Electrical Generation Interface and Grid Interaction
Core concepts
Understand the generator, excitation, synchronization, and the grid interface. Candidates must know synchronizing conditions: voltage magnitude, frequency, phase angle, and phase sequence. Know real power follows torque and is controlled by the governor, while reactive power follows excitation and is controlled by the voltage regulator. Understand droop, load sharing, islanding, and the effect of grid frequency on turbine speed. Recognize the role of the generator circuit breaker, protection relays, and the difference between motoring and generating.
Traps
Questions often test which control changes real versus reactive power. Another trap is synchronization: closing the breaker out of phase causes large currents and mechanical shock. Remember that a grid frequency drop increases turbine load if droop control is active, and that loss of excitation reduces reactive support. Do not confuse the generator breaker with the turbine trip valve.
Worked rule of thumb
With 5% droop and a 1% grid frequency drop, the unit picks up roughly 1/5 = 20% of its rated load if it has headroom. Use this to predict load swings during frequency events and to explain why multiple units share the correction.
Exam focus
Be ready to explain synchronization conditions, real versus reactive power control, and the consequences of a breaker or excitation failure.