high voltage DC wire size?

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Old 04-19-06, 09:50 PM
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high voltage DC wire size?

We are hooking up a grid-tied wind turbine. From the turbine to the inverter it is 280 volts DC (yes DC) and 20 amps. It is a 200' run, including the height of the tower. We want to keep our voltage drop under 5%. Any idea what size wire we need, in copper and aluminum?
Thanks!
Jon
 
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Old 04-19-06, 10:24 PM
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work it backwards

Thats about 400 Vac peak to peak, its not high voltage. Your local electrician should be able to spec this for you easily. But your best to pick a bigger than a smaller one to minimise losses. I would guess your looking at something between 6mm and 10mm cross section area.

If you want less than 5% voltage drop then you are looking at 14Vdc drop. At 20Amps thats a total impedance of 0.7 ohms or 0.35ohms per 100ft, power loss is 280W.

Then get the specs of the underground cable from your local supplyer and see what the resistivity is per 100ft and pick a cable with lower resistivity.

For example a Pirelli 0.6/1kV insulated and sheathed cable, 16mm sq cross section area is rated at 115 amps burried direct in ground, its DC resistivity is 1.15 ohms per Km, approx 0.038 ohms per 100 ft.

Best to get an electrician to spec it for you.

Copper should be cheaper than aluminium.
 

Last edited by eightfootplus; 04-19-06 at 10:36 PM.
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Old 04-19-06, 10:30 PM
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We are hooking up a grid-tied wind turbine. From the turbine to the inverter it is 280 volts DC (yes DC) and 20 amps. It is a 200' run, including the height of the tower. We want to keep our voltage drop under 5%. Any idea what size wire we need, in copper and aluminum?

ok for wire size in copper it is #8

for alum wire it will be #6

this is the THWN type wires


the best way to run the wire[s] is in the conduct like 1 inch pvc or rigid steel if burail wire.

but a head up here with wind turbines you must have some kind of transfer or inverter system to protect the system and can not back feed to the uiltiy system this is very impoart part here

if you going to do this wiring make sure you get proper permit and have the inspector check the wiring system to make sure it is ok to your state code as local code as well

and to bury the wires it have to be at least 18 inch deep .

Merci , marc
 
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Old 04-19-06, 10:36 PM
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How many wires do you have? One or two ungrounded?
One ECG/GEC?

You talking 20A DC, so #12 Cu (0.64 ohm in 400') should handle it within the -5% no problem.
But any voltage drop wastes energy. I suggest #6 Cu (0.16 ohm in 400') or #4 Al for negligible drop. Basically it will pay for the extra cost over time. As 8'+ pointed out, smaller wire is like leaving several lights on. The larger wire might cost another $40, but you soon save $40 by "keeping the lights off".

Buy a 500' spool of #6 THHN stranded for bulk pricing on the wire.

For everything Marc said, what's really important is good grounding to control the lightning as much as possible.
 
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