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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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    Andy is correct - SPD is not a solution for this - and it happens regardless of PEN failure or not, if the Neutral is lost say in a TN-S or TT system (say damaged overhead), the same thing can happen to loads.


    There are relay solutions for this (unvervoltage/overvoltage/phase loss/neutral loss), but the get the correct reliability of products is the challenge. Larger installations that have an intelligent breaker system in the primary switchboard can be better protected.


    OF course, whatever you choose, supplies to safety services should be considered for separate protection.
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    Andy is correct - SPD is not a solution for this - and it happens regardless of PEN failure or not, if the Neutral is lost say in a TN-S or TT system (say damaged overhead), the same thing can happen to loads.


    There are relay solutions for this (unvervoltage/overvoltage/phase loss/neutral loss), but the get the correct reliability of products is the challenge. Larger installations that have an intelligent breaker system in the primary switchboard can be better protected.


    OF course, whatever you choose, supplies to safety services should be considered for separate protection.
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