Effect of graphene modified semi‐conductive shielding layer on space charge accumulation in insulation layer for high‐voltage direct current cable

Abstract

Space charge accumulation in the insulation layer of high-voltage direct current (HVDC) cable is one of the key factors restricting the development of HVDC cable. The inner semi-conductive layer as an important structure of cable will affect the charge accumulation characteristics in the insulation layer. This work intends to explore the method of modifying the semi-conductive layer with graphene, to suppress charge accumulation in the insulation layer. First, the semi-conductive layer with different contents of Graphene (G) and carbon black (CB) are prepared. Second, the morphology and surface roughness of the cross section are analysed. Further, the effects of the semi-conductive layer on space charge accumulation of the insulation layer are studied by pulsed electro-acoustic method and thermal stimulation depolarisation current method. The experimental results show that a moderate amount of graphene replacing CB can effectively reduce charge accumulation in the insulation layer and inhibit positive temperature coefficient (PTC) effect at the same time. The surface roughness of specimens decreases with the increase of G content from 0 to 3 phr (parts per hundreds of resin), when the CB content decreases from 25 to 10 phr, the surface roughness of specimen increases. The resistivity test shows that doping G can significantly inhibit the PTC effect of the semi-conductive layer. The volume resistivity of the semi-conductive layer decreases with the increase of G content and CB content. In addition, charge accumulation of the insulation layer rises and then drops under the action of the semi-conductive layer.

Space Charge Behavior in Epoxy‐Based Dielectrics: Progress and Perspective

“…The internal factors refer to material properties, such as curing agent type, filler properties, and modification treatment, while the external factors are highly associated with operating ambient, including temperature condition, applied electric field, humidity, and electrode status. [29,[33][34][35][36][37][38][39][40][41][42][58][59][60][61][62][63][64][141][142][143][144][145][146][147][148][149] In this section, we mainly focus on three types of EP-based dielectric materials, i.e., pure EP, EP impregnated paper (EIP) composites, and EP-based nanocomposites. A broad perspective on space charge behavior is placed based on the progress of experimental measurements with the consideration of varied internal and external factors.…”

Intelligent model prediction of fluctuant increase of maximum electric field in XLPE insulation using long short‐term memory network algorithm

“…Figure 10 shows the single prediction results of Figure 3 (E max of 120 kV/mm 20°C) with the sample dimension [50,10]. In this case, 50 data of the E max are selected as the training set.…”

“…Consequently, insulation ageing would occur, reducing the lifetime of the cable insulation [6][7][8]. The space charge behaviours depend on the applied voltage, temperature, humidity, and materials, contributing to the complicated dynamic electric field inside the cable insulation [9][10][11]. The characteristics of electric field distortion inside the insulation are regarded as a signal for the diagnosis of the cable insulation state.…”

Optimisation method for carbon black distribution of polypropylene‐based semi‐conductive screen materials and its effect on charge emission behaviour at screen/insulation interface

“…The screen layer material used for HV cables not only needs good CB dispersion but also needs good thermal stability to ensure the screen layer does not melt or deform under thermal shock from overloads and short circuits. Traditional screen material used in cross-linked polyethylene (XLPE) cable is composed by adding conductive particles into polar resins such as ethylene-butyl acrylate, ethylene-ethyl acrylate, or ethylene-vinyl acetate copolymer (EVA), and then cross-linked into thermosetting material with sufficient thermal stability [13][14][15]. Meanwhile, CB particles exhibit good dispersion in polar matrix materials, and there is no obvious CB agglomeration happened.…”