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.


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers.