UHF diagnostics for gas insulated substations

The UHF technique of detecting partial discharges in gas insulated substations (GIS), has over the past 10 years or so been developed from a laboratory curiosity into a sensitive means of giving an early warning of most impending failures in the substation. Its rapid acceptance by both utilities and switchgear manufacturers worldwide has resulted from it being a simple, sensitive and practical technique. In addition, utilities are finding it necessary to drive their plant harder and need to be assured of its reliability-even though they may have fewer staff to carry out maintenance work. The author describes how the UHF technique is now seen by them as a cost effective means of avoiding failures, and providing the high quality of supply demanded by today's customers.