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<DIV><SPAN class=281470421-10042010><FONT color=#0000ff size=2 face=Arial>Re the
60/50Hz business, one of the Gotchas is transformer overheating, or to
expand, A transformer designed for 60Hz has slightly less Iron in it than
the comparable 50Hz one. If you have a "budget transformer" in a item of kit
from a 60Hz source, they would often saturate on 50Hz, get hot and burn out.
Been there, done that!</FONT></SPAN></DIV>
<DIV><SPAN class=281470421-10042010><FONT color=#0000ff size=2
face=Arial></FONT></SPAN> </DIV>
<DIV><SPAN class=281470421-10042010><FONT color=#0000ff size=2 face=Arial>Brian
Summers</FONT></SPAN></DIV>
<BLOCKQUOTE>
<DIV dir=ltr class=OutlookMessageHeader align=left><FONT size=2
face=Tahoma>-----Original Message-----<BR><B>From:</B>
quadlist-bounces@quadvideotapegroup.com
[mailto:quadlist-bounces@quadvideotapegroup.com]<B>On Behalf Of </B>Ted
Langdell<BR><B>Sent:</B> 10 April 2010 19:22<BR><B>To:</B> Quad
List<BR><B>Subject:</B> Re: [QuadList] Mains frequencies, control,similarities
to genlocking<BR><BR></FONT></DIV>
<DIV><BR></DIV>
<DIV>
<DIV>On Apr 10, 2010, at 10:53 AM, Chuck Reti wrote:</DIV><BR
class=Apple-interchange-newline>
<BLOCKQUOTE type="cite">
<DIV>Not documented anywhere I've looked, but wonder if 60Hz might have been
chosen since it correlates with 60sec/min - 60min/hr timekeping.<BR>Did make
it easier to do electric clocks!<BR>-- <BR>Chuck Reti<BR>Detroit
MI<BR></DIV></BLOCKQUOTE></DIV>
<DIV><BR></DIV>
<DIV>Keeping time with motor-based clocks is an interesting situation. See the
link and text below.</DIV>
<DIV><BR></DIV>
<DIV>The process has some elements of pre-framesync Genlock... (Think
rubidium) and since this is Saturday, would have been something networks were
doing with sports events from remote locations.</DIV>
<DIV><BR></DIV>
<DIV>Googling "Genlock Remotes" brought up a 2009 patent application by CISCO,
the data router people in regard to Genlocking remote video sources:</DIV>
<DIV><A
href="http://www.wipo.int/pctdb/en/wo.jsp?WO=2009105593&IA=US2009034598&DISPLAY=STATUS">http://www.wipo.int/pctdb/en/wo.jsp?WO=2009105593&IA=US2009034598&DISPLAY=STATUS</A></DIV>
<DIV><BR></DIV>
<DIV>Genlock and framesyncs turn up in the April "CBS Retirees Ramblings"
here:</DIV>
<DIV><A
href="http://www.cbsretirees.com/blog/blogger.html">http://www.cbsretirees.com/blog/blogger.html</A></DIV>
<DIV><BR></DIV>
<DIV>You'll see a couple of items from Harold Deppe (Sr.,) who was in Maint.
at CBS in NYC and is on the QuadList. We may have the only Father/Son
pair of engineers on a video-related discussion list, for all I know.</DIV>
<DIV><BR></DIV>
<DIV>Back to power for a tad:</DIV>
<DIV><BR></DIV>
<DIV>The section below on Frequency and Load has me wondering whether it would
be practical to monitor the powerline freq., with limit alarms to indicate
that a power "event" like a brownout, load shed or blackout was about to
happen.</DIV>
<DIV><BR></DIV>
<DIV>Ted</DIV>
<DIV><BR></DIV>
<DIV>
<DIV><B><SPAN
style="LINE-HEIGHT: 19px; FONT-FAMILY: sans-serif; FONT-SIZE: 13px; FONT-WEIGHT: normal"
class=Apple-style-span>
<H3
style="BACKGROUND-IMAGE: none; BORDER-BOTTOM-STYLE: none; PADDING-BOTTOM: 0.17em; MARGIN: 0px 0px 0.3em; COLOR: black; FONT-SIZE: 13px; PADDING-TOP: 0.5em; -webkit-background-clip: initial; -webkit-background-origin: initial"><SPAN
style="FONT-WEIGHT: normal" class=Apple-style-span><A
href="http://en.wikipedia.org/wiki/Utility_frequency#Long-term_stability_and_clock_synchronization">http://en.wikipedia.org/wiki/Utility_frequency#Long-term_stability_and_clock</A>_synchronization</SPAN></H3>
<H3
style="BACKGROUND-IMAGE: none; BORDER-BOTTOM-STYLE: none; PADDING-BOTTOM: 0.17em; MARGIN: 0px 0px 0.3em; COLOR: black; FONT-SIZE: 17px; FONT-WEIGHT: bold; PADDING-TOP: 0.5em; -webkit-background-clip: initial; -webkit-background-origin: initial"><SPAN
id=Long-term_stability_and_clock_synchronization class=mw-headline>Long-term
stability and clock synchronization</SPAN></H3>
<DIV style="LINE-HEIGHT: 1.5em; MARGIN: 0.4em 0px 0.5em">Regulation of power
system frequency for timekeeping accuracy was not commonplace until after 1926
and the invention of the <A
style="BACKGROUND-IMAGE: none; COLOR: rgb(0,43,184); TEXT-DECORATION: none; -webkit-background-clip: initial; -webkit-background-origin: initial"
title="Electric clock"
href="http://en.wikipedia.org/wiki/Electric_clock">electric
clock</A> driven by a synchronous motor. Network operators will regulate
the daily average frequency so that clocks stay within a few seconds of
correct time. In practice the nominal frequency is raised or lowered by a
specific percentage to maintain synchronization. Over the course of a day, the
average frequency is maintained at the nominal value within a few hundred
parts per million.<SUP
style="LINE-HEIGHT: 1em; FONT-STYLE: normal; FONT-WEIGHT: normal"
id=cite_ref-16 class=reference><A
style="BACKGROUND-IMAGE: none; WHITE-SPACE: nowrap; COLOR: rgb(0,43,184); TEXT-DECORATION: none; -webkit-background-clip: initial; -webkit-background-origin: initial"
href="http://en.wikipedia.org/wiki/Utility_frequency#cite_note-16"><SPAN>[</SPAN>17<SPAN>]</SPAN></A></SUP> In
the <A
style="BACKGROUND-IMAGE: none; COLOR: rgb(0,43,184); TEXT-DECORATION: none; -webkit-background-clip: initial; -webkit-background-origin: initial"
title="Synchronous grid of Continental Europe"
href="http://en.wikipedia.org/wiki/Synchronous_grid_of_Continental_Europe">synchronous
grid of Continental Europe</A>, the deviation between network phase time
and <A
style="BACKGROUND-IMAGE: none; COLOR: rgb(0,43,184); TEXT-DECORATION: none; -webkit-background-clip: initial; -webkit-background-origin: initial"
class=mw-redirect title=UTC
href="http://en.wikipedia.org/wiki/UTC">UTC</A> is calculated at 08:00
each day in a control center in <A
style="BACKGROUND-IMAGE: none; COLOR: rgb(0,43,184); TEXT-DECORATION: none; -webkit-background-clip: initial; -webkit-background-origin: initial"
title=Switzerland
href="http://en.wikipedia.org/wiki/Switzerland">Switzerland</A>, and the
target frequency is then adjusted by up to ±0.02% from 50 Hz as needed, to
ensure a long-term frequency average of exactly 24×3600×50 cycles per day is
maintained.<SUP
style="LINE-HEIGHT: 1em; FONT-STYLE: normal; FONT-WEIGHT: normal"
id=cite_ref-17 class=reference><A
style="BACKGROUND-IMAGE: none; WHITE-SPACE: nowrap; COLOR: rgb(0,43,184); TEXT-DECORATION: none; -webkit-background-clip: initial; -webkit-background-origin: initial"
href="http://en.wikipedia.org/wiki/Utility_frequency#cite_note-17"><SPAN>[</SPAN>18<SPAN>]</SPAN></A></SUP> In <A
style="BACKGROUND-IMAGE: none; COLOR: rgb(0,43,184); TEXT-DECORATION: none; -webkit-background-clip: initial; -webkit-background-origin: initial"
title="North American Electric Reliability Corporation"
href="http://en.wikipedia.org/wiki/North_American_Electric_Reliability_Corporation">North
America</A>, whenever the error exceeds 10 seconds for the east, 3 seconds for
Texas, or 2 seconds for the west, a correction of ±0.02 Hz (0.033%) is
applied. Time error corrections start and end either on the hour or on the
half hour.<SUP
style="LINE-HEIGHT: 1em; FONT-STYLE: normal; FONT-WEIGHT: normal"
id=cite_ref-18 class=reference><A
style="BACKGROUND-IMAGE: none; WHITE-SPACE: nowrap; COLOR: rgb(0,43,184); TEXT-DECORATION: none; -webkit-background-clip: initial; -webkit-background-origin: initial"
href="http://en.wikipedia.org/wiki/Utility_frequency#cite_note-18"><SPAN>[</SPAN>19<SPAN>]</SPAN></A></SUP><SUP
style="LINE-HEIGHT: 1em; FONT-STYLE: normal; FONT-WEIGHT: normal"
id=cite_ref-19 class=reference><A
style="BACKGROUND-IMAGE: none; WHITE-SPACE: nowrap; COLOR: rgb(0,43,184); TEXT-DECORATION: none; -webkit-background-clip: initial; -webkit-background-origin: initial"
href="http://en.wikipedia.org/wiki/Utility_frequency#cite_note-19"><SPAN>[</SPAN>20<SPAN>]</SPAN></A></SUP> A <A
style="BACKGROUND-IMAGE: url(http://bits.wikimedia.org/skins-1.5/monobook/external.png); PADDING-BOTTOM: 0px; PADDING-LEFT: 0px; PADDING-RIGHT: 13px; BACKGROUND-REPEAT: no-repeat; BACKGROUND-POSITION: 100% 50%; COLOR: rgb(51,102,187); TEXT-DECORATION: none; PADDING-TOP: 0px; -webkit-background-clip: initial; -webkit-background-origin: initial"
class="external text" href="http://www.dynamicdemand.co.uk/grid.htm"
rel=nofollow>dynamicdemand.co.uk/grid - Real-time frequency meter</A> for
power generation in the <A
style="BACKGROUND-IMAGE: none; COLOR: rgb(0,43,184); TEXT-DECORATION: none; -webkit-background-clip: initial; -webkit-background-origin: initial"
title="United Kingdom"
href="http://en.wikipedia.org/wiki/United_Kingdom">United Kingdom</A> is
available online. Smaller power systems may not maintain frequency with the
same degree of accuracy.</DIV>
<DIV style="LINE-HEIGHT: 1.5em; MARGIN: 0.4em 0px 0.5em"><BR></DIV>
<DIV style="LINE-HEIGHT: 1.5em; MARGIN: 0.4em 0px 0.5em"><BR></DIV>
<DIV style="LINE-HEIGHT: 1.5em; MARGIN: 0.4em 0px 0.5em">
<H3
style="BACKGROUND-IMAGE: none; BORDER-BOTTOM-STYLE: none; PADDING-BOTTOM: 0.17em; MARGIN: 0px 0px 0.3em; COLOR: black; FONT-SIZE: 17px; FONT-WEIGHT: bold; PADDING-TOP: 0.5em; -webkit-background-clip: initial; -webkit-background-origin: initial"><SPAN
id=Frequency_and_load class=mw-headline>Frequency and load</SPAN></H3>
<DIV style="LINE-HEIGHT: 1.5em; MARGIN: 0.4em 0px 0.5em">The primary reason
for accurate frequency control is to allow the flow of alternating current
power from multiple generators through the network to be controlled. The trend
in system frequency is a measure of mismatch between demand and generation,
and so is a necessary parameter for load control in interconnected
systems.</DIV>
<DIV style="LINE-HEIGHT: 1.5em; MARGIN: 0.4em 0px 0.5em">Frequency of the
system will vary as load and generation change. Increasing the mechanical
input power to a synchronous generator will not greatly affect the system
frequency but will produce more electric power from that unit. During a severe
overload caused by tripping or failure of generators or transmission lines the
power system frequency will decline, due to an imbalance of load versus
generation. Loss of an interconnection, while exporting power (relative to
system total generation) will cause system frequency to rise. AGC (automatic
generation control) is used to maintain scheduled frequency and interchange
power flows. Control systems in power plants detect changes in the
network-wide frequency and adjust mechanical power input to generators back to
their target frequency. This counteracting usually takes a few tens of seconds
due to the large rotating masses involved. Temporary frequency changes are an
unavoidable consequence of changing demand. Exceptional or rapidly changing
mains frequency is often a sign that an electricity distribution network is
operating near its capacity limits, dramatic examples of which can sometimes
be observed shortly before major outages.</DIV>
<DIV style="LINE-HEIGHT: 1.5em; MARGIN: 0.4em 0px 0.5em">Frequency protection
relays on the power system network sense the decline of frequency and
automatically initiate load shedding or tripping of interconnection lines, to
preserve the operation of at least part of the network. Small frequency
deviations (i.e.- 0.5 Hz on a 50 Hz or 60 Hz network) will
result in automatic load shedding or other control actions to restore system
frequency.</DIV>
<DIV style="LINE-HEIGHT: 1.5em; MARGIN: 0.4em 0px 0.5em">Smaller power
systems, not extensively interconnected with many generators and loads, will
not maintain frequency with the same degree of accuracy. Where system
frequency is not tightly regulated during heavy load periods, the system
operators may allow system frequency to rise during periods of light load, to
maintain a daily average frequency of acceptable accuracy.<SUP
style="LINE-HEIGHT: 1em; FONT-STYLE: normal; FONT-WEIGHT: normal"
id=cite_ref-20 class=reference><A
style="BACKGROUND-IMAGE: none; WHITE-SPACE: nowrap; COLOR: rgb(0,43,184); TEXT-DECORATION: none; -webkit-background-clip: initial; -webkit-background-origin: initial"
href="http://en.wikipedia.org/wiki/Utility_frequency#cite_note-20"><SPAN>[</SPAN>21<SPAN>]</SPAN></A></SUP><SUP
style="LINE-HEIGHT: 1em; FONT-STYLE: normal; FONT-WEIGHT: normal"
id=cite_ref-21 class=reference><A
style="BACKGROUND-IMAGE: none; WHITE-SPACE: nowrap; COLOR: rgb(0,43,184); TEXT-DECORATION: none; -webkit-background-clip: initial; -webkit-background-origin: initial"
href="http://en.wikipedia.org/wiki/Utility_frequency#cite_note-21"><SPAN>[</SPAN>22<SPAN>]</SPAN></A></SUP></DIV></DIV>
<DIV
style="LINE-HEIGHT: 1.5em; MARGIN: 0.4em 0px 0.5em"><BR></DIV></SPAN></B></DIV></DIV><BR>
<DIV>
<DIV>
<DIV>
<DIV>Ted Langdell</DIV>
<DIV>Secretary</DIV>
<DIV></DIV></DIV></DIV></DIV><BR></BLOCKQUOTE></BODY></HTML>