Investigation of cable and its accessory insulation in extruded HVDC cable

Polymer insulated HVDC cable and its accessories are one of the most important equipments in flexible DC power transmission and space charge inhibition is always a problem to solve by science and engineering of electrical insulation. Since the 1980´s, there are lots of papers on space charge in cables reported, and there are few papers on electric insulation of accessory. Most of researchers and engineers focus on how to suppress the space charge in cable insulation. However, there is much amount of space charge at the interface between cable insulation and accessory insulation considering there is a big difference of ratios between dielectric constant and conductivity of cable and accessory insulation. And this space charge might distort the local electric field near the interface. Based on the consideration above, both of silicon rubber (SIR) and ethylene-propylene-divinyl (EPDM) rubbers with the same nano-filler of aluminum (Al₂O₃) were investigated at various temperatures. It is found that the conductivity of SIR varies more sensitively than that of EPDM rubber. In order to know which rubber matches cable insulation better, three kinds of commercial cable insulation (A, B and C) have been taken into account. It is found that EPDM with nano-filler of alumina matches A the best.