Evaluation of Excitation System Effect on Power Oscillations at Full Load of an 805 MVA Hydrogenerator

The 805 MVA hydrogenerator of Gun Power Plant had power oscillations under operating conditions at high loading after having substituted its runner to rehabilitation. In order to investigate the origin(s) of such power swings and its solutions the following actions were carried out. In term of hydraulic system, tests with air admission and with a cylindrical extension on the end of runner cone; regarding the generator-power system, frequency response were made for different settings of the automatic voltage regulator (AVR) and power system stabilizer (PSS) with and without the cylindrical extension of cone. This paper presents the effects of automatic voltage regulators and power system stabilizer settings in the solution of a resonant frequency problem involving the hydraulic, mechanical and electrical systems, related to an 805 MVA generator