The definition of droop is the amount of speed (or frequency) change that isnecessary to cause the main prime mover control mechanism to move from fullyclosed to fully open. In general, the percent movement of the main prime movercontrol mechanism can be calculated as the speed change (in percent) divided by theper unit droop. A governor tuned with speed droop will open the control valve a specifiedamount for a given disturbance. This is accomplished by using feedback from themain prime mover control mechanism (valve, gate, servomotor, etc.). A simplifiedblock diagram of a droop governor is shown in Figure 2. If a 1% change in speedoccurs, the main control mechanism must move enough to cause the feedbackthrough the droop element to cancel this speed change. Thus, for a 1% speedchange, the percent movement of the main control mechanism will be the reciprocalof the droop (i.e. if the droop is 5% the movement will be 1/.05 = 20). If the governor is tuned to be "isochronous" (i.e. zero droop), it will keepopening the valve until the frequency is restored to the original value. This type oftuning is used on small, isolated power systems, but would result in excess governormovement on large, interconnected systems. Therefore, speed droop is used tocontrol the magnitude of governor response for a given frequency change so allgenerators will share response after a disturbance.
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an error does'nt become a mistake if corrected!
Turbine
Re: turbine
