According to the Inspectorate’s safety alert, an electrician in the main substation for a CHPP was attempting to operate an 11kV oil circuit breaker (OCB) that had tripped out on an earth leakage fault. The metal tank of the 11kV OCB failed and high-temperature oil sprayed onto the victim’s arm.
He received burns to his right forearm and minor heat trauma to the right side of his face. Hot oil also ignited drawings on top of the drawing cabinet in front of the switchboard along with the spare air-conditioning unit filters at the rear of the switchboard.
“An electrician was attempting to operate the circuit breaker at the time of the incident. The method used by the victim to close the circuit breaker, by standing to one side, greatly reduced the probability of more serious injury,” the Inspectorate said.
It issued the following recommendation when operating electrical switchgear in similar situations:
Ensure OCBs are regularly maintained as part of a mine's maintenance system, including operation of the mechanisms and effective oil sampling and testing;
Follow the manufacturer’s maintenance procedures as a minimum, including any recommendations for maintenance after interrupting faults. This may include service bulletins and alerts issued for this equipment;
Consider older electrical equipment and where it is in its life cycle. Consider if this necessitates a review of operational and maintenance procedures, inspection and testing regimes;
Ensure there are procedures in place covering action to be taken after trips on high voltage circuits;
Identify what arc flash personal protective equipment is required;
Restrict the storage of flammable materials in and around electrical equipment;
Ensure the doors to the switch-room are always readily accessible and include provision for quick exiting, such as a crash bar on the inside of the door;
Ensure the availability of accessible water and first aid materials for treating burns, including in any emergency response vehicle; and
To reduce risk to acceptable levels, it may necessary to move the operator away from the circuit breaker cabinet, necessitating the use of remote open/close facilities or some other mechanism.
The cause of the OCB failure is still under investigation.
