At 09:13 AM 10/11/1998 +0000, James, Chris wrote: >Some S American countries quote +/-10%, whether they actually do vary >that much I don't know.
No, they don't vary that much. I grew up in Brazil and I certainly would have noticed if my TV acted up and kept dropping out of sync. Also my record player (it had strobe bars). I'm not sure why various countries quote frequency tolerances, but in fact the actual variation is very minimal. Otherwise, nobody would be able to watch their TVs. >As for clocks - most nowadays are xtal controlled. The older mains >dervied clocks certainly in the UK relied on the fact that the >generating companies time averaged the frequency variation to zero over >a 24 hour period........... as I recall Well, there are still an awful lot of ac driven clocks around. But yes, as you and Chris Dupres point out, the total number of cycles is averaged out over 24 hrs. All the power companies that I am aware of do this. This is true in the US, Canada, UK, Brazil; indubitably most of the civilized world. >All generators on a grid "slave" each other so they remain in sync - >it's not a matter of getting two independent grids exactly in phase and >then connecting them. Hmm ... interesting ... How do they do this? Are all the generating stations connected by radio or microwave links? I don't see how they can do this unless the frequency is very stable. If one generator is off by a fraction of a precent, they would all have to be. This could be a nightmare, trying to get everybody synchronized to a variable frequency. The last time I took a power course was over 30 years ago. At that time, the prof (ex Bonneville Power Admin. staff) stated that all interconnected power grids maintained very exact frequency and phase. If this is not correct, then I want a refund on my course! Egon :-) --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
