Cable Calc Template.

[Guest123]

Evening all.

This has been in the arms for a while now and I meant to post it in the open forums ages ago but totally forgot.

It's the design template I created when I did my C&G 2400 design course (C&G 2391-20 in todays money). I have tweaked it a bit to update it, regs references etc but the fundamentals haven't changed at all.


Hope you find it useful.

:cyclist:

 

[silva.foxx]

Thanks Lenny.

It would be really handy as a spreadsheet :wink_smile:

 

[Guest123]

Thanks Lenny.

It would be really handy as a spreadsheet :wink_smile:

Funny you should mention that.

I started one, ages ago with hyperlinks to actual regs pages etc, and never have got round to finishing it. Who knows, maybe one day.........got this HNC thingy robbing me of all my spare time at the mo though.:smart:

 

[i=p/u]

always looked for one of these when didnt quite grasp it all... whats point 7 all about, would you max zs from circuit breaker??? cheers will save it anyway and print and pass on too i think appropriate

 

[Guest123]

always looked for one of these when didnt quite grasp it all... whats point 7 all about, would you max zs from circuit breaker??? cheers will save it anyway and print and pass on too i think appropriate

Point 7 is calculating wether or not the CPC would be large enough to cope with the magnitude of earth fault current that may flow under fault conditions, using the adiabatic equation.

 

[i=p/u]

so you would use, the breaker device max zs for the sum...... would you multiply by 0.8 before you find your fault current??? )

 

[johnboy6083]

no mate you wouldnt, asitsthe max fault current you are looking for, to ascertain if your protective devices have sufficient breaking capacity to contain the fault.

 

[i=p/u]

ok so point 7 is very clear in saying, thermal constraints i.e breaking capicty for that point ic circuit... i thought when done at the origin and devices selected along with this it would cover downstream ones as got less fault current....

but i think i know you still need to check when out in industry , where im on about domestic lol

 

[johnboy6083]

what your talking abput mate is called cascading, or back-up protection. It is permitted in industry too.

what usually happens is that you have a main board, that will be weither MCCB's or fuses, this will then feed smaller panelboards, or large machines. The panleboards will have MCCB's or fuses, and then your final ccts will be fed from a 3phDB that will be on MCB's.
this is because its very difficult to acheive discrimination with MCB'as feeding MCB's, but easier to use fuse's or MCCB;s to feed MCB's.

you will then in all likelyhood, if using large cables to feed you final 3ph DB, be using the MCCB or fuse on the feed as backup protection for short circuit and/or earth fault protection.

 

[i=p/u]

yes great page for someone like myself with ahaqlf a clue... black and white

 

[i=p/u]

i do think it should say at point 7 , Uo /Ze.... but im sure there is perfectly good reasn why... dont mind me

 

[Guest123]

i do think it should say at point 7 , Uo /Ze.... but im sure there is perfectly good reasn why... dont mind me

I suggest you investigate exactly what the adiabatic equation is and how it used in circuit design.

 

[i=p/u]

so does that mean you would use the max zs reading of the breaker for the design???? sorry

 

[i=p/u]

sorry at first point

 

[dingledong]

hmm i cant get it to open:ninja: