Space charge and long-term performance of XLPE insulation under a high DC field

The correlation between space charge accumulation and insulation failure has been investigated in two types of XLPE subjected to a DC field of 50 kV/mm. The specimens were aged for extended periods of time, up to 256 weeks at single polarity and up to 72 weeks with the polarity reversed every week. While all specimens of regular XLPE, without tree-retardant additives, survived 256 weeks of single polarity aging, all specimens having the additive broke down within 54 weeks. However, the latter material survived 72 weeks without a single breakdown when the polarity of the applied voltage was reversed every week at RT and 75 °C.