Safe isolation under the Electricity at Work Regulations 1989 using the GS38 prove-test-prove method and suitable test instruments.
Legal basis
The Electricity at Work Regulations 1989 require that work is carried out with conductors dead unless it is unreasonable for them to be dead and suitable precautions are taken. Safe isolation is the procedure used to prove a circuit is dead before work starts.
The safe isolation procedure
- identify the correct circuit or point of isolation
- switch off and isolate the supply
- lock off using a lock and a unique key kept by the person doing the work, and fit a caution notice
- prove the approved voltage indicator on a known live source or a proving unit
- test all the isolated conductors to confirm they are dead, testing line to neutral, line to earth and neutral to earth
- prove the voltage indicator again on the known source
This prove, test, prove sequence confirms the indicator did not develop a fault between checks.
Suitable instruments under GS38
- use an approved two-pole voltage indicator made to the HSE guidance note GS38
- probes should have finger guards, an exposed metal tip of no more than 4 mm (preferably 2 mm or shrouded) and fused leads
- do not rely on a non-contact volt-stick or an ordinary multimeter to prove dead
- a proving unit gives a known source where a convenient live supply is not available
Why lock off
Locking off stops the supply being restored by another person while work continues, because the only key stays with the worker.