[time-nuts] Re: Power line timing -- setting a clock

[Peter Reilley]

There are a few things to consider here.   First is that California is 
part of the western grid.
The western grid is certainly not out by more than a few seconds at most 
at any particular
time but it will always make up the slippage to restore the correct 
time. Â  Clocks on the
grid will be correct on average.   There are web sites that track this.

Your particular case:
1)Â Â  At times a section of the grid may break away from the western grid 
because of equipment
failure. Â  During this time the local grid will be working to restore 
the local grid stability.
They wont worry about maintaining the correct time. Â  Eventually they 
will reconnect to
the western grid. Â  You may not notice this.

2)Â Â  Your local circuit will have circuit breakers at substations. A 
fault on your local circuit,
like a tree branch touching the line, will cause the breaker to open. Â  
Many breakers have
an auto-close feature. Â  After a certain time, generally just a few 60 
Hz cycles, they will
re-close automatically.   They will repeat this a certain number of 
times and then remain
open.   You may notice this as the lights flickering.   During this time 
you will loose
a few cycles.   A non auto-close breaker will stay open until an 
operator manually closes
it.

There are probably a few other scenarios where a section of the grid may 
loose correct
time keeping but the main grid will always strive to be correct on average.


On 3/22/2024 9:52 PM, Larry McDavid via time-nuts wrote:
> I believe the local electric generation utilities have largely 
> divested themselves of maintaining an accurate 60 Hz mains frequency, 
> both instantaneously and total cycles per day.
>
> I know that my home clocks that count cycles from the power lines no 
> longer show accurate time. In fact, compared to GPS time, I often see 
> more than 5 seconds error in just a week's time, here in Southern 
> California.
>
> If I don't reset those power-line (no crystal reference) clocks, I've 
> surely seen errors of 30 seconds accumulate. That holds true for 
> stand-alone power-line clocks and the clocks in microwave ovens and 
> kitchen appliances. But, all those clocks in appliances roll the 
> minute digit about simultaneously, when the time had been set 
> accurately to the second. This indicates the various appliance clocks 
> are counting cycles accurately, but the cycle count per day varies and 
> is not well maintained.
>
> All those appliances loose the time setting when there is a power 
> failure. It is probably mild OCD, but I try to set all those clocks 
> using a GPS clock and to the second. I used to rely on a 
> mains-frequency clock for A/V timing but now I use a GPS Clock by Nick 
> Sayer, sold on Tindie; it displays time to tenth-second. This GPS time 
> is closely tracked by my Heathkit WWV (not WWVB) Most Accurate Clock; 
> a few days after carefully setting a mains frequency appliance clock, 
> the time is very typically seconds off GPS time.
>
> -Best wishes,
>
> Larry McDavid W6FUB
> Anaheim, California (SE of Los Angeles, near Disneyland)
>
> On 3/21/2024 3:13 AM, Hal Murray via time-nuts wrote:
>>
>> All sorts of gear uses the power line to drive their clock.
>>
>> I picture that a corner of the control room has 2 clocks, one 
>> tracking UTC and
>> the other tracking the power grid.  The difference between that pair 
>> feeds
>> into their complicated control system that includes some sort of PLL 
>> that
>> keeps the power line clock
>> tracking UTC.
>>
>> Is there any way to get a copy of their power line clock?  So I can 
>> set my
>> power line clocks to a similar offset so they will have a better 
>> chance of
>> being right tomorrow after they correct for today's offset?  I'm not 
>> looking
>> for microseconds, just microwave-setting accuracy.
>>
>> Do they have a graph showing the offset for the last week or month?  
>> I can
>> line that up with my graphs.
>>
>>
>>
>> Here is a graph from Feb/Mar 2024 where it drifted a minute over 2 
>> weeks.
>> Â Â  https://www.glypnod.com/TimeNuts/60Hz/60Hz-2024-FebMar.png
>> That's 4 seconds per day.
>>
>>
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