Indeed, it could be as simple as a
ground loop. A similar issue occurred ten or so years ago on a
much smaller scale. A small off grid system with a Trace Tiger 500
inverter would trip off with no loads. This had been installed by
another solar installer. We were called to troubleshoot the
installation. I found about 3 or 4 neutral-ground bonds. Once
reduced to one, the tripping issue never returned.
Allan
Allan Sindelar
al...@positiveenergysolar.com
NABCEP Certified PV
Installation Professional
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder, Positive Energy, Inc.
A
Certified B CorporationTM
3209
Richards Lane
Santa Fe, New Mexico 87507
505 424-1112 office 780-2738 cell
www.positiveenergysolar.com
On 2/12/2014 11:43 AM, Ray Walters wrote:
I
just had an idea on this situation from August's comment. I'm
sure you've checked already, but are you sure that ground and
neutral aren't bonded in both locations, causing current to flow
through the ground system? I've seen many multiple building
properties inadvertently send both a ground wire and neutral to a
separate structure with neutral bonded to ground in both
locations.
If the separate structure has its own grounding system and bond,
then disconnect the ground wire connection back to the other
building, as it will still be bonded through the neutral. The
other option is to set a separate ground buss in the load center
at the separate structure, and unbond neutral from ground, since
it would bonded back at the other building.
Just an idea, I've seen all sorts of weird things happen with
current flow on the ground. If you have uneven current flow on
that long a run, it could definitely cause some issues.
R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760
On 2/12/2014 9:14 AM, Exeltech wrote:
Troy,
Elsewhere in this thread, boB (Midnite) suggested connecting
one of the problematic lights and dimmers directly at the
inverter output.
This is a very sound recommendation, and would immediately
rule in .. or rule out the conductors (and related circuits) as
an issue.
Another Wrench suggested using an oscilloscope to check the
waveform at the load end. This too is excellent advice, and
would be even more telling than connecting the lamps and dimmer
directly at the inverter. The ‘scope will reveal the AC voltage
AND a visual indication of any waveform distortion, either
aspect of which could potentially cause the flicker you
describe.
If you don’t have access to a ‘scope, boB’s comment about
connecting at the inverter won’t require any test equipment.
At a minimum, set your DVM to record the voltage minimum;
connect it the lamp circuit, and turn on the 1 kW load you
described. If the voltage is dropping notably, this too would
introduce visible flicker. The DVM method is less accurate than
an oscilloscope, but better than nothing, and depends greatly on
the quality (or not) of your DVM.
The above aside, anything else would be strictly conjecture ..
which we can do all day, and never be correct.
Dan
--------------------------------------------
On Wed, 2/12/14, August Goers <aug...@luminalt.com> wrote:
Subject: Re: [RE-wrenches] Long transmission line inductance
and LED light flicker
To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org>
Date: Wednesday, February 12, 2014, 9:01 AM
Hi Troy,
Have you double checked that your grounding systems both in the
house and at the inverters/array are all up to snuff?
Sorry I can’t offer any help with the inductance issue.
Best,
August
From: re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of
Troy Harvey
Sent: Tuesday, February 11, 2014 5:45 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Long transmission line inductance and
LED light flicker
Richard,
The system configuration is:
Approx 24.7kW of modules connected to:
2 x 9kW Sunnyboys
1 x 5kW Sunnyboys
Plus
4 x 6kW sunnyislands, with 2 Parallel 48V Strings of (12 x 4V
Surrettes ) using 350MCM cable
Wire
The wire is about 1000 feet long 350 MCM in a "twisted" bundle
to this outbuilding
Conditions
The conditions were during the day with full sun, so during the
test there is approx. 47kW of available inverter pointed at only
>15 amps (120V) of load(!).
The steady state conditions was a few LED lights, maybe 60 watts
worth, plus a handful of vampire loads, maybe 100-200 watts
total. When a pure resistance load, like a 1000W curling iron
was turned on the lights would flicker.
Since the lights flickered from a resistive load, but didn't
stay dim, I assumed it was from a reactive-phase issues due to
the transient turn-on - screwing with the LED dimmer circuits
which are already doing a bit of magic to turn TRIAC waveforms
into a DC constant current.
thanks,
Troy Harvey
---------------------
Principal Engineer
Heliocentric
801-453-9434
tahar...@heliocentric.org
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