[LEAPSECS] Schedule for success

Poul-Henning Kamp phk at phk.freebsd.dk
Mon Dec 22 07:15:33 EST 2008

In message <000301c963cd$0476cd70$0d646850$@com>, "christopher hoover" writes:

>> Everything relating to the power-grid load/supply distribution,

>> that means control of power-plants, transformers and switching

>> stations.


>The power grid does not necessarily require (fully) isochronous operation.


>Microgrid research (e.g., Piagi and Lasseter) has indicated practical ways

>to do autonomous control using only local information. This work has grown

>particularly important as we increase distributed generation capacity and

>leverage the efficiency of CHP/CCHP/cogeneration.

The magnitude of energy spikes going the wrong direction in a matter
of milliseconds have everybody doing the "let somebody else try this,
with _their_ transformers and generators" shuffle.

It is well known and documented that the current (HVAC) strategy
does not work and the increasing distances between power generator
and consumer dictates HVDC systems.

But so far all HVDC has been point to point and very few experiments
have been done with "busing" where you have multiple entry/exit
points on a HVDC grid.

The main problem with HVDC is that the lack of zero-crossings means
that it is terribly hard to open a circuit under load.

To put matters in perspective: Many power plants today have the
"fuse of last resort" protecting their kit. This consists of
approx 3 meters of copper rail with a couple of bars of dynamite
wrapped around the middle, often wired to automatically blow
above a certain fault current.

The secondary problem with HVDC is that the lack of inductive
components and dV in the grid makes faults propagate close to ten
times faster and fault currents build up to values five times higher.

And finally, blowing out a big-ass transformer is bad money news,
but blowing all the thyristors or IGBTs in a AC/DC conversion plant
is _really_ bad money news.

About the only thing people can agree on, is that "coordinated
switching" requires synchronization to better than 10% of period,
which everybody translates to a one microsecond requirement.

One switchpoint being 1 second off because the hadn't heard about
the leap second could make for the best and most new years eve
fireworks you can imagine.

Ohh, and the reason they need UTC ? Billing.


Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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