TN-C-S Earthing - Page 1
Forum section: electronics / general

author: Ralphy007
author_rank: Contributor
timestamp: June 10, 2021, 02:03:50 pm
content: Apparently with TN-C-S earthing it is important that the neutral is kept at earth potential by earthing it at many points along its length. If this is not done, a fault to neutral in one installation could cause a shock risk in all other installations connected to that system.Need help with this as I dont understand it - any material, drawings, references would be most welcome.

author: f4eru
author_rank: Super Contributor
timestamp: June 10, 2021, 02:59:01 pm
content: Please consult the rules that apply to your location.As far as I (mis)understood from UK rules, TN-C-S applies to inside buildings, and all the metal pipework etc has to be connected.Outside is difficult because the PE can become a danger in case of PEN failure, so it seems there has to be a solution at that point like PE voltage check, and/or local different earthing scheme like TT, or similar...

author: HB9EVI
author_rank: Frequent Contributor
timestamp: June 10, 2021, 03:23:43 pm
content: Quote from: Ralphy007 on June 10, 2021, 02:03:50 pmthere may apply local rules; but according to swiss installation rules the neutral is grounded at one single point only, this normally in the installation cabinet where the local grounding and the neutral from the public network are connected together - everything after this point PE and N are strictly separated, otherwise you inhibit the proper function of the RCD.In old installations there has to be watched out, that no sockets are PE and N together (klassische Nullung), what was common practice in the 1970th; usually that becomes a problem, when new installations are done which require the installation of a RCD; for proper function there has to be installed the PE wire to all sockets and all PE-N-connections have to be lifted.

author: themadhippy
author_rank: Super Contributor
timestamp: June 10, 2021, 03:37:42 pm
content: this might help, about 10 minutes

author: Alti
author_rank: Frequent Contributor
timestamp: June 21, 2021, 10:59:05 pm
content: Quote from: Ralphy007 on June 10, 2021, 02:03:50 pmI think you misunderstood what neutral conductor is. You must not ground neutral conductor. If you short PE (protective earth) and N (neutral) then this should be treated as a violation of electrical code, in any distribution system.I think what you meant is that there is a PEN conductor distributed (such earthing system is called TN-C, there is no N or PE conductor there) and PEN conductor is split into protective earth PE and neutral N. From this point it is called TN-S and whole earthing system is called TN-C-S, both PE and N conductors run separately.It does happen some old installations have TN-C earthing systems distributed at homes. This is TN-C, not TN-C-S, and you cannot have fault to neutral there simply because there is no neutral.So, "fault to neutral" as you describe can only happen when you actually have neutral. Now, in single phase distribution system (like TN-C-S in UK homes) damaging neutral is not a safety issue, you can chop it anywhere and nothing is going to happen. However, damaging neutral in two/three phase systems is called "lost neutral" or "floating neutral" and leads to some rather expensive and unpleasant fireworks but I would not call it a "shock risk".