Effects of the preparation of semi-conducting electrode on space charge injection in LLDPE

Polyethylene is widely used in high-voltage DC cables, but prolonged exposure to high-voltage electric field will result in space charge accumulation in insulation layers, which could lead to electric field distortion or even breakdown of cables. The addition of carbon black (CB) in semi-conducting layer plays an important role in homogenizing electric field and preventing insulation damage. In this paper, CB nanoparticles of 18nm, 30nm and 55nm were uniformly dispersed into ethylene-vinyl acetate copolymer (EVA) with 30wt% and 35wt% respectively. The effects of the preparation of semi-conducting electrodes on space charge injection in LLDPE were studied under 40 kV/mm and 40°C. The obtained results show that space charge injecting rate is low when the mass percentage of CB in the semi-conducting electrode is low. The sample with the electrode filling with bigger size CB particles and filling rates also shows low space charge injecting rate. The impact of crosslink agent within the semi-conducting electrodes on the injection of space charge is also discussed.