Fast fault detection challenge for alienation coefficient based bus fault discriminator

One of the latest fault discrimination algorithms used to supervise bus differential protection schemes, is Alienation Coefficient Algorithm (ACA). ACA uses alienation coefficient of current signals during first one-eighth cycle after fault inception to discriminate between internal and external faults. Therefore, the performance of ACA highly depends on fault detection speed. This paper examines the performance of ACA for currently used fault detection technique and the results reveal that ACA fails to detect external fault in case of fast current transformer (CT) saturation. This paper also proposes an alternative fault detection technique for ACA and presents a simulation study to validate the performance. Documented results show that ACA with the new fault detection technique performs better for fast CT saturation during close-in external faults.