How to carry out PEFC and PSCC on a three phase db with a rcd as the supply?

[RyanF]

Ive got my am2 resit tommorow for my live testing and I ran out of time and failed as well as I carried out the ze test on 2 lead high thus tripping the rcd.

So now I know for next time to complete this on a 3 lead LOW test and measure ze with earth disconnected etc.. then connect main earth back after the test.

But how would you measure pefc and pscc on the three phase db.

The plan I had was for PEFC:-

Set the megger mft1740 to L-PE on 3 low test and croc on to the main earth first, then probe on the Neutral then the phase.

So I would do :- L1- N- E
L2- N -E
L3 -N-E

Note down the highest value for PEFC.

Then same connections set the tester to L-L/L-N to measure PSCC

Same test points again

L1-N-E
L2-N-E
L3-N-E

Note down the highest value as PSCC.

If meter can measure phase to phase then do the tests. But, if not simply take the highest value and times by 2 or more accurately 1.732.

Then record this value as PFC.

Is this right or should I be doing 2 lead low test, but wont this trip the rcd? I have in my mind to do 3 lead low test to not cause any imbalance in the rcd.

Cheers!

 

[Strima]

What test meter will you be using? Have you Googled the user guide for the test meter?

 

[RyanF]

What test meter will you be using? Have you Googled the user guide for the test meter?

Yeah I have doesnt really give a clear description as the manual is difficult to follow/ understand for the questions I have...

 

[westward10]

This is the second thread you have opened in a similar vein to the one you started Friday with 47 posts. If you don't know the answer by now another thread is probably not going to help you.

 

[casperLennon]

The assessor will help as each meter may differ from the normal one they use

 

[Risteard]

On a TT system PEFC won't be the PFC. Only PSCC is relevant, and it is the maximum value between phases that you need (or double the highest phase to neutral value).

Technically a phase to phase to phase fault (i.e. a simultaneous fault between all three phases) will be the worst but we can't measure this.

 

[DavidSpark]

You would never energise an installation with the earthing conductor removed for obvious reasons. The Ze test is done on the supply side of the mainswitch/protective device.

 

[Richard Burns]

Probably too late, so good luck in the test.

You know from the design of the test bay that you have an RCD in circuit at all times and you do not want to trip this therefore whenever you are measuring Zs, Ze, PEFC then use the 3 lead Lo test setting.

For the testing you have access to all conductors and so there is no need to attempt any other method of testing when testing to earth.

You should not need the green lead to earth for the PSCC test, because of the test conditions you should only test between neutral and each phase as it is not considered necessary to test between phases, the highest measured result is multiplied by 2 to give the value to record on the test sheet as PSCC.

 

[PEG]

Yep,i think we sometimes forget,that the test set-up,is different,from most of the actual real test situations,which is a bit disheartening.

That said,an understanding of the testing procedure,means the candidate should not be troubled by this.

I mean,Ze/Zb...potato/tomato...

I reckon we should go back to the days when,for example,you did military basic training,and there was an accepted percentage of fatalities...

 

[Loki]

How did you get on today with your resit?