Verification of the Short-Circuit Current Making Capability of High-Voltage Switching Devices

Switching in of short-circuit current leads to pre-arcing in the switching device. Pre-arcing affects the ability of switchgear to close and latch. In three-phase systems, making is associated with transient voltage phenomena that may have a significant impact on the duration of the pre-arcing period. An analysis of these transients is presented. It was found that pre-arcing times in three-phase systems can be considerably prolonged with respect to a single-phase situation. On the other hand, it is demonstrated that the three-phase interaction has a moderating influence on the peak value of asymmetrical current. A test circuit is described, able to perform three-phase synthetic make tests up to 245 kV at current up to 63 kA, representing all transient phenomena. Specific tests are described requiring the maximum available laboratory power: one with a circuit breaker subjected to direct test and one with a high-speed grounding switch subjected to synthetic tests.