Prospective earth fault current

[Dambo]

Hi there, Am I right in saying that this is the maximum current that will flow in the case or negligible impedance between phase and earth?

 

[Markiemarque]

I think so.

PFC is:

Highest of either phase to neutral or phase to earth (short circuit). If 3 phase then Phase to neutral x 2.

Cheers

Mark

 

[Andy™]

Hi there, Am I right in saying that this is the maximum current that will flow in the case or negligible impedance between phase and earth?

correct. this can be as low as a few amps for TT, or many hundreds of amps for TN.

generally, phase-neutral is higher than phase-earth (lower loop), and phase-phase is even higher (higher voltage)

 

[Dambo]

[quote name='Andy

 

[Andy™]

Ze is earth loop impedance. you can use this to work out PEFC, but many testers can also test & give a reading as amps or KA

 

[Dambo]

[quote name='Andy

 

[m4tty]

Both the same matey i think

 

[Dambo]

Cheers m4tty. Sometimes I think I go out of my way to confuse myself!

 

[NozSpark]

Don't confuse PEFC with PFC or PSCC

PEFC - prospective earth fault current (L-E)

PSCC - prospective short circuit current (L-N)

PFC - highest of the above

 

[Dambo]

Don't confuse PEFC with PFC or PSCCPEFC - prospective earth fault current (L-E)

PSCC - prospective short circuit current (L-N)

PFC - highest of the above

Is the equation for PEFC: If = Uo / Zs?

 

[NozSpark]

No.. its

If=Uo/Zdb

 

[Dambo]

No.. itsIf=Uo/Zdb

What does the db stand for?

 

[NozSpark]

It's the DB's earth loop impedance, but with the bonds attached

 

[Mark2spark]

So, in the case of a DB2, isn't that effectively the Zs then mate?

 

[Lurch]

So, in the case of a DB2, isn't that effectively the Zs then mate?

Zs = Zdb when the DB is not connected directly to the origin of the supply.

 

[mpspark]

Thanks for clarifying this. It can be confusing at first for us newbies!