size of neutral cable
size of neutral cable
(OP)
In a four wire system ( red,yellow, blue, neutral) can we use a neutral cable
of half size the phase cable. If this is allowed, what are the conditions to be met.
V = 415V, I = 400 Amps, Length = 350 metre
of half size the phase cable. If this is allowed, what are the conditions to be met.
V = 415V, I = 400 Amps, Length = 350 metre






RE: size of neutral cable
RE: size of neutral cable
Of course, that is just an example and perhaps an extreme one at that. However, I can think of many more where this should be considered that may not seem extreme. Take a 208/120Y panel feeding receptacles. Do you really know that the receptacles will be evenly loaded (??) or do you agree that the more real case may be a few space heaters on one phase and some clocks and computers on another.
Again, this is not based on minimum code requirements but (my idea) of a common sense approach. I hope this helps.
RE: size of neutral cable
RE: size of neutral cable
RE: size of neutral cable
i think IEC60364-5-54 can help you
be happy
RE: size of neutral cable
For your distance of 350 meters you need to size the hot wires, neutral, and equipment ground on the basis of voltage drop. For good voltage regulation and efficiency I would not be surprised if you need 600 amp or even 800 amp conductors for the phases and 400 amps for the neutral and equipment ground.
RE: size of neutral cable
As with most modern rules, the onus of responsibility is with the engineer to ascertain if the installation complies.
If you have a balanced three phase load and one of the phase protective devices fails, then the neutral current will rise to the phase value. I have seen neutral conductor current detectors fitted which switch off the phase conductors if an over-current occurs. But for small installations, the cost saving of a reduced neutral is out weighed by the current protection device and usually a full sized neutral is installed.
RE: size of neutral cable
The above is what we follow widely in India. If we agree that the unbalance in phase currents and consequently the magnitude of neutral current is highest at lighting panel level and comes down at the uptream, the above appears reasonable.
RE: size of neutral cable