That to some extent is my gripe. The amendment aims to deal with the risk in single phase installations, but not 3-phase ones.
Yes, the new device described in option (iv) - based on the L-N voltage going out of bounds - is only permitted for single phase installations. From what I gather that's not casting any aspersions on 3-phase systems, but an acknowledgement that the approach is basically flawed as it is possible to have a combination of 3-phase loads and a broken PEN such that a L-N voltage is still within 230V+/-10% but the PEN is way over 70V from true Earth. If you do have a 3-phase system (and can't compare voltage with an electrode) you're far better off using one of the approaches in option (iii) - i.e. comparing with an artificial N point generated from all three lines (see A722.4) as that's far more reliable. So basically the most flawed approach is only allowed where there's no better alternative.
That to some extent is my gripe. The amendment aims to deal with the risk in single phase installations, but not 3-phase ones.
Yes, the new device described in option (iv) - based on the L-N voltage going out of bounds - is only permitted for single phase installations. From what I gather that's not casting any aspersions on 3-phase systems, but an acknowledgement that the approach is basically flawed as it is possible to have a combination of 3-phase loads and a broken PEN such that a L-N voltage is still within 230V+/-10% but the PEN is way over 70V from true Earth. If you do have a 3-phase system (and can't compare voltage with an electrode) you're far better off using one of the approaches in option (iii) - i.e. comparing with an artificial N point generated from all three lines (see A722.4) as that's far more reliable. So basically the most flawed approach is only allowed where there's no better alternative.
