The electrician placed his personal isolation lock onto a lock box and began work on a sump pump.
As the electrician began to remove the main junction box screws, the pump started.
The NSW Resources Regulator said the electrician was not injured.
"The work procedure contained incorrect isolation information and the electrician failed to test for dead before starting work on the pump," it said.
"When group isolation systems are used, the isolation must be confirmed for all the required tasks.
"When workers lock on to a group isolation, they must check that the isolation is suitable for the task they are conducting. Mine workers must be trained and competent in isolation procedures and should always test for dead before starting work."