Before a site is placed into open or total suspension (care and maintenance), there are many tasks that need to be undertaken. The following are some of the electrical issues that need to be considered by the site’s electrical supervisor.
Drawings, manuals, records and electrical log book
- Collect all electrical drawings, records, manuals and the electrical log book and place in secure storage.
Care and maintenance – Portable tools and equipment
- Collect all portable electrical tools and equipment, attach out-of-service tags and place in secure storage. Note that these must not be returned to service until tested and tagged.
Care and maintenance – Identification of circuits to remain energised
Is power required for security lighting, security buildings, boom gates, alarm systems, or pumps?
Is it intended to rotate any machinery during care and maintenance?
- Use single line drawings (SLDs) to identify circuits that are required to remain energised (e.g. autolubrication systems) and the distribution boards from which the circuits originate.
- Consider maintaining power supplies to uninterruptible power supply (UPS) devices to prevent premature battery failure.
- Consider connecting power supplies to programmable logic controller (PLC) and supervisory control and data acquisition (SCADA) systems to prevent program corruption. Back up and securely store PLC and SCADA control programs.
- Identify necessary generator supplies and connection points, and arrange circuits to island equipment as required.
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Care and maintenance – Preparation of electrical equipment
What needs to be done to prepare equipment for downtime?
- Lift the brush gear from drives incorporating commutators, and place warning signs on terminal boxes.
- Consider energising drive heater circuits, where installed, and place warning signs on terminal boxes.
- Check silica gel breathers on all transformers. Replace or reactivate as necessary.
- Check the insulating oil levels in all transformers, switchgear and circuit breakers. Top up as necessary.
- Where installed, close and lock earthing switches onto unused high voltage (HV) cables.
- Open and lock all air break switches on unused overhead power lines.
- Disable all reclosers on unused overhead power lines.
- Securely lock and weatherproof all substations, motor control centres (MCCs), distribution boards and electrical equipment enclosures.
Cables
- Where cables are redundant and disconnected, short all active cores together and to earth, and bag or fit heat shrink caps at both ends. Refer to the Wiring Rules.
CMD allocation
- If the site is connected to the South West Interconnected System (SWIS), carefully consider the surrender of the site’s contracted maximum demand (CMD) allocation to Western Power Corporation (WPC) as it might not be reinstated if needed later.
Care and maintenance – Regulatory issues
- If any circuits and installations remain energised on site, then an electrical supervisor must remain appointed in accordance with regulation 5.10 of the Mines Safety and Inspection Regulations 1995 and section 44 of the Mines Safety and Inspection Act 1994.
- If it is intended to perform any electrical installation work while the site is under care and maintenance, consider maintaining the work licence for electrical in house installing and any exemption from submission of notices.
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