AGING DIAGNOSIS OF INSULATION SYSTEMS BY PD MEASUREMENTS - EXTRACTIONOF PARTIAL DISCHARGE FEATURES IN ELECTRICAL TREEING

The charge height values associated with PD measured during electrical tree inception and growth are processed according to the Weibull dist ribution. Test arrangements, based on the needle-plane electrode syste m, consider specimens having either a cavity at the tip or an intimate contact with insulation. It is shown that the Weibull-function parame ters have close relation to discharges occurring in cavity and tree ch annels, and that an indication of inception of electrical trees can be obtained.