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?
But rather than adding an extra device to monitor the supply voltage (along with a contactor which would presumably have to draw power almost all the time), the obvious solution would be program an existing piece of equipment that already measures L-N voltage and has an in-built contact capable of disconnecting the installation - i.e. a smart meter. While it was at it, it could also directly inform the DNO/supplier of network problems which may require some intervention. It even sits rather well theologically as the supply industry is then responsible for ensuring that the supply is within safe limits, rather than the consumer.
But rather than adding an extra device to monitor the supply voltage (along with a contactor which would presumably have to draw power almost all the time), the obvious solution would be program an existing piece of equipment that already measures L-N voltage and has an in-built contact capable of disconnecting the installation - i.e. a smart meter. While it was at it, it could also directly inform the DNO/supplier of network problems which may require some intervention. It even sits rather well theologically as the supply industry is then responsible for ensuring that the supply is within safe limits, rather than the consumer.
