Experimental measurements of the rotor oscillations in an synchronous generator during the three-phased sudden short-circuit test

Abstract

This work presents a method to determine rotor oscillations during a three-phased sudden short-circuit test of a synchronous generator. To our best current knowledge, no such similar method is yet published in the technical literature. During the periodic and non-periodic component separation of the three phase currents, it was found that the time difference between the currents' extreme values, for any of the three phase currents, does not have a 10 ms constant value, as in the stationary phase. Investigating why this happens we found that these variations are caused by the rotor oscillations. Certain parameters of a synchronous generator's rotor and of the rotor's oscillations are measured during the sudden three-phased short-circuit test. Based on these readings, with the method presented in this paper, we can compute the rotor's mechanical oscillation amplitudes and the transient process durations. Using the measured values, the equation describing the rotor's mechanical oscillations, independent of its power, can be re-written. Knowledge of the oscillation amplitudes and their durations is necessary for a correct loop control design and in establishing the generator's performance.

Simulation of three-phase short circuit electromagnetic transient process of synchronous generator

“…When magnetic coupling exists in adjacent windings, mutual inductance should be considered to calculate the time constant, otherwise it will affect the accuracy of the final result. Under the circumstance of ensuring the constant flux linkage, studying the free current generated during short circuit, it can be concluded that according to the rotor excitation time constant Td', it can be concluded that it attenuates according to the time constant of excitation winding which the DC and frequency doubling components of stator windings correspond to the fundamental frequency components of rotor current [6]. The time constant 9 is determined by the ratio of inductance of stator winding to resistance considering the mutual inductance of excitation winding [7,8].…”