ANSI IEEE 262B-1977 Trial-Use Standard Dielectric Test Requirements for Power Transformers for Operation on Effectively Grounded Systems 345 kV and Above.pdf

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1、IEEE Trial-Use Standard DielectricTest Requirements for PowerTransformers forOperation on EffectivelyGrounded Systems 345 kV and AboveIEEE Std 262B-1977 (Trial-Use Supplement to IEEE Std 262-1973, ANSIC57.12.90-1973) IEEE Trial-Use Standard Dielectric Test Requirements for Power Transformers for Ope

2、ration on Effectively Grounded Systems 345 kV and Above Sponsor Transformers Committee of the IEEE Power Engineering Society Copyright 1977 by The Institute of Electrical and Electronics Engineers, Inc No part of this publication may be reproduced in any form, in an electronic retrieval system or ot

3、herwise, without the prior written permission of the publisher. William R. Kruesi, Chairman Approved March 3, 1977 IEEE Standards Board Ivan G. Easton, Secretary Irvin N. Howell, Jr, Vice Chairman William E. Andrus Jean Jacques Archambault Mark Barber Edward J. Cohen Warren H. Cook Louis Costrell R.

4、 L. Curtis David B. Dobson R. O. Duncan Charles W. Flint Jay Forster Ralph I. Hauser Joseph L. Koepfinger Irving Kolodny Benjamin J. Leon Thomas J. Martin Donald T. Michael Voss A. Moore William S. Morgan William J. Neiswender Ralph M. Showers Robert A. Soderman Leonard W. Thomas, Sr B. W. Whittingt

5、on Foreword (This foreword is not a part of IEEE Std 262B-1977, IEEE Trial-Use Standard Dielectric Test Requirements for Power Transformers for Operation on Effectively Grounded Systems 345 kV and Above.) Dielectric standards for power transformers are normally provided through ANSI C57.12.00, Gener

6、al Requirements for Distribution, Power, and Regulating Transformers and ANSI C57.12.90, Test Code for Distribution, Power, and Regulating Transformers. These standards had their origins in the days of ungrounded systems, rod-gap coordination, and generally conservative insulation levels. While modi

7、fications have been made to reflect modern practice, these standards have become increasingly difficult to apply in the case of transformers in the Extra High Voltage range. This new standard represents several years of work by the Working Group on revision of Dielectric Tests of the Transformers Co

8、mmittee of the IEEE Power Engineering Society to develop dielectric requirements in line with current technology. The key elements are: 1. Lower Lightning Impulse insulation levels. 2. Chopped wave insulation levels set at 110 percent of lightning impulse insulation levels. 3. Retention of the 83 pe

9、rcent relation between switching impulse and lightning impulse insula tion levels. 4. Establishment of phase-to-phase switching impulse insulation levels at 3.4 times maximum peak 60 Hz voltage to ground. 5. A new low-frequency test at 1.5 times maxiumum operating stress for one hour with the trans

10、former connected as in service. 6. Incorporation of partial discharge monitoring during the low-frequency test with a 150 micro volt limit. The Working Group on Revision of Dielectric Tests, of the Dielectric Tests Subcommittee, of the Transformer Committee, had the following membership at the time

11、this standard was developed and approved: E. J. Adolphson, Chairman G. W. Iliff, Secretary E. H. Arjeski C. Hurty P. J. Musil P. L. Bellaschi . Keil J. D. Phillips S. Bennon H. F. Light L. R. Stensland D. F. Buchanan H. B. Margolis R. C. Thomas G. S. Haralampu* S. P. Mehta E. R. Uhlig K. R. Highton

12、L. S. McCormick F. F. Willett C. C. Honey G. P. Michel Z. Zepic Z. E. Minkwitz, Sr Liaison, Surge Protective Devices Committee Notice of Trial Use Comments on this Trial-Use Standard are welcomed and should be addressed to the Secretary, IEEE Standards Board 345 East 47th Street New York, NY 10017 A

13、fter a trial-use period of approximately one year, the committee responsible for this document will prepare a revision that will take into consideration the experience resulting from the current document. That revision will be submitted to the Standards Board for approval as a full-status IEEE stand

14、ard. Contents SECTION PAGE 1. Scope 7 2. Insulation Levels3. Insulation Coordination 8 4. Bushing Requirements 9 5. General Test Procedures5.1 Factory Dielectric Tests5.2 Field Dielectric Tests5.3 Routine Tests5.4 Optional Tests5.5 Test Sequence5.6 Test Procedure 9 6. Lightning Impulse Test Procedur

15、es 10 6.1 Test Sequence for Winding Terminals6.2 Test Sequence for Neutral Terminals6.3 Low-Frequency Excitation6.4 Oscilloscope 16.5 Chopped-Wave Test 0 6.6 Connections for Lightning Impulse Tests 16.7 Lightning Impulse Wave Considerations 1 6.8 Detection of Failure During Lightning Impulse Test 17

16、. Switching Impulse Test Procedures 12 7.1 Procedures 17.2 Connections7.3 Number of Tests7.4 Switching Impulse Waves7.5 Failure Detection 2 8. Applied-Potential Test Procedures 13 8.1 Connections 18.2 Resistance 4 8.3 Relief Gap8.4 Duration and Frequency8.5 Failure Detection9. Low-Frequency Induced

17、Test Procedures 14 9.1 Connections 19.2 One-Hour Test9.3 Internal Partial Discharges9.4 Failure Detection 5 10. Referenced StandardsTABLES Table 1 Insulation Levels for Terminals 362 kV and Above 8 Table 2 Insulation Levels for Terminals 230 kV and BelowTable 3 Applied-Potential Insulation Levels fo

18、r Delta Windings 9 FIGURE Fig 1 Connections for Making Switching Surge Tests on 3-Phase Transformers Using an Impulse Generator (Cg) Discharging into the Low-Voltage Windings 13 IEEE Trial-Use Standard Dielectric Test Requirements for Power Transformers for Operation on Effectively Grounded Systems

19、345 kV and Above 1. Scope 1.1 This standard prescribes insulation levels and dielectric test requirements for power transformers where: (1) The transformer insulation levels and di electric test requirements are specified to be in accordance with this standard.1 (2) The highest voltage winding of th

20、e trans former is wye connected and rated 345 kV or above. (3) The transformer is intended for operation on an effectively grounded system2 and is pro tected by suitable surge arresters. 1.2 These requirements, when specified, super sede all requirements relative to insulation levels, dielectric tes

21、ts, dielectric test methods, or bushings as contained in Sections 4, 8, and 9 of ANSI C57.12.00-1973 (IEEE Std 462-1973) and Section 3 of ANSI C57.12.90-1973 (IEEE Std 262-1973). 2. Insulation Levels 2.1 Each winding terminal 362 kV and above shall be assigned a Basic Lightning Impulse Insulation Le

22、vel (BIL), as chosen from Table 1, which shall indicate the factory dielectric tests which the terminal is capable of withstanding. Selection of a given BIL determines not only the lightning impulse insulation level but also 1li the user does not wish to employ this standard, or if the transformer d

23、oes not fall within the scope of this standard, the insulation levels and dielectric test requirements shall normally be in accordance with ANSI C57.12.00, General Requirements for Distribu tion, Power, and Regulating Transformers (IEEE Std 462-1973) and ANSI C57.12.90, Test Code for Dis tribution,

24、Power, and Regulating Transformers (IEEE Std 262-1973). 2The ratio of zero-sequence reactance to positive-sequence reactance shall not exceed 3, and the ratio of zero-sequence resistance to positive-sequence re-the chopped wave insulation level, the phase-to-ground switching impulse insulation level

25、, and the phase-to-phase switching impulse in sulation level. The low frequency phase-to-ground insulation level shall be 1.5 times the maximum system voltage as listed in Table 1. 2.2 Each winding terminal 230 kV and below shall be assigned a BIL as chosen from Table 2, which shall indicate the fac

26、tory lightning impulse and chopped wave tests which the terminal is capable of withstanding. Each wind ing terminal 230 kV and below shall also be capable of withstanding dielectric stresses re sulting from switching impulse tests and low-frequency tests imposed on the high voltage terminals. 2.3 Ne

27、utral terminals shall normally be as signed a BIL of 110 kV; however, other con siderations, such as lack of effective grounding on low voltage windings or the use of current limiting reactors between neutral and ground, may require that an appropriately higher BIL be specified. 2.4 All windings des

28、igned for delta connection shall be capable of withstanding an applied-potential test for one minute at the level speci fied in Table 3. 2.5 All windings designed for wye connection shall be capable of withstanding an applied-potential test at 34 kV; however, other con siderations, such as lack of e

29、ffective grounding on low voltage windings or the use of current limiting reactors between neutral and ground, may require that an appropriately higher level be specified. actance shall not exceed 1. This will normally limit the voltage on the unfaulted phase during a phase-to-ground fault to 1.3 pe

30、r unit of the phase-to-ground value for the normal time to clear the fault. If system conditions or connections are such that higher temporary overvoltages or sustained overvoltages may occur, then suitable low-frequency induced and ap plied potential test levels shall be specified by the user. 7 IE

31、EE Std 262B-1977 IEEE TRIAL-USE STANDARD DIELECTRIC TEST REQUIREMENTS Table 1 Insulation Levels for Terminals 362 kV and Above Maximum System Voltage*, kV Column 1 362 550 800 Basic Lightning Impulse Insulation Level (BIL), kV Crest Column 2 900 1050 1175 1300 1425 1550 1675 1800 1925 2050 Chopped W

32、ave Insulation Level, kV Crest Column 3 990 1155 1290 1430 1570 1705 1845 1980 2120 2255 Phase-to-Ground Switching Impulse Insulation Level, kV Crest Column 4 745 870 975 1080 1180 1290 1390 1500 1600 1700 Phase-to-Phase Switching Impulse Insulation Level, kV Crest Column 5 1050 1050 1050 1550 1550

33、1550 1550 2300 2300 2300 Low-Frequency Phase-to-Ground Insulation Level, kV rms Column 6 315 315 315 475 475 475 475 690 690 690 System voltage is based on maximum operating voltage in accordance with ANSI C92.2-1974. NOTES: (1) Depending on the levels involved and the type of transformer design, it

34、 may be necessary to exceed the speci fied phase-to-phase switching impulse test levels in order to meet the specified phase-to-ground switching impulse test levels. (2) Where specified by the user and where “better than effective grounding“ is employed, the low-frequency phase-to-ground insulation

35、level may be reduced in the case of 1300 kV BIL for 550 kV system voltage and 1800 kV BIL for 800 kV system voltage. Table 2 Insulation Levels for Terminals 230 kV and Below System L Voltage*, kV 14.4 and below 23 34.5 46 69 115 138 161 230 Basic Lightning Impulse Insulation Level (BIL), kV Crest 11

36、0 150 200 250 250 350 350 450 450 550 550 650 650 750 Chopped Wave Insulation Level, kV Crest 125 165 220 275 275 385 385 500 500 605 605 715 715 825 System voltage is based on nominal voltages in accordance with ANSI C84.1-1970, Voltage Ratings for Electric Power Systems and Equip ment (60 Hz). 3.

37、Insulation Coordination 3.1 The BIL chosen for each winding terminal shall be such that the lightning impulse, chopped wave impulse, and phase-to-ground switching impulse insulation levels include a suitable margin in excess of the surge arrester protective levels available at that terminal. For inf

38、ormation on surge arrester characteristics and application, refer to ANSI C62.1-1975, Surge Arresters for Alternating-Current Power Circuits (IEEE Std 28-1974), and ANSI C62.2-1969, Guide for Application of Valve Type Lightning Arresters for Alternating-Current Systems. 8 FOR POWER TRANSFORMERS - 34

39、5 kV AND ABOVE IEEE Std 262B-1977 3.2 A switching surge impulse occurring at one terminal during test or in actual service will be transferred to other winding terminals with a magnitude approximately proportional to the turns ratios involved. This interaction must be considered when evaluating surg

40、e arrester ap plication, expected magnitude of surges, and establishment of insulation levels. 4. Bushing Requirements 4.1 The bushings shall be capable of with standing all tests required to be performed on the transformer. 4.2 Each transformer, if possible, should be tested with the bushings that

41、are to be supplied with that transformer. 4.3 Where applicable, bushings shall be in con formance with IEEE Std 21-1976, General Requirements and Test Procedure for Out door Apparatus Bushings (ANSI C76.1-1976). Transformers using bushings having dimen sions in accordance with IEEE Std 24-1977, Elec

42、trical, Dimensional, and Related Require ments for Outdoor Apparatus Bushings (ANSI C76.2-1977) shall have bushing mounting holes adequate to accommodate the maximum P di mensions for those bushings, as shown in the applicable tables. 5. General Test Procedures 5.1 Factory Dielectric Tests. The purp

43、ose of dielectric tests in the factory is to demonstrate that the transformer has been designed and constructed to withstand the specified in sulation levels. 5.2 Field Dielectric Tests. Dielectric tests in the field may be warranted on the basis of detec tion of combustible gas or other circumstanc

44、es. However, periodic dielectric tests are not rec ommended because of the severe stress im posed on the insulation. Where field dielectric tests are required, low-frequency applied-potential and induced-poten-Table 3 Applied-Potential Insulation Levels For Delta Windings System Voltage*, kV 14.4 an

45、d below 23 34.5 46 69 Test Level, kV rms 34 50 70 95 140 System voltage is based on nominal voltages in ac cordance with ANSI C84.1-1970, Voltage Ratings for Electric Power Systems and Equipment (60 Hz). tial tests shall be used, and the phase-to-ground or phase-to-phase voltage stress imposed shall

46、 not exceed 150 percent of normal operating voltage. The duration of the test shall not ex ceed 5 minutes. The test frequency, when in ducing a transformer in excess of its rated voltage, should be increased as necessary to avoid core saturation. 5.3 Routine Tests. Lightning impulse tests on winding

47、 terminals, phase-to-neutral switching impulse tests, applied-potential tests, and low-frequency induced tests shall be per formed on all transformers. 5.4 Optional Tests. Lightning impulse tests on neutral terminals shall be peformed only when specified. Phase-to-phase switching impulse tests shall

48、 be performed only when specified and where the transformer has a three-legged core or a delta winding to facilitate the test. This test shall normally be made on only one transformer of a given rating, except that this test shall be omitted when a record of such test made in accordance with this st

49、andard on a duplicate or essentially duplicate unit is avail able. 5.5 Test Sequence. The tests may be performed in any sequence providing that the low-fre quency tests (applied and induced tests) fol low the transient tests (lightning impulse, chopped wave, phase-to-ground switching im pulse, and phase-to-phase switching impulse tests). 5.6 Test Procedure. Dielectric tests shall be made in accordance with IEEE Std 4-1969, Techniques for Dielectric Tests (ANSI C68.1-1968). 9 IEEE Std 262B-1977 IEEE TRIAL-USE STANDARD DIELECTRIC TEST REQUIREMENTS 6. Lightning Impulse Test Procedures 6.1 T