Safety
Working dead — the 5 safety rules
How to make an installation safe to work on
As a rule, all work on or near electrical installations must be done with the installation dead. The five safety rules are the fixed sequence that ensures the installation is dead — and stays dead — while you work.
Plan and define the scope of the work
Determine which part of the installation is to be made dead, and who is the person in charge of the work. Obtain the circuit diagram/board documentation so you know the extent of the circuits and can identify the correct isolation point. Unclear boundaries are the most common reason people believe an installation is dead while it is still live.
Rule 1 — Disconnect all poles
Disconnect the supply to the relevant part on all poles (L and N) so the installation is completely isolated from the voltage source. A simple circuit breaker is often not sufficient isolation — use a suitable point of isolation.
Rule 2 — Secure against reconnection
Lock the isolator in the off position (lockout) or remove the fuse, and put up a warning sign: »Work in progress — do not switch on«. The purpose is that nobody else can apply voltage while you have your hands in the installation.
One person, one lock, one key — whoever locked it is the only one who unlocks it again.
Rule 3 — Verify that the circuit is dead
Actively measure that the installation is dead with an approved two-pole voltage tester. ALWAYS test the tester on a known voltage source both before and after the measurement (test before/test after), so you know the instrument worked during the measurement.
Never assume an installation is dead — measure it. Test the tester before and after.
Rule 4 — Earthing and short-circuiting
Earth and short-circuit the isolated conductors where relevant. The rule is mandatory for high voltage; for low voltage it is applied based on a risk assessment (e.g. long cables or installations that can be back-fed from solar panels, UPS or batteries).
Rule 5 — Shield adjacent live parts
If there are live parts close to the work area that cannot be made dead, they must be shielded or cordoned off with insulating material so that you cannot touch them inadvertently.
Carry out the work
Now — and only now — is the installation safe to work on. Keep track of the boundaries: if the work extends beyond the dead part, the procedure must be extended before you continue.
Remove the isolation in reverse order
When the work is finished, screening and earthing are removed, all tools and people are withdrawn, and only then is the lock/sign removed so the installation can be switched on again. Check that nobody is still working before you apply voltage.
Source
Built on DS/EN 50110-1 (work on electrical installations) and the guidance on sik.dk (Danish Business Authority, formerly the Danish Safety Authority).