Space Charge Formation and Breakdown in Polyethylene Influenced by the Interface with Semiconducting Electrodes

Abstract

This paper deals with the influence of interface between polyethylene and semiconducting electrode on the space charge formation and electrical breakdown. Low-density polyethylene (LDPE) films attached with different semiconducting electrodes were subjected to the DC breakdown test, and corresponding space charge distribution was measured.A heat treatment to LDPE itself did not bring about a significant change in space charge profile, however, when a semiconducting electrode was hot-pressed, the impurities would migrate into LDPE at high temperature, leading to the change in space charge profile. Furthermore, it was suggested from the comparison between the results with degassed and asreceived semiconducting electrodes, that some carriers relating to impurities in the electrode would move into LDPE under the voltage. In addition, It was shown that the breakdown is not determined by the field at the cathode which can supply sufficient electrons, but by the maximum field across the specimen, suggesting that an increase in conduction current due to the generation and/or injection, rather than the electronic avalanche process, leads to the breakdown.