C37.109-1988- Shunt Reactor protection

ANSI/IEEE C37.109-1988 An American National Standard IEEE Guide for the Protection of Shunt Reactors Sponsor IEEE Power Systems Relaying Committee of the IEEE Power Engineering Society Approved October 20, 1988 IEEE Standards Board Approved May 10, 1989 American National Standards Institute Abstract: ANSI/IEEE C37.109-1988 IEEE Guide for the Protection of Shunt Reactors, discusses the protection of shunt reactors used typically to compensate for capacitive shunt reactance of transmission lines. The more common circuit arrangements and protective relaying schemes presently in use are discussed and illustrated. Copyright © 1989 The Institute of Electrical and Electronics Engineers, Inc. 345 East 47th Street, New York, NY 10017-2394, USA No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher. 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Such adoption does not assume any liability to any patent owner, nor does it assume any obligation whatever to parties adopting the standards documents. iii Foreword (This Foreword is not a part of ANSI/IEEE C37.109-1988, IEEE Standard Guide for the Protection of Shunt Reactors.) This Guide was prepared by the Shunt Reactor Protection Working Group of the Substation Protection Subcommittee of the IEEE Power Systems Relaying Committee. At the time this Guide was approved, the working group membership was as follows: L. L. Dvorak, Chair D. C. Dawson R. W. Dempsey H. Disante C. M. Gadsden J. D. Huddleston, III L. J. Schulze At the time this Guide was approved, the Substation Protection Subcommittee membership was as follows: J. E. Stephens, Chair R. W. Dempsey, Vice Chair J. K. Akamine H. N. Banjeree E. A. Baumgartner J. J. Bonk S. P. Conrad C. J. Cool D. C. Dawson L. L. Dvorak S. E. Grier R. W. Haas R. E. Hart J. D. Huddleston, III G. C. Parr W. E. Reid L. J. Schulze J. W. Walton T. E. Wiedman The following persons were on the balloting committee that approved this document for submission to the IEEE Standards Board: C. H. Griffin, Chair J. R. Boyle, Vice Chair J. A. Zulaski, Secretary J. K. Akamine G. Y. R. Allen J. C. Appleyard R. F. Arehart C. W. Barnett E. A. Baumgartner R. W. Beckwith J. J. Bonk J. R. Boyle B. Bozoki J. A. Bright H. J. Calhoun J. W. Chadwick, Jr. D. M. Clark S. P. Conrad J. Criss D. C. Dawson R. W. Dempsey H. Disante P. R. Drum L. L. Dvorak W. A. Elmore J. T. Emery E. J. Emmerling J. Estergalyos W. E. Ferro R. J. Fernandez C. M. Gadsden A. T. Giuliante S. E. Grier C. H. Griffin R. W. Haas R. E. Hart R. W. Hirtler J. W. Hohn F. Huber, Jr. J. D. Huddleston, III J. W. Ingleson R. H. Jones E. W. Kalkstein T. L. Kaschalk W. N. Kennedy S. S. Kershaw K. J. Khunkhun W. C. Kotheimer S. R. Lambert L. E. Landoll J. R. Latham J. R. Linders F. N. Meissner J. Miller R. J. Moran C. J. Mozina J. J. Murphy T. J. Murray K. K. Mustaphi G. R. Nail S. L. Nilsson R. W. Ohnesorge G. C. Parr A. G. Phadke A. C. Pierce A. Politis J. M. Postforoosh L. J. Powell G. D. Rockefeller iv M. S. Sachdev E. T. Sage D. E. Sanford L. Scharf H. S. Smith J. E. Stephens A. Sweetana F. Y. Tajaddodi R. P. Taylor J. R. Turley E. A. Udren D. R. Volzka C. L. Wagner J. W. Walton T. E. Wiedman S. E. Zocholl A. Zulaski When the IEEE Standards Board approved this standard on October 20, 1988, it had the following membership: Donald C. Fleckenstein, Chair Marco Migliaro, Vice Chair Andrew G. Salem, Secretary Arthur A. Blaisdell Fletcher J. Buckley James M. Daly Stephen R. Dillon Eugene P. Fogarty Jay Forster* Thomas L. Hannan Kenneth D. Hendrix Theodore W. Hissey, Jr. John W. Horch Jack M. Kinn Frank D. Kirschner Frank C. Kitzantides Joseph L. Koepfinger* Irving Kolodny Edward Lohse John E. May, Jr. Lawrence V. McCall L. Bruce McClung Donald T. Michael* Richard E. Mosher L. John Rankine Gary S. Robinson Frank L. Rose Helen M. Wood Karl H. Zaininger Donald W. Zipse *Member Emeritus v CLAUSE PAGE 1. Introduction .........................................................................................................................................................1 2. References...........................................................................................................................................................1 3. Use of Reactors ...................................................................................................................................................2 4. Typical Reactor Protection..................................................................................................................................2 5. Reactor Construction and Characteristics ...........................................................................................................2 5.1 Dry Type .................................................................................................................................................... 3 5.2 Oil-Immersed ............................................................................................................................................. 3 6. Dry-Type Reactors—Application and Protection...............................................................................................4 6.1 Reactor Connections .................................................................................................................................. 4 6.2 Failure Modes and Types of Faults............................................................................................................ 4 6.3 System Considerations............................................................................................................................... 6 6.4 Relaying Practices...................................................................................................................................... 6 7. Oil-Immersed Reactors—Application and Protection ......................................................................................10 7.1 Reactor Connections ................................................................................................................................ 10 7.2 Failure Modes and Type of Faults Encountered ...................................................................................... 11 7.3 System Considerations............................................................................................................................. 11 7.4 Relaying Practices.................................................................................................................................... 12 8. Bibliography......................................................................................................................................................17 1 An American National Standard IEEE Guide for the Protection of Shunt Reactors 1. Introduction This guide covers protection of shunt reactors used typically to compensate for capacitive shunt reactance of transmission lines. A survey of shunt reactor protection, conducted in 1979 by the Shunt Reactor Protection Working Group of the IEEE Power System Relaying Committee, was used as a reference to determine the more common circuit arrangements and protective relaying schemes presently in use. Other arrangements or special applications of reactors such as harmonic filter banks, static var compensation (SVC), high voltage direct current (HVDC), or current-limiting reactors are not specifically addressed; however, the protective methods described in this guide are usually applicable to this equipment. 2. References This guide shall be used in conjunction with the following publications: [1] ANSI/IEEE C57.21-1981, Requirements, Terminology, and Test Code for Shunt Reactors Rated Over 500 kVA.1 [2] ANSI/IEEE C62.2-1987, IEEE Guide for Application of Gapped Silicone Carbide Valve-Type Surge Arresters for Alternating-Current Systems. [3] ANSI/IEEE C62.11-1987, IEEE Standard for Metal-Oxide Surge Arresters for AC Power Circuits. [4] ASEA Electric Recommendations for Protective Relays, Pamphlet ZF27-004E Reg. 4771. ASEA Brown Boveri, Protective Relay Division, Allentown, PA, 1985. 1ANSI/IEEE publications are aviailable from the Institute of Electrical and Electronics Engineers, Service Center, 445 Hoes Lane, P.O. Box 1331, Piscataway, NJ 08855-1331, or the Sales Department, American National Standards Institute, 1430 Broadway, New York, NY 10018. 2 Copyright © 1988 IEEE All Rights Reserved ANSI/IEEE C37.109-1988 IEEE GUIDE FOR [5] EDWARDS, L., CHADWICK, J. W., JR., RIESCH, H. A. and SMITH, L. E., Single-Pole Switching on TVA's Paradise-Davidson 500-kV Line Design Concepts and Staged Fault Test Results, IEEE Transactions on Power Apparatus and Systems, Vol PAS-90, Nov./Dec. 1971, pp. 2436–2450. [6] ENGELHARDT, K. H., EHV Line-Connected Shunt Reactor Protection Application and Experience, International Conference on Large High-Voltage Electric Systems, C.I.G.R.E, Paris, France, paper No. 34-09, 1984. [7] KIMBARK, E. W., Suppression of Ground-Fault Arcs on Single-Pole Switched EHV Lines by Shunt Reactors, IEEE Transactions on Power Apparatus and Systems, Vol. 83/No. 3, Mar. 1964, pp 285–290. [8] PICKETT, M.J., et al, Near Resonance Coupling on EHV Circuits, IEEE Transactions on Power Apparatus and Systems, Vol PAS-87, Aug. 1967, pp 322–325. [9] Power System Relaying Committee Report. Shunt Reactor Protection Practices. IEEE Transactions on Power Apparatus and Systems, Vol PAS-103, Aug. 1984, pp. 1970–1976. [10] S&C Electric Company, Chicago, IL. RD-3221 Operating Description, Aug. 1985. [11] Trench Electric, Toronto Ontario, Canada. Shunt Reactor Bulletin T100-35-02l, May 1984. 3. Use of Reactors Shunt reactors are used to provide inductive reactance to compensate for the effects of high charging current of long transmission lines and pipe-type cables. For light load conditions, this charging current can produce more leading reactive kVA than the system can absorb without risk of instability or excessively high voltages at the line terminals. 4. Typical Reactor Protection Two basic shunt-reactor configurations are considered: 1) Dry-type, connected ungrounded wye which are connected to the impedance-grounded tertiary of a power transformer. 2) Oil-immersed, wye-connected, with a solidly grounded or impedance-grounded neutral, connected to the transmission system. Major fault protection for dry-type reactors is achieved through over-current, differential, or negative-sequence relaying schemes, or by a combination of these relaying schemes. Protection for low-level turn-to-turn faults is provided by a voltage-unbalance relay scheme with compensation for inherent unbalance. Major fault protection for oil-immersed reactors is achieved through over-current relaying, differential relaying, or a combination of both. Protection for low-level turn-to-turn faults is provided by impedance, thermal, gas-accumulator, or sudden-pressure relays, or by a combination of these relays. 5. Reactor Construction and Characteristics The two general types of construction used for shunt reactors are dry-type and oil-immersed. The construction features of each type, along with variations in design, are discussed under the headings which follow. Copyright © 1988 IEEE All Rights Reserved 3 THE PROTECTION OF SHUNT REACTORS ANSI/IEEE C37.109-1988 5.1 Dry Type Dry-type shunt reactors generally are limited to voltages through 34.5 kV and are usually applied on the tertiary of a transformer which is connected to the transmission line being compensated. The reactors are of the air-core (coreless) type, open to the atmosphere, suitable for indoor or outdoor application. Natural convection of ambient air is generally used for cooling the unit by arranging the windings so as to permit free circulation of air between layers and turns. The layers and turns are supported mechanically by bracing members or supports made from materials such as ceramics, glass polyester, and concrete. The reactors are constructed as single-phase units and are mounted on base insulators or insulating pedestals which provide the insulation to ground and the support for the reactor. Because the dry-type shunt reactor has no housing or shielding, a high-intensity external magnetic field is produced when the reactor is energized. Care is thus required in specifying the clearances and arrangement of the reactor units, mounting pad, station structure, and any metal enclosure around the reactor or in the proximity of the reactor. A closed metallic loop in the vicinity of the reactor produces losses, heating, and arcing at poor joints; therefore, it is important to avoid these loops and to maintain sufficient separation distances. Shielding may be required when it is not possible to arrange dry-type units in an equilateral-triangle configuration isolated from external magnetic influences. This shielding is required to limit the impedance deviation between phases. Deviation from impedance values for reactors will result in a deviation from the actual MVAR rating. For the same range of applications, the primary advantages of dry-type air-core reactors, compared to oil-immersed types, are lower initial and operating costs, lower weight, lower losses, and the absence of insulating oil and its maintenance. The main disadvantages of dry-type reactors are limitations on voltage and kVA ratings and the high- intensity external magnetic field mentioned above. Because these reactors do not have an iron core, there is no magnetizing inrush current when the reactor is energized. 5.2 Oil-Immersed The two design configurations of oil-immersed shunt reactors are coreless type and gapped iron-core type. Both designs are subject to low-frequency longtime constant currents during de-energizing, determined by the parallel combination of the reactor's inductance and line capacitance. However, the gapped iron-core design is subject to more severe energizing inrush than the coreless type. Most coreless shunt reactor designs have a magnetic circuit (magnetic shield) which surrounds the coil to contain the flux within the reactor tank. The steel core-leg that normally provides a magnetic flux path through the coil of a power transformer is replaced (when constructing coreless reactors) by insulating support structures. This type of construction results in an inductor that is linear with respect to voltage. The magnetic circuit of a gapped iron-core reactor is constructed in a manner very similar to that used for power transformers with the exception that small gaps are introduced in the iron core to improve the linearity of inductance of the reactor and to reduce residual or remanent flux when compared to a reactor without a gapped core. Oil-immersed shunt reactors can be constructed as single-phase or three-phase units and are very similar in external appearance to that of conventional power transformers. They are designed for either self cooling or forced cooling. 4 Copyright © 1988 IEEE All Rights Reserved ANSI/IEEE C37.109-1988 IEEE GUIDE FOR 6. Dry-Type Reactors—Application and Protection 6.1 Reactor Connections Dry-type reactor banks are generally connected to the tertiary of a transformer bank as shown in Fig 1. Each wye- connected, ungrounded reactor bank can be switched individually on the supply side of the reactor bank, as shown in Fig 1, or on the neutral side, as shown in Fig 2. A grounding transformer having a grounded wye-connected primary and a broken-delta connected secondary, with a grounding resistor, as shown in Fig 1, is normally used on the tertiary circuit to provide a limited amount of ground current. The grounding transformer and the grounding resistor are sized for a continuous zero-sequence current at least equal to the zero-sequence current flowing through the tertiary-circuit capacitance to ground under ground-fault conditions. In addition, the grounding transformer must be rated for continuous application of line-to-line voltage in order to withstand a continuous ground fault on the tertiary. The grounding scheme for the tertiary is essentially a high-resistance method utilizing the broken-delta secondary of the grounding transformer to insert the resistance, as well as provide indication of a ground fault on the tertiary circuits. This method offers the following advantages: 1) The neutral is stabilized by the zero-sequence resistance. 2) The voltages to ground on the tertiary circuits due to switching are kept low. 3) Currents due to line-to-ground faults, the most prevalent type, are minimized; a few amperes are typical. 4) Excellent ground fault protection is afforded by the voltage relay across the resistor. 5) Any number of banks can be switched without sacrificing the foregoing advantages. Other tertiary grounding arrangements are possible, however, the multiple advantages of this method have gained wide acceptance and application. Surge arrester selection, coordination, and application for protection of shunt reactors is covered ANSI/IEEE C62.2- 1989 [2],2 and ANSI/IEEE C62.11-1987 [3]. 6.2 Failure Modes and Types of Faults The faults encounte