Investigation of Ferroresonance Incidents in the EPB Distribution Network

The purpose of this paper is to present the analysis outcome of two incidents in the EPB's (of Chattanooga) distribution network which have been attributed to unique conditions hitherto undocumented in the literature. The first observation was recorded by an S&C IntelliRupter® using its new PulseClosing® technology which was adopted by EPB as part of its smart-grid deployment. The second incident involves an actual wye-connected capacitor bank in which a unique cascade of events involving a capacitor phase failure, loss of bank neutral, and single phase switches led to downstream damaging voltages. Use of a real-time simulator made the study of the affected network section feasible and confirmed that the incidents were caused by ferroresonance in the involved transformers.