On 4/20/11 9:39 AM, Poul-Henning Kamp wrote:
In message<4daf0b0d.4080...@earthlink.net>, Jim Lux writes:
I found this in a generator interconnection agreement:
This frequency response control shall, when enabled at the direction of
CAISO, continuously monitor the system frequency and automatically
reduce the real power output of the Asynchronous Generating Facility
with a droop equal to a one-hundred (100) percent decrease in plant
output for a five (5) percent rise in frequency (five (5) percent droop)
above an intentional dead band of 0.036 Hz
Neither that text nor any other I have been able to find, guarantee
that the integral (= long term average) of the frequency will
converge on 60Hz, only that the instantaneous frequency will stay
in an particular range.
There's the "integrated time shall not deviate more than 2 seconds from
actual" sort of requirement. I don't know what the integration interval
on that is, but I think it implies that in any given day, there will be
60*86400 cycles plus minus 120 cycles. And that further, a sequence of
+120, +120, +120 on successive days wouldn't be allowed.
I also noted that they seem to want the "corrections" to be done at the
top of the hour (they speed up or slow down the 60 Hz until they're
realigned).. I don't know, off hand, how much difference that would
make in power flow (say they adjust by 0.01 Hz... over 1 second, that's
a phase shift of 3.6 degrees, which is pretty big in the power
management world)
tvb's data at http://leapsecond.com/pages/mains/ [...]
That data confirms what I said: Maybe if you average over a couple
of months, but the practical problems related to doing that are
enormous.
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