Detecting Broken Conductor Faults in the Presence of Inverter-Based Resources

The increasing number of inverter-based resources (IBR) in the power system and the fast response of IBRs during faults impose new challenges for protection. An open circuit (OC) fault can be the result of a breaker malfunction or a broken conductor, where the broken conductor fault can occur with or without a series arc. It is essential to develop a fast broken conductor fault detection method in the presence of IBRs. An undetected broken conductor fault can degrade power quality, cause local outages and forest fires, and cause personnel injury if conductors contact the ground. Existing broken conductor fault detection methods typically use a measure of current imbalance; however, these methods can be inaccurate due to the current imbalance not being local to the faulted line. This paper proposes a method using current magnitudes and angles to detect a broken conductor fault with and without a series arcing event when the local generation is supplied by grid-forming (GFM) and grid-following (GFL) IBRs. The proposed broken conductor fault detection method without arcing looks for a decrease in phase current, an increase in zero-crossing events, and an impedance angle that falls in a capacitive window. The proposed broken conductor fault detection logic with arcing alerts for a decrease in phase current and impedance angle over a predefined series arcing window. Time domain simulation studies are performed in PSCAD/EMTDC to evaluate the effectiveness of the proposed broken conductor for both GFM and GFL IBRs in approximately one fundamental cycle.