Direct current electrical characteristics of nano-CB/LDPE composite

Electric field distortion caused by the space charge accumulation in the insulation is considered to be one of the obstacles for the operation of high voltage DC cables. In this paper, nano-CB/LDPE composites were fabricated by using the melt blending method. Space charge characteristics and field distortions of nanocomposite films were measured under direct current (DC) field by pulsed electro-acoustic (PEA) method. Dielectric properties and DC breakdown strength were also investigated. Experimental results indicate that, by adding appropriate doping content of CB nanoparticles, the space charge injection threshold of the films was increased, which suppressed homo-polarity space charge injection and ameliorated the field distribution. Breakdown strength of nanocomposite decreased whereas the dielectric permittivity and dielectric loss tangent increased slightly. However, too much CB nanoparticles mixed in LDPE could weaken the suppression effect on charge injection and field distortion, and the LDPE with 0.03wt% of CB nano-particle showed a relative better ability of inhibiting field distortion.