Assessment of insulation condition in rotating machine stators

The authors describe an attempt to assess the condition of stator insulation in standby generators in two generating stations. The insulation condition was estimated by comparing diagnostic test results for different machines with similar insulator or for different phases of the same machine. The diagnostic tests included measurements of insulation resistance, partial discharges, and capacitance and dissipation factors as well as AC and DC hipot tests. The methods used to assess the insulation system are outlined in detail, and the assessment results are described and discussed.< >