Relation analysis for ferroresonance of bus potential transformer and circuit breaker grading capacitance

•Ferroresonance of a potential transformer and circuit breaker grading capacitance is investigated.•This new device is designed to avoid the restriking resonance.•The study mitigates the ferroresonance by inserting resistors in parallel instead of a single one.•Key factors are all examined through simulation analysis, laboratory experiments, and field tests.

This paper presents a methodology to reduce the ferroresonance between a bus potential transformer and circuit breaker grading capacitance. It starts with the investigation of the relations between ferroresonance of a bus potential transformer and circuit breaker grading capacitance, where different resistors are simulated to add in the secondary side of bus potential transformers, anticipating that the ferroresonance occurrence can be better comprehended. In the study, both the driving force factor and the ratio of system-to-ground capacitance and inductance are assessed. In order to confirm the feasibility of the proposed strategy, a ferroresonance-suppression device has been developed and several scenarios have been examined through digital simulations, laboratory analyses, and field validations. Test results support this proposed approach for its ferroresonance-suppression application that is considered.