[time-nuts] A Research Proposal

[Bill Hawkins]

Group,

We've discussed this before, but maybe it needs to be said again.

Line frequency is not constant.   There is no master PLL.  Approximate frequency is maintained by a central power dispatching office in each of the four (?) regions tied together by their power distribution grid.  The dispatcher's goal is to create the same number of cycles of AC each day.  IIRC, power is bought and sold by the number of cycles generated.   As the daytime load increases, the generators slow down a bit.  Note that it is not possible for each generating station to control its frequency, as that would not be stable.  Instead, the dispatcher asks various plant operators to generate more or less steam (or water flow) in order to increase the frequency.  When the load drops at night, the generators speed up a bit, and steam has to be reduced. At the end of the day, so to speak, the number of cycles generated is very nearly equal to the number generated if the line frequency had been steady at 60 (or 50) cycles per second.  Synchronous clocks stay accurate although they may be off by a few seconds as dispatchers scramble to get enough steam to keep up.

So yes, you can get phase data within a region but you must compensate timing data as the frequency varies.

The regions are connected to each other for purposes of power sharing with DC transmission lines.  These use inverters to convert between AC and DC. The AC frequency is controlled by the grid that it is tied to.  Phase angle can be changed to change the amount and direction of the power transferred.

So no, you can't compare data from different regions, unless you want to know which way DC power is flowing.

I hope this was informative.

Bill Hawkins


On Thu, Jul 4, 2019, at 2:00 PM, Andy Backus wrote:
> Historically, and even today, the steady frequency of AC power has been 
> used for timekeeping.  So there may be interest here in the following 
> research proposal:
> 
> Within a given power distribution grid, several observers as widely 
> separated geographically as possible, time stamp the first two zero 
> crossings of the power line after each UTC second – over the course of 
> 24 hours (86,400 pairs of data).
> 
> Popularly conceived, all the components of a power distribution grid 
> are phase locked – though, of course, power is taken in and out by 
> varying degrees of lead or lag.  Frequency is maintained by a constant 
> balancing act between load and generation.
> 
> Typical power distribution grids, however, are sized on a scale of 
> thousands of miles.  “Locking phase,” then, is problematic simply on 
> the basis of the limits of information transmission rate.  Even at c, 
> every 1000 miles takes 5 ms, which represents a third to a quarter of 
> the period of the AC power waveform.
> 
> Many interesting phenomena might result from that reality, which 
> suggests a certain constrained flexibility over large distances – 
> almost as if the system is like a large lake of viscous liquid.  When 
> there are local disturbances such as rapid load changes or sudden 
> generation adjustments, for example, it is quite possible harmonic 
> ripples could be propagated through the system.
> 
> Such effects could be observed by comparing phase data across 
> significant distances within a distribution grid.
> 
> Andy Backus
> Bellingham, WA
> USA
> 
> ________________________________
> From: time-nuts <time-nuts-bounces at lists.febo.com> on behalf of Thomas 
> D. Erb <tde at electrictime.com>
> Sent: Thursday, July 4, 2019 5:23 AM
> To: time-nuts at lists.febo.com
> Subject: Re: [time-nuts] 60 Hz frequency and phase measurement
> 
snip
> I had a recent tour of a power station - the operators had no idea the 
> output was synchronized to a time standard - they just synchronize with 
> the local grid.

> 
> Thomas D. Erb
> p:        508-359-4396
> f:        508-359-4482
> a:        97 West Street, Medfield, MA 02052 USA
> e:         tde at electrictime.com
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