Safe isolation on 3-phase systems in the UK currently requires a 10-point test plan
A quick internet search bring up the following 10 point test plan.
L1 – L2
L2 – L3
L1 – L3
L1 – Neutral
L2 – Neutral
L3 – Neutral
L1 – Earth
L2 – Earth
L3 – Earth
Neutral – Earth
Personally I think the industry should write it down as follows
Earth to L1
Earth to L2
Earth to L3
Earth to Neutral
Neutral to L1
Neutral to L2
Neutral to L3
L1 – L2
L2 – L3
L1 – L3
It shows clearly the first 7 sets of test FROM LEAST dangerous connector/probe first
Steps to Safe Isolation
Permission: Secure authorization to isolate the circuit.
Identify: Locate the correct isolation point.
Switch Off: Turn off the 3-phase supply.
Lock Off: Secure the isolator with a padlock and keep the key.
Warn: Place "Danger" notices and "Do not switch on" labels.
Prove (Before): Test your voltage indicator on a known live source/proving unit.
Test: Perform the 10-point test above.
Prove (After): Re-test the indicator on the proving unit.
The Lock Off: Secure the isolator with a padlock and keep the key. Should EMPHASISE preferred lockoff is upstream from DB/CU
Important Notes:
Always use a GS38-compliant voltage tester; voltage sticks are not suitable for proving dead
Now for the 11th test part
Use a suitable clamp meter on the tails to check for leakage current initially set to Amps then mA after the isolation step/lockoff step. This is vital to help detect PEN faults/Diverted Neutrals
As always please be polite and respectful in this purely academic debate.
Come on everybody let’s help inspire the future
