submain testing.

[sime27]

When filling out a EIC i always use a seprate SCHEDULE OF TEST RESULTS for any submains feeding seprate CU.
but what should i put for Ze and PFC at the top ?

 

[ricicle]

The Ze and PFC are measured at the incoming terminals of your sub main board and so should go at the top of your sheet for that board.

 

[sime27]

is this the way everbodys does it ???

 

[industryspark]

Its the way it should be done. the Ze becomes Zdb (distribution board) if you like.

 

[sime27]

would this be done in the normal way as you do at main incoming supply i.e would you remove the incoming earth feed to the db ?

and whille your on could to tell me the formular for calculating PFC at a db?

 

[ricicle]

would this be done in the normal way as you do at main incoming supply i.e would you remove the incoming earth feed to the db ?

and whille your on could to tell me the formular for calculating PFC at a db?

If it is practical to do so then yes measure on the earth wire disconnected.
Why are you asking these questions if you are carrying out this work.If you have to ask then you are not competant.
If your tester will not measure PFC then basic ohms law tells you how to come by PFC if you have the Ze

 

[sime27]

im in my 3rd session of 2391 and we aint covered allot of the maths so would appreciate if some1 could tell me the formula

 

[comms]

im in my 3rd session of 2391 and we aint covered allot of the maths so would appreciate if some1 could tell me the formula

I=v/r
I=240/Ze
or in your case
I==240/Zdb

 

[DESL]

im in my 3rd session of 2391 and we aint covered allot of the maths so would appreciate if some1 could tell me the formula

Oh boy - you mean you don't know OHM's Law - it's all you need!!

 

[ricicle]

Don't forget to double your SP PFC for worst case scenario 3 phase PFC (if your working on 3 phase)

 

[plugwash]

Don't forget to double your SP PFC for worst case scenario 3 phase PFC (if your working on 3 phase)

don't forget that that figure is just a relatively conservative estimate of the 3 phase PFC but it is *NOT* a worst case.

in particular a bad neutral could easilly make your single phase PFC very low but would have no affect whatsoever on the phase-phase PFC.

 

[Spark123]

Just to clarify the terminology, the PEFC (prospective earth fault current) is the largest figure for the phase to earth fault current, this is the figure that can be derived from the supply voltage divided by Ze. The PSCC (prospective short circuit current) is the largest live-live fault current (wether it be phase-neutral or phase-phase). Some EFLI testers require both the earth and the neutral test probes to be connected to the neutral conductor to measure PSCC - see the specific instrument for details. Like has been said if the tester cannot handle phase-phase voltage the largest phase-neutral value should be taken and doubled.
The PFC is the value which is the larger of the PSCC or the PEFC. In a 3phase system it is most likely the phase-phase.

 

[ricicle]

Don't forget to double your SP PFC for worst case scenario 3 phase PFC (if your working on 3 phase)

don't forget that that figure is just a relatively conservative estimate of the 3 phase PFC but it is *NOT* a worst case.

in particular a bad neutral could easilly make your single phase PFC very low but would have no affect whatsoever on the phase-phase PFC.

Yes, but if your tester will not test phase to phase PFC you can only make the assumption it will be twice the single phase PFC and you would have no way of knowing if you have a bad neutral.You would just have to assume either 2x P/N PFC or 2x P/E PFC whichever was the higher