Abstract
According to the recent analysis results of temporary AC overvoltage in the AC system connected with a frequency converter station, large magnitude of overvoltages were confirmed to occur under some special system conditions.
Most of the station insulators currently used cannot withstand such overvoltages according to our evaluation based on the data obtained before.
We recognized the necessity of tests to be done in order to evaluate such performance more accurately. We made both power frequency and switching impulse overvoltage flashover tests on contaminated insulators by the method well simulating the natural wetting condition.
Switching impulse flashover voltage with the wave shape having a long wave-front time of 2ms can be well correlated with the flashover voltage characteristics of temporary AC overvoltage. Higher flashover voltage characteristics were obtained by clean fog test method compared with those obtained by equivalent fog test method.
