Abstract

With the development of power systems, the need to deliver more reliable energy is also increased. So that electricity consumers expect a minimum level of power outages. One of the issues that makes it difficult is to detect short circuit faults in the network under current transformers saturation conditions. With saturation of current transformers, protective relays encounter numerous problems in dealing with current transformers. The present study aimed to propose useful practical solutions to this problem. To this end, it has been suggested to detect current transformer saturation under network error conditions using wavelet transform and then to change the protective relay logic to deal with it. Differential and distance relays were selected for this task and, for each of them, an algorithm was proposed to detect the saturation current and to deal with it. Wavelet transform, which is a new method in digital signal processing, was used to detect saturation of current transformers. Wavelet transform has high operating speed and can be implemented for protective relays due to its simple structure. Simulation was performed on a power system modeled based on a real network in EMTDC/PSCAD software and the outputs were analyzed using MATLAB software. Simulation results confirmed the efficiency and usefulness of the proposed algorithm.