TN-S braiding

[Toneyz]

I don't get involved with a lot of properties that have a TN-S supply but had one today in an old local community theatre/centre had a MET with all sub-main earths etc going to it 16mm/10mm then abrade going from the sheath to the MET all standard and in good condition just looked to me a bit feeble compared with the 16/10mm copper conductors in the MET. does anyone know what it is made of and its CSA etc not realy given it much thought up till now.

 

[Gavin John Hyde]

Have wondered the same when the DNO fit a new sheath earth to repair an old broken one. At end of the day Dno take responsibility for it so havent worried too much.

 

[Bobster]

If you do the adiabatic equation, you can see just how small a CPC you actually require.

Being a TN-S supply, probably 4 - 6mm is all that is actually required. As long as it's not sat next door to the substation. The larger CPC's are most probably installed from the CU to keep the Zs down within circuits.

Always a good idea to give it a quick visual check though. Make sure it's not showing signs of heating etc...

 

[Midwest]

Seen a few steel braids going from sheath to MET. First time I saw one, I even asked DNO to inspect, as it wasn't something I'd seen before. They said it was normal practise for them.