Transient circuit implementation of arc models with particular focus on arcs in low-voltage power cables

Abstract

Accurate and detailed fault arc models are increasingly important for development of modern power system protection algorithms which demand very granular and realistic time domain simulation. While the literature spans several decades, few contributions specifically address arcing in low voltage (LV) power cables. Such cables are usually installed underground, underwater, or even in space, making them difficult to access in the field. Real world fault studies on LV power systems are difficult and disruptive so existing fault data is scarce. Therefore to generate reliable and extensive data on the influence of fault arcing on power networks, electromagnetic transient (EMT) timescale simulations of the grid are required at circuit level, together with a commensurate circuit model of the arc itself. This paper therefore assesses existing arc models for their suitability for implementation in a circuit simulator and, for the first time, presents universal electrical circuits that solve existing arc model equations. Although the existing models have mostly been developed for arcs in high voltage overhead lines and circuit breakers, circuit simulations are presented here to evaluate their suitability for LV power cables. Particular emphasis is therefore given to the model inspired by the ablation process as the arc propagates through the cable dielectric. Following the circuital implementation of existing models, a novel Low Impedance Arc Model (LIAM) is presented that computes the time varying “ablation” conductance with a reduced number of parameters. Quantitative analysis of the arc conductance as a function of time (for the models considered in this study) was performed to show the important influence of the electrical environment to the development and the shape of the arc. It was found that the resistance of the source driving the arc is of crucial importance. Furthermore, in order to create a more realistic simulation tool, a model of the high frequency component of the arc conductance is demonstrated for the first time.