Effect of voltage reduction in minimising partial discharge activity in cables – experimental study

A common cause of insulation degradation in high voltage (HV) cables is due to partial discharges (PD). PD may be initiated through imperfections and contaminants present in the insulation. It can be hypothesized that a reduction in system voltage can potentially reduce PD, which will correspondingly extend the service life of the cable. Currently, industry voltage statutory requirements permit ±6% tolerance setting on nominal voltage on distribution networks. Such ±6% voltage reduction on may have little or adverse effect on PD magnitude which depends on the nature of defect. Hence, the accuracy and type of measuring PD while reducing system voltage is more critical for this application. Power cable as a low pass filter which attenuates and disperse the PD pulses. In this paper, effect of voltage reduction on PD is investigated using standard electrode geometries such as point-plane, point-point and point- rod using IEC60270 measurement system together with frequency domain measurements. It has been observed that PD frequency characteristics at different voltages varies in the wideband frequency spectrum.