Effect of Eccentricity on Electrothermal Runaway in the Insulation of Extruded High Voltage DC Cables

This article presents the electrothermal 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 nonlinear, temperature (or load current)-dependent field dynamics as compared to alternating current (ac) case. The effect of eccentricity on electrothermal breakdown has not received adequate attention till now. In this work, the authors simulate the runaway in an HVDC cable and investigate the impact of eccentricity under different scenarios, such as short-time and long-time instability, using a comprehensive finite element method (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.