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

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 EB+ with the same polarity to that of the pre-stressing field was higher than the DC breakdown strength EB of thin LDPE films without pre-stressing, while the DC breakdown strength EB− with the opposite polarity was lower than EB. 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 EB+ and EB− were found higher than EB. 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.