Several incidents have occurred on flameproof free-steered vehicles where electrical faults have not been detected and cleared by electrical circuit protection.
Miners have noticed damaged lighting circuit cables and intermittent arcing. The electrical protection installed failed to detect the faults as the magnitude of the fault current was similar to the normal load current.
The report said inspection and maintenance regimes have failed to identify defective cable installations on the free-steered vehicles and regimes of increased inspection and improved mechanical protection of cables have not prevented further incidents occurring.
Also, electrical protection could not detect and clear faults that were reasonably foreseeable.
The incidents resulted in the development of alternator-based protection systems that can detect such faults and disconnect the supply to the faulted circuit.
The DPI has recommended that all users review the electrical installations on flameproof free-steered vehicles and consider:
- Installation of electrical cables and components such that they are protected and located to minimise the risk from foreseeable damage;
- The suitability of the electrical protection to detect and clear faults that have the potential to cause incendive arcing; and
- Installation of reliable protection systems that can detect intermittent arcing faults and disconnect the electricity supply as quickly as possible.