Case Studies of Rotating Machine Insulation Condition Assessment

The progressive deterioration of high voltage machine insulation is assessed through nondestructive techniques like measurement of Insulation Resistance, Polarization index, tan δ & Capacitance and Partial discharge activity mainly for trend analysis. Though a single test cannot indicate the condition of the stator winding insulation, a reasonable assessment can be made by analyzing all the test results together. This paper presents the usefulness of these techniques in condition assessment of winding insulation of generators and motors in service. Several motors and generators were tested at some of the industries, hydro, thermal and nuclear power stations. The results are presented and discussed as case studies.