The effect of the thermal history on the space charge accumulation in HVDC crosslinked polyethylene cables

Space charge profiles of polymeric high voltage direct current (HVDC) cables measured by pulsed electro-acoustic (PEA) systems are normally asymmetrical. It is observed that the space charges in cable samples are mainly located in the outer part of the insulation with little or no space charge accumulation at the inner semi-conductive layer. The objective of the present work is to elucidate the underlying mechanisms behind this space charge accumulation process. The performed experiments include space charge measurements using a pulsed electro-acoustic (PEA) system on cables and plaques cross-linked and cooled under different conditions. The results suggest a link between space charge build-up and the microstructure of the insulation.