Submain swa size check

[bigspark17]

Just after a bit of advice from thoose of you that deal with this regularly & want to make sure i get it right.

Swa submain to phone network mast
63Amp single phase supply
Pme supply assumed ze of 0.35
245M run

Ive been trying to calculate which size swa & cpc or 3c swa to go for, would like any experienced input.
Thanks

 

[Ian1981]

What is your protective device ?
Fuse, mccb , mcb etc?
Also installation method
May restrict your calculations as your max zs will hinder you as I would imagine your ze will probably be less than 0.35
As an example a type c 63 amp mcb has a max zs of 0.34 ohms without your 80% rule of thumb.

 

[Leesparkykent]

Ze is a major factor. Any chance you can site survey and measure it?

 

[bigspark17]

What is your protective device ?
Fuse, mccb , mcb etc?
Also installation method
May restrict your calculations as your max zs will hinder you as I would imagine your ze will probably be less than 0.35
As an example a type c 63 amp mcb has a max zs of 0.34 ohms without your 80% rule of thumb.

I was going to install switch fuse 63amp bs88.. install method is buried in ground with warning tape buried above.

Ze is a major factor. Any chance you can site survey and measure it?

Unfortunatly not as the DNO have not installed the supply into the customer built hut yet, :/

 

[bill01803]

It is unlikely to be TNCS in a hut more chance of TT

 

[Wilko]

As Bill has said above, there may be reasons to TT the installation instead of PME. The network guys (DNO and or mobile operator) should have detailed guidance for you, as its not exactly the first one. Anyway, see page 35 in this guide for some earthing info

https://library.ukpowernetworks.co....017+Customer+Installation+Earthing+Design.pdf

 

[Leesparkykent]

Without knowing Ze your a little stuffed...If there is no way of knowing then I would be looking at pricing to install a MCCB with adjustable earth leakage/fault protection.

 

[Ian1981]

It is unlikely to be TNCS in a hut more chance of TT

Why is that?
If it's a purpose built hut to house the metering and any distribution equipment why does it need to be TT?

 

[Ian1981]

 

[Ian1981]