Field Testing of Voltage Transients Associated with Vacuum Breaker No-Load Switching of a Power Transformer in an Industrial Plant

Reported here are the results of a field investigation of switching-produced transients associated with vacuum circuit breaker switching of an unloaded low-voltage substation transformer. A sufficient sampling of data has been obtained and documented to provide a good statistical basis for this important mode of switching in a very prevalent application area. The results of this field measurements program confirm that the transient voltage environment created by such switching is within, by a wide margin, the expected transient capabilities of the associated power distribution equipment-specific evaluation being made with respect to the switched transformer.