Effects of Temperature on Space Charge and DC Conductivity Behaviors in PP/ULDPE/Graphene Nanocomposite for HVDC Cable Insulation

Polypropylene (PP), with good electrical and heat-resisting properties, has a great potential to apply as insulation for extruded HVDC cables. The space charge and conductivity behaviors are critical issues in the design of insulation systems for HVDC cable application. Besides, the operating temperature of a loaded cable often varies with load conditions, which has a great influence on the dielectric properties of cable insulation. Therefore, the space charge and DC conductivity characteristics of PP based insulations under various temperatures are studied. In this paper, the space charge and DC conductivity test of the pure PP, PP/ultralow density polyethylene (ULDPE) blends and its graphene nanocomposites are performed at 30, 60 and 90 °C, respectively. The results show that the DC conductivity of all the samples increase with rising temperature, and the conductivity from 60 to 90 °C have a greater variation than that from 30 to 60 °C. The PP/ULDPE blends with a content of 0.01 wt.% graphene nanoplatelets show a good performance of space charge, and DC conductivity at the temperature range from 30 to 90 °C for potential HVDC cable insulation.