Influence of Distributed Compensation on Earth Fault Protection in Cable Distribution Systems

The growing use of underground cables in distribution systems increases the capacitive coupling of the network to earth and as a consequence the capacitive earth fault current. In rural systems consisting of long cable feeders the extensive reactive current transportation gives rise to resistive losses that influence the earth fault protection. Simulations carried out in this work suggest the resistive losses disable sensitive earth fault protection in centrally compensated resonant earthed neutral systems unless unconventional low earth fault protection thresholds are applied. The introduction of distributed compensation will decrease the reactive current transportation and associated resistive losses. Distributed compensation will enable the use of sensitive earth fault protection using conventional protection thresholds.