Screening Method and Accelerating Test of DC Partial Discharges in Molded Polyethylene Components

Abstract

A method for measuring simultaneously the dc partial discharge of many samples, a screening method by soft X-rays and a voltage and/or temperature accelerating test are proposed in order to save time for measuring the dc partial discharge. Theoretically, it is possible to distinguish a sample where the dc partial discharge has occurred from many other samples by using the band pass filters having different central frequencies at both sides of the samples and the detector parts.It is also clarified that soft X-rays are useful in detecting the cavities in polyethylene. From the voltage and temperature dependence of the repetition rate of the dc partial discharge, the following acceleration coefficient is obtained: α=(\\frac{V_{2}}{V_{1}})n\\frac{\\sum\\limits_{j{=1}}^{N_{2}}\\cfrac{1}{E_{ij}}}{\\sum\\limits_{j{=1}}^{N_{1}}\\cfrac{1}{E_{ij}}}exp {\\frac{W}{k}(\\frac{1}{T_{1}}-\\frac{1}{T_{2}})} where the voltage, the temperature and the number of discharge sites are changed from V1, T1 and N1 to V2, T2 and N2, respectively; Eij is the discharge inception stress of the jth discharge site; and W is the thermal activation energy of polyethylene.