The influence of degassing and heat treatment on the electric field distribution in extruded HVDC cables

Extruded HVDC cables with XLPE insulation are becoming an alternative to mass impregnated HVDC cables at voltages ≤ 320 kV. However, due to peroxide decomposition products resulting from the manufacturing process extruded HVDC cables require more focus on degassing and heat treatment procedures in order to reduce charge accumulation and to achieve a desired electric field distribution during operation. Typical distributions of peroxide decomposition products are studied in this paper with respect to the influence on electric field distribution. It can be seen that a heat treatment procedure which reduces the concentration gradient of the decomposition products impacts the electric field distribution in the cable insulation.