Temperature effect of space charge distribution in cross-linked polyethylene

Electrical characteristics of cross-linked polyethylene (XLPE) often vary depending on temperature. The accumulation of space charge in the insulation of extruded HVDC cables is frequently discussed and considered in development of insulation systems designed for HVDC application. Thus it is important to study and attempt to understand the space charge behavior in XLPE under various temperatures. This paper presents the results of pulsed electro-acoustic (PEA) measurement of the space charge distribution in 0.3mm thick planar XLPE samples over the temperature range of 30~90°C. The results show that the testing temperature has a great effect on the space charge distribution in XLPE. At room temperature accumulation of homocharge is observed adjacent to both cathode and anode, while at temperatures above 50C the space charge distribution is dominated by negative charges. This might be contributed to the variation of charge injection and charge mobility at different temperatures. Besides, the charge decay rate during short circuit increases with the increased testing temperature.