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?
I agree it probably goes against the intention of that regulation.
It's still out there, being driven across the dustier bits of the globe...
BS7671 is not written assuming that the supply could be derived from anything including things as rough as a pair of clips onto a bare overhead line, with some uncertainty about which core is which.
Power of opportunity brings a different set of risks and mitigations for which some of the standards assumptions are not so suitable, it does not mean you cant use the local electricity safely, you just have to plan for some odder cases - oh and never use any of the supply cables as earth.
You probably won't like my torch bulb NE as tell-tale indicator of lost neutral - if it lights up you have a bit of an NE offset problem if the filament has vaporised you have a big problem (or at least did have at some point since it was installed ).
I agree it probably goes against the intention of that regulation.
It's still out there, being driven across the dustier bits of the globe...
BS7671 is not written assuming that the supply could be derived from anything including things as rough as a pair of clips onto a bare overhead line, with some uncertainty about which core is which.
Power of opportunity brings a different set of risks and mitigations for which some of the standards assumptions are not so suitable, it does not mean you cant use the local electricity safely, you just have to plan for some odder cases - oh and never use any of the supply cables as earth.
You probably won't like my torch bulb NE as tell-tale indicator of lost neutral - if it lights up you have a bit of an NE offset problem if the filament has vaporised you have a big problem (or at least did have at some point since it was installed ).
