A generating station for a power system consists of four 120-MVA 15-kV 0.85-PF-lagging synchronous generators with identical speed droop characteristics operating in parallel. The governors on the generators' prime movers are adjusted to produce a 3-Hz drop from no load to full load. Three of these generators are each supplying a steady 75 MW at a frequency of 60 Hz, while the fourth generator (called the swing generator) handles all incremental load changes on the system while maintaining the system's frequency at 60 Hz.
(a) At a given instant, the total system loads are 260 MW at a frequency of 60 Hz. What are the no-load frequencies of each of the system's generators?
(b) If the system load rises to 290 MW and the generator's governor set points do not change, what will the new system frequency be?
(c) To what frequency must the no-load frequency of the swing generator be adjusted in order to restore the system frequency to 60 Hz?
(d) If the system is operating at the conditions described in part (c), what would happen if the swing generator were tripped off the line (disconnected from the power line)?