Interfacial charge dynamics in multi-dielectrics under various electric fields and thermal gradient

For the reliable utilization of HVDC interconnections, the joint/termination, as the keystone elements have to be engineered with superior performance and reliability. The use of insulating material in cable interconnections different from that of the cable insulation results in dielectric/dielectric interface in the cable joint. Under DC stress, the field distribution in the multi-dielectrics depends on the differences in material constitutive parameters, conductivity and permittivity, and the field profile is complex and difficult to predict under thermal gradient. In this paper, the field distribution in two dielectric bilayer of cross-linked polyethylene (XLPE)/silicon rubber (SiR) and ethylene propylene rubber (EPR)/SiR, as representative of cable joints, have been studied to provide guidance for the safe design and optimization of HVDC joints. The results show that compared with XLPE/SiR, the EPR/SiR sample has better performance with less space charge injection and less electric field distortion. This is because of closer constitutive material parameters and lower space charge accumulation of EPR under DC electric field. The content of this paper can be helpful to explain the interface charging property of multi-dielectrics and further provides significant importance to the selection of materials in developing of HVDC cables.