On May 1, 7:50*pm, The Natural Philosopher
wrote:
On 01/05/13 17:42, John Williamson wrote:







harry wrote:

Better to work the system on voltage fluctuations than frequency.
If the voltage drops, reduce the load by what ever means you decide
on. When it rises the cut off loads can be reconnected.
Much easier.

Yes, but much less effective.

There are a *lot* of places in this Country where voltage varies
wildly even under normal load conditions, and there are a *lot* of
automatic tap changers in substations and at the top of poles which
try to maintain the correct voltage. These would all have to be either
adjusted or overridden to do what you suggest. On the other hand, the
frequency is generally stable except under conditions of grid
overload, and a frequency drop is easily detected with very few false
alarms.

If you plot mains frequency against time with enough resolution, you
can actually work out when popular TV programmes end by the frequency
dip as millions of kettles are turned on. You'd be hard pushed to do
the same by checking the Grid voltages.

local voltage tells you what you or your street is doing. Frequency
tells you what the whole GRID is doing.

The street is what you need to know about.
The frequency business is ********.

If the voltage falls locally future smart meters could "report back"
and turn a few local wind turbines/PV panels on. ;-)

Or maybe some of these as they become common.
http://www.ecpower.co.uk/english/
(Co-generation)

Or maybe stored power in electric vehicle batteries.

This is what Smart Grid technology is about.
All these PV panels/small wind turbines will need controlling at some
point in the future. As they become more numerous, they can't be left
running uncontrolled as at the moment.

And they will also cut off non essential thing if needed.

Anybody who co-operates with all this will be rewarded. (As with PV/
other renewable power at the moment)

The important bit will be to monitor all this an there will be
financial inducements for people to do this. ie different prices for
importing/exporting power at different times.

We ain't seen nothing yet.