Identification Scheme for CT Single-Phase Faults and Busbar Single-Phase Short-Circuit Faults Based on Phase Characteristics

Current transformer (CT) faults can lead to misoperations of busbar differential protection, while busbar high-impedance short-circuit faults may be misinterpreted as CT faults, resulting in protection refusal. An effective identification scheme is needed to differentiate between these two types of faults and to promptly clear the faults to prevent accidents. This paper theoretically analyzes the effects of branch CT single-phase faults and busbar single-phase short-circuit faults on busbar differential current and branch currents, and proposes criteria for identifying the faulty branch and faulty phase based on their characteristics. Then, the differences in phase between busbar differential current and the positive sequence current of the power source branch under both fault scenarios are studied, and criteria for distinguishing between CT single-phase faults and busbar single-phase short-circuit faults are proposed based on these differences. Finally, the effectiveness of these criteria is verified through simulation.