[RE-wrenches] National grid hertz adjustment
Exeltech
exeltech at yahoo.com
Mon Jun 27 12:38:07 PDT 2011
Hi Dave,
Just got back from from four weeks overseas plus a two-week
domestic road trip and am still unwinding (decompressing?).
Need to readjust the caffeine intake accordingly.
I accidentally multiplied the 20 minutes by 60.
Your value is correct .. and an even smaller error.
Thanks for keeping on top of things....
Dan
--- On Mon, 6/27/11, Dave Click <daveclick at fsec.ucf.edu> wrote:
> From: Dave Click <daveclick at fsec.ucf.edu>
> Subject: Re: [RE-wrenches] National grid hertz adjustment
> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
> Date: Monday, June 27, 2011, 2:26 PM
> Dan, I think we're only looking at an
> error of 20 minutes per (8760 hrs
> x 60 min / hr) = 0.00381%, well within the frequency drift
> allowed under
> UL 1741. So as you point out, it would only be the shorter
> excursions
> away from 60.0Hz that would be the issue. This shift isn't
> the easiest
> thing in the world to do (and then maintain)!
>
> On 2011/6/27 15:08, Exeltech wrote:
> > A max of 20 minutes error per year (as stated in the
> article)
> > equates to an error of 0.228%.
> >
> > Whether grid-tied inverters stay on line or not
> depends on
> > the ultimate range of the frequency excursions
> permitted
> > during the tests. UL1741 limits are 59.3 to 60.5 Hz
> for
> > fixed frequency settings. The cumulative error shown
> > above is well within those bounds. 59.3 Hz = -1.16%;
> > 60.5 Hz is +0.83%.
> >
> > However, I could see cases where they may allow 60.6
> Hz
> > one day and 59.4 Hz the next. The overall net
> difference
> > would be zero for a frequency-dependent clock - but a
> > grid-tied inverter would spend the first day of this
> example
> > totally offline.
> >
> > This would have to be a grid-wide frequency
> difference,
> > else they'd end up with some seriously large power
> flows
> > from one part of the grid to another, with potentially
> disastrous
> > results.
> >
> > It will be interesting to see how they handle this.
> >
> > Thanks for the post.
> >
> > Dan
> >
> >
> > --- On *Sun, 6/26/11, bob ellison /<reellison at gmail.com>/*
> wrote:
> >
> >
> > From: bob ellison <reellison at gmail.com>
> > Subject: Re: [RE-wrenches]
> National grid hertz adjustment
> > To: "'RE-wrenches'" <re-wrenches at lists.re-wrenches.org>
> > Date: Sunday, June 26, 2011,
> 6:40 PM
> >
> > This will make it interesting
> to everybody with a grid tie inverter,
> > can we open up the specs to
> let them work with the “new test
> > variation”? The other option
> is that the inverters will spend a lot
> > more time off line.
> >
> > Bob Ellison
> >
> > *From:*re-wrenches-bounces at lists.re-wrenches.org
> > [mailto:re-wrenches-bounces at lists.re-wrenches.org]
> *On Behalf Of
> > *Roy Butler
> > *Sent:* Sunday, June 26, 2011
> 1:45 PM
> > *To:* RE-wrenches
> > *Subject:* Re: [RE-wrenches]
> National grid hertz adjustment
> >
> > I saw this as well, came over
> the AP news wire on Friday, June 24th.
> > I've been trying to figure out
> what they hope to gain by allowing more
> > frequency
> variation.....puzzling at best!
> >
> > Roy Butler
> >
> > NABCEP Certified Solar PV
> Installer®
> >
> > NYSERDA eligible PV&
> wind installer
> >
> > Four Winds Renewable Energy,
> LLC
> >
> > 8902 Route 46
> >
> > Arkport, NY 14807
> >
> > 607-324-9747
> >
> >
> >
> >
> www.four-winds-energy.com <http://www.four-winds-energy.com>
> >
> >
> >
> > Although no trees were killed
> in the sending of this message,
> >
> > a large number of electrons
> were terribly inconvenienced.
> >
> >
> >
> >
> >
> >
> > On 6/26/2011 1:31 PM, North
> Texas Renewable Energy Inc wrote:
> >
> > This article in the local
> paper sounds a little like potential
> > trouble for grid connected
> inverters. I looked around on the NERC
> > www site without finding the
> report mentioned. Any other wrenches
> > seen anything about this
> experiment?
> >
> > Jim Duncan
> >
> > By Seth Borenstein The
> Associated Press
> >
> > WASHINGTON -- A
> yearlong experiment with the nation's electric
> > grid could mess
> up traffic lights, security systems and some
> > computers -- and
> make plug-in clocks and appliances like
> > programmable
> coffee makers run up to 20 minutes fast.
> >
> > "A lot of people
> are going to have things break, and they're not
> > going to know
> why," said Demetrios Matsakis, head of the time
> > service
> department at the U.S. Naval Observatory, one of two
> > official
> timekeeping agencies in the federal government.
> >
> > Since 1930,
> electric clocks have kept time based on the rate of
> > the electrical
> current that powers them. If the current slips
> > off its usual
> rate, clocks run a little fast or slow.
> >
> > Power companies
> now take steps to correct it, keeping the
> > frequency of the
> current as precise as possible.
> >
> > The North
> American Electric Reliability Corp., which oversees
> > the U.S. power
> grid, is proposing an experiment that would allow
> > more frequency
> variation without corrections, according to a
> > June 14 company
> presentation obtained by The Associated Press.
> >
> > The test is
> tentatively set to start in mid-July.
> >
> > Tweaking the
> power grid's frequency is expensive and takes a lot
> > of effort, said
> Joe McClelland, head of electric reliability for
> > the Federal
> Energy Regulatory Commission.
> >
> > "Is anyone using
> the grid to keep track of time?" McClelland
> > said. "Let's see
> if anyone complains if we eliminate it."
> >
> > No one is quite
> sure what will be affected. This won't change
> > the clocks in
> cellphones, GPS or even on computers.
> >
> > But wall clocks
> and those on ovens and coffee makers -- anything
> > that flashes
> "12:00" when it loses power -- may be a bit off
> > every second,
> and that error can grow with time.
> >
> > VCRs or DVRs
> that get their time from cable systems or the
> > Internet
> probably won't be affected, but those with clocks tied
> > to the electric
> current will be off a bit, Matsakis said.
> >
> > According to the
> June presentation, East Coast clocks may run up
> > to 20 minutes
> fast over a year, but West Coast clocks are only
> > likely to be off
> by eight minutes. In Texas, it's only an
> > expected speedup
> of two minutes.
> >
> >
> > Read more:
> > http://www.star-telegram.com/2011/06/24/3178359/test-of-electric-grid-could-be.html#ixzz1QOzHwezw
> >
> >
> > <http://www.star-telegram.com/2011/06/24/3178359/test-of-electric-grid-could-be.html#ixzz1QOzHwezw>
> >
> >
> >
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