Pulse-count Distribution as a Possible Diagnostic Tool for Assessing the Level of Degradation of Rotating Machine Insulation

The work covered in this paper pertains to a method by which one can qualitatively assess the condition of epoxy mica insulation systems used in large rotating machines, as function of time. Experimental techniques for acquisition and analysis of failure data have beeh presented. Experiments have been conducted on actual rotating machine coils subjected to combined electrical and thermal stress, under simulated conditions, so as to reflect the service environment as far as possible. Diagnostic measurements such as incremental loss tangent, capacitance change, partial discharge pulse count/magnitude, and PD energy have been performed along with destructive measurements (dielectric strength). Excellent correlations between pulse count/magnitude and dielectric strength appear to be present. This fact can be used, in the assessment of the degree of degeneration of the insulation