Calculate the appropriate size of the protective conductor exam question

James2249 · Jan 24, 2024

fault = 400 A
Operating time of protective conductor = 0.15 s
Constant k, for the material of the conductor = 134

a 1.5mm
b 2.5mm
c 4.0mm
d 6.0mm

Just want to make sure I've got this right,

nicebutdim · Jan 24, 2024

It would be best to post your answer along with working out. People aren't going to hand out answers for this sort of thing, but will check your work and offer guidance where necessary.

westward10 · Jan 24, 2024

What is the full question but as above what are your workings?

James2249 · Jan 24, 2024

nicebutdim said:
It would be best to post your answer along with working out. People aren't going to hand out answers for this sort of thing, but will check your work and offer guidance where

Sorry, it’s been bugging me most of the night.

James2249 · Jan 24, 2024

I think it’s wrong

Julie. · Jan 25, 2024

These are often difficult questions, because although your calculation is correct - leading to the answer 1.5mm^2 there are sometimes related regulations.

So if the question relates to final circuits etc (I.e. twin & earth or whatever), this would be correct.

However, if the question relates to other areas, there are minimum conductor sizes - depending upon if the conductor is protected or not.

On face value, I would assume 1.5mm^2

Examiners tend to have a specific situation in mind when they write questions, which often isn't clearly presented

James2249 · Jan 25, 2024

Julie. said:
These are often difficult questions, because although your calculation is correct - leading to the answer 1.5mm^2 there are sometimes related regulations.

So if the question relates to final circuits etc (I.e. twin & earth or whatever), this would be correct.

However, if the question relates to other areas, there are minimum conductor sizes - depending upon if the conductor is protected or not.

On face value, I would assume 1.5mm^2

Examiners tend to have a specific situation in mind when they write questions, which often isn't clearly presented

Thank you so much for your help

much appreciated

Julie. said:
These are often difficult questions, because although your calculation is correct - leading to the answer 1.5mm^2 there are sometimes related regulations.

So if the question relates to final circuits etc (I.e. twin & earth or whatever), this would be correct.

However, if the question relates to other areas, there are minimum conductor sizes - depending upon if the conductor is protected or not.

On face value, I would assume 1.5mm^2

Examiners tend to have a specific situation in mind when they write questions, which often isn't clearly presented

thank you so much for your help, much appreciated