Abstract
Resistive-type of superconducting fault current limiters (RSFCL) have been developed for medium voltage class aiming to operate at 1 MVA power capacity and short time recovery (< 2 s). A RSFCL in form of superconducting modular device was designed and constructed using 50 m-length of YBCO coated conductor tapes for operation under 1 kV / 1 kA and acting time of 0.1 s. In order to increase the acting time the RSFCL was combined with an air-core reactor in parallel to increase the fault limiting time up to 1 s. The tests determined the electrical and thermal characteristics of the combined resistive/inductive protection unit. The combined fault current limiter reached a limiting current of 583 A, corresponding to a limiting factor of 3.3 times within an acting time of up to 1 s.
Highlights
Superconducting fault current limiters (SFCLs) are current limiting devices which present advantages of very low losses in steady state operation, high limiting impedance under fault conditions, reliable operation, very short reaction times to fault currents and an automatic response feature without the requirement of an external trigger mechanism
The modular superconducting device unit (MSD) constituted by 24 sectors in series was designed for operation at 761 V and steady current of 150 A
During fault current test the limited current values reaches 590 A in the first peak and 304 A in the fifth peak, with very low voltage developed within the Resistive-type of superconducting fault current limiters (RSFCL), Vlim = 230V when compared with the design value of 761 V
Summary
Superconducting fault current limiters (SFCLs) are current limiting devices which present advantages of very low losses in steady state operation, high limiting impedance under fault conditions, reliable operation, very short reaction times to fault currents and an automatic response feature without the requirement of an external trigger mechanism. A modular SFCL was built using 2 x 25 m length of YBCO CC tapes in parallel, with a shunt protection with equivalent resistance Rsh = 0.078 ȍ per sector, or Req = 1.86 ȍ for the whole modular device with 24 sectors, without electrical joints (Fig. 1) This configuration provides a homogeneous quench behavior of the HTS tapes, with a copper contact in each 20 cm-length of YBCO CC tapes, working as a thermal sink (barrier) contributing for limit ing the maximum temperature within the tape (reducing the length to recovery) and acting as stabilizer in the device for decreasing the recovery time. The power dissipation can achieve 73.3 kW (SFCL voltage 256 V and limited current 573 A) during 100 ms; the energy density of about 488 J/cm is lower than the critical value of 1,200 J/cm for YBCO tapes [6]
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