How do you measure 3 Phase Supply confirming it is correct as in 400V between phases etc.

[RyanF]

I have my AM2 exam and the question I have is how would you confirm supply polarity?

Would you do the following tests:-

L1-L2 L1-L3 L2-L3
L1-N L2 - N L3-N
L1-E L2- E L3-E doing this you should expect 400V reading?

Finally, test Neutral to Earth and expect to be 0 volts.

Would the main isolator be switched off for the 3 phase board or switched on?

This would then be a tick on the confirm supply polarity?

 

[Strima]

All test equipment must be GS38 compliant.

You can test from the incoming side of the isolator. Ideally have the isolator locked off for safety, it's not unknown for people to loose balance and put an hand out to steady themselves.

Using a voltage indicator test L1-E, L2-E, L3-E, L1-N, L2-N, L3-N. You should get around 230 volts on each. I see no need checking Ph to Ph as you have already confirmed polarity and voltages.

Connect the phase rotation tester and check the direction of rotation. This should remain the same throughout the installation.

After
all that testing stick a tick in the box, a bit of an anticlimax...

 

[RyanF]

So testing wise I would do :-

L1-N L2-N L3 -N

L1-E L2 -E L3 -E

I would expext to have 230volts?

Again as you said tick in the confirm supply polarity.

I also have another question carrying out Ipf test you ofcourse have

PEFC ( 3 lead test)

Simply test between Incoming L1- E L2-E L3- E record highest value.

PSCC ( 2 lead test)

Simply test between Incoming L1- N L2-N L3- N

Record the highet value but doubled. The highest out of the two test would be my Ipf?

Is that right or wrong?

All test equipment must be GS38 compliant.

You can test from the incoming side of the isolator. Ideally have the isolator locked off for safety, it's not unknown for people to loose balance and put an hand out to steady themselves.

Using a voltage indicator test L1-E, L2-E, L3-E, L1-N, L2-N, L3-N. You should get around 230 volts on each. I see no need checking Ph to Ph as you have already confirmed polarity and voltages.

Connect the phase rotation tester and check the direction of rotation. This should remain the same throughout the installation.

After
all that testing stick a tick in the box, a bit of an anticlimax...

 

[Pete999]

I have my AM2 exam and the question I have is how would you confirm supply polarity?

Would you do the following tests:-

L1-L2 L1-L3 L2-L3
L1-N L2 - N L3-N
L1-E L2- E L3-E doing this you should expect 400V reading?

Finally, test Neutral to Earth and expect to be 0 volts.

Would the main isolator be switched off for the 3 phase board or switched on?

This would then be a tick on the confirm supply polarity?

L1,L2 and L3 to E will give 230Volts as will L1,L2 and L3 to N

 

[Deleted member 26818]

Not aware that you are required to record PEFC and or PSCC.
You should double the highest measurement and record this as PFC.

 

[RyanF]

Not aware that you are required to record PEFC and or PSCC.
You should double the highest measurement and record this as PFC.

I know there is no place to record it but, the whole point of the two tests is to see under fault conditions if the protective devices installed can withstand the fault current (IpF) and can clear the fault current safely and not blow them to bits.

So on my am2 exam I will simply use the megger and test:-

PEFC ( 3 Lead Test)

Place the Neutral croc clip on the Neutral Bar then test L1–N- E L2-N-E L3-N-E

Keep a mental note of the highest figure.

PSCC ( 2 lead test)

Connect the earth test probe directly into the neutral test lead on the meter and measure between:-

L1- N
L2- N
L3-N

Mental note of highest figure.

The highest overall figure x2. And record this as Ipf
For example PEFC = 1900 Amp
PSCC= 2100 Amp

2100x 2 = 4200 Amps

Therefore, Ipf = 4200 AMPS

Is that correct?

 

[Strima]

Why do a 3 lead test for one and a 2 lead test for the other?

If there's no RCD present then 2 lead test will suffice. Line to E for PEFC and Lines to N for PSSC, double the PSSC result if the test meter is not capable of testing line to line.

Record the highest result out of the lot.

 

[RyanF]

Why do a 3 lead test for one and a 2 lead test for the other?

If there's no RCD present then 2 lead test will suffice. Line to E for PEFC and Lines to N for PSSC, double the PSSC result if the test meter is not capable of testing line to line.

Record the highest result out of the lot.

So when I do my am2 I will be aloud to simply use a two lead test on both? PEFC and PSCC there is only RCBO,s which I believe are on the lighting circuit and the ring main circuit. Obvs highest fig doubled and record on the test sheet as Ipf value.

 

[Strima]

You carry out those tests as close to the origin as you can, so only main switch. Ideally on the incoming side of the main switch with the board isolated to reduce the risk of accidental contact with live conductors.

 

[RyanF]

You carry out those tests as close to the origin as you can, so only main switch. Ideally on the incoming side of the main switch with the board isolated to reduce the risk of accidental contact with live conductors.

I understand that so what I said before is correct with two probe PSCC test Lines to Neutral
PEFC test Lines to Earth.

Also how would you complete RCD testing on a RCBO which is installed on a lighting circuit? I know how to do it for sockets. But not sure how to do it for lights as you cant remove any fronts or pendant covers as this is a live test so all has to be done from the DB but how?

 

[Strima]

You test RCDs/RCBOs with loads removed. The best way to do this is at the device itself.

Google the Megger user guide it will show you how to test using the leads.

There is nothing to stop you from asking the examiner to show you how to use the test meter as they don’t expect you to know everything about the test kit.

 

[RyanF]

Would you happen to send me a youtube link to watch the video as I tend to stuggle to find the videos etc? Thanks

 

[RyanF]

So How would you test the lighting circuit RCBO? Like step by step?