Comparison of non-real-time and real-time simulators with relays in-the-loop for adaptive overcurrent protection

Non-real-time or real-time simulators with relays in-the-loop can be used to test and validate adaptive protection systems. In this paper, the non-real-time and real-time simulator test procedures with relays in-the-loop for an adaptive overcurrent protection system in a microgrid with distributed generators (diesel generators) were described, contrasting the test set-up and experiment preparation. In addition, test results for the non-real-time and real-time simulators with relays in-the-loop were compared. Selectivity, reliability and speed for an adaptive overcurrent protection system was validated using both relays in-the-loop test procedures. Of 44 tripping tests ran for both relays in-the loop techniques, the breakers near the fault tripped and the other breakers remained closed in 34 cases, and backup relays tripped when primary relays did not trip in 10 cases (backup tests). Inverse time overcurrent elements tripped breakers at maximum fault currents in less than 0.5 s. To test adaptive overcurrent protection systems, it is recommended to use the relays in-the-loop with real-time simulator instead of non-real-time simulator, to optimize the test validation of primary and backup relays working together.