How do you calculate percentage Vd for single phase? 4

[AusLee]

Hi,

Can someone please advise on which voltage the single phase voltage drop is calculated?

The application is simple: we have a cable 100m long. It is a 3 phase multi-core copper cable with cross section 25mm² per phase and neutral. The voltage is 230/400V 50Hz.

From page 87 in the following manual (Olex Handbook, the characteristic voltage drop is 1.61 mV/A/m

The loads at the end are 3 single phase loads, each consuming 10A and are a balanced load.

So the voltage drop in principle would be: 1.61 x 100 x 10 = 1.61V.

As the load is single phase, if you divide 1.61/230 = 0.7%. But if you divide by 400V, then it becomes only 0.4%. Which percentage value is correct?

Also, say for some reason two of the loads have been manually shut off, there remains only one load of 10 A on one phase in this 3 phase cable. As there are no loads on the other phases to balance it, the current in the neutral is then 10A also and not zero and consequently the voltage drop across the neutral should be accounted for. How do you calculate that in this case? 1.6 x 100 x 10 times 2?

Thanks.

 

[AusLee]

Yes we do have a requirement to identify the conductors by color.

The tip of paralleling just the phases is appreciated thanks.