Modification of space charge pattern and charge mobility of Low Density Polyethylene (LDPE) in the presence of crosslinking byproducts

The formation of space charge in Crosslinked Polyethylene (XLPE) cable has always been related to the byproducts such as acetophenone, a-methylstyrene and cumyl alcohol. In this paper, the argument is to be justified. Space charge formation in cumyl alcohol soaked Low Density Polyethylene (LDPE) is presented and compared with that of acetophenone and a-methylstyrene soaked LDPE. Cumyl alcohol causes charge accumulation of both charge polarities with heterocharges appeared when the sample is stressed at low voltage. The total charge accumulated as well as the charge decay in the clean LDPE sample are then compared to that of the chemicals soaked LDPE films. Charge mobility values in all samples were calculated from the decay characteristics and the results reveal that the byproduct chemicals accelerate the decay process in LDPE film, due to their high charge mobility. Since the byproduct chemicals change the space charge decay behavior of LDPE, it is suggested that the chemicals modify the trapping characteristics of LDPE. This is possible either by superseding the deep traps in insulator with shallow traps from the chemicals, or simply adding up the number of shallow traps in the insulator.