Equivalent Circuit of Single-Core Cable Lines Suitable for Grounding Systems Analysis Under Line-to-Ground Faults

This paper presents two approaches where the single-core cable line and an additional conductor laid in parallel can be reduced to a simple equivalent π-circuit containing an active element beside the usual passive impedances. The parameters of the equivalent circuit are calculated using a numerical approach where the distributed parameter line was discretized and an analytical approach is based on the wave propagation theory. A series of tests has been performed to determine error levels in both cases showing that they are less than 1%. With numerical examples, we show that the cable equivalent circuit offers a simple way to calculate voltages in complex grounding systems. The results are in good agreement with the previously published calculated and/or measured values. Both approaches offer the possibility of calculating voltage and current distribution along the cable line which gives insight into the significance of each cable component in the complex grounding system.