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Neutral - Earth Link in Main Switchboard

Nick Parker
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. 


If the Neutral terminal of the transformer is grounded near the transformer and if it is interconnected with the other earth rods/bars? Is still neural - earth link to be provided at the Main switchboard?
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    Glibly, when there is not already a link somewhere else - there has to be at least one in the system for the ADS to work. - in TN-S and TT it is at the transformer, for TNC-s (PME) at each point where the TNC part becomes TN-s, that is at least at each building origin, usually.


    Also needed  if the feed from the transformer is a combined neutral and LV earth, in the manner of PNB.


    Also, often, but not always done at the board when there are multiple sources, such as pairs of private transformers, or private generators  to be combined - though in such cases where there are more than one  link the part  of the earthing between links needs to be sized for carrying the neutral current too, depending which supply or supplies is active or may be active in combination, and at least in the UK, this is carefully regulated, needing DNO or BNO involvement -ESCQR applies.


    In summary, there are quite a few situations - not sure which one you have in front ot you.
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  • 0
    Glibly, when there is not already a link somewhere else - there has to be at least one in the system for the ADS to work. - in TN-S and TT it is at the transformer, for TNC-s (PME) at each point where the TNC part becomes TN-s, that is at least at each building origin, usually.


    Also needed  if the feed from the transformer is a combined neutral and LV earth, in the manner of PNB.


    Also, often, but not always done at the board when there are multiple sources, such as pairs of private transformers, or private generators  to be combined - though in such cases where there are more than one  link the part  of the earthing between links needs to be sized for carrying the neutral current too, depending which supply or supplies is active or may be active in combination, and at least in the UK, this is carefully regulated, needing DNO or BNO involvement -ESCQR applies.


    In summary, there are quite a few situations - not sure which one you have in front ot you.
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