Understanding and Dealing with Ferroresonance

The basic concept of ferroresonance is introduced and explained in engineering terms. A broad set of example problems in distribution, substation, and transmission systems is presented. Included are ferroresonance involving: a) 345-kV bus VTs and circuit breaker voltage grading capacitors, b) lightly loaded 12.47-kV pad-mount transformer fed by underground cable, c) failure of 72 VTs in temporarily ungrounded 50-kV European system, and d) synch-check VT on ungrounded 13.8-kV delta winding of a 115-13.8-kV 18-MVA transformer in distribution substation. Simulation and analysis methods are outlined. Mitigations or fixes are discussed, as well as general guidance for design strategy and specification