rickman wrote:
Daniel60 wrote on 12/5/2017 8:13 AM:
James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:37:53 -0000, rickman wrote:

On 3/17/2017 10:28 PM, James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:01:09 -0000, rickman wrote:

On 3/17/2017 8:02 PM, James Wilkinson Sword wrote:
https://en.wikipedia.org/wiki/Nation..._2008_incident





Can someone explain why a power station should disconnect due to
detecting a small frequency drop?* Would this not make things worse?

When I read that article, it said that this was no longer the
rule.* In
fact, the problem was caused by some smaller generation facilities
tripping off the grid when the current rule was to *not* trip at that
point.* They were running old software.

I assume that not entirely unlike blowing a fuse, the general rule
is to
separate portions of the grid when things are going wonky.* I can
only
imagine that there could be parts of the grid damaged if the flow of
power is not well regulated.

Agreed.* But if a power station detects the grid is at a slightly low
frequency, why on earth would it be a good idea to cease generating?
The low frequency was presumably caused by a lack of input, making the
power stations throughout the country labour a little and slow down.
Taking more power stations off the grid will exacerbate the problem.

Did you read what I wrote?* That is not the rule.

Yes, you said they seperate if the frequency is wrong.* Which is not a
good idea is it?

Coming in very, very, late to this discussion, but .....

It would seem to me that if the freqs that two generators were
operating at
were slightly different, then the instantaneous voltages being
produced by
the two generators would also be different, so one generator would be
supplying power to the "real" load *and* to the slower generator!

Keep in mind that the power lost in transmission is not zero.* A
sufficiently small difference in phase (rather than frequency which
would result in phase creeping) would simply result in a smaller or
larger loss in the transmission.* Given the difference in phase of
voltage on the load this would result in current leading or lagging the
generated voltage and result in a torque that would speed the lagging
generator and slow the leading generator since the back EMF is created
by the current.

If one generator was running at 50Hz and the other was running at, say,
49.95Hz, then every1,000 cycles or so, the two waveforms would be
exactly in phase ..... for an infinitesimally (??Sp) small time!!

If the two generators were both running at 50Hz but one lagged the other
by some degrees (your second case, and not the one I originally
considered) could possibly be as you mentioned.

Daniel