Useful Details about Testing Protective Relays with Signals that Include Effects of Travelling Waves

This article shows useful details about testing protective relays with signals that include effects of travelling waves. Test signals were obtained from two electromagnetic transient programs: a) RSCAD for RTDS, which is a real-time tool; b) Matlab/Simulink, for off-line tests with an injector. Furthermore, test signals were obtained using two models for the faulted transmission line (Bergeron model and a frequency-dependent model). The tested relays were a travelling wave relay (SEL-T400L) and two distance relays (SEL-421 and Micom P545). The tests with RTDS were performed at the low-level interface of SEL relays, whereas the tests with the inj ector were performed at the usual voltage and current inputs of distance relays. In general, the results are useful to emphasize the need of contrasting the expected output signals with oscilloscope captured waveforms, because the expected output signals (as shown by injectors' interfaces) can be different than the real injected signals. Despite this fact, the observed behavior of tested relay functions can be considered adequate.