Rotor Oscillations of a synchronous generator due to under excitation
Rotor Oscillations of a synchronous generator due to under excitation
(OP)
What exactly causes rotor oscillations of a synchronous generator (while delivering complex power) during stages of under excitation.
Many thanks
Constantins
Many thanks
Constantins






RE: Rotor Oscillations of a synchronous generator due to under excitation
RE: Rotor Oscillations of a synchronous generator due to under excitation
As you may be aware a system will be less stable as the real power transported approaches the capacity of the line. Power transmitted by a long line (inductance) is approx sin(delta)*|E1||E2|/XL where E1 and E2 are voltages on each end of the line and delta is the angle between them. Syncronism is lost if delta exceeds 90 degrees since power handling capability starts decreasing at that point. In the underexcited case E1 will be lower and E2 will also likely be lower (depends on system reactive power balance), resulting in a lower power handling capability for the line.
So for a given amount of real power required to be transmitted, it is more stable to operate with higher voltage.
Note that real situations are of course much more complex... several transmission lines and internal reactance of generator. But in general the conclusion still holds... higher voltage causes increased ability to transmit real power.