Advanced Multi-terminal Line Current Differential Relaying and Applications

Current differential relaying has long been an alternative to directional comparison relaying, especially for short line applications. Current transformer performance has always been one of the limiting factors is using a current differential scheme. Summing the current transformer currents before entering the relay deepens the problem. With the advent of multi-terminal current differential relays, individual currents can be kept isolated throughout the differential process, mitigating the problem. This paper describes differential relaying techniques and shows examples of how keeping currents separate helps solve real application problems