Wacky Weekend: NERC to relax power grid frequency strictures
if at xip.at
Sat Jun 25 22:47:07 UTC 2011
>> Generators all stay in sync. Generator owners have expensive devices
>> that sync the phase before the generator is connected to the grid. Once
>> a generator is connected to the gird, it will stay in sync - in fact
>> that is why they have the expensive devices to make sure that they are
>> in sync before they connect them, as if they are not, it will instantly
>> jump to being in sync, which may destroy the generator.
> As a matter of fact, it may destroy the generator, the housing, the building,
> the damn, and more. An out-of-sync generator becomes a motor until it is
> in sync. lt can be a graphic and dramatic event.
Big generator are synchron maschines, as they can generate also reactive
power. If a out of sync synchron maschine is connected to the grid, theres
a big "kawumm" and then the maschine is in sync or dead.
Only the angle between the rotor and the magentic field make the
difference between generator and motor.
A synchron motor can not self-start and only run at fixed grid freuency /
rpm's. A overloaded motor suddenly stops.
Smaller generators are asynchron maschines, that can run faster or slower
than network frequency - ie run as generator or motor - but they always
consume reactive power.
They can self-start.
Synchronising maschines to a grid is not a big problem, the bigger problem
is to syncronise 2 disconnected grids.
Some years ago in europe a grid operator violated the n+1 redundancy rule
as he needed to switch of a big power line over the river "Ems" - to
allow a big ship to leave the shipyard.
The result was a netsplit trough whole europe - a lot of "big"
line-breakers flipped and switched of north-west and south-east power
The whole european grid was split into 3 parts, running at higher and
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