To address ferroresonance caused by the transient process of single-phase earth faults in 6 ~ 35 kV non-effectively grounded distribution networks

this paper analyzes the generation mechanism of ferroresonance and its hazards to voltage transformers and the safe operation of power systems. The technical characteristics and limitations of conventional primary ferroresonance suppressors are then discussed

and an active ferroresonance suppression device based on the physical properties of thermistors and integrating an electromagnetic switch is designed. Simulation verification under fault conditions that occurred repeatedly at a substation shows that the developed active thermistor-based ferroresonance suppressor can rapidly suppress ferroresonance and effectively solve the problems of ferroresonance overvoltage in voltage transformers and overcurrent during earth faults.