Neutral - Earth Link in Main Switchboard

When is an earth neutral link required in an main switchboard? Is it particular to the earthing system?


Is it common to earth the source neutral at the first point in the LV system where the neutral is terminated - the main LV switchboard.

In general there's exactly one N-PE link in an TN-S system - it'll only appear at the main swicthboard if there isn't one at the transformer. (The text books often seem to assume it's always at the transformer, but it's often convenient in practice to have it at the switchboard when using a private transformer, especially if the HV and LV earths are separated).


The same basic principle applies with TN-C-S systems but the link is sort of "stretched" along the length of the CNE (or PEN) conductor - earthed at the source end and N/PE split at the consumer end(s).


Likewise TT systems will have the N earthed at one point only (again possibly 'stretched' along a CNE if the system also supplies TN-C-S installations).


In the UK we never "re-earth" a true N - as I understand is traditional in the US and similar (although of course a CNE can be earthed multiple times along its length).


   - Andy.

When is an earth neutral link required in an main switchboard? Is it particular to the earthing system?


Is it common to earth the source neutral at the first point in the LV system where the neutral is terminated - the main LV switchboard.

In general there's exactly one N-PE link in an TN-S system - it'll only appear at the main swicthboard if there isn't one at the transformer. (The text books often seem to assume it's always at the transformer, but it's often convenient in practice to have it at the switchboard when using a private transformer, especially if the HV and LV earths are separated).


The same basic principle applies with TN-C-S systems but the link is sort of "stretched" along the length of the CNE (or PEN) conductor - earthed at the source end and N/PE split at the consumer end(s).


Likewise TT systems will have the N earthed at one point only (again possibly 'stretched' along a CNE if the system also supplies TN-C-S installations).


In the UK we never "re-earth" a true N - as I understand is traditional in the US and similar (although of course a CNE can be earthed multiple times along its length).


   - Andy.