On 6/24/11 9:22 PM, Jim Lux wrote:
On 6/24/11 8:20 PM, Chris Albertson wrote:
On Fri, Jun 24, 2011 at 5:59 PM, gary<[email protected]> wrote:
I use a Logitech Squeezebox radio in the bedroom. Network timed!
I don't see how they connect grid that aren't totally in sync.
The big long distance transmission lines are high voltage DC.
Most aren't. I don't recall the exact number, but less than half of the
power flowing down the Pacific coast is carried by DC. (3-4 GW on the DC
link.. 3000A at 1 MV..yeah, baby... that's a power line)
Just looked it up..4.8GW on AC, 3.1GW on DC.
Stabilizing the 3 AC links is quite the chore.. (my dad's PhD advisor
was involved in this.. it was one of the very early uses of computers,
calculating loads and sources and stabilizing the networks)
If you've ever seen that video of the huge "drawn arc" at a electrical
substation during a test (the arc must be 50 feet long, at least), that
was shot at Lugo substation, which is where the 500kV AC links terminate.
The advent of GPS timing apparently made the whole controlling the
network much easier, because it allowed high performance measurements of
the phase at the ends of the links, which can then factor in to controls
on things like synchronous condensors and the "throttle" on power
plants. When they started to move away from mercury pool to solid state
thyristors, that made life even easier. There are some enormous
cycloconverters to do small frequency/phase changes.
I find the scale of this stuff amazing, and the level of control needed
to keep it all working is quite impressive. Sure, keeping measurement
systems stable to 1 part in 1E15 over 20 minutes is a challenge... but
at least all that stuff fits in one rack.
Doing 1 degree kind of control on gigawatts of power is something I find
really impressive.
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