Inductive Superconducting Fault Current Limiter Research Articles

Improvement of an inductive superconducting fault current limiter by using stacks of thin film washers as secondary

We have studied the performance of an inductive superconducting fault current limiter with a secondary based either on stacks of bulk Bi 1.8Pb 0.26Sr 2Ca 2Cu 3O 10+ α rings or thin film Y 1Ba 2Cu 3O 7− δ washers. Our results show that when the number of stacked samples is increased for operating at higher fault currents the device impedance is strongly reduced for bulk samples whereas remain nearly unchanged for thin film samples.

The impedance of inductive superconducting fault current limiters operating with stacks ofthin film Y123/Au washers or bulk Bi2223 rings as secondaries

Inductive fault current limiters operating with stacks of various smallsuperconducting elements acting as secondaries were studied. The stacks consist ofY1Ba2Cu3O7−δ thin filmwashers or Bi1.8Pb0.26Sr2Ca2Cu3O10+x bulk rings. A central result of our work is an experimental demonstration that the limitingcapability of the device is strongly reduced when several bulk rings are stacked, whereas itremains almost unchanged for thin film washers. The use of thin films should thereforeallow us to build more efficient high power inductive limiters based on stacks of smallwashers.

Inductive Superconducting Fault Current Limiters With Y123 Thin-Film Washers Versus Bi2223 Bulk Rings as Secondaries

We present the comparison between the performance of an inductive superconducting fault current limiter operating with bulk Bi1.8 Pb0.26Sr2Ca2Cu3O 10+x rings or Y1Ba2Cu3O7-delta thin-film washers as secondaries. We have measured the impedance offered by the limiter under current faults and the recovery time once the faults are cleared. Our results show that the use of thin films can improve the impedance response of these devices and especially their recovery time, which can be about two orders of magnitude shorter than that of bulk samples

Development of a HTS Magnet System for Long-Run Operation Test in Sub-Cooled Nitrogen

This paper deals with the development of a 6.6 kV/200A HTS magnet for inductive superconducting fault current limiter (SFCL) that uses a sub-cooled nitrogen cooling system which is expected to be very useful to the applied HTS machines. The several characteristics of the HTS magnet such as critical current, electrical insulation and heat transfer can be enhanced in the sub-cooled nitrogen cooling system rather than in saturated liquid nitrogen <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$( LN_2)$</tex> cooling system. To obtain sub-cooled nitrogen, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$ LN_2$</tex> was cooled down to 64 K with GM-cryocooler and its pressure was kept at 101 kPa with gaseous helium. In this investigation, the HTS magnet for a 6.6 kV/200 A SFCL was developed and its long-run operation characteristics were measured and analyzed. The characteristics of the sub-cooled nitrogen system like temperature, level of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$ LN_2$</tex> and pressure of cryogenic system were not degraded in spite of the several over current tests, electrical insulation tests, and even long-run operation tests with rated transport current.

Tests results and analysis of inductive superconducting fault current limiter with Bi-2223 tube and HTS tape as secondary winding

The Superconducting Fault Current Limiters are very attractive devices for the electrical power network. The performance comparison of inductive SFCL with three different secondary windings are presented in this paper. As secondary windings we used Bi-2223 tube, HTS tape and HTS tape parallel rings. We proved that the limiting capabilities of the SFCL with different windings are comparable, and the windings made of HTS tape are less expensive and more mechanically stable then HTS tubes. We proposed two method of implementation of shorted secondary winding. The experimental results show that HTS tube can be successfully substitute by cheaper shorted winding made of HTS tape.

Experimental and Numerical Analysis of Electrothermal and Mechanical Phenomena in HTS Tube of Inductive SFCL

The superconducting fault current limiter (SFCL) can be successfully used to limit the short-circuit current level in electrical networks to 5 (or less) times of rated current level. The inductive SFCL works like transformer with shorted secondary winding in a shape of HTS tube. The SFCL 625-A consists of superconducting Bi-2223 tube (critical current=625 A at 77 K), iron core and copper primary winding. The numerical model using the thermal physical domain of CAD package FLUX2D has been used to analyze of temperature distribution in HTS tube during the fault. The numerical model using the magnetodynamic physical domain of FLUX2D package was used to analyze the mechanical force in HTS tube during fault. We attempt to provide explanation why HTS tubes quite often break during current limitation

Thermal recovery of inductive superconducting fault current limiters with weak zones inthe secondary

We study here the limitation performance and the thermal recovery of inductivesuperconducting fault current limiters (SFCL) with special emphasis on the case in whichthe superconducting element (i.e. the secondary) has weak zones. Our experimental resultsindicate that the conduction of heat between a hot weak zone and its cold surroundingsplays an important role in its refrigeration. This suggests that it could be interesting todesign superconducting elements based on an appropriate distribution of artificialweak zones. In this way, the heat would be removed more efficiently than in thecase of homogeneous samples, where the heating would be uniform. By using anumerical simulation it is found that, with a proper distribution of artificially createdweak zones, it could be feasible to simultaneously get a good current limitation(as big as with homogeneous secondaries) and a shorter recovery time. Theseresults suggest an unexpected way to improve the performance of any SFCL.

Sub-cooled nitrogen cryogenic cooling system for superconducting fault current limiter by using GM-cryocooler

The 21st Century Frontier R&D Program was planned to develop and commercialize the inductive Superconducting Fault Current Limiter (SFCL) in Korea until 2011. The 1.2 kV/80 A inductive SFCL was planned to develop at the first year in the first phase (2001–2002) and the 6.6 kV/200 A inductive SFCL for short run operation test was planned to develop at the second and third year in the first phase (2002–2004). The experimental characteristics of conduction-cooled cooling system developed in the first year was very weak from the sudden large thermal disturbance. Therefore, the conduction-cooled cooling system was concluded not appropriate for the cryogenic technology of the application of superconducting fault current limiter. In the third year research, the improved sub-cooled nitrogen cooling system was adopted and investigated. In this paper, the characteristics of each cooling type was compared and the basic deign of ameliorated cooling system was introduced and the total heat load of the cooling system was calculated and compared with the heat load of the cooling system developed at 2nd year research.

Harmonics Control of Inductive Superconducting Fault Current Limiter System With DC Reactor

The solutions for the harmonic reduction of the superconducting fault current limiter system was discussed in this paper. The ideal high-T/sub c/ SFCL system with the DC reactor has negligible influence on the power system under normal operations. However the high-order harmonic currents are generated from the 6-pulse bridge configuration. Passive filter techniques employ tuned LC filters at 5th, 7th, 11th and 13th harmonic frequencies. The harmonic currents can be eliminated using the tuned LC filter and the special bridge configuration. Simulation results are given to validate the harmonic isolation feature at harmonic frequencies and also demonstrate the harmonic filtering process to meet IEEE 519 harmonic standards.

Design and Cooling Characteristic Results of Cryogenic System for 6.6 kV/200 A Inductive Fault Current Limiter

The conduction-cooled cryogenic cooling system for 1.2 kV/80 A inductive superconducting fault current limiter (SFCL) was fabricated and tested for its cooling characteristics in 2002. The observed thermal stability of the conduction-cooled system was very unreliable and precarious for the applied superconducting equipment with very large variation of currents like SFCL. Therefore, we replaced the conduction-cooled system with the sub-cooled nitrogen system for the 6.6 kV/200 A SFCL. In this paper, the design techniques and test results of cooling characteristics were introduced. The conditions for achieving the sub-cooled nitrogen state were 1 atm and 64 K. First, the temperature of 64 K was achieved by using the rotary pump and then the pressure of 1 atm was achieved by GHe. The characteristics of liquid nitrogen were strongly enhanced in these conditions. This fabricated cryogenic system merely for the short run operation test SFCL. Finally, the cryogenic system for the long run operation test SFCL was introduced.

Design, Fabrication, and Test of High-Tc Superconducting DC Reactor for Inductive Superconducting Fault Current Limiter

A high-T/sub c/ superconducting (HTS) DC reactor has been developed as a part of DC reactor type superconducting fault current limiter (SFCL) rated on 6.6 kV/200 A. The DC reactor was a solenoid coil and was wound with a 4-parallel stacked tape. This coil has 5 layers which are connected in series each other. The inductance of the coil is about 84 mH. This paper deals with the design, fabrication and testing of the DC reactor. For this design of the coil, a prototype solenoid coil had been used. Using the experimental result of a prototype solenoid, the number of stacks and the inductance were designed. The winding machine for the HTS solenoid was manufactured. Using this machine, the large-scale HTS solenoid using a Bi-2223 tape was fabricated successfully. Characteristics of the fabricated coil were observed through a measurement of voltage as current transportation.

Losses of Thyristor on Modified Bridge Type High-Temperature Superconducting Fault Current Limiter

Due to the high voltage and current ratings of the modified bridge type high-T/sub c/ superconducting fault current limiter (SFCL), the exact determination of on-state and switching loss in the thyristor is an important problem under normal condition. This paper treats investigations on losses in the thyristors that are essential parts of the inductive current limiter. After the detailed switching characteristics of these thyristors are described, the power losses are calculated in the system. Analysis of the switching process in the inductive SFCL with the DC reactor is given and the on-state, switching, and snubber losses are also estimated under normal conditions. The proposed model is suitable for investigations with system loss analysis and overall system cost.

Bi-2223 and Bi-2212 Tubes for Small Fault Current Limiters

The superconducting fault current limiters (SFCL) can be used to limit the short-circuit current level in electrical transmission and distribution networks. In one concept of SFCL-serial resistive limiter, the superconductor is inserted in the circuit directly. During a fault, the fault current pushes the superconductor into a resistive state and resistance, which limits the fault current, appears in the circuit. Another concept-inductive limiter works like transformer with shorted superconducting secondary winding. The impedance of this limiter under standard operation conditions is nearly zero, since the zero impedance of the secondary superconducting winding is reflected to the primary. In the event of a fault, the resistance in the secondary winding is reflected into the circuit and limits the fault current. The small inductive type SFCL's with Bi-2223 tubes with critical current=112 A, 625 A, and 1210 A (at 77 K and self-magnetic field) and various numbers of primary winding turns are presented with their limitation coefficients. The resistive type SFCL based on Bi-2212 tube with critical current=125 A (at 77 K and self-magnetic field) is presented too.

Design, fabrication techniques and test results of 1.2 kV/80 A inductive fault current limiter by using conduction-cooled system

An inductive superconducting fault current limiter protects power system by limiting the amplitude of fault current by the inductance of its dc reactor. Therefore, it is very important to design the dc reactor of high critical current prior to fabrication. At first, the optimal design parameters were calculated by using finite element method and then the superconducting dc reactor for 1.2 kV/80 A rms inductive superconducting fault current limiter was designed by considering the conduction-cooling characteristics. Moreover, the design, fabrication and conduction-cooling method of the superconducting dc reactor were introduced. Actually, the superconducting dc reactor was fabricated and cooled down to 20 K by using GM cryocooler. Finally, the short-circuit test was performed and the experimental results were discussed.

Design, fabrication and testing of superconducting dc reactor for 1.2 kV/80 a inductive fault current limiter

A superconducting DC reactor protects a power system by limiting the amplitude of fault current with its inductance. Therefore, it is very important to design and simulate the DC reactor precisely for making the power system stable and effective. In this paper, we designed the superconducting DC reactor of an inductive superconducting fault current limiter conceptually and acquired the optimal design parameters by using Finite Element Method (FEM). We manufactured the superconducting DC reactor and tested its characteristics at cryocooler-cooled 20 K temperature. Moreover, we compared experimental characteristics with simulation results and analyzed them. We introduced the design method of the superconducting DC reactor and the fabrication method of a 1.2 kV/80 A class DC reactor for an inductive superconducting fault current limiter. Finally, we performed the short circuit test and discussed the results.

Properties comparison of superconducting fault current limiters with closed and open core

The high-T/sub c/ superconducting fault current limiter (SFCL) can be classified into resistive, inductive and hybrid types. The inductive type HTSFCL seems to show most prospect due to the simple design (construction) of the secondary superconducting winding in the form of ceramic type BSCCO and for the reduction of current leads. In an inductive type SFCL, ferromagnetic cores for magnetic flux are applied, however open cores are also taken into consideration in order to simplify the construction. The results of experimental and computational investigations of inductive SFCL parameters are presented in this paper.

Study on inductive high- Tc superconducting fault current limiters

An inductive superconducting fault current limiter based on Bi-2212 tubes has been built. In this paper, we present the experimental results of static impedance tests and dynamic short circuit tests. The dynamic short circuit tests show the limiter can limit the fault current to a few times the nominal current. We evaluate the performance of the limiter and compare the differences between the closed-iron core and the open-core. Using the equivalent circuit of inductive superconducting fault current limiter (SCFCL), we calculate the effective permeability, ( μ( H)), of the magnetic circuit during fault conditions. Results show that the resistance of superconducting tubes is the primary limiting factor of the SCFCL during the fault condition, and the open-core is more suitable for the distribution networks than the closed-core.

The short circuit analysis of integrated three phase superconducting fault current limiter with two phase superconducting circuits

The integrated three-phase superconducting fault current limiter (SFCL) using two superconducting circuits was conceptually designed and analyzed. The integrated three-phase SFCL system is an upgrade version of inductive single-phase SFCL systems. It uses one magnetic core having three legs, like a three phase transformer. Each leg has a copper winding as a primary winding but, as a secondary winding, only two legs have superconducting tubes and the other leg has no secondary winding. It has the same characteristics with inductive single-phase SFCL. Moreover it has other merits in stability, expense, and mechanical stress.

Quenching behaviour of superconductors in an inductive fault current limiter

Earlier papers introduced a new form of inductive superconducting fault current limiter (FCL) in which the primary and secondary windings were interleaved symmetrically, producing current sharing in the multiplicity of secondary coils. A new FCL which employs similar structure but in a higher rating has been designed and constructed. The new FCL, has eight series connected primary coils interleaving with at least eight isolated secondary superconductor rings around a toroidal iron core. Investigation of this FCL when carrying a different number of superconductor rings has showed the ability to reduce the leakage fields around the windings hence improving the current rating of the FCL by increasing the number of superconductor rings in the FCL. However, being isolated, each superconductor ring has a different switching profile as a result of the development of normal regime resistance at different current values. A new way of characterising this nonuniform quenching behaviour of the superconductors in the FCL as the fault occurs is reported.

Novel design and operational characteristics of inductive high-Tc superconducting fault current limiter

A novel prototype of an inductive superconducting fault current limiter with an iron core and an air gap was fabricated and tested. If its impedance is not high enough to limit the fault current, then destructive damage occurs in the power system. The authors attained magnetic saturation under the higher current by introducing an air gap in the three-legged magnetic core. The fault current was successfully limited to two times as much as the nominal current without high fault current within 1/4 cycles at a 60 Hz source having an effective voltage of 70 V.