Vicki Warren — Iris Power - Toronto, Ontario
Brian F. Moore – Georgia Power - Atlanta, Georgia
Jim Williams – Bradley’s Motors - Corpus Christi, Texas
Special thanks to Gary Castle at Bradley’s Motors
Traditional tests of insulation resistance, polarization index (IEEE 43) and the controlled DC high voltage test (IEEE 95) have been effective in evaluating certain aspects of global vacuum pressure impregnation (GVPI) stator windings; however, they have not proven adequate for determining whether or not the insulation system is well-consolidated. Recently there has been the development of an IEC standard (IEC 60034-27) that defines the test procedures for performing off-line partial discharge testing as part of quality assurance testing. In addition, globally there has been a move towards using a dielectrics characteristic test, either power factor or dissipation factor, as part of the QA testing for GVPI systems. Partial discharge tests have proven to be effective in locating isolated problems that could lead to failure; whereas, the dielectrics characteristic tests provide a more general condition assessment. Based on experience to date, both are needed to fully evaluate how well the winding is consolidated.
This paper, presented at the 2014 EASA Convention, describes research done by EASA service shops on the effectiveness and practicality of using offline partial discharge combined with a dielectrics characteristic test to evaluate the consolidation of stator windings in medium voltage machines manufactured by GVPI. Advantages and disadvantages of each test and industrial standards will be described as appropriate.
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