The impacts of the temperature and electric field on the electrical characteristics in semicon-bonded XLPE insulation

HVDC cables play a vital role in the power transmission system for renewable energy and global power trade. Nowadays, the crosslinked polyethylene (XLPE) extruded cables have been widely applied in power industry due to the superior performance on the thermo-mechanical properties and dielectric properties. The low volume conductivity and the minimized space charge accumulation are the two key requirements for a reliable high voltage direct current (HVDC) cable insulation. This paper reports on the impact of temperature and electric field on the space charge behavior and DC conductivity in XLPE material for cable insulation. The samples were carefully prepared to simulate the real cable insulation structure. A layer of LDPE film mixed with DCP (dicumyl peroxide) was sandwiched between two layers of semicons (also contain crosslink agent) and then crosslinked at 200 °C to ensure the semicon layers were thermally bonded with the XLPE insulation. The crosslinked samples were then degassed in the vacuum oven with for 6 days at 80 °C. The space charge characteristics and the conductivity of the semicon-bonded XLPE samples were measured at room temperature and high temperature. The electric fields were kept at 20 kV/mm and 40 kV/mm and the influences of the electric field and the temperature on space charge dynamics and conductivity in the semicon-bonded XLPE samples are discussed.