Generator and motor stator monitoring based on partial discharge quadratic rate measurement

The authors describe the use of partial discharge quadratic rate measurements on high-voltage generator and motor windings, which allow global aspects to be monitored for all partial discharge generating phenomena in a stator and their evolution to be followed over time. Two measuring instruments are used: an oscilloscope to view the signal and a narrowband quadratic-rate instrument equipped with selective filters. The frequency bands and test circuits are selected to perform two different and complementary measurements, namely, measurements on the winding as a whole and localized measurements at the end of the winding. The method can be used to find manufacturing defects at acceptance and to monitor generator windings in service using periodical measurement as part of a suitable maintenance schedule