Dynamic simulations help improve generator protection

This paper describes a digital simulation study of a set of two 160 MW generating units operating in the Juan de Dios Batiz Paredes thermal power station, in Topolobampo, Sinaloa, Mexico. This plant belongs to Comision Federal de Electricidad, the national Mexican utility. We first discuss the factors that limit the active and reactive power delivered by a generating unit, such as thermal and voltage limits, power-system imposed limits, and the minimum excitation limiter. We then describe generator protection functions related to the capability curve. Later, we propose a P-Q plane-based scheme that provides generator loss-of-field protection and capability-curve violation alarming. Finally, we present the simulation results of loss-of-field and loss-of-synchronism conditions of one of the two generating units for several cases, including different initial load conditions, different loss-of-field modes, and different numbers of units on line.