Ferroresonance Effects

Ferroresonance is a mysterious phenomenon that seems to occur capriciously, causing much concern among utility operating personnel. It generally occurs during a system imbalance, usually during switching, that places capacitance in series with transformer magnetizing impedance. This can result in high overvoltages that can cause failures in transformers, cables, and arresters. Any system capacitance can be involved in ferroresonance, but the major concern is about underground cable capacitance.