Space charge measurements in polymeric HV insulation materials

This paper reports on a study using the laser induced pressure propagation (LIPP) method to measure the space charge characteristics in bulk crosslink ed polyethylene (XLPE) insulation under dc electric stress. Particular atte ntion has been given to the quantitative appraisal of calibration parameter s, and the resultant estimations of space charge and electric stress distri butions. A method is described for analyzing the measured raw data from ram p voltage and aging tests to give an estimate of charge and stress without resorting to a complicated mathematical exercise. The consequence of stress enhancement due to the trapped charge on the life of the insulation is est imated using the empirical inverse law. Using analysis of variance and a mu ltivariate analysis technique, the effects of treatment and type of XLPE on the space charge characteristics are also discussed.