My father was protection design engineer for the largest (population)
grid in Australia.  It's therefore an area of interest for me.  He
retired around 1990, I think.

On Mon, Nov 17, 2003 at 04:30:39PM -0000, Hulatt, Jon wrote:
> Every generator set that contributes to the grid has to be running in
> perfect frequency and phase with the grid. Therefore, if immense loading on
> the grid would slow down the frequency, it must correspondingly slow down
> all of the connected generator sets and in turn, the turbines or engines
> that drive them. Which seems odd.

I thought having more load than generating capacity caused an increase in
frequency.  But I may have been confusing effect with control method.

> Furthermore, since "anyone" can contribute supply to the grid, and can only
> connect their generator set when it is perfectly in phase with the grid,
> then how on earth can someone realistically expect to get their generator in
> phase with a significantly changing frequency or phase?

They connect it with a device that can track the change and adjust their
generator set.  As you can imagine, if the set was connected with the
wave following the grid, the set would behave as a load.

I've heard stories of early phase detectors that could display zero for
180 degrees out of phase condition.  Generators leaping from turbine
housing.  But if I recall correctly, they were American stories.  ;-)

> Although, I could be getting the wrong end of the stick. Perhaps it's the
> frequency of the grid (hence, the inertia of the spinning generators /
> turbines / flywheels) that provides the "buffer" of energy needed to cope
> with continually fluctuating supply and demand. Perhaps therefore, short
> term frequency variance is "designed in".

In the control room (Carlingford) when I was there, was a frequency
counter with several digits after the decimal place, an atomic or radio
synchronised clock, and a 50Hz line frequency driven "domestic" clock,
showing hours, minutes and seconds.

Grid frequency was allowed to shift around within certain constraints,
subject to the load and generating capacity.  But once things were
stable, the main frequency control would be adjusted to bring the clock
back into alignment with real-time.  The aim was to provide very
accurate long term (many hours) average frequency.

One should be able to set a line frequency bedside alarm clock to the
second using the national radio's time signal, and then have it wake
with the theme introduction to the News at 6AM the next day.

Disclaimer: this was in the eighties, before the government sold the
operation as a business.  My memory needs refreshing.

--
James Cameron    mailto:quozl@us.netrek.org     http://quozl.netrek.org/

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