Iron-core Superconducting Fault Current Limiter Research Articles

Combining finite element and reinforcement learning methods to design superconducting coils of saturated iron-core superconducting fault current limiter in the DC power system.

A saturated iron-core type superconducting fault current limiter (SI-SFCL) can effectively restrict the magnitude of the fault current and alleviate the strain on circuit breakers in DC power systems. Design of a superconducting coil (SC), which is one of the key tasks in the SI-SFCL design, requires guaranteeing a sufficient magnetic field, ensuring optimization of the shape and size, minimizing the wire cost, and satisfying the safety and stability of operation. Generally, finite element method (FEM) is used to calculate and evaluate the operating characteristics of SCs, from which it is possible to determine their optimal design parameters. When the coil is complex and large, the simulation time may range from hours to days, and if input parameters change even slightly, the simulations have to be redone from scratch. Recent advances in deep learning represent the ability to be effective for modeling and optimizing complex problems from training data or in real-time. In this paper, we presented a combination of the FEM simulation and deep Q-network (DQN) algorithm to optimize the SC design of a lab-scale SI-SFCL for a DC power system. The detailed design process and options for the SC of SI-SFCL were proposed. In order to analyze the characteristics related to the electromagnetic properties and operational features of the SC, a 3D FEM model was developed. Then, a DQN model was constructed and integrated with the FEM simulation for training and optimizing the design parameters of the SC in real-time. The obtained results of this study have the potential to effectively optimize the design parameters of large-scale SI-SFCL development for high-voltage DC power systems.

DVR Transient Analysis with Saturated Iron-Core Superconducting Fault Current Limiter

Abstract: The saturated iron-core super conducting fault current limiter exceeds all other fault current limiters in terms of technical performance. Based on the real structure, magnetic structures have been proposed. Simulated current limiting inductance was calculated using the Newton iteration method and the fundamental magnetization curve. Sagging and soaring current levels occurred frequently during the faulting process. Short circuits and voltage fluctuations are two of the most typical grid-related issues.. The use of the SISFCL and DVR in this project resulted in a reduction in the amount of fault current and voltage variation. With the help of Matlab/Simulink and theoretical insights from previous research, we were able to construct an electromagnetic transient simulation model. The transient behavior of these devices during simulation tests demonstrates the accuracy and validity of the suggested strategy. Keywords: Analysis of transient electromagnetic waves in a saturated iron core using a Newton iteration method. Fault current limiter (SISFCL), dynamic voltage restorer (DVR), pulse width modulation (PWM)

Combined Operation Analysis of a Saturated Iron-Core Superconducting Fault Current Limiter and Circuit Breaker for an HVDC System Protection

Recently, in order to overcome the difficulties of interrupting fault currents in multi-terminal direct current systems (MTDC), studies combining a saturated iron-core type superconducting current limiter (SFCL) and a direct current circuit breaker (DCCB) have been conducted. However, the effect of inductance change of the SI-SFCL on the interrupting time of the DCCB during fault has not been studied yet. In this paper, the interrupting time delay caused by the dynamic behavior of the inductance change during the fault current blocking process of the SI-SFCL combined with a DCCB was analyzed through experiments and a new fault detection method considering this phenomenon was proposed. After designing and manufacturing the laboratory-scale SI-SFCL and DCCB, a fault current interrupting test was performed and the inductance change pattern of the SI-SFCL was analyzed. Based on the analysis results, a new fault detection technique was proposed to alleviate the interruption time delay that occurs when applying the combined protection system to a MTDC, and its effectiveness was verified through a simulation. These results will be useful for planning protection coordination strategies when introducing a SI-SFCL in combination with a DCCB in actual MTDC systems.

Losses in the Saturated Iron-Core Superconducting Fault Current Limiter For VSC-HVDC System

This paper presents the loss analysis on the saturated iron-core superconducting fault current limiter (SISFCL) for a VSC-HVDC transmission system. The numerical model of SISFCL as well as its loss calculation on superconducting parts were carried out by the finite-element method (FEM) using the H-formulation merged into the commercial package COMSOL. The SISFCL model was established for a practical ±10 kV VSC-HVDC system, and the fault current situation was simulated using the PSCAD with a SISFCL. The capability of fault current limiting was verified using the analysis of electromagnetic characteristics, and the corresponding patterns of magnetic field in the iron-core were studied. During the process of fault current limiting, the instantaneous power losses in the superconducting components were studied with the increasing DC bias current. Even in a DC grid system, results proved there were considerable amounts of losses occurred in the superconducting parts, when the SISFCL encountered the fault currents.

Saturated Iron-core Superconducting Fault Current Limiter for VSC Network: System Modeling With Loss Analysis

The potential application of the superconducting fault current limiter (SFCL) in a voltage source convert (VSC) system has received lots of attention. On the basis of the fault current limiting characteristics, this paper evaluated the loss level of saturated iron-core FCLs (SI-SFCLs) in a VSC-based distribution grid. The models of VSC network and the SI-SFCL model were respectively developed. Then, with and without the implementation of SI-SFCLs, the fault current process under positive-to-ground and positive-to-negative short-circuit was presented. Next, the power dissipated from the superconducting coil was curved. Analysis demonstrated the power dissipation of the SI-SFCL during the short-circuit is likely to reach tens of kilowatts. This study can provide a helpful guidance for the design of SI-SFCLs.

Experimental Study on the Current Limiting Characteristics of a Saturated Iron-Core Superconducting Fault Current Limiter in DC Power Systems

Several recent studies have proposed a conceptual design of a saturated iron-core superconducting fault current limiter (SI-SFCL) for DC power systems, but experimental studies to verify its operating characteristics and performance have not yet been conducted. In this paper, a laboratory-scale SI-SFCL was designed and tested to operate in a 500 V, 50 A DC power system. First, the detailed configuration, specifications, and hardware manufacturing contents of the SI-SFCL were presented, and then an experimental circuit was developed and installed for the performance test of the SI-SFCL in normal operation and failure conditions. A 3D finite element method model was constructed to compare the simulation results and experimental results for the operating function of the SI-SFCL. Without the SI-SFCL, the maximum fault current level was 500 A, as a result, the SI-SFCL has a large current limit function, which can reduce the magnitude of the fault current up to the design target value of 73.6%. The results obtained in this study can be effectively applied to large-scale SI-SFCL development studies for HVDC power systems.

Design and Performance Analysis of a Saturated Iron-Core Superconducting Fault Current Limiter for DC Power Systems

A saturated iron-core superconducting fault current limiter (SI-SFCL) can significantly limit the magnitude of the fault current and reduce the stress on circuit breakers in direct current (DC) power systems. The SI-SFCL consists of three main parts: one magnetic iron-core, one normal conductive primary coil (CPC), and one superconducting secondary coil (SSC). This paper deals with the design options for the coil system of the SI-SFCL and confirms their operating characteristics through a physical experiment. The electromagnetic characteristics and operational features of the SI-SFCL was analyzed by a 3D finite element method simulation model. The design of the SSC was based on shape, wire types, required fault current limit and protection aspects. In the CPC, the bobbin was designed based on material selection, cost, structural design, and the effects of the SI-SFCL on the fault current limit. Based on these simulation results, a laboratory-scale SI-SFCL was developed, specifically fabricated to operate on a 500 V, 50 A direct current (DC) power system. In the experiment, the operating characteristics of each coil were analyzed, and the fault current limit of the SI-SFCL according to the operating currents of the SSC and bobbin design of the CPC were confirmed. Finally, the cost analysis of the SI-SFCL with the proposed design options of the coil system was implemented. The results obtained through this study can be effectively used to large-scale SI-SFCL development studies for high-voltage direct current (HVDC) power systems.

Conceptual Design of a Saturated Iron-Core Superconducting Fault Current Limiter for a DC Power System

A superconducting fault current limiter can significantly reduce the stress on the DC circuit breaker in DC power systems due to its inherent physical characteristics that can quickly limit the fault current. This letter presented the conceptual design of a saturated iron-core superconducting fault current limiter (SI-SFCL) for DC power systems. First, the electrical characteristics of the SI-SFCL were investigated. Then, a detailed design process and corresponding configuration of the SI-SFCL for a 15 kV, 3 kA DC power system were presented. A PSCAD/EMTDC simulation model was built to analyze the operating and fault current limiting characteristics of the SI-SFCL. To demonstrate the effectiveness of the conceptual design parameters and configuration, a lab-scale SI-SFCL for a 500 V, 50 A DC power system was designed in detail. The fault current limiting capability of the lab-scale SI-SFCL was confirmed by the 3D finite element method. As a result, the lab-scale SI-SFCL has a high current limiting capability, which can reduce the magnitude of the fault current by up to 75%. This study results will be effectively applied to a large-scale SI-SFCL for HVDC power systems.

Performance analysis of an open-core type three-phase saturated iron-core superconducting fault current limiter

Abstract A very common kind of fault that appear in an electrical power system is the short-circuit fault, which were traditionally handled by the use of protective devices like fuses or circuit breakers which would disconnect the power supply to protect the components of the network. An alternative to these are fault current limiters (FCL), which are protective devices that limit or suppress the high-magnitude currents created during a short-circuit fault, thereby preventing damage to sensitive equipment and also aid in providing uninterrupted power supply to the consumers. A saturated iron-core superconducting fault current limiter (SISFCL) employs the ferromagnetic property of its core material to automatically suppress high-magnitude currents. In this paper, the performance of an open-core type three-phase SISFCL design is evaluated against three different kinds of short-circuit faults. The analysis is performed using finite element modelling (FEM) in the ANSYS Maxwell software environment.

Research on the Magnetic Properties of Iron Core for Saturated Iron-Core Superconducting Fault Current Limiter

The magnetic field of iron core is excited by the interaction of both direct current (dc) and alternating current for the saturated iron-core superconducting fault current limiter (SI-SFCL), which will reach a relatively high level as 2 T or above. On account of using different methods to describe the magnetic property of the iron core, the simulation results of the magnetic field and loss of iron core will be different, we use a new method to measure its magnetized characteristic, especially in saturated state. In this paper, we have studied the definition of the magnetized property for SI-SFCL under dc bias current in detail. On the basis of the experimental data of grain-oriented electrical steel, we plot the hysteresis loop and the magnetization curve of the electrical steel. The rightness of the definition is verified by using simulation analysis and experimental test. At last, the research results mentioned earlier are applied to analyze a 380-V SI-SFCL.

Investigation on Power Dissipation in the Saturated Iron-Core Superconducting Fault Current Limiter

This paper presents the power dissipation analysis on saturated iron-core superconducting fault current limiter (SISFCL). The modeling of SISFCL together with its power dissipation computation on a high-temperature superconducting (HTS) coil was executed by the H-formulation model implemented into the finite element method (FEM) software package COMSOL. The model was based on the practical three-phase 35-kV/90-MVA SISFCL. The ac magnetic field in the crucial parts of SISFCL was studied to discover the origin of power loss on the HTS coil. The instantaneous power dissipations in the HTS coil with increasing dc bias current were computed and compared. Analysis proved that power dissipation in the HTS coil of SISFCL should be taken into account for the real operation.

Study on the Working Current of the Superconducting Coil and the Equivalent Circuit of HTSFCL

This paper mainly describes the designing progress of iron-core saturated high-temperature superconducting fault current limiter (HTSFCL). First, the relationship between magnetic field and current of high temperature superconducting coil is simulated in the finite element software, which can get the working current of superconducting coil of 70 A. Then, using the simulation results of coil, the design formula is deduced, and the size of HTS current limiter and the number of coil turns are calculated. Third, the HTSFCL model is established in the finite element analysis software to obtain the field distribution and short-circuit characteristics from the simulation results, and calculate the equivalent parameters. The equivalent circuit of HTSFCL is established in the circuit analysis software, and the correctness of the equivalent circuit is verified by comparing different simulation results. Finally, through the test of HTS coil, the working current of the superconducting coil is verified to be 70 A.

Study of the Application of Active Saturated Iron-Core Superconductive Fault Current Limiters in the VSC-HVDC System

As a typical inductive type superconductive fault current limiter (SFCL), the saturated iron-core SFCL (SI-SFCL) is very important to the safety of the VSC-HVDC system. Considering that the high-induced voltage of the superconductive winding may cause damage to the dc-bias source, an active SI-SFCL, which can quickly cut off the dc-bias source branch, is introduced to limit the dc fault current. This paper first describes the building of a transient analysis model of the active SI-SFCL and, presents the VSC-HVDC system equivalent circuit with the active SI-SFCL deployed. Moreover, the method of solving the state equations of the equivalent circuit is obtained. On this basis, the influence of the protective voltage of the metal oxide arrester on the current-limiting performance is studied. Finally, the correctness of the transient analysis model, and the effectiveness of the theoretical analysis method are verified by MATLAB/Simulink simulations.

Analysis of Magnetic Circuit and Leakage Magnetic Field of a Saturated Iron-Core Superconducting Fault Current Limiter

The saturated iron-core superconducting fault current limiter (SISFCL) is considered to be an effective solution to reduce the impact of fault current and increase the reliability of the power grid. This paper presents the basic structure and the electromagnetic analysis of SISFCL. In order to study the leakage magnetic flux distribution of the SISFCL, two approaches have been used to model the transient behavior of such device. The leakage magnetic flux distribution of the limiter was calculated, respectively, by using the finite element method (FEM) and the magnetic field division method. By considering the SISFCL as a controlled voltage source dominated by the flux through the ac coils, we establish a magnetic circuit. With the magnetic circuits, we calculate the steady-state impedance. Comparing the results with the FEM model, we verify the validity of the equivalent magnetic circuit model.

Research and progress in developing key technologies for practical saturated iron-core superconducting fault current limiters

Saturated iron-core superconducting fault current limiter is one of the various types of superconducting fault current limiters studied in recent years. The principle was first proposed by Raju’s group in the early 1980’s, which utilizes the intrinsic property of a magnetic core, i.e. change in magnetic permeability at different magnetization states, resulting in the change in impedance of the coil wound around it. There have been some technical difficulties for it to satisfy the utility’s requirement in functional capacity, safety, and reliability, which prevents this kind of device from practical application. This article introduces our progresses in solving these technical difficulties in last ten years. These progresses include: ensuring a deep and stable saturation of the iron-core’s working section by cross-sectional area variation of the core in a loose coupling structure, paving the way for high voltage grid applications; adopting a fast switching mechanism for the DC bias circuit to avoid high induced voltage during fault current limiting, protecting the device from damaging and enhancing its operation safety; by meas of the combination of high power mode and low power mode in magnetization and the use of varistor energy release unit, shortening the device’s recovery time to satisfy the grid re-closure requirement; taking on the three phases in one configuration to optimize the iron-core structure, reducing the size and the weight of the device and lowering the costs of manufacture, transportation and installation; eliminating the problem of induced eddy current and large coupling current on a metal oil-tank by using separated fiber glass oil-tanks. These new technologies make a saturated iron-core superconducting fault current limiter an ideal short-circuit fault current limiting device, a superior choice particularly for high voltage power grids.

Studies on the active SISFCL and its impact on the distance protection of the EHV transmission line

The active saturated iron-core superconductive fault current limiter (SISFCL) is a good choice to decrease fault current. This paper introduced the principles and impedance characteristic of the active SISFCL. Then, it shows the current-limiting effects of the SISFCL. Besides, the impact of the active SISFCL on the distance protection of the EHV transmission line is evaluated. Based on that, the coordination scheme of the distance protections is proposed. A 500 kV double-circuit transmission system with SISFCLs is simulated by Electro-Magnetic Transients Program including DC (EMTDC). Simulation tests demonstrate the correctness and validity of theoretical analyses.

Research on Saturated Iron-Core Superconductive Fault Current Limiters Applied in VSC-HVDC Systems

The high-voltage direct-current transmission based on voltage source converter (VSC-HVDC) system has pointed the way for the development of the smart grid, yet one challenge to be faced is that VSCs are vulnerable to dc short-circuit faults due to the huge discharge current of the dc-link capacitor. Therefore, the saturated iron-core superconductive fault current limiter (SI-SFCL) is introduced to limit the fault current to a relatively low level. The working principle and electrical properties of the SI-SFCL are discussed first. The relationship between the inductance and dc gird current of the SI-SFCL is deduced. The transient process of a short-circuit fault in the VSC-HVDC system with the SI-SFCL is studied. The maximum current and the drop velocity of dc rail voltage are presented according to the parameter of the SI-SFCL. The effectiveness of the SI-SFCL is proved by comparing fault currents and voltages of the VSC-HVDC system with and without it in PSPICE.

Performance Analysis of SISFCL with the Variation of Circuit Parameters using Jiles Atherton Hysteresis Model

Abstract In modern day power systems, fault current limiters (FCL) are used to provide protection from high fault currents in the event of electrical faults and thus help to deliver uninterrupted electric supply to the consumers. Several technologies of FCLs are available for practical usage. However, the saturated iron-core superconducting fault current limiter (SISFCL) has gained a lot of attention in recent years in view of its ability to offer very low impedance during normal operation and high impedance during faulted condition. Previous mathematical models defining the performance of the device employs a simple BH curve. But as the change in mathematical state of saturation and unsaturation is important for the operation of the device, the paper investigates the responses considering the effects of magnetic hysteresis utilising the Jiles Atherton hysteresis model. Further the performance of the device is analysed with the variations of different parameters viz., the fault resistance magnitude, DC bias current, number of turns of the AC winding and number of turns of the DC winding that portray the effectiveness of the parameters encouraging an optimal design of the limiter.

Current limiting impedance comparison between different designs of iron cores of the flux‐lock‐type superconducting fault current limiter

Fault current limiters are playing an ever more important role in today's power systems and many of their different types have now reached maturity. Owing to the progress in superconducting technology, the superconducting fault current limiter (SFCL) has attracted increasing attentions. To investigate the efficacy of SFCL devices from a system point of view, the fault current limiting impedance is of great importance. This study proposed an improved structure of flux-lock type of SFCL and compares the current limiting impedance of different layouts. It focuses on the impacts of iron core shape on primary winding inductance. The analyses include simulations based on finite element method carried out in the simulation software ANAlysis SYStem (ANSYS). This study shows that an E-E-shaped core with an air gap is better than a closed core when being used for an SFCL. It is also found that for an iron core SFCL with fixed size, its rated fault current limiting impedance can be adjusted by changing the cross-sectional area of the iron core centre leg and the length of the air gap.

Electromagnetic Transient Analysis of the Saturated Iron-Core Superconductor Fault Current Limiter

Superconducting fault current limiters offer superior technical performance in comparison with conventional methods to limit fault currents. Due to prominent advantages and practical demand, the saturated iron-core superconductive fault current limiter (SISFCL) has been applied on transmission lines and distribution system. Considering the actual structure, the sophisticated equivalent magnetic circuit of the SISFCL was proposed first in the paper. Based on those above, the electromagnetic transient simulation model of the SISFCL was built in Matlab/Simulink. To realize accurate electromagnetic transient simulation, Newton iteration method and fundamental magnetic magnetization curve are introduced into the calculation of the current-limiting inductance during simulation. The transient behavior of the SISFCL in simulation tests illustrated that the proposed method is valid and correct.