Single-Phase Ferroresonance in an Ungrounded System During System Energization

Abstract

Ferroresonance often occurs in power systems during system switching, which creates overvoltage situations and poses great risks to the equipment safety. In this article, a single-phase ferroresonance incident during a system energization process is presented, which occurred at a single-phase station service transformer in an ungrounded system, causing a surge arrester's failure. This incident is investigated through the PSCAD simulation and the analytical analysis. To validate the PSCAD simulation model, the relay field record is compared with the PSCAD simulation results. Several case studies are conducted using PSCAD simulation to evaluate contributing factors to this ferroresonance incident. The root cause is found to be lack of ground in the system during energization. Field practices are recommended to avoid such incidents, which were proved to be effective by successfully energizing the system in the field.