Mining Plant Electrical (HV Mobile) SWMS

High voltage maintenance on draglines, electric rope shovels and other mobile mining plant exposes electricians, fitters and supervisors to some of the most severe energy hazards in Australian industry. Trail cables carrying 6.6 kV to 22 kV, slip ring assemblies, transformer cubicles and motor cooling circuits must be isolated, tested dead and earthed before any intrusive work begins, often in remote pits where rescue response is measured in tens of minutes. This SWMS addresses the integrated electrical, mechanical and mobile plant interface risks unique to surface coal and metalliferous mining HV maintenance. Under WHS Regulation 2025 (and mirror provisions in the WHS Regulation 2011 carryover in NSW, QLD and other jurisdictions), HV electrical work and work adjacent to energised mobile plant are High Risk Construction Work and High Risk Work, mandating a written SWMS before work commences. The document captures isolation boundaries, test-before-touch protocols, earthing sequences and exclusion zones consistent with AS/NZS 4836, the Electricity Safety (Network Assets) framework, and the relevant state mining electrical safety legislation.

Hazards identified

7 hazards covered, sorted by priority.

Control measures

Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.

1. 1Elimination — Defer all HV intrusive work until the dragline or shovel is fully de-energised at the substation breaker, walked to a safe park position, and the trail cable disconnected at the skid.
2. 2Elimination — Eliminate live HV testing by performing diagnostics through fibre-optic protection relay ports rather than opening energised cubicle doors.
3. 3Substitution — Substitute manual switching with remotely operated racking trolleys and motorised earth switches to remove the worker from the arc flash boundary during breaker operations.
4. 4Substitution — Replace oil-filled instrument transformers with dry-type units during overhaul to remove flammable dielectric and reduce confined space entry frequency.
5. 5Engineering — Apply a verified isolation, lock, tag, test and earth sequence using calibrated HV voltage detectors to AS 4202 and portable earthing leads rated for prospective fault current at the point of work.
6. 6Engineering — Establish swing radius exclusion barriers, key-exchange interlocks between operator cab and electrical isolators, and proximity detection on adjacent mobile plant per AS/NZS 4240.
7. 7Administrative — Conduct documented pre-start under this SWMS with electrical work permit, switching schedule sign-off by an Authorised HV Operator, and JSEA verification of arc flash incident energy calculations.
8. 8Administrative — Maintain a competent standby observer with HV rescue training, insulated rescue hook and defibrillator at the work front for the duration of all HV tasks.
9. 9PPE — Wear arc-rated coveralls, hood and gloves matched to the calculated incident energy (minimum Category 2, 8 cal/cm² for cubicle entry post-isolation), Class 2 HV gloves to AS 2225, and dielectric footwear.
10. 10PPE — Use full body harness with twin lanyards and shock-absorber to AS/NZS 1891 for boom and mast access, with rescue plan referenced in this SWMS and equipment staged before ascent.

Applicable Codes of Practice

High-Risk Construction Work triggered

Worked example

At a remote open-cut coal operation, a four-person electrical crew is scheduled to replace a failed motor cooling blower on a walking dragline during a planned 12-hour shutdown. At the pre-start brief in the crib hut, the supervisor opens this SWMS on the site tablet and works through it line by line with the crew. The hazard register flags inadvertent re-energisation, capacitive discharge and swing radius crush as HIGH priority for this task. The crew confirms the switching schedule has been executed at the 22 kV substation, the trail cable is disconnected and visibly parked, and portable earths are installed at the machinery house bus. Two workers sign on as HV Authorised, one as Standby Observer with the rescue hook, and the apprentice is logged as observer-only. During the task, the crew detects residual voltage on the blower motor frame when the test instrument is applied — the SWMS control requiring a second discharge cycle through earthing leads is invoked, the supervisor pauses work, and the additional five-minute discharge is documented in the permit annex. Work resumes only after a second test-dead confirms zero potential, and the sign-on sheet attached to the SWMS is updated to reflect the control adjustment before the blower is unbolted from the motor housing.

Related legislation

• WHS Act 2011 (model)
• WHS Regulation 2025
• AS 2550 — Cranes, hoists and winches; AS 1418 series

Frequently asked questions