How good are you at telling the difference?
How good are you at telling the difference?
yuk! unbalanced neutral current by design. And no lower covers fitted over the rubber trouser sleeves.
yuk! unbalanced neutral current by design. And no lower covers fitted over the rubber trouser sleeves.
I'm pretty sure I've seen 3-phase installations fed by three single core concentric overheads - so such things might not be too far from the norm in DNO land. I presume the incoming cables are modern concentrics with copper rather than steel "armour" - so no induced currents to worry about and the line conductors will have their own insulation underneath the trouser boot, so insulation+sheath overall. DNO's don't regard Ns as hazardous. Assuming the two supplies are on different phases the (and not too many nasty harmonics in the load) then the N current shouldn't exceed that of one phase, so no overloading issues. I might have preferred to see both cables run much closer together from an EMI perspective and perhaps the two N linked, just as a nicety and reduce N v.d. a bit.
- Andy.
If both phase are say loaded to 100A, then the neutral is - 100A, yes, as the missing third phase would sum to zero, and this is a worst case, but its horrible from an EMC point of view or for 3rd harmonics, and at any point those cables may go through a metal hole. Not to mention the massive extra magnetic field, some associated extra volt drop, and probably not great for loop hearing aids either.
Mike.
It’s not three-phase, but it does appear to be TN-C-S (PNB).
The phases are at 180 degrees, not 120.
The phases are at 180 degrees, not 120.
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