Guidance about earth leakage protection

Requirements

The person responsible for the safety of electrical equipment at a mining operation must ensure that an earth leakage protection device is provided for:

• all alternating current circuits installed in underground mines, quarries, or as part of a dredge (other than a floating treatment plant)
• all circuits providing alternating current supply to portable, mobile or moveable equipment.

High voltage (HV) circuits

Where a high voltage circuit supplies alternating current exceeding 1,000 V, the circuits specified above must have an earth leakage protection device.

For high voltage circuits, regulation 5.24(2) requires the earth leakage protection device to operate at an earth leakage current not exceeding 2 A. This must be achieved in the context of safe step and touch voltage limits (i.e. appropriate engineering judgement).

The earth leakage protection device should operate, in a reasonable time frame, in accordance with Appendix F5 of Australian Standard AS/NZS 3007:2013 Electrical equipment in mines and quarries-Surface installations and associated processing plant.

Low voltage (LV) circuits

For low voltage electricity, the circuits must have an earth leakage protection device that incorporates a readily accessible means for testing the operation of the device.

Residual current devices (RCDs) are earth leakage protection devices provided to final sub-circuits to isolate the electrical supply to socket outlets if the current flow to earth exceeds 30 mA.

For low voltage circuits, regulation 5.24(2) requires the earth leakage protection device to operate at an earth leakage current not exceeding 1 A. This must be achieved in the context of safe touch voltage limits (i.e. appropriate engineering judgement must be applied to this regulatory requirement).

The earth leakage protection device should operate, in a reasonable time frame, in accordance with Appendix F5 of AS/NZS 3007:2013.

Australian Standard AS/NZS 3000 Electrical installations, also known as the Australian/New Zealand Wiring Rules, explains where to install RCDs within low voltage circuits.

Surface operations

A mining operation is required to have a system for maintaining all electrical equipment and installations in safe working order.

As a minimum, the maintenance system should include the testing of earth leakage protection devices every 6 months by means of the test facility and every 12 months by injection testing.

Underground operations, quarries and dredges

Monthly testing is required for earth leakage protection devices installed in underground mines, quarries, or as part of a dredge (other than a floating treatment plant).

All earth leakage protection test results, or the location of the results, must be recorded in the electrical log book.

It is also strongly recommended that an adhesive label be attached to all earth leakage devices identifying the date of testing, as well as the person who carried out the testing. For large switchboards with more than one device, a combined label for the entire board can be used.

Only a licensed electrician may test earth leakage protection devices where the electricity supply exceeds 1,000 V AC.

For low voltage circuits where the alternating current does not exceed 1,000 V, a competent person may undertake the following RCD testing provided they use the socket outlet when conducting the operating time test.

Two types of testing must be conducted for RCDs used in mining operations:

• push button test (in-built test facility)
• operating time test (an RCD tester may be used).

For all other low voltage circuits where RCD testing requires hard wiring, an operating time test must be conducted by a licensed electrician.

Further information: When an RCD fails one or both of the above tests, the competent person is responsible for recording the outcome and immediately placing ‘out of service’ tags against further use. The faulty RCD must be serviced or replaced by a licensed electrician.

Portable equipment used in heavy operating environments such as workshops, mining area, processing area, construction sites and similar places must be examined, tested and tagged on a quarterly basis.

Other electrical equipment and cables need to be periodically examined and tested at such intervals that will ensure safety.

For low voltage portable equipment where the alternating current supply does not exceed 1,000 V, a competent person may perform testing and tagging provided they use a portable appliance tester. For all other low voltage portable equipment where the test requires hard wiring, a licensed electrician must conduct the equipment testing and tagging.

As long as the tags identify the date of examination and testing, as well as the person who carried out the examination and testing, mining operations may either use their own tagging system or choose to follow Appendix F of Australian Standard AS/NZS 3012 Electrical installations - Construction and demolition sites.

All test data must be recorded in the electrical log book, or an entry made describing where the test results can be found.

Construction work at mining operations must be carried out in accordance with Australian Standard AS/NZS 3012 Electrical installations – Construction and demolition sites.

This standard requires all final sub-circuits of construction wiring to be protected at the switchboard by an RCD with a maximum rated residual current of 30 mA, to provide protection for all socket outlets.

Portable equipment means any equipment that is intended to be normally held in the hand during use or which can be carried by a person.

Mobile equipment means any equipment that is too heavy to be portable equipment but is capable of being moved without discontinuing its electric power supply during its use.

Moveable equipment means any equipment that is too heavy to be portable equipment but that is moved about between periods of use with its electric power supply disconnected.