Leslie Newell wrote: > Generally they adjust the frequency throughout the day. As the load on > the system increases the frequency drops. To increase the frequency they > bring more generators on line. If the frequency gets too high they > reduce the generating capacity. The really tricky bit is matching > generating capacity to the load well enough to maintain a reasonably > accurate 50/60Hz > The power stations are self-synched to the overall grid. Opening the throttle on the turbines acts to increase frequency, but due to the enormous stiffness of all the alternators, many of the throttles have to be opened wider and then the frequency starts to rise very slowly. So, it is a VERY tricky and slightly unstable network. You can measure the effect of each individual alternator by measuring the phase angle between current and voltage, although that gets complicated by the excitation level of the alternator. Reducing field excitation causes the alternator to produce current that lags the voltage, like an induction motor, and increasing the excitation causes current to lead the voltage.
Experts have tried to model the whole grid, and found it to be very nearly mathematically intractable. Resistance and leakage inductance in transformers, etc. are the only thing keeping the grid (barely) stable. Jon ------------------------------------------------------------------------------ Increase Visibility of Your 3D Game App & Earn a Chance To Win $500! Tap into the largest installed PC base & get more eyes on your game by optimizing for Intel(R) Graphics Technology. Get started today with the Intel(R) Software Partner Program. Five $500 cash prizes are up for grabs. http://p.sf.net/sfu/intelisp-dev2dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
