<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">A max of 20 minutes error per year (as stated in the article)<br>equates to an error of 0.228%.<br><br>Whether grid-tied inverters stay on line or not depends on<br>the ultimate range of the frequency excursions permitted<br>during the tests. UL1741 limits are 59.3 to 60.5 Hz for<br>fixed frequency settings. The cumulative error shown<br>above is well within those bounds. 59.3 Hz = -1.16%;<br>60.5 Hz is +0.83%.<br><br>However, I could see cases where they may allow 60.6 Hz<br>one day and 59.4 Hz the next. The overall net difference<br>would be zero for a frequency-dependent clock - but a<br>grid-tied inverter would spend the first day of this example<br>totally offline.<br><br>This would have to be a grid-wide frequency difference,<br>else they'd end up with some seriously large power flows<br>from one part of the grid to another,
with potentially disastrous<br>results.<br><br>It will be interesting to see how they handle this.<br><br>Thanks for the post.<br><br>Dan<br><br><br>--- On <b>Sun, 6/26/11, bob ellison <i><reellison@gmail.com></i></b> wrote:<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"><br>From: bob ellison <reellison@gmail.com><br>Subject: Re: [RE-wrenches] National grid hertz adjustment<br>To: "'RE-wrenches'" <re-wrenches@lists.re-wrenches.org><br>Date: Sunday, June 26, 2011, 6:40 PM<br><br><div id="yiv911515806"><style><!--
#yiv911515806
_filtered #yiv911515806 {font-family:Calibri;panose-1:2 15 5 2 2 2 4 3 2 4;}
_filtered #yiv911515806 {font-family:Tahoma;panose-1:2 11 6 4 3 5 4 4 2 4;}
_filtered #yiv911515806 {font-family:Consolas;panose-1:2 11 6 9 2 2 4 3 2 4;}
#yiv911515806
#yiv911515806 p.yiv911515806MsoNormal, #yiv911515806 li.yiv911515806MsoNormal, #yiv911515806 div.yiv911515806MsoNormal
{margin:0in;margin-bottom:.0001pt;font-size:12.0pt;font-family:"serif";color:black;}
#yiv911515806 a:link, #yiv911515806 span.yiv911515806MsoHyperlink
{color:blue;text-decoration:underline;}
#yiv911515806 a:visited, #yiv911515806 span.yiv911515806MsoHyperlinkFollowed
{color:purple;text-decoration:underline;}
#yiv911515806 p
{margin-right:0in;margin-left:0in;font-size:12.0pt;font-family:"serif";color:black;}
#yiv911515806 pre
{margin:0in;margin-bottom:.0001pt;font-size:10.0pt;font-family:"Courier New";color:black;}
#yiv911515806 span.yiv911515806HTMLPreformattedChar
{font-family:Consolas;color:black;}
#yiv911515806 span.yiv911515806EmailStyle19
{font-family:"sans-serif";color:#1F497D;}
#yiv911515806 p.yiv911515806byline, #yiv911515806 li.yiv911515806byline, #yiv911515806 div.yiv911515806byline
{margin-right:0in;margin-left:0in;font-size:12.0pt;font-family:"serif";color:black;}
#yiv911515806 p.yiv911515806avgcert, #yiv911515806 li.yiv911515806avgcert, #yiv911515806 div.yiv911515806avgcert
{margin-right:0in;margin-left:0in;font-size:12.0pt;font-family:"serif";color:black;}
#yiv911515806 span.yiv911515806EmailStyle23
{font-family:"sans-serif";color:black;}
#yiv911515806 .yiv911515806MsoChpDefault
{font-size:10.0pt;}
_filtered #yiv911515806 {margin:1.0in 1.0in 1.0in 1.0in;}
#yiv911515806 div.yiv911515806WordSection1
{}
--></style><div class="yiv911515806WordSection1"><p class="yiv911515806MsoNormal"><font color="black" face="Calibri" size="4"><span style="font-size: 14pt; font-family: "sans-serif"; color: black;">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.</span></font></p><p class="yiv911515806MsoNormal"><font color="black" face="Calibri" size="4"><span style="font-size: 14pt; font-family: "sans-serif"; color: black;"> </span></font></p><p class="yiv911515806MsoNormal"><font color="black" face="Calibri" size="4"><span style="font-size: 14pt; font-family: "sans-serif"; color: black;">Bob Ellison</span></font></p><p class="yiv911515806MsoNormal"><font color="black" face="Calibri" size="4"><span style="font-size: 14pt; font-family: "sans-serif";
color: black;"> </span></font></p><div><div style="border-right: medium none; border-width: 1pt medium medium; border-style: solid none none; border-color: rgb(181, 196, 223) -moz-use-text-color -moz-use-text-color; padding: 3pt 0in 0in;"><p class="yiv911515806MsoNormal"><b><font color="black" face="Tahoma" size="2"><span style="font-size: 10pt; font-family: "sans-serif"; color: windowtext; font-weight: bold;">From:</span></font></b><font color="black" face="Tahoma" size="2"><span style="font-size: 10pt; font-family: "sans-serif"; color: windowtext;"> re-wrenches-bounces@lists.re-wrenches.org [mailto:re-wrenches-bounces@lists.re-wrenches.org] <b><span style="font-weight: bold;">On Behalf Of </span></b>Roy Butler<br><b><span style="font-weight: bold;">Sent:</span></b> Sunday, June 26, 2011 1:45 PM<br><b><span style="font-weight: bold;">To:</span></b> RE-wrenches<br><b><span style="font-weight: bold;">Subject:</span></b> Re:
[RE-wrenches] National grid hertz adjustment</span></font></p></div></div><p class="yiv911515806MsoNormal"><font color="black" face="Times New Roman" size="3"><span style="font-size: 12pt;"> </span></font></p><p class="yiv911515806MsoNormal"><font color="black" face="Times New Roman" size="3"><span style="font-size: 12pt;">I saw this as well, came over the AP news wire on Friday, June 24th.<br>I've been trying to figure out what they hope to gain by allowing more<br>frequency variation.....puzzling at best!<br><br></span></font></p><pre><font color="black" face="Courier New" size="2"><span style="font-size: 10pt;">Roy Butler</span></font></pre><pre><font color="black" face="Courier New" size="2"><span style="font-size: 10pt;">NABCEP Certified Solar PV Installer®</span></font></pre><pre><font color="black" face="Courier New" size="2"><span style="font-size: 10pt;">NYSERDA eligible PV & wind installer</span></font></pre><pre><font color="black"
face="Courier New" size="2"><span style="font-size: 10pt;">Four Winds Renewable Energy, LLC</span></font></pre><pre><font color="black" face="Courier New" size="2"><span style="font-size: 10pt;">8902 Route 46</span></font></pre><pre><font color="black" face="Courier New" size="2"><span style="font-size: 10pt;">Arkport, NY 14807</span></font></pre><pre><font color="black" face="Courier New" size="2"><span style="font-size: 10pt;">607-324-9747</span></font></pre><pre><font color="black" face="Courier New" size="2"><span style="font-size: 10pt;"> </span></font></pre><pre><font color="black" face="Courier New" size="2"><span style="font-size: 10pt;"><a rel="nofollow" target="_blank" href="http://www.four-winds-energy.com">www.four-winds-energy.com</a></span></font></pre><pre><font color="black" face="Courier New" size="2"><span style="font-size: 10pt;"> </span></font></pre><pre><font color="black" face="Courier New" size="2"><span
style="font-size: 10pt;">Although no trees were killed in the sending of this message, </span></font></pre><pre><font color="black" face="Courier New" size="2"><span style="font-size: 10pt;">a large number of electrons were terribly inconvenienced.</span></font></pre><pre><font color="black" face="Courier New" size="2"><span style="font-size: 10pt;"> </span></font></pre><pre><font color="black" face="Courier New" size="2"><span style="font-size: 10pt;"> </span></font></pre><p class="yiv911515806MsoNormal"><font color="black" face="Times New Roman" size="3"><span style="font-size: 12pt;"><br>On 6/26/2011 1:31 PM, North Texas Renewable Energy Inc wrote: </span></font></p><div><p class="yiv911515806byline"><font color="black" face="Arial" size="3"><span style="font-size: 12pt; font-family: "sans-serif";">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?</span></font></p><p class="yiv911515806byline"><font color="black" face="Arial" size="3"><span style="font-size: 12pt; font-family: "sans-serif";">Jim Duncan</span></font></p><p class="yiv911515806byline"><font color="black" face="Arial" size="3"><span style="font-size: 12pt; font-family: "sans-serif";">By Seth Borenstein The Associated Press</span></font></p></div><blockquote style="margin-top: 5pt; margin-right: 0in; margin-bottom: 5pt;"><p><font color="#1f497d" face="Calibri" size="2"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);">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.</span></font></p><p><font color="#1f497d" face="Calibri" size="2"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);">"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.</span></font></p><p><font color="#1f497d" face="Calibri" size="2"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);">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.</span></font></p><p><font color="#1f497d" face="Calibri" size="2"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);">Power
companies now take steps to correct it, keeping the frequency of the current as precise as possible.</span></font></p><p><font color="#1f497d" face="Calibri" size="2"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);">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.</span></font></p><p><font color="#1f497d" face="Calibri" size="2"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);">The test is tentatively set to start in mid-July.</span></font></p><p><font color="#1f497d" face="Calibri" size="2"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);">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.</span></font></p><p><font color="#1f497d" face="Calibri" size="2"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);">"Is anyone using the grid to keep track of time?" McClelland said. "Let's see if anyone complains if we eliminate it."</span></font></p><p><font color="#1f497d" face="Calibri" size="2"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);">No one is quite sure what will be affected. This won't change the clocks in cellphones, GPS or even on computers.</span></font></p><p><font color="#1f497d" face="Calibri" size="2"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);">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.</span></font></p><p><font color="#1f497d" face="Calibri" size="2"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);">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.</span></font></p><p><font color="#1f497d" face="Calibri" size="2"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);">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. </span></font></p><p class="yiv911515806MsoNormal"><font color="black" face="Calibri" size="2"><span style="font-size: 11pt; font-family: "sans-serif";"><br>Read more: <a rel="nofollow" target="_blank"
href="http://www.star-telegram.com/2011/06/24/3178359/test-of-electric-grid-could-be.html#ixzz1QOzHwezw"><font color="#003399"><span style="color: rgb(0, 51, 153);">http://www.star-telegram.com/2011/06/24/3178359/test-of-electric-grid-could-be.html#ixzz1QOzHwezw</span></font></a></span></font></p><p class="yiv911515806MsoNormal"><font color="black" face="Calibri" size="2"><span style="font-size: 11pt; font-family: "sans-serif";"><a rel="nofollow" target="_blank" href="http://www.star-telegram.com/2011/06/24/3178359/test-of-electric-grid-could-be.html#ixzz1QOzHwezw"><font color="#003399"><span style="color: rgb(0, 51, 153);"><br></span></font></a></span></font></p></blockquote></div></div></blockquote></td></tr></table>