The Audiophoolery Thread.

[mole42uk]

And perhaps another reference for triple redundancy. I’m currently residing only 30 miles from a large nuclear power station, they must have a suitable frequency reference to lock on to.

[mark_in_manc]

Originally Posted by mole42uk

And perhaps another reference for triple redundancy. I’m currently residing only 30 miles from a large nuclear power station, they must have a suitable frequency reference to lock on to.

What's the half-life of unobtanium?

[Analogue man]

Originally Posted by mark_in_manc

What's the half-life of unobtanium?

These days about the same as the full life!

[Radio Wrangler]

Originally Posted by mole42uk

they must have a suitable frequency reference to lock on to.

Nope. Each power station turbine/generator is quite small compared to the size of the whole grid. Each generator's speed is brought up to get its output matching the frequency of the grid before it is connected. It is allowed to drift slightly and the relative phase between the generator and the grid is watched on an instrument called a Synchroscope, and when the phases align, someone drops the breaker in. Get the phase wrong and there will be a shock load. Much error and there will be dramatic damage. This is genuinely scary with teh forces and kinetic energies involved. There are automated phase control systems in some places but there are still plenty of multi-megawatt things like hydro stations where syncing is done by humans. There are videos on youtube of generator syncing. The tredidation can come across quite well.

Once on-line, the generator acts like it was mechanicall linked to all the other synchronous generators on the grid, and all the synchronous motors and all their moments of inertia!

If you put more steam or water (as appropriate) on your turbine, it tries to speed up the entire grid. It won't get far, of course, but it will start putting more power into the grid and supporting more of the load. Grid frequency is allowed to wander a little, it acts as a signal to command idle generators to come on line and help with the load when the frequency is low. So a generator needs a modest accuracy frequency standard to monitor the grid frequency and tell it when it needs to go to work and when it can go off line to economise.

If every generator's frequency was independently controlled by its own frequency standard, chaos would result and pretty much everything would destroy itself.

The audiophools worried sick about whether the mains cables on their gear are expensive/magical enough are clueless about what they're connecting into

David

[Ted Kendall]

Unlike so many things that have come up on this thread, that's actually dead interesting!

[julie_m]

Switching a generator into the grid is analogous to engaging a clutch to couple its own shaft to the shaft of a much more powerful machine -- and with the added wrinkle that each shaft has a fine line engraved lengthwise for a portion of its length, and these must also line up perfectly at the moment when the clutch engages. The instrument used for ensuring perfect phasing is called a synchroscope; and shows you, on a large dial for the sake of precision, the phase shift between the two generator outputs -- which will be constant if both are at the same frequency. So you aim to get your speed almost right, so the synchroscope pointer is rotating very slowly (at the difference between shaft speeds) and then close the switch when it is pointing straight up.

When moving things get joined together, momentum is always conserved, even if some kinetic energy has to be dissipated somehow -- whether that be in the form of heat, sound, work done deforming things plastically or still kinetic energy, only no longer attached to the original moving objects .....

If the two things are already moving at the same speed when they become joined together, though, there is no net change in momentum, and no forces acting between them at the moment of contact.

Think of it as stepping from one moving train onto another one. When the synchroscope pointer is stationary, the speeds are matched; and when it's pointing straight up, there is something next to you to step on.

[G6Tanuki]

The days of someone watching a synchroscope and deciding when to throw the switch are long gone. These days it's all done under supervision of a bunch of rather intelligent electronics that can get the alternator to a degree of phase-offset-error unimaginable and unachievable to anything manual.

[A friend works for RWE, managing a 1440 MW CCGT plant. He does most of this from his home-office rather than being on-site]

Back in the days of manual synchroscope-syncing, an error doing it damaged one of Ironbridge's generating-sets beyond the point where it was economic to bring back into service.

[Trevor]

I used to be in charge of a no of generators that used bump-less power transfer As stated the units would self synchronise before operating the contactors both on with the mains and on going back to mains all worked well.
Trev