Cable calculation exercise

[CristiP]

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

 

[MJPD29]

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]

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]

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]

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

 

[MJPD29]

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]

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.