Special Report for Session 3 CIRED 2001

C I R E D 17th International Conference on Electricity Distribution Barcelona, 12-15 May 2003

Special Report – Technical Theme 3 OPERATION, NETWORK CONTROL AND PROTECTION

Th. CONNOR Rapporteur - Federal Republic of Germany [email protected]

INTRODUCTION MORNING SESSION The session will present 27 papers on Block 1 operation. The call for papers resulted in 105 abstracts related to Out of this number there will be 9 selected papers present- the subjects of Session 3. Out of them 73 papers were ed in some detail and 18 giving an update or summary. selected based on the judgment of national committees as well as the technical committee of CIRED. The num- After the coffee break the Block 1 section will be fin- ber of papers reflects an increased interest in the subject ished. For Block 2 network control the presentation of 15 of network operation, control and protection. papers will start. Out of them 4 are selected for a more detailed presentation. The majority of papers was prepared by groups of au- thors. In some cases these groups are composed of au- Block 1 Operation thors from different countries and even continents. Neutral earthing methods The papers are reflecting: The papers 3.6-Italy, 3.7-Italy and 3.33-Italy give a very  The experience of large and small utilities, of ru- detailed survey of the actual situation in ENEL´s distribu- ral as well as urban areas tion networks. The need for change in neutral earthing scheme from isolated neutral to a special compensation  The products and strategies of manufactures with introduction of new protection and switches in order  The scientific as well as practice orientated work to obtain automated fault clearing, improved operation of universities and research institutes and satisfy customer requirements. First results show that traditional methods of customer supply restoration lasted  Interesting joint work e.g. between utilities and 50 minutes while the new approach reduced the time to 6 manufactures minutes. The subject of the session is structured in three blocks The distribution networks of Poland are presented in pa- which are subdivided by topics originated from the main per 3.20-Poland. The main distribution level of 15 kV is focus of the papers presented. operated with Petersen coils. In the past only 50 % of the Block 1 Operation earth faults could be detected. Today due to the improvement of protection the rate has increased to 95 %.  Neutral earthing methods Paper 3.24-Slovak Republic offers a special equipment to  Fault detection measure capacitive earth fault current contribution during an artificial earth fault.  Network automation Fault detection  Loss reduction and voltage control The experience on localization of earth faults and short  Special operational conditions circuits in a rural medium voltage network is given in pa- Block 2 Network control per 3.9-Germany. Results of 130 analyzed faults are given, indicating that 90 % of all faults could be located very Block 3 Protection quickly. Furthermore the parameters influencing the accu-  Relays and settings racy of detection are discussed.  Dedicated earth fault protection Fast fault localization resulting from a computer based support for fault clearance is given in paper 3.13-Ger-  Special protection features many. The method simulates accessing and switching and can be handled interactively.  Theoretical basis for protection development Automation in extended overhead line networks without The morning session will cover Block 1 and the first communication is a challenging task. Paper 3.22-Norway part of Block 2. In the afternoon Block 2 will be contin- gives details of fault statistics and costs of energy not de- ued and Block 3 will be dealt with. livered. Experience with a system that brings interruption time in case of permanent faults down from 90 minutes to 3 minutes are presented.

Theodor Connor Session 3 Special Report - 1 - C I R E D 17th International Conference on Electricity Distribution Barcelona, 12-15 May 2003

Another paper on fault detection and automation is options in the light of economic parameters valid in 3.42-Japan. Distribution automation systems composed Spain. of switches and fault indicating devices are used for The joint work of university and utility in paper 3.2-Libya more than 20 years. The actual stage of the system in- highlights the need for power factor improvement. It is cluding the communication channels are presented. recommended to carry out periodical power factor mea- For the CEMIG utility in Brazil which serves an area surements and check of power factor compensation equip- roughly the size of France the average number of thun- ment. derstorm days per year is 70. paper 3.3-Brazil gives de- According to paper 3.14-Iran it is possible to maintain si- tails on their detection system for atmospheric discharge multaneously the voltage of several feeders in a distribu- and the implementation into the operation. tion system. For this purpose fuzzy modeling and fuzzy Paper 3.11-China proposes a method to reduce fault optimization strategies are applied. time in compensated networks from more than 2 hours Paper 3.15-Colombia reports on a project of ENELVEN to less than 10 seconds. The necessary compensation utility in Venezuela. A real time power flow tool is imple- disturbance for fault detection is achieved by a fast elec- mented to identify losses on transformers and lines under tronic switch. special consideration of unbalanced loads and a large va- Automation riety of transformer vector groups. Power quality improvement in distribution systems by Strategies to prevent voltage collapse in transmissions means of optimization of the protection and control sys- systems are well established. Paper 3.18-Sweden proposes tem is the subject of paper 3.5-Argentina. EDEMSA a new selective control strategy which allows both switch- utility studied the suitable locations to install teleoperat- ing on and off of loads in distribution systems. Details of ed reclosures to improve quality factors such as frequen- the indicators for voltage instability and simulation results cy of power outage and average outage time. The statis- are given. tics after more than two years clearly show the improve- Paper 3.23-China has interesting details of the China ment. power grid development. The focus is on line loss control. Paper 3.4-Belgium illustrate the all in one software Adequate measures especially in distribution networks package managing the whole data processing from cus- will bring loss rate below 7 %. It is pointed out that it is a tomer call to breakdown origin. Electrabel Netmanage- large challenge to decrease line losses during a period of ment Wallonia is giving details of the software tools in- overall load increase. volved and operational sequences to handle break- Another approach to reduce power losses emerge from downs. paper 3.25-Finland. To improve supply reliability and The network automation project for Zagreb is described fault detection and to cope with increasing distributed in paper 3.16-Croatia. Details of the network and auto- generation the closed ring operation is studied and offers mation components including remote control elements, benefits for overhead line systems. fault indicator and communication system are given. Special operational conditions AES Eletropaulo is the distribution utility operating city In some extended territories overhead lines are put into of Sao Paulo. Paper 3.28-Brazil presents methodology danger by icing. Paper 3.8-Russia identifies the critical and software tool to monitor events and identify the weather conditions in which preventive warm up of phase most probable causes. conductors and ground wires can be very useful. Paper 3.34-Romania proposes a tool to improve quality For the operation knowledge of the impact of different of supply indices. The tool is based on wireless commu- technologies in a restoration process is evident. Paper nication technology options using short range radio 3.12-Canada describes the Fjord project which allows de- links and the use of scatternets. scription and simulation of system operation according to Loss reduction and voltage control different scenarios. Paper 3.21-China presents a real time monitoring sys- Some open questions for the free discussion of network tem for reactive power and voltage. The system with 8 operation are: sub-functions is embedded in the existing automation surrounding. The system guides operating personnel to  Each of the different neutral earthing methods of- timely adjust voltages. As a benefit it is shown that for fer benefits for the operation. Which method is the 35 kV to 110 kV the line losses were reduced by 0.5 % most suitable for mixed overhead line and cable resulting in 15 million kWh saved. networks? The possibility to introduce trade of reactive power are  Which are the strategies to disconnect faulted sec- analysed in paper 3.1-UK. This paper is based on an ex- tions in compensated networks in case of operation ample for a typical Spanish network and gives technical with permanent earth fault?

 Are there experiences with cross country faults AFTERNOON SESSION and evolving faults in compensated networks? Block2 Network control  Which are the limits for the size of compensated Paper 3.10-Belgium gives a summary on a practical IT networks? based tool to improve distributor’s quality of supply. The  What is the cost-benefit relation of fast fault de- linked SCADA and distribution management tool offers tection and clearing? the network operator power outage forecast, incident management and quality criteria management. Therefore  Where to put the priority? Supply continuation or operation strategies can be chosen to limit penalties. fast and reliable fault detection. The provincial electricity authority of Thailand operates  Which are the experiences with automated fault 150 000 distribution transformers. Paper 3.19-Thailand detection in case of evolving faults? gives details of a project to calculate transformer load  Is there a relation between network automation based on energy consumption data for customer billing. and maintenance efforts? In a retrofit program of Southern California Edison Com- pany 50 substation automation systems were installed per  Which level of network automation is required year. Paper 3.29_USA gives details on the project targets for developing countries? and the joint work with manufactures to develop a substa-  How many training is necessary to keep operation modeling tool. tors in highly automated networks fit? A vendor independent distribution management platform  How will operators handle voltage control in the towards an integrated GIS/SCADA/DMS solution is the future with increased dispersed generation? title of paper 3.31-China. The paper suggests an integrated approach and gives way for web deployment of opera-  Is loss reduction and increased utilization of net- tional functions. work elements a contradiction? Paper 3.37-France proposes a web based substation re- Block 2 Network control mote monitoring and maintenance tool. The technical Network control evolution makes it feasible with sensible costs. The necessary hardware architecture and software tools are de- Paper 3.32-France gives a survey of the introduction of scribed to obtain improved customer service or equipment a remote control system for distribution networks called monitoring to increase lifetime. SINTR/INPACT. The goal of the project was to install state of the art and to reduce the number of control cen- The key features which are requested from modern distri- ters from 100 to 35. The new system was developed and bution management systems especially in the competitive validated at the control center in Nîmes. Afterwards 6 energy market environment are the subject of paper 3.38- centres per year were converted. Details on the software Germany. The role of communication between distribu- structure and the implementation procedure are given. tion management system and other IT systems is highlighted as well as the easy migration from existing sys- The integration of control center and power quality in- tems and the incremental upgrading for future needs. formation at IBERDROLA utility is given in paper 3.35-Spain. Distribution management systems in 9 con- The specific topic of on-line estimation of non-technical trol centers surveying 9 million customers were linked losses in a distribution system is dealt with in paper 3.39- with a central database by real time communication and Austria. In some countries the economical success of a integration with facility management, maintenance sys- utility depends on the management of non-technical loss- tem and customer information system. By this means it es which are mainly theft. A distribution management is possible to provide quality of service data to all cus- system in conjunction with meter reading offers the tomer bills. chance to track down weak points. Starting from pre-automation network performance pa- The European Community funded project ScadaOn Web per 3.36-UK reveals that medium voltage automation is presented in paper 3.41-Switzerland. The task is to cre- offers major benefits. A standard procedure was devel- ate a new web data type that can be displayed in any oped to enable a rapid implementation. The cost as well browser to handle scada data in a similar way like well as the tendency of customer interruptions and customer known gif or jepec pictures. minutes lost figures indicate that the project was suc- A new model for real time state estimation in distribution cessful. systems is the topic of paper 3.43-Finland. The novelty is On the border of operational and commercial business the fact that in addition to standard systems also compo- process of the utility the grid meter plays an important nent temperatures or customer voltages are estimated. role. Paper 3.40-Switzerland highlights that actual grid Thus network capacity can be used to full extend without meters are used for network operation and substation violating power quality standards. control as well as for commercial processes where especially secure data exchange is required.

Paper 3.44-Finland shows the importance of communi- Power quality targets are given in paper 3.51-USA. It is cation protocols. A TCP/IP based communication archi- shown that feeder protection optimization contributes to tecture for distribution network operation and control is meet targets. The role of selective protection grading and presented with special consideration of data security as- the choice between definite time and inverse time over- pects. current relays is highlighted. A new generation of distributed architecture protection A proposal for a directional relay without voltage sensor and control terminal is the subject of paper 3.45-Spain. is subject of paper 3.56-France. The aim of the paper is to show how symmetrical components can be used to in- Some open questions for the free discussion of network crease efficiency of algorithms and avoid voltage sensors. control are: Paper 3.59-Sweden analyses fast fault detection for peak  How is the optimal number and size of network current limitation. It is demonstrated that 3 phase fault de- control centers determined? tection within 1 ms after fault inception is possible. The  How is the optimal number of automated and re- method allows to distinguish between capacitor energiza- mote controlled network elements determined tion and fault inception. with respect to cost justification? A proposal for an agent based adaptive protection is pre-  Will IEC 61850 offer advantages for both user sented in paper 3.60-Korea. The relay with own intelli- and manufacturer? gence is self tuning and has a communicating ability. Changes of network topology lead to self adaptation of  Will IEC 61968 play a main role in communica- setting parameters. tion between distribution management systems and other IT systems? An important topic in network protection is the interoper- ability between new and legacy products. Paper 3.68-Ger-  Is it possible to fulfill the targets of electricity many gives details for refurbishment of relays and new trade and effective network control in parallel? beneficial features. The replacement of differential relays with new types offering several communication options is  To what degree is network control dependent on highlighted. communication security? How is communication security achieved in Web based systems? Dedicated earth fault protection  Is it possible to transfer retrofit and refurbish- The protection problems caused by intermittent earth ment programs for one project to another? faults is discussed in paper 3.48-Finland. The characteris- tics of intermittent earth faults are investigated by theory,  How can distribution management systems gen- simulations and field tests. The developed algorithms erating fault statistics distinguish between opera- show an improvement in selective detection without false tional and fault related events? starts. Block 3 Protection A new directional transient relay for high resistive earth The session will present 26 papers on Block 3 protec- faults is subject of paper 3.50-Germany. Starting from tion. Out of this number there will be 11 selected papers theory the conventional transient relays are compared to presented in some detail and 15 giving an update or the new algorithm and the advantages in case of high re- summary. sistive or re-striking earth faults are shown. In-between there will be a coffee break. Paper 3.57-China adds one more approach to new transient earth fault relays for compensated or isolated net- Relays and settings works. Results are given from two trial tests of the new Paper 3.52-Switzerland gives a practical example how relay. protection schemes are assessed in order to keep system Innovation of protection systems for indication of ground reliability on a high level. Practical studies show how faults in medium voltage networks is presented in paper simulation, calculation and site tests work together. 3.63.Czech Republic. The most effective measure for reli- A comprehensive survey of a refurbishment cycle for able indication in this case is the conductance criterion in substations is presented in paper 3.61-Netherlands. cooperation with automatic switching of an additional re- From the past, the present to the future the protection in sistor. the substation environment and the project experiences Paper 3.71-Czech Republic proposes a method for fault are reported. detection in closed loop medium voltage networks includ- Paper 3.62-Austria is focused on the upcoming commu- ing the use of remote control signals. Advantages and dis- nication standard IEC 61850. With data communication advantages are compared. networks in substations new testing tools and methods Special protection features will be required. Third generation of system protection scheme for Zeya hydro power plant is presented in paper 3.54-Russia. It re-

Theodor Connor Session 3 Special Report - 4 - C I R E D 17th International Conference on Electricity Distribution Barcelona, 12-15 May 2003 veals the need for a special protection to avoid instabili- of paper 3.72-Iran. It is concluded that for the study cases ty of power systems by the use of breaking resistors. the walsh series solution performed better. Additional measurement functions provided for a pro- Some open questions for the discussion of network protection system allows effective fault location. Paper tection: 3.64-Netherlands present experience that two and three phase fault are located within 100 m and single phase  Are there experiences about the common work of faults within 1000 m. intelligent electronic devices (IED’s) with respect to network protection, network control and meter- Fault location techniques are reviewed in conjunction ing? Is ‘one bay, one IED’ a viable concept for with different network types in paper 3.49-USA. As a protection and substation automation? result it is stated that more data and exact network model will result in more accurate fault location.  Are still new features for detection of intermittent and high resistive earth faults necessary? Is there a A new arc furnace transformer protection is presented in clear criterion, which discriminates between high paper 3.53-USA. Differential protection is not typical resistive faults and service conditions? for this kind of transformer. A key role for the given solution plays a rogowski coil as current transformer on  How can the relay engineer verify correct opera- the secondary side. tion of relays using adaptive techniques? Paper 3.55-Yugoslavia presents an analytical procedure  Will the new theoretical approaches for protection to evaluate ground fault currents in case of lines com- development reduce the number of setting parame- posed of cable and overhead line sections. ters? Are there any ‘self setting’ relays commer- cially available on the market? A toolbox for protection device coordination enhanced by embedded expert system is subject of paper 3.73-  How long will proprieratary protocols survive after Egypt. launch of the IEC 61850 standard for the informa- tive port? Theoretical basis for protection development  Are there any standardization efforts for the Paper 3.27-Iran presents a novel approach for fault loca- teleprotection port for relay-to relay communication in distribution systems using neural networks. The tion? training of the system is simple and fast. As the system is linked to a geographic information system the fault  What impact has the refurbishment of the commu- location can be displayed in a map. nication infrastructure on relay-to relay communication? Signal analysis of simulated and measured earth faults in compensated distribution networks for future devel-  When is the market ready for large scale use of opment of fault location methods is the subject of paper novel sensors? Is there a full range of relays and 3.47-Denmark. Earth faults were analyzed using wave- meters available for use with novel sensors? let transformation and Prony analysis. The tool developed appears to be a promising method for fault loca-  What is the impact of neural networks techniques tion improvement. on field testing and fault analysis? By use of time domain reflectometry it is possible to get automatic fault localization for low voltage cable systems. Paper 3.69-UK gives details how this tool can be used even with multiple tees. The detection of high impedance faults using artificial neural network is presented in paper 3.58-Saudi Arabia. Several different designs were trained and tested show- ing promising results for different types of faults. Paper 3.65-UK is focused on data compression of power system data for network operation and control using wavelet transformation. The purpose of using such methods is to reduce data communication burden. A practical example of implemented neural network technology is given in paper 3.67-France. Field experience with a transformer differential relay based on neural networks is presented. A digital differential relay for transformer protection using walsh series and least square algorithms is the topic

Theodor Connor Session 3 Special Report - 5 -