Effect of Semiconductive Layer on Space Charge Accumulation of Polypropylene Blends for DC Cable Insulation

This paper reports on the effect of different semi-conductive shielding layers on the space charge accumulation behavior of insulation layer in polypropylene (PP) HVDC cable. Four kinds of semi-conductive shielding materials were prepared with different content of CB (20, 25, 30, 35 wt%) in ethylene butyl acrylate copolymer (EBA) resin matrix. PP/propylene-based-elastomer (PP/PBE) blends were selected as the insulation layer. The space charge accumulation behavior of polypropylene blends was measured by pulsed electro-acoustic (PEA) method under an electric field of 50 kV/mm. The average charge density and electric field distribution in PP/PBE blends were estimated. The results showed that the average charge density of PP/PBE blends decreased first and then increased with the increase of the content of CB, and reached the minimum value when CB content was 25 wt%. At the same time, the electric field distortion also reached the minimum. Therefore, this semiconductive layer has the best inhibition effect of space charge in PP/PBE blends. This work has referencing significance for improving the insulation performance of PP based cable.