CT saturation effects on performance of digital overcurrent relays

In general, modeling the behavior of the core in current transformers (CTs) used for protection and the effects of its operation outside the linear region are commonly reported in literature. The problem in using a mathematical TC model is to obtain the parameters in a particular case in order to implement that model easily, efficiently and accurately. In this sense, a CT model was implemented in MATLAB based on the theory published by the IEEE Power System Relaying Committee (PSRC) to analyze various factors and conditions that can lead to the CT saturation. The current data obtained from the simulation were converted to COMTRADE format to be used in a injection test equipment to verify the overcurrent relay response behavior. A similar analysis was done in the RTDS (Real Time Digital Simulator) perfoming hardware-in-the-loop simulations (HIL) in order to compare results and validate the tests, which are presented in this paper. current transformer saturation, overcurrent relay, hardware-in-the-loop, real time digital simulator.