THE Queensland Department of Mines and Energy (DME) has issued a safety alert after a shuttle car ran over and damaged its own power supply cable.
According to the alert, the incident caused a short circuit between two live-phase conductors and the earth conductor.
“The fault caused a power surge in the local distribution system, and two people observed a spark between a continuous miner nearby and the rib mesh,” DME mines inspector Brian Lyne said.
During the mine’s incident investigation, according to the alert, the power factor of the Earth Fault Current Limiting Impedance was questioned.
“The use of a neutral earthing reactor (as opposed to a resistor) may contribute to high inrush currents in some system configurations, particularly with clearing earth faults,” Lyne said.
The mines inspector recommends that possible hazards from low power factor neutral connected current limitation must be considered in the development of a coal mine’s safety and health management system.
According to the alert, all neutral connected impedances in service should be checked for compliance with the relevant Australian standard.