An incident investigation involving a phase-to-earth fault on 1000-volt equipment in the hazardous zone at an underground mine identified ineffective earth connections in a restrained cable plug (SA06-05).

Subsequent to this incident, the mine returned cables to an approved cable repair workshop.

Eighteen plugs were inspected, with eight found to have an extremely poor connection between the plug nose cone and the internal earthing ring. Nine were considered to have a poor connection.

The cable plugs were disassembled and the earth sleeve was found to have an unreliable contact with the earth ring attached to the moulded interior.

The plug is manufactured by CMI Electrical Products and is a 300A 660/1100V Restrained Trailing Cable Plug with Integral Gland (Cat no. AF31/64SB3).

The manufacturer of the plug has developed a solution to give a much improved earth connection.

The NSW Department of Primary Industries has recommended mines immediately implement a program of returning cables with this product attached, taking them to an approved cable repair facility and having defective earth termination rings and earth sleeves identified and replaced.

It said the program must be completed as soon as possible and mines needed to review the implementation of the recommendations contained in SA06-05.

Further information on plugs and receptacles can be obtained from DPI web site, www.minerals.nsw.gov.au.