Use of a safe system of work

Restriction of live working

Work dead is the normal approach. In Great Britain, Regulation 14 of the Electricity at Work Regulations permits dangerous work on or near exposed live conductors only if all three conditions are met: it is unreasonable in all the circumstances for the conductor to be dead; it is reasonable to work on or near it while live; and suitable precautions prevent injury. Commercial convenience, lost production or a claim of no alternative is not enough.

Competent assessment and planning must consider how to avoid live work and control the remaining hazards, including arc flash and stored energy. Other countries have different legal wording. This chapter is revision material, not authorisation or a complete procedure for live electrical work.

The precautions should have been identified in the risk assessment. It is not always possible to follow one rigid procedure for every situation, but the following precautions must be followed:

• install temporary insulation, protective enclosures or screens to prevent parts at different potentials being touched at the same time
• use temporary barriers with warning notices to keep unauthorised people away from the work area
• make sure adequate clearances are set and kept when working near live equipment
• make sure workers are competent, can recognise their own limits and know when to seek help
• provide supervision
• provide lighting and working space that are adequate and free from trip hazards
• use robust, properly insulated tools
• use test instruments with insulated probes and fused leads
• keep tools and test equipment in good condition and replace them if damaged
• store tools correctly, without using horizontal surfaces and projections inside control cabinets, and make sure objects such as tools and bolts cannot fall onto exposed live parts
• avoid lone live working
• use suitable personal protective equipment (PPE) to reduce the risk of contact with live parts or earth
• if there is a risk of burns from arcing or flashover that cannot be avoided, consider adequately rated, thermally insulating, flame-resistant PPE

The most common live working activity is testing, typically carried out as part of routine preventive maintenance, diagnostic testing, product testing, commissioning or fault finding. Guidance on safety during electrical testing is in INDG354, Safety in electrical testing at work.

Isolation

An isolation procedure is a set of predetermined steps to follow when workers have to carry out tasks such as inspection, maintenance, cleaning or repair on an electrical system. Its aims are to:

• isolate all sources of electrical energy so that an accidental release of electricity cannot occur
• control all other hazards to those doing the work
• make sure entry to a restricted area is tightly controlled

The main steps of an isolation procedure are:

1. Prepare. Plan the job and identify every energy source.
2. Notify. Tell everyone affected that the equipment is to be shut down.
3. Turn off or shut down. Stop the equipment by its normal controls.
4. Isolation. Disconnect it from every energy source.
5. Apply locks and tags. Lock off the isolation points and attach tags.
6. Control stored energy. Release, discharge, restrain or otherwise safely control pressure, gravity, electrical and other stored energy using the assessed method.
7. Verify the safe state. A competent person must use the correct method and suitable equipment to prove dead and verify isolation. Trying the start button alone is not proof of electrical isolation.
8. Perform the task.
9. Make safe, inspect and restore. First confirm people and tools are clear, safeguards reinstated and linked work complete. Remove locks and tags only through the authorised release procedure, notify affected people and restore energy in a controlled way.

Summary notes for Element 11 · Cheat sheet · Glossary. A study aid, not published or endorsed by NEBOSH.