A New Stabilizing Method of Differential Protection Against Current Transformer Saturation Using Current Derivatives

As the power system expands, the need to provide reliable energy has also increased, consequently. One of the issues that makes this problem difficult is detecting of short circuit faults in the grid under saturated current transformers (CT) condition. In the case of CT saturation, protective relays encounter many problems. This paper presents two new and practical solutions to tackle this problem. Firstly, it is proposed to use a combination of two signal processing indices for detecting CT saturation in the network fault condition. Then, it is suggested to modify the differential protection characteristic to stabilize it against CT saturation. The simulation has been done on modeled real network in EMTDC/PSCAD and its outputs are analyzed using MATLAB. The results of the simulation confirm the efficiency and usefulness of the proposed method for stabilizing the differential protection against CT saturation.