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

J. Forster jfor at quik.com
Sat Jun 25 04:34:29 UTC 2011

Mostly correct, but:

> 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.

When two parts of the system are interconnected, the frequency must be the
same, except very briefly when the relative phase is being changed. The
direction and size of the power flow over the link is controlled by the
differential phase.

> 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.

And adjust the voltages to be equal. Bth phase and voltage have to be
equal to avoid transients.

> 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.

The transients are very lightly damped, unless the generator rotors have
quadrature windings with active controls.



> 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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