Protection Relay for Secondary Ferroresonance Suppression in Coupling Capacitor Voltage Transformers

A new protection relay to detect, suppress and mitigate secondary ferroresonance in CCVTs is presented in this paper. The new protection relay uses frequency response characteristic to detect and characterized secondary ferroresonance and an electronic switch with back to back thyristor to introduce a commutable load to the CCVT’s secondary circuit for secondary ferroresonance suppression. The proposed protection relay has been verified with computer simulations and hardware experiments, which demonstrated a successful performance regarding three design aspects, namely, detection, suppression and security.