Re: High Voltage Failure
Please note that OSHA rules require that the cause of the trip be investigated and corrected before a tripped breaker is reclosed.
Under re-closing both the 20A and 100A breakers a short-circuit happened again, and this time not only are the two breakers cut out, but the whole high-voltage circuit (4,160V) is cut out on a HV earth failure.
The low voltage fault current is seen by the transformer windings and its primary OCPD device. If the current is high enough on the secondary the primary device will act to clear the fault. Under normal conditions, proper OCPD coordination will have the secondary devices trip before the primary. Also note that on the secondary, you cannot selectively coordinate most small(less than 400A) breakers for high fault conditions
The code only applies to T&M work....it does not apply to contract work.