Pre-stressing effect on DC breakdown in low-density polyethylene

Abstract

Polyethylene is widely used in electrical wires and power cables. The pre-stressing effect, which restricts the applications of polyethylene, has not yet been investigated in depth. We studied the breakdown of low-density polyethylene (LDPE) films pre-stressed by direct current (DC) electric field. The results showed some conformity, as reported in many other papers, that the DC breakdown strength E B+ with the same polarity to that of the pre-stressing field was higher than the DC breakdown strength E B of thin LDPE films without pre-stressing, while the DC breakdown strength E B − with the opposite polarity was lower than E B. Such phenomena could be explained by the hetero effects of accumulating space charges, which enhanced the electrical field when the polarity was reversed. However, as a further increase in pre-stressing electrical field, both E B+ and E B − were found higher than E B. We investigated the space charge behavior in LDPE films and found that when applied with a higher electrical field, space charge packet initialized and traveled through the specimen. The results suggest that the space charge packet behavior may contribute to the pre-stressing effects on electrical breakdown in LDPE films.