Avoiding Switching Transients on Mv Transformers

This paper explores the potential problems associated with switching transients and the adverse effect on installed equipment. A specific case where mill equipment was damaged to the point of catastrophic failure by repeated exposure to such transient over-voltages is presented and analyzed. The problem was caused by the combination of a medium voltage vacuum circuit breaker powering an unloaded transformer via short cable connections. Recommendations are made on how to avoid similar equipment damage and measures to take during design, installation and operation to minimize issues in the field with similar configurations.