ANSI IEEE C57 12 21-1992 Requirements for Pad-Mounted Compartmental-Type Self-Cooled Single-Phase Distribution Transformers With High Voltage Bushings High-Volt.pdf

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1、 The Institute of Electrical and Electronics Engineers, Inc.3 Park Avenue, New York, NY 10016-5997, USACopyright 2003 by the Institute of Electrical and Electronics Engineers, Inc.All rights reserved. Printed in the United States of America.Print:ISBN 0-7381-3624-7 SH95108PDF:ISBN 0-7381-3625-5 SS95

2、108No 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.ANSI C57.12.21-1992American National StandardRequirements for Pad-Mounted, Compartmental-Type Self-Cooled,Single-Phase Distribution Tran

3、sformersWith High Voltage Bushings; High-Voltage, 34500 GRYD/19920 Volts and Below; Low-Voltage, 240/120 Volts; 167 kVA and SmallerApproved 5/7/92American National Standards Institute, Inc.Approval of an American National Standard requires verification by ANSI that the requirements for due process,

4、consensus, and other criteria for approval have been met by the standards developer. Consensus is established when, in the judgment of the ANSI Board of Standards Review, substantial agreement has been reached by directly and materially affected interests. Substantial agreement means much more than

5、a simple majority, but not necessarily unanimity. Consensus requires that all views and objections be considered, and that a concerted effort be made toward their resolution. The use of American National Standards is completely voluntary; their existence does not in any respect preclude anyone, whet

6、her he has approved the standards or not, from manufacturing, marketing, purchasing, or using products, pro cesses, or procedures not conforming to the standards. The American National Standards Institute does not develop standards and will in no circumstances give an interpretation of any American

7、National Standard. Moreover, no person shall have the right or authority to issue an interpretation of an American National Standard in the name of the American National Standards Institute. Requests for interpretations shall be addressed to the secretariat or sponsor whose name appears on the title

8、 page of this stand ard. CAUTION NOTICE: This American National Standard may be revised or withdrawn at any time. The procedures of the American National Standards Institute require that action be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of approval

9、. Purchasers of American National Standards may receive current information on all standards by calling or writing the American National Standards Institute. Published by National Electrical Manufacturers Association 130 0 N. 17th Street, Rosslyn, Virginia 22209 Copyright 1996 National Electrical Ma

10、nufacturers Association All rights reserved. No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without prior written permission of the publisher. Printed in the United States of AmericaAmerican National Standard i ANSI C57.12.21 - 1992 CONTENT

11、S Page Foreword . iv 1 Scope 1 2 References 1 2.1 General . 1 3 Ratings 2 3.1 Kilovolt - ampere ratings . 2 3.2 Voltage ratings and tap rat ings . 2 4 Basic lightning impulse insulation levels and dielectric test levels 3 5 Tests . 3 5.1 General . 3 5.2 Dielectric tests 3 6 Construction 3 6.1 Genera

12、l . 3 6.2 Bushings and terminals 4 6.3 High - voltage and low - voltage compartments . 4 6.4 Instruction nameplate . 5 6.5 Oil preservation 5 6.6 Tanks 5 7 Storage and installation . 6 7.1 Storage . 6 7.2 Installation . 6 8 Other requirements that may be specified for some applications . 6 ii ANSI C

13、57.12.21 - 1992 Foreword (This Foreword is not part of Amer ican National Standard C57.12.21 - 1992) The Accredited Standards Committee on Transformers, Regulators, and Reactors, C57, has for a number of years been developing and correlating standards on transformers and regulators. The data used in

14、 this work have been gathered from many sources, including the standards of the Institute of Electrical and Electronics Engineers and the National Electrical Manufacturers Association, reports of committees of the Edison Electric Institute, and others. This standard was p repared by the Working Grou

15、p of the Subcommittee on Distribution Transformers, Overhead and Pad - Mounted, C57.12.2, and is a revision of the 1986 edition. Added to this revision are sections on storage and installation with emphasis being placed on the actual position when stored and the consideration of the angle of tilt wh

16、en installed. At the time of approval, the Working Group members were as follows: Gerald A. Paiva, Chair A. Ghafourian M. Mingoia R. Stahara K. Hanus D. Peters J. Valdes J. Malloy R. Scheu D. Whitley This standard was processed and approved for submittal to ANSI by Accredited Standards Committee on

17、Transformers, Regulators, and Reactors, C57. Committee approval of the standard does not necessarily imply that all committee members voted for its approval. At the time it approved this standard, the C57 Committee had the following members: Chairman: P. J. Hopkinson, NEMA Delegation Vice Chairman:

18、J. C. Thompson, EL High - Voltage, 34500 GRDY/19920 Volts and Below; Low - Voltage, 240/120 Volts; 167 kVA and Smaller 1 Scope This standard is intended for use as a basis for determining performance, interchangeability, and safety of the equipment covered, and to assist in the proper selection of s

19、uch equipment. 1.2 This standard covers certain electrical, dimensional, and mechanical characteristics and takes into consideration c ertain safety features of single - phase, 60 Hz, mineral - oil - immersed, self - cooled, pad -mounted, compartmental - type distribution transformers with high - vo

20、ltage bushings. These transformers are rated 167 kVA and smaller, with high - voltages of 34500 GRD/19900 volts and below for operation between one phase and grounded neutral, and low - voltage of 240/120 volts. These transformers are generally used for step - down purposes from an underground prima

21、ry cable supply. NOTE Refer to latest federal regulations concern ing polychlorinated biphenyl (PCB) contaminations in transformers. 1.3 This standard covers bushing and terminal arrangements for both radial and loop feed systems. 1.4 This standard does not cover the electrical and mechanical requir

22、ements of any accessory devices that may be supplied with the transformer. 2 References 2.1 General All characteristics, definitions, terminology, voltage designations, and tests, except as otherwise specified herein, shall be in accordance with the following American Natio nal Standards (see 2.2):

23、ANSI C57.12.00 - 1987, American National Standard Requirements for Overhead - Type Distribution Transformers, 500 kVA and Smaller; High - Voltage, 34,500 Volts and Below; Low Voltage, 7970/13800 Y Volts and Below. ANSI C57.12.20 -1988, American National Standard Requirements for Overhead - Type Dist

24、ribution Transformers, 500 kVA and Smaller; High - Voltage, 34,500 Volts and Below; Low - Voltage, 7970/13800 Y Volts and Below. ANSI C57.12.28 - 1988, American National Standard for Switchgear and T ransformers Pad - Mounted Equipment Enclosure Integrity . ANSI C57.12.70 - 1978 (Reaff. 1987), Ameri

25、can National Standard Terminal Markings and Connections for Distribution and Power Transformers. ANSI C57.12.80 - 1978, American National Standard Terminology for Power and Distribution Transformers. ANSI C57.12.90 - 1987, American National Standard Test Code for Liquid - Immersed Distribution, Powe

26、r, and Regulating Transformers and Guide for Short - Circuit Testing of Distribution and Power Transformers. ANSI C57.12.21 - 1992 2 ANSI/IEEE C5 7.12.91 - 1981, American National Standard Guide for Loading Mineral - Oil - Immersed Overhead and Pad - Mounted Distribution Transformers Rated 500 kVA a

27、nd Below with 65 C or 55 C Average Winding Rise . 2.2 Revision of American National Standards referred to in this document. When an American National Standard referred to in this document is superseded by a revision approved by the American National Standards Institute, Inc., the latest revision sha

28、ll apply. 3 Ratings 3.1 Kilovolt - ampere ratings Kilovoltampere r atings shall be continuous and based on not exceeding either a 65 C average winding temperature rise or an 80 C hotspot conductor temperature rise. The temperature rise of the insulating oil shall not exceed 65 C when measured near t

29、he top of the tank. These kilovolt - ampere ratings are based on the usual temperature and altitude service conditions specified in ANSI/IEEE C57.12.00. The kilovolt - ampere ratings shall be as follows: 25 75 37.5 100 50 167 3.2 Voltage ratings and tap ratings 3.2.1 Voltage r atings shall be in acc

30、ordance with table 1. 3.2.2 No taps shall be provided. Table 1 Transformer high - voltage ratings and insulation levels High - Voltage Rating (Volts) Minimum BIL (kV) 4160 GrdY/2400 60 8320 GrdY/4800 75 12000 GrdY/6930 95 12470 GrdY/7200 95 13200 GrdY/7620 95 13800 GrdY/7970 95 16340 GrdY/9430 95 22

31、860 GrdY/13200 125 23900 GrdY/13800 125 24940 GrdY/14400 125 34500 GrdY/19920 150 4 Basic lightning impulse insulation levels and dielectric test levels 4.1 Basic lightning impu lse insulation levels (BILs) shall be in accordance with table 1 and 6.2.1. 4.2 Dielectric test levels shall be in accorda

32、nce with the distribution levels in ANSI/IEEE C57.12.00. ANSI C57.12.21 - 1992 3 5 Tests 5.1 General Except as specified in 5.2, tests shall be performed as specified in ANSI/IEEE C57.12.00 and ANSI/IEEE C57.12.90. 5.2 Dielectric tests No applied voltage test is required on the high voltage winding.

33、 Induced voltage tests shall be performed by applying between the terminals of one winding a voltage that wil l develop from the high - voltage line terminals to ground a voltage of 1000 volts plus 3.46 times the rated transformer winding voltage, in no case shall the line to ground voltage develope

34、d exceed 40,000 volts for 125 kV BIL and 50,000 volts for 150 kV BIL. For this test the neutral terminal shall be grounded. 6 Construction 6.1 General A pad - mounted, compartmental - type transformer shall conform to ANSI C57.12.28 and consist of a tank with high voltage and low - voltage cable ter

35、minating compartment, as sho wn in figure 1. The compartment shall be separated by a barrier of metal or other rigid material. 6.1.1 The high - voltage and low - voltage compartments shall be located side - by - side on one side of the transformer tank. When viewed from the front, the low - voltage

36、compartment shall be on the right. 6.1.2 Access to the terminal compartments shall be provided by a single door or by individual compartment doors. If individual compartment doors are provided, they shall be so constructed as to provide access to hi gh - voltage compartment only after the door to th

37、e low - voltage compartment has been opened. There shall be one or more additional captive fastening devices that must be disengaged before the high - voltage door can be opened. Where the low - voltage compartment door is of a flat - panel deign, or where only a single door is provided, the door sh

38、all have three - point latching with a handle provided for a locking device. If a lift - up hood or single door provides access to both the high - voltage compartment and the lo w - voltage compartment, one -point latching with provision for a locking device shall be provided, along with an addition

39、al door or lift - out panel that must be removed before access can be gained to the high - voltage compartment. 6.1.3 The bottom edges of the compartments shall be so constructed as to provide for the use of hold -down devices accessible only from inside the compartments. 6.1.4 The construction of t

40、he unit shall be such that it can be lifted, skidded, or slid, or a combination of these, into p lace on the mounting surface without disturbing the high - voltage or low - voltage cables. 6.1.5 The transformer base shall be arranged for rolling in two directions; parallel to and at right angles to

41、one side of the transformer. 6.1.6 The lifting provisions shall be on the tank to provide a distributed balanced lift in a vertical direction for the completely assembled transformer and shall be designed to provide a safety factor of 5. The safety factor of 5 is the ratio of the ultimate stress of

42、the materia l used to be working stress. The working stress is the maximum combined stress developed in the lifting provisions by the static load of the completely assembled transformer. ANSI C57.12.21 - 1992 4 6.2 Bushings and terminals 6.2.1 The electrical characteristics and clearances of the com

43、pletely assembled high - voltage bushing and low - voltage terminals shall be as shown in table 2. Table 2 Electrical characteristics and minimum electrical clearances of high - voltage bushings and low - voltage terminals Rating (volts) BIL (kV) 6 0 Hz Dry - One - Minute Withstand (kV) Minimum Clea

44、rance Live Parts to Ground* (Inches) 240/120 30 10 1 4160 GrdY/2400 60 21 2 - 1/2 8320 GrdY/4800 75 27 3 - 1/2* 12000 GrdY/6930 to 16340 GrdY/9430 95 35 5* 22860 GrdY/133200 to 24940 grdY/14400 125 42 5 - 3/4* 34500 GrdY/19920 150 70 8* * These dimensions should be increased wherever possible to all

45、ow the user ease in making connections. *Where clearances are less than those shown, an adequate non - hygroscopic insulating barrier shall be provided, but in no case shall the dimension between live parts and the barrier be less than four inches for 150 BIL, three inches for others. The use of bar

46、riers shall not reduce the above electrical characteristics. 6.2.2 The number, location, and arrangement of the high - voltage bushings and low - voltage terminals shall be as shown in figure 1. 6.2.3 High -voltage bushings shall have tinned copper alloy clamp -type connectors and shall be arranged

47、fro vertical take - off. The clamp connectors shall accommodate No. 8 AWG s olid to 2/0 AWG stranded conductors and shall be as shown in figure 2. 6.2.4 The H 2 end of the high - voltage winding shall be securely connected internally to the grounded clamping structure or the tank. This connection sh

48、all be independent of all other electrical connections. 6.2.5 Low - voltage line and neutral terminals shall be in accordance with figure and arranged for vertical take - off. Terminal dimensions shall be as shown in figure 3. 6.2.6 The low - voltage neutral shall be either a blade connected d irect

49、ly to the tank or a fully insulated terminal. If a fully insulated terminal is used, a ground pad shall be provided on the outer surface of the tank. One or more removable ground straps suitably sized for the short - circuit rating of the transformer as defined in ANSI C57.12.00 shall be provided and connected between the low - voltage neutral terminal and ground pad. 6.2.7 Bushing and terminal designations shall be as defined in ANSI C57.12.70. The high - voltage bushing and low voltage terminal designatio ns and locations