Partial discharge detection for GIS: A comparison between UHF and acoustic methods

Abstract

The widespread application of SF6 gas insulated substations (GIS) in high voltage power transmission requires reliable fault detection and diagnosis techniques. Partial discharge (PD) detection has so far been proven to be the most effective tool for GIS insulation diagnosis. Both ultra high frequency (UHF) technique and acoustic means have been popularly used in PD detection thanks to their well-noted anti-interference performance. In spite of numerous researches on either UHF or acoustic techniques, little has been done to draw a comparison between the two. To address this research gap, the present research simulates five major types of PD discharges caused by the immobilized particles on insulator surface, free metallic particles on insulator surface, protrusion on inner shell, high-voltage electrode faults and floating conductor discharge on a well-established 220kV test assembly, where PD signals were simultaneously detected by both UHF and acoustic methods. The two detection means are compared among the five PD models and different applied voltages in terms of inception voltage for discharge, average apparent discharge magnitude, discharge pulse count and average discharge amplitude. Based on the test results, it is suggested that the UHF method can be used as the major measurement for the diagnosis of insulation degradation in GIS with other necessary means serving as supplementation.