Feeder Voltage Drop

[juangla99]

I am not shure how to calculate the voltage drop of the following incoming line:

9 - #500 kcmil THWN Aluminium (phase) + 3 - #500 kcmil THWN Aluminium (neutral)

The system is serve in 480 V, 3 phase. The load is 425 kVA, and the length is 150 meters.

 

[augie47]

Assuming you mean 3 500s per phase, using a chart, unless I made a conversion error, the drop should be around 7 volts looking at phase to phase.
Don't know about L-N as you don't list the neutral load.
Keep in mind I may be in error. I'd suggest you wait for a 2nd look,.

 

[RichB]

Assuming you mean 3 500s per phase, using a chart, unless I made a conversion error, the drop should be around 7 volts looking at phase to phase.
Don't know about L-N as you don't list the neutral load.
Keep in mind I may be in error. I'd suggest you wait for a 2nd look,.

Everything augie said--I get 6.7 volts drop--so call it 7

 

[kingpb]

150m = 492ft
425KVA @ 480V 3ph = 511A

3 x 500KCMIL Al/ph

I'm coming up with just about 2%

You could actually go with 2 per phase.

 

[Julius Right]

Since we don't know how the 12 single-core cables are running [in groups of 4-each group of all phases and N, for instance- or in conduits or in cable tray or else] so we don't now the distance between cables. It is important in order to calculate the resistance [proximity factor] and the reactance. Also we don't know the power factor, the frequency and the conductor temperature.
In order to get 7 V voltage drop we have to take-for instance-groups of 4 cables laid in straight line ABCN, NCBA.. and so on, power factor of 0.99 , 60 Hz and 75oC.
I agree with kingpb. For 2 cables per phase the voltage drop will be 11.82 V [2.46%] less than recommended by NEC [Art.215.2 Minimum Rating and Size. (A) Feeders Not More Than 600 Volts.(b) Informational Note No 2.]