Effect of Eccentricity on Electro-thermal Runaway in the Insulation of Extruded High Voltage DC Cables

This paper presents the electro-thermal runaway characteristics of an extruded high voltage direct current (HVDC) cable, in the presence of eccentricity, i.e., a misalignment in the axes of cable conductor and insulation, which is practically unavoidable in extruded cables. In particular, eccentricity in DC case assumes importance due to non-linear, temperature (or load current) dependent field dynamics as compared to alternating current (AC) case. Effect of eccentricity on electro-thermal breakdown has not received adequate attention till now. In this work, the authors simulate the runaway in a HVDC cable and investigate the impact of eccentricity under different scenarios such as short-time and long-time instability, using a comprehensive FEM model. The results show a drastic shift in phenomenon from traditional global thermal breakdown to local thermal breakdown due to eccentricity in power cables. The results are validated with analytical computations.