Superconducting Fault Current Limiter Research Articles

Protection Coordination of Radial Distribution Networks Connected with Distributed Generation Considering Auto-reclosing Schemes by Resistive Superconducting Fault Current Limiters

AbstractRadial distribution networks are normally protected against fault currents by fuses and reclosers. This protection is coordinated in a way that reclosers clear temporary faults before the melting of fuses and fuses melt to clear permanent faults. Distribution networks, which are recently connected with distributed generations (DGs), incur a variety of issues that are certainly worthy of closer considerations. One of these issues is the operation of protection devices. Recloser-fuse coordination may be lost when DGs are integrated with distribution networks due to the effect of current flowing from DGs during fault period and the breaking of the radiality nature of these networks. The impact of DGs on recloser-fuse coordination depends on penetration level, location, and type of DG. Recloser-fuse coordination of radial distribution networks connected with DGs can be kept by connecting resistive superconducting fault current limiter (R-SFCL) in series with the DG to limit the fault current contribution of DG during the fault period. However, when considering the auto-reclosing scheme of the recloser, recloser-fuse coordination may be lost even if R-SFCL is connected. This paper shows the effectiveness of R-SFCL to restore recloser-fuse coordination without considering auto-reclosing scheme. It also proposes solution methods based on three different configurations of R-SFCL to maintain recloser-fuse coordination when auto-reclosing scheme is considered. Simulation results illustrate the effectiveness of the proposed configurations of R-SFCL to keep recloser-fuse coordination. All simulations are performed using MATLAB/Simulink package.

Analysis on Protective Coordination between Over-Current Relays with Voltage Component in a Power Distribution System with SFCL

To solve the increased fault current in a power distribution system due to its interconnected operation of the generators with larger capacities, the superconducting fault current limiters (SFCLs) have been noticed as the advantageous protective devices. However, the application of the SFCLs into this power distribution system causes either mal-operation or non-operation of the protective relays and affects their protection coordination. Therefore, the studies on the protection coordination of protective relays considering the application of SFCL are needed. In this paper, the over-current relay (OCR) with the voltage component to minimize the influence of the SFCL on the operation of the OCR was proposed and the protection coordination between the OCRs with the voltage component due to the SFCL's application into the power distribution system was analyzed. From the analysis through the PSCAD/EMTDC simulation, the effective selection for the voltage proportional coefficient of the voltage component of the OCRs was discussed to improve the protection coordination between the OCRs.

Recovery performance of partially-joined porous-stabilized REBCO tape for resistive type superconducting fault current limiters

In the case of using rare-earth barium copper oxide (REBCO) tape as a current-limiting element, there are three requirements: high normal state resistance, high thermal stability, and quick recovery to the superconducting state. In this study, a new type of REBCO tape with a metal porous medium as a stabilizer (a porous-stabilized REBCO tape) was proposed, which has high resistance compared to bulk material and prevents film boiling due to its strong capillary force. First, a numerical simulation was performed to evaluate the current-limiting performance of the porous-stabilized REBCO tape with a Ni–Cr porous medium. The results showed that the current-limiting performance was dramatically improved by placing indium partially on the REBCO tape to join the porous medium compared to placing indium wholly. Then, the porous-stabilized REBCO tapes with various arrays of indium were manufactured, and tested to confirm its recovery characteristics. The experimental results indicated that the partially-joined Ni–Cr porous-stabilized REBCO tape reduced the recovery time by 69% compared to that of the stabilizer-free REBCO tape.

Design and Performance Test of a 20-kV DC Superconducting Fault Current Limiter

A resistive-type dc superconducting fault current limiter (SFCL) is developed for the fault current limiting at the Suzhou Nami substation. The rated voltage and current are 20 kV and 400 A, respectively. The prospective peak value of the short-circuit current is about 3.5 kA, and the current could be limited to less than 2.1 kA by the SFCL. The SFCL uses about 1800-m stainless steel reinforced yttrium barium copper oxide (YBCO) conductor. According to the testing results, the developed SFCL has passed the dc withstand voltage test at 50 kV/min, the full-wave lightning impulse voltage at 95 kV, and the dc power switching test with a peak value of 2.26 kA and a fault duration of 16.5 ms.

Quench and Recovery Characteristics of SFCL Based on Double-Sided YBCO Thin Films

In previous studies, we have preliminarily verified the feasibility of resistive superconducting fault current limiters (SFCLs) by using double-sided thin films. However, there are still many details that need to further research on double-sided thin films. In this present study, we fabricated two SFCL components juxtaposed on two sides of 2-in diameter sapphire substrates, coated with a gold layer and patterned into meander lines by photolithography. The double-sided SFCL components in serial connection were subjected to the ac fault currents, and their quench and recovery characteristics were investigated at various source voltages. From the experiments results, it was revealed that the double-sided configuration induced simultaneous quench and recovery between the components, and the temperature distribution in double-sided SFCL components was nearly close during quench and recovery. These results can be interpreted with the thermal interaction between top and bottom SFCL components by the sapphire substrates. The thermal effect of electrodes significantly affected the temperature distribution during quench and recovery. In addition, in overcurrent experiments, we defined the concept of perpendicular quench propagation to explain the rapid limitation of fault current at the beginning of short circuit and to optimize the structure of double-sided SFCL module.

Application of Superconducting Fault Current Limiter in Power Grid - Survey

Introduction of Distributed Energy Sources (DES) is the highest change happening to the distribution network. This paper describes different types of current limiting methods which reduce the magnitude of the fault current. The interconnected distributed energy sources to the conventional grid improves the power generation capacity of the power system but also increases the magnitude of fault current which cannot tolerate by the short-circuit ratings of the circuit breaker, relays, isolator etc. This paper reviews on the innovative electric equipment i.e. Superconducting Fault Current Limiter (SFCL), which reduces fault current magnitude in first cycle of fault current. Keywords: Distributed Energy Sources, Fault current, Superconducting Fault Current Limiter (SFCL), Protection Equipment.

Application of Superconducting Fault Current Limiter in Power Grid - Survey

Introduction of Distributed Energy Sources (DES) is the highest change happening to the distribution network. This paper describes different types of current limiting methods which reduce the magnitude of the fault current. The interconnected distributed energy sources to the conventional grid improves the power generation capacity of the power system but also increases the magnitude of fault current which cannot tolerate by the short-circuit ratings of the circuit breaker, relays, isolator etc. This paper reviews on the innovative electric equipment i.e. Superconducting Fault Current Limiter (SFCL), which reduces fault current magnitude in first cycle of fault current. Keywords: Distributed Energy Sources, Fault current, Superconducting Fault Current Limiter (SFCL), Protection Equipment.

Practical Calculation Method for the Short-Circuit Current of Power Grids with High Temperature Superconducting Fault Current Limiters

With the expansion of the power grid scale and the enhancement of network structure interconnection, the short-circuit current of power grids is increasingly close to the upper capacity limit of circuit breakers. The fault current limiter is effective in suppressing the short-circuit current of power grids, and with the mature development of superconducting technology, high-temperature superconducting fault current limiters (HTS-FCLs) have been widely used in power grids. Due to the nonlinear impedance–current characteristic of HTS-FCLs, the traditional short-circuit current calculation method is inapplicable to power grids with HTS-FCLs. First, based on the establishment of the electromechanical transient model and the short-circuit calculation model, the short-circuit current calculation procedure for power grids with HTS-FCLs is proposed. Second, the calculation methods for three-phase and single-phase short-circuit currents at the substation bus in power grids with HTS-FCLs are analyzed. Finally, three-phase and single-phase short-circuit currents at the 500 kV Xijiang substation bus in the Guangdong power grid are calculated as the study case. Simulation results show that compared with the situation where there is no HTS-FCL installed, the short-circuit current on the 500 kV bus decreases from 65.34 to 58.31 kA in terms of the three-phase short-circuit fault, and decreases from 54.56 to 46.62 kA in terms of the single-phase short-circuit fault, thus verifying the effectiveness and practicability of HTS-FCLs in suppressing the short-circuit current, which is significant for the safe, stable and reliable operation of the power grid.

Comparison of resistive and inductive superconductor fault current limiters in AC and DC micro-grids

Superconducting Fault Current Limiters (SFCL) have been used in power systems for many years, however the best possible positioning of different SFCL still needs a lot of work. Resistive and Inductive are two types of SFCL used in power system. Function of both these current limiters is to control the fluctuations and abnormalities in the system by introducing a high impedance in it, through transforming itself from normal stage to superconducting stage. In this research, placement of resistive SFCL and inductive SFCL in AC and DC microgrids (MG) are analyses at two different positions; at the point of integration of conventional source and distributed generator (DG) and at the point where DG is added to the system. The AC and DC microgrids contains industrial and residential loads, while they use respective main wind power generation source and photo voltaic power source along with conventional power, supplied from main grid. The behavior of both types of SFCL in their grid models is analyzed through MatLab Simulations, in order to compare their effectiveness and determine best possible position to place them.

Short-circuit fault current-limiting characteristics of a resistive-type superconducting fault current limiter in DC grids

Resistive-type superconducting fault current limiters (R-SFCLs) can limit short-circuit fault current and help DC circuit breakers (DCCBs) to isolate short-circuit faults in medium voltage and high voltage DC (HVDC) systems. SFCLs are always used with circuit breakers to break short-circuit current in power systems. The interruption characteristics of the DCCBs influence the current-limiting characteristics of the SFCLs. However, there has been a lack of investigation into the current-limiting and interruption characteristics when R-SFCLs are combined with mechanical-type DCCBs (M-DCCBs) based on the self-excited oscillation interruption principle in medium voltage and HVDC systems. The objective of this paper is to obtain the short-circuit fault current-limiting characteristics of a designed R-SFCL combined with an M-DCCB in DC grids. This paper describes the design of a 10 kV DC R-SFCL which was tested in combination with an M-DCCB in a DC circuit in order to obtain the quenched resistance and the required current interruption characteristics. Besides, a modular multilevel converter-based multi-terminal direct current (MMC-MTDC) grid was used to investigate the current-limiting and interrupting characteristics of the R-SFCL and the M-DCCB in a realistic HVDC grid. The experimental results show that in the 10 kV DC circuit the R-SFCL combined with the M-DCCB limited a 10 kA DC to the peak value of 1416 A and then interrupted this limited current successfully. And unlike other methods of DC interruption, this did not create overvoltage after interruption. The highest voltage on the R-SFCL is the system voltage during interruption. This means that the R-SFCL can effectively delay the voltage drop in MMC-MTDC grids, and provide enough time for the M-DCCB to interrupt the limited current. Thus, a combination of R-SFCLs and M-DCCBs might be an effective and reliable method to interrupt short-circuit fault currents in medium voltage and HVDC grids.

Modeling the Heating in a High Temperature Superconducting Current Carrying Element in Fault Current Limiters

Mathematical model was developed for modeling the increase temperature in high temperature superconducting (HTS) current carrying element in superconducting fault current limiters (SFCL). The variation in the heating up of HTS element along its length is a result primarily of the variation in its resistance that has to do with the manufacturing process employed to make it.The model was developed and mathematical modeling of the process was carried out in the Comsol MultiPhysics software package. Element that was tested was a 12 mm wide stack of three stainless steel tapes and three HTS soldered to each other. In order to get more precise parameters for the models the cross-sectional thermal conductivity was measured for the stacks of HTS of two different types. The estimates obtained using the model were very close to experimental data. The impact was also studied of the spread of the electrical resistance of HTS on how fast the current carrying element made from it heated up.

Modeling A Superconducting Fault Current Limiter Inserted in a Nine-Bus Electrical Network

Modeling A Superconducting Fault Current Limiter Inserted in a Nine-Bus Electrical Network

Transient Stability Improvement using Resistive-type Superconducting Fault Current Limiters (R-SFCL)

The rapid growth in the demand for electrical energy due to the astronomic growth in population has led to increase in the system fault current levels. This increase in fault current if not properly checked, could lead to system collapse. Superconducting Fault Current Limiters (SFCLs) are used in power system networks to mitigate against high fault current levels. In this study, the transient stability enhancement capability of three commercially available Resistive-type Superconducting Fault Current Limiters (R-SFCLs) based on Yttrium-Barium-Copper-Oxide (YBCO) and Bismuth-Strontium-Calcium-Copper-Oxide (BSCCO) Coated Conductors of different lengths were simulated. The test case was the Nigeria 330kV transmission network. The Runge-Kutta method was used to solve the differential equations characterizing the swing equations of the generators. The proposed method shows the effectiveness of the SFCL in enhancing transient stability of a Multi-Machine System.

Implementation of SFCL in Three-Phase System for Fault

The main aim of this paper is to place “Superconducting Fault Current Limiter” (SFCL) in a threephase power scheme for fault evaluation. superconducting fault current limiter (SFCL) in a three-phase system for the purpose of fault analysis. The implementation of the SFCL mitigates a burden on the network along with the reliability improvement of an electrical system. In this paper a typical three phase system is designed using Simulink /Sim Power System and analysis of LG and LL fault is done with and without employing SFCL in the system.

Enhancement on the Fault Ride through Capability of Power Distribution Systems Linked by Distributed Generation due to the Impedance of Superconducting Fault Current Limiters

Recently, studies on connecting distributed generation (DG) to power distribution systems through DC links have been actively conducted. When a fault in feeder of this power distribution system occurs, a voltage dip can happen in the grid. In order to prevent voltage dips, there are several solutions such as the application of a superconducting fault current limiter (SFCL). If a SFCL with a larger impedance is applied, the voltage dip of the grid is effectively prevented. However, this action can bring about the malfunction or the delayed operation of the over-current relay (OCR) due to the decreased fault current, which causes another problem of protection coordination between the protective relays. On the other hand, if the impedance of the SFCL is too low, excessive reactive power is supplied by the fault ride-through (FRT) regulation and the active power is reduced. This causes an active power imbalance on the DC link and increases the DC link’s voltage. As previous solutions to prevent the rise of DC links’ voltage, the deloading method and the application of a chopper resistor have been suggested. In this paper, a technique called active power tracking control (APTC), was proposed to suppress the rise of DC links’ voltage. Case studies considering the impedance of SFCL in the constructed power distribution system were carried out, and the rise of DC links’ voltage could be effectively suppressed without any significant delay in the operation of the OCR. This study is expected to solve both the voltage dip of the grid and the rise of DC links’ voltage when distributed generation is connected to a grid.

The Influence of the Geometrical Properties of Bulk Superconductors on Limiting Fault Current in an Electrical Network

The behavior of the superconducting fault current limiters SFCL used in Electrical Network is largely determined by the geometry properties and the type of the bulk superconductors used. In this work we present a numerical analysis of the electromagnetic and the thermal behavior of the SFCL and the influence of geometrical properties of the bulk superconductors of rectangular shape used in an electrical network The results are obtained from a three-dimensional computation code, developed and implemented under MATLAB environment where the formulation in magnetic vector potentials A and electrical scalar potential V are adopted to solve the electromagnetic problem and the heat diffusion formulation is also adopted to solve the thermal problem. The coupling is ensured by an alternating algorithm and the numerical resolution of the problem is ensured by the method of the finite volumes in its three-dimensional version in order to avoid certain problems of numerical convergence linked to the strongly nonlinear character of the problem to be solved.

Effectiveness evaluation of passive resistive element placement on a fault ride‐through enhancement in a DFIG‐based wind energy conversion system

AbstractOver the last few decades, doubly fed induction generators (DFIG) have become one of the most successful and preferred types of wind energy generators (WEG). The DFIG has the advantages of a wide range of speed operations, a high efficiency, and partial rated converters. However, direct coupling of the stator with the grid makes the system more prone to grid disturbances. The consequences of grid disturbances, such as a rotor overcurrent, stator overcurrent, electromagnetic torque oscillations, and direct current (DC) link overvoltage, are the predominant considerations that affect the rotor circuit, stator circuit, mechanical components, and DC‐link capacitor of the DFIG, respectively. These uncertainties affect the operation of the generator and may lead to the generator to be shutdown. In this paper, a novel position for the placement of a passive resistive element (PRE) is illustrated. This position of the PRE placement is compared with all other possible locations for the PRE. The different locations for PRE placement are the stator side, rotor side, across the DC‐link capacitor, and between the rotor side converter (RSC) and grid side converter (GSC). This paper aims to determine a cost‐effective solution among all possible locations of the PRE placement. The novel position of the PRE, ie, between the RSC and GSC, is the best position among the other possible locations of the PRE, when the performance, cost, and loss are taken into consideration. The effectiveness of the PRE is further compared with the resistive‐type superconducting fault current limiter (R‐SFCL). The PRE performs better and has a lower cost than the R‐SFCL.

Designing a composite deep learning based differential protection scheme of power transformers

This paper proposes a novel differential protection scheme based on deep neural networks (DNN). The goal is to propose a fast, reliable, and independent protection scheme in distinguishing inrush current from internal fault in power transformers, as the most challenging issue in power transformers protection. Shallow-based techniques require spectral analysis and handcraft feature extraction to be proper methods in this major. However, they require a significant computational cost. In order to address this issue, in this paper, a novel DNN-based approach is proposed based on combining convolutional neural network (CNN) and light-gated recurrent unit (LGRU), namely CLGNN. The results show a more accurate and more reliable performance than three different shallow and three state-of-the-art DNN based techniques. Adaptability and robustness of the proposed scheme are evaluated considering CT saturation, superconducting fault current limiter (SFCL), and series compensation impacts. The obtained results prove the effectiveness and validity of the proposed DNN-based protection scheme in this paper.

Analysis of Recovery Time of HTS Tapes With Electrical Insulation Layers for Superconducting Fault Current Limiters Under Load Conditions

The implementation of superconducting fault current limiters (SFCL) in the electrical power system requires the coordination of its parameters with the installed power system protection (PSP), in particular when using automatic reclosing (AR). The crucial parameter for AR is the recovery time of the SFCL, understood as the SFCL return time to the superconducting state after its operation. This time will depend mainly on the efficiency of the cooling system and the heat dissipation processes in the electrical insulation system. This article presents the results of experimental research on the return time to the superconducting state of superconducting tapes with layers of electrical insulation of various thicknesses. The tests were carried out in conditions in which the density of energy generated during the surge current flow correspond to the operating conditions of superconducting material in SFCL. Also, the transfer of this energy to liquid nitrogen corresponds to phenomena occurring in SFCL. The recovery time of several types of high temperature superconducting tapes in the zero current state and recovery under load were determined. The range of the load current at which it is possible return to the superconducting state was determined for tapes with and without electrical insulation. It has been shown that the analysis of these processes must take into account the strong dependence between the thermal energy transfer from the sample surface to liquid nitrogen and the type of nitrogen evaporation process on the surface of the sample. The presented research results are of particular importance for the functionality of SFCL and its cooperation with the PSP.

Influence of Bubbles on Insulation Properties of LN2 for SFCL Under Lightning Impulse and DC Voltage

As one of the most effective ways for the suppression and interruption of short-circuit current in voltage source converter based high-voltage direct current (VSC-HVdc) power systems, superconducting fault current limiter (SFCL) has received more and more attention, especially the resistive SFCL. However, when the resistive SFCL is in the current limiting state or overload operation, a large amount of bubbles will be generated on the surface of superconducting tape, thereby affecting the insulation performance of the SFCL. Experiments are performed by using a heater-built-in electrode system where bubbles are generated from the surface of the ground electrode. The test can simulate the actual working condition. The effect of bubbles on breakdown voltage of liquid nitrogen (LN2) is investigated under different types of voltage (negative lightning impulse, positive dc voltage, and composite voltage of negative lightning impulse and positive dc voltage) and different pressures. The results show that the breakdown voltage of LN2 decreases with the increase of the number of bubbles regardless the type of voltage, and elevating pressure is an effective way to improve the insulation strength of LN2. All the test data can be used as the theoretical basis for insulation design of resistive SFCL.