Impact of power system instability on generator protection

Recent system instability events have interacted with both transmission and generation protection in ways not always envisioned by the protection engineer. This paper discusses what relay engineers need to know about power system stability, including the four basic types of power system instability: Voltage instability, Steady-state instability, Transient instability and Dynamic instability. The paper relates how these various forms of instability relate to generator and transmission system protection. The paper also discuss system schemes used to address instability including: Generator Fast Valving, Generator Tripping, Generator High-speed Excitation Systems, Independent Pole Circuit Breaker applications and various types of Special Protection Schemes (SPS)¹.