Analysis and Simulation on Intermittent Arc Grounding Overvoltage for Neutral Grounding via Arc-suppression Coil with Shunt Resistance in 35 kV Urban Distribution System

Abstract

Due to the significant increase of line-to-ground capacitive current, for urban distribution networks mixed by overhead lines and a larger number of cables, the higher electromagnetic transient overvoltage presents not only always on fault phase and neutral point, but also on non-fault phases when some intermittent arc grounding faults occur. Some arc-suppression coil which has a relatively smaller overcompensation tuning-off degree is mainly used to compensate the line-to-ground capacitive current, reduce the arc residual current and reignition times, and then increase the self-restoration probability after a single phase intermittent arc grounding fault occurs. At the same time, according to the characteristics and performance requirements of distribution systems, a relatively smaller shunt resistance is mainly used to quickly release the charge of line-to-ground capacitance, improve the decay rate of overvoltage of fault phase, non-fault phases and neutral point respectively, reduce the rising speed of neutral point recovery voltage and its amplitude after the intermittent arc dies out, so that the transient overvoltage can be restrained effectively. Results of transient numerical analysis and ATP simulation have demonstrated the mode of neutral grounding via arc-suppression coil with shunt resistance is an optimum choice which is applicable to 35 kV urban distribution networks mixed by overhead lines and cables.