Multi-Frequency Surge Withstand Capability Tests for Protective Relays

The reliability of solid state protective relays in the hostile electromagnetic environment of high-voltage switchyards and substations has been improved by the use of surge withstand capability (SWC) tests. Ontario Hydro relay specifications call for a SWC test with a surge test wave having frequency, amplitude, and source impedance as variable and interdependent parameters. The need for a multi-frequency SWC test with a frequency range of 0.1 to 2 MHz is confirmed by field surveys of surge characteristics, data from actual SWC tests, and laboratory investigations of SWC frequency dependence. A simple, moderately-priced SWC tester capable of generating accurately defined test waves within the defined range of test wave parameters is described