how do megawatt Solar farms prevent voltage loss in long wire runs?

rollandelliott

how do megawatt Solar farms prevent voltage loss in long wire runs?
Looks like some wire runs are a few football fields long!
Just curious!

mikeo

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

how do megawatt Solar farms prevent voltage loss in long wire runs?

I would guess by using high voltage.

ggunn

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

rollandelliott wrote: »

how do megawatt Solar farms prevent voltage loss in long wire runs?
Looks like some wire runs are a few football fields long!
Just curious!

With AC runs, sometimes with big wire and parallel runs, sometimes with step up/step down transformers, depending on the economics of the situation and the length of the run. Keeping the inverters and combiners as near as possible to the arrays helps with the DC voltage drop, as well as running big wire from the combiners to the inverters.

Typically the specs for voltage drop are more restrictive on the AC side, since voltage drop on the AC line results in voltage rise at the inverter terminals and can kick the inverter off line.

There is always some loss due to voltage drop. There is no way around it.

niel

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

rollandelliott wrote: »

how do megawatt Solar farms prevent voltage loss in long wire runs?
Looks like some wire runs are a few football fields long!
Just curious!

technically, it doesn't prevent voltage losses, but the higher voltages lower the percentage of loss for identical currents passing. the v drop actually is the same volts lost in identical currents passing, but if the reference voltage is higher the loss is then lower percentage wise.

if one only has a certain wattage to pass then going to a higher voltage will cut the current that must pass by the formula P=I*v. the lowered current passing through the same wire will then exhibit an actual lowered voltage loss and not just a percentage benefit.

jaggedben

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

I think in many cases the true answer is...

They don't.

ggunn

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

jaggedben wrote: »

I think in many cases the true answer is...

They don't.

I disagree. It's true in all cases. It's a matter of degrees and of balancing cost of materials with acceptable losses, but the losses are never zero.

feedhorn

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

They are called Big Thick Aluminum Buss Bars.

FH

Cariboocoot

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

ggunn is, of course, right: there is no way to prevent Voltage drop and resultant power loss. You can only minimize it. The usual way: high Voltage to begin with, thick wires, nitrogen-filled transmission lines, alien time-warp technology, et cetera.

niel

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

feedhorn wrote: »

They are called Big Thick Aluminum Buss Bars.

FH

even those large buses have resistance and if some will look i had already said, "technically, it doesn't prevent voltage losses" in wire runs. any resistance will have a predisposed v drop with a specified current going through it.

for example, if you run 12v with 10a through a 20ft long piece of #10 cu wire it will drop .255v at 90 degrees c for a percentage of 2.123%. with everything the same except for the voltage which we will put to 24v for our demonstration we see the same .255v being dropped, but because it is 24v being referenced to, the percentage is now 1.061%. do note that doubling the voltage with the same current will double the wattage flowing through the wires. no v drop is prevented by a large solar farm or even by higher voltage if the current and wire size is held to the same values. if it is a question of a set wattage with raised voltages then that will reduce the current flowing and reduce not only the %, but it will reduce the actual v drop itself. all wires, connectors, etc. have resistance and as such will always have a v drop no matter how large or small. when one ventures into the land of 0 ohms resistance you have entered a mythical area that does not exist except in theory and even then that would create a circumstance of infinite current with 0 volts which for many of us know that means there is no power because v x i = p.:roll:

what large generation points do is raise the voltage while keeping the same current in a wire which in effect allows more power to be transferred through that same wire over the same distance. power utilities do take advantage of this so they do not need to change out the wires already present to carry more power over them and those wires would be expensive to change out in order to up the capacity the same amount as upping the voltage has allowed.

so ends this electrical lesson. case closed.

ggunn

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

Cariboocoot wrote: »

ggunn is, of course, right: there is no way to prevent Voltage drop and resultant power loss. You can only minimize it. The usual way: high Voltage to begin with, thick wires, nitrogen-filled transmission lines, alien time-warp technology, et cetera.

What do N2 filled transmission lines do? I assume that this is to exclude O2, but why? How does it reduce line loss?

niel

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

ggunn wrote: »

What do N2 filled transmission lines do? I assume that this is to exclude O2, but why? How does it reduce line loss?

the only thing i can think that might do is preserve the wire so that no oxidation takes place to degrade the wire. oxidation would lead to higher resistance.

mike95490

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

ggunn wrote: »

What do N2 filled transmission lines do? I assume that this is to exclude O2, but why? How does it reduce line loss?

Filled with liquid nitrogen ?

There are a few areas where some superconducting power lines are installed.

niel

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

mike90045 wrote: »

Filled with liquid nitrogen ?

There are a few areas where some superconducting power lines are installed.

nobody said liquid nitrogen as they would trap the gas into the gap areas that show up in the wire. i've often wondered the difficulty in doing this and how they preserve it inside of there once it's there.

BB.

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

In general, for pressurized telecom cables it was to keep water out and could also indicate cable damage if pressure was lost.

High pressure could also reduce arc-over inside a cable assembly...

NKT High Voltage cable.

15 BAR Nitrogen *(~217.5 PSI) paper insulated cable (apparently, this is 1930's tech--and this particular stuff is kept around for repairing of existing cable runs.

-Bill

ggunn

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

niel wrote: »

the only thing i can think that might do is preserve the wire so that no oxidation takes place to degrade the wire. oxidation would lead to higher resistance.

But copper does not oxidize readily in air and I believe that when it does it forms a thin impervious layer that prevents further oxidation. I don't think that's it.

niel

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

i'm guessing as i use standard wires. btw, copper does eventually get eaten through by oxidation and any oxidation that is there has a high resistance to it electrically.

ggunn

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

niel wrote: »

i'm guessing as i use standard wires. btw, copper does eventually get eaten through by oxidation and any oxidation that is there has a high resistance to it electrically.

So far, Google has yielded nothing. I am pretty sure I have seen N2 cannisters in substations, though. Copper gets eaten by corrosion from exposure to some things, but air isn't one of them. Other than turning brown on the surface, there are plenty of copper coins that have been around a very long time with no ill effects.

niel

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

ggunn wrote: »

So far, Google has yielded nothing. I am pretty sure I have seen N2 cannisters in substations, though. Copper gets eaten by corrosion from exposure to some things, but air isn't one of them. Other than turning brown on the surface, there are plenty of copper coins that have been around a very long time with no ill effects.

i never said anything about air.

ggunn

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

niel wrote: »

i never said anything about air.

OK, but what other function could nitrogen serve besides displacing air? You did mention oxidation; what source of oxygen other than air are copper conductors likely to be exposed to?

I'm not trying to be combative, I'm just trying to reason it out.

BB.

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

I am loosing sight of what the question is? Dry compressed nitrogen is cheap and relatively non-reactive.

Low pressure is used to charge cable runs (such as telecom) to keep water out and loss of pressure can be used to detect impending cable failures and damage.

High pressure Nitrogen is used for (some) high voltage applications to increase dielectric strength/alternative to other insulative materials. Has even been used at 15 Bar (~217 psi) for as insulation for (I guess) >100,000 volt buried "paper insulated" transmission cable since the 1930's (mostly Europe?)...

-Bill

Cariboocoot

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

I've got to refrain from starting these Easter egg hunts; they always seem to lead to arguments.

Bill had the answer at post #14.

Now, what about the alien time warp technology?

ggunn

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

Cariboocoot wrote: »

I've got to refrain from starting these Easter egg hunts; they always seem to lead to arguments.

Bill had the answer at post #14.

So he did. Somehow I managed to miss it the first time. Thanks, Bill!

niel

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

Cariboocoot wrote: »

I've got to refrain from starting these Easter egg hunts; they always seem to lead to arguments.

Bill had the answer at post #14.

Now, what about the alien time warp technology?

yes, stop that as somebody is bound to complain you are picking on watch making in another far off country and then somebody will assume we are talking about their great uncle hands solo (yep, i went there) who fixed watches.:p:p:roll:

ggunn

Re: how do megawatt Solar farms prevent voltage loss in long wire runs?

niel wrote: »

yes, stop that as somebody is bound to complain you are picking on watch making in another far off country and then somebody will assume we are talking about their great uncle hands solo (yep, i went there) who fixed watches.:p:p:roll:

What we need is a hyperspace link to the interior of the sun. Now that's solar power. ;^)