It cannot be over-emphasized how important it is that isolation of electrical circuits is carried out in a set sequence, and that this sequence is repeated each time a circuit or complete installation is to be isolated.
If the same procedure is followed each time isolation is carried out, it will soon become a habit, which can only be a good thing as it may save your life.
It is vital that the correct test equipment is used for isolation and that it complies with the Health and Safety Executive document GS 38. This document gives guidance on the use of test equipment, particularly leads and probes.
The GS 38 document is not a statutory document but if the guidance given in the document is followed, it will normally be enough to comply with the Health and Safety at Work Act 1974, the Electricity at Work Regulations 1989 and any other statutory requirements that may apply.
The items of equipment that should be available to persons carrying out the safe isolation procedure are:
It is very important to ensure that the circuit that you want to isolate is live before you start. To check this, a voltage indicator/test lamp or a piece of equipment that is already connected to the circuit should be used. If it appears that the circuit is already dead, you need to know why.
• Is somebody else working on it?
• Is the circuit faulty?
• Is it connected?
• Has there been a power cut?
You must make absolutely certain that you and you alone are in control of the circuit to be worked on. Providing the circuit is live you can proceed as follows:
Ensure voltage indicator/test lamp is working correctly.
Test between all live conductors and live conductors and earth.
Locate the point of isolation. Isolate and lock off. Place warning notice (DANGER ELECTRICIAN AT WORK) at the point of isolation.
Test circuit to prove that it is the correct circuit that you have isolated.
Check that the voltage indicator is working by testing it on a proving unit or a known live supply.