Partial Discharge Signal Propagation in Three-Phase Gas-Insulated Switchgear: CIGRE Recommendations-Based Analysis

Abstract

High voltage (HV) testing of Gas-insulated switchgears (GIS) has been predominantly employed using the ultra-high frequency (UHF) detection techniques. Initiated partial discharge (PD) currents are coupled with electromagnetic (EM) waves, which are then captured by the UHF antennas. To determine the minimum detectable signal received by a UHF sensor, CIGRE sensitivity verification recommendations are utilized. In this paper, a 3-phase GIS model, which utilizes CIGRE recommendations to analyze the EM waves behavior, is built based on 3-D full-Maxwell finite element (FE) solver. This approach permits initiating a PD source using a transmitting sensor, which can then be acquired using other receiving sensors. The modeling approach introduced in this paper can be used to understand the behavior of signals propagating inside GIS systems for better utilization of UHF sensors in detecting PD inside such capital assets. The proposed three-phase GIS model investigates the EM wave propagation in time-domain and frequency-domain using step 1 of the CIGRE sensitivity verification recommendations. The impact of the relative position of the PD source and sensors, and the dielectric spacers on EM wave propagation is investigated and analyzed. The obtained results show that three-phase GIS structures act as cavity resonators when PD is created. Moreover, both low-frequency and high-frequency modes of propagation exist in such cavities.