1、 IEEE Recommended Practice for Quality Control Testing of External Discharges on Stator Coils, Bars, and Windings Sponsored by the Electric Machinery Committee IEEE 3 Park Avenue New York, NY 10016-5997 USA 30 November 2012 IEEE Power and Energy Society IEEE Std 1799-2012IEEE Std 1799-2012 IEEE Reco
2、mmended Practice for Quality Control Testing of External Discharges on Stator Coils, Bars, and Windings Sponsor Electric Machinery Committee of the IEEE Power and Energy Society Approved 19 October 2012 IEEE-SA Standards Board Abstract: The procedure for quality control testing of external discharge
3、s on stator coils, bars and windings of large air-cooled ac electric machines is described in this recommended practice. Keywords: ac, corona-imaging instrument, discharge inception voltage, electrical insulation, external discharges, IEEE 1799, stator winding, ultraviolet radiation The Institute of
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18、ght 2012 IEEE. All rights reserved. viParticipants At the time this IEEE recommended practice was completed, the P1799 Working Group had the following membership: Remi Tremblay, Chair Claude Hudon, Secretary David Agnew Kevin Alewine Raymond Bartnikas Kevin Backer Stefano Bomben Andy Brown Donald Ca
19、mpbell William Chen Doug Conley Ian Culbert Jeffrey Fenwick Shawn Filliben Nancy Frost Paul Gaberson Michel Gagn Bal Gupta Gary Heuston Richard Huber Marcelo Jacob Aleksandra Jeremic Aleksandr Khazanoy Amir Khosravi Thomas Klamt Inna Kremza Laurent Lamarre Gerhard Lemesch Rimma Malamud William McDer
20、mid David McKinnon Charles Millet Glenn Mottershead Beant Nindra Sophie Noel Ramtin Omranipour Howard Penrose Helene Provencher Emad Sharifi John Schmidt Jeffrey Sheaffer Reza Soltani Gregory Stone Chuck Wilson Hugh Zhu The following members of the individual balloting committee voted on this recomm
21、ended practice. Balloters may have voted for approval, disapproval, or abstention. Michael Adams David Agnew Martin Baur Thomas Bishop Stefano Bomben Steven Brockschink Chris Brooks Donald Campbell Weijen Chen Ian Culbert Matthew Davis Ray Davis Gary Donner Gary Engmann Jeffrey Fenwick Jorge Fernand
22、ez Daher Sudath Fernando Rostyslaw Fostiak Paul Gaberson Michel Gagn Randall Groves Bal Gupta Werner Hoelzl Claude Hudon Innocent Kamwa Jim Kulchisky Chung-Yiu Lam Benjamin Lanz William Lockley Greg Luri Rimma Malamud William McBride William McCown William McDermid David McKinnon Don McLaren James M
23、ichalec G. Harold Miller Charles Millet Jerry Murphy Arthur Neubauer Michael S. Newman William Newman Sophie Noel Lorraine Padden Christopher Petrola Alvaro Portillo Iulian Profir Bartien Sayogo John Schmidt Jeffrey Sheaffer Gil Shultz Reza Soltani Gary Stoedter Gregory Stone James Timperley Remi Tr
24、emblay John Vergis Kenneth White Hugh Zhu Copyright 2012 IEEE. All rights reserved. viiWhen the IEEE-SA Standards Board approved this recommended practice on 19 October 2012, it had the following membership: Richard H. Hulett, Chair John Kulick, Vice Chair Robert M. Grow, Past Chair Konstantinos Kar
25、achalios, Secretary Satish Aggarwal Masayuki Ariyoshi Peter Balma William Bartley Ted Burse Clint Chaplin Wael Diab Jean-Philippe Faure Alexander Gelman Paul Houz Jim Hughes Young Kyun Kim Joseph L. Koepfinger* John Kulick David J. Law Thomas Lee Hung Ling Oleg Logvinov Ted Olsen Gary Robinson Jon W
26、alter Rosdahl Mike Seavey Yatin Trivedi Phil Winston Yu Yuan *Member Emeritus Also included are the following nonvoting IEEE-SA Standards Board liaisons: Richard DeBlasio, DOE Representative Michael Janezic, NIST Representative Julie Alessi IEEE Standards Program Manager, Document Development Malia
27、Zaman IEEE Standards Program Manager, Technical Program Development Copyright 2012 IEEE. All rights reserved. viiiIntroduction This introduction is not part of IEEE Std 1799-2012, IEEE Recommended Practice for Quality Control Testing of External Discharges on Stator Coils, Bars, and Windings. Extern
28、al discharges in the end-windings are caused by inadequate workmanship for globally vacuum-pressure impregnated (VPI) stators or problems on stators assembled on-site. Poorly finished lashes with an insufficient gap between bars produces coil-to-coil or bar-to-bar discharges. Misalignment between ad
29、jacent coils or bars may also reduce the gap distance and generate a high electric stress larger than the air breakdown strength. Sometimes misplaced resistance temperature detector (RTD) or air gap monitor leads have been seen to cause partial discharges (PDs) with high-voltage bars or coils. Exter
30、nal discharges for the individual coil/bar could also be a result of improper design, improper material, or improper workmanship. After many years, the deterioration induces surface degradation that may lead, in the long run, to a phase-to-ground fault and reduce the overall reliability of the syste
31、m. More detail on the theory of external discharges and their effects is given in Annex A. Some utilities have seen deterioration of the junction between the stress control coating and semiconducting slot coating of stator windings after only a few years of operation. Other secondary effects, such a
32、s the production of a large quantity of ozone, which may be deleterious to the equipment and dangerous to personnel, is also of concern. In addition, over the years, the ground-wall insulation thickness of stator coils and bars has been reduced to improve heat transfer through the ground-wall insula
33、tion. This optimization does, however, increase the dielectric stress on the insulation and on the end-winding stress grading system making them more susceptible to developing electrical discharges. In the current recommended practice, the term “semiconducting slot coating” is preferred to “semicond
34、uctive slot coating” often used in the industry. These coatings, composed of resin, varnish, enamels, or other compounds, are filled with carbon black powder, graphite, or other filler and should have electrical resistivity per unit of surface of 1 102 5 105Ohms per square. The semiconducting slot c
35、oating applied on the insulation surface of the slot parts of winding must have uniform tight contacts with the grounded walls of the stator slot. This coating provides minimum voltage between the surface of the coil or bar and the grounded stator core. A stress control coating must be applied on th
36、e end turns of high-voltage stator winding and overlap the semiconducting slot coating to provide electrical contact between them. The stress control coating has a non-linear resistance with voltage. This recommended practice presents two methods for evaluating the quality of materials and design, f
37、actory workmanship, and on-site workmanship. The first one, the blackout test, has been used for many years. The second one, the corona-imaging inspection, is more recent and presents several advantages. Each method has its advantages and disadvantages. IEEE Std 1434 mentions these two inspection me
38、thods but with very little detail. The current recommended practice includes a more elaborate description of sample preparation, bench tests, test conditions, and acceptance criteria in the factory and on-site. Copyright 2012 IEEE. All rights reserved. ixContents 1. Overview 1 1.1 Scope . 2 1.2 Purp
39、ose 2 2. Normative references 2 3. Definitions 3 4. Test preparation and safety. 5 5. Test equipment and connections. 5 5.1 Sensitivity of the corona-imaging instruments 6 6. Quality control test of external discharges with corona-imaging instrument or blackout test 7 6.1 Factory test on coils and b
40、ars. 8 6.2 Stator model test 10 6.3 Test on fully assembled stator windings 14 7. Data records 20 7.1 How to fill the data logging tables. 20 Annex A (informative) Theory of optical emissions from external discharges 24 Annex B (informative) Variability of discharge inception and extinction voltages
41、 . 27 Annex C (informative) Example of determination of the maximum voltage for a specific winding diagram. 28 Annex D (informative) Example of correction factor to apply to the test voltage of a stator model and VPI stator for a machine which will operate at altitudes of more than 1000 m. 31 Annex
42、E (informative) Example of operating-voltage table and bar/coil identification table used during test. 33 Annex F (informative) Bibliography 35 Copyright 2012 IEEE. All rights reserved. 1IEEE Recommended Practice for Quality Control Testing of External Discharges on Stator Coils, Bars, and Windings
43、IMPORTANT NOTICE: IEEE Standards documents are not intended to ensure safety, health, or environmental protection, or ensure against interference with or from other devices or networks. Implementers of IEEE Standards documents are responsible for determining and complying with all appropriate safety
44、, security, environmental, health, and interference protection practices and all applicable laws and regulations. This IEEE document is made available for use subject to important notices and legal disclaimers. These notices and disclaimers appear in all publications containing this document and may
45、 be found under the heading “Important Notice” or “Important Notices and Disclaimers Concerning IEEE Documents.” They can also be obtained on request from IEEE or viewed at http:/standards.ieee.org/IPR/disclaimers.html. 1. Overview This quality control test is used to confirm that the insulation sys
46、tem of the stator winding of generator and motor operating in air, including the semiconducting slot and stress control coatings, are free of external discharges. Quality control of the semiconducting slot coating, stress control coating, and manufacturing process is best done in the factory. For st
47、ators assembled on-site, such as those for large hydro-generators, additional tests can be performed on the fully assembled generator in order to control the quality of the assembly and workmanship. This control includes: a) evaluation of the spacing between end-arms and with the phase circuit rings
48、 or connections to the main phase terminals b) confirming proper alignment of the ground plane made by the semiconducting slot coating on the straight portion of the bar/coil with regard to the core pressure finger c) the positioning of all cables (RTD, air gap monitor) with respect to high voltage
49、and d) inspection of imperfections that may have been introduced during assembly (presence of foreign objects, misplaced slot center filler, chips and scratches to bars or coils coating) In the case of machines assembled in the factory, such as VPI machines, the complete quality control test can be done in the factory. However, special care should be taken so that no change in the machines IEEE Std 1799-2012 IEEE Recommended Practice for Quality Control Testing of External Discharges on Stator Coils, Bars, and Windings Copyright 2012 IEEE. All rights rese
