DC treeing breakdown phenomena of LDPE at cryogenic temperature

The growth of polarity reversal trees was initiated by application of the impulse voltage of inverse polarity after pre-stressing with a dc voltage was studied in a low density polyethylene (LDPE). The Weibull distributions of the length of polarity reversal tree were analyzed. The length of polarity reversal tree has no dc pre-stress effect and no temperature dependence below glass transition temperature of LDPE. Above glass transition temperature, however, the length of polarity reversal tree increases greatly with the increase of the specimen´s temperature. The shape parameter (β) obtained from the Weibull distribution of the tree length is always β>1. From these results, the effect of space charge on dc treeing phenomena at cryogenic temperature was discussed