On 06/20/16 22:36, James Knott via talk wrote:
On 06/20/2016 08:31 PM, Michael Galea via talk wrote:
Someone remarked that the accuracy of 60 hz is good, and that
over-frequencies would cancel under-frequencies. I would really doubt
that they could do that to any great degree of accuracy. The grid is
the largest machine on Earth, and there is more than just a single
generator.
You may have heard of the power grid. With the grid, many generators,
in many locations are synchronized with each other. You can be certain
this also involves holding the long term frequency stability to 60 Hz.
O.K. So I should have been clear. I really mean that I doubt that the
grid achieves an average six sigma frequency of 60.00 Hz more than a few
times a day. The thing that I'm not sure that people understand is that
if energy withdrawn from the grid does not continuously and exactly
balance the power injected into it, _the frequency MUST change_. It
fact, since load is continuously changing, so is the frequency.
After all, if the grid is runs at 60.01 Hz for an hour (and it does)
than it is one part on 6000 off, or about 1/2 a second. That's hardly
accurate. At Siemens we achieved 100 nSec accuracy on our IEEE1588
systems and the last time I looked the IEEE was trying to close in on 10 nS.
I also have heard of the power grid, being a microgrid designer and all.
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Michael Galea
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