On Thu, 6 Sep 2001, Lincoln Dale wrote:
HZ moving around causes far more problems -- makes peoples clocks go slow and fast. for that reason, HZ is very tightly regulated - if it goes over for a period, they'll make it go under to even it out.
Sorry for the nit-picking... Grid AC frequency is tightly controlled for entirely different reason - imagine what happens when you have two generators on the same grid, out of phase from each other. (In really large grids, like ex-USSR's United Energy System wave propagation delays make the whole synchronization dance quite interesting, particularly considering that turbines start rotating faster if load drops, etc). There other, as imprtant, reasons to keep frequency stable: for example, phase difference determines the direction of energy flow in an inter-tie transmission line! (see, for example, analysis of coupled oscillators in Feynman's lectures on physics). And there's a whole can of worms in keeping right the angle between voltage and current :) Actually, a lot of what grid control automatics people do could be a very well worth to learn for the network people. Grid control requires very fast redistribution of the load to keep parts of grid in sync; miss the time window, and you have to live in panic mode, effectively shutting down and patritioning grid to protect equipment against cascading effects. That forced automation designers to go into a lot of very heavy trickery, like pre-computing failure modes, and then quickly selecting the right scenario. Of course, no in-line signalling foolishness there :) --vadim