Graphical Characteristics Analysis of PD Signals Phase Distributions of XLPE Cables

Abstract

Aiming at analysing the graphical characteristics of PD signals of XLPE cables, this introduced the methods of constructing four graphs of phase distribution: ϕ-Q-N distribution map, maximum discharge quantity phase distribution H_Qmax(ϕ), the mean of discharge quantit phase distribution HQmean(ϕ) and the discharge frequency phase distribution H_N(ϕ). An experimental platform in laboratory was established to acquiring PD signals of four typical insulation defects of XLPE cables. The results show that different insulation defects leads to the PD signals which have distinct graphical characteristics. Corona discharge and surface discharge are asymmetrical in phase distribution while suspended electrode discharge and internal air gap discharge are symmetrical. The amplitudes of corona discharge are concentrated while the amplitudes of surface discharge vary greatly. The amplitudes of internal air gap discharge in two half-cycle are almost the same level while the amplitudes of suspended electrode discharge in positive half-cycle exceed that in negative half-cycle. According to these characteristics, it can be inferred which type of discharge the PD signals belongs to.