This paper discusses power-system instability and the
importance of fast fault-clearing performance to aid in reliable
production of power. An explanation regarding small-signal stability,
high-impedance transmission lines, line loading, and high-gain
fast-acting excitation systems is provided. Transient stability is
discussed, including synchronizing and damping torques. The
power-angle curve is used to illustrate how fault-clearing time and
high initial response excitation systems can affect transient stability.
The term “power-system stability” has become increasingly
popular in generation and transmission. The sudden requirement
for power-system stabilizers (PSSs) has created confusion about
their applicability, purpose, and benefit to the system.