Impact of Semi-Conductive Layers on the DC Conductivity of XLPE MVAC Cables

The increasing demand for electrical energy poses new challenges on the existing transmission and distribution grid. To overcome these challenges, the DC transmission in the MV grid will play an important role in future. To achieve a cost-effective solution, research is focusing on the use of MVAC cable systems for MVDC. MVDC cables with extruded insulation exhibit phenomena such as the accumulation of space charges in the insulation bulk. Furthermore, space charges accumulate at interfaces. Since the semi-conductive layers in cables represent such interfaces and the interaction with the insulation could be crucial for reliable operation, leakage current measurements are carried out on XLPE plate samples with and without an extruded semi-conductive layer. The material was taken from an MVAC cable. The apparent DC conductivity is measured in a temperature range of 25°C-90°C and for an electric stress up to 20 kV/mm.