Measurement Limitations in Identifying Partial Discharges in Turn-Turn Insulation of Low-Voltage Induction Motors

This work aims to highlight limitations of measurement techniques when identifying partial discharges (PDs) in the turn-turn insulation of low-voltage induction motors. It has been observed in previous studies that different types of PDs exist. While the nomenclature of the authors varies, these types can be broadly classified into so-called “Townsend-like” and “streamer-like” PDs. The former are low amplitude slow rise time PD pulses and may thus be undetectable by common PD instruments. The present study extends previous investigations by identifying conditions which favor the formation of such Townsend-like PDs, illustrating the challenges associated with detecting such PDs, and showing that a prolonged exposure of an organic insulation material's surface to such PDs causes surface erosion. This emphasizes the potential importance of being able to detect this PD type between the thin turn-turn insulation of low-voltage induction motors.