Three phase polarity test

[gazdkw82]

I have my AM2s coming up and i am a little confused to the live polarity test on a 3 phase circuit. It's the first live test and I dont want to fail on what is a simple test. I know how to perform a live polarity test on a single phase circuit but unsure on the procesure for 3 phase. Is it just L1,L2,L3 to earth and then to neutral?

Furthermore, I could not find any guidance in GN3 or onsite guide to this test.

 

[Lucien Nunes]

I don't know whether the AM2 syllabus requires a particular method but in reality, yes, plus tests between the lines. The tests to N & E prove that the neutral has not been exchanged for one of the lines, and tests between lines prove that the three lines are all different. It would be possible to miswrire a panel to give e.g. L1, L1, L3 on the three line conductors which would still give three readings of 230V to N and E, but the zero reading L1-L2 instead of 400V would reveal the error. Having confirmed that all three lines and neutral are present, a phase sequence test can be carried out.

 

[plugsandsparks]

You need 400V between all phase conductors L1-L2, L2-L3 and L1-L3.
When testing a 3 phase ccts, i test for above, also L1-N, L2 -N and L3-N, then L1-E, L2-E and L3-E and finally N-E. Its so quick to do you end up doing it in your sleep.
Also in real life you also need a phase rotation check to make sure its consistent with the whole installation usually 1,2,3

 

[gazdkw82]

You need 400V between all phase conductors L1-L2, L2-L3 and L1-L3.
When testing a 3 phase ccts, i test for above, also L1-N, L2 -N and L3-N, then L1-E, L2-E and L3-E and finally N-E. Its so quick to do you end up doing it in your sleep.
Also in real life you also need a phase rotation check to make sure its consistent with the whole installation usually 1,2,3

Phase rotation is performed at the end of the live test schedule. After functional

 

[H]

Are you allowed to do all your live tests first.

Supply polarity
Phase rotation
Ze
Pefc
Pscc

or has it got to be on a particular order?

 

[Pete999]

Are you allowed to do all your live tests first.

Supply polarity
Phase rotation
Ze
Pefc
Pscc

or has it got to be on a particular order?

Testing should be done in line with the method laid down in BS 7671 I should think, otherwise what would be the point of the Regulations and / or the course content.

 

[Sintra]

This is from the AM2 guide.

Safe Isolation for Dead Working
All LV installations must be isolated and proven dead before work can commence, except in case when dead working is unreasonable. Don`t forget that electricity kills, so it is vital that everyone in the electrical industry adopts safe working practices.
Safe isolation sequence:
• Seek permission from a relevant responsible person to isolate supply.
• Select the correct and mains approved test equipment and ensure it works correctly by
testing on the proving unit.
• Identify the point of isolation for the system or circuit. Lock off, place warning label and
keep the key to the lock with yourself.
• Test circuit to make sure it is dead.
• Re-test the test equipment on the proving unit.
• Begin work
Testing Single Phase Installation:
Test for voltage between the following:
• Phase and Neutral • Phase and Earth
• Neutral and Earth
Testing 3 Phase four wire systems:
Test for voltage between the following:
• L1 and L2
• L1 and L3
• L1 and Neutral
• L1 and Earth
• L2 and L3
• L2 and Neutral
• L2 and Earth
• L3 and Neutral
• L3 and Earth
• Neutral and Earth
Remember:
When isolating the main source of energy it is also essential to isolate any secondary sources such as standby generators, uninterruptible power supplies (UPS) and microgenerators.
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The full guide can be downloaded here. AM2 Guide - https://www.electriciansforums.net/resources/am2-guide.69/

 

[littlespark]

Someone mentioned a proving unit there....
Most important. Test your probes with unit before and after testing the circuit.

Some examiners can be strict with that

 

[Deleted member 105166]

That checklist doesn't mention proving the circuit live before isolating and proving dead. If you don't prove live first and the circuit is incorrectly labelled at the board, it may already be dead and you could lock off the wrong circuit. Someone could then come along and energise whilst you are working on it.

 

[gazdkw82]

That checklist doesn't mention proving the circuit live before isolating and proving dead. If you don't prove live first and the circuit is incorrectly labelled at the board, it may already be dead and you could lock off the wrong circuit. Someone could then come along and energise whilst you are working on it.

When I was at college that's how we were told to do it. When I recently did my AM2s 2 day brush up they told us to just check the outgoing side