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?
So, taking this discussion in a slightly different direction....
What would be the general consensus/opinion about using a 4 pole REC isolator to disconnect (for a single phase domestic installation) the phase, neutral & also disconnect the water & gas bonds away from the network earth/neutral conductor? I'm thinking perhaps use two of two of the poles to switch two 25mm^2 conductors connecting the MET to the network earth/neutral to give some redundancy against a failed switch contact.
Over to the floor....
Removing the main bonding won't achieve anything at all in an installation with internal conductive service pipes. The pipes throughout the installation would still import PEN voltage from other installations.
In addition, even if adjacent consumers had the same protective provision, metal service pipes "in the street" could still pick up risen PEN voltage from the street.
I think it would be better for the SMART meter system to alert the DNO to the fact they may have a problem in a particular area so they can investigate. In a single-phase installation, the meter won't know whether it's a supply line conductor issue, supply transformer or tap issue, or a broken PEN conductor, but the DNO can build up a picture based on the voltages reported by meters from single phase installations on different phases, to determine which of these it might be.
So, taking this discussion in a slightly different direction....
What would be the general consensus/opinion about using a 4 pole REC isolator to disconnect (for a single phase domestic installation) the phase, neutral & also disconnect the water & gas bonds away from the network earth/neutral conductor? I'm thinking perhaps use two of two of the poles to switch two 25mm^2 conductors connecting the MET to the network earth/neutral to give some redundancy against a failed switch contact.
Over to the floor....
Removing the main bonding won't achieve anything at all in an installation with internal conductive service pipes. The pipes throughout the installation would still import PEN voltage from other installations.
In addition, even if adjacent consumers had the same protective provision, metal service pipes "in the street" could still pick up risen PEN voltage from the street.
I think it would be better for the SMART meter system to alert the DNO to the fact they may have a problem in a particular area so they can investigate. In a single-phase installation, the meter won't know whether it's a supply line conductor issue, supply transformer or tap issue, or a broken PEN conductor, but the DNO can build up a picture based on the voltages reported by meters from single phase installations on different phases, to determine which of these it might be.
