Understanding power system stability

This paper discusses the causes of power system instability and the importance of fast fault clearing. The k-constant model is used to explain the relationships among the following: small signal stability, high impedance transmission lines, line loading and high gain, fast acting excitation systems. Various types of power system instability, utilizing both mathematical and practical approaches, are covered. 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. In the past number of years, "power system stability" has become an increasingly popular term used in generation and transmission. The sudden requirement for power system stabilizers for use with new and existing excitation equipment has created much confusion about their applicability, purpose, and benefit to the power system. This paper will discuss the fundamentals of the power system stabilizer and its effectiveness in the system. An explanation will be provided concerning the various types of power system stabilizers and the benefit of some types over others. Lastly, the paper will address regulatory commission guidelines identified by NERC that will impact generation connected to the transmission system.