Distribution voltage drop over distance
Distribution voltage drop over distance
(OP)
Hello,
I am trying to figure out a rough calculation of the voltage drop of a 25kv, 336 kcmil ACSR conductor over given lengths (40km or more) from 2 8MW feeders.
It has been a while since I have touched this stuff and can't remember the equations I should consider for a rough estimate or any additional data that I might need to make an informed answer.
Any help would be greatly appreciated
I am trying to figure out a rough calculation of the voltage drop of a 25kv, 336 kcmil ACSR conductor over given lengths (40km or more) from 2 8MW feeders.
It has been a while since I have touched this stuff and can't remember the equations I should consider for a rough estimate or any additional data that I might need to make an informed answer.
Any help would be greatly appreciated






RE: Distribution voltage drop over distance
RE: Distribution voltage drop over distance
Normally I think you would need to know the code name for the conductor and for a 336 kcmil I beleive there are a couple choices :
Merlin
Oriole
Linnet
...
Ok so stay with me here,
if we select Merlin, we know
R(AC@75C) = 0.0625 ohm/1000ft
519 allowable amps
then I would think I would need to consider the current flow for my case, as I believe that is the biggest factor in determine losses. Given that I have 2 8mw feeders @ 25kv this yeilds 8mw/25kv = 320amps
then I could use Vdrop = Ir*R + Ix*X however I don't know the power factor... or the reactance. I suppose I could just assume unity PF...
So am I on the right track here? Or is it possible to get more or less a rule of thumb over distance for given voltage drops without knowing much else?
RE: Distribution voltage drop over distance
The exact stranding of the 336 ACSR doesn't have as much effect.
A standard reference book such as EE Handbook or Elements of Power System Analysis will have information on calculating the line impedance per unit length.
Then you use whatever current loading you want to determine the voltage drop at that current.
RE: Distribution voltage drop over distance
Power factor?
RE: Distribution voltage drop over distance
Thanks for the input dpc. I will give those books a look over.
I guess I was looking for a rule of thumb or a basline to use for approximate voltage drop over given lengths. Stictly for observation purposes.
RE: Distribution voltage drop over distance
Ran a quick simulation with what I have in CYME's equip database for 336 kcmil. Ideal source, 40 km line and 3 phase spot load.
That should give you an idea.
We use to load our line at 350 A with margin for cold load pick-up up to 1.8 to 2.0 times normal load without problem.
Load type might cause problem (e.g. large motor) for such a distance.
RE: Distribution voltage drop over distance
Here's the output
Desrod
RE: Distribution voltage drop over distance
Thank you very much for that!
RE: Distribution voltage drop over distance
After looking up the specs on the conductor here: http://www
and calculating the equvalent R= 0.2076 ohm/km X = 0.39567 ohm/km
I think I have enough data to display various lengths using a simple short line model.
RE: Distribution voltage drop over distance