An impedance-based CT saturation detection algorithm for bus-bar differential protection

This paper presents an algorithm for CT saturation detection based on the measurement of the power system source impedance seen at the relay location. The algorithm estimates this source impedance using a short-data window impedance-estimation algorithm and samples taken from the Current Transformer (CT) secondary current and bus-bar voltage. Following the changes on the impedance seen at the relay location, the algorithm is able to detect a CT saturation and send a blocking order to a fast tripping bus-bar differential relay.