Partial discharge and noise separation in combined cable–OHLs based on three‐phase power ratios

Abstract

Partial discharge (PD) detection has been proved as an effective tool for monitoring the insulation condition of high-voltage cables. However, the detection can be seriously affected by pulse-shaped interference from overhead lines (OHLs) when carried out at the cable termination of a combined cable–OHL. In this study, a novel scheme is presented for separating the PD pulses and interference in a combined cable–OHL. First, the characteristics of the currents from different pulse sources are investigated mathematically. On the basis of these characteristics, separation of multiple pulse sources can be realised by projecting the three-phase power ratios extracted from detected signals onto a ternary plot and then constructing maps using the power ratios of the defective phase. The performance of the scheme is subsequently evaluated by both numerical simulations and field applications. Furthermore, a comparison with the well-known time–frequency mapping method is provided. The results demonstrate that by using the proposed scheme, different pulse sources can be effectively identified without requiring stable pulse shapes and a better separation could be achieved compared with the conventional waveform-based approaches.