Voltage Drop check

Status
Not open for further replies.
D

Designer69

Senior Member
836 feet 480/277V 3ph 4w system, running 4/0 AWG copper, 250 Amps load

I calculate this at 2.2% or 6.2 Volts.

Can someone confirm this using their methods? TY
 
I come up with a drop of about 18.5 volts, figuring the 836 as the one way distance in feet and assuming it is an underground installation (<25c).

18.7 x 836 x 250 / 211600 = 18.47ish volts
 
Designer69 said:
836 feet 480/277V 3ph 4w system, running 4/0 AWG copper, 250 Amps load

I calculate this at 2.2% or 6.2 Volts.

Can someone confirm this using their methods? TY
Click to expand...
Thats in the ballpark for 2 - 4/0 Cu per phase. One per phase = 4.7% 13 volts
phase to neutral.
 
jeez I was way off... damn

Im not understanding the difference between 1 way / total length.. there are 4 conductors total, all 4/0 from the pole mtd transf to the meter bank. that distance is 836ft
 
Designer69 said:
jeez I was way off... damn

Im not understanding the difference between 1 way / total length.. there are 4 conductors total, all 4/0 from the pole mtd transf to the meter bank. that distance is 836ft
Click to expand...
Appears you have 3 phase conductors and a neutral. If its 3phase, you only count the circuit length one way, 836 ft.
Post your numbers and lets see what you did. By the way, 4/0 is only rated for 230 amps.
 
Last edited:
Designer69 said:
jeez I was way off... damn

Im not understanding the difference between 1 way / total length.. there are 4 conductors total, all 4/0 from the pole mtd transf to the meter bank. that distance is 836ft
Click to expand...
That's one-way distance.

Total length is distance through the entire circuit loop, i.e. source out to load and back to source.
 
Designer69 said:
ohh ok I get it, thats why I was getting around half of everyone else's numbers.

I'm slow, Thanks guys
Click to expand...
Single phase VD calcs use one-way distance times 2.

Three phase VD calcs use one-way distance times 1.732 (square root of 3).
 
Designer69 said:
836 feet 480/277V 3ph 4w system, running 4/0 AWG copper, 250 Amps load

I calculate this at 2.2% or 6.2 Volts.

Can someone confirm this using their methods? TY
Click to expand...

25.48V or 5.31% @ 1.0 pf
22.93V or 4.78% @ .9 pf
21.66V or 4.51% @.85 pf

The % represents 480V source voltage. The % would increase if the base is taken as 460V.
 
Last edited:
weressl said:
25.48V or 5.31% @ 1.0 pf
22.93V or 4.78% @ .9 pf
21.66V or 4.51% @.85 pf

The % represents 480V source voltage. The % would increase if the base is taken as 460V.
Click to expand...
Hmmm... by my calc's the VD goes up for lower pf's. I'm using IEEE method and Table 9 values for PVC, with R adjusted for ambient temperature (20?C underground) and current through conductor...

480V Source:
23.28V or 4.85% @ pf=1.0
27.31V or 5.69% @ pf=0.9
27.49V or 5.73% @ pf=0.85​

View attachment 1490
 
For my education, would you guys include your formulas and results like Smart did in his last post? The ambient correction angle is very helpful. I love watching great minds at work.
 
Smart $ said:
Hmmm... by my calc's the VD goes up for lower pf's. I'm using IEEE method and Table 9 values for PVC, with R adjusted for ambient temperature (20?C underground) and current through conductor...

480V Source:
23.28V or 4.85% @ pf=1.0
27.31V or 5.69% @ pf=0.9
27.49V or 5.73% @ pf=0.85​
Click to expand...
I have the same numbers as you. However at pf = 0.60 the VD begins to decrease. Capacitor effect. Voltage rise.
 
bob said:
I have the same numbers as you. However at pf = 0.60 the VD begins to decrease. Capacitor effect. Voltage rise.
Click to expand...
I was just using the pf's used by Laszlo, and didn't check others. My excel "calculator" does not account for capacitance, but in checking for reversal, my "calculator" shows the VD peaks at pf=0.84.
 
Karl H said:
I'm using VD=(1.732xKxIxD)/CMILS and I'm finding it too primative and incomplete without doing ambient correction adjustments.
Click to expand...
It all depends on how close to borderline you want to get :grin:
 
Status
Not open for further replies.
Top