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Selection of the SFCL Type and its Design in order to Resolve the Problem Associated with the Rise of Grid Short-Circuit Level in a Sample Distribution and a Sample Sub-Transmission Substation of Tehran Regional Electric Company

Samizadeh, Ali | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58784 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Vakilian, Mahdi; Fardmanesh, Mahdi
  7. Abstract:
  8. In recent years, with the increase in generation capacity and the expansion of power networks, the grid short-circuit level has significantly risen, creating serious challenges for the protection of the network electrical equipment. One effective solution in this context is the use of Superconducting Fault Current Limiters (SFCLs), which, due to their fast transition from the superconducting state to the resistive state, can limit the high fault currents within a short period of time. In this thesis, after reviewing the operating principles, types, and applications of SFCLs, in the first step a semi-industrial prototype of a resistive-type SFCL is tested in the Superconductivity Laboratory of Sharif University of Technology. This device not only demonstrated the ability to limit fault currents under laboratory conditions, but also a controllable thyristor switch was designed and constructed to interrupt the fault current limited by the SFCL. Moreover, a cryostat (thermal insulation container) was designed and fabricated to maintain the cryogenic conditions of the superconductor. As the main achievements of the thesis, two practical SFCLs are deigned to be used in the power networks. The first design, is developed for a sample sub-transmission substation of Tehran Regional Electric Company. This design is based on a modular structure with bifilar pancake coils, where 136 coils are implemented in series-parallel modules. The dynamic thermal simulation of this system is carried out using Simulink software. In this simulation considering realistic conditions such as heat transfer between the microlayers of the superconducting tape and convective heat transfer between the liquid nitrogen and the superconducting tape surfaces, (using the Thermal-Electrical Analogy) through application of the Multi Conductors algorithm and the finite difference method (FEM) the study is carried out. The second design targets a sample distribution substation to protect the electrical equipment and the outgoing feeders againt the rise of grid short circuit level. It employs a hybrid structure that combines the parallel reactors of opposite coupling with SFCL to ensure a fast and stable fault response. The electro-thermal modeling of this system is performed by application of MATLAB/Simulink software, while the yoke and reactors are simulated by COMSOL Multiphysics software to monitor the magnetic flux density and to determine the reactor inductances. The results of simulations and experiments demonstrate the successful performance of the proposed SFCLs in reducing the short-circuit levels, enhancing power system reliability, and providing a better protection for the sensitive equipment
  9. Keywords:
  10. Superconductivity ; Fault Current Limiter ; Power Systems ; High Temperature Superconductor ; Short Circuit Level Increase ; Design

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