Measuring system for phase-resolved partial discharge detection at low frequencies

This paper addresses the measurement of partial discharges (PD) for a range of low frequencies of applied voltage and explores the frequency dependence of PD patterns for a few objects. The aim is to determine the existence of frequency-dependent trends in PD patterns and how these trends can be expressed through use of statistical parameters calculated from the PD patterns. An experimental setup was developed to measure phase-resolved PD patterns for a range of low frequencies, from 1 mHz to 100 Hz. Tests were performed on a few PD-infested objects, including a corona gap, a needle-film object, and a generator stator bar, to demonstrate the measuring system and analysis methods. Statistical operators were used to quantify the PD patterns, and the resulting parameters were then considered as functions of frequency.