Grid Side Unbalanced Fault Detection using Soft Open Point in an Electrical Distribution Network

Abstract

Soft open point (SOP) is a power electronic device that installed in place of normally open points in distribution networks. This paper investigates the performance of SOP under an unbalanced line to ground (L-G) fault in a medium voltage (MV) distribution network. A method to detect unbalanced grid side AC faults was developed using positive and negative sequence currents injected into the feeder by the SOP. Simulations were carried out on a network model developed in PSCAD/EMTDC. Local measurements at SOP grid connection point were used to define a fault index. Results show that the fault index, based on the values of positive and negative sequence currents, is able to effectively detect the presence of an unbalanced fault in a MV distribution network.