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Loss of neutral

lyledunn
I have just been involved in a situation where temporary loss of neutral on a TNCS system caused thousands of pounds worth of damage. It seems this loss of neutral situation, either within or outside the installation, is occurring more frequently. SPDs are now commonly fitted but at DBS  and generally with a Up in the order of 860v, so giving no protection on loss of neutral in a three-phase and neutral system. Cost benefit analysis across the national spectrum might not support a compulsion but is it time designers should be raising the issue with clients and at least offering a solution. On the other hand, is there a packaged solution?
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  • 0
    Hi gkenyon


    Mapj1  Tells a solution which at first seems like it only has positives to it.


    I was thinking of single phase TNCS with the earth side of the Caps Linked to a separate earth rod. because

    1. the system earth rod voltage would rise to dangerous levels

    2  the capacitors would then make zero contribution to any earth leakage currents in system under normal or fault conditions.

    ,

    Can you think of significant negatives or do you know why...

     
    531.3.1.202 It is not permissible to introduce an external connection for the purpose of intentionally creating a residual current to trip an RCD.


    Was added in?  

    Perhaps they had more "Heath Robinson" contraptions in mind?

Reply
  • 0
    Hi gkenyon


    Mapj1  Tells a solution which at first seems like it only has positives to it.


    I was thinking of single phase TNCS with the earth side of the Caps Linked to a separate earth rod. because

    1. the system earth rod voltage would rise to dangerous levels

    2  the capacitors would then make zero contribution to any earth leakage currents in system under normal or fault conditions.

    ,

    Can you think of significant negatives or do you know why...

     
    531.3.1.202 It is not permissible to introduce an external connection for the purpose of intentionally creating a residual current to trip an RCD.


    Was added in?  

    Perhaps they had more "Heath Robinson" contraptions in mind?

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