Space Charge Distribution in an Extruded Cable Aged in Tap Water for 3 Years

Moisture is one of the parameters which might have an effect on the space-charge distribution in an extruded insulation system under DC voltage. Investigation into their relationship is of importance for gaining insight into the conduction and breakdown mechanisms of insulation materials. In this study, a specially manufactured lab sample in the form of an extruded cable has been aged in tap water for 3 years under DC voltage. Space charge measurements were made using the PEA (pulsed electro-acoustic) method. These measurements were performed before, during and after the wet ageing. Limited hetero-charge was observed in the vicinity of insulation screen / insulation interface. Both negative and positive DC voltages have been examined. The cable survived the 3-year-long wet ageing without breakdown.