The reason electric generators join the system at the proper frequency is because the system will rip a generator out of its moorings if it is rotating too fast or too slow. There is much more energy in the system as conveyed by a high power transmission line than there is in a single generator. Frequency synchronization is a defensive measure. It is all done with meters at the tie-line point or with readings telemetered to a central control center.
Charles Elliott > -----Original Message----- > From: questions-bounces+elliott.ch=verizon....@lists.ntp.org > [mailto:questions-bounces+elliott.ch=verizon....@lists.ntp.org] On > Behalf Of unruh > Sent: Thursday, February 23, 2012 4:41 PM > To: questions@lists.ntp.org > Subject: Re: [ntp:questions] GPS Jammers in Use by Criminals - Warping > Time for Fraud Suggested > > On 2012-02-23, Richard B. Gilbert <rgilber...@comcast.net> wrote: > > On 2/22/2012 5:16 PM, David Woolley wrote: > >> An article in the Metro, the free morning paper on the London > >> commuter transport network, suggests that criminals may be using GPS > >> jamming equipment to warp the time on financial systems to allow the > >> commission of fraud. > >> > > GPS is not the only source of time! > > > > In the U.S. 60 cycle Alternating Current is the standard and the > > source of time. It's not going to give you the nanoseconds but very > > few people could even explain what a nanosecond is let alone needing > > nanosecond resolution. > > It is neither a standard nor is it a "source of time". The requirement > is that the phase of the 60Hz be the same across the country, so > electricity can be traded between generation facilities without one > source shorting out the other. That does not require frequency > accuracy, just that the frequency of all the generators be the same and > the phase difference be less than a ms or so. > > Because the easiest way to ensure phase coherence is to demand > frequency coherence and use a standard, like UTC, as a reference, they > do tend to be close. But the requirement is phase coherence not time > accuracy and the latter will be jettisoned in favour of the former. > > > > >> Although I can't find the source of that article, the BBC has an > >> article, presumably from the same underlying source, addressing > >> another point in that that article, that GPS jammers are > increasingly > >> being used to defeat GPS based car tracking systems. > > > > If anyone wants to track my car's location, you're welcome. And I > > hope that no one dies of boredom! > > > ><snip> > > _______________________________________________ > questions mailing list > questions@lists.ntp.org > http://lists.ntp.org/listinfo/questions _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
