The point of course is that the neutral is not really anything of the kind, as it is quite likley to be at a voltage no-where near earth, as the whole point of this sort of system is that you can ground one of the phases, and it carries on worrking. Variations on the IT theme used to be popular with DC on small ships and I believe for some electric train systems, so that first fault can be detected, without the supply being disconnected.
Indeed the earthing would somtimes be the centre of some warning lamps so that they all lit dimly, when all was well, and earth was in the centre of the live conductors, and when one side was faulted to earth, then one lamp or group of them would go out, and the remaing come on brighter, so show a fault state on one side. The problem with having a 'neutral' is that it is not sensible to fuse it, when it is at or near earth potential, but the whole ADS needs rethinking when either side could be live or not. Wiring so all cores are treated as live is a far safer way to operate - some odd applications like undersea power works this way for example, and often at odd voltages too, like 690 single phase for example. I understand that on ship AC 3 phase is often with "insulated neutral" , but we'd need someone like Ancient Mariner to confirm if that is true IT, though I fear we may have lost him in the forum move.
The point of course is that the neutral is not really anything of the kind, as it is quite likley to be at a voltage no-where near earth, as the whole point of this sort of system is that you can ground one of the phases, and it carries on worrking. Variations on the IT theme used to be popular with DC on small ships and I believe for some electric train systems, so that first fault can be detected, without the supply being disconnected.
Indeed the earthing would somtimes be the centre of some warning lamps so that they all lit dimly, when all was well, and earth was in the centre of the live conductors, and when one side was faulted to earth, then one lamp or group of them would go out, and the remaing come on brighter, so show a fault state on one side. The problem with having a 'neutral' is that it is not sensible to fuse it, when it is at or near earth potential, but the whole ADS needs rethinking when either side could be live or not. Wiring so all cores are treated as live is a far safer way to operate - some odd applications like undersea power works this way for example, and often at odd voltages too, like 690 single phase for example. I understand that on ship AC 3 phase is often with "insulated neutral" , but we'd need someone like Ancient Mariner to confirm if that is true IT, though I fear we may have lost him in the forum move.
