Might not be a bad idea to verify connection integrity between the utility transformer )Pole Pig) and the load center.
Dan Brown
Foxfire Energy Corp.
Renewable Energy Systems
(802)-483-2564
www.Foxfire-Energy.com
NABCEP #092907-44
-------- Original Message --------
Subject: Re: [RE-wrenches] Buck-Boost transformer to mitigate high
voltage drop?
From: Will White <w...@solarenergy.org>
Date: Thu, August 18, 2016 11:49 am
To: RE-wrenches <re-wrenches@lists.re-wrenches.org>
I've had the exact same problem except we also had high voltage at the transformer due to a utility substation being rebuilt. We had to open the voltage window of the inverter and that solved the issues.On Wed, Aug 17, 2016 at 2:12 AM, <d...@energysolarnow.com> wrote:Howard-Any voltage drop at the house will be a function of current drawn by the house load. Shut off most loads and there will be minimal voltage drop. If there was a low voltage issue now before solar is installed, there would be symptoms like florescent lights not working well. That's why they flicker when a big motor kicks on nearby.A transformer could be used to boost the voltage to the house, but that assumes more or less constant load. When the house load is low there is minimal voltage drop and the boosted voltage may become too high. The utility service transformer may have different wire taps to adjust its output voltage as well. But again, this assumes more or less constant load.When there are long wire runs it is more common to use a pair of transformers, one at the utility drop and one at the house, to boost (or step up) the voltage at the service drop end to, say, 480 with a 2:1 transformer. That is, the ratio of number of primary to secondary windings is 2:1. Then at the house another matching transformer bucks (steps down) the voltage back to 240.The current in the long wire run is cut in half, and so is voltage drop.This boosted voltage can be higher-- thousands of volts are not uncommon on ranch properties with miles-long wire runs.A solar inverter senses the voltage at it's connection point, and raises it's voltage a couple volts higher to push solar current into the wire. If there is voltage drop in the wire, the solar inverter must raise it's voltage even higher to overcome voltage drop and still be a couple volts above the grid. If voltage drop is severe, the inverter will sense that it's voltage is getting too high out of range and fault with a grid voltage error. Grid voltage is not changing, inverter voltage is.For example, we had an inverter sited at a 10 KW array connected to a garage with 200' of existing 6 AWG AL buried wire. The attendant voltage drop from nearly 40 amps solar current caused the inverter to raise it's own voltage so much to overcome voltage drop that it faulted. It was necessary to tweak the software settings to allow the voltage range to be extended.When your client's 20 KW solar inverter is sited at the house, any solar current will first be consumed by the house loads. This reduces current through the long wire run and so reduces voltage drop. When the solar current matches the house loads, no current flows through the long wire run and there is no voltage drop. Everyone is happy, except the utility company who now doesn't get to sell energy.Excess solar current not consumed by house loads will run back through the long wire to the utility grid, causing some voltage drop. This must be overcome by the inverter raising it's voltage to still be a couple volts over grid-voltage-plus-voltage-drop. Without running the numbers I suspect that the less-than-40 solar amps you may run into 4/0 AL wire will not be a problem.You will want to measure the voltage at the house under low and maximum load conditions.If the load is at max when the sun shines, a solar inverter will tend to help alleviate any low voltage issue at the house, as Ray W. wrote.Don BarchEnergy SolarDate: Tue, 16 Aug 2016 14:23:27 -0600
From: Ray Walters <r...@solarray.com>
To: RE-wrenches <re-wrenc...@lists.re-wrenches.org >
Subject: Re: [RE-wrenches] Buck-Boost transformer to mitigate high
voltage drop?
Message-ID: <c0339c2a-4d02-f64c-2512-fb1a7bbc0...@solarray.com >
Content-Type: text/plain; charset="windows-1252"; Format="flowed"
My guess is that in your case the GTPV will just help alleviate the volt
drop situation. I wouldn't start adding transformers, etc until you are
having a problem. Put in the contract that this extra cost may be
necessary for proper function, but I would keep it as a backup. Based
on the numbers you just mentioned, you would only be selling a surplus
of 30 amps, and the existing wire should be adequate for that.
R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760
On 8/16/2016 1:16 PM, Howard Arey wrote:
>
> Answers to all:
>
> No ? I did not measure voltage at the house. Right now, only an
> assumption of voltage drop based on my perception of what ?typical?
> loads might be on this 150-amp service. I wasn?t expecting to see such
> small wires for such a long run from transformer to house when I
> showed up there without a voltmeter. He is a heavy user, using 6,000
> kwh in some months
>
> We?re looking at a 20KW system (he has some other expansion
> requirements, he has the roof space, and the need.) I roughly estimate
> that he?ll use onsite 40-50 amps of the 82 amps at peak inverter power
> output.
>
> Interesting to hear of one transformer response and hope to learn more
> on that, too.
>
> *Howard ?Scot? Arey*
>
> Owner, Solar CenTex
>
> 254-300-1228
>
> scot.a...@solarcentex.com
>
> www.solarcentex.com <http://www.solarcentex.com/>
>
> https://www.facebook.com/SolarCentex
>
> Rated #1 Solar Installer in Texas by Solar Reviews
> <http://www.solarreviews.com/solar-companies/top-100- >__residential-solar-power- contractors-2016/texas/
>
> Solar Centex Logo - No Back
>
On Tue, Aug 16, 2016 at 12:16 PM, Howard Arey <scot.a...@solarcentex.com>
wrote:
Good day,
I have a potential client that has an existing 1,000 foot run from the
meter and transformer at the street to the home. This is 4/0 Al and quick
calcs show the voltage drop at over 12%. He acknowledges that the wire is
undersized to keep voltage at/about 240 volts (I have not measured directly
at the street / transformer yet).
I know the wire has the necessary ampacity to carry his current service
needs and to carry amps from the to-be-suggested solar system.
My concern is that the voltage drop will change the 240 volts at the
street/transformer/meter to 211ish (or will I see a higher 268?sh voltage
at the far house end?) at the house. The inverter will try to synch to this
voltage but of course this is outside of typical inverter parameters.
So, instead of re-running much large wire, does anybody have experience and
comments about potentially using a buck-boots transformer at the home to
get us back to 240 volts? This would need to be service entrance sized.
*Howard ?Scot? Arey*
Owner, Solar CenTex
254-300-1228
scot.a...@solarcentex.com
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