INFERENCE OF PD IN ELECTRICAL INSULATION BY CHARGE-HEIGHT PROBABILITY-DISTRIBUTION - DIAGNOSIS OF INSULATION SYSTEM DEGRADATION

This paper deals with application of stochastic procedures for the ana lysis of PDHD (partial discharge height distributions) detected during life of insulation systems. Experiments of accelerated aging under el ectrical stress were carried out on both an artificial flat cavity and a 23 kV epoxy-resin insulator, where PD are already active at the beg inning of aging. A correlation between aging time and PDHD features is observed during long-term voltage application, until breakdown, on bo th objects. In particular, the PDHD analysis is approached by means of the Weibull function. It is shown that the time evolution of shape an d scale parameters can provide diagnostic indications on aging amount, incoming failure and thus on the reliability of insulation systems.