INSULATION MICROBREAK DETECTION BY ACOUSTIC-EMISSION MEASUREMENTS

This article discusses a way to detect insulation microbreaks in a high voltage transformer whose windings are covered with epoxy resin. A microfault is registered as a series of short ultrasonic impulses having a high damping constant. By measuring acoustic emission one can determine the high voltage at which the microbreaks occur as well as the voltage at which they transform into a breakthrough, which becomes obvious through the rapid increase in the number of microbreaks per unit of time. Examination can be performed for the purpose of checking transformer serviceability with regard to breakthrough as well as for the purpose of determining the operating voltage at which the insulation is break-safe.