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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
    AJJewsbury:

    I wonder how damaging short overvoltages (say a few seconds) are. Ordinary L-N (or L-PE on TN-C-S) faults on one phase will pull the N a long way towards the phase the fault is on, so consumers on other phases will see a much increased L-N voltage until the fault clears - which could easily be approaching 5s for faults withini consumers' installations, or even up to 60s for distribution network faults. I guess such problems must be relatively common - much more common than broken PENs etc - yet we don't have devices failing left right and centre.

       - Andy.


    That would be my thoughts..... With electronic devices in particular I would have thought that the damage would be done in a few cycles - much faster than any monitoring device could detect & fire a contactor or shunt trip.


    I can see that such a device would reduce the risk from prolonged over-voltage from a loss of neutral but I'm not convinced it be be any help in saving electronic appliances.


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  • 0
    AJJewsbury:

    I wonder how damaging short overvoltages (say a few seconds) are. Ordinary L-N (or L-PE on TN-C-S) faults on one phase will pull the N a long way towards the phase the fault is on, so consumers on other phases will see a much increased L-N voltage until the fault clears - which could easily be approaching 5s for faults withini consumers' installations, or even up to 60s for distribution network faults. I guess such problems must be relatively common - much more common than broken PENs etc - yet we don't have devices failing left right and centre.

       - Andy.


    That would be my thoughts..... With electronic devices in particular I would have thought that the damage would be done in a few cycles - much faster than any monitoring device could detect & fire a contactor or shunt trip.


    I can see that such a device would reduce the risk from prolonged over-voltage from a loss of neutral but I'm not convinced it be be any help in saving electronic appliances.


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