THE CAPABILITY OF ALTERNATORS IN VOLTAGE COLLAPSE ANALYSIS

ABSTRACT The paper presents and discusses the static models of the synchronous machines used in voltage collapse analysis, taking into account the capability limits.The paper considers the thermal limits of rotor and stator currents (dependent on voltage and real power), the underexcitation limiters action that prevents from the stator-end heating caused by eddy currents (dependent on voltage and real power), the real power limits (dependent on the turbine characteristics) and the stator voltage limits. The importance of a realistic model for the generators in the determination of the collapse condition is pointed out and a comparison is made between the results obtained using the traditional fixed upper and lower limits and some models that take into account the dependence of the limits on the voltage.