Electrical test methods for nonceramic insulators used for live line replacement

The utilities frequently use nonceramic insulators for live line maintenance. These insulators are not always tested electrically during manufacture. Undetected internal failures in an insulator may endanger workers performing live line maintenance on the insulators. The live line maintenance requires careful testing of each insulator before use. For the selection of the most effective test method, insulators were purposely made with internal flaws and then subjected to megger, hot stick, partial discharge and RIV tests as well as measurement of the total and surface component of leakage current, together with surface heating measurement. The most sensitive method is the RIV test, which identified 6 insulators with flaws. The partial discharge and hot stick tests found 4 insulators with embedded wire. From a practical point of view, the modified hot stick test seems to be suitable for field test of the insulators.