Partial discharge charge decay analysis using chopped sequence

Summary

Partial discharge measurements remain one of the main test and diagnostic tools in high voltage electrical insulation validation. Apart from instrumentation development, the key aspect is still in better understanding of physical phenomena, inception and development of discharges and associated mechanisms. Among those topics is the behaviour of charges remaining in the dielectric voids or on a surfaces from previous ignitions. This paper deals with analysis of a charge decay which depends on the dielectric mechanisms and surface electrical conditions. The special interest is paid to surface charge decay and relation to void conductivity. In order to reveal a charge decay dynamics the chopped sequence was applied. Partial discharge chopped sequence consists of a number of packets of a base waveform, separated by a variable time delay. The base waveform may be sinusoidal, square-like, trapezoidal or with the different shapes. The experiments were performed on two classes of insulating materials, manifesting broad spectrum of surface and bulk resistivity. Depending on the resistivity and neutralization effects, the deposited charges from post discharges will decay with certain time constant. Analysis of different chopped sequences might provide inside and assessment of the decay process. Thus proposed approach has further potential towards diagnostic methodology.

Additional informations

Keywords

Partial discharges, diagnostics, charge decay