DEGREE PROJECT IN VEHICLE ENGINEERING, SECOND CYCLE, 30 CREDITS STOCKHOLM, SWEDEN 2021
Life Cycle Cost of Smart Wayside Object Controller Livscykelkostnad av Smart Wayside Object Controller
FILIPP ZAROV
KTH ROYAL INSTITUTE OF TECHNOLOGY SCHOOL OF ENGINEERING SCIENCES i
Author
Filipp Zarov MSc in Railway Engineering School of Engineering Sciences KTH Royal Institute of Technology
Title
Life Cycle Cost of Smart Wayside Object Controller Livscykelkostnad av Smart Wayside Object Controller
Host Company ALSTOM Transport AB Trafikverket
External Supervisor Fredric Bonnevier, Head of DC performance, ALSTOM
Internal (KTH) Supervisor Zhendong Liu, Researcher, vehicle engineering and solid mechanics, KTH
Examiner Sebastian Stichel, Professor, Department of Engineering Mechanics, KTH
Date August 2021 ii
Sammanfattning
I ett regionalt järnvägssignalsystem är utdelar de enheter som ansvarar för att kontrollera spårutrustning och fungerar de som gränsyta för spårutrustning med ställverksdatorn och tågtrafikledning systemet. Dock, tillhörande kablar (signalkablar ock kraftkablar), samt anläggningsinfrastruktur utgör en stor kapitalinvestering och de är en källa till märkbar kapitalkostnad och driftskostnader, särskilt på landsbygdsområden, där tillgänglighet och anslutning till elnätet och ställverket är problematisk. Dessutom, kablar och signalutrustning utsätts för stöld och sabotage i sådana områden. Detta kan öka den totala livscykelkostnaden ytterligare. Shift2rail forskningsprogram, som genomförs av EU och järnvägsintressenter, försöker att ta itu med problemet och modernisera utdelar konceptet genom projektet “TD2.10 Smart Radio Connected Wayside Object Controller”, där målet är att utveckla en Smart Spårutrustning Utdelar, så kallade SWOC. En SWOC har kapacitet för trådlös kommunikation mellan central ställverket och spårutrustning, samt decentralisering av satällverkslogiken. Dessa innovationer kan minska nödvändig kabeldragning, öka tillgängligheten av diagnostiska data, vilket minskar underhålls- och driftskostnader och kan leda till energibesparing genom att använda lokala kraftkällor. Den viktigaste effekten av SWOC är en betydande minskning av kapitalkostnader, driftskostnader och totala livscykelkostnaden för en installation som använder SWOC istället för typiska utdelningsystemet.
Detta examensarbete fokuserar på att uppskatta LCC för ett SWOC-system och jämföra det med en konventionell utdelingsystem genom att utveckla en LCC-modell som täcker båda fallen, samt att använda denna modell för att undersöka när det är mer lönsamt att implementera en SWOC istället av ett typiskt utdelingsystem. Detta görs genom att använda LCC-analys och kombinera en mängd olika metoder i en parametrisk studie. För att göra detta genomförs en grundlig analys av ett modernt regionalt järnvägssignalsystem, samt grunden för livscykelanalys. Samtidigt beskrivs både ett typiskt utdelingssystem - och SWOC-system samt faktorer som påverkar deras kostnad deskuteras.
Metoden består av LCC-modelleringsdelen samt insamling av metoder och tekniker som används för att beräkna LCC för OC / SWOC-system och för att uppskatta kostnaderna för olika delmodeller och parametrar för processen. För modelleringsprocessen valdes stationen i Björbo, som arbetar under ERTMS-R-systemet, men för analysens skull antas att det typiska bassystemet på plats är en typisk OCS och tillsammans med befintlig planritning och kabelplan är används som grund för analys. Slutligen används den bildade LCC-modellen i en parametrisk studie för att undersöka hur LCC påverkas genom att använda OC eller SWOC samt hur LCC reagerar på förändringar i parametrar såsom antal OC / SWOC, trafiktäthet och lokala kraftinstallationskostnader för Björbo-stationen.
Nyckelord: järnvägssignalsystem, ställverk, hårdvara, Utdelar, SWOC, livscykelkostnad, förnybara energikällor iii
Abstract
In a regional railway signalling system, object controllers are the devices responsible for controlling Track Side Equipment and act as interfaces for TSE with the interlocking computer and the Traffic control system. However, associated cabling (signal and power cabling) and civil works pose a major capital investment and it is a source of significant Capital and Operational expenses, particularly in rural areas, where accessibility and connectivity to power grid and to the interlocking are a problem. Furthermore, cables/signalling equipment are exposed to sabotage and theft in such areas. This can increase the total Life Cycle Cost even further. The Shift2Rail research programme, which was initiated by the European Union and railway stakeholders, tries to address this issue, and revamp the Object Controller concept through the project “TD2.10 Smart radio connected wayside object controller”, where the aim is to develop a Smart Wayside Object Controller (SWOC). A SWOC is capable of wireless communication between central interlocking and TSE as well as decentralization of interlocking logic. These innovations can reduce the cabling required, increase the availability of diagnostic data, thus reducing maintenance and operational costs and can lead to power saving by utilizing local power sources. The most important impact of the SWOC is a significant reduction of CAPEX, OPEX and of total LCC for an installation utilizing SWOCs, instead of typical OCS.
This work focuses on estimating the LCC of a SWOC system and to compare it with a conventional OCS by developing an LCC model that covers both cases, as well as to use this model to examine when it is more profitable to implement a SWOC, instead of an OCS system. This is done by utilizing LCC analysis and combining a variety of methods in a parametric study. To that extend, a thorough analysis of a modern regional railway signalling system, as well as the basis for LCCA are being discussed. At the same time, both OC and SWOC systems are being described and factors affecting their cost discussed.
The methodology is comprised of the LCC modelling part as well as the collection of methods and techniques used to calculate the LCC of OC/SWOC systems and to estimate the costs of different sub-models and parameters of the process. For the modelling process, the station of Björbo was chosen, which operates under ERTMS-R system, but for the sake of the analysis it is assumed that the typical base system in place is an OCS and together with the existing track layout and equipment it is used as the basis of the analysis. Finally, the formed LCC model is being used in a parametric study to examine how the LCC is affected by using OC or SWOC as well as how LCC responds to changes in parameters such as number of OC/SWOC, traffic density and local power installation cost for the Björbo station.
Keywords: railway signalling system, interlocking, hardware, Object Controller, Smart Wayside Object controller, Lifecycle Cost, renewable energy sources iv
Nomenclature and Abbreviations
AC Alternating Current OC Object Controller
ABS Automatic Block System OCS Object Controller System
ATC Automatic Train Control O&S Operations and Support
ATP Automatic Train Protection OPEX Operational Expenses
CAPEX Capital Expenses PCE Parametric Cost Estimation
CTC Centralized Traffic Control PD Power Distribution
CCS Command Control and Safety PSU Power Supply Unit dB Decibel PVC Polyvinyl Chloride
DC Direct Current PV Photovoltaic
DMU Diesel Multiple Unit RBC Radio Block Centre
DTC Direct Traffic Control ROW Right Of Way
EC Element Controller (see OC/OCS) SHS Standalone Hybrid System
EMU Electric Multiple Unit SWOC Smart Wayside Object Controller
EPR Ethylene Propylene Rubber STM Specific Transmission Module
ERA European Union Agency for Railways TCC Traffic Control centre
ERTMS European Rail Traffic Management System TD Technology Demonstration
ERTMS-R European Rail Traffic Management System – TETRA Terrestrial Trunked Radio Regional
ETCS European Train Control System TMS Traffic Management System
EU European Union TOC Total Ownership Cost
FO Fiber Optics TOB Technical Object Building
GSM-R Global System for Mobile Communications – TPSS Traction Power Substation Railway
LCC Life Cycle Cost TRV Trafikverket (Swedish Transport Administration)
LCCA Life Cycle Cost Analysis TSE Track Side Equipment
LED Light Emitting Diodes TT&TO Timetable and Train Orders
LEU Landside Electronic Unit TVM Time Value of Money
LRBG Last Reference Balise Group TWC Track Warrant Control
LSZH Low Smoke Zero Halogen UPS Uninterrupted Power Supply
MBS Manual Block System UHF Ultra-High Frequency Radio
NTC National Train Control XLPE Cross-Linked Polyethylene v
Acknowledgements First and foremost, I would like to thank Fredric Bonnevier, Head of DC performance of Alstom, for guiding me through this task, by providing data crucial for the estimation of SWOC LCC model, by helping to define the scope of such a task as well as providing an in- depth understanding and useful advice, as well as support for the implementation of this project. Second, I would like to thank Mihael Zitnik, system engineer and fellow EMC Expert of Alstom for providing me with data related to OCS and SWOC, for helping me understand the SWOC project from an energy perspective and for providing me with data related to energy consumption of crucial objects, such as cables and OCs. Third, I would like to thank Anders Lindahl, Research engineer at KTH, Transport planning division for his invaluable help, guidance and provision with legislation, regulations and technical documents related to signalling infrastructure in Sweden. Fourth, I want to thank Tyler Dick, lecturer and Principal Railway Research Engineer with the Railway Transportation and Engineering Centre (RailTEC) at the University of Illinois at Urbana-Champaign (UIUC) for his invaluable input, related to railway project development, particularly from the standpoint of providing an insight into consultancy cost estimation as well as proving me with cable duct cost values. Furthermore, I would like to thank Sebastian Stichel, professor at KTH, Department of Engineering Mechanics and examiner for this master thesis for his effort in stimulating this master thesis and its progress. Last but not least, I would like to thank Marija Rubil for her massive phycological support and for standing by my side through the whole process.
Finally, I would like to thank anyone involved directly or indirectly in the process of master thesis writing. vi
Table of Contents
1. Introduction ...... 1 1.1. Background ...... 1 1.2. Problem ...... 2 1.3. Purpose ...... 2 1.4. Goal ...... 2 2.Background and literature study ...... 3 2.1. Classification of railway systems ...... 3 2.2. The core of railway signalling and train control ...... 3 2.2.1 Centralized Traffic Control ...... 5 2.2.2. Interlockings ...... 6 2.2.3 Automatic Train protection (ATP) ...... 21 2.2.4. Track elements and trackside equipment ...... 28 2.2.5. Civil works: Cable ducts and OC/SWOC foundations ...... 37 2.2.6. Railway power supply systems and signalling ...... 38 2.3. The Smart wayside object controller (SWOC) ...... 44 2.4. Fundamentals of LCC analysis ...... 48 2.4.1. LCC of railway signalling project ...... 52 3.Methodology ...... 53 3.1. Case study: Björbo and Västerdalsbanan ...... 54 3.2. Björbo station layouts and TSE within the station ...... 55 3.3. Calculation of distances between signalling objects, OC/SWOC, interlocking and power source ...... 56 3.4. Number and location of object controllers/SWOC ...... 57 3.4.1. K-means algorithm ...... 58 3.5. Inflation ...... 59 3.6. Estimating the LCC model of an OC/SWOC installation – Generic model ...... 60 3.6.1. Estimation of installation design cost (푪풅풆풔풊품풏) ...... 61 3.6.2. Estimation of CAPEX cost ...... 61 3.6.3. Cost of construction and installation (푪푪푰) ...... 69 3.6.4. Cost of Energy Storage and energy supply system ( 푪푬푺풚푺 and 푪푬푺푺) ...... 70 vii
3.6.5. Estimation of OPEX cost ...... 77 4. Results ...... 79 4.1. LCC of SWOC VS OC installation – scenarios (a) VS (b) ...... 80 4.2. The effect of adding more OCs/SWOCs - scenarios (a) to (f) ...... 81 4.3. Main factors affecting the choice of SWOC or OC solution ...... 86 4.3.1. Distance of interlocking from station and the effect of OCs/SWOCs ...... 87 4.3.2. Cost of local power supply and the effect of traffic ...... 88 5. Conclusions and future work ...... 91 5.1. Conclusions ...... 91 5.1.1. Signalling system structure and cost ...... 91 5.1.2. The effect of SWOC concept on the LCC of signaling installations...... 91 5.1.3. The LCC modelling process for signalling installations ...... 92 5.1.4. Profitability of OC vs SWOC installations...... 93 5.2. Future work ...... 95 References ...... 96 Appendix A: Literature review ...... 100 Appendix B: Methodology ...... 103
1 | 1. Introduction
1. Introduction
1.1. Background In a modern regional signalling system, which is based on electronic interlocking, object controllers, which are devices located on the field, are used in case of many objects which are geographically dispersed, either along a line or a station to provide interfaces between TSE and the interlocking computer. This sounds reasonable but comes with several drawbacks:
− To connect Object Controllers (OCs) with the interlocking and with electricity, particularly in cases where OCs are located in remote areas, km of copper cables and Fiber Optics (FO) are necessary to create the necessary architecture. This comes with a hefty Capital Expense (CAPEX), due to the need for extensive material procurement and the need for civil works on the spot. − OPEX that is generated throughout the entire life of the project is also very high, particularly when cable maintenance is considered. − Due to its value, the copper cables are exposed to theft and therefore railway system is faced with interruptions and lost productivity. − The total LCC is very high.
To address these drawbacks, the X2Rail4 project within the Shift2rail, an EU research programme, was initiated by the European Union and railway stakeholders. The Shift2Rail mission is to advance the EU railways, and its activities focus on three top level objectives:
− Reducing the life-cycle cost of railway transport − Increasing railway capacity − Increasing reliability and punctuality
Within Shift2Rail, The IP2 “Advanced Traffic Management & Control Systems” is one the five asset-specific Innovation Programmes (IPs), covering all the different structural (technical) and functional (process) sub-systems related to control, command, and communication of railway systems. IP2 defines 11 Technology Demonstrators and one of them is the project titled “TD 2.10 Smart radio connected wayside object controller”. In this TD, the aim of Shift2rail is to address the problems created in an OC system, by revamping the OC concept into a Smart Wayside Object Controller (SWOC). A SWOC is capable of wireless communication between central interlocking and TSE as well as decentralization of interlocking logic. These innovations can reduce the cabling required, increase the availability of diagnostic data, thus reducing maintenance and operational costs and can lead to power saving by utilizing local power sources. The most important impact of the SWOC is a significant reduction of CAPEX, OPEX and of total LCC for an installation utilizing SWOCs, instead of typical OCS. 1. Introduction | 2
1.2. Problem One of the many tasks that surround the development of SWOC is to estimate its LCC and make the necessary calculations in order to be able to quantify its economic impact on the cost of signalling systems. In general, it is desirable that products such as this can reduce the total LCC, through reduced CAPEX and OPEX.
1.3. Purpose This work is part of the Shift2Rail work and more specifically part of the activities related to the SWOC project. The purpose of this work is to develop a valid LCC model that captures the cost structure of a SWOC and is able to be used in order to estimate the LCC of a SWOC installation. Furthermore, this LCC model must be able to be used in order to estimate in which cases it is preferable to use a SWOC installation instead of a typical OCS, purely one economic terms.
1.4. Goal The goals of this research are to underline the main contributors to LCC in either an OC or a SWOC system, to construct the necessary LCC models but above all to prove that the use of a SWOC system instead of a typical OCS in rural areas can have a significant impact to the total LCC of the installation by minimizing both CAPEX and OPEX.
3 | 2.Background and literature study
2.Background and literature study
2.1. Classification of railway systems According to Pachl [1], railway systems may be classified by different criteria. A common approach is to distinguish between heavy and light rail systems. Heavy rail systems are the standard railways and other railway systems that are based on a similar technology. The standard railways form the nationwide railway system. Due Figure 1: Classification of Railway Systems. Source: [1] to a high degree of standardisation, most railway vehicles may operate in the entire national rail network. However, the access of locomotives to specific lines may be restricted due to axle loads or requirements for specific equipment. There are also dedicated lines for a specific kind of traffic (e.g., high-speed lines) where other kinds of traffic are excluded. Most standard railways offer transportation services to customers on the public transportation market. Heavy rail transit/metro systems implement similar technology, but standards may differ, therefore these systems are kept separate from the standard rail network. In the context of the present work, the focus lies entirely on what applies for heavy rail systems and more specifically on standard railways, particularly from the perspective of train control and signalling systems.
2.2. The core of railway signalling and train control C. Barkan [2] states that “railroads enable high efficiency, which is related to the form of train control”. Furthermore, he suggested that train control systems “must optimize the balance between safety, cost and service quality”. To that extent, it can be argued that cost is one of the most important factors driving the form of train control or of a railway signalling system. In the following sections, an attempt is made to clarify the terminology surrounding the topic and to establish a connection between train control, railway signalling systems and their characteristics, as well as their cost, which will be proved very useful later. He further states that railway transportation has several distinct advantages. However, its characteristics (and to some extent its advantages), mainly the low coefficient of friction and the fixed guideway, affect the infrastructure design and the train control system requirements. It can 2.Background and literature study | 4
be stated that the train control system is implemented through a railway signalling system1 and requires three elements:
1. Movement authority: the permission given by the traffic control centre to a train to occupy or not to occupy a track section. Variety of ways to be accomplished, control may be local or centralized, manually, or automatically monitored and issued. The way movement authority is issues is directly related to the structure of the train control system/signalling system and to some extent to its cost. 2. Communication: means by which the status of specific track sections is monitored, and operating instructions are provided to trains. Includes simple means like verbal or paper or more complicated like radio, cables, or visual signals. Here, the choice of equipment depends on many parameters but mainly on cost, efficiency, and availability. 3. Speed control: necessary for traffic control requirements and civil infrastructure. Includes systems that either inform operator about the speed or automatically enforce it. Such systems are known in the broad context as ATP systems and in pan-European/ ERTMS signalling system context as ETCS system with its different levels of application. This is where a big part of disparity between systems can be located. For example, while is USA coded track circuits are used to achieve cab signalling and convey information/provide speed control, in Europe and particularly in ETCS context, balises or radio are used instead. This of course affects the capabilities and the cost of the system: the more sophisticated the speed control is, the more expensive the application.
Every train control system has its own Method of operation(s), which according to Barkan and Roma [3] is a set of protocols and technologies that characterize how train movements are controlled. Some methods provide or not movement authority and provide or not traffic control. Methods of operation and their interrelations are presented on Table 1, while the provision of movement authority and/or traffic control by different methods of operation on Figure 2.
The attainment of the above require both hardware and software. Hardware could be considered as anything with physical hypostasis, such as hard drives, displays, balises or chips. In contrast, software is anything without physical hypostasis, such as the interlocking logical rules, operating protocols etc.
Fundamentally every railroad has its own hierarchy of documents or operating instructions that apply to and regulate either train operations and movements or crew conduct across a railroad. These documents form a hierarchy, from instructions of more general nature to instructions of a more specific one [3]. Furthermore, they constitute the basis of the train control system in any railroad.
1 1 It must be noted that train control and signalling are not synonymous as the former conveys movement authority, while the latter traffic control, a.k.a. conveys the proper speed to the train driver. However, in some methods of operation, signal indications do convey authority. This is the case with centralized traffic control systems (CTC). 5 | 2.Background and literature study
Table 1: Methods of operation, Movement authority and Traffic Control. Source: [3]
Figure 2: Coexistence of movement authority and traffic control -Methods of Operation. Source: [3]
Today’s train control management allows for continuous train location monitoring, as well as communication between train engineer and dispatcher [4]. However, that was not always the case. Rather train control systems evolved over time by incorporating technological inventions which make the control of train operations safer, more effective and cost efficient, while shortening travel times and increasing capacity. In the context of this master thesis, the focus is mostly on the European railway signalling practice and more specifically on practices followed by Sweden’s Trafikverket and on ERTMS system. To that extent only CTC and centralized ABS/signal-controlled lines, as methods of operation widely implemented on EU and Sweden level, are considered, and discussed below. Furthermore, this master thesis focuses on the hardware structure of the rail traffic management systems2 and especially at the level between interlocking and TSE. ATC
2.2.1 Centralized Traffic Control According to Pachl [1], in Centralised Traffic Control Figure 3: Functional structure of the rail (CTC), all points and signals inside the controlled area are traffic management system. Source: [17], directly controlled by the dispatcher. All train movements own editing are governed by signal indication. The local interlockings are remote-controlled without local staff. In CTC territory, all sections must be equipped with track clear detection. CTC technology has a long tradition on railways that operate long lines
2 The terms train control and management system, rail traffic management system and signalling system with be used interchangeably. 2.Background and literature study | 6
in territories with a very low population density and long distances between stations. Typical examples are lines in North America and in Russia. With the introduction of CTC, some of
Figure 4: Centralized traffic control. Source: [1] the essential differences between railways that follow North American, British, or German operating procedures partly disappeared. CTC brought two operating philosophies together. For European railways, CTC brought centralized control, for North American railways it brought signal-controlled operation. This kind of traffic control is the only one considered for this master thesis.
2.2.2. Interlockings The term interlocking can be seen from many angles. First, it can be used as a) an “interlocking area”, where points and signals are interconnected in a way that each movement follows the other in a proper and safe sequence. Second, b) the principles to achieve a safe interconnection between points and signals are also generally called ‘interlocking’ [1]. Third c), interlocking can be seen as a physical system, which ties all the elements of a train control/signalling system together. From an operational perspective, it is referred mostly to railway intersections or station areas and according to Pachl [1], interlocking is described by a). Figure 5: Control Tower of a Large For example, a signal can only be cleared if all points Interlocking Station (Frankfurt, Germany). Source: [1] are locked in the proper position and conflicting routes are locked out. Signals that govern interlocked routes are called interlocking signals. The points and signals are controlled either by a local interlocking station or from a remote- control centre. Local interlocking stations are called interlocking towers in North America, and signal boxes or signal cabins on most other railways. Modern interlockings are usually remote controlled by a control centre. 7 | 2.Background and literature study
Interlocking systems have evolved as well over the time, from interlocking beds and mechanical installations at stations (used rarely today) to relay and computer based interlocking systems. Electronic interlockings and their physical constitution (system architecture and interconnections) will be discussed extensively and are the focus of this master thesis.
2.2.2.1. Electronic Interlockings - history The first electronic interlocking systems were installed in the 1980s and have since been further developed. Various systems in different versions are offered by different manufacturers, each being applied in one or more countries. In many applications, components of different manufacturers and types are combined. For example, an operation control system of one manufacturer is used to control a relay or an electronic interlocking system of another manufacturer. Alternatively, field elements of one manufacturer are combined with interlocking controllers of other manufacturers. The new trend is increased localisation of element control, in connection with centralisation and flexibility in the logical interlocking functions [5].
2.2.2.2. Electronic Interlockings – system safety In terms of system safety, the functions are mainly defined in programmed software. Microelectronic technology, in comparison with mechanical and relay technology, has several unfavourable safety characteristics, which mainly stem from modus operandi, as well as several inherent characteristics. To overcome these deficits, hardware and software redundancy and diversity are used to a different extent. Hardware redundancy means that the same functions are processed in different hardware channels and the results compared. This mainly helps to exclude spontaneous errors of the electronic system. Hardware redundancy is used in almost all electronic interlocking systems. Diversity helps to exclude systematic errors in design and can take different forms, such as diverse hardware, software, or operation systems [5].
2.2.2.3. Electronic interlockings -hardware structure In a typical electronic interlocking, 3 basic levels can be identified [5]:
− The operation control level is often provided by external remote-control systems or by workplaces far away from the interlocking area. Consequently, the operation control level is usually not considered as an integral part of the electronic interlocking system, but as a separate system. However, interfaces between the operation control systems and the interlocking itself must be defined. It can be argued that this level is represented by the TMS. − The interlocking level is considered to be one of the integral parts of the electronic interlocking system. An interlocking (as a physical object) is represented as a big computation unit (Figure 6). An interlocking includes the safety related functions to interlock signals, routes, movable track elements, block applications etc. with each other [5]. Furthermore, it receives information from and provides them to TMS, establishes, 2.Background and literature study | 8
safeguards, locks, or releases routes, and supervises the status of TSE (e.g., signal lamp filament) [6] − The element control level is also an integral part of the electronic interlocking system. includes functions of commanding, power, and information transmission to and from the field elements, such as signals, movable track elements, track sections, level crossings etc. Integral parts of this level are the Element Controllers/Object Controllers3 (Figure 27) and the different TSE. More specifically, element controllers are modules designed for the control of one or several peripheral elements. Element controllers can be located in the interlocking building, as well as locally near the element(s) they control, in other words the architecture Figure 6: Interlocking EBI Lock of interlocking-element control part can be either centralized 950 (Manufacturer: Bombardier). Source: [6] or decentralized. Types differ between interlocking products, but in general the main types of element controllers are: ➢ element controllers for signals and/or balises of train protection systems ➢ element controllers for points (also usable for derailers etc.) ➢ element controllers for track circuits or axle counters ➢ digital I/O elements for relay interfaces (e. g. block interfaces, level crossings or key locks)
Furthermore, it should be noted that ATP systems (such as European ETCS or Swedish ATC- 2) can interface with either the element control level (in systems that are sending or receiving information from TSE, like ECTS LV1) or the interlocking level (systems that use continuous transmission, such as ETCS LV2). The structure of a typical electronic interlocking is presented in Figure 7.
2.2.2.4. Electronic interlockings -geographic distribution In terms of geographic distribution, most interlockings include central and local interlocking stations. The central interlockings include either the whole interlocking level or parts of it, while the local stations include the element control and sometimes the remaining parts of the interlocking level [5].
In terms of size of the area an interlocking controls (area of responsibility), that varies very much between different interlocking systems. In many cases, a central station is responsible for an area which usually covers one station, whereas one local station is responsible for few (around 1–5) sets of points and/or signals. In other systems with very large interlocking areas, one central interlocking station can control a line section of up to around 100 km, with one local interlocking station being responsible for each (small) station (Figure 8) [5].
3 Object controller is the term will be used throughout the master thesis. 9 | 2.Background and literature study
Figure 7: Functional structure of electronic interlocking. Source: [5]
The power supply is still a conventional central one. Hereby, the control of field elements is distributed in wayside controllers in proximity to the elements to be controlled, whereas the central functions of interlocking logic etc. can be very centrally located. In extreme cases, there can even be one control centre for the whole country. The spatial separation of interlocking and field elements is enabled by Ethernet, which enables practically unlimited control distances. Also, backup control centres are planned, e. g. a second control centre elsewhere in the country. In the future, even solutions in the Cloud could become possible [5].
It must be noted that one characteristic of the network communication structure is that the element controllers (ECs) are connected through rings of command control and safety (CCS) equipment (Ethernet or fiber optics; “FO”) to the redundant fibre-optic network. The switching commands are sent by the electronic interlocking central unit to the element controllers. Central units also have redundant connections to the fibre-optic backbone. The element controllers switch the field elements and send status reports to the electronic interlocking central unit [5] (see Figure 9). 2.Background and literature study | 10
Figure 8: Geographical assignment of electronic interlocking. Source: [5] Similar logic can be applied for the object controllers. Depending on the geographic configuration of interlocking logic hardware, the architecture of the interlocking system (centralized or decentralized), and the distribution of TSE along the station, the architecture of OC system can also vary: there is the possibility to have fully centralized configurations (where TSE is directly connected to the interlocking unit), partially decentralized configurations (several OC’s plugged into the same interlocking unit, controlling a cluster of TSE each) and a totally decentralized configuration (where all OC’s are plugged into the same interlocking unit and one OC corresponds to one TSE).
The geographical distribution of TSE, the distance from the interlocking unit, as well as the Figure 9: Energy bus power supply in network interlocking. Source [5] cost play a very important role in determining the exact configuration as well as the number of OC’s used in an application (see Figure 10). 11 | 2.Background and literature study
Figure 10: Centralized VS decentralized structure of Object controlling system. Source: [25], own editing
2.2.2.5. Communications and connections between interlocking elements According to [5], transmission between the geographically separated components or field elements of an interlocking system is solved by electrical cables, optical cables or radio information, usually based on addressed data telegrams. Safety is provided by redundancy of the data telegrams. For availability, redundancy of the physical data lines on different paths is often also provided. The focus here lies with the connections between interlockings and Object controllers and to a lesser degree between object controllers and TSE.
As mentioned before (Figure 10), in general, there are 2 options regarding connection between TSE and OC: centralized and decentralized connectivity structures. In centralized installations, it requires at least two wires for each signal lamp, and the country specific number of wires for each point machine to be laid between the interlocking and the field element. The control length is around 6.5 km with standard cables and few kilometres more with special cables. In contrast, for decentralized options, control and supervision cable only needs to be laid on the length between the local field element controller and the related field element(s), whereas information between the local controllers and the interlocking can be transmitted by data communication (by using mostly fibre optics or radio communications). This reduces expenses for copper cables but needs additional efforts for locally distributed logic. The control length between the interlocking and the field element is practically unlimited. Finally, as said before, the preference for the one or the other solution depends on economic considerations, the track layout, the historical development of signalling in the 2.Background and literature study | 12
country, the local availability of power supply, environmental conditions etc. The power supply is of particular importance and will be analyzed further.
Figure 11: Variants of cabling of field elements. Source: [5]
2.2.2.5. Cables and Fiber Optics in signalling systems When constructing a physical interlocking system, two main options are available for connecting interlockings, OC’s and TSE physically. The first are cables (usually made of copper) which can be used both as signal cables (between interlocking and OCs, as well as between OCs and TSE to transfer electrical signals) and as power cables to transfer energy between power source and interlockings/OC’s/TSE. The second one is to use optic fibres, which are used as signal cables, usually between interlocking units and OCs. In the following, their properties are being discussed.
The most important topic related to cables is their resistance (for cables being used in DC applications) or their impedance (for cables being used in AC applications). According to [5], there are four impedance components inside the cable (Figure 12):
1. Longitudinal ohmic resistance: This is determined by the material, the sectional area and the length of the cable and should be small to achieve a good control length of the cable and to reduce energy consumption. According to [7], for a resistor, the relationship between voltage 푉 and current 퐼 for a resistor is given by Ohm’s law
푉 = 퐼푅 (1)
this law states that the voltage drop across the resistor is directly proportional to the current through it. The MKSA unit for resistance is the ohm, denoted by Ω, which is 13 | 2.Background and literature study
Figure 12: Quadrupole of a cable. Source: [5]
defined as a volt per ampere. In a case of a conductor of a uniform cross section, the following simple formula is valid
퐿 푅 = (2) 휎퐴 where 퐿 is the length of the conductor, 퐴 is the cross section and 휎 is a physical constant called conductivity, which depends on the material composition and temperature. Alternatively, according to [8] resistance can be written as
휌퐿 푅 = (3) 퐴 where 휌 is the resistivity of the resistor material. The relationship between conductivity and resistivity is inversely proportional
1 휌 = (4) 휎
Figure 13: A uniform cross-sectional area conductor. Source: [7] 2. Longitudinal inductance: This is determined by the spacing and angle between parallel cable cores, the insulation material and the length of the cable and should be small to achieve a good control length of the cable. According to [7], an inductor is a two-terminal element which stores energy in magnetic fields and is characterized by inductance (퐿). It is the property which opposes any change in the existing current [8]. It can be shown that inductance is determined by the square of the number of turns, the geometric dimensions of the inductor, and the magnetic permeability of the core. In effect, inductance is a coefficient of proportionality between flux linkage and current 2.Background and literature study | 14
Ψ = 퐿퐼 (5)
the inductance in a cable is responsible for the creation of inductive reactance (푋퐿), which is the opposition to the flow of alternating or pulsating current by the inductance of a circuit [8]. It can be expressed as:
푋퐿 = 2휋푓퐿 = 휔퐿 (6)
where 푓 is the frequency in HZ, 퐿 is the inductance and 휔 is the angular speed.
3. Leak resistance (ohmic) of the cable: This is determined by the insulation material and by the length of the cable and should be high. 4. Cross capacity between cable cores: This is determined by the spacing between cable cores, the permittivity of the insulation material, the distance and angle between the wires in the cable and the length of the cable and should be low to achieve a good control length of the cable. In general, according to [7], a capacitor is a two-terminal element which stores energy in the electric field and is characterized by capacitance, denoted 퐶. A capacitor is formed by two conductors separated by some distance. Sometimes a dielectric material may be placed between the conductors to provide a means of separation and to enhance the capacitance. Just like inductance, capacitance is usually a difficult quantity to calculate, and this is done by using electromagnetic field theory. However, there are some widely used expressions for a few standard configurations. One of them is the following
휖퐴 퐶 = (7) 푑
where 휖 = 휖푟휖0 (휖푟 is the relative dielectric constant, while 휖0 is the permittivity of vacuum), 퐴 is the plate area and 푑 is the distance between them. According to [7], in
an AC circuit, the capacitive reactance, or the impedance of the capacitor 푋퐶 is 1 1 푋 = = (8) 퐶 휔퐶 2휋푓퐶
where 푓is frequency and 퐶 is capacitance.
In practice, for DC supply, only ohmic resistance can be considered for the cables. However, this is not the case for AC supply, where the cable resistance is expressed as impedance. Impedance can be written as
푍 = 푅 + 푗푋 (9) 15 | 2.Background and literature study
where 푅 is the resistance while 푋 is the reactance. It must be noted that impedance is a complex number, since 푅 and 푋 (푋퐿 and 푋퐶) are in different phase. In turn, reactance can be written as
푋 = 푋퐿 − 푋퐶 (10)
For resistance, inductance, and capacitance in series, impedance can be written as
2 2 푍 = √푅 + (푋퐿 − 푋퐶) (11)
Furthermore, according to [5], there is a possibility of electromagnetic induction by parallel cables with higher voltages and currents, e. g. overhead wires in electric traction areas. These can be avoided by keeping a certain distance to such cables and by only crossing them at right angles. The above factors, the ohmic resistance, the capacitive coupling of wires in the same cable and the voltage induced by overhead wires in electric traction areas lead to a limitation of cable length. The traditional maximum length of a cable for control of signals, points, external digital I/Os etc. is therefore about 6.5 km, with special cables this can be increased up to around 10 km.
In practice, only the longitudinal ohmic resistance is used when impedance is calculated, however one must consider whether the system or part of the system is DC, 1-phase AC or 3-phase AC (they imply different power loss and different types of cables). From physics, it is known that a power source has a specific power (maximum or rated), which is given by
푃푆표푢푟푐푒 = 푉퐼 (12) where:
푃푆표푢푟푐푒 Source Power
푉 Voltage
퐼 Current
At the same time, a cable has a specific resistance, which when combined with current 퐼, according to Ohm’s law, leads to voltage drop, as well as to power loss, which can be quantified as
2 푃퐶푎푏푙푒 = 퐼 푅 (13) where:
푃퐶푎푏푙푒 Power Losses from cable
푅 Cable resistance
퐼 Current 2.Background and literature study | 16
To losses calculations, return losses must also be considered4. To minimize the power loss of a cable there are 2 alternatives: [7]
− Reduce the wire resistance, which requires an increase in the cross-sectional area. This is a rather expensive alternative. − Make the current as small as possible. Since the power transmitted through cables is fixed, the voltage v must be high to transmit the same power with the desired small current. The latter approach is the basic idea behind high-voltage power transmission lines.
Another important parameter related to copper cables is their current rating or their current- carrying capacity5. It can be calculated for a cable by utilizing the electromagnetic theory, which is way out of the scope of this thesis. Instead, different cable diameters are related to different current ratings, which are presented on Table 10 (see Appendix B: Methodology).
For cables used in railways, insulation of the wires against each other and against the environment is important, for avoidance of interference, as well as for mechanical strength. Sheaths are used to reduce inductivities induced from sources outside the cable, whereas armour provides mechanical protection [5].
The layers from outside to inside are typically [5]:
− Outer sheath − First armour − Second armour Figure 14: Layers of a signal cable (photos: − Cable sheath Martin Bimmermann). Source: [5] − Cable shield from aluminum, connected by wires − Copper wires, each of them isolated, twisted (to minimize capacities).
In general, cables can be either copper or aluminum. Their difference is while copper has less resistivity, aluminum costs approximately 1/2 to 1/3 of the copper price. Therefore, aluminum is usually used, especially during the last decade as a main material for power network cables (high to low voltages). Furthermore, in comparison to Figure 15: Comparative diameters of 600/1000V, 4-core PILS/STA and CNE cable of Consac type of equal rating. copper, aluminum is more brittle, which Stranded and solid type cables. Source: [62] partially explains its use on higher cable cross sections. Finally in terms of performance, copper cables have a lower voltage drop than
4 Multiply resistance by 2. 5 As a general rule of thumb, the current determines the thickness of the wire, while the voltage determines the thickness (and/or material) of the insulation. 17 | 2.Background and literature study
aluminum cables, when cables of similar cross section are examined, however for higher voltages the difference is smaller. Copper conductors are favored where cable diameter, flexibility, connectability of the conductor, and cost of components beyond the conductor are major factors. Aluminum conductors offer cost savings where cable diameter is less of a factor and a weight advantage, which is important for cables suspended in air [9].
Different cable cross-sections apply. Their size Figure 16: Stranded 1.5 mm copper cable. depends on the power requirements, the balance Source: [67] between cost and power losses/voltage drops as well as the acceptable limits for the voltage drop. Cables with small diameters are used for shorter distances, while cables with bigger cross sections are used for longer distances.
Another difference between different cables is solid vs stranded cables. In solid cables, the core is made of one rolled piece (s) of metal, while in stranded cables are made of several strands to form the cable. In general, solid cables are better electrical conductors and provide superior, stable electrical characteristics over a wider range of frequencies. They are also considered more rugged and less likely affected by vibration or susceptible to corrosion since they have less surface area than stranded conductors. Flexibility is another parameter. Stranded cables are much more flexible and can withstand more bending compared to rigid solid conductors that can break if flexed too many times. However, when it comes to terminating stranded cable, the individual strands of the conductors can break or become loose over time [10].
Finally, another important difference between different cables is the number of cores: they can be either single – core or multi-core cables (multi-conductor cables). With respect to power cables, the most common have three or four insulated power conductors but more are Figure 17: Three conductor round cable. possible for special purpose cables. A simple case might (From Amerceable, January 2011, Internet Catalog, with permission. Accessed have three insulated conductors and an overall jacket. A December 2010.). Source: [9] design common in international low voltage cables is shown on Figure 18. The underlying insulation may be PVC, XLPE, or EPR overlaid with a PVC jacket. Concern for the safety and health concerns connected with smoke and halogens previously discussed result in increased use of LSZH insulation and jacketing materials internationally. An interesting feature of this design is the use of sector-shaped conductors (120° for 3/C cables and 90° for 4/C cables). Round conductors are also available. [9] 2.Background and literature study | 18
Multi-core cables are useful in 1 or 3-phase delivery systems, when having a cable for all phases plus the neutral (return) is more convenient from technical and economic perspective. The following cables can be used to supply a single-phase installation [11]:
− Two conductors: blue (neutral) and brown (one phase).
− Three conductors: blue (neutral), brown (one Figure 18: 3/C Low voltage cable with sector- phase) and green-yellow (earthing). An example shaped conductors. (From General Cable, January 2011, Internet Catalog, with permission. of tripolar would be an armored cable. Accessed December 2010.). Source: [9] To supply 3-phase installation, the following cables are required [11]:
− Three conductors: Grey, brown and black (all three phases) − Four conductors: Grey, brown and black (the three phases) and blue (neutral). Figure 19: 600/1000V, single-core XLPE − Four conductors: Grey, brown and black (all insulated cable with stranded conductor, taped three phases) and green-yellow (earthing). bedding. Source: [62] − Five conductors: Grey, brown and black (the three phases), green-yellow (earthing) and blue (neutral).
Finally, the typical cabling layout for a larger interlocking area is shown in Figure 21. For Figure 20: 600/1000V, 4-core unarmoured cable economic efficiency, thick cables with many wires with solid aluminium conductors. Source: [62] are used in proximity to the interlocking controller. The cables branch up into smaller cables towards the ends of the cable lines. Cable distribution cabinets form the intermediate nodes of the cabling equipment.
Figure 21: Typical cabling layout (graphic: Martin Bimmermann). Source: [5]
The other type of cables used as signal cables are optic fibers. In principle, according to [12], fiber optics constitute a part of what is called the fiber – optic link. In general, a link is a transmission pathway between two points using a generic cable. The pathway includes a 19 | 2.Background and literature study
means to couple the signal to the cable and a way to receive it at the other end in a useful way. A fiber-optic link is like any other link, except that it uses optical fiber instead of wire, where an electrical signal is converted to light, moves over a distance through optic fibers and then is reconstructed as an electrical signal from the light (Figure 22).
Optical fibers carry light energy from the transmitter to the receiver. Their structure is composed of a core between 8 and 62.5 microns in diameter, a cladding that surrounds the core and is typically 125 Figure 22: The fibre-optic link. Source: [12] microns in diameter, as well as the optical fiber’s coating protects the cladding from abrasion. The thickness of the coating is typically half the diameter of the cladding, which increases the overall size of the optical fiber to 250 microns, much smaller than a typical cable. [12]. Most of the fibers are made from glass, i.e., silica. For short-distance (shorter than 1 km) and low-bit-rate (∼ Mb/s) transmission systems, plastic fibers can be used. They are inexpensive, flexible, and easy to install and connect. However, they do not transmit light efficiently because of high absorption. For long-distance and high-bit- rate systems, glass fibers are typically used [13]. In general, the optic fiber cable can have Figure 23: Fibre optic cable layers. Source: more layers and its design is related to the https://www.ofsoptics.com/optical-fiber-coatings/ intended application.
The principle of operation of fiber optics is the internal reflection of light rays, which is the result of the design of both the core and the cladding surrounding it. The core of the optic fiber has a high refractive index 푛0 and is surrounded by a cladding with a lower refractive index 푛1. This index difference requires that light from inside the fiber which is incident at an angle greater than the critical angle (14) be totally internally reflected at the interface of core and cladding [13] [14], so as long as the reflection angle of light ray is bigger than the critical angle, it will keep on reflecting internally till the output end.
−1 푛1 휃푐 = sin ( ) (14) 푛0
It must be noted that the cladding supports the waveguide structure while also, when sufficiently thick, substantially reducing the radiation loss into the surrounding air. In essence, the light energy travels in both the core and the cladding allowing the associated fields to decay to a negligible value at the cladding–air interface [15]. The basic structure of 2.Background and literature study | 20
an optic fiber as well as the mechanism of light propagation inside a fiber optic is presented on Figure 25.
Just like typical copper/electrical cables, fiber optics also do suffer from energy loss over distances. As light travels away from its source through the link, it loses energy. Energy loss can be caused by several factors, such as the absorption or scattering of light by impurities in the fiber, or by light passing through the core and cladding and being absorbed in the coating [12]. Figure 24: Comparison of copper cable (top) and fibre cable (bottom). One of the more common terms used when discussing the Source: [12] quality of a signal in fiber optics is the decibel (dB). The decibel can be used to express power gain or power loss relative to a known value. In fiber optics, the decibel is mostly used to describe optical power, which is also known as signal
Figure 25: (a) Generic optical fibre design, (b) path of a ray propagating at the geometric angle for total internal reflection. Source: [14] power. Modern optical fiber has very low signal power loss and many fiber-optic links do not require the signal to be amplified. To calculate the decibel value of a gain or loss in optical power, the following equation can be used:
푑퐵 = 10 log10(푃표푢푡 + 푃푖푛) (15)
Finally, a very interesting question, especially in railway signalling is whether copper cables of fiber optics are better for transmitting information. A summary is presented on Table 2 below [16] [15]. It can be said that due to the nature of signalling system equipment, copper cables are more widely used. Nonetheless, fiber optics are used as signal cables to allow communication between OC/local interlockings with central interlocking computers. 21 | 2.Background and literature study
Table 2: Differences between Copper cable and fibre optics. Source: [16]
2.2.3 Automatic Train protection (ATP) According to [1], ATP systems transmit information on movement authorities and speed limits from the line to the train to cause automatic braking if the train ignores the valid limits. In a territory with lineside signals, an ATP system works in addition to the lineside signals and with the main purpose of preventing trains from violating signals. In a territory with cab signalling, the ATP system provides the information for the cab signalling. However, having cab signals does not necessarily mean to have ATP. In terms of data transmission between track and train, there is a general distinction between intermittent ATP’s and continuous ATP’s.
For this master thesis, ATP systems are not the focus. However, they are of importance, as every ATP utilizes different trackside equipment to achieve communication and to that extent speed control. The focus of this master thesis lies on ERTMS, and more specifically on ECTS Level 2 and ERTMS-R systems.
2.3.3.1. Train control and command systems (ATC) in Europe In Figure 3, the basic structure of a signalling system was presented. In railway signalling systems, the train control-command or ATC system is an overlay system which extends from the interlocking, all the way down to the rolling stock. According to Winter [17], these 2.Background and literature study | 22
systems are necessary for supporting the driver in the observation of lineside signals or replacing the latter completely by in cab signalling. Furthermore, in physical terms, an ATC/train control – command system is the sum of technical solutions and train control- command devices that allow the trains to be linked to the railway infrastructure and the ATC to be able to perform its duties.
Across Europe, different countries implement different ATC systems with different capabilities and therefore different types and combination of equipment and as no surprise this is the area that has received the most attention on a European level in terms of standardization efforts, since this disparity creates interoperability issues for trains that are travelling through more than one country. Similar challenges are being faced by interlocking, as well as the traffic control levels, but to a lesser degree regarding standardization.
To overcome this disparity on a European level, EU prompted the creation of a European rail traffic management system, or a common European signalling system known as ERTMS. In ERTMS, focus is given on the traffic management layer/operational level (Europtirails), the hardware of signalling system (interlocking, Object control and TSE/INESS), the train control – command system (ETCS) and on railway communication (GSM-R). Therefore, ETCS is a subproject of ERTMS [18]. One important aspect of ETCS is that it gives the infrastructure manager the opportunity to granularly control investments on the trackside by the definition of application levels. This affects the necessity to provide lineside signals, GSM-R based data-communication and the update of interlocking systems not economically compatible with ETCS. [19].
Finally, regarding the equipment of the lines and trains, ETCS specifies three application levels: 1, 2 and 3. Beside that there are two levels for situations, where ETCS is not available (0 and NTC) and three types of equipment of lines developed after the finalisation of the basic structure of the specification that might be represented as an independent level, but will be shown to the driver as one of levels 1 to 3 (Limited Supervision, ERTMS regional and Level 2/3 Hybrid) [19]. Focus will be given on ETCS LV 2, as well as to ERTMS regional. For more details regarding technical aspects of ETCS system, see [20].
2.3.3.2. ETCS Level 2 In ETCS level 2, Information between track and train is continuously and bi-directionally transmitted by Euroradio, a radio standard for data communication based on GSM-R. The central trackside unit is the Radio Block Centre (RBC). It is responsible for the control of a longer section of a line. It stores the track topology including the permitted speed and gradient of track sections and obtains dynamic data like signal aspects and point positions from the interlocking systems in the area. As in Level 1, the interlocking systems are responsible for track clear detection and the setting of routes but have to be replaced when the connection to the RBC is economically not reasonable (e.g., mechanical, or older types of interlocking). In contrast to Level 1, the trains are individually known in the RBC. The RBC sends an updated Movement Authority to the RBC whenever available [19]. In normal level 2 operation, line- 23 | 2.Background and literature study
side signals are no longer necessary [20]. Trains send position reports in short time (e.g., every 6 seconds), after passing balises and upon request by RBC. Balises are mainly needed for positioning the train, the error of the odometry rises with increased distance from the last reference balise group (LRBG) up to 5 %. On open lines with long block sections, the balises are normally installed every 1 to 2 km. Except in special situations like the supervision of an autonomous level crossing, only fixed data balises are used. Level 2 is in operation and is being introduced continuously on several high speed and conventional lines [19]. The crucial differences between level 2 and levels 1 and 3 are presented on Figure 26 and on Table 6 (see Appendix A: Literature review). Furthermore, a very important note is that as ETCS level is being upgraded, the trackside equipment required for the ATC system to operate decreases in number and the role of wireless communication (GSM-R and RBC) becomes more and more important. This development reduces the costs incurred upon installation and operation of a signalling system. On the basis of the concept of cost reduction, the ERTMS-Regional (ERTMS-R) was developed.
2.3.3.3. ERTMS-Regional According to Frøsig [21] more than 25 % of the European rail network consists of regional low-density lines which are still nationally regulated. As their signalling and communication installations often approach obsolescence, it will be necessary to devise economical replacement strategies to maintain the viability of the traffic and to take advantage of advanced technological solutions. For operational reasons, intra-operability with the main line conventional network is also often required. As ERTMS will become the standard on the high-speed and conventional main lines, it makes sense to take advantage of the existing on- board investment on the rolling stock fleet in the planning of new signalling and telecommunications applications on the regional networks. With this aim, UIC has specified, in close cooperation with the Swedish Infrastructure Manager Banverket (now Trafikverket), a low-cost track side concept for regional lines based on the ERTMS system, the so-called ERTMS Regional (ERTMS-R). The costs for the signalling infrastructure can be reduced to 2.Background and literature study | 24
Data flow in ETCS Level 1 (full supervision)
Data flow in ETCS Level 2
Data flow in ETCS Level 3
Figure 26: Data flow in different ETCS levels. Source: [19] about half the price of comparable conventional signalling equipment thanks to the following cost saving factors:
− Staff reduction in stations − Fall-back by Rules and Regulations − No line-side signals − Safety approach by considering a − No traditional interlocking tolerable hazard rate. − Minimising cables by controlling − Minimised track-side equipment will elements via radio. minimise maintenance. − Track circuits and axle counters only for special locations
Sommer et. al. [19] give more details about ERTMS-R configuration. According to them, while ETCS Level 3 was to increase capacity by shortening headways on lines with very high 27 | 2.Background and literature study
traffic levels. ERTMS-R focusses on the minimisation of infrastructure costs and is designed for application in rural areas or on secondary lines with low traffic. The on-board part is identical to the installation used in Level 2, enabling easy movements of trains to main lines with standard ETCS. However, the trackside equipment uses a different layout. Central unit in ERTMS-R is the Traffic Control Centre (TCC), combining functions of the interlocking system (1), Radio Block Centre (RBC) (2) and Traffic Management System, thus safety relevant and non-safety relevant functions are handled by one operator and centralized in one unit, recovering the idea of ERTMS as a system for both, technical and operational functions.
Another important characteristic of the system is that trackside elements are connected to object controllers (OC) (Figure 27), which can be linked to the TCC either by cable or by GSM-R. The concept of wireless communication between traffic control centre/interlocking and TSE and to that extend the reduction of infrastructure cost is central here. SWOC is the embodiment of this idea and will be discussed extensively.
Furthermore, according to Pachl [1], train spacing in ERTMS-R is based on ETCS level 3 without trackside track clear detection technology following the virtual Figure 27: Object Controller on the block principle. Since all passenger trains on regional ERTMS-R pilot line. Source: [21] lines are DMUs or EMUs, which cannot lose any vehicles, checking train completeness is not an issue. For the few freight trains, train completeness is checked by train crews at station stops. He also adds that in ERTMS-R the train control functions of ETCS are combined with the interlocking functionality into a common system. By doing this, the system does not only meet the requirements of ETCS but also of other ERTMS layers. That is, why it is called ERTMS Regional. Finally, according to Sommer et. al. [19], until 2019, there was only one application of ERTMS Regional on the Västerdalsbanan in Sweden and tests on three lines in Italy. The basic schematic of this system is depicted on Figure 28.
Figure 28: Data flow in ERTMS Regional. Source: [19] 2.Background and literature study | 28
2.2.4. Track elements and trackside equipment
2.2.4.1. Tracks In railway operations, according to [1], a track is often also referred to as a line. A route consisting of just one track is called a single line, while a route with double track operation, i.e., two parallel tracks and a specified direction for normal moves on both tracks is called a double line. For operational purposes, tracks are divided into two main classes:
− Tracks that may be used for regular train movements. − Tracks that must only be used for shunting movements.
The tracks used for regular train movements are called main tracks or running lines. The lines between stations and their continuation through stations and interlocking areas belong into
Figure 29: Classification of tracks. Source: [1] this category. It also includes tracks for passing and overtaking trains which are called loops on most railways. In a signalled territory, tracks used for train movements are equipped with signalling appliances for the safe passage of trains. Along the line a train passes through, turnouts are usually interlocked with signals that provide the movement authority. Sidings are all tracks that must only be used for shunting movements. Turnouts6 of sidings are often not interlocked.
2.2.4.2. Turnouts, crossings, derailing devices and point machines According to Pachl [1], a turnout is an assembly of rails, movable points, and a frog, which effect the tangential branching of tracks and allows trains or vehicles to run over one track or another. The points may be operated manually or by a point machine, which electric motor drives or electrically controlled pneumatic Figure 30: Components of a turnout. Source: [1]
6 Technically only the switch part of a turnout is interlocked (part(s) connected with a point machine). That could also apply for a crossing/frog if a turnout implements movable frogs. 29 | 2.Background and literature study
Figure 31: Crossings. Source: [1] cylinder drives. In case of a small angle of divergence, a movable frog operated by an additional point machine could be provided. On the other hand, a crossing is an assembly of rails that effects two tracks to cross at grade. The inner part of a crossing is called a ‘diamond’. Crossings with a large angle of intersection are designed rigidly. In case of a small angle of intersection, fixed diamond frogs are replaced by movable points. Small angle crossings may be equipped with additional points providing a slip connection to permit movements from one track to another.
Derailing devices are trackside devices that are used to protect train movements against unattended movement of vehicles on converging tracks. An unsafe movement will be derailed before it could join the protected route. In the protecting position, a derailing piece is raised over one rail. Like points, derailing devices can Figure 32: Block type Derailing Device operated by be hand or power operated [1]. a Point Machine (Swiss Railways). Source: [1]
Today, modern signalling systems employ non-manual point machines in order to motorize and provide motion to movable parts of the track infrastructure, like switch blades/points, frogs and derailing devices. Point machines can be described as the interface between track and the signalling sytem. In short, according to [22], point machines provide three main functions related to moving points: switching points (1), locking the points (2) and supervision of points (3). A range of switching technologies are implemented, depending on the requirements of each installation.
One of the most common ones are the electro-mechanical point machines (Figure 33 and Figure 34), where electric power is transformed into mechanical by means of an AC or DC electric motor M. The motor rotation is spread on to the reduction gear R meant to strengthen the angular momentum and to reduce the rotary speed of the motor. Figure 33: EPM block diagram (R is a mechanical gear in The motor is connected with reduction gear electro-mechanical and a hydraulic gear in electro- via branch sleeve which allows an hydraulic point machine). Source: [22] 2.Background and literature study | 30
insignificant radial displacement of shafts while retaining a parallel position of their axes. To protect the motor from overloads, e. g. if the blades do not reach their end position due to an obstacle, and to ensure the braking of the revolving parts of the EPM after the end of switching the points, a friction gear is inserted. The Figure 34: Electro-mechanical point machine (Poland, rotating movement is transferred into manufacturer: Bombardier). Source: [22] the progressive motion of the throw bar TB in the last cascade of the reduction gear. the throw bar impacts upon the blades of the points through the point drive rod. The detection contacts DC provide checking of point positions and commutate the electric controlling circuits. Obtaining the checking signal about of point end position is only possible if the position of the detection bars DB conforms to that of the throw bar [22].
2.2.4.3. Lineside signals
Figure 35:Color and position light signals. Source: [1] According to Pachl [1], lineside signals are still the most common technology for controlling train movements. In railways (predominantly European) where train movements are strongly separated from shunting movements, there are two basic kinds of lineside signals: Main signals (1) and shunting signals (2). Main signals authorize a regular train movement to enter a line section. The movement authority is limited by the next main signal, or a point specified in the operating rules.
In railway operations, a signal that authorizes a train movement requires an approach aspect at the braking distance in approach to the signal because the stopping distance is generally greater than the range of vision. On lines where the distance between signals does not significantly exceed the braking distance, the approach aspect is usually provided Figure 36:Different Design of Lineside Signals. Source: [1] by the signal in rear. On lines with very 31 | 2.Background and literature study
long distances between main signals, distant signals are placed at the braking distance in approach to a main signal.
Lineside signals can be divided into semaphore and light signals. Being overwhelmingly common, light signals display their aspects by the colour or the position of lights. However, in new signal systems, pure colour or position light aspects are preferred. Most main signals are mounted on a high signal mast directly beside the track it governs. If there is not sufficient space between parallel tracks to place signal masts between them, the signal heads may also be mounted on signal cantilevers or signal bridges. On some railways, signals on slow speed tracks (or on shunting sections) may be designed as dwarf signals. Finally, concerning the control principle, signals can be controlled (1), Automatic (2) or semi-automatic (3).
Figure 37: Solutions to generate lights in different colours by filament lamp signals (principles). Source: [23] A more technical description of optical trackside light signals is given by [23]. Light signals today are designed with a filament lamp or with light emitting diodes (LED). The purpose of the converging lens system, usually solid or Fresnel lenses, is to gather as much light as possible from the lamp and to form a parallel light beam. The quality of light beam from a solid lens is higher, but in most cases a Fresnel lens is enough. The light is filtered by the colour filter. To provide different light distributions, different lens versions or additional distribution lenses are common (Figure 38). To generate switchable signals in different colours, signals with a filament lamp can be classified as multi-unit signals, searchlight signals or of an intermediate form (Figure 37).
Regarding the control and supervision of lamps, it can be assumed that light is emitted when a current flows through the filament only. Figure 39 shows a typical structure of a lamp circuit. Current is often transmitted to the signal at higher voltage to minimise energy loss. It is transformed to lower voltage in the proximity of the lamp. The cable can be modelled as a resistor with an inductive component. The cable also contains a capacitive Figure 38: Structure of a signal unit. Source: [23] leak impedance between the wires. A supervising unit in the interlocking, which is often a relay, detects the presence of a current continuously. This can prove that the lamp illuminates. The following circuit behaviour must be ensured: 2.Background and literature study | 32
− In the case of open circuit (e. g. filament broken), the current via the leak impedance must not exceed a certain value, which would prevent the supervising relay from dropping down. The longer the cable, the higher is the leak impedance and the stronger this current. − In the case of a short circuit, the current must be high enough to blow the fuse or to operate the automatic circuit breaker. Either will result in the disruption of the circuit and dropping of the relay. The longer the cable, the weaker is the short circuit current.
The result of both conditions is the limitation of the length of the cable, depending on the type of cable. Typical values are between 5 km and 10 km.
Figure 39: Lamp circuit for signal lamps. Source: [23]
Today, according to [23], especially on new interlockings and signalling installations, Light Emitting Diode (LED) are used instead, since advantages are the very long life compared with the filament lamp, as well as the potential for a reduction in power consumption. However, conventional interlockings are firmly linked to the filament lamp, which makes the introduction of LED preferable with newer installations. Nonetheless, the design of the signalling circuits to suit the filament lamp results in LED unit designs which try to adapt to its behaviour. Such LED units can be used to replace signal units with filament lamps. The electrical adaptation is provided by electrical driver circuits, the optical one by an adapted optical design. The architecture can be modified, depending on application. One possibility is using LED units with clusters. For more information on LED’s, see [23]. Figure 40: LED unit with clusters. Source: [23]
2.2.4.4. Block sections, train detection, separation, and track circuits According to Pachl [1], in a territory with a fixed block system, the lines are divided into block sections for the purpose of safe train separation. A train must generally not enter a block section until it has been cleared by the train ahead. In a territory with lineside signals, block sections are limited by signals, which govern train movements. A signal that limits a block section outside a station area is called a block signal. While the basic idea of train 33 | 2.Background and literature study
separation by fixed sections also applies on station tracks, many railways that separate the station areas from the open line use the term block section only outside of station areas.
In Europe, it can be stated that automatic block principle is the most applicable, which can be divided into decentralized or centralized ABS. In a centralised automatic block system, the control logic for all block signals between two interlockings is part of a centralised control system. Instead of exchanging block control information (decentralized ABS), the control of a centralised automatic block systems is based on so-called block routes which are set up from signal to signal. These block routes are in some way similar to interlocking routes, but they do not lock any points or other movable parts of the infrastructure. The block routes are just part of the block control logic [1].
In an automatic block territory, the occupation and clearance of block sections and overlaps is detected by track clear detection to enable the signalling system to work automatically. For track clear detection track circuits or axle counters are being implemented. Here, only track circuits are being considered [1].
A track circuit is an electrical circuit of which the rails of a section form a part. It usually has a source of current at one end and a detection device at the other. Sections are divided by insulated rail joints. If the section is occupied by a vehicle, the axles produce a short circuit by shunting the two rails. As a result, the detection device does not receive any current and therefore it detects the section as occupied. The detection Figure 41: Normally closed (Fail Safe) track circuit. Source: [24] device is often implemented by a track relay, which is in a picked-up position when the section is clear and dropped when the section is occupied. Since a track circuit is based on the closed-circuit principle, any interruption of the current will lead to a safe state by making the section occupied [1]. According to [24], regarding the form of current, track circuits can be classified into DC, AC with low frequency and AC with high frequency (usually jointless). It can be stated that the type chosen depends on the form of traction (AC or DC, electric or Diesel-electric), but also on the type of rail system. Another important topic is the treatment of traction return currents. One solution is that only one rail carries the return currents. For this purpose, either one rail is constructed without insulated rail joints and the other rail (the signal rail) with, or both rails have isolated rail joints and are 2.Background and literature study | 34
Figure 42: Return of traction supply through single rail, (a) only one rail is constructed with IRJ's, (b) both rails have IRJ's but used alternatively. Source: [24] used alternately for return currents and connected by diagonal connectors. The advantage of the latter is a higher level of safety in case of overmilling of the insulated rail joint.
a=rectifier, 7V, 6A, battery charger
b= rectifier, 7V, 6A
c=battery, 6V, 60 Ah
d= Adjustable resistor 0-6 Ω, 4A
e= Resistor 15 Ω, 2A
f = Circuit breaker 32A
Figure 43: Track circuit feed with or without battery for non-electrified lines. Source: [26] According to [25] [26], in Sweden Trafikverket employs DC track circuits for main lines as standard track circuits, with configuration on Figure 42a for return currents being the prevailing one (I-räl is designated as the insulated rail, while S-räl as the common rail). The feeding can be realized either through the catenary or through the public grid. In either case, a rectifier is used to convert power supply from 1- phase AC to DC current. Furthermore, a battery may be added for increased availability. Feeding, uptake and more technicalities regarding track circuits in Sweden are described in [26].
a= relay, JRK 10470 – 10474 b = Adjustable resistor, 30 Ω of which a maximum of 15 Ω shall constitute parallel resistors and have red-marked connection screws
c = Series-connected choke 2.6 Ω at DC and approx. 400 Ω, 16⅔ Hz (only in switches with switch heating)
d= lightning surge protection
e=external grounding
Figure 44: Track circuit uptake with lightning surge protection. Source: [26] 35 | 2.Background and literature study
2.2.4.5. Level crossings A level crossing can be defined as a crossing between rail traffic and road traffic at the same level, which includes active and passive warning devices [27], both towards the rail vehicles as well as towards road vehicles. Despite the occurring fatalities, many level crossings will remain for the foreseeable future [28], mostly due to the high price of grade separation: cost is 20 times more than basic level crossing equipment [29].
According to [28], a basic distinction between them according to ERA (European Union Agency for Railways) is between passive and active level crossings. The latter ones indicate to the road user whether a train is approaching or not. They can be distinguished by multiple criteria and different technical solutions Figure 45: Example of a level crossing (Germany) (photo: DB (in different combinations) can be applied AG/Christian Bedeschinski). Source: [28] as well, depending on the country. In Sweden, Trafikverket [30] [31]defines the technical standards for level crossings. They are divided into categories from AH to E, depending on level and type of protection. In this master thesis, only level crossings levels AH, A and B are considered (lights and barriers).
The most common devices involved in an active level crossing are:
− Light signals, which differ between the countries and usually placed inside, above or below the St. Andrew's cross. − Mechanical closure of the road. The most common solutions are half barriers and full closure (either by full barriers or by two pairs of half barriers). In some countries also other mechanical obstacles such as road blockers which can be sunk in the road are applied. − Additional audible signals, either given wayside or by the train. Wayside audible signals can be giving either during the closing of the barriers or continuously until the train arrives.
In Sweden, extra light signals are positioned towards rail traffic. A level crossing with a road protection system must be provided with a V-signal and in some cases with an extra V-distant signal [30]. It must be noted that level crossings are a self-standing autonomous system of interconnected TSE, controlled by its own Figure 46: V- distant signal (left) and V-signal with yellow operational hardware and software logic. Furthermore, they often square sign with the symbol "V" include more related equipment, depending on principle of (right). Source: [30] 2.Background and literature study | 36
operation, like track circuits or signals directed towards rail vehicles. An example of such an installation is presented on Figure 47.
Level crossings can be manually or automatically activated. In the latter ones, the operation is initiated automatically by the approaching/clearing train or by route calling in an interlocking system. The activation and deactivation are usually initiated by the train entering or leaving the approach zone. Suitable detectors are different kinds of spot wheel detectors, track circuits and magnetic inductive loops. To increase the reliability, the detectors are often doubled for redundancy [28].Other methods include frequency shift overlay circuitry or even combined with motion detectors [29] or balises to increase accuracy of activation/deactivation times of a level crossing. In ERTMS lv 2, it is feasible to use RBC to
Figure 47: Equipment plan of an active level crossing (example). Source: [28] trigger the activation of a level crossing [27]. A typical way of activation is through a 3-relay track circuits [27] [29] which also applies in Sweden. According to [27], track circuits detect the train position and logic remembers the driving direction. The warning signalling starts when predefined track circuits are occupied (and, if needed, after time delay). In analogy, warning signalling stops when predefined track circuits are passed in correct order, or after a time delay, if all track circuits are detected free (failure situation). An example of level crossing operation in Sweden is presented on Figure 48, where train is arriving from the left: In “rest state” the level crossing logic is ready for a train in both directions. While Train occupies track circuit Iv, the warning signalling starts (1), when Train passes track circuit Sv, the warning signalling stops (2) and when Train occupies track circuit IIv – level crossing logic returns to “rest state”.
(1) (2) (3)
Figure 48: Example of level crossing operation in Sweden. Source: [27] 37 | 2.Background and literature study
2.2.5. Civil works: Cable ducts and OC/SWOC foundations In general, when civil works in signalling infrastructure are being discussed, they include mainly civil infrastructure for accommodating signalling equipment. They can include foundations for RBC buildings/ radio antennas and OCs/SWOCs, as well as earthworks, and more specifically excavations and embankments for cable ducts and other equipment. Here, only foundations of OCs/SWOCs, as well as cable ducts for railway Figure 49: Plowing cable for an underground system. This machine digs trench, buries cable, signalling systems are being discussed. and backfills sod in one operation. Source: [32]
2.2.5.1. Cable ducts for signalling cables In regional railway signalling systems and particularly on rural areas, cables can generally be buried or put in a cable duct. Pansini states that the installation of cable directly in the ground by burying it saves the cost of building conduits/cable ducts and manholes and allows the use of long sections of cable, thereby eliminating the necessity Figure 50: Cable Ducts. Source: [32] for several splices [32]. However, in case of railway infrastructure, it is usually avoided since tamping actions during track maintenance may damage the cables.
In contrast, installing cables in underground conduit or duct systems is a more complex and costly operation than burying them directly in the ground. Underground cable is carried and protected by different types of ducts or conduits. The Figure 51: Cable ducts type 350, and type 535 employed by most used types of conduits or ducts are Trafikverket. Source: [33] [63] shown on Figure 50: precast concrete, plastic, fiber, and wrought iron pipe. The first three are usually used because of their lower cost. Because wrought iron pipe is comparatively costly, its use is generally limited to places where the space for conduits is shallow and where rigidity and strength are required. Conduits installed under roadways or other places subject to severe loading are sometimes encased in concrete. Ducts come in different sizes The size of the duct depends on the Figure 52: Installation of concrete size of the cable to be installed at the present or on any probable cable duct along the track. Source: https://steriks.se/globalassets/kabel size to be installed in the future. It should always be large enough rannor-produktblad.pdf to make cable installation as easy as possible [32]. Trafikverket 2.Background and literature study | 38
employs several different types of cable ducts depending on the situation [33]. Several representative designs are presented on Figure 51 and Figure 52.
2.2.5.2. Foundations for Object controllers Plinth foundations are one of the simplest form of foundations. They consist of concrete plinths which are embedded into the ground and on which a building is based. This solution is very useful for Object controller building foundations. The embedding depth, the number of plinths and their dimensions depend on the application. Figure 53: A cement plinth. Source: https://images.homedepot- static.com/productImages/0ddc9724- 2.2.6. Railway power supply systems and signalling fcae-4a10-a383- A modern railway signalling system requires power to work and 454440f8cf95/svn/cinder-blocks- 8053112-64_1000.jpg this includes almost all its components, especially when electronic interlockings, OCs and TSE are considered. Furthermore, modern railways in western countries are almost always work with electrified traction. The way a line is electrified (or not) is related with how power is provided to the signalling system.
In regional railway systems, when a line is electrified, Traction Power Substations (TPSS) are positioned along the line, providing the catenary with electricity, and forming a circuit with the tracks to power the trains. They are positioned in such a way that the voltage drops from a TPSS to the train and therefore the power loss, regardless of distance from TPSS and the prevailing traffic pattern, do not fall below a certain level: power must be enough to power up a train. TPSS are usually supplied with power from the main grid. Brenna et. al. [34] distinguish three main types Figure 54: Bilateral power supply, concentrated load at a distance x. Source: [34] of power supply for railways:
− DC electrification: simplicity and the possibility to derive the power supply directly from the primary lines at mains frequency without introducing unbalances makes this type of power supply attractive. The main disadvantage lies with the fact that the maximum attainable voltage is limited (3000 V commercially, technically 6 kV maximum). − Single phase at railway frequency: In electric rail traction, it is very important to be able to adopt high line voltages because only then can adequate power with sufficiently low current values be transmitted to trains (smaller voltages). This, combined with the requirement for only one overhead line (instead of 3 for 3-phasce AC) made the 1-phase AC electrification very attractive. Östlund [35] describes that at the time of the first world war, the Central European and Scandinavian countries (including Sweden) decided on electrification with 15 kV 16 2/3 Hz single-phase alternating current, due to the fact that 39 | 2.Background and literature study
at that time the existing traction motors could not operate with frequencies above 25 Hz and because it was suitable to use rotary converters to generate a low frequency – 16 2/3 Hz7. − Single-phase at mains frequency (25 kV, 50 Hz): Apart from increasing the available power even more, the great advantage that the adoption of single-phase mains frequency systems has is the possibility of greatly simplifying substations.
The signalling system elements follow the traction electrification as well, although especially for field elements there is a need to reduce the voltage and sometimes to convert it to another form. However, not all lines are powered, especially on the countryside, since traffic patterns may not justify the investment (substation cost is estimated between € 240,000 and € 370,000 per km and catenary between 180,000 and € 240,000 in 2008 values [36]). Signalling system elements can be powered by:
− Main grid (most common for rural areas). − Dedicated power distribution (rarely) − Electrified line (catenary)
In the case of rural areas, powering from the grid is the preferable solution. The substation must be within acceptable limits to minimize power losses and voltage drops. In Sweden, according to Wangel [37], the power grid has three levels: the national transmission grid, the Figure 55: The power system includes both the grid infrastructure and the electricity market. Source: [37] regional distribution grid, and the local distribution grid (Figure 55). The national grid consists of 220 kV and 400 kV cables. The regional grid connects to the national grid via converter stations and has a lower voltage, usually 40–130 kV. The local grid connects to the regional grid, again via converter stations. From the local grid, with voltage levels of 20 kV or lower, the electricity is transformed in the distribution areas to the low voltage 400 V /230 V that is used in domestic households.
2.2.6.1. Alternative energy sources for local power supply of SWOC Powering signalling equipment, including OC/SWOC, via main grid can be a challenge, especially in rural areas, where long cables must be deployed, and catenary does not exist, which sometimes can increase cost to a great extent. This sparked the interest for using local renewable sources of energy, including PV, wind energy, fuel cells etc. in this case. This type of power scheme is one of the main concepts behind SWOC project. For reasons of efficiency and redundancy, several power generation technologies can be combined. In general, such solutions are possible, however the technologies behind must be proven, commercial and technologically mature. An issue with this solution is that energy from renewable energy
7 One of the most important issues was whether the electrical power would be produced in special power stations for the railway or if the existing three-phase grid should be reinforced to provide the single-phase rail network with power through converters. The latter solution was eventually chosen in Sweden [35]. 2.Background and literature study | 40
sources cannot be produced on demand but depends on either the wind speed variation/days with wind or the occurrence of days with clear weather to power up PVs. To that extent, batteries for storing up energy can be used during windless or non-sunny days. However, batteries performance is affected by temperature and due to energy losses (leakage) they cannot store the spere energy forever. Therefore, systems of this kind must be designed with a diversified modus operandi and employ energy sources in such a way that the solution creates redundancy.
Jerresand & Diamant [38] developed a model which estimates the energy usage of a SWOC system and dimensioned it based on energy requirements of TSE, the SWOC themselves and the power losses by cabling, taking also in account existing commercial and technologically mature solutions and their limitations as well as the prevailing traffic patterns. They distinguish several ways of energy storage and harvesting. For energy storage they discuss mechanical storage (flywheel), chemical, batteries, electrical (capacitors) and hydrogen, while for energy harvesting, they discuss renewable energy sources (PV and wind power), mechanical (piezoelectric), electromagnetic and chemical (fuel cells). In this work only photovoltaic and wind power facilities, as well as batteries are being discussed. Furthermore, the calculation of required infrastructure is based on power rather than energy calculations.
2.2.6.2. Photovoltaic arrays and solar energy Photovoltaic systems convert electromagnetic radiation into electricity. A photovoltaic system consists of an array of solar cells. In short, according to Kanoğlu et. al. [39], the solar energy reaching the earth’s atmosphere is called the total solar irradiance Gs, whose value is:
푊 퐺 = 1373 (16) 푆 푚2 However, due to effects of atmosphere and of relevant phenomena (e.g., absorptions by the clouds), the solar energy reaching the earth’s surface is weakened considerably, to about 950푊/푚2 on a clear day and much less on cloudy or smoggy days and varies by season. Another restrictive effect is the efficiency of solar cells. Silicon has been commonly used in solar cells, but the commercial silicon solar cells have a low efficiency (between 15 and 20 percent). Considering the values observed in northern Europe, it would be reasonable to assume an average value between 100 and 200 푊/푚2 for PV panels. A single solar cell produces only 1 to 2 W of power. Multiple cells should be connected to form modules and modules should be connected into arrays so that reasonable amounts of power can be generated.
In the context of SWOC, the best solution is stand-alone hybrid system. That would be systems where the solar energy yield is matched to the energy demand. Since the solar energy yield often does not coincide in time with the energy demand from the connected loads, additional storage systems (batteries) are generally used. If the PV system is supported by an additional power source – for example, a wind or diesel generator - this is known as a 41 | 2.Background and literature study
photovoltaic hybrid system [40]. In terms of electricity type, PVs are producing DC current, therefore an inverter is required to convert the power to AC. Furthermore, number of inverters and configuration of PV panels play a role regarding system power capabilities. Finally, regarding installation, free-standing installations require sturdy and weather- resistant support structures. The selection and usability of mounts and foundations depend upon the quality, the load, and the pH value of the ground. There are also other special Figure 56: Concept with central circumstances that may have to be considered, such as shallow inverter and higher voltages Source: Solarpraxis, cited in [40] topsoil layers, if the PV installations are to be built on former landfill sites. Stone or concrete strips or slabs are frequently used as pad foundations, which are either precast or made in situ as well as timber post or steel screw foundations, which are easier to be removed, do not require earthworks but are not suitable for all types of ground and require sufficient depth. Frames can be made of both timber and metal. Furthermore, panels are always positioned on a specific angle which optimizes their position in relation to sun and therefore maximizes energy absorbed but can also be equipped with passive or active tracking systems which track the sun position on the sky. In the latter case (tracking PV arrays), on days with high insolation Figure 57: Steel screw foundation (left), Aluminium frame on concrete pad and a large direct radiation component, a tracking foundations, (upper right), Galvanized steel system enables relatively large radiation gains to be frame on Gabion foundations (lower right). Source: [40] achieved. In summer, a tracking system achieves around 50 per cent radiation gains on sunny days, and in winter, 300 per cent or more, compared to a horizontal surface [40].
2.2.6.3. Wind Power According to Kanoğlu et. al. [39] a wind turbine converts the kinetic energy of the fluid into power. If Figure 58: Solar farm on the former Erlasee experimental vineyard near Arnstein, the wind is blowing at a location at a velocity of V, the Germany: The planned 1500 independent available wind power is expressed as: SOLON Movers have a total power output capacity of 12MW. Source: SOLON AG, Paul Langrock, cited in [40] 1 푊 = 푚푉2 (퐾푊) (17) 푎푣푎푖푙푎푏푙푒 2 This is the maximum power a wind turbine can generate for the given wind velocity V. The mass flow rate is given by: 2.Background and literature study | 42
푘푔 푚 = 휌퐴푉 ( ) (18) 푠 where ρ is the density and A is the disk area of a wind turbine (the circular area swept out by the turbine blades as they rotate). Substituting, the potential wind power can be found:
1 푊 = 휌훢푉3 (퐾푊) (19) 푎푣푎푖푙푎푏푙푒 2 They also state that every wind turbine has a characteristic power performance curve (speed vs power), where three key locations on the wind-speed scale can be identified:
− Cut-in speed is the minimum wind speed at which useful power can be generated. − Rated speed is the wind speed that delivers the rated power, usually the maximum power.
Cut-out speed is the maximum wind speed at which the Figure 59: Typical qualitative wind- wind turbine is designed to produce power. At wind turbine power performance curve with definitions of cut-in, rated, and cut-out speeds greater than the cut-out speed, the turbine blades speeds. are stopped by some type of braking mechanism to avoid damage and for safety issues.
the efficiency of wind turbines usually ranges between 30 and 40 percent. Regarding the possible installation configurations, when a wind turbine project is underway on a windy site, many turbines are installed, and such sites are properly called as a wind farm or a wind park, which is highly desirable due to reduced site development costs, simplified transmission lines, and centralized access for operation and maintenance. Single use of a wind turbine is used for off-grid homes, Figure 61: Optimum spacing of wind turbines in a wind farm. (Adapted from off-shore areas, and Yao et al., 2011.). Cited in [39] demonstration projects. The number of wind turbines in a site depends on the spacing between the turbines. It turns out that there is an optimum spacing between the turbines, and it is estimated to be 3 to 5 blade diameters between the turbines in a row and 5 to 9 blade Figure 60: A small wind turbine on diameters between rows, as shown in Figure 61. a 16-meter (54 feet) monopole tower. Source: [42] Regarding the foundations of wind turbine, the design is largely driven by the tower base overturning moment under extreme wind conditions. A variety of slab, multi-pile and monopile solutions have been adopted for tubular towers [41]. However, for small turbines, foundations are simpler since the towers are simpler. A typical example 43 | 2.Background and literature study
are the foundations for Freestanding towers, which must be sufficient to support the downward load of the tower and turbine plus the overturning loads on the tower and turbine. Another type of towers are Guyed towers, which have even more simpler foundations [42].
2.2.6.3. Energy storage system-batteries Energy storage is required in most stand-alone systems, as energy generation and consumption do not generally coincide. The solar power generated during the day is very often not required until the evening and therefore must be temporarily stored. Longer periods of overcast weather Figure 62: A base foundation ready for concrete (left) and a base also must be catered for [40]. The attached to a foundation (right). Copper wire is grounding for lightning protection. Source: [42] same applies for wind energy: It may be needed when there is no wind. The energy storage function is provided by batteries, amongst other things.
A short but intuitive description of batteries is given by [43]. Batteries, have a specific energy stored inside them, which can be defined as:
퐸 = 퐶 × 푉 (20)
Where 퐶 is battery capacity in Ah, 퐸 is energy in Watt-hours and 푉 is battery voltage. Da Rosa [44] explains that the capacity 퐶 is a measure of how much charge a battery can deliver to a load. It is an imprecise number because it depends on temperature, age of the battery, state of charge, and on the rate of discharge. Formally, for a constant rate of discharge, 퐼:
퐶 = 푡퐼 (퐴ℎ) (21)
Where 푡 is time in hours and 퐼 is current in amperes. Torabi and Ahmadi [43] state that the capacity of a pack of battery, which consists of many identical cells in series, is the same as the capacity of a single cell because the same amount of current passes through all the cells (connecting batteries in series increases voltage. However, the capacity of the pack increases if the cells were connected in parallel because in parallel in connection the current passing through the pack is divided between the cells (connecting batteries in parallel increase Ah capacity 퐶). In both cases the energy content of the pack increases because its energy content is the sum of the energy contents of the individual cells, regardless of their connection type. The capacity of battery also depends on its material and its operational time is inversely proportional to the current- the more is drawn, the less it lasts. Finally, other important parameters are how many charge-discharge cycles a battery can have before cease functioning, as well as what is battery’s discharge rate. For a lithium battery this would be between 300 and 500 cycles, while discharge rate depends on the battery properties and temperature conditions. 2.Background and literature study | 44
2.3. The Smart wayside object controller (SWOC) Earlier, it was stated that in a modern electronic interlocking, Object Controllers (OC) act as interface between TSE and interlocking computer by giving orders to TSE and receiving information from TSE. Furthermore, they group different objects together and, in many cases, provide power supply to them (see Figure 10, Figure 27). Today’s OCs are designed and developed by each supplier in a different way. They are interconnected via copper cables with TSE and the power supply [45]. Fiber optics are usually used in order to connect OCs with the interlocking. The practice is to use OC’s when TSE is geographically distributed and away from interlocking, while direct connections with the interlocking are used in case of short distances (Figure 9). According to [45], there are disadvantages to these solutions:
1. It is expensive to provide cabling for power and data to remote TSE, especially in freight lines or regional lines featured by light traffic. 2. The cable provided is vulnerable to cable theft, which is costly, and causes disruption. 3. Changes within track layouts (position of TSE) are complex and costly. 4. The usage of cable restricts distances between TSE and interlocking, which might demand additional equipment.
They state that if it is possible to remove cables, then LCC of installations can be reduced significantly in the following areas:
− Material costs − Energy costs − Installation costs − Cost occurring because of cable theft − Maintenance costs
As it is described in [46], to that end, IP 2 contains the project titled “TD2.10 Smart Radio connected wayside object controller”, which is one of the 11 Technology Demonstrators defined in IP2. The question here is what a SWOC is and what innovations can it bring on the field.
In many aspects, a SWOC resembles a typical OC. However, in comparison, it incorporates many innovations. Bombardier [46] states that the project purpose is to develop a solution with the following characteristics: Figure 63: Smart Wayside Object Controller. Source: [45] − Scalable and flexible solution, which fulfils different configurations and scenarios. − Use of locally derived power – From renewable and alternative energy sources. − Use of wireless communications, independent of media. A SWOC will be able to use different communication protocols, ranging from GSM-R and UHF to TETRA and 5-G. − Enable de-centralisation (up to the level of one Smart Object Controller for every individual TSE). − Significant reduction of trackside cabling, and associated cable routes, ducting etc. 45 | 2.Background and literature study
− Use of residual bandwidth in the communication system for transmission of diagnosis reports / maintenance information. − Generation of benefits like lower investment costs, reduced operating costs, improved standardisation, and therefore simplified certification / authorisation.
A SWOC will be able to communicate wirelessly not only with the central interlocking computer/TMS, but also to have bi-directional communication with other SWOCs as well as with trains. Furthermore, SWOC will implement distribution of intelligence, including smart routing capabilities. This will be implemented by including interlocking functions in the SWOC. This practically implies locally available interlocking on site, which can bring distribution of complex functionality to simplify the system and to speed up execution of orders.
The existence of local interlocking implies a hierarchy between the SWOCs on the field. SWOCs which carry the local interlocking logic are called master SWOCs, while the ones receiving information from the Master SWOC and just controlling a group of TSE are called slave SWOCs. In any case, a local interlocking can relay or receive data to and from the higher interlocking levels. Another important feature of the SWOC system is that it can be powered locally, through a dedicated power supply and storage system. As discussed before, a standalone hybrid system composed of wind turbines, solar panels, batteries and/or other power sources (fuel cells, supercapacitors, flywheels etc) has the ability to create viable local power supply system, at least for low traffic density lines. The most important contribution of a SWOC system is that it can reduce the cabling and associated civil works considerably: through better grouping and positioning of SWOCs, through better positioning of local energy supply in relation to infrastructure it powers and through the elimination of a physical connection not only between SWOCs but also between SWOCs and the interlocking, since interlocking is decentralized and the relay of information to higher levels is done wirelessly. A presentation of SWOC system in comparison to OCS is done on Figure 64. 2.Background and literature study | 46
Figure 64: Comparison between OC and SWOC systems. Own edit
A high level of SWOC Product and system description is presented on Figure 65. Its most fundamental parts are the following [46]:
− EBITOOL, TOOL_MINT and MDC: software responsible for configuring the OCS related equipment, automated tests, and collection of maintenance diagnostics respectively. − PD (Power distribution) board: Its task is the support of low power mode through interface with OCS PSUs by means of controls that will power on/off the required PSUs. Furthermore, it will be capable to power on/off each single object controller, depending on information from VAC board. − VAC board(s): The VAC board(s) is the core of the system. It is the vital platform on which the simple needed interlocking logic will run. Also, the VAC will implement the communication interface to the communication network for SWOC-to-SWOC 47 | 2.Background and literature study
communication and also the communication interface with the power system for the power related functionalities. − Object controllers: they are located in the OC rack and used to physically interface the VAC(s) to the wayside object such as Signals, LX Signals, Barrier Machines etc. The Object Controllers will be based on OCS950 platform. − PSUs (Power Supply Units): OCS950 system uses linear power supply to power the wayside objects such as Signals or point machines. Those power supply will be used as they are, and they will be also controlled by the PD board for the implementation of the low power mode. A PSU is a type of transformer without active components. − Power system and batteries: The power system will be an intelligent UPS system that will entirely handle the interface with the grid line or renewable power sources, the batteries and will provide the needed power to all the objects belonging or interfaced with the SWOC. One of the functionalities that will be implemented will be to inform the VAC about the status of the batteries so that the VAC can implement the power saving strategies accordingly. − Telecommunication system/radio: The telecommunication system will be composed by an internal network which connects the Board VAC(s), the power system and the external objects such as adjacent SWOCs, Train and any other external system to which the SWOC will need to be in communication with. The system will implement 2 antennas - 1 for communication between SWOCs and between SWOC and interlocking. Each antenna is around 2-3 meters and is bidirectional.
Figure 65: SWOC: Definition of the system Architecture and interfaces. Power interfaces are red arrows, communication interfaces are green arrows and control & monitor signals are yellow. Source: [46]
2.Background and literature study | 48
It must be noted that in comparison with a master SWOC which utilizes VAC boards, a slave SWOC will utilize DCM board. It is a same board type, but VAC boards have A & B + C processor for HW independence for SIL4 applications, whilst DCM board is a “stripped” VAC board without the complex set up of processors for use as communication and non SIL applications.
Finally, on the field, ideally the SWOC will be composed of a TOB with 2 indoor enclosures Figure 66: Outdoor enclosure, housing SWOC, UPS (back-to-back enclosure. Alternatively in case and batteries. Courtesy of ALSTOM. of no building exists, an outdoor enclosure housing both SWOC, UPS and batteries can be constructed. Finally, it is also feasible to have several different enclosures for all the equipment.
One of the main impacts expected by the implementation of SWOC is the decrease of LCC for parts of signalling system, mainly through smarter energy consumption and reduction of required infrastructure, as well as cabling. The last part of this chapter will describe the fundamentals of LCC.
2.4. Fundamentals of LCC analysis A good perspective regarding LCC and LCCA can be taken from Farr & Faber [47], where the engineering economics of life cycle cost analysis are discussed in detail. Here, only basic points are presented from their work. They state that in the 21st century, for engineers, beyond technical excellence, understanding the economics or business aspects of modern engineering as well as having a LCC perspective of their products is key to success both for companies employing engineers as well as for engineers who design products, services, and systems. But what are LCC and LCCA?
In general, Life Cycle Costs are all the anticipated costs associated with a project or program throughout its life. LCC is the sum total of the direct, indirect, recurring, non-recurring, and other related costs incurred, or estimated to be incurred, in the design, research and development, investment, operations, maintenance, retirement, and any other support of a product over its life cycle. All relevant costs should be included regardless of funding source, business unit, management control, and so on. LCC is important for systems because the acquisition is a small part in relation to the true cost or TOC associated with owning and operating the systems [47].
In terms of methodologies for determining LCC, there are 4 generally accepted, and either of them or all of them could be combined to develop the TOC [47]: 49 | 2.Background and literature study
− Engineering build-up methodology: Sometimes referred to as “bottom-up” estimating, the engineering build-up methodology rolls up individual estimates for each element, item, and component into the overall cost estimate. This can be accomplished at the work breakdown structure element level or at the component level. In this costing methodology, the cost of a work breakdown structure element is computed by estimating at the lowest level of detail and computing quantities and effort levels to determine the total system cost. Obviously, this is the most accurate means to develop a cost estimate. The challenge is that early in the systems development a bottom-up approach cannot be used because the systems haven’t been fully designed. Ideally, you would like to take bottom-up estimates and scale them based on experience. − Cost accounting: modern cost management systems to track and allocate expenses. − Analogy Cost Estimates: they are performed on the basis of comparison and extrapolation using like items or efforts. In many instances, this can be accomplished using simple relationships or equations representative of detailed engineering builds of past projects. Obviously, this is the preferred means to conduct a cost estimate based on past programs that are technically representative of the program to be estimated. Cost data is then subjectively adjusted upward or downward depending on whether the subject system is felt to be more or less complex than the analogous program. − Parametric Cost estimation (PCEs): they are usually based on mathematical equations or models. Simple mathematical relationships, such as linear and non-linear regression, are mainly used. Often, they are based on historical data from similar projects. The biggest challenge is determining the relationships between the dependent and independent variables and their range of usefulness.
These methods are suitable for different stages of a system/product life cycle; however, a detailed engineering build-up methodology becomes more relevant as one goes forward within the life cycle (most relevant during production phase). This can be seen in Figure 67.
Figure 67: Cost estimation techniques throughout the life cycle. Source: [47], courtesy of NASA, 2015 2.Background and literature study | 50
For engineering economics in general, a whole range of techniques are implemented to allow for comparisons by accounting for the time value of money (TVM). This is usually manifested as calculations for present, future value or calculating the influence of inflation on prices of assets. For more advanced economic calculations, particularly when an economic model is constructed, a sensitivity analysis is being performed, which is the study of how inputs, variations, and assumptions affect the output of a mathematical model and constitutes an important component of all economic analysis. Sensitivity analysis allows us to [47]:
− Identify the key input elements, which can allow for more effort quantifying the value of the most important inputs. − Develop a visual presentation of the effects of various inputs on the output, and − Ask “what if” to determine the amount of change in a data point that might change the output of the analysis.
A simple example of sensitivity analysis is presented in Figure 68, where the impact of fuel price on monthly cost for two different Figure 68: Sensitivity analysis for a hybrid vs a traditional cars on the basis of initial costs and miles car. Source: [47] driven annually is examined.
Apart from the previous points, LCC and LCCA must also be examined from a view of the perspective it adopts for a product/system, as well as from the perspective of model building. From a model building perspective, life cycle cost analysis (LCCA) is an economic evaluation technique that determines the total cost of owning, operating, and disposing of a system over its lifespan. Conducting LCC analysis requires us to not only understand the concept of the time value of money (including price escalation, inflation, cost of capital, depreciation, and taxation) but also to capture the true TOC. When building a model for LCCA, there are two principal types of uncertainty that LCC model builders are advised to consider:
1. Uncertainty regarding the cost-generating activities. 2. Uncertainty regarding the expected cost of these activities.
Both present unique challenges. In many respects, developing the categories is more challenging than estimating the costs. As espoused by the Deming Institute (2013), “The most important figures that one needs for management are unknown or unknowable but successful management must nevertheless take account of them.” This was the motive for developing and presenting a categorization methodology, with Figure 70 representing the top-level categories. 51 | 2.Background and literature study
Once the categories have been developed, the next step is to ascertain the costs and then develop a LCC model. A simple process for developing a life cycle model is shown in Figure 69.
Figure 69: Process for developing an LCC model. Source: [47]
From a view of LCC perspective, LCC can be viewed from a pre- and post-production perspective, with some typical main categories as shown in Figure 70. This figure shows a partial list of LCC general categories that can be used to develop more detailed costs. Every system is unique, and this figure is by no means an all-encompassing list. Nonetheless, several key cost categories can be detected [47]:
Figure 70: Some general LCC categories. Source: [47]
− Research, development, testing, and evaluation (RDT&E) cost is the most commonly accepted term used to encompass development activities prior to production. From a development perspective (pre-production), these are the most difficult costs to ascertain because the product architecture has not yet been developed. Table 7 (see Appendix A: 2.Background and literature study | 52
Literature review) lists some of the cost categories and elements used in developing a LCC model. − Acquisition Costs: The term “acquisition” is meant to include any aspect of producing the technology, such as buying, manufacturing, producing, and so on. Table 8 (see Appendix A: Literature review) is a partial list of cost categories and elements that are associated with acquisition or production. One item often overlooked is inventory- holding costs. − Operations and support costs: The operational life of a product drives the post- production LCC. Developing good post-production costs for O&S is critical to capturing the TOC. Table 9 (see Appendix A: Literature review) lists some LCC categories for the O&S phase. In building a LCC model, ascertaining these costs is critical because of their relative contribution to TOC. Table 3: Some LCC categories for disposal expenses. − Disposal or retirement costs: Unless special Source: [47] conditions apply, planning for disposal costs is relatively straightforward. The problems arise in special cases such as when asbestos, nuclear energy, funding retirement plans, some drugs, and so on are involved. Table 3 lists some of the cost categories and elements for disposal or retirement of a product.
2.4.1. LCC of railway signalling projects The LCC of railway projects which are related to signalling and specially to infrastructure side are possible to be divided into the following costs, assuming they are implementing a researched signalling system with well-defined parameters:
− Planning/design costs: considering a part of a rail network (e.g., a station), these costs include the consultant’s work to plan the needs for signaling equipment and for the infrastructure which will accommodate the said equipment (usually civil works or cabling). Examples of these costs include the production of drawings or signal plans for a station. − Capital Expenses (CAPEX): this stage includes the material procurement, transportation to the site, construction, and installation of civil works and of the equipment. To that, wages of technicians doing the fieldwork must be taken into account. − Operational Expenses (OPEX): This stage include the costs occurring during the stage of operation. This includes maintenance of different parts of the infrastructure but also the cost of parts being replaced due to malfunction or dur to accident/sabotage. For railway systems, these costs are usually calculated for 25-30 years of operations. − Disposal costs: this cost includes the process of disposal, which can be different for parts of the signalling project. 53 | 3.Methodology
3.Methodology This section describes the methodology followed to estimate the LCC for the SWOC solution and to form a basis for comparison between SWOC and typical OC alternatives. In short, for this purpose, the railway station at Björbo was chosen as a case study, which is equipped with a typical OCS, but utilizes modem to communicate with the corresponding interlocking at Borlänge, since it is operated under ERTMS-R. However, for the sake of the work, it was assumed that the existing OC does not implement modem, but rather a conventional link with the interlocking, by utilizing FO. The main TSE deployed in the vicinity of the station were identified and distances between TSE interface points and the OC, as well as between OC and nearest interlocking computer were measured. This would constitute the nominal case, against which all the comparisons will be made: the conventional OCS system. This existing system has a specific LCC, which is going to be the base for every other configuration.
Using the Björbo station as a template, the next step is to create alternative scenarios and test the effect of different parameters, with the focus being the replacement of a typical OC with a SWOC. The aim is to estimate the LCC of SWOC and compare it with that of a conventional system. Here, two main scenario groups can be seen:
− Scenarios involving changes in the number of OC controlling the station in conjunction with the number of TSE, size of station and distance from power supply. − Scenarios which involve changing OC with SWOC as well as changing the numbers of SWOC controlling the station in conjunction with numbers of TSE, size of station and the size of local power supply and storage system
Therefore, the first alternative will be just to replace OC with SWOC and optimize its position in relation to existing TSE to see its effect on the LCC, when SWOC vs OC is used. After that, alternatives with different conditions will be tested, but the center of comparison will
Figure 71: Estimation of LCC for OC/SWOC systems. Own edit 3.Methodology | 54
always be OC vs SWOC installations. The scenarios are presented in Figure 84. To be able to perform such kind of sensitivity analysis, models must be built, and this chapter describes the building of scenarios, as well as the estimation of LCC models. The process is depicted in Figure 71. The mapping was performed on AutoCAD, while mathematical modelling is done in MATLAB.
3.1. Case study: Björbo and Västerdalsbanan Björbo is an urban area in the municipality of Gagnef, in Dalarna County, which is in the Västerdalälven valley and along the E16 (Västerdalsvägen) and motorway 66, which here Figure 72: Station building at Björbo station. Source: deviates from the E16 towards Ludvika. The https://upload.wikimedia.org/wikipedia/commons/ population of Björbo is 658 residents [48]. In other 2/2c/BjorboStn.jpg words, Björbo is a small town located in the countryside, away from big cities (distance from Borlänge is roughly 50 km) with a low accessibility.
In addition, Björbo constitutes part of Västerdalsbanan, which is served by 6-8 freight trains per day. Freight transports on the line are dominated by Figure 73: Västerdalsbanan. Source: [49] timber transports from the timber terminal in Vansbro to the paper mills, mainly in Dalarna and Värmland. In addition, wagon load transports are conducted to a lesser extent from a number of suppliers. The freight traffic is relatively extensive for being an unelectrified railway. The wagon trains run under the auspices of Green Cargo. In 2009, the Västerdalsbanan interest association conducted a series of interviews with the companies along the line as the largest freight generators. Of the companies interviewed (see Figure 99, Appendix B: Methodology), only three companies today transport their goods by rail and only one company (Rågsveden Såg) had clear plans to expand its rail transport significantly under the above conditions. However, they have certain reservations, including the fact that rail transport would not cost them more than a corresponding truck transport. Passenger services on the line were discontinued in December of 2011 due to relatively low speeds, low passenger traffic demand, poor maintenance and reluctance from state’s side to pay for a very expensive rebuilding of trains (20 million), in order to comply with ERTMS-R standards [49] [50]. These line characteristics imply that the LCC of any installation (including signalling) along the line must be as low as possible to be a viable technical solution, as this is a rural line with low traffic and low priority in terms of upgrading and maintenance by Trafikverket. 55 | 3.Methodology
Table 4: Background of the Västerdalsbanan line. Source: [49]
3.2. Björbo station layouts and TSE within the station To estimate the LCC not only of SWOC but also of the conventional solution, the topology of signalling equipment of a railway installation is needed. For this task, Björbo signalling infrastructure plans [51] were provided by ALSTOM8. Furthermore, to be able to interpret such signalling plans, a document which explains the symbology on these plans produced by Trafikverket was utilized [52]. Plans of the station’s layout were digitalized with the help of AutoCAD and expertise regarding the installation and the placement of signalling equipment on the field was provided by ALSTOM.
Apart from the infrastructure plans, it is equally important to define the layout spatially and for that, RGB orthophotos from Björbo station as well as panchromatic photos which cover the track all the way up to the interlocking computer in Borlänge. Orthophotos were downloaded from SLU geodata extraction tool. [53] Another important aspect is to get information regarding the local power supply lines/substations as well as property boundaries in the vicinity of railway station. That was done with the help of material from Lantmäteriet [54] and a legend for 1:50,000 maps [55]. This is done in order to place the signalling equipment in absolute geographical coordinates (x,y in meters, SWEREF 99 TM projection system) relative to the track layout and being able to measure the distances between interlocking, OC/SWOC and TSE, as well as between OC/SWOC and the power source, be that for the nominal case (typical OC) or alternative (SWOC). Furthermore, it is important to determine whether there is space for the placement of a local power source at the station with the existing property or if there is need for acquiring extra land/ROW for its placement. This information was incorporated into the AutoCAD
8 ´´Planritning´´, ´´Kabelplan´´, ´´Isolerplan´´ and ´´instruktionsritning´´ were the most useful types of schematics 3.Methodology | 56
Using this methodology, a simplified schematic of the layout under the nominal scenario9 at Björbo station can be produced (Figure 74), as well as for the alternative scenarios, which are examined below. More detailed plans can be found in the appendix. These types of drawings can be used to give a short, yet accurate picture of the signalling equipment involved without sacrificing detail.
3.3. Calculation of distances between signalling objects, OC/SWOC, interlocking and power source The aim of the SWOC concept is to reduce cabling (signal and power cables) as well as associated costs of construction, installation, and maintenance. To calculate the economic effect of using SWOC instead of OC, the following distances between different parts of the signalling system should be found as follows:
Figure 74: Simplified schematic of Björbo Station-Nominal scenario (OC). Source: Own edit
− Distance between interlocking and OC/SWOC: currently both EBI 850 interlocking (responsible for lines equipped with ETCS LV1/2) as well as TCC Interflo 150 ERTMS- R, integrated RCB+interlocking (responsible for lines equipped with ERTMS-R) are located at Borlänge station. The salient assumption here is that since the precise location is not known, it is assumed that the signal cables are extending from the platforms of Borlänge station, all the way to the first switch at Björbo station (station entrance), which
9 The OC located at Björbo is connected with interlocking through modem, however for the calculations we assume a nominal case (a typical installation which include fiber optic cables) vs a scenario with wireless communication (SWOC). 57 | 3.Methodology
is located at the southeast side. Furthermore, as a common practice in Sweden, fiber optics are placed either in cable ducts or plastic tubes right next to the track, so the length was calculated according to track geometry. To that, distance between the first switch and OC is also added to the sum. That would be the distance between the typical interlocking and OC. For SWOC, since the interlocking logic is decentralized on the field and communications are preformed via RCB/wireless means, fiber optics are not needed and thus this distance is zero. − Distance between OC/SWOC and TSE: since a detailed cable plan for the station is not given, it is assumed that the length of copper cables will be given by the relative distance between the centroid of OC/SWOC and the reference point of a TSE. In case where an electric cabinet exists next to the object (or a control box for a level crossing) it can be considered as a reference point. If not, then the reference point is replaced by the centroid of the TSE. It must be noted that these distances are probably larger, since cabling connection is not direct but follows the track geometry. − Distance between OC/SWOC and power supply: In case of Björbo, Västerdalsbanan is a non-electrified line, which means that signalling equipment must be powered by the grid. In turn, this implies that a substation usually acts as a supply point and a power cable is drawn to the OC, which in turn acts as a power distribution to all TSE connected to it. In case of Björbo, the exact position of the local converter is nearby the station (Figure 102). In case of the alternative scenario, SWOC will be powered by a local power supply source, therefore the distance will equal that between SWOC and the facility which produces the power locally.
3.4. Number and location of object controllers/SWOC With the current scheme of signalling equipment at Björbo station, only one OC is responsible for controlling all the TSE within the station. However, a question arises whether there is a better configuration with more OCs/SWOCs, since usually TSE is not uniformly dispersed but appears to be concentrated in clusters. Bearing that in mind, sometimes it is better to use more than one OC/SWOC for a station in a scheme where one OC/SWOC is responsible for a cluster of objects to minimize the cabling required. It is assumed that the basic relationship here is whether there is an economic benefit by adding one or more OC and eliminating cabling between OC and TSE (cost of additional OC vs cost of cables removed). In that sense it is expected that SWOC will outperform existing OCs, not only because of greater system flexibility, but also because SWOC has not a physical connection with the interlocking. This means that while the cost of cabling between interlocking-OC- TSE are partially indifferent towards the distances between them, depending mostly on cost of fiber optics vs copper cables (while the distance between OC and TSE diminishes, the distance between OC and interlocking increases), in SWOC the cabling cost between SWOC and TSE is not indifferent towards the distances between SWOC and TSE, since there is not an “opposing cost” (see Figure 103). 3.Methodology | 58
The main purpose here is to examine whether there is an optimal position for the additional SWOCs as well as an optimal number of SWOCs for a given set of TSE. More general aims are to evaluate the economic tradeoff between reduced cabling and more SWOCs as well as how a pattern of OC/SWOCs affects the cost. For that, the K-means algorithm will be implemented to examine the optimal position/number of SWOC. To that purpose, a script was written in MATLAB programming language.
3.4.1. K-means algorithm A quite robust methodology which can help with determining the optimal number of SWOC/OC for a given pattern of TSE at a station is the K-means clustering. Being a machine learning technique, which is used in data analysis, the K-means clustering, according to Bruce and Bruce [56], is a technique to divide data into different groups, where the records in each group are similar to one another. A goal of clustering is to identify significant and meaningful groups of data. K-means divides the data into K clusters by minimizing the sum of the squared distances of each record to the mean of its assigned cluster, which is referred to as the within-cluster sum of squares or within-cluster SS. K-means does not ensure the clusters will have the same size but finds the clusters that are the best separated.
The algorithm starts with a user-specified K and an initial set of cluster means, then iterates the following steps [56]:
1. Assign each record to the nearest cluster mean as measured by squared distance. 2. Compute the new cluster means based on the assignment of records.
The algorithm converges when the assignment of records to clusters does not change. For the first iteration, you need to specify an initial set of cluster means. Usually, you do this by randomly assigning each record to one of the K clusters, then finding the means of those clusters. The two most important outputs from the K-means algorithm are the sizes of the clusters and the cluster means.
Finally, when it comes to selecting the cluster numbers K, the K-means algorithm requires that you specify the number of clusters K. Sometimes the number of clusters is driven by the application. In the absence of a cluster number dictated by practical or managerial Figure 75: The clusters of K-means applied to stock considerations, a statistical approach could be price data for ExxonMobil and Chevron (the two used. There is no single standard method to find cluster centres in the dense area are hard to distinguish). Source: [56] the “best” number of clusters. A common 59 | 3.Methodology
approach, called the elbow method, is to identify when the set of clusters explains “most” of the variance in the data. Adding new clusters beyond this set contributes relatively little incremental contribution in the variance explained. The elbow is the point where the cumulative variance explained flattens out after rising steeply, hence the name of the method [56]. The variance can be qualified with WCSS, which is:
Figure 76: The elbow method applied to the stock data. Source: [56]
퐶푛 푑푚 2 푊퐶푆푆 = ∑( ∑ 푑푖푠푡푎푛푐푒(푑푖, 퐶푘) ) (22)
퐶푘 푑푖 푖푛 퐶푖
Where 퐶 is the cluster centroids and 푑 is the data point in each cluster. This method optimizes the number and position of OC/SWOC required on the field in relation to TSE. However, it must be noted that the final position of OC/SWOC will depend on spatial restrictions – due to lack of space the final position may deviate from the originally calculated position. The process of calculating the optimal location of OCs/SWOCs is presented in Figure 77.
Figure 77: Calculation of optimal location for OC/SWOC. Own edit
3.5. Inflation According to Farr and Faber [47] inflation is the phenomenon that explains the change in purchasing power of a given currency over time. In general, healthy economies have an inflation rate of about 2%, but to define it more accurately is a very difficult task. This is also 3.Methodology | 60
reflected on the level of prices, which tend to increase overtime and therefore must be taken into consideration. To that extend, the 2% figure can be used for a 10-year period. Therefore, the problem of calculating the future value given a present value can be tackled with simple interest formula:
퐹 = 푃(1 + 푛푖) (23)
Where:
푃 initial amount
퐹 Future value
푛 Number of years
푖 Interest rate/inflation level
3.6. Estimating the LCC model of an OC/SWOC installation – Generic model Having established the methods which establish the signalling equipment on the field, and outline the surroundings of the Björbo installation, the next step is to formulate a generalized LCC model for Björbo installation with SWOC and compare it with the same installation with typical OC. This step will unfold around not only about creating a generic LCC model, but also to discuss and develop sub-models, which are very important to determine the overall cost reliably. To be able to construct an LCC model, cost data related to different parts of OC/SWOC were used, as well as economic data related to cabling, civil works as well as maintenance costs. Data related to OC/SWOC were provided by ALSTOM, but since signalling equipment costs are confidential, they cannot be displayed within the master thesis.
When one considers a product such as SWOC, it must be done in a system framework, in the sense that this product does not affect the cost by itself, but rather does so by alternating the structure of an interlocking system as well as the connections between the different parts. Furthermore, parts of LCC are also affected by new parts entering the cost estimation or by parts being removed as a direct implementation of the SWOC concept. In the case of a station such as Björbo and considering the effect of SWOC, a generic LCC model which covers the interlocking system from the interlocking computer all the way down to TSE (without including it) can be expressed as:
퐿퐶퐶 = 퐶푑푒푠푖푔푛 + 퐶퐴푃퐸푋 + 푂푃퐸푋 + 퐶푑푖푠푝표푠푎푙 (24)
퐶푑푒푠푖푔푛 includes the design cost of the installation, as well as the cost of internal and external consultants. 퐶퐴푃퐸푋 includes all the capital expenses associated with the project during the construction phase. 푂푃퐸푋 includes all the operational expenses associated with the project during its lifetime. Finally, 퐶푑푖푠푝표푠푎푙 includes costs related to disposal of the system or parts of it. 퐶푑푖푠푝표푠푎푙 can be considered as a separate topic and can therefore be excluded from the 61 | 3.Methodology
analysis. This is since as a process, disposal requires its own analysis, including cost analysis which implies a workload way beyond the scope of this master thesis. Furthermore, 퐶푑푒푠푖푔푛 does not affect the outcome significantly since the same station under different conditions is being considered. The generic model for both OC and SWOC installations can therefore take the following form:
퐿퐶퐶 = 퐶퐴푃퐸푋 + 푂푃퐸푋 (25)
3.6.1. Estimation of installation design cost (푪풅풆풔풊품풏) The design cost includes costs for internal or external consultants, who are responsible for designing the project. For Västerdalsbanan, this cost is given as a lump sum without compartmentalization per station. Since, design cost does not play a crucial role, it will not be considered for the calculations.
3.6.2. Estimation of CAPEX cost CAPEX cost can be defined as the sum of one-time costs related to the construction of the installation. Covering both typical OC and SWOC installations, CAPEX can be expressed as:
퐶퐴푃퐸푋 = 퐶퐸푀푃 + 퐶퐶푊 + 퐶퐶퐼 + 퐶퐸푆푦푆 + 퐶퐸푆푆 (26)
Where:
퐶퐸푀푃 Cost of equipment and material procurement
퐶퐶푊 Cost of civil works
퐶퐶퐼 Cost of construction and installation
퐶퐸푆푦푆 Cost of energy supply system
퐶퐸푆푆 Cost of energy storage
Alternatively, CAPEX can be divided by installation sections, that is the distance between interlocking and OC/SWOC, the OC/SWOC itself and distances between OC/SWOC and TSE. Here the former method is implemented.
3.6.2.1. Cost of equipment and material procurement (푪푬푴푷)
퐶퐸푀푃 cost includes the following parameters:
− Cost of OC/SWOC units − Cost of fiber optics (signal cables between interlocking and OC) − Cost of copper cables
In the case of an installation with typical OC, the sub-model would be as follows: 3.Methodology | 62
푛 ( ) ( ) 퐶퐸푀푃 = ∑ 퐶푂퐶푖 + 푁퐹푂 × 퐶퐹푂 × 퐿퐹푂 + 푁퐶푂 × 퐶퐶푂 × 퐿퐶푂 (27) 푖=1 Where:
푛 Sum of the costs of OC units to be procured
∑ 퐶푂퐶푖 푖=1
푁퐹푂, 퐶퐹푂, 퐿퐹푂 Number of fiber optics between interlocking and OC, Cost of fiber optics per meter and Length of fiber optics
푁퐶푂, 퐶퐶푂, 퐿퐶푂 Number of copper cables between interlocking, OC and TSE, Cost of Copper cable per meter and length of Copper cables
In the same fashion, the sub-model for the equipment and material in an installation with SWOC would be:
푛 ( ) 퐶퐸푀푃 = ∑ 퐶푆푊푂퐶푖 + 푁퐶푂 × 퐶퐶푂 × 퐿퐶푂 (28) 푖=1 Where:
푛 Sum of the costs of SWOC units to be procured
∑ 퐶푆푊푂퐶푖 푖=1
푁퐶푂, 퐶퐶푂, 퐿퐶푂 Number of copper cables between SWOC and TSE, Cost of Copper cable per meter and length of copper cables
3.6.2.2. Cost of OC vs SWOC (푪푶푪풊 vs 푪푺푾푶푪풊) In terms of cost structure, a SWOC does not differ a lot from a typical OCS system, however there are some important differences:
1. Antennas: A SWOC communicates wirelessly with the central interlocking/TCC as well as with other SWOCs, which means that every SWOC must have 2 bi-directional antennas installed: one for communication between different SWOCs and another for communication with the central interlocking/TCC, which incurs an additional cost for the 2 antennas for every SWOC unit. 2. Local interlocking logic: VAC boards. In short, VAC boards are the embodiment of localized interlocking in a SWOC installation. These boards are installed only on a master SWOC responsible for a station; therefore the associated cost is related only with the master SWOC. 63 | 3.Methodology
Apart from these differences, the cost structure of an OC/SWOC starts with a basic configuration, which includes the OCS cabinet and the building housing it and form the core cost. After, the cost of an OC/SWOC goes up and this depends on several factors:
− Number of TSE equipment connected to the OC/SWOC. It is obvious that additional TSE requires addition OC/SWOC racks and equipment in general. − Building size. The addition or extra building size for accommodating a UPS unit with batteries affects the total cost of an OC/SWOC − Plugging-in point machines to OC/SWOC. Power-wise and equipment-wise, point machines require more power supply and equipment to be accommodated by the OC/SWOC. − Extra functionalities: A typical example applied to Swedish rail network owned by TRV would be the Point Position Detector (TKK), which is a condition that requires additional equipment installed within OC/SWOC.
To draw conclusions regarding the variation of cost, a cost model in the form of a flowchart was constructed to depict the process of cost estimation for an OC. Furthermore, a synthetic database for the relation between total cost and different parameters of an OC/SWOC was constructed and the relationship was modelled with the help of linear regression. The detailed flowchart of the modelling process for OC and SWOC alike are presented on Figure 78 and on Figure 79. These are simplified models, adjusted to Björbo case and ignore many more parts that an OC or SWOC contain. This would be the whole cost of telecommunication equipment, cost of different PSU’s (different objects require different PSU) and other smaller parts of an OCS/ SWOC. Since cost details for different parts of an OC/SWOC are corporate information subjected to bidding, they will not be presented here. However, results are presented in index prices, which is sufficient to draw conclusions regarding the LCC of a SWOC solution in general.
3.Methodology | 64
Figure 78: OC model. Own edit, based on data from [65]
Figure 79: SWOC model. Own edit, based on data from [65]
65 | 3.Methodology
3.6.2.3. Cost of Fiber optics 푪푭푶 vs cost of copper cables 푪푪푶 In the case of a signalling system there are 2 types of cables used: Copper cables and optic fibers. The cost of optic fibers depends not only on the price per meter for an optic fiber but also on their length and number. There are many different types of fiber optic cables, as well as the cable structure. One of their main differences is how many strands (optic fibers) they contain. According to price comparison advisor [57], the cost per linear Figure 80: A 10-strand Fibre optic cable. Source: foot ranges between $1 and $6 per foot, https://www.nai-group.com/optical-fiber-technology-how- including installation, while a 24-strand it-works/ single-mode fiber optic cable costs between $2 and $3. These prices were applicable 10 years ago. Therefore, they must be brought to the present, which can be done by considering the time length as well as the inflation. Here, a value of $1.5 is assumed for a 4-strand cable, since economy scales exist when one buys cables in bulk.
Considering the inflation, it was calculated that in 2021, a 4-strand optic fiber cable would cost $1.8 per foot. Since 1 ft equals 0.3048 m, the cost of a 4-strand optic fiber per meter would be $6. Finally, using the current exchange ratio between USD and SEK (1:8.27), the cost per meter expressed in SEK is 49.62 SEK/m. It must be noted that no significant power transmission losses are assumed.
Just like with FO, cables can vary in size, number, and dimensions. Their dimensions are selected based on the required power for an installation, the voltage drops along their length, their material, as well as their max current capacity and the type of current (DC, 1 phase AC, 3 phase AC). All these factors affect the structure and cost for cabling. In the case of OC/SWOC installation, the interest in cables lies with cables connecting the local grid/distribution areas with the OC/SWOC, cables connecting OC/SWOC with TSE and cables connecting SWOC with the local power supply.
Since the line in Björbo is not electrified, the signalling equipment is powered by the local grid. The specifications demand an appropriate cable for power supply. Hence, for supplying appropriate power levels, a three-phase, 3-core aluminium solid conductor,25 mm 0.6/1 kV cable is assumed both between local grid and OC, as well as between SWOC and local power supply. Internationally, 0.6/1 kV is a common low voltage rating, where 1 kV is phase-to- phase (U) and 0.6 kV is phase-to-ground voltage (푈0). For connections between OC/SWOC and TSE, 48 X 1.5 mm single core stranded copper cables are adopted, just like in the cable plan for the station.
The determination of costs for copper and aluminium cables is also difficult, since cable costs are confidential information. To solve this problem, a similar approach as with fiber optics 3.Methodology | 66
was adopted. An earlier list from 2017, published by Nexans New Zealand [58] states prices for different cable categories. For 0.6/1KV cable CU NSCRN XL 4X 25^ 3.2 was chosen. Since it is made from copper while the assumed one is from aluminium, its price per 100 m was halved and converted to price per meter. Finally, by taking the inflation into account, the 2021 price was converted to SEK, yielding 1810 SEK/m. Similar approach was taken for CU TPS 1X1.5 BK WH 1HM 1.5 mm copper cable, yielding 579.59 SEK/m.
3.6.2.4. Cost of civil works (푪푪푾) This cost category includes all civil works associated with the infrastructure necessary for deployment of cables (power and signal cables), as well as of OC/SWOC technical building/cabinets. The corresponding equation for a typical OCS based system can be expressed as:
푛 푛 ( ) 퐶퐶푊 = ∑ 퐷푖푗 × 퐴퐸푋푇퐶퐸푋 + 퐶퐷 + 푉퐸푀푇퐶퐸푀 + ∑ 푉퐹푂퐶푖 × 퐶퐸푋 + 4푁푂퐶 퐶퐶푃 (29) 푖=1,푗=1 푖=1
Where:
푛 Sum of distances between interlocking, OCs, TSE and ∑ 퐷 푖푗 substation 푖=1,푗=1
Cross-section of excavation for trench which 퐴 , 퐶 퐸푋푇 퐸푋 accommodates the cable duct, cost of excavation
퐶퐷 Cost of cable duct per meter
Volume of embankment for trench which 푉 , 퐶 퐸푀푇 퐸푀 accommodates the cable duct, cost of embankment
푛 Total Volume of foundations of an OC, Number of ∑ 푉 , 푁 , 퐶 퐹푂퐶푖 푂퐶 퐶푃 OC, Cost of Cement plinth for foundations 푖=1
The sum of distances between interlocking, OCs, TSE and substation can be written as:
푛 푛 푛 푛 퐷 + + 퐷 + 퐷 ∑ 퐷푖푗 = 퐼−푆퐸 ∑ 퐷푂퐶푖−푂퐶푖+1 + 퐷푆퐸−푂퐶1 ∑ 푂퐶푖−푇푆퐸푗 ∑ 푂퐶푖−퐶푆 (30) 푖=1,푗=1 푖,푗=1 푖=1 푖=1
Where:
Distance between interlocking and station entrance. 퐷퐼−푆퐸 Estimated by following the track from interlocking all the way to station entrance. 67 | 3.Methodology
푛 Sum of distances between interconnected object controllers and the distance between 1st OC and
∑ 퐷푂퐶푖−푂퐶푖+1 + 퐷푆퐸−푂퐶1 푖,푗=1 OC1 OCi SE
Sum of distances between each Object controller and 푛 corresponding TSE connected to them ∑ 퐷푂퐶푖−푇푆퐸푗 푖=1
Sum of distances between Object controllers connected directly to Converter station and converter
푛 station. Depends on power architecture and redundancy. ∑ 퐷푂퐶푖−퐶푆 푖=1
(a) (b)
The cross-section of excavation for trench which accommodates the cable duct, can be expressed as:
퐴퐸푋푇 = 푊퐸푋푇퐷퐸푋푇 (31)
Where:
푊퐸푋푇 Width of the excavated trench
퐷퐸푋푇 Depth of the excavated trench
The width and depth of the trench depends on the type of cable duct or cable installation technique. The Volume of embankment for the trench which accommodates the cable duct can be defined as:
푉퐸푀푇 = 퐿퐸푀푇푊퐸푀푇퐷퐸푀푇 (32)
Where:
퐿퐸푀푇 Length of embankment of trench
푊퐸푀푇 Width of embankment of trench
퐷퐸푋푇 Depth of the excavated trench
Here it must be noted that 푉퐸푀푇 ≠ 0 only if plastic pipe ducts are used for cable protection or the cables are directly buried underground.
Finally, the volume of foundations of an OC can be defined as: 3.Methodology | 68
푉퐹푂퐶푖 = 4 × 퐴퐶푃 × 퐷퐸푋 (33)
Where:
Cross section of cement plinth used in 퐴 퐶푃 foundations
Depth of the excavated foundation for a 퐷 퐸푋 cement plinth
This procedure ensures as accurate estimation of civil works as possible. However, one must be aware that there are some crucial elements considering the cost calculations.
1. The first is that that the distances defined by the formula refer to sections where cables must be laid. There are sections, where signal cables between station and interlocking (fiber optics) and between OCs/SWOCs and substation/local power source (0.6/1 kV cable) may be overlapping, so calculations must be adjusted accordingly if possible. Here, overlapping is not considered. 2. The second point is related to the cost of excavations and embankments as well as their necessity, which relates to the form of cable installation, mainly the used od concrete/plastic cable ducts or not. If in a project, direct cable burial or plastic pipe for cable casing are selected, then the cost of embankment must also be included, while in case of concrete cable ducts it does not have to. Furthermore, some parts may require embankments, others not. Here embankments are not assumed. 3. The cost of excavation, just as the cost of embankments is not easy to be estimated as it is a bidding item and therefore a confidential information. To that end, estimations regarding the cost of excavation and embankments were done based on numbers provided by C.T. Dick [59]. Since the numbers were referring to cubic yards and were 10 years old, they were converted to cubic meters and were brought to present with the process described before. As a result, excavation per 푚3would cost 51.8 푆퐸퐾/푚3, while embankment 64.75 푆퐸퐾/푚3. 4. The cost of cable duct depends on factors such as type of construction material, as well as its dimensions. The types of linear cable ducts Trafikverket [33] specifies for line sections are of reinforced concrete type, with type 350 and 535 being good examples. Although clearly, they have different price, it is assumed that for type 350 (2250 × 350 × 300 푚푚) a ballpark price would be 162410 SEK/m or 3654 SEK/piece. 5. The foundations of OCs/SWOCs are composed of 4 plinths. Plinth foundations are the simplest and are suitable for small cabins, like OC’s and SWOCs. The value of a plinth can be estimated around 500 SEK/piece but in general depends on size and specifications.
10 C.T. Dick estimates the price on the basis of 12-24’’ culverts used in US railway engineering practice, since they have similar dimensions and construction material. 69 | 3.Methodology
3.6.3. Cost of construction and installation (푪푪푰) The cost of construction and installation of a signalling system (not including the material procurement cost) refers to the cost of material, personnel, equipment, and procedures used on site for constructing relevant infrastructure and installing relevant equipment. Furthermore, it constitutes a measure of “effort” put by the working crew to construct infrastructure. When one considers the construction materials on site for cable ducts, this could include either nails, screws or more concrete for connecting cable duct sections and not the cost of material procurement discussed earlier.
Cost of construction and installation cab be expressed as:
퐶퐶퐼 = 퐶푀 + 퐶푀푇 + 퐶푃 + 퐶퐸 + 퐶푂퐶퐼 + 퐶푆퐶퐼 + 퐶푃퐶퐼 (34)
Where:
Cost of mobilization. Includes proceedings 퐶 푀 of setting up site
퐶푀푇 Cost of material transport
Cost of personnel. Includes but not limited to 퐶 푃 wages and related extra costs.
Cost of equipment. Includes hand equipment, 퐶 퐸 road, and rail construction vehicles
Cost of OC/SWOC construction and 퐶 푂퐶퐶퐼 installation.
퐶푆퐶퐼 Cost of Signal cable installation
퐶푃퐶퐼 Cost of power cable installation
Costs during construction and installation can include:
− Mobilization cost, which includes but is not restricted to the site setting up, accumulation of equipment and installation of facilities for personnel. Typically expressed as lump sum or as a percentage. − Cost of material transportation on site. Depends on distance between material storage facility and site, the means available for transporting material etc. − Cost of personnel and equipment. This is directly related with the size, nature, and complexity of project, which will require adequate and suitable manpower as well as equipment. The problem of estimating this cost becomes even more difficult if one 3.Methodology | 70
considers national/regional regulations and the fact that the time plan of the project can also influence it. For example, for project planning reasons, more resources cab be poured into construction to speed up the process, thus affecting the cost. − Cost of construction and installation of OC/SWOC building and relevant equipment. Equipment and technicians are used to assemble the OC/SWOC building and install the equipment inside/on the field, such as OC cabinets, UPS and battery supplies etc. − Cost of Signal cables installation (fiber optics). This involves laying down the cables and create connection between them and interfacing devices. − Cost of power cables installation. Just like in the case of fiber optics, power cables must be installed and plugged to OCs/SWOCs, as well as to the power source, which can be a local transformer/substation or a local power source (e.g., array of PV panels).
Construction and installation costs are very difficult to be calculated as they are project specific, they are usually confidential information, and their disaggregation varies from project to project. Furthermore, many authors when referring to construction and installation they mix it with material procurement, which makes any comparisons even more challenging. In this case, since ERTMS-R project was implemented in Västerdalsbanan, which includes several stations, a total construction and installation cost was given by ALSTOM. Due to the sufficient level of data disaggregation and since this is not a crucial parameter for an intra- station analysis, this cost will not be included in the calculations and therefore is excluded from the analysis.
3.6.4. Cost of Energy Storage and energy supply system ( 푪푬푺풚푺 and 푪푬푺푺) From a cost perspective, the key, when examining both OCS and SWOC power supply systems, especially when costs of different solutions are considered, is to relate the required power/energy with the cost of the solution. In the case of a typical OCS, the only cost considered is the cost of power cable between OC and the converter station. On the other hand, for a SWOC, since it is powered by a local source, the power requirements must be defined based on signalling objects power requirements and energy consumption, including TSE and SWOC consumption as well as the power losses and power factors available for each part of the system.
The required power will define in its turn the dimensions and therefore the cost of the local power supply. This method of power requirements estimation is based on active rather than standby power, which is significantly bigger. Furthermore, the basic principle is the fact that the sum of active power required for all devices plus power factors and energy losses must be covered by the local power supply system, even when system utilizes the energy stored.
This principle is described on Figure 81. The modelling process of 퐸푆푦푆 and 퐸푆푆 based on power requirements is presented on Figure 82.
The estimated CAPEX of a hybrid standalone system that can be considered as a cost calculation by itself, includes but is not restricted to: 71 | 3.Methodology
− Site mobilization − Earthworks (for solar panels depends on foundations and their configuration) − Cost of equipment material and personnel − Cost of material procurement. This includes the number of solar panels, wind turbines and battery packs, as well as cables and other electrical infrastructure (e.g., inverters). − Cost of construction and installation. Here the cost will differentiate from a typical installation, as this is a small-scale installation
Figure 81: Power dimensioning principle in case of renewable and alternative energy sources for SWOC. Own edit
Typically, the cost structure of a standalone hybrid power system would be identical to that of an OC/SWOC solution (planning cost, CAPEX and OPEX). Furthermore, it depends strongly on the power requirements of the installation, the choices regarding PV panels, wind turbines and battery pack capabilities, power safety and redundancy, the mix of energy sources11 as well as their efficiency. It is also fair to note that depending on the country, wind turbines or solar panel may be a subject of extra costs coming from environmental permitting and mitigation of side effects (e.g., environmental impact on landscape, nose, etc.).
In terms of power demand for every system object, the following are assumed for TSE and OC/SWOC, based on information provided by ALSTOM, as well as data from [38], [45]:
− Radio communication: different types of radio have different power requirements. For example, the most power - demanding radio mode is TETRA, which requires 130W (when active). PSU type and its output for radio application is also important. To that extend, an active power of 120 W can be assumed. Standby mode requires considerably less power (1W) − Point machine: a typical 3 phase point machine of 230V requires 2.5 KW of active power to be operated on average. However, this is required for short periods of time: point
11 A standalone system like this can incorporate more technologies such as fuel cells, supercapacitors, flywheels etc. which are out of the scope. 3.Methodology | 72
machines are operated for 15 sec or less on average. Standby mode requires considerably less power (5W). − A level crossing system requires approximately 2.5 KW on active mode to power up its whole system. Its power requirements depend on the size, type, and complexity of level crossing: the more equipment a level crossing has, the more power is required. Standby mode requires less power (317.5 W), but still considerably more than other devices in the system. − UPS 1 or 3-phase and batteries. A 3 phase UPS requires 10 kVA, while a 1-phase 2kVA. Furthermore, a 300W A/C system or 2000 W cab be added for colling. − Same OC/SWOC: The power required for the operation of an OC/SWOC as a “box” can be estimated to 3 kW. − The power factor (PF) can be estimated at approximately 0.95.
Figure 82: Cost calculation of energy supply and energy Storage system based on power requirements. Own edit.
In general, it can be assumed that for any device or system that is part of OCS/SWOC the following apply:
max(푃푖,푖푑푙푒, 푃푖,푎푐푡푖푣푒) 푃푖 (35) 푃푖,푖푛 = 푃퐹푑푒푣푖푐푒
Where:
푃푖,푖푛 Power required for an object
Maximum value between idle or active max(푃푖,푖푑푙푒, 푃푖,푎푐푡푖푣푒) 푃푖 power for device 푖 73 | 3.Methodology
푃퐹푑푒푣푖푐푒 Power factor of the device
Therefore, the dimensioning of the system of the basis of power must be done in such a way that the following apply:
푛 푛
푃퐸푆푢푆 ≥ ∑ 푃푖,푖푛 + ∑ 푃푖푗,푙표푠푠 (36) 푖=1 푖=1,푗=1
푛 푛
푃퐸푆푆 ≥ ∑ 푃푖,푖푛 + ∑ 푃푖푗,푙표푠푠 (37) 푖=1 푖=1,푗=1
Where:
푃퐸푆푢푆 Power delivered by energy Supply system
푃퐸푆푆 Power delivered by energy storage system
푛 Sum of power required for each object in the ∑ 푃 푖,푖푛 system under study (OC/SWOC/TSE) 푖=1
푛 Sum of the power gets lost in cabling ∑ 푃 푖푗,푙표푠푠 between system objects (OC/SWOC/TSE) 푖=1,,푗=1
The estimation based on power is straightforward, but it overestimates the needs for power since all the equipment on the field have or will have a standby mode in the future (particularly in the case of SWOC) which does not require that much power. Furthermore, another disadvantage of this method is that it cannot consider the effect of traffic, as it affects energy consumption, rather than power requirement. To illustrate that point, if one considers a point machine, on active mode (when motor works to pull/push switch blades) it requires 3 kW of power, but in standby mode maybe few watts, which means that 3kW are only needed for maybe a few minutes every day. The energy consumption of an object is tightly related not only to the standby and active power a system object requires, but also to the level of traffic. Therefore, the energy required to power up a signalling object during a day, considering the traffic (푁푡) will be equal to:
퐸푖 = 푃푖,푖푛,푖푑푙푒 × (24 − 푡푖,푎푐푡푖푣푒) + (푃푖,푖푛,푎푐푡푖푣푒 × 푡푖,푎푐푡푖푣푒)푁푡 (38)
Where:
Idle power required for the object in 푃 푖,푖푛 푖푑푙푒 including power factor 3.Methodology | 74
Active power required for the object 푃 푖,푖푛,푎푐푡푖푣푒 including power factor
Time pe day an object is on active mode in 푡 푖,푎푐푡푖푣푒 hours
푁푡 Number of trains per day using the object
The total energy required by the system during a day can be expressed as:
푛 푛
퐸푡표푡푎푙 = ∑ 퐸푖 + ∑ 퐸푖푗,푙표푠푠 (39) 푖=1 푖=1,푗=1
Where:
푛 Sum of the energy consumed by the ∑ 퐸 푖 signalling objects (TSE,SWOC,OC) 푖=1 푛 Energy losses occurring through cables ∑ 퐸푖푗,푙표푠푠 between objects and between objects and 푖=1,푗=1 power supply
This method is much more accurate for energy system dimensioning, but also requires more knowledge about voltages and currents created within the system. Here it was decided to model the 퐸푆푦푆 and 퐸푆푆 by using the energy approach. That was decided since the study of the impact of traffic in an important parameter of the study. For that, current values by Mihael Zitnik were provided, while others were adopted from [38]. The LCC modeling just as the modelling of the 퐸푆푦푆 and 퐸푆푆 were performed on MATLAB, where resistance and current values were used to create matrices depicting the energy losses of cables and the energy consumption profiles of signaling objects, not only as a function for active and standby power, but also as a function of traffic. Combined, they create an estimation of a daily energy consumption of the installation. The dimensioning of the energy storage system was more straightforward. There, 6 hours of autonomy were assumed with TESLA Powerwall 2 batteries and based on the maximum energy in Wh for each battery, the number of batteries and the energy that they should store were calculated.
Having dimensioned the system, it is possible to calculate the cost of energy supply system
(퐸푆푦푆) and energy storage system (퐸푆푆). Regarding the actual cost of the powering infrastructure, it is assumed that for a standalone hybrid system, the CAPEX of the facility will follow the wind farm cost structure presented on Table 5, by starting the calculations from energy production and storage equipment. 75 | 3.Methodology
Table 5: Typical Breakdown of costs for a 10 MW wind farm on an upland UK site. Source [41]
Regarding equipment procurement, a small wind turbine can cost roughly between $3,000 and $5,000 per kW [60] (33,243 sek/kW on average), while solar PV panels cost about $2.5/W [39] or $ 2,500/kW (20,777 sek/kW). Furthermore, there are many different energy storage solutions – batteries made of different material, with different capacities and energy storage capabilities. One of the most effective and commercial batteries is Tesla Powerwall 2, with 5 kW power and 13.5 kWh stored energy [61]. This is the only type that will be considered for the project. It is estimated that the cost of two tesla batteries cost 129,519 sek.
The cost estimation of the SHS is done on the basis of kW rather on the basis of Wh. To do the dimensioning, hours of energy production are assumed for Björbo installation (solar power) or energy production for a specific wind turbine under specific wind speed at Björbo is taken directly. Figure 83: Tesla Powerwall 2 integrated AC battery system for residential or light commercial use. The cost of equipment procurement for energy storage and Dimensions: 1150 mm x 755 mm x supply system can be estimated as: 147 mm. 5 KW, 13.5 kWh. Source: [61] 푛
퐶퐸푆푦푠 = ∑ 푃푖푛,푖퐶푘푊푖 (40) 퐸푆푦푆,푖=1
푛
퐶퐸푆푆 = ∑ 푃푖퐶푘푊푖 (41)
퐸푆푆,푖=1
Where:
퐶퐸푆푦푠 Cost of energy supply system
퐶퐸푆푆 Cost of energy storage system
푃푖푛,푖 Power required for an object/power
푃푖 Power of a battery/energy storage device
Cost of kW for a specific energy 퐶 푘푊푖 source/storage device 3.Methodology | 76
The final CAPEX of the whole standalone hybrid system, based on Table 5, can be calculated as:
퐶퐿퐸푃푆 = 퐶퐸푆푦푠 + 퐶퐸푆푆 + 퐶퐶푊퐿퐸푃푆 + 퐶퐸퐸 + 퐶퐸퐶 + 퐶푃퐷푀 (42)
Where:
Cost of local energy production and storage 퐶 퐿퐸푃푆 system
퐶퐸푆푦푠 Cost of energy supply system
퐶퐸푆푆 Cost of energy storage system
Cost of civil works related to local energy 퐶 퐶푊퐿퐸푃푆 production and storage system
Cost of relevant electrical infrastructure 퐶 퐸퐸 (cables, inverters, etc.)
퐶퐸퐶 Cost of electrical connections
Cost of project development and 퐶 푃퐷푀 management for the local energy installation
A word must be said regarding the underlying assumptions of power capabilities of energy storage and supply systems, with a focus on solar, wind and battery storage technologies, which affect the cost of the standalone hybrid energy storage and production system solution, as well as the space they occupy. Regarding PV efficiency, it was discussed before that the
퐺푆 value depends on the region or Sweden and is further reduced by PV’s efficiency. For 푚2 Sweden, a value of 200 푊/푚2 is reasonable to be assumed, which means that 5 are 퐾푤 required. However, with the current technological developments, PV efficiency can go all the way up to 40%. Solar panels produce this kind of energy only during the day and only when the there are no clouds. Their power capabilities are also affected by the angle towards the sun. For wind turbines, their rated power is attained only when wind blows with an optimal speed. Therefore, optimal conditions are assumed. This means that a small wind turbine with 5 kW power is assumed to produce that power all the time. For wind turbines, energy efficiency also varies (30-40%), but most importantly the wind does not have the same speed for 24 hours. Finally, battery systems have different capacities, which is affected by internal battery characteristics but also by the amount of current that is drawn from the battery- the more current, the less the capacity.
Finally, all the remarks above define the space required by the installation. As it stated before, 푚2 for solar panels, 5 are required, whereas for wind turbines a spacing of 7퐷 from back-to- 퐾푤 77 | 3.Methodology
back by 4퐷 from side to side, where 퐷 is the rotor diameter, can be assumed. Finally, batteries can be stored within filed cabinets which can provide them with protection and stable operational temperature. The dimensions of the cabinet must be enough to accommodate batteries and the appropriate electronics.
3.6.5. Estimation of OPEX cost The estimation of OPEX is also a difficult task, not only because the bidding prices are confidential, but also because the form, duration, and frequency of maintenance of an asset depends on the maintenance contract details.
The OPEX cost can be categorized into the following:
1. Maintenance Costs. Maintenance can be related to following items: a. Maintenance of OC/SWOC. For OCS, maintenance does not have to be intensive. An inspection is conducted once per year to determine the status of electronics. Therefore, unless circuitry is damaged and requires repair, maintenance is restricted to inspection b. Maintenance of Power and communication cables. Usually, if cables are dimensioned and chosen properly, they require zero maintenance (perhaps only field inspections). However, cables can be damage by excessive current and optic fibers by bending or other mechanical means. Then they will probably require changing. c. Maintenance of civil work: cable ducts and local energy supply. These structural elements must also be inspected and repaired. This could possibly include cracks or other damage. d. Preventive and corrective maintenance e. Supply chain and spare parts cost. These costs have to do with the cost/availability of spare parts and how fast damaged parts are being replaced on the field. f. Maintenance of local energy source. This cost includes the cost of maintaining PV panels, wind turbines and battery packs on the field. 2. Energy consumption and price. For a standalone hybrid system, the energy production takes place on site, so theoretically it costs nothing. However, supplying signalling equipment from the grid is subjected to pricing. 3. Vandalism and sabotage. These operational costs fall under the subcategory of unexpected costs. Cable theft (particularly copper cables) can require extensive repairs. Another externality of a cable theft is the possible halt of traffic, and the lost of productivity in monetary terms, which is much more difficult to be estimated.
More generic influences include the traffic density, as well as the life cycle of the project. For a SWOC configuration, traffic density has an impact from the standpoint of energy consumption: the more frequent a service is, the more power and energy is required (e.g., point machine activation, radio communications, signal illumination and track circuits etc.,
(see 3.6.4. Cost of Energy Storage and energy supply system ( 푪푬푺풚푺 and 푪푬푺푺)) On the other 3.Methodology | 78
hand, life cycle is a subjective term but when signalling installations are involved, it refers to the operational lifetime. Typically, railway equipment has a life cycle of 30 years, if only operational period is considered.
3.6.5.1. Maintenance cost of cables Since information are scarce and not detailed, the cost of cable maintenance will be an approximation. According to Profillidis [36], the infrastructure maintenance costs comprise the following:
− Maintenance and renewal of tracks and subgrade − maintenance of electrification, signaling and telecommunications facilities and substations, − maintenance of tunnels and bridges − maintenance of platforms (in stations).
A maintenance cost per year of 47,000 €/km of track was reported for France and a cost of 60,000 €/km was reported for the Netherlands (monetary values for the year 2008). This cost is allocated as follows to the various maintenance components:
− 65% for track and platforms − 30% for electrification, signaling, telecommunications and substations − 5% for bridges and tunnels.
A value of €50,000/km can be assumed for maintenance and by taking into account the inflation, the conversion to SEK, as well as the fact that the line is under ERTMS-R regime (taking 1/3 of 30% percentage), the annual maintenance per km is SEK 63,441/km for cabling.
3.6.5.2. Maintenance cost of local power supply The annual maintenance of a PV array can be assumed to be 2% of the capital expense value. It is assumed that the same value applies for wind power and battery parts as well.
79 | 4. Results
4. Results In this chapter, the results of the LCC calculation process of OC vs SWOC installations are being presented and discussed. The discussion is based on 6 different scenarios that were commissioned on the basis of the initial OC installation (scenario (a)) at Björbo in order to evaluate the LCC of SWOC installations in comparison to conventional ones by using the LCC model described in the methodology section. These scenarios are depicted in Figure 84.
Figure 84: Scenarios of signalling equipment created to test the LCC model. Own edit 4. Results | 80
4.1. LCC of SWOC VS OC installation – scenarios (a) VS (b) These scenarios are the most elemental ones: scenario (a) represents the base or nominal scenario, where a conventional system with one OC exists, connected to the power grid. It is compared in terms of costs with scenario (b), where OC is replaced with a master SWOC, powered by a local SHS and the position of SWOC was optimized in relation to TSE. The results are presented in Figure 85.
Figure 85: LCC comparison between 1 OC and 1 SWOC installation (index values). Own edit
It is clear from the data that the SWOC option has a dramatic impact on the LCC of an installation. In the case of Björbo station, which is controlled by one OC, and which is located quite far away from the nearest interlocking computer (Borlänge), a SWOC solution reduces the CAPEX by 75%, the OPEX by 97% and the total cost by 85%. These savings are primarily achieved by eliminating the FO connection between Borlänge and Björbo, as well as eliminating the cable duct and associated civil works. Both parameters are reduced by 98%. Another remark is that in spite the fact that the SHS is quite expensive to be developed, its cost is overshadowed by the reduction of cabling and civil works costs between the interlocking and station. In practice, since the data is not fully accurate and maintenance costs are based on rough estimations, it is more accurate to assume a reduction of the LCC cost by 75%, which equals the reduction in capital expenses. This is a more realistic approach, since in practice, cables and OCs/SWOCs do not have big need for maintenance, which is usually limited to routine inspections. 81 | 4. Results
4.2. The effect of adding more OCs/SWOCs - scenarios (a) to (f) Another interesting aspect that could be examined is the effect of adding more OCs/SWOCs in order to cover a station area, regardless of the number of TSE. As presented in the methodology section, in order to devise an optimum number of OCs/SWOCs, the K-means algorithm can be implemented. The finding was that for 5 TSE (3 switch point machines, 1 point machine for the derailer, 1 level crossing) 3 OCs/SWOCs was the optimum number.
Figure 86: Effect of number of OCs on cable cost. Index values. Own edit.
Figure 87: Effect of number of SWOCs on cable cost. Index values. Own edit 4. Results | 82
Starting from the effect of OCs/SWOCs on the cable cost, it is obvious that the strongest impact is observed for cables between OCs/SWOCs and TSE as well as for the total cable cost– the more the OCs or SWOCs, the better the station area coverage and the bigger the reduction in cabling, since OCs/ SWOCs are placed in such a way that they minimize the cabling required. The big number of cables between OCs/SWOCs and TSE also plays an immense role. On the other hand, for all cases, it seems that the addition of more OCs/SWOCs requires more power cables to connect them with the power source and therefore increasing their cost. What is different for both cases is the existence of FO between OCs themselves as well as between the station and interlocking, something that SWOCs solve with radio communication and decentralized logic. This has a significant impact on the cost difference between OC and SWOC solution in terms of cabling and civil works, as the SWOC solution does not require FO between SWOCs as well as between station and interlocking. Overall, for both options, the addition of extra OCs/SWOCs reduces the total cost of cabling and increases the cost for power cables. Furthermore, while the reduction in cabling is the same for both options, the SWOC solution has an overall lower cost due to absence of need for FO. These results are shown on Figure 86 and Figure 87.
Figure 88: Cumulative cost of OCs/SWOCs Vs number of OCs/SWOCs. Index values. Own edit
Naturally, adding more OCs/SWOCs increases the total cost for their acquisition. However, one can argue that adding more SWOCs is slightly more expensive than adding more OCs, as they employ extra equipment, like radio module or VAC boards in case of a master SWOC. This is shown on Figure 88.
Next, the effect of increased number of OCs/SWOCs on civil works cost is being discussed. When excavation is considered, for OC system, its bulk consists of excavation 83 | 4. Results
Figure 89: Excavation Costs vs Number of OCs (up) and Excavation costs vs Number of SWOCs (down). Index values. Own edit being performed between the station and interlocking (roughly 98% of the cost). The rest is related to excavation within station. While the addition of extra OCs reduces the excavation needs between each OC and TSE, it does increase the ones related to excavation between OCs and the station entrance, as well as between the station and the local power source. Overall, the addition of extra OCs increases the overall excavation cost slightly. In comparison to an OC installation, a SWOC installation involves much less excavation costs: 4. Results | 84
around 2% of that required for an OC installation. In fact, for a small station such as Björbo, the addition of extra SWOCs decreases the excavation cost slightly. Furthermore, while the cost of excavation between SWOCs and TSE decreases due to better grouping, the excavation increases for connections between SWOCs and local power supply, just like in the case of OCS. These remarks are presented on Figure 89. The cable duct costs follow the same pattern as the excavation in both cases, although the costs for cable ducts are significantly higher. Finally, the cost of foundations follows a similar relationship with that of OCs/SWOCs, albeit much lower in terms of magnitude than either cable ducts or excavation.
While for OCS, these parameters conclude the CAPEX part, for a SWOC system the cost of the local power source must be added. In general terms, the cost of a local power supply follows a relationship similar to that of cumulative cost of SWOCs in relation to the number of SWOCs (Figure 88) since the cost of a local power supply is directly connected with the power requirements of the installation and the number of TSE does not change (change is only affected by the number of SWOCs). The results regarding the LCC of local power supply are discussed later, while the relationship between number of SWOCs and the cost of local power supply is presented in Figure 90.
Figure 90: Cost of Standalone hybrid system (local power supply) vs number of SWOCs. Index values. Own edit
The increase in the number of OCs/SWOCs affects the cost of maintenance as well. For both OC and SWOC installations, the cable maintenance cost graphs follow the course of the excavation graphs presented on Figure 89, albeit the maintenance cost is much higher than that of excavation. Therefore, they are not presented. Furthermore, the cost of maintenance of local power source follows the cost of the local power supply (being estimated as a percentage of its CAPEX) on Figure 90. 85 | 4. Results
Figure 91: Main LCC categories Vs number of OCs. Index values. Own edit Another topic of comparison between OC and SWOC installations is to compare costs (total LCC, CAPEX and OPEX) in relation to change in the number of OCs/SWOCs in both cases. When the number of OCs increases to 3, for OC installations, a reduction in CAPEX by 20% is achieved, largely by reduction in cable costs (-68%), while operational costs are being stable, due to the fact that maintenance is done per km of cables rather than by considering their number (according to salient modelling assumptions). This achieves a reduction in total LCC by 6.5% by using 2 OCs and almost 9% by having 3 OCs. These remarks can be seen on Figure 91.
In comparison with an OC installation, the addition of SWOCs in a SWOC installation with 1 SWOC results in a reduction of total LCC by 37% when 1 extra SWOC is being added, while a reduction of 50% when 2 SWOCs are added. CAPEX follows a similar trajectory. The reason for this huge reduction stems from the fact that the overall cost of a SWOC installation is lower, while the reduction in cabling is roughly the same as in the OCS case, which means that the reduction in the cabling cost inside the station represents a much bigger portion of the total cost. Therefore, while the cost in terms of percentage is bigger, in absolute numbers it is the same. In contrast, the OPEX increases more than the corresponding OPEX value in an OC installation. This occurs because the maintenance cost increases due to increased dimensions of the SHS. In any case, SWOC is the winner when it comes to cost reductions especially for small installations, when CAPEX and total LCC are considered and when the number of SWOCs increases. There remarks can be seen on Figure 92. 4. Results | 86
Figure 92: Main LCC categories Vs number of SWOCs. Index values. Own edit A final question arises from the examination of the effect of extra OCs/SWOCs on the LCC structure is whether there is a point where there is no benefit in adding an extra OC/SWOC. From the data it seems that with the current cost structure, as long as the gain from saving from capital investment in cables and from maintenance is bigger than the cost of an extra OC/SWOC and in the case of SWOC also from additions to local power source, it is profitable to do so. Following this Figure 93: Factors behind the profitability or non-profitability of the addition of extra OCs/SWOCS. Own edit. logic, it seems that as stations are becoming bigger, this point is more feasible to appear in the case of SWOC. However, this is also a question of technology: Possibly in the future, it will become cheaper to achieve bigger and bigger degrees of system disaggregation, which means that it will be always profitable to add extra OCs/SWOCs. These hypotheses need mode data in order to be tested.
4.3. Main factors affecting the choice of SWOC or OC solution As result of the analysis, and considering the LCC model, the following was established, in relation to the proposed LCC model: 87 | 4. Results
− Design, construction, and installation costs do not play a decisive role to determine LCC of either of these solutions in the case of the same station; knowing these numbers would be required when two stations with totally different layout are compared. However, here the same station with different configurations is being considered, therefore these variables can be excluded from the analysis. − Cable cost and cost of civil works does not play a significant role per se. This is because in any case the unit cost would be the same for either OC or SWOC installation, unless different cables and their numbers are being sued. − The same principle applies for the maintenance costs.
However, from all the factors, several stand out as the main drivers behind determining whether an engineer should consider an OC or SWOC solution, purely on cost grounds. Such factors are not producing results by themselves but in tandem with each other. They are the following:
− Distances: Distances between interlocking, OCs, TSE and grid or between SWOCS, TSE and local power supply play a very important role in determining the costs of cables, associated civil work and maintenance costs. − OCS: Distance between station entrance and interlocking: This is the main difference between OC and SWOC system. In general, data suggest that the bigger the distance is, the more beneficial it is to use SWOC instead of OC. − SWOC: cost of SHS: this is the counterbalance to distance from interlocking to the station for a SWOC system: In general, the higher the energy demands, the more expensive the local power supply is. An expensive local power supply makes the conventional system more attractive. − The effect of rail traffic: Another important factor affecting the balance is the amount of traffic, as it affects the amount of energy required and therefore the cost of the power source.
In the following, these points will be examined numerically.
4.3.1. Distance of interlocking from station and the effect of OCs/SWOCs The distance between the station and the interlocking is important when a conventional system is compared against a SWOC solution, however it should be considered together with traffic conditions and energy demands for a SWOC system. From the data available, the results show that for 1 OC and for very low traffic (8 trains per day) the optimal solution will always be a SWOC installation. However, when the station starts to be optimized in terms of number of OCs/SWOCs and therefore reducing the cabling required inside the station, then a distance from the station emerges where it is actually preferrable to put OC instead of SWOC emerges. This of course providing that when the cabling and the associated infrastructure are installed, the total LCC will be smaller than of SWOC. These remarks are presented in Figure 94. Of course, more experiments and measurements are required to determine this relationship more accurately. Furthermore, for reasons discussed in section 4. Results | 88
4.1. LCC of SWOC VS OC installation – scenarios (a) VS (b), it is better to use CAPEX as a measure of comparison. Here, what drives the relationship is the effect of adding extra OCs/SWOCs to the station configurations (both for OC and SWOC installations) and to gradually increase the distance between station and interlocking thus increasing the cost of OC configuration. By increasing the former, reduction in cabling inside the station occurs and while there is no other significant influence from other parameters in case on an OC installation, a SWOC installation must also consider the capital invested in renewable energy sources, which is getting bigger as the station becomes more energy demanding. As a result, the bigger the station gets with more equipment but also with more cable optimization, for closer distances the scale tips in favour of OC. Eventually for smaller stations and further away from the interlocking, a SWOC becomes preferrable but nonetheless for very small distances between station and interlocking, an OC solution is better. This of course is affected by more parameters, which will be discussed below. The remarks mentioned before are presented on Figure 94.
− Station size − Distance of interlocking from station − Number of OC/SWOC − Cost of local power source
OC SWOC
Figure 94: Installation of OC vs SWOC installation: the effect of distance from interlocking and the station size. Index values. Own edit. 4.3.2. Cost of local power supply and the effect of traffic The cost of local power supply is another part affecting the equilibrium between OC and SWOC solution. The cost of a local power supply depends on many factors, which are subject to a separate investigation. Nonetheless parameters like the traffic density, the required amount of redundancy, the level of autonomy desired and the types of energy sources used for the SHS are several factors affecting the final cost of the local power supply. For example, in case of Björbo, several assumptions were made about the energy system. The first was that regardless the fact that UPS is installed within the OCs/SWOCs, the local power supply will 89 | 4. Results
be dimensioned for 6 hrs. autonomy. Another assumption is that when dimensioning the system, each power source (e.g., wind, solar etc.) must be able to supply the energy required to the system separately. Finally, it also about the type of equipment being chosen. The main finding is that there is a direct relation between number of SWOCs, power demand and cost of a standalone hybrid system, which is presented on graphs of Figure 95.
Figure 95: Relation of energy demand and cost of a standalone hybrid system with the number of SWOCs. Normalized values of cost on the basis of OC cost. Own edit. As explained before, it can be proven, and it is theoretically sound that more SWOCs increase the power consumption and therefore the cost of the local power system. This in turn affects the choice equilibrium in favor of OC solution, especially at close ranges. Unfortunately, with the current data at hand, this cannot be proven, as apart from increases in the number of OCs/SWOCs nothing else changes in the configuration of the station. Therefore, an attempt to compare results would result in a logical error. Nonetheless, there are many ways to show the relationship of equilibrium with increase in energy. One of them is the traffic. The way traffic is affecting the equilibrium is through its volume: more frequent rail services tend to tip the scale in favor of an OC solution, as TSE is utilized more often, thus requiring more 4. Results | 90
power. This can be shown on for the case of a 2 OC/SWOC system where 8 trains/day are compared with 100 trains/day. Of course, the impact is not huge, as the station is very small. This effect is amplified with the energy requirement of objects and with the size of station.
OC SWOC
− Increased traffic − Increased energy consumption − Increased cost of local power supply − Increase of cost in SWOC installation
Figure 96: Effect of increased energy consumption and traffic over the choice between OC and SWOC system
91 | 5. Conclusions and future work
5. Conclusions and future work
5.1. Conclusions This work focused mainly on developing an LCC model for both OC and SWOC installations, as well as on using these models to conduct comparisons between the two systems. However, this work also tried to explore other parameters of the topic as well. This includes the relation between total LCC for either OC or SWOC installations and the signalling system parameters, the process of estimating the total LCC itself, the impact of SWOC on the LCC, as well as when it is profitable to use SWOC instead of a typical OCS.
5.1.1. Signalling system structure and cost It was possible to show that a regional signalling system, and particularly the costs which are generated from its construction and operation are directly related to its form. By starting from the methods of operation a signaling system implements, several aspects were discussed. Some of them were whether CTC system is used or not, as well as the form and characteristics of the interlocking system being implemented. Others were the type of ATP and the technical solutions implemented within it, as well as the type and quantity of TSE. Finally, the extent and characteristics of civil works, as well the way power is provided to the signalling system are parameters were topics of interest. What was shown is that all of them have a direct impact on the form of signalling system and therefore on the total LCC of a system in general. These considerations touch and affect all the subsystems of a signalling system, down to the element (TSE) control level, where an OC must interface specific TSE and the interlocking with specific ways. This parameter of interfacing is a very important cost driver. When it comes to the SWOC solution itself and the ways that such a facility can be powered, alternative energy sources come into the picture. They do incur extra costs, the level of which depends totally on their characteristics, the extend of the facility they are powering as well as the level of redundancy they offer to the installation in terms of power supply. A positive aspect is that currently new energy production alternatives are being researched and commercialized, therefore in the future more options will be available to diversify the power production inventory.
5.1.2. The effect of SWOC concept on the LCC of signaling installations As a concept and product, SWOC is characterized by many innovations which can revolutionize the signalling system structure and affect the incurred costs that come with it. By utilizing wireless communications and decentralized interlocking logic, it can affect and simplify the signalling system structure in ways that were simply not possible before. For example, a SWOC has the possibility to simplify the communication system in terms of hardware: by allowing the direct relay of information to the train wirelessly, it can remove hardware overlays that increase the LCC of signalling systems, while promoting more integrated and safe railway systems. In comparison with a typical OCS, its main impact on LCC was proven to be large. In the case of Björbo station and considering only the results of CAPEX modelling, it was shown to reduce the associated costs by 75%. This makes a good 5. Conclusions and future work | 92
business case for many rural railway lines with low traffic, for which currently there in not enough incentive for utilization and renewal by railway authorities. By implementing a SWOC solution to such lines, it is feasible to create profitable rural passenger services, which can give the railway authorities around Europe the justification they need to renew rural railway lines. This in turn can have important repercussions by revitalizing or bringing railway passenger services to the countryside, something which can promote rural development and population decentralization. By doing so, people will experience much higher accessibility to the countryside and them enough people have credible reasons living there. This can result in a more balanced development on a national level and can help to bring down housing prices in cities. For freight services, SWOC can improve the already achieved economies of scale even further.
5.1.3. The LCC modelling process for signalling installations The modelling process of LCC of either an OC or SWOC system seems to be relatively simple on the surface. However, their estimation is a very complicated process. What was realized from the modelling process first is the need for accurate cost data for all parts of the system involved (e.g., cost of OCs/SWOCs, cost of cabling, cost of civil works, cost of local energy supply etc.). Furthermore, good data related to the existing installation (e.g., maps, technical schematics etc.) are very important for any LCC modelling attempt to be made. The problem here is multidimensional and is affected by the following:
− Accurate cost data regarding different parts of the system are hard to be found. While some of the data required can be found on the internet and in books, their quality and accuracy are debatable, since every author has its own point of view regarding costs and many times the cost is an average value or approximation. Other costs that can be found on the internet are either out of date or come from a different market that the one under investigation. That would be the example of cables. A list provided by Nexans was found online but was from 2017 and from New Zealand. This means that inflation and exchange rate had to be considered to bring values to 2021. Even then there is no guarantee that prices are accurate, as for bigger orders usually there is a discount, governed by the supply contract. The most difficult part of cost data is related to items that are just not available online. This is the case for all the products used in OC/SWOC installations and in railway applications in general. These items comprise bidding items and therefore are considered as classified information, with little to no access to the public for reasons of competition. This kind of data can only be accessed through direct contact with the companies involved in designing and implementing railway signalling infrastructure. − Schematics and maps from the installation being examined are of paramount importance for an accurate estimation of LCC for OC/SWOC installations. These schematics include mapping data related to the general area of the installation (orthophotos, property maps, utility maps etc.) but also maps specifically related to the installation such as signalling plans and cable plans. 93 | 5. Conclusions and future work
− National regulations are also very important, particularly when they consider the railway infrastructure. This includes infrastructure standards and in case of Sweden, TRV has a lot of standards, which can be used to determine costs with accuracy.
5.1.4. Profitability of OC vs SWOC installations The last important topic emerging from this work is related to the question whether for an installation it is profitable to use OC or SWOC and for that the case of Björbo station was explored. Naturally, the cost of hardware and civil works can drive the LCC up or down. However, it was shown that this is not the primary reason. Instead, the most prominent drivers of choice, given the fact that the only variables that change are the number of OCs or SWOCs are rather related to the following parameters, which should be considered collectively rather than separately:
− Distance of interlocking from the station. When cables and related civil works are considered within the station for SWOC installations in comparison with OC installation, a SWOC benefits from eliminating the FO between SWOCs, something which for small stations is not a big cost. However, the biggest difference is that SWOC saves all the cabling between station and interlocking, which can be kilometers away. It was shown that for Björbo with 1 SWOC and everything else being equal, except for the addition of local power source for SWOC, it is always profitable to use SWOC, independent of the distance. However, as more OCs/SWOCs are added to control the different TSE and the cost of energy source increases, it seems that for very small distances from the station (between 500 and 1000 m), if an interlocking is located within that range, then it is more profitable to use OCs instead of SWOCs. For bigger distances however, SWOC is always more profitable, as the extra cabling between station and interlocking quickly tips the scale in favor of SWOC. − Cost of local power supply. It was shown that its cost depends on many parameters which can be traced all the way back to its design. First is the question of types of power sources: what kind of power sources are used, with what specifications and in what mix. This underlines the principle that the same function can be achieved with a variable mix of energy sources: PV and wind turbines, wind turbines and fuel cells, small and big wind turbines to take advantage of different wind speeds are just few of the options. Next, is the question of autonomy of the system: how many hours an installation should be able to operate without power, in cases when wind does not blow, or sun does not shine. Furthermore, dimensioning must answer the question whether each power source must provide the required energy amount independently or in tandem with others. Finally, it is a question of energy requirements themselves: The general rule is that the higher the energy requirements, the more expensive a SHS is. Its effect on the choice of OC or SWOC is that by increasing the power requirements the total cost of a SWOC solution increases and that drives the equilibrium point to the right of the graph. − Size of station. The size of station is better defined here as the number of TSE and OC/SWOC deployed inside the station, rather as a function of distances. In that sense, 5. Conclusions and future work | 94
from a signalling perspective, a station may be half the actual size of another but in terms of equipment it can have double the number and thus require double more energy. Looking the size of a station from that perspective, it seems that when OCs/SWOCs are added, the equilibrium point moves towards the right (in the case of Björbo because the introduction of more OCs makes the OC solution comparatively cheaper to SWOC solution at close distances). Of course, the effect of more TSE and OC/SWOCs needs to be investigated further. − Traffic Volume. It was proven that an increased amount of traffic favors the OC solution more, by increasing the cost of SWOC and therefore moving the equilibrium point to the right. This is because in comparison with the OC option, a SWOC installation must consider the cost of SHS as well. As the traffic increases, so does the power requirements, which increase the SWOC installation cost.
The points above are summed on Figure 97, as well as on Figure 94 and Figure 96.
Figure 97: Choice of OC vs SWOC. own edit
95 | 5. Conclusions and future work
5.2. Future work This work attempted to create a process of estimating the LCC of a SWOC installation, as well as to discuss it in a railway signalling system context by highlighting all the main aspects and parameters that affect the formulation of the LCC model. However, this work cannot cover the full spectrum of issues affecting the LCC of a SWOC or OC installation. Several important topics can be defined for future work:
− Refinement of LCC model. In this work, a workable LCC model was defined. However, due to restricted amount of data and time, the modelling process could not advance deeper. In the future, a potential direction is to refine several sub models that help defining the total LCC cost: design cost, construction, and installation cost, as well as the OPEX part of LCC, by defining maintenance models better. − Considering the actual spatial footprint of an installation. Here, a rather simplistic approach was defined in order to calculate the distances between different TSE, OCs/SWOCs and other system elements. In reality that does not apply: the distances between different elements are bigger, as cables follow the track geometry inside a station or along an open track. Therefore, future modelling attempts must take more detailed cable plans into account. − Radio communication parameters. One of the aspects that could affect the SWOC solution cost but was not discussed was the radio communication part. It was stated that a SWOC is capable of using different radio communication protocols, ranging from GSM-R to TETRA and 4/5G. However, radio cells have a limited radius or cell size, which depends on the parameters of each radio communication mode. That being said, there may be cases where SWOC is out of coverage, which means that an extra radio tower has to be erected or maybe an extra SWOC placed somewhere in between. That could incur extra costs which is wise to be included in LCC calculations (at least the CAPEX part). − Better data regarding capital costs of cables and civil works. The data that was provided was adequate for the modelling effort. However, data regarding cabling or civil work costs could be much more accurate. That being said, a future endeavour could include more accurate values from that standpoint.
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Appendix A: Literature review | 100
Appendix A: Literature review
Table 6: Information flow in level 1, 2 ,3 and ERTMS-R. Source: [19], own editing
Figure 98: Relative size of modern wind turbines. Adapted from Manwell et. Al. (2002). Cited in [64]
101 | Appendix A: Literature review
Table 7: Some RTD & E LCC categories. Source: [47]
Table 8: Some LCC categories for acquisition expenses. Source: [47]
Appendix A: Literature review | 102
Table 9: Some LCC Categories for operations and support expenses. Source: [47]
103 | Appendix B: Methodology
Appendix B: Methodology
Figure 99: Companies with great transport needs along the Västerdalsbanan line. Source: Ramböll, 2009b, referred into [49](commissioned by Västerdalsbanan's interest association).
Figure 100: Property map from station area in Björbo. Source: [54]
Appendix B: Methodology | 104
Figure 101: Possible locations of power supply from local grid-Björbo. Source: [54], own editing
Figure 102: Local electric network in the vicinity of Björbo railway station. Source: [66] 105 | Appendix B: Methodology
Figure 103: Principle of partial indifference of cabling cost towards the distances between signalling equipment. Source: own edit
Table 10: Current carrying capacity of cables-IEE current ratings (Table 4E1A). Source: https://www.cse- distributors.co.uk/cable/technical-tables-useful-info/table-4e1a/ TRITA TRITA-SCI-GRU 2021:241
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