Partial discharge measurement in operation: problems with disturbances and their removing

Abstract

Diagnostics by partial discharge measurement is a modern diagnostic method for determination of the state of insulating systems of high voltage machines and equipment. In the High Voltage Laboratory of the Czech Technical University in Prague was developed the complex measuring and evaluating system for partial discharge measurement. Unfortunately, the main problem of discharge activity measurement in practice is in electromagnetic disturbance. This article is focused on the removing this disturbance from measured data. Great problems in the evaluation of partial discharge data is in various sorts of interferences. The most of disturbing signals was eliminated by using of a suitable circuit modification, but others could be only convert (in the case of partial discharge signals into digital form) by using suitable computing programs for the processing and saving of measured data. In this article two basic algorithms are described for the elimination of main disturbing signals from digitized partial discharge data. At first, the algorithms for the elimination randomize disturbing signals and the second, for the SCR disturbing (from thyristors). Two math theorems were applied to all measured samples by the computing program. In another way for the elimination of disturbances from partial data is the mathematical Wavelet analysis, which makes possible the elimination of more types of disturbance.