Online Partial Discharge Detection Technique for GIS Based on UHF Sensors

Resumen

Gas-Insulated Switchgear (GIS) have been in operation for more than 45 years and show a high level of reliability. However, experience indicates that some of the in-service failures are related to defects in their insulation system. Many of these defects can be detected by Partial Discharge (PD) diagnostics. PDs generate electromagnetic and acoustic waves, emit light and produce chemical decomposition of insulation materials; these physical and chemical effects can be detected by various diagnostic methods and appropriate sensing elements (sensors). Besides the so-called ‘conventional’ electrical method described in IEC 60270, it is possible to detect and measure PDs with various ‘non-conventional’ methods. The Ultra-High Frequency (UHF) measurement method, which was introduced in the late 1980’s for PD detection, is used worldwide by GIS manufacturers during routine testing in factory, during commissioning on-site and by utilities for continuous monitoring in service. The UHF method is less sensitive to noise, so it is easier to handle in comparison with the conventional method according to IEC 60270. To avoid technical misinterpretation, there was a special need to give recommendations for this non-conventional method. This paper is based on the experience and describes its practical applications for GIS. A detailed description of the procedure is given and supported by examples. Guidelines will help the users with the effective application of the UHF method for Online PD detection on GIS.