PFC & PSC

[downundersparky]

Hi Iam a mature apprentice in Western Australia and Iam struggling with PFC & PSC can any one help me pls, I have been told by a guy from the UK this is the site to be on.

Regards Downundersparky.

 

[steptoe]

welcome downunder

PFC = Prospective Fault Current

PSC/PSCC = Prospective Short Circuit Current

PSC/PSCC is measured across LINE & NEUTRAL

PFC is measured across LINE & NEUTRAL and again across LINE & EARTH (or GROUND, depending on terminology) , PFC is then recorded as the greater figure between the 3 figures, PFC and both of the PSCC readings.

HTH,

 

[downundersparky]

welcome downunderPFC = Prospective Fault Current

PSC/PSCC = Prospective Short Circuit Current

PSC/PSCC is measured across LINE & NEUTRAL

PFC is measured across LINE & NEUTRAL and again across LINE & EARTH (or GROUND, depending on terminology) , PFC is then recorded as the greater figure between the 3 figures, PFC and both of the PSCC readings.

HTH,

Thanks Steptoe, but I was after the for formula !!! I just can`t seem to get it in my head for some reason !!!!!. :coat :coat:coat:coat:coat:coat:coat:coat:coat

 

[kerching]

G'day,

We are a tad recalcitrant in givng straight answers on here, not that we are awkward [well some are but He knows who He is]

Basic Physics, so if you shorted out line to neutral, then the current flowing would be proportional to the Voltage and inversely proportional to the impedance...if you see what I mean?................ :coat

nb...obviously shorting out L-N is not classed as a good move under any circumstances and should not be attempted

 

[downundersparky]

Ta for that, my question is how I work it out.

Uo/ ???? or ?????. I just can`t seem to figure it out I know I appear thick but I just cannt get it.

 

[steptoe]

you need to measure the impedance

 

[downundersparky]

Thanks Steptoe, Z at the submain/PA or both added toghether ??

If I have impedences of,

Z1 transformer imp 0.01591

Z2 Consumer mains 0.0037 3

Z3 submains to DB 0.026

I think AMP=Z1+Z2+Z3/ is it sph or 3ph after this I loose the will to live !!!!!.

 

[kerching]

you need to measure the impedance

But FFS don't do it with an Ohm meter, otherwise your relatives will be having 30 minutes with the Vicar and a very limp handshake.

You need to get hold of an Earth Loop Impedance Tester...you can borrow mine if you pay me to deliver it and my return fare. In fact I will even test it for you for free if you do that!!!...............always helpful on here!........... :coat

 

[downundersparky]

Thanks Kerching, do you mind if I fly you via Thailand for a 2 week stop over 1st ????.

 

[steptoe]

Thanks Steptoe, Z at the submain/PA or both added toghether ??If I have impedences of,

Z1 transformer imp 0.01591

Z2 Consumer mains 0.0037 3

Z3 submains to DB 0.026

I think AMP=Z1+Z2+Z3/ is it sph or 3ph after this I loose the will to live !!!!!.

impedance at the point you wish to calculate PFC for.

obviously PFC will[should] be higher the closer you are to the Tx.

 

[johninlondon1]

A Prospective short circuit current is the maximum current that could flow between line and neutral on a single phase supply or between line conductors on a three phase supply.

A prospective earth fault current is the maximum current that could flow between live conductors and earth.

The value of whichever is the highest, will be your PFC. the highest value of PFC will be closest to the origin of the supply, as that is where the impedence is at its lowest value.

PSCC = U/Ze

eg. on 230v system with a Ze of 0.30 Ohm, calculation would be 230/0.3 = 766.66 Amps or 0.76 K/Amps.

 

[brav]

A Prospective short circuit current is the maximum current that could flow between line and neutral on a single phase supply or between line conductors on a three phase supply.A prospective earth fault current is the maximum current that could flow between live conductors and earth.

The value of whichever is the highest, will be your PFC. the highest value of PFC will be closest to the origin of the supply, as that is where the impedence is at its lowest value.

PSCC = U/Ze

eg. on 230v system with a Ze of 0.30 Ohm, calculation would be 230/0.3 = 766.66 Amps or 0.76 K/Amps.

Wouldnt it be U/Zs, as the earthing conductor is connected?

 

[steptoe]

Wouldnt it be U/Zs, as the earthing conductor is connected?

why would the earthing conductor be connected?

I think the clue is in the fact of measuring Ze.

headbang

 

[brav]

why would the earthing conductor be connected?I think the clue is in the fact of measuring Ze.

headbang

To find the highest pfc all parallel earth paths must be in place to get the lowest impedence ohm reading and the highest amp reading/calculation? Ze is taken with the earthing conductor disconnected, Zs at a Distribution board or Consumer Unit, where the protective device would be, is done with the earthing conductor connected to get pfc

 

[steptoe]

thats all well and good at a sub,

how would that differ from a new install I wonder?>?>?>?>?>?>