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Title: Superconducting fault current limiter with integrated vacuum interrupter
Author: Pei, Xiaoze
ISNI:       0000 0004 2721 026X
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2012
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Fault current levels in land-based power systems are generally rising because of the increase in renewable generation capacity. Once the fault current level exceeds the capacity of the existing protection equipment, expensive upgrades become necessary. In order to avoid excessively expensive equipment upgrades, many fault current limitation techniques have been investigated. This thesis presents the work conducted on the design, manufacture and testing of a resistive superconducting fault current limiter (SFCL) with an integrated fast-acting vacuum interrupter. The practical application of magnesium diboride (MgB2) in round wire form was also investigated. A single-strand MgB2 SFCL coil was investigated and demonstrated repeatable and reliable current-limiting action. In practical power system applications, the development of SFCLs needs a considerable scale-up of the current-carrying capability of the MgB2 wire samples. One option is to use parallel wires in order to carry current levels in the kA range. The behaviour of a prototype three-strand MgB2 SFCL coil was assessed, which showed that each of the three wire strands shared the current approximately equally and demonstrated reliable and repeatable behaviour during testing. The MgB2 SFCL coil with multiple wire strands in parallel shows considerable potential as a practical method for scaling-up the current levels required for power system applications. One of the significant operational issues for resistive SFCLs is the temperature recovery time after a fault is cleared. A vacuum interrupter was integrated therefore into the SFCL system to quickly remove the superconducting coil from the circuit during a fault condition and allow the superconducting coil to recover whilst a bypass resistor acted as a current limiting resistor. A fast-acting actuator and its control circuit were designed and manufactured to control the operation of the vacuum interrupter. The SFCL with a prototype vacuum interrupter was successfully tested to validate the design process. The energy dissipated in the superconducting coil was significantly reduced by the fast operation of the vacuum interrupter and the recovery time significantly reduced. This research demonstrates the potential of a cost-effective and compact SFCL for the power system applications.
Supervisor: Smith, Sandy. Sponsor: EPSRC ; Rolls-Royce
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: SFCL ; MgB2 ; Vacuum interrupter ; Vacuum interrupter actuator ; Cryogenic