Single-Phase Short-Circuit Testing of Vacuum Interrupters for Power Systems with an Effectively Earthed Neutral

Circuit breakers using vacuum interrupters (VI) are frequently tested according to the IEC standard 62271–100 and the IEEE standard C37.09. The IEC 62271–100 standard was updated to include additional tests for medium voltage circuit breakers, designed to verify successful interruption in electrical power systems with an effectively earthed neutral. One part of these tests consists of interruption tests on three-phase asymmetric current, which requires a so-called four-wire test circuit. The standard also specifies a single-phase test as a substitute for the three-phase tests. This work evaluates the severity of the single-phase asymmetric test as compared to the three-phase test. It shows that the current single-phase test is a reasonable simulation of the second phase to clear in the three-phase test for interruptions on the major current loop. The test is more severe for interruptions that require an additional minor loop. The IEEE standard also has a single-phase asymmetric test, referred to as T100a 1Ph. The IEC single-phase test at 50 Hz can also cover the comparable IEEE T100a 1Ph test at 60 Hz with a modest increase in the arc time. Attempting to cover the IEEE T100a 1Ph test at 50 Hz with the IEC test would place higher TRV, arc time, and transferred charge stresses on the VI.