Abstract
Excitation winding interturn short circuit (EWISC) is a common fault in turbo-generators. Once the fault occurs, if not handled in time, it will result in significant security risks to the power system. Using the multifield characteristics of fault generators for a comprehensive diagnosis can make the diagnostic results more accurate and credible. In this paper, taking a TA-1100-78 type, two pole pairs turbo-generator as the research object, the two-dimensional finite element electromagnetic model of stator/rotor and the three-dimensional finite element heat transfer model of rotor were established. The electromagnetic field, temperature field, and stress field of the generator were simulated and analyzed. At the same time, the air gap magnetic field, three-dimensional temperature field, and stress field distribution of the rotor were calculated for EWISC faults in different fault degrees and positions. The results showed that the EWISC fault weakened the air gap magnetic field and caused unbalanced electromagnetic distribution. At the same time, it caused a distortion of the rotor temperature field, resulting in an unbalanced distribution of the temperature field. The stress field was affected by the distortion of temperature field, and the local thermal stress increased but did not exceed the yield limit of the material. Restorable elastic deformation occurred when the rotor was heated, which caused the thermal bending of the rotor. The method adopted in this paper can provide a reference for the calculation of multiphysical field after a generator fault. It is also pointed out that the thermal unbalance influence should not be neglected in the study of generator vibration characteristics.
Highlights
With the rapid economic development, demand for electric energy is increasing day by day, and the installed capacity is increasing year by year
As the core of thermal power generation and nuclear power generation, the safe and stable operation of turbo-generators is very important to the power grid
The rotor of the generator is in high-speed rotating state for a long time, the excitation winding is embedded in the rotor groove and rotates with the rotor, and the interturn insulation is destroyed by centrifugal force, which causes excitation winding interturn short circuit (EWISC) faults
Summary
With the rapid economic development, demand for electric energy is increasing day by day, and the installed capacity is increasing year by year. Reference [8] analyzes the electrical characteristics of EWISC and points out that EWISC faults make the excitation current relatively increased and the reactive power relatively reduced This method has been applied to some static excitation generators. Reference [12] studies the variation characteristics of electromagnetic power before and after a EWISC fault This method establishes the functional relationship between electromagnetic power and excitation current and obtains the expected electromagnetic power at any time. The analysis and research on the EWISC fault in turbo-generators in the world is mainly limited to the circuit and electromagnetic characteristics, and the temperature and stress field distribution as obvious characteristics of the fault have been seldom studied. The relationship between these characteristics and the EWISC short circuit fault factors was obtained
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