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Guidance on The Design, Selection, Installation and Use of Uninterruptible Power Supplies Onboard Vessels

International Marine Contractors Association IMCA M 196 April 2009 www.imca-int.com

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The International Marine Contractors Association (IMCA) is the international trade association representing offshore, marine and underwater engineering companies.

IMCA promotes improvements in quality, health, safety, environmental and technical standards through the publication of information notes, codes of practice and by other appropriate means.

Members are self-regulating through the adoption of IMCA guidelines as appropriate. They commit to act as responsible members by following relevant guidelines and being willing to be audited against compliance with them by their clients.

There are two core activities that relate to all members:  Competence & Training  Safety, Environment & Legislation

The Association is organised through four distinct divisions, each covering a specific area of members’ interests: Diving, Marine, Offshore Survey, Remote Systems & ROV.

There are also four regional sections which facilitate work on issues affecting members in their local geographic area – Americas Deepwater, Asia-Pacific, Europe & Africa and Middle East & India.

IMCA M 196

This report was prepared for IMCA, under the direction of its Marine Division Management Committee, by Noble Denton Consultants Ltd.

www.imca-int.com/marine

The information contained herein is given for guidance only and endeavours to reflect best industry practice. For the avoidance of doubt no legal liability shall attach to any guidance and/or recommendation and/or statement herein contained.

Guidance on The Design, Selection, Installation and Use of Uninterruptible Power Supplies Onboard Vessels

IMCA M 196 – April 2009

Summary ...... 1 List of Abbreviations ...... 2 1 Introduction ...... 3 1.1 Acknowledgements and Contributions ...... 3 1.2 UPS Definition ...... 3 1.3 Purpose of this Document ...... 3 1.4 Survey of Vessel UPS and DC Power Supply Installations ...... 3 1.5 List of Manufacturers ...... 4 2 Type of UPS Used Onboard Vessels ...... 5 2.1 UPS Internal Topology ...... 5 2.2 Standby UPS ...... 5 2.3 Ferro-Resonant Standby UPS ...... 6 2.4 Line Interactive UPS ...... 6 2.5 Online UPS ...... 7 2.6 Delta Online UPS ...... 8 2.7 Manual Bypass ...... 8 2.8 UPS Features ...... 8 2.9 Testing UPSs at Annual DP and Field Arrival Trials ...... 9 2.10 Qualifying UPSs for Marine Applications ...... 9 2.11 Types of Batteries for UPS ...... 9 3 Types of DC Power Supplies Used on Vessels ...... 10 3.1 DC Power Supplies Topology ...... 10 3.2 System Specification ...... 10 3.3 Types of Batteries for DC Power Supplies ...... 11 4 Types of Batteries Used Onboard Vessels ...... 12 4.1 Battery Definitions ...... 12 4.2 Types of Secondary Batteries ...... 12 4.3 Types of Lead Acid Batteries ...... 12 4.4 Types of Nickel-Cadmium Wet Cell Batteries ...... 13 4.5 Advantages and Disadvantages of Battery Types ...... 14 4.6 Battery Maintenance ...... 14 4.7 Battery Inspection ...... 15 4.8 Battery Load Testing and Alternatives...... 15 4.9 Conductance Testing FAQ ...... 16 4.10 Battery Charging ...... 17 4.11 Battery Cell Temperature ...... 18 5 Application of UPS and DC Supplies Onboard Vessels ...... 20 5.1 General ...... 20 5.2 UPS for Control Systems ...... 20 5.3 UPS for Voice and Data Communication Systems ...... 21 5.4 UPS for Safety Related or Critical Systems ...... 21 5.5 UPS for Emergency Systems ...... 21 5.6 DC Supplies with Battery Backup – Application to Generation Systems ...... 21 6 Integration into Vessel Systems ...... 23 6.1 Electrical Considerations ...... 23 6.2 Run Time ...... 23 6.3 Harmonics ...... 25 6.4 Interface Systems Considerations – Alarms and Monitoring ...... 26 6.5 Dual Supplies to UPSs ...... 26 6.6 ESD Requirements ...... 27 6.7 UPS Systems DC Power Supplies – Fault Levels and Protection Discrimination ...... 27 6.8 Dual Voltage UPSs...... 27 6.9 Common/Summary Alarm ...... 28 7 Strategies for UPS and DC Distribution ...... 29 7.1 General ...... 29 7.2 Minimum Requirement ...... 29 7.3 Distributed UPS Arrangement ...... 31 7.4 Centralised UPS Systems...... 32 7.5 Backup UPS ...... 33 7.6 Strategies for DC Power Supply Distribution ...... 34 7.7 Cross Connection of DC Power Supplies ...... 34 8 Class Requirements for UPS, DC Supplies and Batteries ...... 36 8.1 General ...... 36 8.2 Common Requirements ...... 36 8.3 Standards Organisations ...... 36 9 Switching Arrangements ...... 44 9.1 General ...... 44 9.2 Main and Backup Supplies to UPSs ...... 44 9.3 Static Switches ...... 45 9.4 Changeovers at UPS Output or in the Distribution Scheme ...... 46 10 Operational Issues ...... 47 10.1 Safety Considerations ...... 47 10.2 Environmental Considerations ...... 47 11 Suitability for Marine Applications ...... 48 11.1 General ...... 48 11.2 Construction for Marine Environment ...... 48 11.3 Design for Marine Applications – UPS ...... 48 11.4 Design for Marine Applications – DC Supply ...... 50 12 References ...... 52 Appendices 1 UPS Qualification Checklist ...... 53 2 Data on UPS, DC Power Supplies and Batteries ...... 55 Survey of Owners and Operators of UPS Equipment ...... 55 Survey of Owners and Operators of DC Equipment ...... 58 NDC Desktop Survey of UPS Types...... 59 VRLA Cells – Results of Vessel Survey, Vessel Technical Information and Desktop Investigation ...... 63 Wet Cells – Results of Vessel Survey, Vessel Technical Information and Desktop Investigation ...... 66

Summary

This document was commissioned by the International Marine Contractors Association and is intended to provide the reader with guidance on the design, selection, installation and use of UPSs and DC power supplies for marine applications.

Information provided by IMCA members confirms that there is a very wide range of manufacturers supplying UPSs to the marine sector. Most of these units are of commercial grade and of the online type, that is to say, the inverter continuously supplies the load.

There is a wide variation in the cost, quality and capability of UPSs and purchasers should carefully consider and understand the required application and the electrical and environmental conditions in which the UPS or DC power supply will be expected to operate.

Features and levels of performance cannot be taken for granted and standards for UPS design assume that much of the specification for performance will be agreed between the purchasers and the supplier. Therefore, simply making reference to a particular standard in a specification document does not necessarily guarantee the unit will be fit for purpose.

In addition to poor choice of equipment for particular applications, the investigation revealed that premature battery failure is a key issue in UPS reliability and maintainability. Thus the guidance provided concentrates heavily on the maintenance and testing of batteries and on the advantages and disadvantages of different battery types.

IMCA M 196 1 List of Abbreviations ABS American Bureau of Shipping LCD Liquid crystal display AC Alternating current LED Light emitting diode AGM Absorbed glass Mmat/absorptive glass LRS Lloyds Register micro-fibre MCB Main circuit breakers Ah Amp hour MF Maintenance free AHC Anti heave compensation MODU Mobile offshore drilling unit AVR Automatic voltage regulator MSB Main switchboard BCR Breaker close relay MSC Maritime Safety Committee COSWP Code of Safe Working Practices for NDC Noble Denton Consultants Ltd Merchant Seamen NiCaD Nickel-cadmium DC Direct current NMEA National Marine Electronics DDP Deep discharge protection Association DG Distributed generation PC Personal computer DNV Det Norske Veritas PCB Printed circuit board DOD Depth of discharge pf Power factor DP Dynamic positioning PLC Programmable logic controller DSP Digital signal processing PMG Permanent magnet generator ECU Electronic/environmental control unit PMS Power management system EG Emergency generator RCS Remote control system ESD Emergency shut down RCU Remote control unit FMEA Failure modes and effects analysis RMS Route mean squared HSE Health & Safety Executive (UK) ROV Remotely operated vehicle HV High voltage SBC Single board computer IAS Integrated automation system SCR Silicon control rectifier IEC International Electro Technical SLA Sealed lead acid Committee SLI Starting, lighting and ignition IEEE Institute of Electrical & Electronic Engineers SOLAS Safety of Life at Sea IMO International Maritime Organization SWBD Switchboard IP Ingress protection TMS Thruster management system ISM International Safety Management UPS Uninterruptible power supply ISO International Standards Organisation VA Volt-amperes IT Information technology VFD Variable frequency drive kV Kilo volt VMS Vessel management system kVA Kilo volt ampere VRLA Valve regulated lead acid kVAr Kilo volt ampere reactive VRPP Valve regulated pocket plate kW Kilowatt VT Voltage transformer LA Lead acid WCFDI Worst case failure design intent

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1 Introduction This document provides guidance on the design, selection, installation and use of uninterruptible power supplies (UPS) for marine applications.

1.1 Acknowledgements and Contributions

Thanks are due to the following companies for their contribution to this document:  Norco Group Ltd – www.norcoenergy.com  Transocean Engineering, Houston – www.deepwater.com  Knutsen OAS Shipping AS – www.knutsenoas.com  Converteam – www.converteam.com  Kongsberg Maritime – www.km.kongsberg.com  Helix Energy Solutions – www.helixesg.com  Technip – www.technip.com

1.2 UPS Definition

IEC/EN/BSI standard 62040-3, ‘Uninterruptible Power Systems (UPS)’ defines an uninterruptible power system as:

A combination of converters, switches and energy storage means, for example, batteries, constituting a power system for maintaining the continuity of load power.

Although most standards on UPSs deal only with units providing an AC output, this guidance document will also consider DC power supplies employing batteries as they share many of the same issues with AC UPSs.

1.3 Purpose of this Document

This document is intended to provide information on the design, selection, installation and use of UPSs for marine applications. This is a very large subject which touches upon complex issues in electrical power engineering. The intention is to provide the reader with an understanding of the main issues to aid in the preparation of specifications and maintenance regimes. Issues associated with design and installation are also discussed. However, much still depends on the experience and competence of both purchaser and vendor.

1.4 Survey of Vessel UPS and DC Power Supply Installations

A survey of vessel UPS and DC power supply installations was carried out in the process of preparing this document. Some of the information was received from members in response to information note IMCA M 12/08. Other information was taken from Noble Denton Consultants Ltd’s (NDC) archive of FMEAs carried out on dynamically positioned (DP) vessels. A sample of 15 vessels of various types was studied including DP Class 2 and DP Class 3 drilling rigs, pipelayers and construction vessels with some respondents providing general commentary on equipment used across their fleet. The information obtained is presented in tabular form in Appendix 2 and a summary of the findings is presented below.

The survey revealed that there are a very large number of manufacturers providing UPSs used onboard vessels. Seventeen different brands of UPS and DC supply were identified from the sample but an internet search suggests there are many more. Further investigation revealed that certain groups of well known brands are owned by the same parent company. Most of the units were of the online type (also known as double conversion) but other types of UPS are in use onboard vessels including ferro resonant types and line interactive units. No examples of the more basic standby UPS were noted but these may be found in minor roles for backing up non essential PCs, etc. A more detailed discussion of these different types of UPS is given in Section 2.

IMCA M 196 3 As might be expected, the UPS brands favoured by the major DP and vessel management system providers feature strongly. In particular, one well known manufacturer of DC systems and nickel cadmium (NiCad) batteries features strongly in the section on DC power supplies for switchboard controls.

Although some UPS manufacturers do offer a range of ‘marine’ UPSs, most units appear to be commercial units intended for the protection of small to medium sized IT equipment such as servers in offices and factories. In many cases, the UPS unit is repackaged by a third party supplier into a more rugged enclosure which may include anti-vibration mounts, MCBs for the distribution system, the batteries and external bypass circuits. There are few reports of dissatisfaction with the performance of online units but problems have been reported with ferro-resonant and line interactive types.

UPSs for propulsion and vessel control applications tend to be in the range 2kVA to 15kVA at 110V or 220V single and three phase output. Output voltages include 110V, 230V or 480V single or three phase with some two phase units.

Most vessels reported their main source of UPS problems as unexpected battery failure. In the course of the survey, it was noted that there is also a very large range of battery manufacturers offering a wide variety of battery types and models. It was further noted when studying the technical specification of UPSs that it could be difficult to determine exactly what type of battery was being offered with each UPS. This is quite significant as it is possible to specify batteries with very different expected lifespan. A much more detailed discussion of batteries and their characteristics is presented in Section 4.

Following internal discussions, it was agreed that manufacturers’ names and model numbers should be replaced with a code. None of the products from manufacturers included in the survey was significantly worse than any other although some vessel owners did express a preference for one or two brands. In cases where there have been significant problems they are usually related to wrong application or poor specification rather than issues of quality.

The most important lesson to be learnt is that in order to select a unit which is fit for purpose it is important to understand the limitations of the type of UPS being offered and the physical and electrical environment in which it will be operating. These issues should then be discussed and agreed with the UPS supplier. Appendix 1 provides a checklist to assist the vessel owner in this task.

1.5 List of Manufacturers

The following list of UPS and DC power supply manufacturers was created from the survey of members’ replies to information note IMCA M 12/08 and reviews of archive information. The omission of a UPS manufacturer from this list does not imply unsuitability of their products for marine applications. In fact, a review of information in the public domain suggests that there are many more manufacturers that may be worthy of consideration.  APC  General Electric  MGE  Siemens  Best UPS  HHI  Powec  Socomec  Cigentec  Jotec  Power Innovations  Toshiba  Eltek  Marathon  Powerware  XP  Enersys  Mastervolt  SAFT

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2 Type of UPS Used Onboard Vessels

2.1 UPS Internal Topology

This section presents an overview of the theory of operation of different types of UPS. When specifying a UPS for a particular application, it is vitally important to know what technology is being offered by any given vendor as some technologies are more suitable than others for certain applications.

The capability, performance and reliability of a UPS is dependent both on the quality of the power supply to which it is connected and the electrical characteristics of the load it supplies. Commercial UPSs are optimised to be competitively priced and efficient in operation and are tailored to their primary role. The main market for UPSs is protection and continuity of supply to shore-based computer systems and other IT equipment. In recent times, industry standards have improved the ride-through capability of this type of equipment to the point where the short supply interruptions associated with some UPS topologies do not affect the operation of the load. Although UPSs are used to supply similar types of loads on vessels, the same level of ride-through capability should not be assumed. Similarly, in the developed world, utility power supplies are generally very stable, in both frequency and voltage and of low harmonic content. Again, UPS designers take advantage of this in developing and optimising their products. Power system quality is generally much poorer in most marine applications and can be particularly bad on vessels with large electric propulsion and drilling loads.

Some vendors do offer a range of marine UPSs and many commercial UPSs are suitable for use on poor quality marine power systems. However, it is important to note that industry standards for UPSs, such as IEC 62040-3, require the buyer and vendor to agree many aspects of the specification if the operating conditions are unusual. Therefore, simply quoting UPS standards in a vessel specification without additional information and qualification may not ensure that a UPS system is fit for purpose.

At the most basic level, there are only two types of UPS defined as ‘online’ and ‘standby’. In a standby UPS, the load is normally supplied directly from the main AC input by way of a filter. The unit switches to inverter-battery mode on detection of supply failure. In the online design, the load is always supplied from the inverter source and the battery is continuously charged during normal operation by way of the rectifier stage (or a separate battery charger). However, there are two types of online UPS and three distinct types of standby UPS which are sufficiently different in design to be recognised as types in their own right. Therefore, in practical terms, there are essentially five main types of UPS:  Standby UPS;  Ferro-resonant standby UPS;  Line interactive standby UPS;  Online UPS;  Online Delta UPS.

2.2 Standby UPS

The simplest form of UPS is the standby UPS. Figure 1 below shows the main components of such a system. In this design of UPS, the load is supplied from the main AC input by way of a filter and an auto-changeover (usually a static switch). The control system monitors the quality of the incoming power and switches the load to the inverter supply on detection of poor quality. However, the sophistication of the control system and the range of supply voltage parameters initiating a changeover may vary greatly from one model to the next. There is a short supply interruption during transfer to inverter mode. The transfer time is typically quoted as 4ms but detection times may extend this. As the zero-voltage ride-through time of commercial IT equipment power supplies is generally taken to be of the order of 10ms, this type of UPS works well in its intended application. This includes the protection of individual PCs in shore-based applications but does not guarantee that it will be effective or reliable in marine applications. The reason for this is that poor quality marine power supplies require the inverter to switch on and off more frequently than shore-based applications. The load will also be exposed to any supply voltage and frequency variations and transients which do not cause a

IMCA M 196 5 changeover to inverter mode. Thus the quality of the power delivered to the load is dependent on the quality of the line conditioning and the sophistication of the control circuitry. Even in its intended market, this type of UPS is generally only specified for very small loads and is generally not recommended for use in the propulsion and control systems of modern vessels.

SENSE LINE CONTROL CCT

LINE OUTPUT CONDITIONING CIRCUIT BREAKER MAIN AC INPUT

FILTER BATTERY CURRENT BATTERY CURRENT FLOW DURING FLOW DURING LOAD NORMAL STORED ENERGY OPERATION MODE

Figure 1 – Standby UPS

2.3 Ferro-Resonant Standby UPS

Refer to Figure 2. The ferro-resonant UPS is a development of the simple standby UPS in which the changeover switch is replaced by a ferro-resonant transformer. Such transformers are carefully designed to form a resonant circuit in combination with suitable capacitance. By designing the transformer to operate in saturation, considerable voltage variation can be tolerated without switching to inverter mode and battery supply. As the ferro-resonant transformer’s primary role is in line conditioning, it is ideally suited as a line conditioner for the main AC supply. Because it operates as a resonant circuit, the transformer will also continue to provide an output voltage during the short interruption between detecting loss of the main supply and start up of the inverter.

On marine power systems there can be significant swings in frequency. Because the ferro-resonant transformer is effectively synchronised to main AC input it cannot protect the load from changes in the steady state frequency and thus will transfer to battery power in this case. Although very popular at one time, the ferro-resonant transformer has largely been replaced by line interactive and online type UPSs for reasons of size and cost. This type of UPS is no longer recommended for use in the propulsion and control systems of modern vessels.

MAIN AC OUTPUT INPUT CIRCUIT BREAKER

SENSE LINE

LOAD LINE CONTROL CONDITIONING BATTERY CCT CHARGER

FERRO-RESONANT TRANSFORMER FILTER

INVERTER BATTERY

Figure 2 – Ferro-resonant UPS

2.4 Line Interactive UPS

The line interactive UPS represents a further advance in the design of the standby UPS.

Figure 3 shows the arrangement of the main components. In this type of UPS there is a single power converter capable of bi-directional operation. During periods when the quality of the main AC input power remains within acceptable limits, the filtered mains power is fed directly to the load and the converter acts as a battery charger. On detecting that the input power has failed, or is no longer within tolerance, the converter reverses its direction of power conversion and feeds the load. Line

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interactive UPSs still account for a large share of the low and medium power range and offer cost effective protection. For their intended role in shore-based IT systems, they have been optimised to the point where many consider them to be the equal of online UPSs. They are generally more efficient than online UPSs because they only have one stage of power conversion instead of two. For most of the time the power converter is acting as a battery charger at very low load and thus its losses are also low. Like all standby UPSs much of its efficiency comes from the fact that the input power quality is expected to be good with only infrequent transfers to inverter mode. This may not be the case in some marine applications. In the worst case, the unit may operate on battery supply so frequently that the battery becomes depleted leading to a switch back to bypass mode regardless of power quality. Although there are a number of modern vessels using line interactive UPSs in propulsion systems, the online or double conversion UPS is preferred where isolation from poor quality power and security of supply is the main consideration.

LINE CONDITIONING

MAIN AC OUTPUT INPUT CIRCUIT BREAKER FILTER

LOAD SENSE LINE CONTROL CCT STATIC CHANGEOVER BATTERY SWITCH CHARGER

INVERTER BATTERY

Figure 3 – Line interactive UPS

2.5 Online UPS

The online or double conversion UPS is considered to provide the highest level of isolation from poor quality supplies. As its name suggests, the load is always supplied by the inverter. Figure 4 shows the arrangement of the main components. A common line-conditioning stage supplies the rectifier/battery charger and the automatic bypass line. As is the case with the standby UPS, either the inverter output or the bypass line is selected by a static (solid state) switch. Unlike the standby UPS, the inverter supply is the normal supply. In theory, the automatic bypass is not essential to the operation of an online UPS. In practice, the bypass is provided to cover for failure or overload of the inverter. Some online UPSs have an ‘economy mode’ in which their mode of operation changes to standby mode while power quality is good. The inclusion of such a feature in a UPS specification is unlikely to be important for marine applications and may even be undesirable.

SENSE LINE CONTROL CCT

LINE CONDITIONING BYPASS MAIN AC OUTPUT INPUT CIRCUIT BREAKER FILTER

LOAD

BATTERY CHARGER

INVERTER BATTERY

Figure 4 – Online UPS

IMCA M 196 7 2.6 Delta Online UPS

The delta online UPS is a patented concept which offers a significant improvement in efficiency over the conventional double conversion online UPS. The designers claim that it is suitable for use with all types of generators. As it requires no input filter, it may also help to avoid the problems associated with adding filters to power systems with a high harmonic content. The delta online UPS is a relatively recent concept and as such may have had limited exposure to the marine market but vessel owners may wish to carry out further evaluation of this novel design to see what advantages it provides. In very basic terms, the theory of operations is that the current in one winding of a differential (delta) transformer is controlled by a rectifier-battery-inverter combination producing the desired voltage and frequency (but not the load current). This in turn controls the current in the other winding of the delta transformer and thus the load voltage. In the event that the supply voltage fails, the inverter and battery supply the load as they would in a conventional double conversion UPS.

DELTA TRANSFORMER

LOAD

Figure 5 – Delta online UPS

2.7 Manual Bypass

Most UPSs offer a manual bypass facility. Some classification societies require that this is physically separate from the UPS enclosure if the UPS is used to supply emergency services. By the same rule, the power distribution would have to be separate from the UPS enclosure to ensure the desired level of independence. Most manual bypass facilities are included in the UPS enclosure along with the batteries and the circuit breakers for power distribution.

2.8 UPS Features

UPSs can be purchased with a very wide range of features depending on the size and cost of the unit. Even fairly modest UPSs make use of digital signal processing (DSP) technology as a part of their control functions.

Diagnostics: UPSs can now provide a great deal of information on a range of conditions including converter health, control systems health and battery condition.

Battery curves: In UPS units which can accept different types and numbers of batteries, it is possible to load different battery discharge characteristics into the control systems. This information is used to control advanced charging systems and also to provide a ‘fuel gauge’ type indication of remaining time on batteries.

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Voltage regulation: In the simplest online UPSs, the output voltage is determined by the DC link voltage level which falls steadily when the battery is being discharged. More sophisticated UPSs use a dc/DC converter between the battery and the DC link to maintain the output voltage within tight tolerances.

Deep discharge protection: Some manufactures fit deep discharge protection to prevent the batteries being damaged by a deep discharge. One problem with this type of protection is that it may reduce the time on batteries as they age. Such features generally disconnect the load when the battery voltage has fallen to a predetermined level.

Graceful shutdown alarm: Most UPSs of the size found onboard vessels are capable of providing a control signal which can instruct the load being supplied to shut down in a graceful manner. This function could be used to prevent hard drive failure in VMS operator stations but is not generally used in marine applications. Where this feature is more commonly used is in UPSs for the control systems of variable speed drives. In some designs of modern drives there is a risk of damage to the drive if the control system fails or power to the control system is lost. A small UPS with a run-time of around 10 minutes can be used to protect the drive against failure of the auxiliary power supply. As soon as the UPS detects that mains power has been lost the UPS will signal the drive to commence a graceful shutdown before the batteries expire.

Hot swap batteries: UPSs with this feature have already been fitted to some members’ vessels. The batteries are in slide-out trays that can be removed a bank at a time without the UPS dropping the load.

2.9 Testing UPSs at Annual DP and Field Arrival Trials

Battery endurance testing is a feature of the annual trials carried out by DP Class 2 and DP Class 3 vessels. Some vessels also carry out battery endurance tests as part of the field arrival trials. In some cases this could mean that UPS batteries are being discharge tested every month. Classification society rules require that UPS batteries supply the load for at least 30 minutes. Battery life is affected by the number and depth of discharge cycles that the battery experiences in a given time.

With this in mind, it may be prudent to confirm that the batteries are not being over-tested to the point where reliability is actually reduced by testing, not enhanced. Similarly, when determining the battery capacity required of a UPS, vessel owners may wish to include a margin for routine testing that ensures the battery will not be damaged. Care should also be taken that any margin is not eroded by the addition of extra loads. Experience shows that the demand for UPS power grows throughout the life of a vessel as modifications and enhancements are added to the DP controls and other systems. Additional position reference systems, sensors, monitors, data recorders and bridge PCs all place extra demands on existing UPSs.

2.10 Qualifying UPSs for Marine Applications

UPSs for marine applications can be qualified initially by a review of the UPS design against the required specification.

The power systems of drilling rigs present a particular challenge for UPSs and some drilling contractors have experienced significant problems with UPSs failing due to the overload of internal components. One major drilling contractor has even gone so far as creating its own method for qualifying UPSs for use on power systems with high levels of harmonics and commutation notches associated with drilling drives. The qualifying procedure involves operating the UPS from a test rig consisting of a small generator driving a 6 pulse variable speed drive to recreate typical drilling system distortion. The performance of the UPS is closely monitored during an extended test period to prove reliability of operation in all modes and the quality of the output power that it is able to provide. This type of qualification procedure should be considered by any vessel owner with similar power system problems.

2.11 Types of Batteries for UPS

The vast majority of UPSs use a VRLA (lead acid) battery of various types. See Section 4 for more detail on the advantages and disadvantages of various battery types.

IMCA M 196 9 3 Types of DC Power Supplies Used on Vessels

3.1 DC Power Supplies Topology

System terminology: In its simplest form, the DC power supply consists of a battery charger, battery bank and distribution system with associated protection. The term ‘battery charger’ is misleading and these units should more properly be called rectifier control units as they are capable of delivering the full power requirements of the system without contribution from the battery.

Voltage levels: 110V DC power supplies are traditionally used for high voltage switchboard control systems. Engine and thruster controls are typically supplied at 24V DC. Applications are considered in more detail below under ‘Installation monitoring’.

Battery management: This feature is key to ensuring the longevity of battery banks and multi stage charge with a boost, absorption and float stage are commonplace now. It should be noted that battery types cannot be interchanged without consideration of the battery charging systems. In particular, chargers used for lead acid batteries cannot be used for nickel cadmium batteries unless designed for dual purpose operation. Adjustment or a change of charger may also be required between different types of lead acid batteries and manufacturers’ guidelines should be followed.

Association of major components: Figure 6 and Figure 7 show two possible physical configurations of the major elements of a DC system. The arrangement in Figure 7 offers the advantage of being able to isolate the battery bank without having to disconnect the distribution.

AC SUPPLY BATTERY DISTRIBUTION BANK

Figure 6 – Linear configuration of rectifier, battery bank and distribution

AC SUPPLY BATTERY DISTRIBUTION BANK

Figure 7 – Branch configuration of rectifier, battery bank and distribution

Installation monitoring: Installation monitoring of the system for over/under voltage, over-current and earth fault should be a minimum requirement.

3.2 System Specification

When specifying a DC supply system for a particular application, it is important to know what battery, charger and distribution system technology is being offered by any given vendor as some technologies are more suitable than others for certain applications.

The capability, performance and reliability of a DC supply system is dependent both on the quality of the power supply to which it is connected and the electrical characteristics of the load it supplies. Power system quality is generally much poorer in most marine applications and can be particularly poor on vessels with large electric propulsion and drilling loads.

The type of battery bank used has to take into account the following:  the regulations and requirements of the certification authorities;  the duration (ampere hour) system requirements;  the supply voltage system requirements;  the current level system requirements;  location considerations (corrosive effects, ventilation);

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 ventilation requirements and maintained battery bank cell temperature;  battery electrolyte spillage containment;  fault level capability (ability to supply system fault levels and maintain voltage levels);  IP classification of enclosure;  maintenance/inspection requirements.

The type of charger (rectifier control unit) used has to take into account the following:  the regulations and requirements of the certification authorities;  the supply voltage quality;  the output voltage quality (maintained voltage levels and ripple factor);  the charge requirements of the batteries;  the monitoring and alarm requirements of the system;  interface alarms requirements to VMS;  the internal protection requirements;  the external protection requirements of the distribution system;  fault level capability (ability to supply system fault levels and maintain voltage levels);  IP classification of enclosure;  maintenance requirements.

The type of distribution system used has to take into account the following:  the regulations and requirements of the certification authorities;  monitoring of system voltage and current’  type of system grounding – either ‘intentionally grounded’ or ‘floating’ with ground fault protection;  alarm requirements of the system (interface alarms to VMS);  the internal protection requirements of feeder and outgoing breakers (overload and short circuit protection);  co-ordination of protection with battery charges, battery bank and outgoing feeders;  IP classification of enclosure;  isolation and lock off facilities of supplies and feeders;  maintenance/inspection requirements.

3.3 Types of Batteries for DC Power Supplies

Vessel survey results in Appendix 2: The survey results do not contain many examples of DC systems, however the limited results indicated that DC systems utilise wet cell batteries.

Desktop study results in Appendix 2: The survey results confirm that the majority of DC systems currently in use utilise wet cell batteries.

IMCA M 196 11 4 Types of Batteries Used Onboard Vessels

4.1 Battery Definitions

Primary batteries: Primary batteries are designed to transform chemical energy into electrical energy. When the initial supply of energy reactants is exhausted it cannot be restored to the battery by electrical means.

Secondary batteries: Secondary batteries are designed to transform chemical energy to electrical energy like primary batteries. However, when the supply of energy reactants is depleted or exhausted the batteries can be recharged. Secondary batteries can have their chemical reactions reversed by supplying electrical energy to the cell and therefore restoring their original composition. Although rechargeable batteries may be refreshed by charging, they suffer degradation primarily through charging, discharging, age and environmental (temperature) operating conditions.

Battery shelf life: This is the time an inactive battery can be stored before it becomes unusable. When a battery has reached 80% of its initial capacity, it is usually considered unfit for usage.

Battery calendar life: This is the elapsed time before a battery becomes unusable whether it is in active use or inactive.

4.2 Types of Secondary Batteries

Two basic battery technologies are used onboard vessels, lead acid and nickel cadmium.

Secondary batteries can be categorised as follows:  open vent (wet or flooded cell) batteries;  sealed (valve regulated vent) batteries;  dry (valve regulated vent) batteries.

The categorisation of battery types into wet, sealed and dry batteries is not as precise as the names may suggest as most higher power batteries that are said to be sealed or dry are valve regulated. This design feature allows gas to be expelled in abnormal circumstances. Valve regulated nickel cadmium cannot be classed as dry as all the electrolyte is not absorbed by the glass mat.

The chemical types of batteries also fall into two basic categories these being:  lead acid batteries (open vent, sealed and dry);  nickel cadmium (open vent and sealed).

Some other derivatives of the nickel battery and lead acid types have been listed. The smaller nickel based dry types have not been considered for marine application due to their limited capacity and usage within the industry.

4.3 Types of Lead Acid Batteries

Wet cell (flooded) open vent: This is the standard lead acid battery. Within this type of battery range there is a large selection of batteries with high specification and advanced technology which has proven to be reliable over a long period of time.

Valve regulated lead acid (VRLA): The VRLA battery also called ‘sealed lead acid (SLA)’ is one of many types of lead acid batteries, also known as maintenance free (MF). In a VRLA battery, the hydrogen and oxygen produced in the cells recombine back into water. In this way there is no leakage and the battery can be considered to be maintenance free. This construction is designed to prevent electrolyte loss through evaporation, spillage and gassing and this in turn prolongs the life of the battery. Instead of simple vent caps on the cells to let gas escape, VRLA types have pressure valves that open only under extreme conditions. Valve regulated batteries also need an electrolyte design that reduces gassing by impeding the release to the atmosphere of the oxygen and hydrogen generated by the galvanic action of the battery during charging. This usually involves a catalyst that causes the

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hydrogen and oxygen to recombine into water and is called a recombinant system. Because spillage of the acid electrolyte is eliminated, the batteries are also safer. There are two main types of VRLA batteries which are discussed below.

Valve regulated lead acid – absorbed glass mat battery (AGM): Also known as ‘absorptive glass microfibre’; AGM is used in VRLA batteries such that the boron silicate fibreglass mat acting as the separator between the electrodes and absorbing the free electrolyte acting like a sponge. Its purpose is to promote recombination of the hydrogen and oxygen given off during the charging process. The fibreglass mat absorbs and immobilises the acid in the mat but keeps it in a liquid rather than a gel form. In this way the acid is readily available to the plates allowing fast reactions. This construction is robust and able to withstand severe shock and vibration and the cells will not leak even if the case is cracked. AGM batteries are also sometimes called ‘starved electrolyte’ or ‘dry’, because the fibreglass mat is only 95% saturated with sulphuric acid and there is no excess liquid. Nearly all AGM batteries are sealed valve regulated VRLA. This is the most common battery utilised for UPS systems found during this study.

Valve regulated lead acid – gel battery: This is a rechargeable valve regulated lead acid battery with a gelatinous electrolyte. The gel batteries virtually eliminate the electrolyte evaporation, spillage and therefore corrosion issues. It has a good resistance to extreme temperatures, shock and vibration and is therefore utilised in automobiles, boats, aircraft and other motorised vehicles. These batteries are often referred to as sealed lead-acid (SLA) batteries due to their non-leaking containers but they are not completely sealed, valve regulation allows for gas to be expelled. Chemically, they are the same as wet (non-sealed) batteries except that the antimony in the lead plates is replaced by calcium. The battery type is often referred to as a lead-calcium battery.

Deep cycle batteries: Often listed as for ‘marine applications’, these deep cycle batteries are designed to be completely discharged before recharging. Because charging causes excessive heat which can warp the plates, thicker and stronger or solid plate grids are used for deep cycling applications. With reference to marine application, the batteries are designed to supply equipment with longer intervals between recharging. They also have an engine starting capability and some models can perform a dual ‘domestic’/’starting’ role.

SLI batteries (starting lighting and ignition): This is the typical automotive battery application. Automotive batteries are designed to be fully charged when starting the vehicle; after starting the engine, the lost charge, typically 2% to 5% of the charge, is replaced by the alternator and the battery remains fully charged. These batteries are not designed to be discharged below 50% depth of discharge (DOD) and discharging below these levels can damage the plates and shorten battery life.

4.4 Types of Nickel-Cadmium Wet Cell Batteries

Wet cell (flooded) open vent: This is the standard nickel cadmium battery. Within this type of battery range, there is a large selection of batteries with high specification and advanced technology which has proven to be reliable over a long period of time.

Nickel-cadmium fibre plate batteries: The nickel fibre matrix used for the fibre plate allows 90% of the electrode volume for holding the active material. This fibre structure provides good conductivity to ensure electrical performance. In addition, the nickel cadmium fibre plate technology uses active material free from graphite and iron. The elimination of graphite ensures that the electrolyte does not get carbonated and the elimination of iron reduces water consumption.

Nickel-cadmium pocket plate batteries: Nickel-cadmium pocket plate batteries are said by the manufacturers to be the most reliable and rugged batteries available today. They can withstand to a great extent any type of abuse like overcharge, deep discharge, even accidental reverse charge, and can be stored in any state of charge.

Nickel-cadmium valve regulated pocket plate batteries (VRPP): VRPP batteries work on the oxygen recombination principle and therefore have much reduced water consumption. The level of recombination of these cells is 85-95% whereas normal vented type cells have a 30-35% recombination efficiency. When the VRPP cells are properly float charged, the manufacturers list that they will not need to be topped off with water for nearly 20 years. If the levels do become low during the life of the battery, there are provisions to add water to the cells.

IMCA M 196 13 4.5 Advantages and Disadvantages of Battery Types

Wet cell lead acid versus nickel-cadmium: There are many claims and counter claims from manufacturers of lead acid and nickel-cadmium wet cell batteries of the advantages and disadvantages of their product. Our research has found that this debate is less intense where the manufacturer supplies both types of batteries. Both lead acid and nickel-cadmium batteries are excellent products with a wide range and variety, offering numerous options to the design engineer. The specification requirements of the system design should be the dominant factor in deciding what type of wet cell battery should be used.

Wet cell versus valve regulated lead acid (VRLA): The specification requirements of the system design should be the dominant factor in deciding what type of battery should be used. This option may not be fully conveyed to the designer or purchaser as our research has found that UPS manufacturers may not offer various choices or options. The general findings are that DC systems use wet cells and UPS systems use some variation of valve regulated lead acid battery technology. The dominant factor for UPS systems appears to be the provision of a safe and maintenance free battery. However, no battery should be considered to be entirely maintenance free as periodic inspection is beneficial in all cases.

Types of valve regulated lead acid (VRLA): There are various types of VRLA batteries and general terminology has been found in UPS manufacturers’ information such as sealed battery, non spillage battery, dry battery. All non wet cell lead acid batteries have valve regulation.

Life span: Manufacturers’ information on VRLA batteries is dominated by claims of battery lifespan. As the majority of manufacturers make a selection of battery types with quoted life spans of 3-5 years, 5-8 years and 7-10 years, it should be possible to choose a suitable battery type. The dominant design specification is what design intent is set for the UPS system lifespan and, if the battery lifespan requires or can be selected to meet this same criteria, it could be concluded that the batteries with the longest lifespan should always be the choice. However, the owner or operator may have a policy of renewing all VRLA batteries every three to five years and this is an equally valid approach. It should be noted that the battery renewal costs may be 25 to 30% of the original cost of the UPS; therefore, renewal of the batteries three times may well be equal to the original project costs of the system.

4.6 Battery Maintenance

Battery management: Battery management is a method of keeping the cells within their desired operating limits. This is achieved by ensuring the charging rate is correct, the discharge rate does not exceed the design intent (loading of system) and the environmental conditions are correct.

Maintenance free: The term ‘maintenance free’ or ‘low maintenance’ may have lulled some users into a false sense of security that DC battery supply systems and UPS systems do not require maintenance. Detailed study of manufacturers’ information confirms that maintenance such as inspection and testing is still required. The terminology of maintenance free normally relates to the requirement to top up the battery electrolyte. For instance, if the charging condition is incorrect or one battery is faulty in a battery bank, overcharging can take place and VRLA or VRPP batteries will gas off. Also, if the temperature conditions have changed due to ambient or internal ventilation conditions (fan failures or blocked air inlets or outlets), batteries will overheat and can fail.

Maintenance of wet cell (flooded) open vent: This is the standard lead acid or nickel-cadmium battery; manufacturers’ information will state the maintenance requirements inclusive of inspection and testing periods for various operational conditions. These requirements will vary depending on the battery technology and type.

Maintenance of wet cell (flooded) advanced technology: Advanced battery technology, both in lead acid and nickel-cadmium batteries, has proven to be reliable over a period of time. Manufacturers’ information states the maintenance requirements inclusive of inspection and testing periods for various operational conditions. These requirements vary depending on the battery technology and type.

Maintenance of valve regulated lead acid: VRLA batteries (both AGM and gel types) still require maintenance. Manufacturers’ information states the maintenance requirements inclusive of inspection and testing periods for various operational conditions. These requirements vary depending on the battery technology and type. The construction and installation conditions should also be considered;

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for instance, the UPS manufacturer instruction manual will not consider whether the UPS system has been housed in another panel as is often the case with ruggedised units.

Battery storage: Figure 8 shows how battery capacity may reduce with time in storage at various temperatures. Actual performance will vary from one battery model to another.

Figure 8 – Reduction in battery capacity with time in storage at various temperatures

4.7 Battery Inspection

Inspection: The inspection of batteries should be carried out on a regular basis. Visual inspection can highlight burned connections, battery cell distortion or cracked case. Also, this type of inspection may be combined with checking the temperature (heat status) of the cells within the battery bank.

Heat status tests: Thermal imaging can be utilised to check for ‘hot spots’ which would indicate points of high thermal stress in the cell or the battery pack. These tests can assist in the identification of problems such as overheating, inadequate air flow and interference from neighbouring cells or heat from other components. The images can also be used to determine the best location for temperature sensors. Specialised thermal imaging cameras can be used to carry this out. A simple test can be carried out by a laser thermometer or similar handheld device. One problem with a heat status test is that batteries on a float charge may not draw sufficient current to reveal any issues. It is common for very large land based UPS installations (say 250kVA to 750kVA) to use a ‘ductor’ to test battery interconnections.

4.8 Battery Load Testing and Alternatives

General information: Battery testing is a specialist subject and the information presented below has been developed from a report prepared on this subject for NDC by Norco Energy using information taken from the public domain. Information reviewed in the process of preparing this guidance highlighted that battery testing has an important role in establishing battery condition and therefore reliability. If battery condition is not known then battery backup systems have no known level of reliability.

For most applications, the load test of a battery is the most efficient and most effective demonstration of fitness for service. However, alternative test methods have been developed in the last few years which are gaining acceptance and which can be performed more conveniently. Such testing could be used to supplement the traditional load bank test.

Load testing: Using a UPS’s own consumers as the test load is the most common way to confirm battery endurance. Such tests are typically carried out at annual DP trials and field arrival trials. This

IMCA M 196 15 type of testing provides confidence that UPS batteries have the necessary endurance but provides little in the way of diagnostic information about the long term health of the battery bank.

Discharge testing: Discharge testing is the traditional way of testing battery banks. This type of testing is intrusive and involves isolating the battery from its system and connecting it to resistive load- banks. Each cell is tested and its performance compared against manufacturer’s specifications. The data from all of these tests is then electronically recorded and analysed by engineers. Historical data is combined with the latest test results to predict possible cell failures and make recommendations for prolonging battery life. Replacement cells and/or repairs are then provided where necessary.

Conductance testing: Conductance testing is a modern alternative to discharge testing and has recently been added to the IEEE draft standard for testing sealed valve regulated lead acid batteries. Many battery manufacturers have adopted conductance testing. The Midtronic’s conductance tester has found acceptance amongst a range of battery users including major telecommunications companies.

4.9 Conductance Testing FAQ

Increased awareness of conductance testing has generated questions about application and methodology. The following are answers to some of the most frequently asked questions.

What is Ohmic testing technology? In simple terms, Ohmic battery testing technology refers to a range of techniques based on Ohm’s Law, which expresses the relationship between voltage, current and impedance in an electrical circuit.

For a purely resistive circuit, Ohm’s Law can be expressed as follows: Volts (E) = Amperes (I) x Ohms (R). If any two of the three values of voltage (Volts), current (Amperes) or resistance (Ohms) are known, the third value can be calculated using the above expression. Thus, Ohmic testing technology attempts to use voltage and current measurements to determine the resistive characteristics of a battery. A higher than expected resistance equates to a reduced ability to produce current.

What is conductance? Electrical conductance is a measure of how easily electricity flows. Test results show that, for low frequency measurements, the conductance of a battery is an indicator of battery health and has a linear correlation to the battery’s timed-discharge capacity test result. Thus a conductance measurement can be used as a reliable predictor of battery end-of-life.

Why use conductance testing? Conductance testing offers advantages over other types of battery testing. Voltage and specific gravity measurements are not predictive. Timed discharge testing is very time-consuming and expensive. Other forms of impedance testing may not correlate directly and linearly with timed-discharge capacity.

How is the conductance test performed? Test set leads are connected to the positive and negative posts of the cell or battery under test, a measurement is taken in a matter of seconds. There is no need for additional leads to be connected to the ends of the string or for clamp-on current measurements. Testing can be carried out when the battery system is online and at various states of charge.

How can conductance readings be used? The conductance tester gives a quantitative measurement in Mhos (or Siemens) as well as a qualitative indication of battery health (percent or reference) related to a standard.

Can conductance testers measure the condition of sealed valve-regulated batteries as well as flooded cells? Correlation studies have been performed on a significant number of valve regulated cell types. These studies have shown that conductance test results are very predictive of battery timed discharge capacity, while voltage measurements are shown to be of little value. Data for gelled batteries is also available.

What kinds of batteries can be tested utilising conductance? Typically, any 2-12 Volt, lead- acid 5-2000 ampere-hour cells can be tested.

Can nickel-cadmium (NiCad) batteries and cells be tested utilising conductance? The instrument will accurately measure the voltage and conductance of NiCad batteries. Conductance testing will measure and identify gross failures of NiCad batteries. The instrument will report hard

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shorts identified through low voltage and is a useful tool in testing the application of NiCad battery systems. The feature of forecasting the failure of cells is more challenging when testing NiCads. Due to the nature of their construction and chemistry, all NiCads will measure consistently (good) until there is a failure indicating the end of life. The instrument will indicate this failure after the fact, a limitation that is true of all Ohmic measuring devices, including all existing impedance and resistance testers on the market. The instrument contains a low voltage alarm, which is set by the user to a minimum of 1.50 Volts/DC cell. This will trigger an audible alarm when testing single cell NiCads falling below the voltage benchmark. Additionally, the instrument will not test any battery or cell where the measured voltage is below 1.0 Volts DC, which would include any badly discharged or shorted NiCad cells.

Has conductance testing been proven and accepted by the international community? Extensive data has been gathered by the global telecommunications industry, battery manufacturers worldwide, international rail and transportation providers and the electric power industry. This data has been presented to the IEEE Standards Committee which now includes conductance testing in its draft standard for testing sealed valve-regulated batteries. Additionally, the data has also been presented to the International Lead Zinc Research Organisation, the Battery Council International and the International Telecommunications Energy Conference.

Does battery temperature affect conductance measurement? The actual temperature of the battery needs to be considered when making a conductance test. Battery conductance reference values (or baselines) assume the optimal battery operating temperature of 77° Fahrenheit (25° Celsius). A calculation can be made to compensate for temperature variation. Conductance testers can automatically calculate the change in percent of reference.

4.10 Battery Charging

General: Battery chargers and battery charge levels can be summarised as two basic categories.  Battery chargers that can supply system load current, trickle (float) levels and boost levels. These systems are sometimes called rectifier control units;  Battery chargers that supply trickle (float) levels.

Direct current supply systems: The battery charger (rectifier control unit) supplies the system load and trickle (float) charge to the battery bank, if the system has been operating on battery power and the battery voltage has dropped. When the mains AC power is restored the battery charger will supply the system load and recharge the batteries, the battery charge condition may change from trickle (float) to boost mode depending on the battery voltage level, the battery type and the settings of the battery charger. Typically, a 110V DC system may boost charge at 138V DC.

UPS supply systems with VRLA batteries: The battery chargers supply the trickle (float) charge to the battery bank. If the system has been operating on battery power and the battery voltage has dropped, the battery charger will trickle (float) charge the battery bank when the mains power is restored.

Unapproved chargers: Unapproved battery chargers may be found on installed systems where different manufacturers’ equipment is installed or where retrofit work has taken place.

Trickle (float): A trickle charger charges the battery slowly, normally at the self-discharge rate; this method of battery charging is the slowest method of charging. Batteries can be left in a trickle charger indefinitely to keep the battery ‘topped up’ but not overcharged.

Boost charge: This is a method of fast charging a battery (or battery bank) from a low battery terminal voltage. This is normally one element of a battery charger and research carried out for this guidance document suggests this feature being applicable to wet cells only.

Intelligent chargers: An intelligent charger will monitor the battery voltage change (may also measure temperature) and time under charge to determine the optimum charge current. This type of charger is often referred to as a ∆V or delta-V charger. Charging is finished when a combination of the voltage (may be temperature) and or time indicates that the battery is fully charged. An intelligent charger may fast charge a battery up to about 85% of its maximum capacity in under an hour and then switch to trickle charging.

IMCA M 196 17 Pulse chargers: Direct current pulse charging technology requires a strictly controlled pulse rise time and width. This type of technology claims to work with any chemistry of batteries, including LA or NiCad wet cells and VRLA and VRPP batteries. Although this type of charger is not common in commercial marine applications, it has been installed on some DP vessels.

Safety systems: Protection and alarm systems within the battery charger will ensure that batteries are not over- or under-charged.

Battery failures due to inappropriate charging: The use of approved and intelligent chargers combined with safety systems will not extend battery life but will ensure that the battery life is not reduced by inappropriate charging or fault conditions. From the survey information and NDC’s experience, the level of this effect cannot be identified; however, from information collated, inappropriate charging and lack of safety systems is listed as a high battery failure effect.

4.11 Battery Cell Temperature

VRLA battery cell temperature: This is the most significant factor affecting battery lifespan. Manufacturers state what the battery lifespan effect will be in respect of elevated temperature. Research carried out in the preparation of this guidance document suggests that this value is normally 20° Celsius. At best, battery lifespan will decrease 20% per 5°C increase above nominal (20°C), see Figure 9 and Figure 10. Some literature reports an even greater effect on lifespan.

Battery temperature: This may be affected by various factors such as ambient temperature, battery bank cell layout, cooling failure (fans, etc.) and charge/discharge rate conditions.

Figure 9 – Reduction in battery capacity with operating temperature

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Figure 10 – Effect of temperature on capacity ratio

IMCA M 196 19 5 Application of UPS and DC Supplies Onboard Vessels

5.1 General

Uninterruptible power supplies are used as an independent source of clean power for a wide range of functions on modern vessels. Information received from IMCA members in the process of preparing this guidance suggests that modern vessels can have as many as 25 dedicated UPSs and DC power supplies in their propulsion and vessel control systems alone.

Applications for UPSs can be loosely divided into four main categories as shown below.  control system;  communication systems;  safety systems;  emergency systems.

There are also some specialist roles for UPS supplies including pre-charging the DC links of thruster variable speed drives as part of blackout recovery.

Applications for DC power supplies with battery backup included engines, thrusters and switchboard control systems. These applications are discussed in Sections 3 and 5.6.

5.2 UPS for Control Systems

Typical control system applications include:  engine control systems;  propulsion and thruster controls systems;  vessel and power management systems;  DP systems;  crane control systems;  drilling control systems including AHC;  pipelay control systems.

For control systems, a UPS has three roles to perform:  It must provide a clean source of power to the control system to isolate it from mains-borne interference such as spikes and harmonics and undesirable fluctuations in frequency and voltage which may occur in a vessel’s power systems. Note: Not all types of UPS are able to operate properly from poor quality power.  It must provide power to the control, alarm and monitoring systems when the main power is unavailable such as during a blackout. In this role, the UPS provides power for remote control of the plant to allow automatic or manual blackout recovery to proceed rapidly.  It must provide a warning to the vessel’s operators that power is being drawn from the batteries to allow time for a graceful transfer to another control system or to make safe the work in progress before control is lost.

The required battery endurance depends very much on the application. In many cases, the battery may only be required to supply the load until an emergency generator connects in a matter of a few minutes or less. In other cases, a much longer period of autonomous operation may be required. Control system UPSs on DP vessels of Equipment Class 2 and 3 are expected to last at least 30 minutes on battery supply but this requirement also appears in some main class rules as a ‘general requirement’ for standby power supplies.

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5.3 UPS for Voice and Data Communication Systems

In communication systems, the primary role of the UPS is to provide conditioned power to a range of essential and non essential consumers. However, during an emergency, the UPS must provide an independent source of power to maintain such modes of communication systems as may be required to effectively manage an emergency situation when the main power system is unavailable.

Typical uses of UPS power from communication systems include:  satellite communications;  radio systems;  public address systems;  general alarm systems;  telephone exchanges;  intercoms;  DP alert lamps;  diving alert.

5.4 UPS for Safety Related or Critical Systems

UPSs or battery systems may be used to support the operation of safety related systems such as:  fire detection systems;  gas detection systems;  ballast control systems;  emergency shutdown systems;  fire damper control panels;  watertight door control panels;  emergency riser disconnect systems.

Some classification societies require isolation of UPS batteries during an emergency shutdown. Only UPSs for certain applications and in certain locations must have their batteries isolated and the reader is directed to the appropriate classification society rules for details.

5.5 UPS for Emergency Systems

There are definitions of emergency systems in classification society rules, SOLAS and related publications. These specify the minimum amount of time for which certain emergency functions must be available when the main power system is unavailable. The size of many of these functions, such as bilge and fire pump, require the emergency generator to be running but other functions may be supported by a UPS at least in the short time it takes the emergency generator to start and connect.

5.6 DC Supplies with Battery Backup – Application to Generation Systems

Generation systems application: The generation systems can be sub-divided into six basic systems.  diesel engines;  governors;  automatic voltage regulators (AVR);  switchgear control;  protection;  metering internal and external.

IMCA M 196 21 Diesel engines: Diesel engine auxiliary supplies are normally 24V DC or 110V DC with 24V DC being the most common supply voltage. The loss of auxiliary supply will result in loss of engine control systems and the engine may shut down with inter-trip interface to the DG breaker. In other installations, the engine may continue to run with alarm to reduced protection.

Governors: Governor auxiliary supplies are normally 24V DC but some electric governors require a 40V DC supply to the actuator. The loss of auxiliary supply normally results in loss of governor control systems and therefore engine speed reduction with inter-trip interface to the DG breaker.

Automatic voltage regulators (AVR): Auxiliary supplies for AVRs are normally 24V DC or 110V DC. The loss of auxiliary supply can result in failure of the AVR and therefore alternator excitation. AVRs can be categorised into five sub-divisions depending on how auxiliary supplies are utilised:  analogue AVRs with no requirement for external DC supplies; this type of AVR normally utilises the DC supply system from the PMG and/or generator VT supply to provide the interface capability to trip the AVR;  analogue AVRs with a requirement for external DC supplies; this type of AVR normally utilises 24V DC or 110V DC to provide the interface capability to trip the AVR;  digital AVRs with no requirement for external DC supplies; this type of AVR normally utilises the AC supply system from the PMG and / or generator VT supply to provide the interface capability to trip the AVR;  digital AVRs with a requirement for external DC supplies; this type of AVR normally utilises 24V DC or 110V DC to provide the display, control and field build up power. The same supply is also used to provide the interface capability to trip the AVR.

Switchgear control: The control of the switchgear consists of breaker close, open, under-voltage, locking magnet coils, etc. The control circuits may be relay logic control or PLC control within a multipurpose protection and control device or a combination of both. The auxiliary supplies are normally 24V DC or 110V DC with the latter being the most common supply voltage. The loss of the control auxiliary supply normally results in the circuit breaker being unable to trip as the majority of switchgear breakers do not have DC under voltage coils

Protection: Protection devices can be arranged as a series of dedicated protection relays or a multipurpose protection and control device or a combination of both. Auxiliary supplies are normally 24V DC or 110V DC with the latter being the most common supply voltage. The loss of the control auxiliary supply normally results in the protection systems failing as set; however, it is not uncommon for a trip output to be given on restoration of auxiliary supplies. The supply is normally the same supply as used for the breaker and metering control.

Metering internal: Internal metering is normally supplied from transducers which have the same supply as the protection and control equipment. It is also becoming common for the metering to be supplied from the multipurpose control and protection device.

Metering external: External metering is normally supplied from transducers which have the same supply as the protection and control equipment. It some instances, the metering may be supplied from the multipurpose control and protection device.

Effects of auxiliary supply failures: The effects of auxiliary supply system failures should be analysed to ensure that a dangerous condition does not develop. This may require allocation of certain equipment to different auxiliary supplies. The following basic rules can be applied:  Engines, governors and AVRs should not be supplied from the same auxiliary supply as the circuit breaker controls. If the generator circuit breaker cannot trip because of auxiliary supply system failure, a large active and reactive condition could develop which may damage the alternator and/or diesel engine.  The external metering should not be supplied from the same auxiliary supply as the circuit breaker controls/protection relays. Auxiliary power failure could result in the power management system not knowing the power available from connected generators and being unable to trip the main circuit breaker.  As the majority of main generator circuit breakers have only a shunt trip coil, these should be supervised to ensure trip circuit integrity and advise the management system to request the operator to remove the generator from the system using the mechanical trip facilities.

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6 Integration into Vessel Systems

6.1 Electrical Considerations

There are three basic considerations:  Input power – can the UPS operate successfully from the power system to which it is to be connected?  Duration of independent operations – What stored energy capacity is required? – Typically, 30 minutes at full load but this may be very application specific.  Output power – Is the quality and quantity of the power the UPS delivers adequate for all operating conditions and modes of operation including the ability to deliver sufficient fault current to ensure selectivity?

When answering the questions raised above, it may be useful to consider three characteristics of UPSs and their loads:  Power factor: This is the ratio of the real (kW) power consumed by a load to the apparent (kVA) power. Loads associated with computer systems can have a poor power factor created by the use of switched mode power supplies.  Crest factor: This is the ratio of the peak current to the RMS current drawn by a load. Many loads associated with computer equipment draw non-linear current from the supply. The result of this is that the UPS may have to deliver current peaks well in excess of the RMS current rating of the load.  Surge factor: Many loads have an inrush current or starting current demand. The UPS must be capable of delivering the necessary current surge.

Once again, it is important to note that the design of commercial UPSs for shore-based use is based on certain assumptions about the nature of the loads that will be supplied. Manufacturers of quality products will allow adequate margins for the factors discussed above in the design of their UPSs. However, for marine applications, it may not be acceptable to rely on these margins when specifying a UPS and the requirements of the actual loads to be supplied should be confirmed and discussed with the UPS supplier.

6.2 Run Time

Figure 11 shows how the UPS run time (determined by the battery endurance) varies with the load on the UPS. The data in Figure 11 is based on the performance of a 3kVA online UPS from a major US manufacturer. The relationship between load and run time is highly non-linear but when the UPS is loaded to practical values (75%), the relationship between load and run time is approximately linear over about the top 50% of its range. Three battery arrangements are shown. Trace 1 shows the endurance of the UPS with the standard battery pack. Traces 2 and 3 show how the addition of extra batteries increases the run time. As Figure 12 shows, this UPS would not provide the 30 minute run time required for DP Class 2 and 3 vessels at 75% loading as it is only capable of 20 minutes at this load. Adding a second battery pack increases the 75% load run time to 80 minutes which should allow some margin for additional loads being added and battery ageing.

IMCA M 196 23 75% Load

3

2

1

Figure 11 – Load against run time for 3kVA, 2100W online UPS

1 2 3 75% Load

DP 2 & 3 Figure 12 – Load against run time for 3kVA, 2100W online UPS (expanded)

Figure 13 shows the relationship between apparent power and run time for a unity power factor load and a load with 0.7 power factor (also taken from manufacturer’s data). As might be expected, the load with the poor power factor has a longer endurance because, for the same apparent power (VA), it is consuming less energy (kW). By comparing a few points on the graph it is possible to show that the run time is largely determined by the real power consumed in each case (e.g. 1000VA is equivalent to 700W with a 0.7 pf and 53 minutes). The important consideration with poor power factor is that

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the VA rating of the UPS cannot be exceeded even if the real power consumed is well below the UPSs rating.

2

1

700W

Figure 13 – Effect of power factor on run time

6.3 Harmonics

Power system harmonics can be a significant problem on vessels with large non-linear power electronic loads such as variable speed drives for thrusters, drilling, pipelaying and cranes. In simple terms, harmonics can be described as unwanted distortions in the power system voltage and current waveforms which can cause premature failure of major components and malfunction of control systems. There are several approaches to minimising the effects of harmonics including supplying sensitive equipment from UPSs but UPSs themselves are not entirely immune to the worst effects of harmonic distortions. Although classification societies set limits, levels of harmonics in marine power systems can be much higher than that allowed by shore-based utilities. Commercial UPSs generally have filters designed to reduce the effects of harmonics on loads. This is particularly necessary for standby UPSs because the load is supplied mostly from the main AC input. Similar filters can also be found in online UPSs which switch automatically to their bypass on fault or overload. Experience shows that these filters may not be able to cope with the level of harmonics found in marine systems and may burn out as a result. If the intended application requires the UPS to operate from a supply with a high harmonic content this requirement should be discussed with the UPS supplier.

IMCA M 196 25

Figure 14 – Harmonic distortion in 6.6kV supply voltage

Online UPSs that use controlled rectifiers for battery charging may be badly affected by commutation notches on their input power supply which are associated with large 6 and 12 pulse drives used for drilling and thrusters. These notches may appear as false zero crossings causing the malfunction of the battery charger to the point where UPS batteries are not properly charged reducing the run-time in battery mode.

6.4 Interface Systems Considerations – Alarms and Monitoring

Alarms: In order that UPSs can make a useful contribution to the safe and reliable operation of a vessel, they need to provide the vessel operator with a useful range of information about their condition and configuration. As a minimum, each UPS and DC power supply should have the following alarms:  ‘On battery supply’ – This alarm should be designed to indicate that load current is being drawing from the batteries. Some UPSs only have a ‘main supply failed’ alarm which is useful but does not provide the same degree of security as actually monitoring the battery current.  ‘Battery disconnected’ – This alarm indicates that the battery has become disconnected. Some classification societies also require an alarm to indicate that the battery protection has operated but this does not provide the same level of security as sensing the connection to the battery.  ‘In bypass mode’ – This alarm should indicate whether the UPS is currently in manual or automatic bypass mode which may prevent it supplying the load during a blackout.

Monitoring: Modern UPSs can provide a large amount of information on their own status and performance. Limited information can be accessed by way of dry-contact relays in some applications. Much more can be obtained by way of serial communication links.

6.5 Dual Supplies to UPSs

It is common practice to provide UPSs used as part of the vessel’s control and automation system with a main and a backup supply by way of either a manual or automatic changeover switch as shown in Figure 26. Typically, the normal supply comes from the main power systems and the backup supply is from the emergency power systems. For DP vessels, class may require that the normal supply is the main power system. However, it is useful for black ship start, lay-up, etc. if the UPS batteries can be charged from the emergency generator. It can also offer a degree of protection against a premature battery failure if the UPS automatically changes over to the supply from the emergency generator as

26 IMCA M 196

soon as it becomes available. However, as with any connection between systems, care must be taken to design the changeover switch so that it will not transfer a fault which risks causing a blackout or severe voltage dip on both sources of supply if the UPS or changeover switch is faulty.

6.6 ESD Requirements

Some classification societies may require that UPS batteries are disconnected on activation of certain levels of the emergency shutdown system (ESD). DNV have advised NDC that the requirement for shutdown of UPSs in its rules is related to abandon platform shutdown/abandon vessel shutdown on a mobile offshore unit. The origin of the requirement is in the DNV Offshore Rules 2008, DNV-OS- A101, Figure 1. This figure lists, among other things, which systems can remain active after initiation of such a shutdown level (UPSs are not included in this list). There are exceptions to this requirement related to mobile offshore drilling units (MODUs) which must, as a minimum, comply with IMO MODU Code Sec. 6.5. ‘In all cases the UPSs and location of such shall comply with the requirements of DNV-OS-A101 Sec.5 F104 which state that:

‘Uncertified (Ex) electrical equipment may be left operational after ESD or gas detection affecting its area of location, provided that the ventilation to the room where the equipment is located is efficiently isolated. Typical living quarter design will meet this requirement, other enclosed spaces will be specially considered.’

There are at least two important issues associated with this requirement:  UPSs must be supplied with a means to disconnect the UPS batteries remotely.  Any UPS required for propulsion or vessel control should be able to start and provide AC power from its batteries without the main input supply being present. This feature is important to allow the vessel to be ‘black started’ quickly and efficiently if the ESD is cancelled or after periodic testing of the ESD. This may seem like an obvious function but UPSs have been designed that cannot do this.

6.7 UPS Systems DC Power Supplies – Fault Levels and Protection Discrimination

Fault level calculations: Classification societies require that converters used as power supplies (which includes UPSs) should be able to provide enough fault current to operate over current protection selectively. Calculations should be carried out to determine the fault levels of the system. The fault level study should be inclusive of the battery bank, charger and or inverter contributions, where appropriate, but most commercial UPSs used in marine applications appear to transfer faults to their bypass. The impedance of filters and other line conditioning equipment may have a significant effect on fault current levels.

Voltage decrement: The voltage drop and duration under fault conditions should be calculated if it is intended that consumers should be able to ride-through the disturbance associated with clearing a ‘branch’ fault.

Protection co-ordination: The protection system, i.e. fuses, MCBs and electronic protection devices within the chargers and or inverters should be considered. Fault level discrimination is generally not given a great deal of consideration in small power systems, including UPSs, and the focus is generally on ensuring safety rather than continuity of supply.

6.8 Dual Voltage UPSs

One arrangement that may present problems, if not carefully considered, is the dual voltage UPS. It is often the case that marine power plants require 220V AC and 24V DC supplies with battery backup for control applications and these units may be provided by shipyards as a cost effective solution. In some cases these units are created by connecting a 24V DC power supply onto the output of the 220V AC UPS such that the batteries in the AC UPS provide the battery backup for both voltages. The difficulty with this arrangement arises when a fault occurs in the 24V DC distribution and the DC power supply does not have sufficient fault capability to operate the over-current protection selectively. The problem can be overcome by providing battery backup at the 24V DC level to provide the necessary fault current but this may be no more cost effective than providing a separate 24V DC system with its own battery bank. If the number of DC consumers is small, providing a 24V DC power supply off the UPS for each consumer is a possible alternative.

IMCA M 196 27 6.9 Common/Summary Alarm

It is tempting to route all UPS alarms into a single common or summary alarm to save I/O. However, care must be taken to distinguish minor events from more serious conditions. Most UPSs provide an audible alarm indicating that the battery is in discharge. This is a useful feature to provide a quick confirmation. The following alarms should be separate:  Battery in discharge – Time on UPS is limited.  UPS in bypass mode – System is not properly configured.  A ‘common’ UPS fault alarm may be used to indicate other conditions.

It is important to discuss alarm requirements with manufacturers prior to purchase and ascertain whether the unit can be made application specific.

28 IMCA M 196

7 Strategies for UPS and DC Distribution

7.1 General

The provision of UPS power to consumers is an important issue on any type of vessel but it is particularly important on vessels where the power plant or control systems must be fault tolerant. Typical applications include vessels with class notation for redundant propulsion or DP. There is a surprisingly common misconception that by supplying critical equipment from a UPS it can be considered not to fail. This is not correct. A UPS and its loads should be considered to fail like any other piece of electronic equipment.

Distribution strategies may be described as centralised, distributed or hybrid solutions with elements of both approaches but, whatever strategy is adopted, it should support the redundancy concept. Those elements of a propulsion system that typically require UPS power include:  vessel control systems including power management and DP;  power generation systems including engines and their auxiliary systems;  power distribution systems;  thrusters and steering gear.

The propulsion arrangement shown in Figure 15 is not particularly important but could represent a large DP Class 2 ROV support vessel or a medium sized pipelayer. The principles under discussion apply equally to any other arrangements including propulsion systems for DP semi submersibles.

THRUSTERS AND CONTROL ENGINES AND POWER DISTRIBUTION PROPULSION SYSTEMS SYSTEMS AUXILIARY SYSTEMS SYSTEMS STEERING GEAR

T5

G1 CONTROL R1 SYSTEM A G2 SWBD T3 T4 T1 T2 G3

G4

T6 G5 SWBD

R2 G6 CONTROL SYSTEM B

FIELD STATION OR CONTROL SYSTEM

Figure 15 – Parts of a redundant propulsion system requiring UPS

7.2 Minimum Requirement

For a vessel with a simple two way split in its redundant propulsion system (such as that shown in Figure 15) all that is required for fault tolerance are two main UPSs each with a distribution system supplying the appropriate parts of the propulsion system such that failure of either UPS does not cause the loss of more machinery than the vessel’s worst case failure design intent (WCFDI). In other words, if one UPS fails, the vessel should be able to hold position using the surviving propulsion and control system equipment. Note that automatic bypasses in UPSs cannot be considered as contributing to redundancy because there is always a possibility that the static switch or some part of the distribution systems might fail. Although Figure 16 shows the minimum requirement for fault tolerance, classification societies may require additional features such as emergency supplies to steering gear.

Variations on this simple arrangement may include providing a ‘backup’ raw supply to control systems by way of local auto changeovers or providing individual internal battery backup in control systems

IMCA M 196 29 where the AC power is converted to low voltage DC. Note that introducing changeovers into any redundancy concept introduces other risks and needs very careful consideration. It is often the case that UPS power distributed at 220V AC or 110V AC is transformed and rectified to 24V DC at each consumer. The argument for not distributing DC directly throughout the vessel is related to the large cable size required to distribute 24V DC without unacceptable voltage drop.

A more common and more practical UPS distribution arrangement for larger vessels is shown in Figure 17. This arrangement introduces an additional fore-aft split into the port-starboard split required for redundancy. This four-way split does not improve the vessel’s overall worst case failure which is still determined by the two way split in the power generation system but does reduce the impact of a UPS failure and leaves the vessel with greater manoeuvring capability. The main reason for further subdivision of this type is to reduce the length of cable runs and site UPS distribution boards closer to the equipment they supply.

UPS A

T5

G1 CONTROL R1 SYSTEM A G2 SWBD T3 T4 T1 T2 G3

G4

T6 G5 SWBD

R2 G6 CONTROL SYSTEM B

UPS B

FIELD STATION OR CONTROL SYSTEM INDICATES SPLIT IN REDUNDANCY CONCEPT

Figure 16 – Minimum requirements for UPS distribution

30 IMCA M 196

UPS A UPS C

T5

G1 CONTROL R1 SYSTEM A G2 SWBD T3 T4 T1 T2 G3

G4

T6 G5 SWBD

R2 G6 CONTROL SYSTEM B

UPS B UPS D

FIELD STATION OR CONTROL SYSTEM INDICATES SPLIT IN REDUNDANCY CONCEPT

Figure 17 – More practical UPS distribution with port/starboard and fore/aft split

7.3 Distributed UPS Arrangement

An increasing number of designers now take the view that a distributed UPS strategy offers the best solution. Some even go so far as to specify that if a particular vendor’s equipment requires UPS power then a suitable UPS should be included with the equipment such that it can be supplied with raw power from the vessel’s power distribution scheme.

The distributed approach has advantages for vessels with a multi-way split in their redundancy concepts where it is necessary to reduce the impact of the worst case failure to a single engine or thruster. However, if each manufacturer provides a UPS for each piece of equipment that is redundant with respect to any other then there may be a very large number of different types of UPSs all with different batteries which will need testing, maintenance and replacement as shown in Figure 18. A compromise would involve grouping together equipment which serves a single engine or thruster and supplying all of that equipment from a single UPS. This provides the necessary level of independence between redundant elements and reduces the number of UPS units required but great care should be taken not to common up supplies for protection systems and control systems. For example, if an AVR, governor and generator protection relay are supplied from the same source, the protection relay will not be able to trip the generator on detection of an AVR or governor fault. If this arrangement cannot be avoided then loss of UPS power must initiate the tripping action by way of a backup supply. It is also preferable to separate control and alarm functions but the advent of distributed vessel management systems means that these functions are generally provided by a common field station so the UPS does not introduce any more commonality. Figure 19 shows how this might be achieved for a variable speed thruster. Providing UPS power to several different vendors’ equipment does require more integration engineering than if the vendors supply their own UPSs.

The distributed approach also has advantages for DP Class 3 designs where there is a need to reduce the risk of transfer of fault associated with fire and flood in one compartment. The strategy of closely associating a UPS with groups of equipment related to one redundant element of the design fits in well with the compartmentalisation scheme for DP Class 3 vessels.

IMCA M 196 31 24Vdc 110Vdc A C E G I K A A

T5

G1 CONTROL R1 SYSTEM A G2 SWBD T3 T4 T1 T2 G3

G4

T6 G5 SWBD

R2 G6 CONTROL SYSTEM B

24Vdc 110Vdc B D F H J L B B

FIELD STATION OR CONTROL SYSTEM

Figure 18 – Distributed UPS scheme

AUXILIARY UPS POWER

)

VESSEL THRUSTER THRUSTER MANAGEMENT CONTROL CONTROL ) ) ) ) ) ) FIELD STATION UNIT FIELD STATION THRUSTER BILGE THRUSTER STEERING CONTROL & FEEDBACK VENTILATION MANUFACTURER’S SPEED CONTROL AND & FEEBACK ALARMS CONTROL SYSTEM STEERING PUMP ON/OFF LUBE OIL PUMP ON/OFF DRAIN PUMP ON/OFF

DE-IONISED WATER COOLING UNIT

MCC/USB FOR MAIN VSD MOTOR THRUSTER POWER AUXILIARIES

THRUSTER HYDRAULIC PUMPS VSD DRAIN PUMP STARTER LUBE OIL STARTER Figure 19 – Grouping UPS consumers for a single thruster

7.4 Centralised UPS Systems

There is still strong support amongst some designers for large centralised UPS schemes. The advantages are related to the perceived higher quality and reliability of large UPS systems. In such a scheme, there is generally only one type of UPS manufacturer and one type of battery to be considered in maintenance programmes. This is a worthwhile consideration in any UPS scheme.

In DP vessels with multi way splits and low impact worst case failure design philosophies, a centralised approach results in an arrangement like that shown in Figure 20 in which each piece of equipment requiring UPS power receives a supply from two large centralised UPSs. Although it is possible to arrange for UPSs to run in synchronism with each other and load share, the normal way in which dual supplies from UPSs are made common within equipment is by rectifying and conversion to low voltage DC such as 24V DC. In other cases a mechanical auto-changeover is provided particularly if AC power is required. The mechanical changeover does not provide continuity of supply on UPS failure and so the redundancy concept should accept that the equipment may have to be restarted on failure

32 IMCA M 196

of one UPS. Where auto-changeovers are used, it is important that they cannot transfer a fault from one supply to another. It should also be possible to monitor which supply they are connected to and that the backup supply is present to increase confidence that the equipment will be available after a fault and that equipment is distributed evenly between the two supplies so that it is not necessary for everything to changeover on loss of one UPS.

It may be very difficult to make redundant centralised UPS schemes comply with the DP Class 3 requirements of some Classification Societies. Requirements in IMO MSC 645 to prevent transfer of fault can be interpreted as meaning that supplies originating from power systems intended to provide redundancy cannot enter the same fire subdivision or watertight compartment even if they serve the same piece of equipment (if both are live at the same time). If it is intended to implement a centralised redundant UPS scheme on a DP Class 3 design then the concept should be discussed with the classification society at an early stage in the design process.

UPS A

T5

G1 CONTROL R1 SYSTEM A G2 SWBD T3 T4 T1 T2 G3

G4

T6 G5 SWBD

R2 G6 CONTROL SYSTEM B

UPS B

FIELD STATION OR CONTROL SYSTEM

Figure 20 – Centralised redundant UPS scheme

7.5 Backup UPS

A variation on the simple two or four UPS scheme described in Figure 16 and Figure 17 is shown in Figure 21. In this arrangement, UPSs A and B are designed to transfer to UPS C on detection of inverter failure rather than their backup supply. This arrangement does not improve the overall worst case failure which is still determined by the two-way split in the UPS power distribution scheme. However, it recognises the fact that UPSs have a finite reliability and losing one of the two UPSs is more likely than losing the entire distribution scheme. Losing one of the two UPSs shown in Figure 16 severely disables the vessel to the point where position critical operations would have to be terminated until the UPS can be repaired. By providing a backup UPS (UPS C) as shown in Figure 21, operations can continue without interruption while the faulty UPS is repaired. Static switches are generally used to create the changeover.

As UPS C forms a common point between the two distribution systems, care should be taken to ensure that a fault in UPS C cannot affect the operation of both UPS A and UPS B. As some UPSs transfer load to their auto-bypass to operate over-current protection, some thought would have to be given to ensuring that over-current protection operates effectively when the bypass mode is effectively a second UPS.

IMCA M 196 33 MAIN SWITCHBOARD A EMERGENCY SWITCHBOARD MAIN SWITCHBOARD B

) ) )

UPS A UPS C UPS B

STATIC STATIC SWITCH SWITCH

UPS UPS DISTRIBUTION DISTRIBUTION

Figure 21 – Backup UPS

7.6 Strategies for DC Power Supply Distribution

The same principles that have been discussed for UPS distribution can also be applied to DC power supplies. Typically, a traditional approach is taken to the provision of DC power for switchboards with a dedicated DC power supply for each switchboard or bus section. DC power for engine controls can be split along the lines of the overall split in the redundancy concept with groups of engines sharing a common power supply. Because of the ease with which DC power supplies can be tied together through diodes, it is quite common to find dual DC supplies to consumers. This practice introduces additional commonality between otherwise redundant elements of a propulsion system and great care must be taken not to provide paths for fault transfer. Some designers prefer to use DC to DC converters rather than diodes as this provides isolation of earth faults and some additional impedance in relation to fault transfer. Other designers prefer to provide a dedicated DC power supply for each consumer.

7.7 Cross Connection of DC Power Supplies

Direct current power supplies: Cross connections tend to be a feature of DC power systems as these supplies are easy to cross connect using diodes or DC to DC converters. Unfortunately, a short circuit fault at the common point causes a voltage dip on both power supplies and generator or thruster circuit breakers may trip before control system fuses or MCBs operate to clear the fault. Such failures are not often simulated at FMEA proving trials due to concerns over equipment damage. On occasions when such systems have been tested realistically, thrusters have tripped. See Figure 22, Figure 23 and Figure 24.

34 IMCA M 196

This arrangement meets Class but may DC DC Supply A not be sufficiently reliable if generators Supply B stop on loss of control voltage.

Control voltage bus for generators 1, 2 and 3 Control voltage bus for generators 4, 5 and 6

Figure 22 – Single supply for each main switchboard

This arrangement apparently improves DC reliability but introduces a common cause DC Supply A failure as a fault on either bus can cause Supply B the voltage on supplies A & B to dip far enough to cause generators to trip.

Control voltage bus for generators 1, 2 and 3 Control voltage bus for generators 4, 5 and 6 Figure 23 – Main switchboard supplies cross-connected

This arrangement provides the required DC DC DC DC Supply A Supply B improvement in reliability and Supply C Supply D maintainability without introducing the common cause failure.

Control voltage bus for generators 1, 2 and 3 Control voltage bus for generators 4, 5 and 6 Figure 24 – Dual supply for each main switchboard

Note that some classification societies require that there is a cross-over arrangement to allow either DC power supply to provide power to for either control bus. This can be a manual selector and remain isolated for normal operations.

IMCA M 196 35 8 Class Requirements for UPS, DC Supplies and Batteries

8.1 General

Classification societies have rules concerning the design, location and installation of UPSs and DC supplies for various supplies. The table which follows Section 8.3 lists the main requirements.

Rules for the location of batteries of different types and sizes in specialised compartment have been omitted as these are detailed and extensive and the reader is directed to the rules of the classification society in this case. Rules which apply to engine starting batteries are also omitted as not directly relevant to UPS or DC supply batteries. The wording of some rules has been paraphrased in some cases.

The purpose of the table is only to give an indication of the range of issues that must be considered to meet class requirements. In all cases, the reader should consult the appropriate year of the classification societies’ rules.

The table has been developed from the following rules:  DNV Rules for Ships –Part 4 Chapter 8 January 2008 – ‘Electrical Installations’.  DNV Offshore Standard DNV-OS-D201, January 2008– ‘Electrical Installations’.  DNV Offshore Standard DNV-OS-A101, October 2005-‘Safety Principles and Arrangements’ (latest at time of writing).  ABS Rules for Building and Classing Steel Vessels 2008.  ABS Rules Effects of Harmonics 2006.  Lloyd’s Register of Shipping, Rules and Regulations for the Classification of Ships – 2006.  Germanischer Lloyd, ‘Rules & Guidelines 2008, Rules for Classification and Construction’, I - Ship Technology, Part 1 - Seagoing Ships, Chapter 3 - Electrical Installations.

8.2 Common Requirements

As can be seen from the table below, there is some commonality between classification society requirements for UPSs. In particular, a battery endurance of 30 minutes is required by all four classification societies listed. There is also significant agreement on the types of alarms to be provided for a UPS.

8.3 Standards Organisations

In addition to classification society rules, the following international and US standards are applicable to UPSs and may be useful in the preparation of vessel specifications, etc.  IEC 62040 from which is derived BS EN 62040-3:2001 ‘Uninterruptible Power Systems (UPS)’.  NEMA Standards Publication PE 1-2003 ‘Uninterruptible Power Systems (UPS) – Specification and Performance Verification’.  IEEE Std 450-2002 IEEE Recommended Practice for Maintenance, Testing and Replacement of Vented Lead-Acid Batteries for Stationary Applications’.  IEEE Std 1188 -2005, IEEE Recommended Practice for Maintenance Testing and Replacement of Valve-Regulated Lead Acid (VRA) Batteries for stationary applications’.  IEEE Std 1184 -2006, ‘IEEE Guide for Batteries for Uninterruptible Power Supply Systems’.

36 IMCA M 196

Rule Requirement IMCA MIMCA 196 Design Issue DNV Lloyd’s Register ABS Germanischer Lloyd Battery

Minimum of 30 mins following loss of Minimum of 30 mins following loss of Minimum of 30 mins following loss of Minimum of 30 mins following loss of Capacity main supply main supply main supply main supply Voltage tolerance:15% to +30% of DC battery supply voltage nominal DC system voltage variations Voltage cyclic variation: max 5% Voltage ripple: max 10% Circuits connected to batteries above Circuits connected to batteries above 12V or above 1 Ah capacity shall have 12V or 1Ah shall have short circuit and short circuit and over-current over current protection. protection. Protection for battery circuits is to be Protection may also be required for provided at a position external and smaller batteries capable of creating a adjacent to the battery compartments. fire risk. Short circuit protection shall be located Battery protection as close as is practical to the batteries, but not inside battery rooms, lockers, boxes or close to ventilation holes.

The connection between the battery and the charger is also to have short circuit protection. Connections between cells and from poles to first short circuit protection shall be short circuit proof. Where the emergency source of Carrying the emergency electrical load Carrying the emergency electrical load electrical power is an accumulator without recharging while maintaining without recharging while maintaining battery it shall be capable of carrying the voltage of the battery throughout the voltage of the battery throughout the emergency electrical load without the discharge period within 12% above the discharge period within 12% above Where the emergency recharging while maintaining the voltage or below its nominal voltage. or below its nominal voltage. source of electrical power of the battery as required by A200. Automatically connecting to the Automatically connecting to the is an accumulator battery it (Interpretation of SOLAS Ch. II- emergency switchboard in the event of emergency switchboard in the event of is to be capable of: 1/43.3.2.1) failure of the main source of electrical failure of the main source of electrical power power Immediately supplying at least the Immediately supplying at least the essential services. essential services.

37

Rule Requirement 38 Design Issue DNV Lloyd’s Register ABS Germanischer Lloyd Each charging device is, at least, to have Where a reserve source of energy The charging facilities are to be such sufficient rating for recharging to 80% consists of a rechargeable accumulator that the completely discharged battery capacity within 10 hours, while the battery a means of automatically can be recharged to 80% capacity in not Battery charging rate system has normal load. charging the batteries is to be provided more than 10 hours. which is to be capable of recharging them to minimum capacity requirements within 10 hours. The emergency source of power shall No accumulator battery except for The emergency switchboard is to be be located above the uppermost engine starting, is to be installed in the installed as near as is practicable to the continuous deck and be readily same space as the emergency emergency source of electrical power. accessible from open deck. It shall not switchboard. No accumulator battery is to be be located forward of the collision installed in the same space as the bulkhead. emergency switchboard. An indicator The emergency source of power shall is to be mounted on the main Location be automatically connected to the switchboard or in the machinery emergency switchboard in case of control room to indicate when these failure of the main source of electric batteries are being discharged. power. The emergency switchboard shall be

installed as near as is practicable to the emergency source of electrical power. General UPS or battery systems for operation of the main power distribution shall not be located together with equipment Location necessary for the operation of the emergency power generation or distribution or vice versa

IMCA MIMCA 196

Rule Requirement IMCA MIMCA 196 Design Issue DNV Lloyd’s Register ABS Germanischer Lloyd Signboards shall be fitted in battery rooms and on doors or covers of

boxes or lockers, warning against risk for explosive gas, smoking and the use of naked lights. All batteries shall be provided with labels (nameplates) of flame retardant material, giving information on the Signs and markings application for which the battery is intended, make, type, voltage and capacity. Instructions shall be fitted either at the battery or at the charging device, giving information on maintenance and charging. Battery systems above 50V shall be marked with special visible warning signboard, i.e. ‘Warning xxx voltage’. UPS

For Converters servicing as power UPS units are to be constructed in supplies for emergency power external accordance with IEC 62040, or an bypass arrangements shall be provided acceptable and relevant national or international standard. A bypass or a second UPS in parallel is to be provided. The operation of the UPS is not to depend upon external services. The UPS unit is to be monitored. An Design and construction audible and visual alarm is to be given on the ship’s alarm system for power supply failure (voltage and frequency) to the connected load, earth fault, if applicable, operation of battery protective device -  when the battery is being discharged, and when the UPS is not operating under normal condition.

39

Rule Requirement 40 Design Issue DNV Lloyd’s Register ABS Germanischer Lloyd Electrical Power Supply Power supply failure with 3 interruptions during 5 minutes successive power breaks — switching-off time 30 s each case. with full power between breaks: combination of permanent frequency combination of permanent frequency variations of ±5% and permanent variations of ±5% and permanent voltage variations of +6/−10% of voltage variations of +6/−10% of Power supply variations for nominal nominal equipment connected to combination of frequency transients (5 combination of frequency transients (5 AC systems: s duration) s duration) ±10% of nominal and voltage transients ±10% of nominal and voltage transients (1.5 s duration) (1.5 s duration) ±20% of nominal. ±20% of nominal. voltage tolerance continuous ±10% of voltage tolerance continuous ±10% of Power supply variations for nominal nominal equipment connected to voltage transients cyclic variation 5% of voltage transients cyclic variation 5% of DC systems: nominal nominal

— voltage ripple 10%. — voltage ripple 10%. +30% to −25% for equipment +30% to −25% for equipment connected to battery during charging connected to battery during charging Power supply variations for +20% to −25% for equipment — +20% to −25% for equipment equipment connected to connected to battery not being charged connected to battery not being charged battery power sources: — voltage transients (up to 2 s duration) ±25% of nominal. Converters serving as power supplies shall be able to supply a short circuit current sufficient for selective tripping of down stream protection without Operation of protection suffering internal damage. Current limiting power supplies or power supplies limited by internal temperature may be used for single consumers.

IMCA MIMCA 196

Rule Requirement IMCA MIMCA 196 Design Issue DNV Lloyd’s Register ABS Germanischer Lloyd Standby Power Supply

Battery or UPS power shall be provided as standby power for the following: Systems required to operate in a blackout Systems required to restore normal Requirements function after a blackout Special requirements Note a UPS alone shall not be regarded as providing redundancy when two mutually independent supplied are required. Once source may be a UPS. Switchboard Control Supplies from Battery Systems The control power can be supplied Sources of switchboard from a battery when the switchboard control power can be divided in two

Number of sources of An independent control power supply

control power must be provided for each bus section. Cross over facilities must be provided so that the battery system for each bus Cross over section can supply other the control power for other bus sections. Each battery system must have sufficient stored energy for two operations of all the components connected to that section of Number of operations switchboard. In the case of switching from battery source off circuit breakers, it must be possible to trip all circuit breakers simultaneously without unacceptable voltage drop.

41

Rule Requirement 42 Design Issue DNV Lloyd’s Register ABS Germanischer Lloyd Alarms An alarm shall be given at a manned The battery charger unit or The UPS unit is to be monitored. An control stations if the charging of uninterruptible power system (UPS) audible & visual alarm is to be given on battery fails or if the battery is being unit is to be monitored and audible and the ship’s alarm system when the Charging discharged. visual alarm is to be given in a normally battery is being discharged. attended location for when the battery is being discharged. Input failure An alarm shall be given when the input The battery charger unit or The UPS unit is to be monitored. An power fails to a UPS uninterruptible power system (UPS) audible and visual alarm is to be given unit is to be monitored and audible and on the ship’s alarm system for power visual alarm is to be given in a normally supply failure (voltage and frequency) attended location for power supply to the connected load. failure (voltage and frequency) to the connected load. Earth fault An alarm shall be given when there is The battery charger unit or The UPS unit is to be monitored. An an earth fault uninterruptible power system (UPS) audible and visual alarm is to be given unit is to be monitored and audible and on the ship’s alarm system for earth visual alarm is to be given in a normally fault.

attended location for earth fault.

Bypass An alarm shall be given when the UPS The battery charger unit or The UPS unit is to be monitored. An bypass is in operation uninterruptible power system (UPS) audible and visual alarm is to be given unit is to be monitored and audible and on the ship’s alarm system when the visual alarm is to be given in a normally UPS is not operating under normal attended location when the bypass is in conditions. operation for on-line UPS units. Battery MCB An alarm shall be given when the The battery charger unit or The UPS unit is to be monitored. An battery protection has operated uninterruptible power system (UPS) audible and visual alarm is to be given unit is to be monitored and audible and on the ship’s alarm system for visual alarm is to be given in a normally operation of battery protective device. attended location for operation of battery protective device

IMCA MIMCA 196

Rule Requirement IMCA MIMCA 196 Design Issue DNV Lloyd’s Register ABS Germanischer Lloyd Testing

Testing of battery supplies UPS systems and DC battery backup Appropriate testing is to be carried out power systems shall be function tested to demonstrate that the battery for dip free voltage when feeding charger units and uninterruptible power is turned off power system (UPS) units are suitable for the intended environment. This is expected to include as a minimum - functionality, including operation of alarms; temperature rise; ventilation rate and battery capacity. Capacity Battery systems shall be tested in battery supply mode for a period determined by the requirements of the system and the relevant rules. Independence When proving the independency for the main and emergency power systems the emergency system will be disconnected including batteries and

UPSs. The following shall be tested

black start and normal operation.

43

9 Switching Arrangements

9.1 General

The UPS or DC power unit is often just one part of a wider power distribution scheme for battery backup power which may include:  automatic or manual changeovers for dual supplies to the input of the UPS;  changeovers at consumers;  external manual bypasses direct to the UPS distribution.

Although the examples which follow discuss UPSs, many of the same principles apply to DC battery systems.

9.2 Main and Backup Supplies to UPSs

Some classification society rules require that UPSs are supplied from the main power distribution in a manner that supports the split in the overall redundancy concept. In the past, before this rule was implemented, it was quite common to find that all UPS were supplied from the emergency switchboard as shown in Figure 25. This arrangement can still be found on recent new-build vessels and, although there are advantages to this arrangement, it actually creates an opportunity for a fault in one part of the vessel’s main power distribution system to affect what should be a completely independent section if one of the UPSs has a faulty battery.

EG

Port 440V Emergency 440V Starboard 440V

NC NC

Emergency 230V Port Thruster Auxiliaries Starboard Thruster Auxiliaries

UPS UPS A B

Hidden Failure of Battery

Port Starboard Thruster Control Thruster Control

Failure of the emergency 230V transformer or Figureswitchboard 25 – UPS A will and limitB create time a common on DP point to battery endurance. A hidden failure of the battery in Figure 25 shows a typical powerUPS B system will cause arrangement all thrusters for toa dieselbe lost electric if the port vessel in which the UPSs for the port thruster control systemspower systemand the blacksstarboard out thruster or 440V control transformer systems are supplied from the emergency switchboard. fails Both ( as UPSs the areemergency of the double230V will conversion also drop out (online)). type. In this failure scenario, which has happenedThrusters several may times be in recovered real life, ,UPS but B valuable has a hidden time failure in the form of a faulty battery which goes openwill be circuit lost and several the vesselseconds will after lose transfer position .to battery supply. The initiating

44 IMCA M 196

fault leading to loss of position is a spurious trip of the circuit breaker on the secondary side of the port 440V service transformer such that the port thruster auxiliaries lose power leading to loss of 50% of the thrusters. Unfortunately, the port LV switchboard also supplies the emergency switchboard which blacks out until the emergency generator connects. Because the batteries in UPS B are faulty, control power is lost to all the other thrusters which are then rejected from DP control and position is lost.

In modern vessels, it is far more common to provide important UPSs with two supplies, one from an appropriate part of the main power system commensurate with the equipment that the UPS supplies. For example, in Figure 25, UPS A would have a normal supply from the port 440V switchboard and UPS B would have a normal supply from the starboard 440V switchboard. In this way, a faulty battery cannot compound a simple UPS failure leading to loss of position. Figure 26 shows the type of arrangement used to provide a backup supply to each UPS from the emergency switchboard. An auto changeover provides some protection against premature battery failure. A similar effect can be obtained by supplying the UPSs’ auto-bypass from the emergency switchboard rather than from the same switchboard as the rectifier input of the UPS. In all cases where redundant elements are linked by auto-changeovers, the effect of hidden failures and transfer of fault must be considered in the design. If it is decided that an auto-changeover is not required then it can still be useful to have a manual changeover to allow UPS batteries to be charged during drydock and at other times when main power is not available, for example, if blackout recovery takes longer that 30 minutes.

MAIN EMERGENCY POWER POWER SUPPLY SUPPLY

) )

NORMAL BACK UP POWER POWER SUPPLY SUPPLY

MANUAL OR AUTO CHANGEOVER

UPS OR DC POWER SUPPLY

Figure 26 – Auto-changeover for UPS or DC power supply input

9.3 Static Switches

Static (semiconductor) switches are used in standby and online UPSs to switch the load power between the inverter output and the main supply. Static switches are generally constructed from back-to-back SCRs (thyristors). Transfer times are quoted as being of the order of 4ms which is quarter of a cycle at 60Hz power frequency. The power interruption experienced with load transfer in a line interactive UPS is also of this order. Provided that detection of loss of power does not extend the transfer time to significantly more than 4ms, most IT loads using switched mode power supplies will not malfunction during the transfer. In fact, any unsatisfactory performance is not likely to be associated with the transfer time but rather the detection time, or lack of sophistication in detecting unacceptable changes in the input waveform. Therefore, it would be prudent to determine the overall transfer time for a range of conditions and confirm the effect. For a standby or line interactive UPS, poor switching performance causing malfunction in the load could significantly reduce the reliability of the vessel as these types of UPS are expected to switch as power quality deteriorates and improves (this switching may occur frequently in a marine application). Transfer time is less of an issue for an online UPS as transfer to bypass should only occur on an inverter or distribution fault. In the case of a distribution fault there will be a significant power system disturbance anyway. The redundancy concepts of DP vessels should accept that a UPS can fail and transfer to bypass is only an

IMCA M 196 45 enhancement. However, frequent malfunctions associated with poor switching would be unacceptable even if they did not lead to a loss of position, bent pipe or broken drill string.

In UPSs which transfer from inverter mode to bypass mode to clear faults in the UPS distribution, the bypass needs to be rated to supply the fault current. Information available from the public domain suggests that some manufacturers undersize the bypass for continuous operation but provide a mechanical bypass across the SCRs in the form of a contactor. It is understood that this may contribute to unreliability in this type of UPS.

Most online UPSs will keep their inverter output in synchronism with the raw main supply so long as it stays within acceptable limits. If the raw power quality deteriorates, however, the two supplies will be allowed to diverge and transfer to bypass will be inhibited.

9.4 Changeovers at UPS Output or in the Distribution Scheme

Dual AC supplies are often provided to DP essential consumers such as VMS field stations operator stations, thruster control systems and the like. Typically, dry contact relays or contactors are often used for this purpose. The intention of such schemes is often to improve the worst case failure by providing a second supply to an important consumer such as a thruster or generator control unit. Figure 27 shows how this changeover arrangement can compromise the redundancy concept. In the arrangement shown, there are two main UPSs supplying power to three bow thrusters. The centre bow thruster has a dual supply from both UPSs. These UPSs also supply the DP control systems. There are two concerns with this arrangement related to a fault on the supply to the centre bow thruster:  The selectivity of the over current protection in the distribution board might not be good enough to ensure that the fuse in the feeder blows and not the incomer. In this case the auto-changeover will operate and blow the incomer fuse at both UPS distribution boards failing the power to both DP control systems.  The correct fuse may blow but the auto-changeover operates and blows the fuses on both UPSs distributions. The voltage dip causes both DP control systems to re-boot.

This type of arrangement should be avoided but if it already exists, or there is no other solution, then the effect of a voltage dip should be proven. The changeover should be designed in such a way that it will not change over if the fault is in the changeover itself or the equipment it supplies.

UPS UPS A B

UPS DISTRIBUTION BOARD

AUTOCHANGEOVER

DP CONTROL DP CONTROL THRUSTER THRUSTER THRUSTER SYSTEM SYSTEM ECU ECU ECU A B

FAULT

T1 T3 T2

Figure 27 – Dual UPS arrangement with auto-changeover

46 IMCA M 196

10 Operational Issues

10.1 Safety Considerations

Personnel considerations: UPSs and DC battery systems present some additional hazards compared to other types of electronic equipment but these can be adequately controlled by normal workplace management. Due to the presence of batteries and capacitors, lethal voltages may exist within enclosure even after the unit has been isolated. Battery banks contain large amounts of stored energy which can be released very rapidly in the event of a short circuit fault leading to explosion/fire.

Manufacturers’ guidelines for maintenance should be followed by competent and approved personnel working within a permit-to-work system.

Explosive effects: All lead acid batteries can release hydrogen if abused, incorrect charging voltage being the most likely cause of out-gassing. Hydrogen forms an explosive mixture with the oxygen in air at the right concentrations and UPS rooms should have adequate ventilation. Class rules provide guidelines on the type of compartment in which various sizes of wet cell battery banks and VRLA battery banks may be located.

Corrosive effects: Lead acid wet cells contain sulphuric acid in liquid form. This may leak out if the battery casing breaks or bursts due to swelling of the plates and can attack metal enclosures and injure personnel. The usual precautions and personal protective equipment for handling corrosive substances should be available. Statutory and company regulations may apply for the handling of such materials.

Area/location considerations: Class rules contain requirements for the location of battery banks in relation to hazardous area classification and these should be followed. Typically, rules for mobile offshore drilling units may specify that compartments containing batteries should be considered as Zone 2 hazardous areas and the equipment within them suitable for operation in Zone 1. However, this is a specialised subject and the reader is directed to the rules of the appropriate classification society.

Ventilation requirements: These are also set out in class rules but, typically, requirements apply to all types of rechargeable batteries with some distinctions made between those batteries having a liquid or dry electrolyte. The ventilation inlet should be in the lower part of the compartment and the outlet in the upper part so that pockets of gas cannot form. Ventilators should be so designed that they cannot be closed and the outlets should be located above the main deck. Some classification societies will permit variation of forced ventilation rates if multi stage charges are used so that a reduced ventilation rate is applied when the batteries are on float charge switching automatically to a higher ventilation rate when the charging current exceeds a defined level.

10.2 Environmental Considerations

Transport and disposal considerations: All types of batteries commonly used aboard vessels are potentially toxic and should be disposed of responsibly. The transportation and disposal requirements of the country in which the vessel requires to transport or dispose of batteries should be followed. Vessel operators should be aware that batteries may be treated as hazardous or toxic waste and there may be restrictions on disposal and transportation. Battery testing companies may be able to provide a transport and disposal service as might some recycling companies.

Nickel-cadmium batteries used in DC power supplies for switchboards may attract particular attention from regulatory bodies due to the toxicity of cadmium.

IMCA M 196 47 11 Suitability for Marine Applications

11.1 General

The marine environment presents significant challenges for electronic equipment designers including:  heat;  vibration;  humidity;  saliferous atmospheres.

As previously discussed, most UPS units installed on vessels are designed and built originally for commercial or factory use. However, all electronic equipment installed on vessels which forms part of the propulsion system must be approved by the relevant classification society who may well attend the FAT for the equipment to make sure it meets their requirements.

Many DP vessels have unmanned machinery space notation in addition to their DP notation. Some classification societies link the requirements of their DP notation to the construction requirements of their unmanned machinery notation which set out construction requirements in more detail, for example:  DNV – E0;  ABS – ACCU;  LRS – UMS.

11.2 Construction for Marine Environment

The survey of vessel DC supplies and UPSs suggests that very few UPSs are purpose built for marine applications. Some manufacturers do have a marine range but survey results suggest that the majority of UPS installations on vessels are either standard commercial units or ruggedised version of commercial units built into larger steel enclosures. These ruggedised versions may include an external battery bank and distribution.

As battery life is severely affected by operation at elevated temperatures, a location should be chosen where the temperature and humidity is controlled. By locating UPSs in air conditioned spaces, such as electrical equipment rooms or switchboard rooms, much of the problems regarding corrosion of mild steel components or the galvanic action associated with connections between dissimilar metals are avoided but it is still relatively common to find battery chargers located in alleyways and other spaces without proper climate control.

Vibration may be more difficult to deal with as vibration levels can still be relatively high even in air conditioned spaces such as switchboard rooms. This is due to their close proximity to the main generators. Anti-vibration mounting may help as will securely mounting commercial components with a ruggedised case.

11.3 Design for Marine Applications – UPS

From the information and issues discussed above, it is possible to put together a specification for a UPS for a marine application. Suggested arrangements for UPS and DC systems are shown in Figure 28 and Figure 29.

48 IMCA M 196

UPS UNIT AND BATTERY BOX

BREAKER OPEN INDICATION UPS AC SUPPLY BATTERY TEST FUNCTION (SEE VARIOUS TYPES)

GENERAL FAULT SHUT DOWN EXTERNAL SYSTEM MAINS FAILURE EARTH FAULT LOCAL CONTROL CHARGER FAULT CONDITION AND INDICATION UPS INTERNAL BYPASS ON UPS FAULT CONDITION BATTERY IN DISCHARGE BATTERY VOLTAGE LOW METAL SEPARATION ESD INTERFACE BREAKER OPEN IF REQUIRED INDICATION

BATTERY BOX WITH CORRECT CELLS CB OPEN SPILL TRAY FOR CELL TYPE INDICATION SUITABLE FOR EASY INSPECTION

SEE NOTE 1

BATTERY BANK TEMPERATURE ALARM

AC BYPASS SUPPLY

DISTRIBUTION PANEL

A V

MANUAL BYPASS AND A FILTER IF NOTE 1: REQUIRED BREAKER OPEN IF BATTERY BANK CELLS ARE WET TYPE, INDICATION BATTERY BOX TO BE SEPARATE NOTE 2: IF DUAL SUPPLY BOTH SUPPIES TO BE ALARMED MULTI OUTPUTS Figure 28 – Design of UPS arrangement suitable for marine applications

Typical marine UPS: A typical marine UPS should of course meet all the requirements for electrical compatibility discussed in Section 6. In addition, the UPS needs to comply with classification society rules as discussed in Section 8. Figure 28 shows a typical layout in which the UPS and its distribution are located in separate enclosures so that, in the event of a severe fault within the UPS, the distribution will not be affected and the manual bypass can still be used to supply the load. Although the battery compartment is shown within the same enclosure as the UPS itself, this is only possible if the batteries are not of the wet cell type. Although it is very common and convenient to include the battery bank within the UPS enclosure, consideration could be given to having a separate battery bank to improve access for routine inspection of the batteries. Many UPSs provide information by way of a single line LCD display on the UPS itself. This may be difficult to view when a commercial UPS is relocated within a ruggedised enclosure and it may be useful to add additional instruments to the UPS distribution.

Interfaces should include:  Mains failure alarm;  Battery in discharge;  In bypass mode;  Inverter fault;  Charger fault;  General fault;  Shutdown external systems (if required);

IMCA M 196 49  Circuit breaker indication;  Remote battery isolation for ESD;  Battery disconnected (cell and/or bank);  Battery voltage low;  UPS on alternative AC supply (if dual supply);  Earth fault.

11.4 Design for Marine Applications – DC Supply

Typical marine DC power supply: A typical marine DC power supply should meet all the requirements for electrical compatibility discussed in Section 6. In addition to this, the DC power supply needs to comply with classification society rules as discussed in Section 8. Figure 29 shows a typical layout in which the rectifier control unit, the distribution and the battery bank are located in separate enclosures.

Interfaces Include:  Mains failure;  Battery in discharge;  Charger fault;  Boost charger on /trickle off – (may be required for ventilation control);  ESD interface;  Output voltage too high;  Charge indication;  Earth fault.

50 IMCA M 196

BATTERY CHARGER PANEL

AC INPUT

CHARGER FAULT CONDITION

BREAKER OPEN LOCAL DC OUTPUT VOLTAGE HIGH INDICATION CONTROL MAINS FAILURE AND BATTERY IN DISCHARGE INDICATION

BOOST CHARGE ON

DUAL FLOW DISTRIBUTION PANEL AMMETERS

BREAKER OPEN A A V INDICATION

MULTI OUTPUTS

DC SUPPLY

BREAKER OPEN INDICATION

CELLS BATTERY BOX WITH CORRECT SPILL TRAY FOR CELL TYPE SHUNT TRIP

ESD BATTERY BANK INTERFACE TEMPERATURE ALARM IF REQUIRED

Figure 29 – Design of DC power supply arrangement suitable for marine applications

IMCA M 196 51 12 References

The following sources of information were used in the preparation of this guidance document: 1 Samstad J, Hoff M – Technical Comparison Online Vs Line-Interactive UPS designs – SPC White Paper #79 2 Anon – Understanding Power Factor, Crest Factor an Surge Factor – APC White Paper #17 3 IEC 62040 from which is derived BS EN 62040-3:2001 – Uninterruptible Power Systems (UPS) 4 NEMA Standards Publication PE 1-2003 – Uninterruptible Power Systems (UPS) – Specification and Performance Verification 5 IEEE Std 450-2002 IEEE – Recommended Practice for Maintenance, Testing and Replacement of Vented Lead-Acid Batteries for Stationary Applications 6 IEEE Std 1188-2005, IEEE – Recommended Practice for Maintenance Testing and Replacement of Valve-Regulated Lead Acid (VRA) Batteries for Stationary Applications 7 IEEE Std 1184-2006 – IEEE Guide for Batteries for Uninterruptible Power Supply Systems 8 DNV Rules for Ships – Part 4 Chapter 8 January 2008 – Electrical Installations 9 DNV Offshore Standard DNV-OS-D201, January 2008 – Electrical Installations 10 DNV Offshore Standard DNV-OS-A101, October 2005 – Safety Principles and Arrangements (latest at time of writing) 11 ABS Rules for Building and Classing Steel Vessels 2008 12 ABS Rules Effects of Harmonics 2006 13 Lloyd’s Register of Shipping – Rules and Regulations for the Classification of Ships – 2006 14 Germanischer Lloyd – Rules & Guidelines 2008, Rules for Classification and Construction’, I – Ship Technology, Part 1 – Seagoing Ships, Chapter 3 – Electrical Installations 15 Public domain (Internet)

52 IMCA M 196

Appendix 1

UPS Qualification Checklist

The following list can be used as an aid to the preparation of a specification for a UPS. Most manufacturers will provide a detailed specification for comparison with specific requirements. It is inevitable that some aspects of a specification will have to be negotiated with potential vendors as it is unlikely that manufacturers will have an off-the-shelf product to fulfil every requirement.

Attention is drawn to Annex D of IEC Standard 62040-3 – Purchaser Specification Guidelines. Issue Notes 1 Type approval Classification society 2 Construction 1 Standards NEMA/IEC/TUV or equivalent 2 Ingress protection 3 Hazardous zone rating 4 Anti condensation heaters 5 Surface preparation 6 Cable connections – glanding – terminations bottom/top/side entry 7 Nameplates 8 Service lighting 9 Audible noise 3 Ventilation Size of battery bank many influence location and ventilation requirements 4 Metering Voltmeters and dual direction ammeters for battery monitoring 5 Interface and alarms 1 UPS on batteries 2 UPS in bypass mode 3 Battery disconnected – (for each cell or for each bank) 4 Battery voltage low 5 Shut down external system 6 Earth fault 7 Charger fault 8 General fault 9 Battery over-temperature 10 Alarms for AC input(s) failed 11 Alarm for connection to alternative AC input (if dual supply) 12 Serial link to VMS 13 Battery test function required 14 Can interface be made application specific? 6 Type of UPS Online (double conversion) preferred for critical applications Line interactive 7 Input power 1 Input voltage specification 2 Input arrangement - number of phase/wires (3 wire, 4 wire, 5 wire) 3 Voltage variation 4 Rated frequency 5 Frequency range 6 Input power factor 7 Surge capability 8 Input current limit 9 Input current THD – (Can be 30% THD for MODU) 10 Surge withstand 11 Input phase rotation 12 Electronic noise isolation

IMCA M 196 53 Issue Notes 8 Output power 13 Rated voltage specification 14 Output arrangement - number of phase/wires (3 wire, 4 wire, 5 wire) 15 Output capacity 16 Rated load power factor 17 Voltage regulation 18 Voltage adjustment range 19 Phase displacement 20 Phase rotation 21 Rated frequency 22 Frequency regulation 23 Frequency sync range (for auto bypass, etc.) 24 Frequency slew rate 25 Voltage transient on step change 26 Transient voltage recovery 27 Overload capacity on inverter 28 Overload capacity on bypass 29 Crest factor 30 Inrush current protection 31 Output over-current 9 Grounding Protective earth arrangements Equipotential bonding Termination of steel wire armour or braid 10 Environmental Operating temperature – (Critical for batteries) conditions Storage temperature Humidity Vibration Saliferous atmospheres 11 Battery type Lead acid wet cell – VRLA – Nickel-cadmium 12 Battery endurance 30 minutes minimum for DP plus margin for load growth and aging, etc. See manufacturer’s run-time charts 13 Battery service life 3 to 5 year or 5 to 7 year typical. Operating temperature – Note manufacturers do not always refer service life to the same operating temperature so it may be necessary to correct the service life figure for the actual operating temperature or for comparison of batteries. 14 Battery charger Battery management features Ripple factor – effect on battery life Hot Swap facility for batteries 15 Bypass requirements 1 Manual bypass 2 Auto bypass 3 Bypass from different source to UPS input 4 Bypass from same source as UPS input 16 ESD requirements Disconnection of batteries – Ability of UPS to restart from batteries 17 Number of AC input Type of changeover supplies 18 Protection and Fuses – Semiconductor fuses for inverter protection coordination Circuit breakers – MCBs for distribution Ability to isolate faults in distribution selectively 19 FAT and CAT Programs to be agreed and submitted for review 20 Warranty & service Availability of service technicians world wide support 21 Documentation Compliance/approval certificates Service manuals Electronic and general arrangement drawings

54 IMCA M 196

Appendix 2

IMCA MIMCA 196

Data on UPS, DC Power Supplies and Batteries

Survey of Owners and Operators of UPS Equipment

UPS Manufacturer Input/Output Power/Duration Type of vessel Code Battery Type Voltage of System at Full Load System Usage Owner’s Remarks K VRLA 176-276V/208- UPS for Pros: (5 Year) 240V integrated Relatively short and to the point manual automation Battery may be replaced without shutting down a system (feature system called ‘hot swap’) Easily configurable for various demands Battery test feature. Thanks to this the battery can be proven operative without shutting down the system. It is very useful Ready to use dual mains input for getting connected to separate power supplies which is a step forward in terms of the overall system reliability

Cons: Lack of NC/NO alarm output instead of existing RS232. In case of remote location easier solution would be to hook it up to the monitoring system DI instead of setting up a network so as such Pipelayer option would be appreciated Reliable, maintenance free, no problems experienced so far C Maintenance-free sealed 220V/220V 400W/650VA Thruster VFD Pros: lead-acid battery with 5 mins controls All details necessary for getting them installed available as printed suspended electrolyte: leak on the rear of the body proof Standard connections Cons: Self-contained with battery which broke in one of them within less than two years’ time Plastic enclosure might be not robust enough for marine environment No experience of any spectacular breakdowns to batteries nor to UPSs other than caused by lack of maintenance resulting in rotten poles, dry cells or incorrect application

55

UPS

56

Manufacturer Input/Output Power/Duration Type of vessel Code Battery Type Voltage of System at Full Load System Usage Owner’s Remarks

Above-mentioned UPS units perform as expected giving no troubles at all A 8pcs 12V DC, 7Ah Input/output 3kVA 115V UPS for drives Pipelayer (internal batteries) voltage 115-120V 2 units A Batteries 10pcs 12V DC Voltage in/out 3000VA, 120V None 28AH Panasonic (external 120V Watts 2100

in cabinet) Output current 25A A 8pcs 12V DC, 7Ah Input/output 3kVA 115V Integrated Six units of this type in service for seven years with only one failure (internal batteries) voltage 115-120V automation system Construction vessel A 8pcs 12V DC, 7Ah Input/output 3kVA 115V Integrated (internal batteries) voltage 115-120V automation system A N/A N/A N/A N/Av No failures since installed

A 120V/230 input N/A Pipelayer 120V/230V output C N/A N/A 120V/1750W N/A A 8pcs 12V DC, 7Ah Input/output 3kVA 115V N/A UPS failures primarily attributed to battery bank failure due to age. (internal batteries) voltage 115-120V One unit failed in such a way trip off-line when a UHF portable handheld radio was keyed immediately adjacent to it D 220V DP None Shuttle Tanker L 3 7Ah sealed lead acid 220V/230V 1000VA Cargo system None batteries 36V DC L 6 7Ah sealed lead acid 220V/230V 2000VA Cargo system None batteries 72V DC M N/A N/A N/A Thruster VSD These are not a marine product but even so they have been very control and reliable. They advertise the design as having been specifically other made to work with stand alone generators and they do deal with DP Drilling vessel

IMCA MIMCA 196 applications frequency variation more gracefully than many UPS products from others. These are all on line designs N N/A N/A N/A N/A These contain a ferro-resonant transformer and tend to be pretty

UPS

IMCA MIMCA 196 Manufacturer Input/Output Power/Duration Type of vessel Code Battery Type Voltage of System at Full Load System Usage Owner’s Remarks reliable.

General comments N/A N/A N/A N/A N/A We have had problems with ferro-resonant type UPS units where drilling contractor there were loads that had inrush, the ferro is self-protecting for over-current at its output so if load inrush applies a current demand over the rating the output voltage collapses Many UPS units do not work well with harmonics on incoming or with power line frequency that varies. Most UPS units are used on land with utility power that never varies in frequency so their basic design often does not account for frequency deviations with sufficient sophistication Most of our UPS units are the on line type, where the output inverter is providing power continuously from the DC link. We have not had very good results with the line interactive type where the inverter only switches on and provides power in certain defined conditions and the rest of the time the power is directly from the line We have had problems with reluctance of UPS manufacturers to configure alarms to our requirements. This has been ridiculous in

some cases, for example alarms on line frequency. Once we even replaced a German UPS because of this Most technical problems we have had with UPS units have been with the batteries. We use UPS units with critical loads; the only way to be sure the UPS batteries will support the UPS is a load test but that generally means if the batteries do not perform we would be at risk of dropping the load. So the maintenance guys are reluctant to load test the UPS batteries using the actual load on the UPS. So I think the guide should address maintenance strategy for UPS units We do have a concern with powering many loads from one UPS and whether a short circuit fault at one of the loads will be cleared without disturbance of the other loads

57

58

Survey of Owners and Operators of DC Equipment

DC System Input/Output Manufacturer Voltage of Current/Duration System Type of vessel Code Battery Type System at Full Load Usage Owner’s Remarks O Separate, 9 x 230V AC/108 22.2A/N/A Switchboard Few if any problems with these units. However in one unit the control PCB failed in sealed, controls the past but no further details available maintenance free, lead acid automotive-like Pipelayer batteries 12V P 3pcs, 24V banks 230V AC/24V 100A Thrusters No problems so far neither with these units nor with batteries managed by them. of 4 x DC controls and Robust stand alone construction and reliable performance nonspillable 6V other uses 190Ah J N/A 230V/110V DC N/A Not specified This is unfortunately obsolete after only one year in service with the rectifying modules irreplaceable. This system comprises several rectifying modules thus Shuttle tanker allowing the loss of one and the system still functions. Note to date we have lost three modules after three years of service G NiCAD 220V AC/110V 15A SWBD None Pipelayer

DC controls J N/A 24V DC Thruster None controls and automation system J N/A 24V DC Bow loading system Shuttle tanker J N/A 24V DC Bow loading system

J N/A 24V DC 30A Bridge J N/A 110V DC HV Switchboard controls

IMCA MIMCA 196

IMCA MIMCA 196 NDC Desktop Survey of UPS Types

Number of Type of ESD Vessel Type Systems System Usage Manufacture System Battery Type Power/voltage Bypass facility Facility Remarks

5 AC UPS DP and IAS A Online/double 32X 7Ah VRLA 210kVA/9kW/230V Manual bypass N/A Manufacturers’ original conversion 455V and auto enclosure mounted on frame transfer to with vibration mounts bypass on Pipe layer overload DP3 7 DC PS IAS and SWBD G N/A N/A 24V DC N/A N/A Manufacturer’s original control enclosure 2 DC PS HV SWBD G N/A N/A 110V DC N/A N/A Manufacturer’s original enclosure Diving N/A N/A N/A N/A N/A N/A N/A N/A No information available or Vessel provided 4 AC UPS DP and IAS F Online & Line N/A 5-6kVA 230V Manual bypass No Mounted in ruggedised interactive and auto enclosure provided by the transfer to DP Control system bypass on manufacturer overload

DP3 Drilling 2 DC PS HV SWBD G N/A NiCAD SBL 30 110V DC N/A No Manufacturer’s original semi-sub enclosure 2 DC PS Engine control G N/A NiCAD SBL 30 24V DC N/A No Manufacturer’s original enclosure 2 AC UPS Fire and gas D Online VRLA 5 kVA N/A No Manufacturer’s original enclosure 3 AC UPS DP and IAS B Online 29 by 26Ah/12V 15 kVA/208V Manual bypass No Manufacturer’s original input/120V/240V and auto enclosure with addition of output transfer to auto-changeover for dual DP2 Drilling bypass (static input supply – status LEDs semi-sub switch) in provided detection of inverter fault or overload

59

Number of Type of ESD

60

Vessel Type Systems System Usage Manufacture System Battery Type Power/voltage Bypass facility Facility Remarks 2 AC UPS IAS and thruster B Online N/A 5 kVA/208V Manual bypass No Manufacturer’s original control input/120V/240V and auto enclosure with addition of output transfer to auto-changeover for dual bypass (static input supply – status LEDs switch) in provided detection of inverter fault or overload 2 AC UPS IAS and thruster B Online N/A 8 kVA/208V Manual bypass No Manufacturer’s original control input/120V/240V and auto enclosure with addition of output transfer to auto-changeover for dual bypass (static input supply – status LEDs switch) in provided detection of inverter fault or overload 4 AC UPS IAS and thruster B Online N/A 2 kVA/208V Manual bypass No Mounted in Rittal cabinet control input/120V/240V and auto with glass front – modular output transfer to withdrawable battery banks

bypass (static switch) in DP2 Drilling detection of semi-sub inverter fault or overload 2 DC PS SWBD control H N/A N/A 110V DC Manual bypass No Purpose built cabinets – with and auto remote battery bank transfer to bypass (static switch) in detection of inverter fault or overload 8 AC UPS VSD control C Line Maintenance free 1500VA/120V No Commercial UPS in rack interactive lead acid with input, 120V output mount form suspended electrolyte

IMCA MIMCA 196

Number of Type of ESD IMCA MIMCA 196 Vessel Type Systems System Usage Manufacture System Battery Type Power/voltage Bypass facility Facility Remarks 3 DC PS SWBD control G N/A SBL30 nickel- N/A Yes – The battery charger feeds cadmium wet cell MCB the battery bank and then supply – 84 cells Tripped one supply to the at 9amp 20 years by a 24V distribution board. The DC shunt system consists of three DP3 trip units, battery charger, Drillship external battery bank and distribution supplied system separately mounted. The switchroom 110V DC supply systems are interlinked but operate independently 11 AC UPS DP and IAS E Online 2 x 12V x 4 Input 110V AC None Yes – The system consists of one output dual voltage MCB panel. The system is a 115V AC and 24V tripped by modular design which has DC a 24V DC AC and DC distribution shunt trip boards at the top, below is DP3 external rack mounted inverter Drillship supplied modules the below that rack mounted rectifier modules

the two battery shelves are at the bottom 1 DC UPS Marine and I N/A N/A 460V input/24V N/A N/A Purpose built enclosure emergency DC output, 60A

61

Number of Type of ESD

62

Vessel Type Systems System Usage Manufacture System Battery Type Power/voltage Bypass facility Facility Remarks 3 AC UPS Nav, comms and D Online Sealed lead acid 8 120V Yes Yes – UPS panel with a distribution backup DP x 12V 7.2Ah 4-5 Internal MCB system and bypass facilities. years automatic Tripped Input 120V AC. This type of bypassing all by a 24V panel is also supplied with UPS internals DC shunt two systems (dual) within inclusive of filter trip one panel with the two UPSs Manual system external on the top shelf and the external to UPS supplied bypass and distribution by selector systems below. The system switch within consists of one panel cubicle (batteries within UPS unit) which is a self-contained unit mounted in the top of the cabinet with the manual bypass switch and output distribution mounted below

IMCA MIMCA 196

IMCA MIMCA 196 VRLA Cells – Results of Vessel Survey, Vessel Technical Information and Desktop Investigation

Information Valve Manufacturer Information Vessel from Regulated Battery Battery Battery Life of UPS from Vessel Technical Desktop System System Manufacturer Lead Acid Type Cell Battery Expectancy System Survey Information Investigation Voltage Usage of Battery Type Number Voltage Ah (Years) Remarks J No Yes No 120V ac UPS Not known Information Not 12V 7.2Ah 4 to 5 8 cells listed as battery given as known Years bank sealed lead acid only K Yes No No 208- UPS Not known Information Not Not Not 5 years System type 240V ac given as known known known information was online VRLA only C Yes No No 220V ac UPS Not known Information Not Not Not Not known System type thruster given as known known known information was online- VFD maintenance- backup controls free sealed lead-acid battery with suspended electrolyte:

leak proof only A Yes No No !20V ac UPS for Not known Information Not 12V 7Ah Not known 8 cells listed as battery drives 2 given as known bank units sealed lead System information was acid only 9120 series 3kVA A Yes No No 120V ac UPS Panasonic Information Not 12V 28Ah Not known 10 cells listed as battery given as known bank. sealed lead System information acid only 3000VA, 120V Watts 2100 Output current 25A L Yes No No 220/230V UPS for Not known Information Not 36V 7Ah Not known 3 cells listed as battery ac cargo given as known bank. system sealed lead System information acid only 1000VA

63

Information Valve

64

Manufacturer Information Vessel from Regulated Battery Battery Battery Life of UPS from Vessel Technical Desktop System System Manufacturer Lead Acid Type Cell Battery Expectancy System Survey Information Investigation Voltage Usage of Battery Type Number Voltage Ah (Years) Remarks O Yes No No 108V dc Switchboard Not known Information Not 12V Not Not known 9 cells listed as battery controls given as known known bank. sealed, System information maintenance DCPS 108-22 at 22.2A. free, lead acid automotive- like batteries only S Yes No No 24V dc Not known Not known Information Not 6V 190Ah Not known 4 cells x 6V = 24V 3pcs given as non- known make up battery bank. spill only System information M6V 190F Q Yes No No 24V dc Ballast and SAE Information Not 12V 25Ah Not known 2 cells listed as battery bilge given as known bank. control cycle gel cell N/A No No Yes As UPS Yuasa VRLA AGM NP 12V Range 5 years Years rating at 20° C

required series of sizes N/A No No Yes As UPS Yuasa VRLA AGM NPL 12V Range 7 to 10 Years rating at 20° C required series of sizes years N/A No No Yes As UPS Panasonic VRLA AGM RW 4/6/12V Range 5 years Years rating at 20°C on required series of sizes 3 to 5 years trickle charge Years rating at 25°C on trickle charge N/A No No Yes As UPS Panasonic VRLA AGM PW 4/6/12V Range 10 years Years rating at 20°C on required series of sizes 6 years trickle charge Years rating at 25°C on trickle charge N/A No No Yes As UPS Enersys VRLA AGM Odyssey 12V Range Design life Years rating at 20°C required series of sizes = 12 years Service life = 6 to 8 years

IMCA MIMCA 196

Information Valve IMCA MIMCA 196 Manufacturer Information Vessel from Regulated Battery Battery Battery Life of UPS from Vessel Technical Desktop System System Manufacturer Lead Acid Type Cell Battery Expectancy System Survey Information Investigation Voltage Usage of Battery Type Number Voltage Ah (Years) Remarks

N/A No No Yes As UPS Exide VRLA AGM Absolyte 4V Range 20 years Years rating at 25°C on required X L of sizes float charge. series N/A No No Yes As UPS Exide VRLA AGM Marathon 6/12V Range 12 years Years rating at 20°C required L series of sizes (80° remaining charge) N/A No No Yes As UPS Exide VRLA AGM Sprinter 6/12V Range 10 years Years rating at 20°C required series of sizes (80° remaining charge) N/A No No Yes As UPS Exide VRLA AGM Power 6/12V Range 7 years Years rating at 20°C required Fit S500 of sizes (80° remaining charge) series N/A No No Yes As UPS SBS VRLA AGM UPS 12V Range 10 years Years rating at 20°C required HR of sizes series N/A No No Yes As UPS SBS VRLA AGM UPS 6/12V Range 7 years Years rating at 20°C required S series of sizes N/A No No Yes As UPS SBS VRLA Gel G series 6/12V Range 10 years Design years rating at

required of sizes 20°C on float charge. 8 to 10 Service years rating at years 20°C on float charge.

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Wet Cells – Results of Vessel Survey, Vessel Technical Information and Desktop Investigation

Information Lead Battery Manufacturer Information Vessel from Acid or Battery Battery Life of DC from Vessel Technical Desktop System System Manufacturer Nickel Type Cell Battery Expectancy System Survey Information Investigation Voltage Usage of Battery Cadmium Number Voltage Ah (Years) Remarks G No Yes No 110V DC supply Saft Nickel SBL 30 Not Not 20 Years 84 cell battery bank. This is a DC system for cadmium known known common cell type and HV configuration found on DP Switchboard vessels metering, protection and control also AVR control E No Yes No Dual 24V DC for SBS60 Lead acid 3 banks 12V Not Not known 6 cell battery bank output engine of 2 x known Dual systems are utilised on of 115V control, 12V DP vessels but cannot be AC and governor cells regarded as common 24V DC control, DG speed

control and also process stations. 115vAC for O/S R Yes No No 24V DC 24V DC Varta Lead acid Vb12149 12V Not Not known 4 separate 24V banks of 2 x ballast and known 12V = 8 cell battery bank bilge control N/A No No Yes 24V and DC supply Saft Nickel SBL 1.2V Wide 20 years This battery type has valve 110V system cadmium range nominal range. regulated pocket plate DC – per cell technology and is listed as other low maintenance also this voltages battery is listed as usage in as UPS systems required

IMCA MIMCA 196

Information Lead Battery IMCA MIMCA 196 Manufacturer Information Vessel from Acid or Battery Battery Life of DC from Vessel Technical Desktop System System Manufacturer Nickel Type Cell Battery Expectancy System Survey Information Investigation Voltage Usage of Battery Cadmium Number Voltage Ah (Years) Remarks

N/A No No Yes 24V and DC supply Saft Nickel SML 1.2V Wide 20 Years This battery type has valve 110V system cadmium range nominal range regulated pocket plate DC – per cell technology and is listed as other low maintenance also this voltages battery is listed as usage in as UPS systems required N/A No No Yes 24V and DC supply SBS Lead acid OPS 2V per Wide 20-25 years This type of battery has been 110V system range cell range listed as DC systems as the DC – study research has highlighted other only one wet cell usage in a voltages UPS system. This was a dual as system with AC and DC required outputs N/A No No Yes 24V and DC supply SBS Lead acid STT 2V per Wide 20-25 years This type of battery has been 110V system range cell range listed as DC systems as the DC – study research has highlighted

other only one wet cell usage in a

voltages UPS system. This was a dual as system with AC and DC required outputs

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