Influence of Load Impedance on PD Monitoring Sensitivity for High-Voltage Cable Lines

Abstract

The aim of this paper is to discuss the influence of the load impedance on the sensitivity of partial discharge (PD) measurements. The investigated circuit is based on coupling capacitors to provide a current path for PD signals during resonance testing of cables. The choice of an appropriate value for this capacitance is crucial. However, the overall impedance at the point of measurement is also determined by the inductance of the test circuit. The presented PD measurement method is a nonconventional system using high-frequency current transformers (HFCTs) to measure and localize PD sources along the cable system. The sensitivity of the whole measurement is, among others, strongly dependent on the impedance at the point of measurement. The results of simulations and effective measurements are analyzed and compared. The impact of the different parameters like parasitic capacitances and inductances in the measurement circuit on the accuracy as well as the sensitivity will be discussed in detail.