when the rotor angle becomes negative in PSSE, what does it mean?
I ran a simulation of IEEE 118-bus system in PSSE, and the bus fault was set to take place at t=0.2s and cleared at t=1.0s.
Something strange happened. The rotor angle started to become negative, what does it mean?
Cuz from what I know, the rotor angle is supposed to be between 0~90°.( maybe larger than 90° for some kinds of synchronous machines)
For the unstable condition, is the rotor angle not supposed to be beyond 90°and keep rising?