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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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Martin Angove wrote:
In message , Tony Williams wrote: In article , John wrote: OK, I'll rephrase the question: why can all gens not be synced by a common time standard instead of by the neighbouring mains waveform? I think because there is the unavoidable problem of phase shift along the transmission cables. The wavelength of 50Hz is about 6000Km, at which the phase would have shifted a full 360 degrees. Sounds no problem, but that represents a 10 degree sync difference only every 167Km or 104 miles. That might cause a problem on the UK's grid. You mean that if generator "A" and generator "C" are each 100 miles away from generator "B", are all synchronised together in *absolute* time by an external reference and all supply the same line, the waveform supplied by "A" and "C" will be 10 degrees out of phase with that supplied by "B" as measured from "B". A=====B=====C Sounds nasty. So am I right in thinking that the way it is actually done is (effectively) to have one generator start first, and for each of the others to synchronise with the received waveform at their own locations? In other words the generators are, in absolute terms, out of phase with each other but due to wavelength / propagation delay / whatever are for all practical purposes synchronised. I can see how this would work for a "bus" topology, but not for anything involving either rings or a mesh as the length of two or more paths from generator to generator will be different and hence received waveforms from each one will be different. How is the grid/supergrid actually organised in this country? How do they do it in the US where distances are vastly greater? Learn something new every day on this ng :-) Hwyl! M. With a mesh, the UK is fairly narrow, so the phase shifts east-west would be small compared to north-south, I guess. In principle I imagine one could have no end of phase shift if, and only if, something... ha, I cant explain it. But I guess its apparent theres no limit to how much phase shift could be accomodated within a network, but it would depend very much on its layout and current flows. You'd have to be careful what you connected to what via what, but in principle one could presumably operate a grid with a ripple shaped phase shift, like a ripple in water, with the phase shift adding upto several whole cycles. Someone can now explain why this is total twaddle. NT |
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