2-Pole turbo-generator eccentricity diagnosis by split-phase current signature analysis

Abstract

2-Pole turbogenerators are usually very high power round-rotor synchronous machines used in generating plants. Turbogenerator monitoring is crucial, especially in nuclear plants. Very long turbogenerator rotors experience excessive run-out due to thermal, mechanical, and magnetic unbalances, resonances, etc. The rotor eccentricity causes vibrations and winding and frame loosening. Since the stators of turbogenerators are often parallel-connected for maximum power output rating, the rotor eccentricities also make rise unbalances in the split-phase currents. This paper resorts to the split-phase current monitoring for detection and estimation of rotor eccentricities. A method is proposed, based on a special theoretical analysis of 2-pole round-rotor machines, through symmetrical components. Time-stepping finite-elements are used for confirmatory simulations of a 500MVA machine.