This model represents a simple islanded power system operating in open loop. Generator A has 30 MW nominal power, generator B has 10 MW.
The model starts at steady state, with both generators at full load supplying a 40 MW load connected at the A side of the transmission line.
At time = 2s, the load is increased by 1%. As both generators have Ta = 10s, the frequency starts dropping by 1% every 10 s, or 0.05 Hz/s. Electro-mechanical oscillations are also triggered, that are not damped out because the generator models do not include the effect of rotor damper cages, and there is no primary frequency control in the system.