what is the formula for calculating PSCC for final circuits?

[WilliamAtkin]

hi in college and watched some YouTube videos and read up on things I think I got the right formula but I'm not sure.

Zsc= Zesc(or Zdbsc) + (R1+RN)
(R1+RN) = milli ohms/metre x length x correction factor and then divide that by 1000
Zesc = Uo divided by PFC
Then add together Zesc and (R1+RN)
Then Isc = Uo divided by Zsc

But the fact that my formula says Isc (short circuit current) at the end and not PSCC makes me thing it could be a slightly different formula and i dont want to do all the work to be told its the wrong formula

Ive done one circuit so far so i will give an example
Single core 1mm cables
(R1+RN) = 36.20 x 29.25m x 1.04 =1101.204 and then divide this by 1000 gives me 1.101204 ohms
PFC is 3.7kA or 3700A
Zdbsc = 230v divided by 3700A which = 0.0621
soZsc = Zdbsc + (R1+R2) = 1.101204 + 0.0621 = 1.163304 and this to 2 decimal places is 1.16 ohms
Isc = Uo divided by Zsc which = 230v divided by 1.16 ohms which = 198.27586... and this to 2 decimal places = 198.28A
And 198.28A is 0.19828kA and that to 2 decimal places is 0.20kA
0.20kA is my final answer but is that just the short circuit current and if so is that the same as the prospective short circuit current or have I indeed got the wrong formula

 

[davesparks]

But the fact that my formula says Isc (short circuit current) at the end and not PSCC makes me thing it could be a slightly different formula and i dont want to do all the work to be told its the wrong formula

What does PSCC stand for?

 

[Petej999]

What does PSCC stand for?

PROSTECTIVE SHORT CIRCUIT CURRENT

 

[WilliamAtkin]

What does PSCC stand for?

Prospective Short Circuit Current
I looked up the exact meaning of prospective as I admit I didn't know what the word meant individually and with a quick google I got the definition- "expected or expecting to be the specified thing in the future" so i gathered that PSCC is the expected short circuit current and I think the formula I'm using is the short circuit current but that might just be the PSCC formula and I could be overthinking it I don't know. The question I'm on in my design project is to select a suitable range of protective devices for the project and it states " Your selection should be based on the following:
- Prospective Short Circuit Currents
-Requirements for additional protection "
So I though the 1st thing for me to do is work out the PSCC for each final circuit .
The PFC is stated in the spec which is 3.7kA and I used this in the formula.
And I know my circuit breakers need have a short circuit rating equal to or higher than 3.7kA
And I know what current rating my breakers will be from my In results in my cable calcs

 

[davesparks]

PROSTECTIVE SHORT CIRCUIT CURRENT

No need to shout dear.

The point of my question, which I thought was obvious, was to get the trainee to think about that question they are asking and work out the answer for themselves.

 

[Petej999]

No need to shout dear.

The point of my question, which I thought was obvious, was to get the trainee to think about that question they are asking and work out the answer for themselves.

try telling my wife that Dave. i get used to shouting just to get myself heard. SORRY MATE

 

[davesparks]

try telling my wife that Dave. i get used to shouting just to get myself heard. SORRY MATE

Your wife is irrelevant, save that for the general forum.

This is the trainee forum, if you cannot treat the trainees with respect and courtesy then keep the hell out of it.

Trainees are the future of this trade, if you cannot treat them witn a modicum of respect then stay quiet and leave it to those of us who do have some respect for trainees and can converse with them without resorting to shouting.