Cable calculation exercise

CristiP · Dec 30, 2022

can anyone help me with this problem ? i don't understand it
ive triend to get involved in it but still i don't get it
thanks

[ElectriciansForums.net] Cable calculation exercise

MJPD29 · Dec 30, 2022

It sounds like you are being asked to calculate required values for the cable to determine whether it will be complaint or not, e.g. suitably sized cable meeting correct values for protective device etc, and I'd not complaint state why.

Lister1987 · Dec 30, 2022

CristiP said:
can anyone help me with this problem ? i don't understand it
ive triend to get involved in it but still i don't get it
thanksView attachment 104952

It's telling you to run the entire design calculation;

Coordination - Ib <= In <= Iz <= It
Volt Drop
Adiabatic Thermal Withstand
Ipf
Actual disconnection time.

And highlight if it fails at any point in the calculations and if it does; a suitable remedy.

CristiP · Dec 31, 2022

Lister1987 said:
It's telling you to run the entire design calculation;

Coordination - Ib <= In <= Iz <= It

Volt Drop

Adiabatic Thermal Withstand

Ipf

Actual disconnection time.

And highlight if it fails at any point in the calculations and if it does; a suitable remedy.

it is even less than ib , what should i do next ?

Electro-tech · Dec 31, 2022

This may be useful, also you can work out the Zs for the circuit to comply with the chosen OCProtection device impedance.

MJPD29 · Dec 31, 2022

Go over all your steps again and see where you've gone wrong or post your working out on here, we will help but not answer it for you

Lister1987 · Jan 1, 2023

CristiP said:
it is even less than ib , what should i do next ?

If you're having to ask, may I suggest Page 40 (blue) or Page 46 (brown) of BS7671, as if you don't understand the abbreviations and symbols then there's little point in going further.