Earth fault loop impedance - textbook values vs BS7671

[Gary Tollison]

Hello.
I'm in the final stages of completing my electrician course, and I find myself confused (again) by EFLI.

In the textbook provided is this:

Uo 230V
see below for each circuit.

Calculate the maximum Zs for each circuit:
Complete the table.

The answers given in the textbook are said to be correct.

However, according to BS7671, the values in the textbook exceed the maximum allowed Zs.

Eg: For the outbuilding circuit, BS7671 states type B 20A has max Zs of 2.19 ohms, yet the book says the correct answer is 2.30 ohms?

Am I missing something here?
Please can anyone help with this?
Thanks,
Gary

 

[Gary Tollison]

Ok, issue sorted.
According to the tutors, the answers in textbook are prior to amendment 3 and even though the version textbook was printed”after” amendment 3, somehow it didn’t get updated too.

So after applying Cmin factor 0.95, it brought the answers down to where they should be!

 

[Wilko]

Great work - a self answered question !
Now, what would be the max measured value?

 

[telectrix]

even before amd 3 and Cmin. ( which is to allow for supply volts down to 218V ), correction factor for cable temperature was to allow for temp. to be 70 deg.C, i.e . a factor of 0.8. applied to the BS7671 tabulated figures.

 

[Risteard]

They have left out the correction factor Cmin.