What You Should Know Before Acquiring Partial Discharge on High-Voltage Motors and Generators: Case Studies and Remedial Actions

Partial Discharge (PD) monitoring is a useful diagnostic tool as it can expose problems that would be difficult to identify otherwise. However, evaluation of a single data point has always been difficult. A better option is to take periodic measurements, starting with a fingerprint or benchmark measurement on the new winding, to obtain trend data. During the last decade, the trend within electric utilities, plants, and petrochemical industries has been increasingly to specify the PD limit when developing their technical specifications for high-voltage (HV) motors and generators. In response to that requirement, motor and generator manufacturers may introduce cost by overdesign, but this does not necessarily produce a machine with a longer life or increased reliability. The biggest challenge often observed during site inspections and testing is to carefully interpret the PD data without causing unnecessary concern.