[RE-wrenches] Strange voltage readings, power quality

Kirpal Khalsa solarworks at gmail.com
Sun Nov 13 18:27:47 PST 2011


I had this also happen recently with a battery bank.....we found that the
cables had some bad connections due to a poor connection....we had used
QuickCote on the cable lugs and the battery lugs prior to installing the
cables.  We disconnected all cables and wire brushed them, reassembled and
then installed a different corrosion preventer after the lugs were attached
to the battery terminals.....this way it was clean terminal joined to clean
battery cable lugs throughout.....
It has been a couple months and problem seems to have disappeared
especially after a couple aggressive corrective equalization charges.
There was no visible corrosion on the battery cables or terminals.....the
customer did not do a stellar job of regular equalization or water topping
off as we arrived and the plastic grids above the plates were just covered
up.....we re advised them on the cost savings achievable by regular care
and maintenance of the battery bank....
Cheers,
-- 
Sunny Regards,
Kirpal Khalsa
NABCEP Certified Solar PV Installer
Renewable Energy Systems
www.oregonsolarworks.com



On Sun, Nov 13, 2011 at 1:12 PM, Nathan Jones <solardude97 at yahoo.com> wrote:

> Mac,
> I have encountered two battery based inverters that were affected by the
> feedback frequency of CF bulbs. One would trip and show overload from a
> single 15 watt bulb with no other loads connected every time. The other one
> was an intermittant situation. Had I not encountered this problem before I
> might still be trying to figure that one out. I think it would be worth
> ruling out as a possibility at this point.
> Nathan Jones
> Power Source Solar
> 417-827-0738
> On Sun, Nov 13, 2011 10:55 AM CST mac Lewis wrote:
>
> >Hello wrenches,
> >
> >I am having an interesting grid-tied issue and would love to get some
> input.
> >
> >The installation is 3 Fronius IG Plus inverters all single phase, two 7.5s
> >and one 10.0.  The service is 120/208.  We have the two 7.5s feeding a
> >dedicated 3 phase sub and tied back into the main panel after production
> >meter.  The first 7.5 is tied across Va to Vb, the second is tied in
> across
> >Vb to Vc.   The 10.0 feeds directly back to the main panel after
> production
> >meter and is tied in across Va to Vb.
> >It should be noted that this facility has very large capacitive load,
> about
> >25 kW of grow lights.  According to an egauge on site, the power factor
> >ranges from 0.5 to 0.75 on all phases.
> >The system worked flawlessly for 3 months, suddenly the two 7.5s dropped
> >out and gave a myriad of grid errors, everything from islanding errors, to
> >high grid voltage, and low grid voltage etc.
> >
> >I went over there and found the phase B voltage to neutral, was way out of
> >wack, anywhere from 120-170.  Oddly, the Line to line voltage was fine,
> >right around 208 for all phases.  I called the power company and had them
> >install a monitor at the transformer.  After 5 days they came back and
> said
> >that their end was within spec.  I decided to put both of the 7.5s between
> >Va to Vc.  They would not boot up.  I then went to the main panel and
> >changed the physical location of the breaker for the subpanels of the
> 7.5s.
> > This seemed to make the difference.  They booted up and are exporting
> >power.  I tried switching one of the 7.5s back Va to Vb, but it still
> would
> >not boot up unless it is connected from Va to Vc.
> >
> >My working theory right now is that we are getting harmonics traveling
> back
> >to the inverters from the ballasts on the grow light across line B.  As
> far
> >as explaining why it suddenly happening, my guess is that he has started
> >turning off inductive loads such as fan motors and compressors as we are
> >entering the winter.  There may have been a filtering effect going on with
> >the motors absorbing some of these harmonics and attenuating them.  I am
> >going to try to verify this with an oscilloscope this week.
> >
> >Does anyone have any other theories to explain this type of behavior?
> > Anyone seen this before?  Should I look for anything else?
> >
> >Thanks
> >
> >Mac Lewis
> >
> >
> >--
> >
> >
> >
> >Mac Lewis
> >
> >*
> >
> >"Yo solo sé que no sé nada." -Sócrates
> >*
>
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