What Is The Purpose of Measuring Prospective Fault Current - PFC?

[Bane]

Is it so the correct size (kA rating) breakers can be installed?

 

[m4tty]

Think he meant prospective fault current not power factor correction mate lol

I believe it's to ensure the cpd can break the fault current safely. Maybe other reasons but that springs to mind. Cheers

 

[Ali]

Hmmm,

Do we need an explanation of PFC?

I suspect Bane means prospective fault current and Johninlondon1 means power factor correction!

 

[Sidewinder]

Its the ratio of useful power compared to actual power, if the percentage is too low, then you can end up paying more for yur electricity. Local electrical supply companys insist on consumers using as high as possible power factor as possible and may insist on upgrades to your electricity supply. One way of improving is to use a capacitor. A low power factor can cause damage to your equipment and also can deteriate the cables as higher currents are in the cables.

john,

sorry mate don't see how your explanation has anything to do with prospective fault currents?...

 

[Bane]

Sorry! Prospective Fault Current.

Thanks anyway JohnInLondon!

 

[Sidewinder]

No Canoey, I don't, do you need an explanation of RTFQ!

Quite how kA & power factor correction relate I don't quite figure in the context of the OP!!!

 

[Bane]

Sorry to break up the domestic here guys!

To steer the thread back on track...

Is Prospective Fault Current measured so the correct size (kA rating) breakers can be installed?

 

[Sidewinder]

Bane,

HOW DARE YOU!

You can't just go steering threads back ontrack willy nilly round here you know! ; )

Yes it is one reason!

 

[sprocketflup]

Sorry to break up the domestic here guys!To steer the thread back on track...

Is Prospective Fault Current measured so the correct size (kA rating) breakers can be installed?

Lol doesnt look like anyonme knows!

I thought it was for the reason youve stated meself, tho Ive had some where it looks like the PFc and Ze have swapped places

I used to come round here when it was all fieldsssss etc etc

 

[Bane]

Hallelujah!!!!

Cheers SideWinder! Much appreciated!

Thank you everyone else who took the time to reply too!

 

[spinlondon]

PFC is also be used when sizing earth conductors, if using the adiabatic equation.

 

[Bane]

Ah!!!

Of course it is!

Just covered that SpinLondon!

Thank you verily!

 

[binky]

Main purpose is to check main protective device for installation ie DNOs fuse is capable of withstanding dead short circuit current, though in reality the likelyhood of dead short generating such an high ampage is unlikely unles it occurrs at 1mm from fuse so as to mimmise resistance. I did for many years believe that for example a 10K PFC would mean that 6K MCBs would not be suitable, this however is wrong ( I have discussed it my assessor) as again unless dead short occurs within CU (highly unlikely) they would never see min rersitance needed, and there are resistances down Meter tails and within main switch / busbars / MCB connections which are still sufficient to seriously drop ampage of dead short. Likewise if dead short happened 1mm from MCB, there is only that MCBs ampage going down circuit anyway. I shall now let argument commence for those that can be arsed to calculate numbers opcorn

Sorry to drag thread back to question

Perhaps we should have a new section for threads that go seriously off topic, which is very amusing though also annoying when in a hurry ?:|

 

[Bane]

Main purpose is to check main protective device for installation ie DNOs fuse is capable of withstanding dead short circuit current, though in reality the likelyhood of dead short generating such an high ampage is unlikely unles it occurrs at 1mm from fuse so as to mimmise resistance. I did for many years believe that for example a 10K PFC would mean that 6K MCBs would not be suitable, this however is wrong ( I have discussed it my assessor) as again unless dead short occurs within CU (highly unlikely) they would never see min rersitance needed, and there are resistances down Meter tails and within main switch / busbars / MCB connections which are still sufficient to seriously drop ampage of dead short. Likewise if dead short happened 1mm from MCB, there is only that MCBs ampage going down circuit anyway. I shall now let argument commence for those that can be arsed to calculate numbers opcorn Sorry to drag thread back to question

Perhaps we should have a new section for threads that go seriously off topic, which is very amusing though also annoying when in a hurry ?:|

And that was a very funny reply!

(Though you're showing off now with your explanation of PFC! Not that I don't appreciate it)

 

[spinlondon]

Increasing the CSA of meter tails, will increase PFC.

 

[ADS]

. Likewise if dead short happened 1mm from MCB, there is only that MCBs ampage going down circuit anyway.|

Not sure what 'ampage' is - but I can pretty much guarantee you that if you have a 'short circuit' at a distance of 1mm from any MCB, you will get pretty much the full 'PFC' flowing, not just the current flowing in that circuit.

 

[SPECIAL LOCATION]

What Is The Purpose of Measuring PFC?

So we can fill in the little box that says PFC of the certs!!!!!!

If you don't read it..

You can't fill it in!!!

Do they not teach younger training electricians to read books anymore...?

Try a bit of bedtime reading:-

Big Red BS7671

434.1 page 75 & 434.5.1, 434.5.2 page 76

Guidance note 3

2.7.16 page 52 through to page 54.

On Site Guide

7.2.7 page 56-57

and

10.3.7 page 88

Think those should help!

Guinness

 

[binky]

What Is The Purpose of Measuring PFC?So we can fill in the little box that says PFC of the certs!!!!!!

Yes

If you don't read it..

You can't fill it in!!!

Do they not teach younger training electricians to read books anymore...?

Try a bit of bedtime reading:-

Big Red BS7671

434.1 page 75 & 434.5.1, 434.5.2 page 76

Guidance note 3

2.7.16 page 52 through to page 54.

On Site Guide

7.2.7 page 56-57

and

10.3.7 page 88

Think those should help!

Guinness

Falling asleep already

 

[binky]

Some quick numbers based on I = V/R Given V = 230V then:-

for a resistance of 0.01 ohms I = 23000A - big bang

for a ressitance of 0.05 ohms I = 4600A - still V scary.

so as you can see even a tiny amount of resistance fails to generate the measured PFC hence we don't see exploded MCBs very often. ray

 

[ADS]

we don't see exploded MCBs very often. ray

You won't see them very often, anyway, because of the back-up protection provided by the cut-out fuse. - but I get your point.