Foreword?[This introduction is not part of IEEE Std 95-2002@ IEEE Recommended Practice for Insulation Testing of AC Electric Machinery (2300 V and Above) With High Direct Voltage.]Traditionally@ the insulation of rotating machines has been tested for dielectric strength with alternating voltage. In 1952@ attention was directed to testing with direct voltage. Since then@ high direct voltage has been widely used. Many reports of procedure and results are found in the IEEE Transactions with expressions of widely differing opinion.In 1957@ the Insulation Subcommittee of the IEEE Rotating Machinery Committee appointed a working group to review the existing literature and to prepare a guide for the conduct and interpretation of high direct-voltage insulation tests. It was found that many methods of making the tests have been used and that there was no uniform opinion of their relative merits.In 1971@ the Insulation Subcommittee of the IEEE Rotating Machinery Committee appointed a working group to revise the existing guide to a recommended practice.In 1996@ the Materials Subcommittee of the IEEE Electric Machinery Committee appointed a working group to revise the existing recommended practice. The document has been updated in a number of respects and typical test results using the ramped voltage test method have been included.At present there is wide usage of high direct voltage for insulation testing@ but there are still areas of disagreement regarding the utility of such tests. In this recommended practice every effort has been made to state facts and to indicate what is not certain. This document gives the present opinion and evaluation of high direct-voltage insulation testing of a large number of investigators with experience in a wide area of test activities.Many of those who have used the methods described in this recommended practice have found them to be satisfactory and a valuable addition to other test procedures. It is hoped that the use of this recommended practice will achieve more uniform results and a fuller understanding and appreciation for the benefits of the high direct-voltage dielectric test.A general discussion of test procedures@ a comparison between alternating and direct-voltage testing@ and requirements for high voltage power supplies may be found in Annex A of this recommended practice. For background information on overvoltage testing@ see Clause 8 of IEEE Std 56-1977 and see IEEE P62.2/ D23.aParticipantsThis document was originally developed by a working group of the Insulation Subcommittee of the IEEE Rotating Machinery Committee. The members of this working group were:C. D. Sidway@ ChairB. R. Loxley@ Secretarya Information on references can be found in Clause 2.C. E. AsburyJ. S. AskeyB. M. CainA. W. W. CameronE. B. CurdtsJ. L. KuehlthauH. M. MarsdenG. L. MosesE. R. ScattergoodW. SchneiderH. R. TomlinsonH. P. WalkerW. A. WeddendorfE. S. YatesThe 1977 revision was prepared by a working group of the Insulation Subcommittee. The members were:R. F. Sharrow@ ChairThis revision was prepared by a working group of the Materials Subcommittee of the Electric Machinery Committee. The members were:N. E. Nilsson@ ChairThe following members of the balloting committee voted on this standard. Balloters may have voted for approval@ disapproval@ or abstention.When the IEEE-SA Standards Board approved this standard on 20 March 2002@ it had the following membership:James T. Carlo@ ChairJames H. Gurney@ Vice ChairJudith Gorman@ Secretary*Member EmeritusJ. M. BrownA. W. W. CameronE. B. CurdtsR. J. HillenW. J. SheetsG. WolffR. BartnikasK. BeckerJ. GrantV. GreenB. K. GuptaM. JacobsW. McDermidB. NindraL. RodlandL. RuxV. WarrenC. A. WilsonPaul A. AndersonWilliam E. AndersonRoy L. BalkeWilliam H. BartleyR. BartnikasK. BeckerThomas H. BishopE. A. BoulterSteven R. BrockschinkStephen P. ConradRoger H. DaughertyGuru Dutt DhingraJames H. DymondJames S. EdmondsFranklin T. EmeryJorge Fernandez-DaherNirmal K. GhaiJ. GrantJohn Travis GriffithFranklin H. GroomsThomas J. HammonsAdrienne M. HendricksonGary A. HeustonPeter H. LandrieuAntonio J. Marques-CardosoWalter J. MartinyC. V. MaughanW. McDermid JeffreyL. McElray Sr..Donald G. McLarenJames R. MichalecGary L. MichelRihong MoDaleep C. MohlaGlenn MottersheadArthur S. NeubauerN. E. NilssonJames A. OliverMadan RanaR. V. RebbapragadaJesus MartinezRodriguezCharles M. RoweJames A. RuggieriL. RuxMaurice A. SecrestJohn SheaDaniel SlomovitzGreg C. StoneQi SuJames E. TimperleyPaul Dieter WagnerV. WarrenKarim YounsiH. ZhuSid BennettH. Stephen BergerClyde R. CampRichard DeBlasioHarold E. EpsteinJulian Forster*Howard M. FrazierToshio FukudaArnold M. GreenspanRaymond HapemanDonald M. HeirmanRichard H. HulettLowell G. JohnsonJoseph L. Koepfinger*Peter H. LipsNader MehravariDaleep C. MohlaWilliam J. MoylanMalcolm V. ThadenGeoffrey O. ThompsonHoward L. WolfmanDon WrightAlso included is the following nonvoting IEEE-SA Standards Board liaison:Alan Cookson@ NIST RepresentativeSatish K. Aggarwal@ NRC RepresentativeAndrew D. IckowiczIEEE Standards Project EditorScopeThis recommended practice provides uniform methods for testing insulation with high direct voltage. It applies to stator (armature) windings of ac electric machines rated 2300 V or higher. It covers acceptance testing of new equipment in the factory or in the field after installation@ and routine maintenance testing of machines that have been in service.