Thanks everyone for the replies. I think there were numerous errors in some of the figures that were quoted. I just double checked myself by spending an hour going over the formulas, using a VD calculator, and doing some examples. Here is what I get:
wind turbine is 1kw, 240v three phase
wire is #10
distance is 1350 feet (one way not circuit length)
Three phase VD=1.732 x K x Q x I x D/CM
K=12.9 for copper (resistance constant)
Q= alternating current skin effect correction factor for large conductors. NA here.
I= current
D= distance
CM = circular mills of conductor
Note that line current for three phase is found by Watts=V*A*1.732 (ignore power factor) thus solving for our values gives I= 2.4A
So VD= 1.732 x 12.9 x2.4*(1350/10380)
thus VD=~7 volts or about 3% AT MAX POWER
But note the VD is not what I am looking for, I know how to get VD, I just thought I would go over that because there were some conflicting answers. I have two questions:
- How does one estimate the average voltage drop given that the turbine will of course not be operating at max power all the time? would calulating the VD at average wind speed correspond to average vd drop (and thus average loss) or doesnt it work out that way?
- Why does Hugh get twice the drop with his "2/3rds method" (http://www.scoraigwind.com/CABLE/index.htm) than I do using the above formula? Of course that is a good question for hugh directly, I'll email him if he doesnt jump in and nobody else knows.
Best regards to everyone and have a good weekend.