Fault Current Peak Research Articles

두 개의 자속경로를 갖는 직렬연결형 초전도한류기의 이중 피크전류제한 특성

We proposed a series connection-type superconducting fault current limiter(SFCL) using E-I core that can prevent the internal magnetic flux generation of cores during normal operation, and prevent the saturation of cores due to a sudden magnetic flux generation at the initial stage of fault occurrence while limiting the peak current. Through a short-circuit simulation experiment, we analyzed the operating status of the two superconducting elements and limiting characteristics according to the size of the fault current peak before and after the failure. Further, the double peak current limiting characteristics according to the winding directions as well as the current and the voltage of each coil were compared and analyzed.

다양한 선재 조합에 따른 이종 초전도 스위치의 특성 실험 및 분석

A Hybrid Fault Current Limiter(FCL) which has more advantages in fast response and thermal characteristics than a simple resistive FCL had been proposed by our group. The Hybrid FCL consists of a resistive FCL for the magnitude of the first peak of fault current, and a fast switch for detecting fault current and generating the repulsive force within a cycle in fault situation. In ideal case, the impedance of the fast switch wound with two other kinds of HTS tape is negligibly zero in normal operation. But, during the fault situation, each HTS tape has different quench characteristics because of asymmetric current distribution. And this phenomenon causes effective flux and this flux opens the switch through the repulsive force applied to a metal plate of the fast switch. The magnitude of the repulsive force affects the switching characteristics of the fast switch. It should be large enough to raise the metal plate up. Otherwise the arc re-out break which are caused by not enough repulsive force to raise the metal plate up can cause unintended operation of the fast switch. In this paper, the numerical calculation of the repulsive force applied to the metal plate of the fast switch in various combinations of HTS tapes was performed by using the short-circuit test and finite element method.

Design of a DC Resistive SFCL for Application to the 20 kV Distribution System

A DC-operating resistive-type superconducting fault current limiter for AC applications (in short a DC Resistive SFCL) is based on the synergistic use of the "resistive" and the "rectifier" fault current limiter concepts, and allows the superconductor to operate in nearly DC current conditions. This regime of operation drastically reduces the AC losses and therefore opens up completely new perspectives with regard to the materials, the architecture of the cable, the layout of the windings and the cryogenics. In this paper the design of a DC resistive SFCL for application to the 20 kV distribution system is presented. A bus tie position with nominal rate of 25 MVA is considered as case study. The resistance and the inductance of the superconducting winding are arrived at by means of the parametric analysis of voltage transients, harmonic distortion and peak fault current. The design of the windings of the real scale device is carried based on a optimized MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> cable. The detailed design of the bridge rectifier is carried out and the power losses due to diodes are evaluated.

Test results of fault current limiter using YBCO tapes with shunt protection

A Fault Current Limiter (FCL) based on high temperature superconducting elements with four tapes in parallel were designed and tested in 220 V line for a fault current peak between 1 kA to 4 kA. The elements employed second generation (2G) HTS tapes of YBCO coated conductor with stainless steel reinforcement. The tapes were electrically connected in parallel with effective length of 0.4 m per element (16 elements connected in series) constituting a single-phase unit. The FCL performance was evaluated through over-current tests and its recovery characteristics under load current were analyzed using optimized value of the shunt protection. The projected limiting ratio achieved a factor higher than 4 during fault of 5 cycles without degradation. Construction details and further test results will be shown in the paper.

Fault Current Limiter Using YBCO Coated Conductor—The Limiting Factor and Its Recovery Time

A fault current limiter (FCL) based on an arrangement of parallel connected high temperature superconducting tapes constituting a limiter element was designed and tested in 220 V line for a fault current peak between 1 kA to 2 kA. The limiter employed second generation (2G) HTS tapes of YBCO coated conductor reinforced with stainless steel. Four tapes were electrically connected in parallel with 0.4 m effective length per element wherein 16 elements connected in series constitutes a single-phase unit. The FCL performance was evaluated through over-current and current fault tests. Its recovery characteristics were used to design the shunt protection. The designed limiting ratio is 4 for 16 elements and the experimental result for one element showed a 20% limiting ratio. For the fault current test one element can withstand five cycles of fault without degradation. It was observed recovery times below 0.5 s under nominal load using a shunt resistance of 173 mOmega.

Fault Current Test of a Bifilar Bi-2212 Bulk Coil

A bifilar Bi-2212 bulk coil with parallel shunt resistor was tested under fault current condition using a 3 MVA single-phase transformer in a 220 V-60 Hz line achieving fault current peak of 8 kA. The fault current tests are performed from steady state peak current of 200 A by applying controlled short circuits up to 8 kA varying the time period from one to six cycles. The test results show the function of the shunt resistor providing homogeneous quench behavior of the HTS coil besides its intrinsic stabilizing role. The limiting current ratio achieves a factor 4.2 during 5 cycles without any degradation.

Development and Test of a Superconducting Fault Current Limiter-Magnetic Energy Storage (SFCL-MES) System

A superconducting fault current limiter-magnetic energy storage (SFCL-MES) system for substation applications is proposed. SFCL-MES system can limit not only the peak fault current, but also the steady fault current. Moreover, it can provide high-quality power for the critical customers of the substation at the same time. A 100 kJ/1000 A/20 kVA SFCL-MES prototype system is developed, and it mainly consists of a NbTi magnet with two coaxial and homocentric solenoids for reducing stray field, a three-half-bridge converter and a current regulator. The principle of SFCL-MES is analysed, the design and experiment results for the SFCL-MES system are described.

Reduction of fault current peak in an inductive high-Tc superconducting fault current limiter

This paper dealt with current-limiting performances of an inductive high-Tc superconducting fault current limiter with an auxiliary coil. The fault current limiter mainly consists of the primary copper coil, secondary high-Tc superconducting rings, and auxiliary high-Tc superconducting coils, which are magnetically coupled through three-legged core. The superconducting fault current limiter as a series element in the power system is inserted to limit the fault current. The device presents fast variable-impedance features in the event of a fault condition. The fault current peak can become relatively large for certain ranges of the flux and the fault instant due to the core saturation. The auxiliary coil proposed in this paper was proven to increase the impedance of the SFCL up to more than 31% while preventing the core saturation.

자속구속형 전류제한기의 초기 사고전류 제한시점 변화

A flux lock-type SFCL consists of two coils which are wound in parallel each other through an iron core, and a HTSC thin film connects in series with coil 2. The operation of the flux-lock type SFCL can be divided into the subtractive polarity winding and the additive polarity winding operations according to the winding directions between coil 1, coil 2. When a fault occurs, the fault current in the HTS thin film exceeds the critical current so that resistance is generated in the HTS film, and thereby the fault current is limited by an instant rise in the impedance of the flux-lock type SFCL. We investigated he variances of initial fault current limiting instant according to the ratio of inductance of coil 1 and coil 2 in the flux-lock type SFCL. It was confirmed from experiments that the initial fault current limiting instant in the subtractive polarity and additive polarity windings were faster as the ratio of coil 2' inductance for coil 1's inductance increased. The 1st peak of fault current in case of the subtractive polarity winding was higher as the ratio of coil 2's inductance for coil 1's inductance increased. On the other hand, in case of the additive polarity winding, the 1st peak of fault current was lower.

Performance of a 1 MV A high temperature superconductors-enabled saturable magneticcore-type fault current limiter

A 1 MV A single-phase DC saturated iron core-type fault current limiter (FCL) employingDC coils manufactured from Bi-2223/Ag high temperature superconductor has beendesigned, constructed, and tested. The device, configured to respond to a fault occurring oneither the positive or negative wave cycle, exhibited instantaneous reaction and reset times.It could clip a continuous applied steady state fault current of 1200 A, and limited atransient peak fault current of 2200 A to the specified current of 100 A. The operation of thedevice did not produce any significant harmonic contribution from the clipping action, asunder fault conditions, 99.96% of the harmonic power spectrum of the clipped waveformcontributed to the fundamental, and the non-fault inductance of the FCL was<0.01 mH.

Influences of superconducting fault current limiter (SFCL) on superconducting generator in one-machine double-line system

Analysis of superconducting generator in single machine double-line infinite-bus transmission system equipped with SFCL's has been performed by use of EMTDC/PSCAD. When some faults occur in one transmission line, the SFCL in the fault line operates and then the peak fault current can be limited to expected value by use of a function of the SFCL. However, in some cases, the SFCL in the other sound line has been also proved to occasionally operate due to the interaction through each transmission line. Problems due to an installation of the SFCL's in such a model system and the influences on the superconducting generator have been pointed out by simulation analysis.