IEEE 43-1974 - IEEE Recommended Practice for Testing Insulation Resistance of Rotating Machinery.pdf

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1、ANSI/IEEE Std 43-1974 (IEEE Reaffirmed 1984) (Revision of IEEE Std 43-1961) (ANSI Reaffirmed 1986) IEEE Recommended Practice for Testing Insulation Resistance of Rotating Machinery Published by The Institute of Electrical and Electronics Engineers, Inc 345 East 47th Street, New York, NY 10017, USA S

2、H20438 November 12, I974 ANSI/IEEE Std 43-1974 (IEEE Reaffirmed 1984) (ANSI Reaffirmed 1986) (Revision of IEEE Std 43-1961) An American National Standard IEEE Recommended Practice for Testing Insulation Resistance of Rotating Machinery Sponsor Rotating Machinery Committee of The IEEE Power Engineeri

3、ng Society Approved May 30,1974 Reaffirmed December 20,1979 Reaffirmed December 13, 1984 IEEE Standards Board Approved September 7,1977 Reaffirmed December 22,1981 Reaffirmed September 25, 1986 American National Standards Institute Copyright 1974 by The Institute of Electrical and Electronics Engine

4、ers, Inc 345 East 47th Street, New York, NY 10017, USA No part of this publication muy be reproduced in any form, in an electronic retrimal system ur otMirise, without prior imittm pmisswn of the publisher. IEEE Standards documents are developed within the Technical Com- mittees of the IEEE Societie

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13、th Street New York, NY 10017 USA Approved May 30, 1974 IEEE Standards Board Joseph L. Koepfinger, Chairman Sava 1. Sherr, Secretary Jacques J. Archambault Irvin N. Howell, Jr Saul Aronow Irving Kolodny Robert D. Briskman William R. Kruesi Dale R. Cochran Benjamin J. Leon Warren H. Cook Anthony C. Lo

14、rdi Louis Costrell Donald T. Michael Charles W. Flint Voss A. Moore Jay Forster Warren H. Cook, Vice-Chairman William S. Morgan Harvey C. Nathanson James D. M. Phelps Saul W. Rosenthal Gustave Shapiro Ralph M. Showers Robert A. Soderman William T. Wintringham Foreword (This foreword is not a part of

15、 IEEE Std 43-1974, IEEE Recommended Practice for Testing Insulation Resistance of Rotating Machinery.) Insulation resistance measurement has been recommended and used for more than half a cen- tury to evaluate the condition of electric insulation. Whereas individual insulation resistance measurement

16、s may be of questionable value, the carefully maintained record of periodic measure- ments accumulated over months and years of service, is of unquestioned value as a measure of the condition of the electrical insulation. Originally, in 1950, this Recommended Practice was pub- lished by the AIEE as

17、a Guide to present the various facets associated with the measurement and understanding of electrical insulation resistance. The Guide was revised in 1961. With this publi- cation as a Recommended Practice, the IEEE is presenting and recommending electrical insula- tion resistance measurement as an

18、important factor in monitoring the condition of electrical in- sulation in rotating machinery. This Recommended Practice was prepared by a working group of the Insulation Subcommittee of the Rotating Machinery Committee of the IEEE Power Engineering Society. Working group personnel were: R. F. Sharr

19、ow, Chairman J. M. Brown A. W. W. Cameron E. B. Curdts R. J. Hillen W. J. Sheets G. Wolff Contents SECTION 1 . Scope . PAGE . 7 . 7 2 . Purpose 3 . Insulation Resistance-General Theory, Use, Limitations . 7 4 . Factors Affecting Insulation Resistance . 8 5 . Uniform Conditions for Measuring Insulati

20、on Resistance . 11 6 . Winding Connections for Insulation Resistance Tests . 11 7 . Methods of Measuring Insulation Resistance: Precautions . 12 8 . 9 . Interpretation of Insulation Resistance Test Results . 13 Recommended Minimum Value of Polarization Index and Insulation Resistance . 13 10 . Stand

21、ards References . 14 APPENDIX A1 . Prevention of Moisture Absorption in Winding Insulation . 15 A2 . Removal of Moisture From Winding Insulation . A3 . Methods of Heating Machine Windings . 16 FIGURES Fig 1 Fig 2 Fig 3 15 Approximate Insulation Resistance Variation with Temperature Typical Variation

22、 of Insulation Resistance with Time for Class B Change in 1 min and 10 min Insulation Resistance During the Drying for Rotating Machines . 9 Insulated Alternating-Current Armature Windings . 10 Process of a Class B Insulated Alternating-Current Armature Winding . 11 An American National Standard IEE

23、E Recommended Practice for Testing Insulation Resistance of Rot at ing Machinery 1. Scope 1.1 This document describes the recommend- ed procedure for the measurement of insula- tion resistance of windings of rotating ma- chines rated l hp, l kW or greater. It applies to synchronous machines, in- duc

24、tion machines, direct-current machines, and synchronous converters. It applies to armature windings and field windings. It does not apply to fractional-horsepower machines. 1.2 This document describes insulation re- sistance characteristics of rotating-machine windings, the manner in which these cha

25、rac- teristics may serve to indicate the condition of the winding, and the testing procedure for ob- taining insulation resistance values. It gives the recommended minimum value of insula- tion resistance of alternating-current and di- rect-current rotating-machine windings. The Appendix gives maint

26、enance information rel- ative to dry-out procedure. 1.3 Other IEEE publications which include information on insulation resistance measure- ment are listed in Section 10. 2. Purpose The purpose of this publication is to: (1) Describe and define insulation resist- ance as applied to the winding of a

27、rotating machine (2) Review the factors which affect or change insulation resistance characteristics and recommend uniform test conditions (3) Outline and recommend uniform meth- ods for measuring insulation resistance to- gether with precautions for avoiding er- roneous results (4) Provide a basis

28、for interpreting insula- tion resistance test results to estimate the suitability of the winding for service or for overpotential test. (5) Present equations, based on machine ratings, for the calculation of recommended minimum insulation resistance values for various types of rotating machines. 3.

29、Insulation Resistance-General Theory, Use, Limitations 3.1 Insulation resistance is the term gener- ally used to describe the quotient of the ap- plied direct potential divided by the current at some given time measured from the start of voltage application; thus reference will be found in this reco

30、mmended practice to 1 min or 10 min insulation resistance. 3.1.1 The current that results from the ap- plied direct potential consists of two parts: that in leakage paths over the surface of the insulation and that within the volume of the insulation. The current within the volume of the insulation

31、may be further subdivided as follows (see IEEE Std 62-1958, Guide for Mak- ing Dielectric Measurements in the Field). (1) The capacitance charging current, of comparatively high magnitude and short du- ration, usually has effectively disappeared by the time the first data are taken, and it does not

32、affect the measurements. (2) The absorption current decays at a de- creasing rate from a comparatively high ini- tial value to nearly zero. The resistance- time relationship is a power function which may be 7 IEEE 43- 1974 RECOMMENDED PRACTICE FOR TESTING plotted on log-log graph paper as a straight

33、 line. Usually the resistance measured in the first few minutes of a test is largely deter- mined by the absorption current. (3) The conduction current, which, with the surface leakage current, is nearly con- stant. These currents predominate after the absorption current has become insignificant. 3.

34、1.2 After removal of the impressed direct potential and the provision of a suitable dis- charge circuit, there will be evident a dis- charge which is of two parts: (1) The capacitance discharge current which will decay nearly instantaneously, de- pending upon the discharge resistance (2) The absorpt

35、ion discharge current which will decay from a high initial value to nearly zero, as does the absorption current in Section 3.1.1. 3.2 The insulation resistance of a rotating- machine winding is a function of the type and assembly of insulating material. In general, it varies directly with the thickn

36、ess of the insu- lation and inversely with conductor surface area. To obtain meaningful insulation resist- ance measurements on water-cooled ma- chines, water should be removed and the in- ternal circuit thoroughly dried. 3.3 Insulation resistance measurements are affected by several factors discuss

37、ed in Section 4: (1) Surface condition (2) Moisture (3) Temperature (4) Magnitude of test direct potential (5) Duration of application of test direct po- (6) Residual charge in the winding tential 3.4 Readings of insulation resistance are usu- ally taken after test dire& potential appli- cation of 1

38、 min and, if facilities are available, after 10 min to provide data for obtaining the polarization index. 3.5 The polarization index (ratio of 10 min to 1 min insulation resistance) is described in Section 4.5.2. 3.6 The interpretation of insulation resist- ance measurements of machine windings and

39、the calculated polarization index is described in Section 8. 4. Factors Affecting Insula tion Resistance 4.1 Effect of Surface Condition 4.1.1 Foreign matter, such as carbon dust deposited on creepage surfaces, may lower the insulation resistance. This factor is particu- larly important in the case

40、of direct-current machines which have relatively large exposed creepage surfaces. 4.1.2 Dust on insulation surfaces which is ordinarily nonconducting when dry may, when exposed to moisture, become partially conducting and lower the insulation resist- ance. 4.1.3 If the insulation resistance is reduc

41、ed because of contamination or excessive surface moisture, it can usually be brought up to its proper value by cleaning and by drying to re- move the moisture (see Appendix). 4.2 Effect of Moisture 4.2.1 Regardless of the cleanliness of the winding surface, if the winding temperature is at or below

42、the dew point of the ambient air, a moisture film will form on the insulation sur- face and may lower the insulation resistance. The effect is more pronounced if the surface is contaminated. It is important to make resist- ance measurements when the winding tem- perature is above the dew point. 4.2.

43、2 Many types of winding insulation are hygroscopic, and moisture may be drawn into the body of the insulation from the humid am- bient air. Absorbed moisture will have a large effect on the insulation resistance. Machines in service are usually at a temperature high enough to keep the insulation com

44、paratively dry. Machines out of service may be heated to keep the winding temperature above the dew point. 4.2.3 When tests are to be made on a ma- chine that has been in service, the tests should be made before the machine winding temper- ature drops to room temperature. The oppor- tunity may be ta

45、ken to test at several temper- atures to establish the applicable temperature coefficient (see Section 4.3.4). 4.3 Effect of Temperature 4.3.1 Insulation resistance of most materi- als varies inversely with temperature. 4.3.2 To minimize the effect of temperature when comparing insulation resistance

46、 tests or INSULATION RESISTANCE OF ROTATING MACHINERY IEEE 43- 1974 when applying the recommended minimum value of insulation resistance as given by Eq 2, it is important that the test be corrected to a 40C base. The correction may be made by use of Eq 1: where Rc = Rt = Kt = insulation resistance (

47、in megohms) corrected to 40C measured insulation resistance (in megohms) at temperature t insulation resistance temperature coefficient at temperature t 4.3.3 The correction of insulation resist- ance to 40C may be done by making mea- surements at several temperatures, all above the dew point, and plotting the results. When a logarithmic scale is used for insulation re- sistance and a linear scale for temperature, test points should approximate a straight line which will indicate the 40C value. For any temperature, Kt can be determined from such a plot b