Correspondence Between Charge Accumulated in Voids by Partial Discharges and Mapping of Surface Charge With PEA Detection

Abstract

Partial discharge (PD) dynamics in gaseous inclusions are related to the memory effects that originate from surface charge accumulation. In this article, the correspondence between a deposited charge that is inside a void during the PD activity with the surface potential mapping and space charge quantity that are obtained through the pulsed electroacoustic (PEA) method was investigated. The experiments were performed in the configuration of an asymmetric void that is embedded in a polyethylene (PE) material. Since the air gap in a void blocks acoustic wave propagation, the measurements were focused on one dielectric void wall (opposite to the metallic electrode). It was discovered that the polarity of the last period in a PD sequence influences the polarity of a deposited charge. Two types of readout pulsers were investigated and compared with the PEA method. In the surface charge decay process, a faster rate for negative charges was noticed as compared with positive ones. The experimental results showed a good quantitative correspondence between a real charge that was deposited by a PD during the phase-controlled sequence with an accumulated charge value that was obtained from surface mapping as well as charge detection—both being performed by means of the PEA method on the same layer of a void wall. The presented experimental results and analysis help extend the insight into PD mechanisms and quantitative surface charge accumulations.