Study of the AC surface discharge characteristics of insulation samples using the UHF method

Summary

Surface discharges occurring on high voltage insulators and bushings can lead to disruption of equipment and ultimately disconnection of power supply. With the increasing use of polymeric material for outdoor insulation, degradation of the insulation surface over time due to pollution and environmental effects such as temperature and humidity can evolve into severe damage to the insulation. Therefore, early detection of surface discharge can help prevent such damage from developing into a disruptive fault. In order to be able to detect surface discharges on operating equipment and to understand their properties, effective techniques should be used. The use of ultra-high-frequency (UHF) and acoustic techniques have been proposed for the study of partial discharge generated in transformers, GIS equipment and outdoor insulation. This paper reports the results of experimental measurements of surface discharges on acrylic insulation surfaces using UHF antennas, and analyses the characteristics of the emitted UHF signals using advanced digital processing. The results are correlated with those obtained with a monopole antenna, a horn antenna, and a high-frequency current transformer (HFCT) measurements to help elucidate the discharge properties. The measurements are carried out under clean surface conditions. Analysis of the initial results indicate that the amplitude frequency spectrum of the electromagnetic waves emitted by the surface discharge under clean conditions lies between 0.5GHz and 1.5 GHz, with a prominent peak at 1.1 GHz. It is expected that this study will help in defining the bandwidth and sensitivity requirements of UHF sensors used for detection of surface discharge in power system equipment, transmission lines and cables.

Additional informations

Authors

N. HARID, H. GRIFFITHS, B.BARKAT, N. AL SAYARI

Keywords

Partial discharge, UHF method, surface discharge, electromagnetic waves, HFCT sensor