6.10.5 Decide whether it is reasonable to work live!
“The risk assessment should inform managers and supervisors whether it is reasonable in all the circumstances to work live. The decision should not be taken lightly. At this stage the economic and operational factors should be evaluated against the risks involved before making a decision, bearing in mind that the risks associated with working live can be very serious. Minor inconveniences arising from working with the equipment dead, sometimes arising from commercial and time pressures, will very rarely outweigh the risks associated with live work”. (Source: HSG 85 Electricity at Work – Safe Working Practices)
6.10.6 Decide whether suitable precautions can be taken to prevent injury!
Once the above requirements have been met, the third condition for the justification of live working must be met which is: suitable precautions (including, where necessary, the provision of personal protective equipment) have been taken to prevent injury. At this stage, the hazards and the precautions to prevent injury should all have been identified and recorded in the risk assessment as detailed in previous paragraphs.
6.10.7 FINALLY - Proceeding with Work
After all the above steps are satisfied, implement safe working and ensure adequate monitoring and supervision. Things change in workplaces, and risk assessments need to be reviewed on an ongoing basis. Consider a “toolbox talk” to run through the requirements of the risk assessment and ensure that these are understood by those undertaking the work.
In addition, the worker must:
- Make sure that any special equipment and PPE is properly used and maintained.
- Pay attention to housekeeping and ensure that the work area is organised and tidy.
- Keep the duration of any live work to a minimum.
- Store tools correctly – horizontal surfaces and projections inside control cabinets should not be used – and ensure that objects such as tools and bolts cannot fall onto exposed live parts.
- Maintain tools and test equipment in good condition and replace them if damaged.
- Avoid lone live working at any stage and make sure that any accompanying person is competent.
6.11 Testing for DEAD
A core principle of most electrical safety programmes is dead working and to always try to avoid live working. Why I emphasise the avoidance of live working, is that sometimes, there can be danger in making equipment dead, or putting equipment in an electrically safe condition.
I recall, many years ago, a utility company repairs electrician being called out to look at a low voltage cable which had been severed by excavation in the street. The current carrying conductors in the severed armoured cable were clearly visible and the electrician jumped into the trench to see if they were still live. The conductors were still live, but the act of prodding them with a test lamp initiated an arc flash incident in which he received some burns. A footnote to this incident is that the same electrician did a very similar thing some years later, but this time was very severely burnt from the resulting fireball and was hospitalised.
TREAT ALL ELECTRICAL EQUIPMENT AND CONDUCTORS AS LIVE UNLESS PROVEN DEAD.
So, with that in mind, how shall we safely test for dead. Whilst the following is not meant to be a definitive guide to isolation practices or lock out tag out procedures, it is a practical approach to ensure that the process of testing at low voltage will not create danger from arc flash. This is to be taken as a whole and no one measure should be taken in isolation.
STEP 1. COMPETENCE. Designate the person who will have responsibility for the isolation. We will call him/her the designated person here, but that term can be changed as long as it is clear, written into the safety rules and does not clash or be confused with any other terms in use. Make sure that the designated person possesses the competence required to undertake the isolation. By that I mean a person who has the skill, knowledge, attitude, training, possess the experience to undertake the work and has the ability to recognise the extent of their own competence and leading them to take appropriate action. Specific requirements over and above general electrotechnical knowledge are that he/she will have an adequate understanding of the system to be worked on and practical experience of that class of system, an understanding of the hazards which may arise and the precautions which need to be taken and an ability to recognise at all times whether it is safe for work to continue. Sadly, the repairs electrician that I spoke about earlier failed on all three counts.
STEP 2. IDENTIFY. The designated person must correctly identify and make dead and Isolated from ALL points of supply. This will include alternative feeders and emergency standby arrangements such as generators and uninterruptible power supply systems. Correctly identifying circuits will take away the trial-and-error approach and reduce the risk.