Correlation between Space Charge Behavior and Dielectric Breakdown in Cross-linked Polyethylene under dc High Electric Field

Space Charge was measured in Cross-linked Polyethylene using pulse-electroacoustic method under a high dc electric field up to the time of dielectric breakdown. Local electric field in the bulk was calculated by integrating space charge profile. Dielectric breakdown did not occurred when the local electric field reached the maximum value but a little while after, suggesting that dielectric breakdown strength deteriorated after the local electric field reached the maximum value. The deterioration of the breakdown strength was caused by increase of mobile carriers that were generated in the insulation and were injected from cathode, where the local electric field was enough high.