301 Madrid, SPAIN Coordination of Protection · PDF fileare related to the proper relay coordination under different fault and system conditions. ... The accuracy of the fault location

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Coordination of Protection Relays

Hideyuki Kameda (CRIPI, JP), Seung-Jae Lee (Myongji Univ., KR), Eva Werdin (Svenska Kraftnat, SE), Zainoren B. Xhukri (Tenaga, MY), Henri Grasset (Areva, FR),

Takahiro Kase (Toshiba Int., UK), Chikashi Komatsu (Hitachi, Ltd., JP)

Abstract Protection, seen as "the recovery of the power system to a stable state", depends not only on the reliability and technical excellence of its components but also on the adequacy of the functions to the application for which they were designed. Protective relaying, as many other systems, is not made by ideal entities, but by dispersed, discrete and non error-free ones. These devices, IED, or more generally functions need to be linked with each other in an organized manner in order to allow the Protection System acting as a whole and in a selective way: Coordination is the technique, art or process that makes this possible. This paper constitutes the introduction to the WG B5.19 Report which covers protection system coordination issues. The Report presents the results of a worldwide questionnaire regarding protection system functions breakdown by power system components, voltage level, Main and Backup, including Special Protection Schemes applications. Examples of required coordination studies are also pointed out in this paper, whilst the Report will deal with a more detailed sequence of the coordination between protective relaying devices and functions, illustrating with concrete situations.

Keywords Coordination, Protective Relaying, Protection Relay, Fault Clearance Relay, SPS.

Study Committee B5 Colloquium 2007 October 15-20

Madrid, SPAIN 301

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Imporving Transmission Line Protection Coordination Through Line Impedance Measurement

Ulrich Klapper (Omicron electronics, Austria), Alexander Apostolov (Omicron electronics, USA), Damien Tholomier (AREVA T&D Automation, Canada),

Simon Richards (AREVA T&D Automation, UK)

Abstract The performance of transmission line protection relays when a fault occurs in the system is important for improvements in the stability of the system and reduction of their effect on sensitive loads. Reducing the fault clearing time for more possible fault conditions is one of the main goals in the development, application and setting of such relays.

The operating time of a transmission line protection relay is a function of many different factors. Some of them are related to the operating principle and the design of the relay itself, while other are related to the proper relay coordination under different fault and system conditions. Transmission line protection coordination requires an accurate model of the electric power system in order to ensure that the calculated short circuit fault currents and voltages are as close as possible to the actual fault values. The paper specifically focuses on the requirements for coordination of non-unit protection solutions – distance and overcurrent – and analyzes the impact of errors in the line impedance parameters on the accuracy of the short circuit currents and voltages calculation, the settings of the distance and overcurrent relays and the fault clearing times for different line lengths and fault locations. The accuracy of the fault location calculation is also affected.

The inaccurate values of the mutual coupling of parallel transmission lines are another important factor that may affect the operation of the relays for faults involving ground. This is also discussed in the paper.

The transmission line impedances used for short circuit currents calculation and the setting of distance relays are normally derived from the results of a line constants program calculation or systems studies. Due to the large number of influencing factors (e.g. wire types, spiraling and average sag of the wires, shield handling on cables, specific soil resistivity) these calculations can be prone to error.

Actual measurement of the fault-loop impedance is the best way to ensure that the distance and overcurrent relay settings are correct. The paper describes an advanced method for these measurements and calculations that provide the impedance data for the different applications that use it. Comparisons of estimated and measured line impedances are presented at the end of the paper.

Measuring mutual coupling between power lines can be done using a similar method.


Madrid, SPAIN 302

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Keywords Transmission Line Protection, Protection Coordination, Impedance Measurements.

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Establishing Sufficient Redundancy: Protection & Telecommunication

Rodney Hughes (Australia)

Abstract The principles of using telecommunication links to improve the performance of protection schemes are well known and are standard practice throughout the world.

Distance protection relays often use signalling channels to speed up or control the response of relays at the remote end, current differential relays use medium speed communication links to enable comparison with currents measured at the remote end, or circuit breaker fail schemes send direct trip signals to the remote ends to ensure system stability and fault isolation. “Wide area protection” principles and generator “run back” schemes are increasingly relying on telecommunications as the enabling technology.

A key principle for ensuring power system security is using duplicated protection systems. In this respect, the basic principles of protection have not varied significantly despite the change from electromechanical to static to numeric/digital designs.

Telecommunication networks also encompass continuity of service provision as a key objective. However electric power utilities have seen a significant change in technologies and, as a result, also a dramatic change to telecommunication network designs. Copper pilots and power line carrier are now being superseded by microwave radio and optical fibre networks. These networks have been progressively established and interconnected using principles of duplication and geographic route diversity relative to the provision of individual services giving a sense of duplication as implying overall reliability of the power network.

Many countries are now introducing regulations (also known as codes or rules) as over arching standards around the design and performance of the electricity networks including the features and operation of the protection and telecommunication systems. These standards increasingly create more stringent requirements on the primary system design and the associated protection and telecommunication systems. This paper explores some of these issues in respect of mesh networks and tee- line configurations for high voltage systems. These systems typically use distance protection or current differential protection, and hence this paper considers the telecommunication network design and the associated service or channel allocation strategy.

The key conclusion is that the protection engineer cannot simply rely on the existence of two telecommunication paths at the substation as sufficient evidence of compliance to the power system performance, operation and design rules.

Keywords Protection, Telecommunication, National Electricity Rules, Duplication, Tee lines, system planning, distance protection, current differential protection.


Madrid, SPAIN 303

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Limits and Advantages of Different Protection Principales on Series Compensated Lines

G. Arruda (Chesf, Brazil), R. Dutra (Furnas, Brazil), P.C. Campos (Eletronorte, Brazil), V. Henn / R. Krebs (Siemens AG, Germany)

Summary Series compensation is widely used to improve the transmission capability of long distance overhead transmission lines and the overall network efficiency. These capacitors do not only influence the operational behavior of the power system, but also the behavior during short circuits. Effects like voltage inversion are well known and covered in distance protection relays by determining the direction of the fault with memorized voltages. Depending on the location of the capacitor, its size, the protection level of the platform protection, and the impedance of the source current inversion is also possible. If this current inversion occurs, new problems arise for the protection scheme. High resistive earth fault protection, fault locator and also the differential protection will be affected in different ways.

The paper explains theory, shows simulation results and practical experiences with the different protection principles and compares these with the differential protection principle. The investigations on the above mentioned that physically caused measuring problems were proven by RTDS real-time simulation tests.


Madrid, SPAIN 304

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Distance Protections: What Limits of Use for Heavy Loaded Very High Voltage Lines

J.M. Grellier * (EDF, France), J.L. Chaneliere (RTE, France)

Summary To increase the load capacity of VHV lines, cables with low dilation coefficient were developed: for example, a beam of two 851mm² aluminium alloy cables whose maximum permanently acceptable intensity in summer is 2290A can be replaced by a beam of two 842mm² cables with low dilation coefficient which maximum permanently acceptable intensity in summer is 3400A (operated at 100°C) and 5280A (operated at 200°C).

These heavy loaded lines (up to 9000A in case of load transfer) raise a difficulty for distance protections because the load equivalent impedance is smaller than some short-circuit impedance. Moreover, the load transfer during single-phase reclosing cycles activates the phase-ground measurement loops.

An electrotechnical analysis of the risks of spurious operation or failure and a comparative study of the solutions by impedance blinders and power blinders are presented.

The electrotechnical study shows that:

the switch onto fault (SOTF) function shall be automatically switched off as soon as the live line criterion is present.

according to the tower geometry and the phase positions, the unbalance residual current can reach about 600A.

the solution by the powers P and Q is not usable on the lines between 2 substations of very strong power, because it is failing when the load is weak.

the combination of the high loads and the fault resistance obliges to have a reactive reach slope in zone 1 of about 45°. The corollary is that the single-phase faults of a resistance of about 10 ohms in the middle of the line are detected in zone 1 by none of the ends. In the same way, the nearby single-phase faults of a resistance of about 20 ohms are not detected in zone 1. Lastly, protections of a highly importing substation but of low short-circuit power almost do not detect the single-phase faults.

The load transfers during single-phase cycles are made on the parallel system if the short-circuit power of one substation is weak. The risky case is that of a resistive load with capacitive compensation shunt, which authorizes high transit while remaining within the contractual voltage limits: the corresponding phase of the parallel system sees its

* [email protected]


Madrid, SPAIN 305

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single-phase loop activated; the 2 systems will thus see a single-phase trip on the same phase. The use of blinders is effective but does not allow detection of the single-phase faults of a resistance of more than ten ohms.

The load transfers during single-phase cycles, if the 2 substations are of great short-circuit power, do not affect the parallel system but the other currents of each substations.

The tests carried out with the distance protection confirm these results.

Being given that the spurious operations must be excluded, the distance protection could be set only for low resistance faults and will not be able to detect an important proportion of faults. A plan of protection with 2 line differential current protections (from different manufacturers and with transmission channels without common mode) seems the only solution.

Keywords Distance protection, VHV lines, heavy loads.

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German Practice of Transmission System Protection

H-J. Herrmann (Siemens AG, Germany), A. Ludwig (Vattenfall Europe, Germany), H. Föhring (RWE TSO Strom, Germany), H. Kühn (E.ON Netz, Germany),

F. Oechsle (EnBW, Germany)

Summary The contribution describes typical protection concepts and the coordination of the protection relays for the different protected objects. These are generators of the power stations, the busbars, the transmission lines with there different configurations and the power transformers. The main focus at the power stations is the coordination with line protection and furthermore the power plant disconnection protection which is used on large generators is explained. The main protection for the busbars is the low impedance current differential protection. The typical requirements of a decentralized busbar protections are discussed. This includes redundancy concepts, tripping time requirements, the implementation of the breaker failure protection and also the bus coupler protection. Additionally the distance protection is used as a backup protection for the bus coupler. The main emphasis of the paper is the transmission line protection based on distance and line current differential protection. The present status of the protection solutions/schemes and the future concepts will be highlighted. The discussion also includes the dual main philosophies. The different positions of the utilities are shown. Different transmission line configurations are examined. Wind farms search for economic line connections. So tapped lines are established. An effective protection concept for these is the differential protection. Modern powerful communication channels advance this principle. In contrast the distance protection needs special settings and communication with the relays on the remote end is a prerequisite.

Keywords Transmission system, line protection, transformer protection, busbar protection, distance protection, differential protection.


Madrid, SPAIN 306

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Practical Experience With Multiple and Evolving Faults

H. Grünert (GSC Power Engineering GmbH, Germany)

Summary Today the distance protection is the protection principle most often applied on overhead lines for the levels 220kV and 380kV. The correct fault detection and the calculation of the fault position regarding the selected zone settings depend essentially on the conformity of voltages and currents with the applied model. The distance measurement is largely known, based on the 1st order-line-model using the positive sequence impedance of the protected object. The correct selection of the faulty measuring loop is essential, especially for multiple faults and in the presence of apparent loops. Particularly the tripping scheme of an associated auto reclosure is mainly influenced by the determined type of fault. Knowing the circumstances where these requirements are not fulfilled is important. In order to compensate for measuring errors, parameter tolerances and to provide nearly undelayed tripping for 100% of the protected object, communication schemes with overreaching zones are applied. Additionally, a directional earth fault comparison scheme can be used to operate in case of high ohmic faults.

Keywords Transmission system, line protection, distance protection, auto reclosing.


Madrid, SPAIN 307

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Coordination Experiences in Japanese Transmission System Protection

Toshiyuki Yamada (Tohoku Electric Power Co., Japan), Akira Takeuchi (Chubu Electric Power Co., Japan),

Fukashi Kumura (Kansai Electric Power Co., Japan), Hidyuki Kameda (Central Research Institute of Electric Power Industry, Japan),

Katsuhiko Sekiguchi1 (Toshiba Corporation, Japan)

Summary This paper describes several examples of protection systems and SPSs coordination based on practical experiences in the Japanese power systems. Japanese power systems are, from the viewpoint of protection, characterized mainly by the following two terms: resistance-grounded systems in a voltage class of 154 kV or less, and parallel double-circuit lines in all voltage classes. Protection schemes used in Japan are closely related to these features. Also, SPSs are widely used to maintain the stability of high-density power systems. Although the presented schemes and coordination issues are particular to Japan, they have wider applicability.

1 [email protected]


Madrid, SPAIN 308

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Practical Solutions to Autoreclosing on Transmission Lines

Dr. Ing. Stelian Gal / Dr. Ing. Florin Balasiu (Transelectrica, Romania) Dr. Ing. Traian Fagarasan / Dr. Ing. Gheorghe Moraru (SMART, Romania)

Keywords Autoreclosing Function, Line Protection Function.


Madrid, SPAIN 309

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Information Analysis of Power Transmission Line Observation for Three-Phase Short-Circuits

S. Ivanov2 / Y. Liamets (Research Centre Bresler) J. Zakonjsek (ABS Holdings)

G. Nudelman (VNIIR)

Abstract The paper provides information analysis of three phase short-circuits in on a tapped power transmission line with two power sources. It has been proven that it is impossible to maintain high identifiability when information about current is only available. To overcome this, it is suggested that from one side the line voltage should be added to the relay protection information base. Algorithm has been proposed that is based on algorithmic model and virtual relay method uses information about currents from both sides of the line. It has been shown that identifying features of the proposed algorithm are close to identification of a short-circuit as a physical phenomenon.

Keywords line differential protection – identifiability – virtual relay.

2 428000, Russia, Cheboksary, pr. I. Yakovleva, 1. E-mail: [email protected]

This work was supported in part by the Russian Foundation for Basic Research, Russia under Grant 07-08-00668-а


Madrid, SPAIN 310

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Electrical Power System Conditions Hierarchy in Methodology of Relay Protection Education

Y. Liametx/D. Kerzhaev/S. Ivanov/A. Podshivalin* (Research Centre BRESLER, Russia) J. Zakonjsek (ABS Holdings) G. Nudelman (VNIIR, Russia)

Abstract This report briefly presents the relay protection education theory. Education objective is seen as representation of simulation model conditions in the setting space. The main task is to identify the boundaries of conditions mappings. Education is based on a recurrent scheme when relay’s informational characteristics improve at each and every step. The theorems associated with description of the boundaries are developed. Relay education techniques are illustrated in closed-form solutions.

Keywords Transmission line protection – identifiability – setting space – alternative conditions.

3 428000, Russia, Cheboksary, pr. I. Yakovleva, 1. E-mail: [email protected]

This work was supported in part by the Russian Foundation for Basic Research, Russia under Grant 07-08-00668-а


Madrid, SPAIN 311

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Challenges in the Co-ordination of Transmission System Protection on Series-Compensated Lines

Anita Oommen (ESKOM Transmission, South Africa)

Abstract The South African economy in recent years has incurred an electricity demand growth rate of 3-4% per annum. Fossil powered plants constitute the bulk of generation supplied to the Eskom network, traditionally located close to coal sources in the north-eastern part of the country with high energy demand in the Cape area in the south-western parts of the country. Due to the absence of sufficient generation in this part of the country and with rapid energy demand growth in recent years, there has been an increased requirement for series compensation of lines down to the Cape, in order to permit adequate power transfer. When the compensation increases to over 50% of line impedance, there are more considerations necessary to ensure adequate co-ordination of protection settings and can become almost impossible in some instances. Compensation of up to 65% has been introduced on EHV (Extra High Voltage) lines down to the Cape. While permitting increased power transfer, this has introduced complications in the setting of protection relays on these lines. Older generation protection relays have difficulties in dealing with the voltage and current inversions that can be introduced in a compensated network. This has been catered for in more modern relays by the use of enhanced polarisation methods. Further complications are introduced with the migration of capacitor bank protection from spark-gap technology to newer MOV (Metal Oxide Varistor) technology. To ensure dependable and secure protection relay operation in the presently constrained EHV network, it is vital to ensure that all potential risks are clearly evaluated and understood. EMTP (Electromagnetic Transient Programs) software packages with relay modelling capability are used to evaluate the dynamic behaviour of such networks and ensure correct protection co-ordination. The protection of series compensated lines requires that Zone 1 be adjusted to cater for capacitor banks on local and adjacent lines not bypassing as well as sub-harmonic oscillations that are introduced as a result of resonance. In heavily compensated networks, Zone 1 may have to be reduced drastically or even disabled. This introduces compromised protection on these lines, as there is increased dependence on telecommunication-assisted tripping. The result is the dependence on the time-delayed operation of Zone 2 protection elements for fault clearance, should telecommunication systems fail. Higher compensation introduces very large reactive reaches to the overreaching zones of protection relays in order to ensure protection of the line when the capacitor bypasses. This introduces potential overreach when the capacitor banks do not bypass, as well as presents challenges in the co-ordination of backup protection zones. The result could be potentially disastrous over-tripping or prolonged fault duration, both of which could lead to a full or partial system blackout. Options considered to try and alleviate the problems thus introduced include adaptive tripping based on changing system conditions.

Keywords High energy demand, generation constraints, dislocation of load centres from sources, series-compensated networks, high compensation, Metal Oxide Varistors, voltage and current inversion, permissive tripping, sub-harmonic oscillations, capacitor magnification, protection co-ordination challenges.


Madrid, SPAIN 312

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Protection Coordination in the Transmission System and Boundaries Wide Area Coordination Study

Isabel de la Fuente dle Castillo(1) / Javier Martin Herrera / Carlos Puente Pérez (Red Eléctrica de España, Spain)

Summary Day after day our society has come to depend on the reliability of the Power System. This dependence makes it all the more critical to coordinate relay settings with those of the surrounding area. The lack of protection coordination increases interruptions in service and reduces system reliability.

In meshed transmission networks, the coordination is especially difficult because of the short-circuit power variability and changes in topology that affect the operation of the protective relays. A methodology has been developed to detect coordination problems in the transmission network and in the boundaries between transmission and generation systems and between transmission and distribution systems.

A complete study of the 220kV network in the northeast of Spain has been carried out. The correct and coordinated relay response is evaluated when each fault is simulated. The study statistics include the simulation of 510 protection relays and 40,000 faults. A commercially available protection simulation software which is able to perform a stepped-event simulation of a large portion of the protection system.

Two network study cases were considered: PEAK CASE, with all available generation connected, and OFF-PEAK CASE that considers generation disconnected for demand coverage and overhead lines disconnected for voltage control according to common operating practice. Both cases model the real time double busbar with bus coupler breaker configuration where available, in order to check the response of bus coupler relays.

For checking coordination only non-unit protection has been included in the study network model. Busbar differential, line differential, and transformer differential protective devices are non-time-delayed protection and are not analyzed. Communication failure for transfer trip distance protection is assumed. These choices are equivalent to considering a N-1 situation of the protection system. Therefore, only overcurrent and stepped-delayed distance relays are responsible for clearing the fault, as backup protections.

To categorize the coordination problems, an algorithm has been designed that detects an inadequate relay setting for a simulated fault, and attributes the failure in coordination either to RED ELECTRICA or to another utility (generator or distributor agent). This algorithm is based on RED ELECTRICA’s transmission network protection philosophy.

Three-phase and single-line-to-ground faults are simulated in the study. These faults are applied to all elements included in the coordination area. Two different network topologies have been defined for simulating faults, N Situation and N-1 situation with minimum infeed. The first one has all


Madrid, SPAIN 313

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network components in service; and the second one considers the overhead line or transformer contributing maximum current for a three-phase fault at the studied bus to be out of service.

The study revealed that most transmission coordination problems were caused by an incorrect operation of the neutral directional overcurrent (67N) and by an incorrect setting of the zone 2 distance relays.

Keywords Coordination- Miscoordination- Primary Protection- Backup Protection – Infeed.

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Hot And Cold Backup Protection As New Concepts In Protective Relaying

Jorge Cardenas (GE Multilin)

Abstract Hot and cold stand-by is a concept widely used in Power Generation. Hot stand-by represents the Power immediate availability to compensate any instantaneous possible loss in generation and cold stand-by represents the Power available to be used after certain conditions have been fulfilled but, in general, it can be defined as the total Power ready to be connected to the network on a time equal to the machine starting time.

In relays, the backup protection can be defined as a hot backup (active and ready to operate) and in general comprise a set of independent devices that are activated when the Main protection system either does not operate properly or it is not capable for clearing the fault.

In numerical relays there are many incorporated backup functions that are not used, because in order to maintain the reliability of the protection scheme, the users maintain the concept to use a duplicate hardware schemes of some backup functions as the breaker failure. The result is a lot of functionality available left unused.

The purpose of this paper is to establish some general recommendations to use all the functionally available without changing the actual protection philosophy of the users, but adding new possibilities that permit the improvement of the scheme, particularly when some device is totally out of service because an internal failure or because power supply failure or loss.


Madrid, SPAIN 314

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Protection of Combined Cable and Overhead Lines

S. López (REE, Spain), J.L. Martínez (IBERDROLA, Spain), J.M. Roca (Unión Fenosa, Spain), A. Montoya (GE Power Management, Spain), I. Zamora (ETSI Bilbao, Spain)

Summary High voltage transmission lines are the subject of increasing public opposition and continuous demands that must be under grounded. As a consequence, new lines, and in many cases existing lines also, must be buried totally or partially. This paper considers the difficulties associated with the protection of the new appearing so called “hybrid lines” defined as consisting of joint overhead/underground transmission media. Some recommendations, got from Spanish utilities experience, are given about practices to adopt on protective relaying, auto-reclosing and communications in these hybrid lines.

Keywords Hybrid lines – Underground lines - Protection practices – Reclosing practices – Fault location.


Madrid, SPAIN 315

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Problems and Solutions for AC Transmission Line Protection under Extreme Conditions caused by Very Long HVDC Cables

Stig Holst / Ivo Brnčič / David Shearer (ABB, Sweden), Ragnar Mangelred (Statnett, Norway), Kees Koreman (TenneT, Netherlands)

Summary NorNed is an HVDC link that will connect the 300 kV transmission system in Norway and the 400 kV transmission system in the Netherlands. The transmission capacity will be 700 MW and the voltage ±450 kV. The 580 km HVDC cable will be the longest submarine cable in the world. The link is scheduled to be commissioned at the end of 2007.

If commutation failures occur in the HVDC converter due to AC power system faults the DC cable capacitance will discharge. The DC cable discharge current will in some instances be injected into the faulty AC power system. As the NorNed cable is very long the discharge current will be of considerable magnitude and will expose the AC protection systems to extreme conditions.

Existing distance relays in the Norwegian power system were tested by Statnett by injection of calculated secondary fault voltages and currents including cable discharge currents. The result was that there is a considerable risk of unwanted operations for some distance relays in case of commutation failures in the HVDC link. It was concluded that distance protection relays are not suitable to use for some of the transmission lines and should be replaced by protection based on another principle.

It was decided to carry out comprehensive tests of a newly developed line differential relay to verify its ability to operate in these difficult applications. The main problem for the protection systems is saturation of the CTs caused by the DC discharge current. As the remanence of the closed core CTs is of major importance for the performance of the protection the tests were carried out with several combinations of remanence including extremely high levels of remanence such as 75 and 85 %.

The tests have verified that the tested line differential protection has the capability to operate correctly in power systems close to HVDC links with very long DC cables. The protection performed excellent and was stable for all relevant external fault cases. All internal faults were tripped and the average operate time was 24 ms. Minimum operate time was 20 ms and maximum 38 ms. The few operations with operate time > 30 ms occurred for cases with low fault currents and with 85 % remanence. Considering the difficult fault cases the average operate time of 24 ms is very good.

Keywords Line differential protection, HVDC, DC cable discharge current, CT saturation, remanence.


Madrid, SPAIN 316

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Advanced Techniques for Current Differential Feeder Protection

Takahiro Kase / Gareth Baber (Toshiba International –Europe- Ltd., United Kingdom)

Summary Current differential feeder protection is being applied ever more commonly as a main protection for transmission lines, largely due to its simplicity as a principle and also because of its ease of application. However, it is not commonly appreciated that many advanced functions and techniques have been implemented in recent current differential protection relays, bringing significant advantages to the user. While some of these are improvements to the basic functions of current differential relays, leading to improvements in performance in terms of operating time and sensitivity, others developments make use of the inherent availability of remote-end data to realise separate functions additional to the basic differential protection. Other innovations relate specifically to aspects of the performance of the communications channel utilised by the protection. In this paper some of these advanced features are introduced.

Keywords Current differential protection – Instantaneous values – Charging current compensation – Dual communication channel – Residual current differential protection – GPS synchronisation – Fault locator – Multi-phase auto-reclosing.


Madrid, SPAIN 317

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Advancements in Transmission Cable Protection, Control, and Monitoring

D. Tziouvaras (Schweitzer Engineering Laboratories, Inc., USA), S. Chano (Hydro-Québec, Canada)

Abstract High-voltage underground ac cables have significantly different electrical characteristics than overhead transmission lines. The cable sheath or shield grounding method has a major impact on the zero-sequence impedance of underground cables. Understanding how the underground cable grounding method affects the series sequence impedances is very fundamental to underground cable ground distance protection. In the paper, we briefly discuss the electrical characteristics of underground cables, how sheath bonding and grounding methods affect the compensated loop impedance, and the fundamental electrical characteristic differences between overhead transmission lines and cables. Finally, we discuss the application of short-circuit protection for high-voltage ac cables and present a number of cable protection application examples.

Keywords Cable Protection – Cable Shielding – Cable Electrical Characteristics – Distance Protection.


Madrid, SPAIN 318

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Improved Transmission Line Protection During Cascading Events

M. Kezunovic / C. Pang* (Texas A&M University, United States)

Summary Relay operations during cascading events play an important role for the power system stability. Without knowing the whole system information, distance relay may make wrong decision from the view of system reliability since it operates only according to local measurements. This paper introduces an improved transmission line protection scheme during cascading events. It utilizes the interactive method of system-wide and local monitoring and analysis tools for on-line automated analysis of protective relay operation. The new system-wide analysis tools based on Vulnerability Index (VI), Margin Index (MI), and Equivalent Parallel Path Approximation (EPPA) allow the vulnerable transmission lines of the system and vulnerable conditions to be identified. Then new local on-line monitoring and control tools are capable of analyzing performance of relay operation and informing the centralized tool about the outcomes that will be invoked to mitigate incorrect or undesirable relay action. A case study is presented to demonstrate the improved transmission line protection scheme using the new tools.

Keywords Transmission Line Protection, Security Analysis, Topological Processing, Power Flow, Distance Relay, Cascading Event.

* M. Kezunovic and C. Pang are with the Department of Electrical and Computer Engineering, Texas A&M University, College Station, TX 77843-3128, USA ( emails: [email protected], [email protected])


Madrid, SPAIN 319

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Transient Simulation Requirements for Testing of Transmission Line Protection Systems

Alexander Apostolov (OMICRON electronics, USA), Peter Meinhardt (OMICRON electronics, Austria),

Damien Tholomier (AREVA T&D Automation, Canada)

Keywords Transmission Line Protection, Functional Testing, Transient Simulation.


Madrid, SPAIN 320

Documents

301 Madrid, SPAIN Coordination of Protection · PDF fileare related to the proper relay coordination under different fault and system conditions. ... The accuracy of the fault location