Influence of Deep Trap Density and Injection Barrier Height towards Accumulation of Space Charge within Dielectrics

Over a decade, insulation technologies have undergone numerous developments to provide better protection for high-voltage direct current (HVDC) equipment. HVDC system has been regarded by the power industry as a medium for long-distance bulk transmission over high voltage alternating current (HVAC). Various types of materials have been used to insulate the HVDC equipment. However, the lack of knowledge about the nature of space charge accumulation which is one of the major problems with HVDC system performance has brought challenges to the industry. It is impractical for the industry to manufacture perfect insulation that could sustain any cause of breakdown due to poor chemical properties. The insulation age or impurities existing within the insulation morphology can influence the accumulation of space charge, thus leading to distortion of an electric field in the insulation material. The constant electric field distortion can accelerate the ageing process of the insulation material itself. To improve the insulation performance, it is important to study the influence of different deep trap densities and the injection barrier height parameters on the behaviour of space charge. This paper will focus on the investigation of space charge behaviour by using a bipolar charge transport (BCT) model on low-density polyethylene (LDPE) and cross-linked polyethylene (XLPE), which both are common polymeric insulations for HVDC cable. In this paper, the effect of different parameters of both deep trap density and injection barrier height on space charge behaviour will be studied based on the charge density and electric field. It has been observed that the deep trap density and injection barrier height affect the accumulation of space charge in the LDPE and XLPE.