[time-nuts] No more 60Hz! TEC Elimination

Jim Lux jimlux at earthlink.net
Sat Jun 25 04:18:23 UTC 2011


On 6/24/11 6:47 PM, Hal Murray wrote:
>> I don't see how they connect grid that aren't totally in sync.
>
> Each grid is in sync with itself.  In the US, there are several grids.  They
> aren't connected except maybe by DC lines.
>
>
all of the US is interconnected, except for Texas.

That said there's not much interchange across the intermountain West 
(e.g. not much power is run from the Pacific coast across Utah and 
Colorado).  This is why the Pacific coast will have less variation than 
the east coast.

As others have pointed out, power flows are done by changing the 
relative phase of the two zones.  You can either keep the power flows 
carefully "net zero" or you can keep the frequency the same, but not 
both. So what they do is try to have times when they don't need to flow 
power, so they can "open the switch" on the intertie, change the 
frequency for a while to get back to where they think they should be, 
then carefully resynchronize and reclose the switch.

There are remarkably few DC interties to help.  the big Pacific DC 
intertie is done not so much to flow power both ways (it's almost 
entirely southbound), but to make it even feasible to send power several 
thousand km.  The alternate (AC) path down through the middle of 
California is a apparently a bear to keep stable, and transients can 
take tens of hours to die out.

After all, that transmission line is starting to be a significant 
fraction of a wavelength at 60 Hz. (lambda in free space is 5000km.. 
prop velocity on a power line is quite a bit slower)




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