Title page for etd-0720100-161358


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URN etd-0720100-161358
Author Chi-Hshiung Lin
Author's Email Address lin_chi_hshiung@hotmail.com
Statistics This thesis had been viewed 5352 times. Download 4211 times.
Department Electrical Engineering
Year 1999
Semester 2
Degree Ph.D.
Type of Document
Language zh-TW.Big5 Chinese
Title Improving the Torque Vibrations on Shafts and Blades of a Large-scale Steam Turbine Generator Set
Date of Defense 2000-07-11
Page Count 159
Keyword
  • flexible coupling
  • choke coil
  • mechanical filter
  • high temperature superconductive fault current li
  • corrosion fatigue
  • steam turbine generator
  • fatigue life expenditure
  • torque vibration
  • Abstract Abstract
    Recently, the expansion in power system capacities leads to the development of large-scale steam turbine generator units. As a result, a fault on the power system may induce large fault current and give rise to serious torque vibrations on turbine shafts and blades, which ought to be improved in order for the reliable operation of a turbine-generator system. In the thesis, countermeasures are proposed from electrical viewing-point and from mechanical viewing-point respectively.
    Based on electrical viewing-point, the apparatus in the generator stator side and in the rotor side respectively is applied to suppress the induced disturbing source. The high temperature superconductive fault current limiter bank introduces a large normal-state resistance to restrict the dc component of stator fault current. The choke coil acts as a low pass filter to restrict the system-frequency component of field fault current. Both of them lead to the reduction in electromagnetic torque of system-frequency and effectively improve the vibrating behavior of blades.
    Based on mechanical viewing-point, it is found from the electromechanical analysis that the Generator/LP-Turbine shaft stiffness and the Generator rotor inertia constant determine the responses of all turbine blades. Once the stiffness on this shaft section is reduced by replacing the rigid shaft coupling with a flexible one or the inertia constant is augmented by a system-frequency mechanical filter, the blades become intrinsically less responsive to electrical disturbances. As a result, the blades will bear less stress impact and can be designed with smaller safety factor.
    On the other hand, LP-turbine long blades operated in corrosive environment and underwent the statistical stress impact due to randomly distributed negative sequence current is studied also. In such situation, the blades may be subjected to corrosion fatigue and the long term effects of power system unbalance may become the cause of fatigue damage on blades though the negative sequence current is still within the limitation of generator thermo-rating. As a result, turbine blades are possibly unprotected by traditional system unbalance protection scheme. Therefore, it will depend on the operating environments and the blade materials whether such long-term stress can be neglected or not. If there is the potential of blade damage, one has to reconsider the I2 protection settings and rearrange the load distribution to limit the system unbalance.
    Advisory Committee
  • M. Y. Cho - co-chair
  • W. M. Lin - co-chair
  • C. Chyn - co-chair
  • K. C. Huang - co-chair
  • C. L. Huang - co-chair
  • T. P. Tsao - advisor
  • Files
  • thesis.pdf
  • indicate access worldwide
    Date of Submission 2000-07-20

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