25-06-2020, 04:49 PM
In the UK we have a mix of TT (you provide your own earth rod, mainly for those with overhead supplies), TNS (earth supplied via sheath of cable, connected to neutral at substation, common in older areas) and TNC-S, aka PME (neutral earthed in many places, earth conencted to neutral at main intake, usual for newer supplies) You are always free to ignore the supplied earth terminal and use TT.
Neutral is always earthed at the substation in most countries.
Ring mains (correctly ring final circuits) are unrelated to earthing method. They are now deprecated for new UK instals. 20A radial with 2.5mm or 32A radial with 4mm cable are now the preferred circuits for sockets.
Some premises, notably petrol stations and farm buildings, aren't allowed to use PME. The risk of a fault causing neutral to rise too far above true earth is too high.
I've had to remove VIR (rubber insulated) cables that have gone either gooey or crumbly. Also lead outer with rubber inner. This was the deluxe option before WW2. Some was perfect. In other cases the rubber fails as with VIR. Used with nice junction boxes where clamps over the lead gave earth continuity.
Neutral is always earthed at the substation in most countries.
Ring mains (correctly ring final circuits) are unrelated to earthing method. They are now deprecated for new UK instals. 20A radial with 2.5mm or 32A radial with 4mm cable are now the preferred circuits for sockets.
Some premises, notably petrol stations and farm buildings, aren't allowed to use PME. The risk of a fault causing neutral to rise too far above true earth is too high.
I've had to remove VIR (rubber insulated) cables that have gone either gooey or crumbly. Also lead outer with rubber inner. This was the deluxe option before WW2. Some was perfect. In other cases the rubber fails as with VIR. Used with nice junction boxes where clamps over the lead gave earth continuity.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
