Pulse-sequence analysis: a new method for investigating the physics of PD-induced ageing

Abstract

A new method is presented of partial discharge data analysis for the investigation of space charge and degradation phenomena in high-voltage insulation systems. The basic principles of the pulse-sequence-analysis (PSA) are illustrated and the characteristic differences with regard to standard procedures that have been established during the past few years are outlined. A description is given of an electronic partial discharge acquisition system, which is designed on a plug-in interface board for a standard PC to perform long-term measurements of all the discharge parameters required for the succeeding analysis. Electrical treeing in polyethylene is used to demonstrate the usefulness of the method. It is shown that information on the physics of treeing phenomena especially with regard to the influence of local space charges and their build-up and decrease over time as well as the development of the local degradation can be obtained by considering correlations between consecutive discharge pulses. Some experimental results from different stages of the electrical tree growth are analysed and their meaning with regard to the local microscopic phenomena inside the tree or in the vicinity of the tree tips discussed. This paper is based on an oral presentation at a conference on Partial discharge, September 1993, Canterbury, titled 'Pulse-sequence analysis, a way to get a better insight into the physics of discharges'.