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Design and Fabrication of Inductive High Temperature Superconducting Fault Current Limiter

Hekmati, Arsalan | 2012

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 42803 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Vakilian, Mehdi; Fardmanesh, Mehdi
  7. Abstract:
  8. The continuous rise in electricity demand and the ever growing power generation in different power networks over the world have caused the short circuit level in the power systems to exceed the operational rating of the installed power devices (including cables, circuit breakers and buses). Replacing these devices with new higher rating devices is an expensive solution. From this point of view, utilizing fault current limiters is an economical solution. Superconducting fault current limiters form an efficient category of current limiters. This type is expected to be studied and used widely in future due to their advantages. In this thesis, the first chapter reviews the superconductivity phenomenon and its features briefly. The second chapter introduces various types of fault current limiters, their applications, and the related advantages. Two prototype inductive (shield-type) superconducting fault current limiters have been designed and fabricated in the superconductivity laboratory. YBCO rings have been utilized in the structure of the first prototype. A novel method has been used for the fabrication of these rings which has been explained in chapter three. The superconductor ring is cast directly which eliminates the drilling process of the superconductor pellets and makes easier the formation of the superconductor rings. In the chapter four, two fabricated prototypes are discussed and their test results presented. BSCCO tapes have been utilized in the structure of the second prototype. The fabricated prototypes are placed in a single phase test circuit and different types of fault have been applied to the circuit. The fault current signals are recorded and the voltage-current characteristics of the prototypes are obtained applying different voltages to their terminals and measuring the through currents. In chapter five, for the first time a novel method has been presented, based on the basic models of magnetic penetration into the superconductors, for the modeling of the shield-type SFCLS to simulate its different operational regimes. Utilizing this model, the through current of the SFCL in different fault conditions is simulated and compared with the measured currents presented in chapter four. In chapter six, an optimization process has been introduced (based on heuristic methods) for determination of the superconductor material optimum dimensions in the SFCL fabrication. The obtained minimum values have been compared with the superconductor material used in world-wide SFCL projects around the world. The considerable advantage of this optimization is demonstrated. In chapter seven, the mechanical forces on the superconductor ring have been calculated in different operating regimes of the SFCL operation. Utilizing these calculations a method has been introduced for the reduction of mechanical forces. This method lowers the probability of the damage to the superconductor ring during the fault. Another SFCL prototype has been fabricated using the results of this method. The results of tests performed on this SFCL has shown acceptable mechanical withstand of the fabricated superconductor ring
  9. Keywords:
  10. High Temperature Superconductor ; Superconductivity ; High Temperature ; Magnetic Shielding ; Fabrication ; Fault Current Limiter

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