Study on the Relation between Space Charge Accumulation at Cable Stress Cone and Semi-conducting Materials

To study the effect of semi-conducting(SC) material o n space charge accumulation in cable accessory, cable electrical-thermal accelerated aging with cable accessories was carried out in laboratory. The experiment results show that a large amount of space charge accumulated in the cable insulation area covered by the stress cone, while there was no space charge in other areas. To explain the reason, the comparative experiments of Cross-linked polyethylene(XLPE) slices of cable insulation were carried out using silicone rubber SC material and ethylene-vinyl acetate copolymer(EVA) SC material as upper electrode respectively. The results show that a small amount of heteropolar charge accumulated near the EVA SC upper electrode, while a large amount of heteropolar charge accumulated near the silicone rubber SC upper electrode. It is concluded that due to the low conductivity and high contact barrier between XLPE and silicone rubber SC material, the ability of conducting sparce charge is weak. Space charge cannot escape from the stress cone SC electrode and accumulate on the outside of the cable insulation at stress cone. The research work shows that the SC material of cable accessory plays a key role in the space charge accumulation. It is necessary to carry out the next work and study how to select materials to suppress the space charge accumulation at cable stress cone. The research work has important theoretical guiding significance for the improvement of manufacturing technology and voltage level of HVDC cable.