Dielectric dissipation factor acceptance criteria for stator winding insulation
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Dielectric dissipation factor (DDF) testing is widely employed by manufacturers and end users of rotating machines to assess the quality (or uniformity) of the insulation of individual stator coils and bars. A new IEC standard (IEC 60034-27-3) has been developed to provide guidance not only on the test method but also on maximum permitted values of DDF. The relevant section of the standard also defines the test voltages at which DDF measurements are obtained. During the drafting of the standard, there was significant discussion concerning the appropriateness of the DDF levels that are contained in the document. The purpose of this contribution is to examine these levels in the context of DDF data obtained over a period of decades on large numbers of stator coils and bars employing a wide range of insulation systems. An analysis of the data is presented and compared with the IEC 60034-27-3 limits and the implications discussed.
[1] R. Omranipour,et al. Effect of stress grading systems and guarding techniques on measured power factor and power factor tip-up of electric machinery stator windings , 2009, 2009 IEEE Electrical Insulation Conference.