The Effects of Semicon on Space Charge Behaviour in XLPE Model Cables

Abstract

Space charge suppression is one of the major requirement for HVDC power cables. Many efforts have been done for developing improved insulation materials. However, as an important part of the cable insulation system, the semicon material can also greatly influence the space charge characteristics of the HVDC cables. In this paper, an attempt is made to explore the space charge characteristics using different semicon materials to highlight the variation in space charge formation and distribution in a model cable using pulsed electro acoustic (PEA) technique. A model cable with different semicon materials for inner and outer semicon screens were manufactured. The experimental results revealed that the semiconductive materials has a greater influence on the space charge formation. It was found that only hetero charges accumulate near the outer semicon screen which is made of AC semicon material, while the space charge accumulation is suppressed near the inner semicon screen which is made of DC semicon material. The results are also consistent with the sandwiched plaque XLPE samples thermally bonded with different semicon materials. The findings of this work suggest that the good co-work between the insulation and semicon material can suppress the space charge accumulation that benefit the whole HVDC cable insulation system.