Partial discharge diagnosis by simultaneous observation of discharge pulses and vibration signal

Abstract

Protrusion defects on inner conductor can seriously weaken the dielectric strength of gas insulated switchgear (GIS). In practice, pulse current method (IEC 60270) and vibration method sometimes are ineffective for this type of defect. Clarification of coincidence of partial discharge (PD) characteristics measured with both methods is very important for further application of the vibration method. In this paper, PD pulses and vibration signal recorded on enclosure generated from artificial protrusions mounted on inner conductor with different lengths and diameters were measured synchronously by using a 252 kV GIS PD test system. The test GIS was filled with the gas SF6 of the standard atmosphere pressure (i.e. 101 kPa), and the power frequency of the test voltage was 50 Hz. The pulse repetition frequency (PRF) characteristics and frequency-resolved vibration (FRV) characteristics under different discharge level were investigated. The dynamic response (DR) characteristics of the experimental GIS are also obtained by using the force hammer test. For a good understanding of PD vibration characteristics, the relationship between FRV, PRF and DR was analyzed in detail. To make more reliable operations of GIS, an improvement vibration method for protrusion defect detection was developed and applied.