Flux-lock Type Superconducting Fault Current Limiter Research Articles

DC Fault Current Limiting Characteristics of Flux-Lock Type SFCL With Parallel Connection of Two Coils Using Twice Quench

In this paper, DC fault current limiting characteristics of DC flux-lock type superconducting fault current limiter (SFCL) with parallel connection between two coils were analyzed. DC flux-lock type SFCL with parallel connection between two coils was composed of two windings connected in parallel and two superconducting modules (SMs), which were connected in series with each secondary winding. DC flux-lock type SFCLs with a parallel connection between two coils and one SM with one secondary winding in series was thought to perform fault current limiting operation as in AC system. However, since the transient period after resistance generation in SM approaches into the constant value, unlike the AC system, there is a DC current limiting transient period. Therefore, the DC current limiting effect disappears in the DC system and the recovery characteristic after the fault is removed also disappears. To analyze the DC fault current limiting and recovery characteristics, a DC short-circuit test was per-formed, and the various behaviors of flux-lock type SFCLs in DC systems were investigated from the test results.

Analysis on Operational Characteristics of Double Quench Flux Lock Type Superconducting Fault Current Limiter

The superconducting fault current limiter (SFCL) which has many advantages is being chosen as an attractive method for limiting fault current. To upgrade the performance of the SFCL, various configurations are reported. Among them, the double-quench type SFCL has been studied in order to reduce the power burden of the high-temperature superconducting (HTSC) elements. The double-quench type SFCL which consists of the two HTSC elements and the normal resistance is a method to improve the performance of the HTSC elements. The design of the normal resistance in the double-quench type SFCL for the control of distributed fault currents on both HTSC elements to reduce the power burden is very important. However, the double-quench type SFCL is difficult to change the specification of the component depending on changing the power system. To improve the disadvantage on the double-quench type SFCL, this paper proposed the double-quench-flux-lock type SFCL which combine the double-quench type SFCL and the flux-lock type SFCL. The conventional flux-lock type SFCL which consists of an iron core, two coils, and the HTSC element could control the operation current and the impedance of the SFCL depending on the turn ratio between two coils. The operational characteristics of the flux-lock type SFCL could flexibly respond to changes in the power system. The double-quench-flux-lock type SFCL proposed in this paper was verified through PSCAD/EMTDC.

Power Burden of HTSC element and Over-Current Limiting Characteristics of Flux-Lock Type SFCL using Third Winding due to Winding Direction of Two Windings

As one of the superconducting fault current limiter (SFCL)s with the over-current limiting operation, the flux-lock type SFCL using third winding was reported. This SFCL was comprised of two windings and third winding wound on the same iron core. The winding direction of two windings among the design parameters in this SFCL was expected to be the more effective to affect the over-current limiting characteristics of the SFCL. In this paper, to analyze the effect of the winding direction of two windings on its over-current limiting characteristics, the short-circuit tests were carried out. Through the comparative analysis on the power burden as well as the resistance amplitude of the first high-TC superconducting (HTSC) element, the SFCL in case of the subtractive polarity winding was observed more advantageous than one in case of the subtractive polarity winding.

Improvement of Current Limiting and Recovery Characteristics of Flux-Lock Type SFCL with Series Connection of Two Coils Using Its Third Coil

In this work, the current limiting and recovery characteristics of a flux-lock type superconducting fault current limiter (SFCL) with series connection of two coils were effectively improved by adding a third winding into the conventional flux-lock type SFCL with series connection of two coils. To confirm the contribution of the third winding to the current limiting and recovery characteristics of this type of the SFCL, short-circuit testing was carried out with consideration of the third winding, and the effect of the third winding on the current limiting and recovery characteristics was examined by comparative analysis of the amplitude of the limited fault current and the power burden of the high-TC superconducting (HTSC) element comprising the SFCL. Through the analysis of both the limiting impedance and the operational current as the main design parameter of the SFCL, the improved current limiting and recovery characteristics of the flux-lock type SFCL using the third winding could be verified.

Double Quench Operation Characteristics of Series Connected SFCL Using Dual Iron Cores

In this paper, we proposed a flux-lock type superconducting fault current limiter (SFCL) with series connection of two coils in order to support the double quench function in relation to the intensity of fault currents at an early stage of a failure. Through the short-circuit simulation, we analyzed the transient fault current limiting characteristics of a flux-lock type SFCL with series connection of two coils and the instantaneous power load characteristics of the SFCL and superconducting elements. In case that the SFCL turns’ ratio between the primary and secondary windings is 0.5, the instantaneous power peak values in both the superconducting elements and the SFCL were confirmed to be much larger rather than 0.25 during the fault generation half period. Also, the peak fault current limiting operation of the SFCL and the sequential quench characteristics of superconducting elements 1 and 2, in case that the turns’ ratio of coils 1 and 2 is a 0.5, were shown to be more excellent than the case with 0.25.

두 트리거 전류를 갖는 자속구속형 초전도한류기의 고장전류 크기에 따른 초전도 모듈의 전력부담 분석

In this paper, the power burden of High-TC superconducting (HTSC) module comprising the flux-lock type superconducting fault current limiter (SFCL) with two triggering currents during the fault period was analyzed. The short-circuit tests for the simulated power system with the SFCL in the different fault positions, which were expected to affect the amplitude of the fault current, were carried out. Through the comparative analysis on the power burden of the HTSC modules, the proposed flux-lock type SFCL was confirmed to be effective to divide into two power burdens according to the amplitude of the fault currents.

Voltage Sag Suppressing Characteristics of Flux-Lock Type SFCL with Two Coils Connected in Parallel Using Dual Iron Cores

In this paper, the flux-lock type superconducting fault current limiter (SFCL), which is comprised of three windings, two high-TC superconducting (HTSC) elements and dual iron cores, was proposed and the short-circuit tests of the SFCL were performed. From the short-circuit tests, the voltage sag suppressing characteristics of the proposed SFCL as well as the fault current limiting characteristics due to the winding direction of two parallel connected windings were compared. The suggested flux-lock type SFCL, which two parallel connected windings comprising the SFCL were designed to be the additive polarity winding, was confirmed to be more effective than the SFCL designed to be subtractive polarity winding from the voltage sag suppressing operation. On the other hand, from its fault current limiting operation, the SFCL designed with the subtractive polarity winding for two parallel connected windings could be found that a little more superior than the SFCL designed with the additive polarity winding.

삼차권선을 이용한 이중퀜치 자속구속형 초전도한류기의 전류제한 특성 분석

The flux-lock type superconducting fault current limiter (SFCL) connects the two parallel windings in parallel with a ferromagnetic core. We suggest that the double quench flux-lock type SFCL should add a third winding. We analyzed characteristics of the fault current and the peak current using the quench of the high-Tc superconducting element. The proposed SFCL's inductances of a primary winding and the third winding were fixed and the amplitude of inductance of the secondary winding was changed. We found that the fault current can be more effectively controlled through the analysis of the equivalent circuit and the short-circuit tests.

FDM based multi-objective optimal sitting and design of TC-FLSFCL for study of distribution system reliability

An approach for optimal placement of flux-lock type SFCL with tap changer (TC-FLSFCL) and adjustment of tap changer related to it is used in this paper by debating the reduction of fault current and enhancement of reliability in a distribution network connected with distributed generation (DG). Recently, various superconducting fault current limiters (SFCL) have been developed in the field of power system. Especially, through researches, SFCLs have been put to practical use in distribution network as well as in the transmission network. TC-FLSFCL is a flexible SFCL that it has some preference than previous SFCLs. In this type of SFCL the current limiting characteristics are improved and the fault current limiting level during a fault period can be adjusted by controlling the current in the third winding, which also made the magnetic field applied to the high-Tc superconducting (HTSC) element. Three objective functions based on reliability index, reduction of fault current and the number of installed TC-FLSFCL are systematized and a nonlinear time-varying evolution (NTVE) based multi-objective particle swarm optimization (MOPSO) style is then formed in searching for the best location and tuning of tap changer of TC-FLSFCL to meet the fitness requirements. A decision-making procedure based on fuzzy decision making (FDM) is used for finding the best compromise solution from the set of Pareto-solutions obtained through MOPSO-NTVE. In a distribution network, Bus 4 of Roy Billinton test system (RBTS), comparative analysis of the results obtained from application of the resistive SFCL (RSFCL) and TC-FLSFCL is presented. The results show that optimal placement of TC-FLSFCL than RSFCL can improve reliability index and fault current reduction index with less number.

모의배전계통에 두 트리거 전류레벨을 이용한 초전도한류기의 전류제한 특성 분석

When the accident occurred in power distribution system, it needs to control efficiently the fault current according to the fault angle and location. The flux-lock type superconducting fault current limiters (SFCL) can quickly limit when the short circuit accidents occurred and be made the resistance after the fault current. The flux-lock type SFCL has a single triggering element, detects and limits the fault current at the same time regardless of the size of the fault current. However, it has a disadvantage that broken the superconductor element. If the flux-lock type SFCL has separated structure of the triggering element and the limiting element, when large fault current occurs, it can reduce the burden of power and control fault current to adjust impedance. In this paper, this system is composed by triggering element and limiting element to analyze operation of limiting current. When the fault current occurs, we analyzed the limiting and operating current characteristics of the two triggering current level, and the compensation characteristics of bus-voltage sag according to the fault angle and location.

Current Limiting Characteristics of a Flux-lock Type SFCL Using Two Triggered HTSC Elements

Abstract In this paper, a flux-lock type superconducting fault current limiter (SFCL) using two triggered high-Tc superconducting (HTSC) elements was proposed and its fault current limiting characteristics according to short-circuit location were analyzed. The flux-lock type SFCL with two triggered HTSC elements consists of two parts. One is two magnetically coupled coils with serial connection. The other, which is connected in series with the second coil, is composed of two HTSC elements in parallel connected through the normal resistor. Since the amplitude of the fault current depends on the fault location in case the fault occurs in a power system, the suggested flux-lock type SFCL can perform the fault current limiting operation through the quench occurrences of one HTSC element or two HTSC elements according to the amplitudes of the fault current. In case a low fault current, the fault current can be limited by utilizing only one HTSC triggered element. On the other hand, a larger fault current can be limited by two HTSC triggered elements. The short-circuit tests for the proposed flux-lock type SFCL according to the fault location were carried out in a feeder line of a power distribution system and its effective limiting operations could be discussed through the analysis on the short- circuit.

Study on Peak Current Limiting Characteristics of a Flux-lock Type SFCL with Two Magnetically Coupled Circuits

Abstract In this paper, we investigated the peak current limiting characteristics of the flux-lock type superconducting fault current limiter (SFCL) with two magnetically coupled circuits. The flux-lock type SFCL with two magnetically coupled circuits has the similar fault current limiting characteristics to the flux-lock type SFCL using its third winding. The current limiting operation of the SFCL is performed by the generation of the magnetic flux between two coils when a fault happens and the fault current limiting characteristics of the SFCL are dependent on the winding direction of two coils. To confirm it, the peak current limiting characteristics of this SFCL were analyzed based on its electrical equivalent circuit and the fault limiting characteristics of this SFCL were investigated through the fault current limiting experiment. Through the analysis on the short-circuit results, it was shown that the limited fault current could be adjusted by the winding direction of two coils.

Hysteresis Characteristics of Flux-lock Type SFCL with Series Connection of Two Coils

Since the saturation of the iron core comprising the flux-lock type superconducting fault current limiter (SFCL) with series connection of two coils can prevent its effective fault current limiting operation immediately after a fault accident, the flux-lock type SFCL's design considering the hysteresis characteristics is essential. For the analysis on the hysteresis characteristics of the SFCL during the fault period, its equivalent circuit for the transformer with the nonlinear exciting branch was drawn. Through the analysis on the SFCL's hysteresis curves, which were obtained from the SFCL's fault current limiting experiments based on its equivalent circuit, the winding direction of two coils, one of the design conditions, to suppress the saturation of the iron core comprising the flux-lock type SFCL with series connection of two coils was discussed.

피크전류제한 설정에 따른 피크전류제한 기능을 갖는 자속구속형 초전도한류기의 고장전류제한 특성 분석

In this paper, the fault current limiting characteristics of a flux-lock type superconducting fault current limiter (SFCL) with peak current limiting function were analyzed through its short-circuit tests. The setting condition for the peak current limiting operation was derived from its electrical equivalent circuit, which was dependent on the inductance ratio between the third coil and the first coil. Through the analysis on the short-circuit tests for the flux-lock type SFCLs with the different inductance ratio between the third coil and the first coil, the setting value for the peak current limiting operation of the flux-lock type SFCL with peak current limiting function could be confirmed to be adjusted with the variation of the inductance ratio between the third coil and the first coil.

변압기 권선을 이용한 자속구속형 초전도 전류제한기의 전류제한 및 전압강하 보상 특성

The superconducting fault current limiter (SFCL) can quickly limit the fault current shortly after the short circuit occurs and recover the superconducting state after the fault removes and plays a role in compensating the voltage sag of the sound feeder adjacent to the fault feeder as well as the fault current limiting operation of the fault feeder. Especially, the flux-lock type SFCL with an isolated transformer, which consists of two parallel connected coils on an iron core and the isolated transformer connected in series with one of two coils, has different voltage sag compensating and current limiting characteristics due to the winding direction and the inductance ratio of two coils. The current limiting and the voltage sag compensating characteristics of a SFCL using a transformer winding were analyzed. Through the analysis on the short-circuit tests results considering the winding direction of two coils, the SFCL designed with the additive polarity winding has shown the higher limited fault current than the SFCL designed with the subtractive polarity winding. It could be confirmed that the higher fault current limitation of the SFCL could be contributed to the higher load voltage sag compensation.

Study on Superconducting Fault Current Limiters Based on Normal Transformers

We propose a new structure of superconducting fault current limiters (SFCLs) coupled with a conventional transformer. The proposed SFCL systems have structures that the primary winding and the secondary winding of a transformer are connected with normal power grids and the tertiary winding of a transformer is connected with superconductors. These structures have advantages of both a transformer type SFCL and a resistive type SFCL. Therefore our SFCL can easily control the current limiting ratio by variation of the turn number of a transformer and minimize quantity of superconductors. Also it can be invisible in normal power grids and not bulky structure unlike a transformer type SFCL or a flux-lock type SFCL. Experimental results are reported in terms of current limiting properties, fault voltages and quench characteristics of superconductors in this system.

Analysis on fault current limiting and recovery characteristics of a flux-lock type SFCL with an isolated transformer

The flux-lock type superconducting fault current limiter (SFCL) can quickly limit the fault current shortly after the short circuit occurs and recover the superconducting state after the fault removes. However, the superconducting element comprising the flux-lock type SFCL can be destructed when the high fault current passes through the SFCL. Therefore, the countermeasure to control the fault current and protect the superconducting element is required. In this paper, the flux-lock type SFCL with an isolated transformer, which consists of two parallel connected coils on an iron core and the isolated transformer connected in series with one of two coils, was proposed and the short-circuit experimental device to analyze the fault current limiting and the recovery characteristics of the flux-lock type SFCL with the isolated transformer were constructed. Through the short-circuit tests, the flux-lock type SFCL with the isolated transformer was confirmed to perform more effective fault current limiting and recovery operation compared to the flux-lock type SFCL without the isolated transformer from the viewpoint of the quench occurrence and the recovery time of the SFCL.

Study on Peak Current Limiting Characteristics of a Flux-Lock Type SFCL Using Its Third Winding

Generally, the peak amplitude of the fault current after the fault occurrence depends on the transient component of the fault current, which is determined by the fault condition such as the fault angle. In the suggested flux-lock type superconducting fault current limiter (SFCL), the fault current of the lower peak amplitude causes the only high-TC superconducting (HTSC) element connected in series with one of two coils comprising the flux-lock type SFCL to be quenched, which the fault current can be limited by the lower limiting impedance of the flux-lock type SFCL. On the other hand, the fault current with the higher peak amplitude makes another HTSC element connected with the third winding to be quenched after the HTSC element connected in series with one of the SFCL's two coils is quenched, which contributes to the higher limiting impedance of this SFCL. Therefore, the effective fault current limiting operation of the flux-lock type SFCL can be performed by generating the SFCL's limiting impedance in proportion to the peak amplitude of the fault current. To confirm the current limiting operation of the proposed flux-lock type SFCL, the short-circuit tests of the flux-lock type SFCL using its third winding according to the fault angle were carried out and its effective fault current limiting operations were discussed.

Analysis on current limiting characteristics of a flux-lock type SFCL with two triggering current levels

In this paper, the flux-lock type superconducting fault current limiter (SFCL) with two triggering current levels was suggested and its current limiting characteristics were analyzed. The structure of the suggested flux-lock type SFCL with two triggering current levels largely consists of two parts. One is the flux-lock type SFCL with two magnetically coupled coils with series or parallel connection and one high-TC superconducting (HTSC) element, which is connected in series or parallel with one of two coils. The other is constructed in the third coil with another HTSC element.This suggested flux-lock type SFCL can limit the fault current by generating its limiting impedance with two different amplitudes, which are dependent on the initial amplitude of the fault current in case of the fault occurrence. To confirm the usefulness of the proposed SFCL, the limiting tests of the SFCL according to the fault angle, which is one of the effective fault conditions to affect the amplitude of the initial fault current, were carried out and its effective limiting operations were discussed.

모의전력계통에 적용된 자속구속형 초전도 전류제한기의 전류제한 특성 분석

When the current of the superconducting element exceeds its critical current by the fault occurrence, the quench of the high- superconducting fault current limiter (HTSC) comprising the flux-lock type superconducting fault current limiter (SFCL) occurs. Simultaneously, the magnetic flux in the iron core induces the voltage in each coil, which contributes to limit the fault current. In this paper, the fault current limiting characteristics of the flux-lock type SFCL as well as the load voltage sag suppressing characteristics according to the flux-lock type SFCL's winding direction were investigated. To confirm the fault current limiting and the voltage sag suppressing characteristics of the this SFCL, the short-circuit tests for the simulated power system with the flux-lock type SFCL were carried out. The flux-lock type SFCL designed with the additive polarity winding was shown to perform more effective fault current limiting and load voltage sag suppressing operations through the fast quench occurrence right after the fault occurs and the fast recovery operation after the fault removes than the flux-lock type SFCL designed with the subtractive polarity winding.