Saturated Core Fault Current Limiter Research Articles

A novel hybrid magnetic material based on three-phase saturated core fault current limiter

Installing a three-phase saturated core fault current limiter (TSFCL) is an effective method to limit the increasing short-circuit current in high-voltage alternating current (HVAC) systems. However, the traditional TSFCL uses silicon steels as its working material for the iron core, resulting in poor current-limiting effects, requiring a large DC excitation current, and having a slow response speed. Nanocrystalline alloys have advantages such as a lower saturation point, higher permeability in the unsaturated zone, and a steep B–H curve, making them highly suitable for TSFCL’s applications. However, their poor capability which withstands fault hindered their large-scale commercialization. Therefore, this paper proposes a novel hybrid magnetic material based on TSFCL (HMTFCL), where the materials of the working limbs are replaced by nanocrystalline alloys. Compared to TSFCL, the DC excitation current of HMTFCL decreases by 60.5%. And, the HMTFCL reduces the peak short-circuit current by 23%. Last, the magnetic flux intensity inside the working limb of HMTFCL is reduced to zero more quickly.

A Compact Saturated Core Fault Current Limiter Magnetically Integrated with Decoupling Windings

Traditional saturated core fault current limiters (SCFCLs) have fast rising fault state inductance that can limit faults automatically. However, the current limiting performance of traditional SCFCLs is insufficient. In order to improve this, some novel SCFCLs use additional air core reactors, resulting in a large volume and floor area. A compact saturated core fault current limiter magnetically integrated decoupling windings (CSFCL) is proposed in this study, which has the advantages of a smaller volume and floor area. The principle of the non-orthogonal decoupling method is firstly introduced. The core body of the CSFCL is then magnetically integrated with the decoupling windings in the form of non-orthogonal decoupling. Equivalent magnetic circuit and electric circuit analysis is carried out. An inductance calculation method for decoupling windings is proposed. Following this, a 220 kV simulation model is conducted based on the finite element method. Finally, a small-capacity prototype of the CSFCL and a test platform are designed to test it. The experimental results verify the correctness and feasibility of the proposed structure.

Hybrid Multifunctional Saturated-Core Fault Current Limiter

Saturated core fault current limiters are effective means to limit short-circuit currents in high voltage power systems. To solve its problems of a low rate of utilization and large loss, this study proposes a multifunctional saturated-core fault current limiter (MFFCL) with a hybrid excitation system. The MFFCL can limit the short-circuit current and control power flow to reduce losses. The composition and topological structure of the MFFCL are provided, an equivalent electromagnetic circuit model of the MFFCL is then established, and its working mechanisms of limiting current and regulating power flow are analyzed. Following this, a finite-element simulation model of the MFFCL is built to investigate its electromagnetic characteristics and verify its performance in terms of limiting current. The power flow regulation function of the MFFCL was verified through the field-circuit coupling method. Finally, a laboratory-scale prototype of the MFFCL and a test platform was designed to test it. The results of the experiments verified the correctness and feasibility of the proposed structure. It can adequately control power flow in its normal state, and can limit the short-circuit current to 60% of the original in case of a fault.

A Self-Activated Fault Current Limiter for Distribution Network Protection

Rapid protection of modern electric networks using fault current limiters (FCLs) is often delayed and limited by the inherent controller, sensor, and power electronic unit delays. This article proposes a novel self-activated FCL (SAFCL), comprising a dc saturation winding, series ac limiter windings, and ac parallel reactor, which limits the fault current in less than 0.4 ms. Furthermore, the advantage of this SAFCL, when compared to a traditional saturated core FCL (SCFCL), is that it does not rely on any external controller, sensor, controllable solid-state switch, and battery. In the normal state, the SAFCL behaves like a saturated reactor with a very low impedance and in the fault state, cores are entered to the unsaturation region without relying on an external controller which imposes a high impedance to limit the fault, rapidly. The performance of the SAFCL is evaluated through off-line MATLAB and Maxwell ANSYS FEM simulations, and is also validated by experimental studies conducted on a scaled-down prototype.

Single core configurations of saturated core fault current limiter performance of laboratory test models

Economic growth with industrialization and urbanization lead to an extensive increase in power demand. It forced the utilities to add power generating facilities to cause the necessary demand-generation balance. The bulk power generating stations, mostly interconnected, with the penetration of distributed generation result in an enormous rise in the fault level of power networks. It necessitates for electrical utilities to control the fault current so that the existing switchgear can continue its services without up-gradation or replacement for reliable supply. The deployment of fault current limiter (FCL) at the distribution and transmission networks has been under investigation as a potential solution to the problem. A saturated core fault current limiter (SCFCL) technology is a smart, scalable, efficient, reliable, and commercially viable option to manage fault levels in existing and future MV/HV supply systems. This paper presents the comparative performance analysis of two single-core SCFCL topologies impressed with different core saturations. It has demonstrated that the single AC winding configuration needs more bias power for affecting the same current limiting performance with an acceptable steady-state voltage drop contribution. The fault state impedance has a transient nature, and the optimum bias selection is a critical design parameter in realizing the SCFCL applications.

A modified bridge-type nonsuperconducting fault current limiter for distribution network application

The electrical distribution network is undergoing tremendous modifications with the introduction of distributed generation technologies which have led to an increase in fault current levels in the distribution network. Fault current limiters have been developed as a promising technology to limit fault current levels in power systems. Though, quite a number of fault current limiters have been developed; the most common are the superconducting fault current limiters, solid-state fault current limiters, and saturated core fault current limiters. These fault current limiters present potential fault current limiting solutions in power systems. Nevertheless, they encounter various challenges hindering their deployment and commercialization. This research aimed at designing a bridge-type nonsuperconducting fault current limiter with a novel topology for distribution network applications. The proposed bridge-type nonsuperconducting fault current limiter was designed and simulated using PSCAD/EMTDC. Simulation results showed the effectiveness of the proposed design in fault current limiting, voltage sag compensation during fault conditions, and its ability not to affect the load voltage and current during normal conditions as well as in suppressing the source powers during fault conditions. Simulation results also showed very minimal power loss by the fault current limiter during normal conditions.

Real-time implementation of ring based saturated core fault current limiter to improve fault ride through capability of DFIG system

Enhancement of fault ride-through (FRT) capability in doubly-fed induction generator (DFIG) system is presented in this paper. The saturated core fault current limiter (SCFCL) works on the behaviour of magnetic field induction theory. It is composed of the ferromagnetic core with three limb construction, where both side limbs are surrounded with AC coil and middle limb with DC coil. For the application of restrictive fault, the ideal SCFCL can work for only low-power rating machines. But for the machine higher power rating, the ideal SCFCL has a drawback of developing heat across the limbs, which can damage the insulation of the coils. To overcome this glitch, the embedding of the copper ring across center limb and using forced-air cooling in SCFCL is used. This ring-based SCFCL (RSCFCL) is placed across the stator of DFIG system, which helps in minimizing fault current during any grid disturbances. Having low impedance during normal condition, it can be located permanently in the system without disturbing its stability. The feasibility of ideal SCFCL and RSCFCL is validated by studying the characteristics using thermal radiation under normal and fault conditions. The use of infrared imaging helps to monitor the thermographic patterns of the core on several conditions. The performance of RSCFCL is analyzed with the help of experimental setup and real-time simulator OPAL-RT 4510. Also, to check its effectiveness, it is used for FRT capability in the DFIG system application.

Experimental analysis of saturated core fault current limiter performance at different fault inception angles with varying DC bias

Economic growth has exponentially increased the power demand resulting in bulk power systems. The distributed generations are also integrating into the grid network to retrieve the benefits of the locally available generating resources. Also, the high-reliability expectations of supply systems lead to the interconnection of power networks. All these modern characteristics escalated the magnitude of short circuit currents in the grids. The security from these currents, therefore, challenged the power network protection systems. The deployment of the scalable and reliable Fault Current Limiter (FCL) technology can enhance the service span of existing components in the power industry. The Saturated Core Fault Current Limiter (SCFCL) can be a commercially viable solution to this problem. This paper reports the test performance of a scaled-down, compact, novel, copper-coils-based SCFCL model. The steady-state and transient-state behavior have been characterized in terms of saturation levels and the fault inception angles. The importance of DC bias selection in the optimum current limiting performance of the device is demonstrated in the results. The results also exhibit that the fault inception at the peak of voltage causes the most asymmetric transient during the current limiting process. Also, the heuristic design methodology based on extensive experimental work has been proposed, taking into account an application of optimum DC bias.

A Novel Saturated Amorphous Alloy Core Based Fault Current Limiter for Improving the Low Voltage Ride Through Capability of Doubly-Fed Induction Generator Based Wind Turbines

This article proposes the use of a novel saturated amorphous alloy core-based fault current limiter (SAACFCL) to improve the low voltage ride through (LVRT) capability of doubly-fed induction generator (DFIG) based wind energy systems, especially during voltage sag events. Compared to the traditional cores, which are widely used in fault current limiter (FCL), amorphous alloy core possesses a very narrow B-H loop, which indicates that the SAACFCL requires a smaller dc excitation current, and it will incur low core losses. Under normal conditions, this developed SAACFCL accomplishes low impedance and has a negligible impact on the network operation. During grid faults, a deep voltage sag causes large fault currents that desaturate the SAACFCL core, increasing its impedance, which limits the fault currents and improves the LVRT capability of DFIG systems. The SAACFCL is designed and characterized by ANSYS software. To validate the performance of the SAACFCL, a DFIG-based system equipped with the SAACFCL has been modeled in MATLAB/Simulink. The simulation results with and without the SAACFCL show that the SAACFCL is capable to achieve the LVRT successfully and can meet the grid code requirement. The performance of the SAACFCL has also been compared with that of the saturated iron core FCL (SICFCL) and superconducting FCL (SFCL). The SAACFCL promises better performances than SICFCL and SFCL. A small scale SAACFCL has been designed, developed, and tested in the laboratory to check its performance. The experimental results show that the proposed SAACFCL can effectively reduce the level of fault current and mitigate voltage sag experienced by the DFIG.

Multi-objective optimization for the superconducting bias coil of a saturated iron core fault current limiter using the T-A formulation

The short-circuit levels have increased considerably in transmission and distribution systems in the last years. Fault current limiter (FCL) devices are a potential solution to this problem. Among several FCL topologies, this group has good experience in the use of superconducting fault current limiters (SFCL) to reduce the electrical current during short-circuits. The literature also presents studies of the saturated iron core superconducting fault current limiter (SIC-SFCL) topology employing mathematical modeling and prototypes design. Some of them have shown promising results, including the construction of pilot prototypes in medium and high voltage substations. The SIC-SFCL simulation studies presented optimal topologies that reduce the amount of ferromagnetic material used in the core and represent well the behavior of this limiter. The finite element method and the finite element analysis are suitable to model the SIC-SFCL. However, a more detailed study focusing on the optimization of the DC bias superconducting coil of the SIC-SFCL has not been presented in the literature yet. In this context, this work proposes a multi-objective optimization method using the Nelder–Mead algorithm to find an optimal geometry for the superconducting coil. In this optimization, the objectives functions are: to maximize the critical current density in the high-temperature superconductor (HTS), minimize the voltage drop in the copper winding, minimize the current through the DC biased superconducting winding, and minimize the price of the HTS superconducting winding. Before implementing the multi-objective optimization algorithm, we have tested a non-superconducting saturated iron core prototype and used the results to validate the simulation models. After that, we have replaced the DC copper winding with an HTS coil in the simulations and initiate the optimization process. Results show that constructing the DC bias superconducting coil using the minimum possible fill factor might not be the best choice.

Hybrid-Material Based Saturated Core FCL in HVDC System: Modeling, Analyzing and Performance Testing

In order to limit the extremely fast rising trend of fault current in a high voltage direct current system, a permanent magnet (PM) biased dc saturated core fault current limiter (DCSFCL) was proposed previously. However, the demagnetization problem of the PM and compromised fault limiting inductance value caused by the inserted PMs are two major issues that need to be solved. In this article, a hybrid-material based fault current limiter (HMFCL) is proposed. First, by means of reconstructing the iron core topology and substituting different soft magnetic materials with their hybrid benefits, the proposed novel HMFCL can present instant change in fault limiting inductance value without threating the safety of the PMs. Then, the Jiles-Atherton hysteresis modeling technique is applied on the HMFCL and its electromagnetic feature is analyzed. The parameters of HMFCL are optimized using genetic algorithm as well. Finally, the effectiveness of the proposed HMFCL is proved by various device and system level simulations as well as a prototype experiment. Results reveal that the proposed HMFCL can limit the fault current by over 80% compared with traditional smoothing reactor.

A Novel Modularization Design Method of PM Biased SCFCL Considering Leakage Flux Effect and Permeance Matrix Modeling

A DC system saturated core fault current limiter (DCSFCL) was proposed to limit the fast rising trend of fault current in HVDC system. However, traditional method to calculate and design the DCSFCL tend to neglect leakage flux around the permanent magnet (PM), leading to large calculation error and inappropriate design procedure. The novel contribution of this paper is that it proposed a modularization method to analyze the permeance of both PM and adjacent air. Hence, the leakage flux effect is considered properly and a more accurate permeance matrix can be derived in a pure mathematical way. In this case, DCSFCL can be calculated much faster than the FEA simulation program with a promising accuracy regarding fault limiting performance. More importantly, design flow of the DCSFCL and related PM biased devices was given as well. Calculation result shows that inductance value calculated by the proposed method has less than 1% error compared with fine meshed FEA simulation result and about 20% increase in accuracy compared with traditional method that neglects PM leakage flux effect. Prototype of the DCSFCL was also built and experimental tests were carried out to verify the correctness of the proposed method.

Saturated‐core fault current limiters for AC power systems: Towards reliable, economical and better performance application

With the continuous expansion of power grid capacity, the problem of short-circuit current exceeding the standard is becoming increasingly serious. Fault current limiter is a promising solution and is gradually becoming a research hotspot. In this study, fault current limiters are classified into four categories. And saturated-core fault current limiters are emphatically introduced, including its working principle and comparison with the other three categories. Saturated core fault current limiters are divided into four branches according to the ways leading the core saturated. A comprehensive review of the research activities and emerging technologies of saturated-core fault current limiters for AC power systems is presented in this study. The working principle and typical structure of DC-biased-, permanent-magnet-, superconducting- and hybrid-type saturated-core fault current limiters are introduced. The advantages and disadvantages of four types of saturated core fault current limiters are compared in detail from the aspects of current-limiting performance, iron core size and DC magnetomotive force. Real grid application examples of some types of devices are presented, as well as new progress in the techniques, are covered and discussed in detail. One may find the content of this study helpful as a detailed literature review or as practical technical guidance.

Optimized Design Method of Permanent Magnets Saturated Core Fault Current Limiters for HVDC Applications

When the fault current in high voltage direct current (HVDC) systems rises to a higher level, the DC circuit breakers will have either insufficient capacity or will require larger sizes with increased costs. Fault current limiters (FCLs) can reduce the turn-off stress and the stringent requirements on breakers, thereby also lowering their cost. The use of saturated core FCLs, which have fast response times and low power loss, is a promising approach for this issue. However, the parameter design principles for this kind of FCL has so far not been discussed in the literature. The design is often based on reactors that does not consider the transient performance. In this study, an optimized design method for permanent magnets saturated core FCLs in HVDC transmission systems, is proposed. The constraint conditions, parameter optimization and modification steps are discussed, and an optimized FCL design is obtained with the lowest cost and expected current-limiting function. Both simulations and experiments are conducted, and the results demonstrate the validation of the proposed method. Finally, a cost evaluation among main types of inductive FCLs is carried out and suggestions for scaling up saturated core FCLs to HVDC applications are given.

Modeling and Simulation of a Saturated Core Fault Current Limiter Integrated in a Typical Distribution System Based on PSCAD Environment

Due to load increasing and generation extensions of the electrical networks, the fault current levels may be largely changed. So, the short circuit capacity may easily exceed the installed equipment interrupting capacity such as circuit breakers. Nowadays there are different methods for restoring the fault current normal values. The traditional methods in power utilities consider one of three options: (1) Replace installed equipment with higher rated equipment or, (2) Install series reactors or, (3) Replace the existing transformers with high impedance transformers. In this paper a Saturated Core Superconducting Fault Current Limiter (SCSFCL) will be presented as an efficient method for solving this problem so that replacing existing circuit breaker infrastructure can be avoided or postponed. This paper simulated the SCSFCL based on the PSCAD environment. An 11 kV West Delta Egyptian Distribution System in TANTA region is modeled as a typical system with the proposed simulated model of SCSFCL. The model parameters are adapted by the authors to restore the fault current levels as their values before the integration of the Distributed Generation (DG) units. The obtained results ensure that the model is easily used in other distribution systems. The results show also that the model performances can meet utility’s needs in mitigating fault current at all types of fault and different fault positions

Phase-Coupling Effects in Three-Phase Inductive Fault-Current Limiter Based on Permanent Magnets

In this article, a novel concept of an inductive, saturated-core fault-current limiter (FCL) design is presented, capable of limiting three-phase faults. The design is based on high-remanence permanent magnets for biasing high-saturation electrical steel cores, thus minimizing the device volume, dimensions, and cost and allowing a relatively easy assembly process due to the magnetic symmetry of the model. By implementing a three-phase design in a single device, we harness the full potential of each magnet, substantially reducing the required material for achieving negligible losses during nominal operation while increasing current limiting during faults. A laboratory-scale, low-voltage prototype has been built and tested to prove the feasibility of the new concept, suggesting that upscaling to higher voltage devices is plausible. Extensive simulations, using finite-element analysis, have yielded insight into several measured phenomena, including a unique phase-coupling effect experienced during three-phase fault measurements.

Limiting mechanism and equivalent analytical model of a bridge-type saturated core fault current limiter

A saturated core fault current limiter (SCFCL) is a promising device to limit the fault current. Due to the nonlinear characteristics of the ferromagnetic materials and the AC to DC coupling effect, traditional equivalent models of SCFCL are not accurate. Moreover, the impact of the DC biasing magneto-motive force (MMF) attenuation on the limiting mechanism is lack of attention. Hence, this paper proposes an accurate limiting mechanism and an equivalent analytical model of a bridge-type SCFCL (BSFCL), considering the AC to DC coupling effect and the DC MMF attenuation. This paper presents the limiting mechanism of the BSFCL based on three working regions. Then an equivalent analytical model considering the coupling effect and the DC MMF attenuation characteristics is established. Finally, the limiting mechanism and an equivalent analytical model of BSFCL are validated by the analytical model method, electromagnetic simulation and experiments. The simulation and experimental results demonstrate the effectiveness and accuracy of the proposed method.

Development of improved direct current based saturated core fault current limiter in DFIG system for enhancing the low voltage ride‐through capability

With the increase of electrical energy consumption and associated power grid expansion the complexity in the grid network increases which tends to increase the fault occurrence possibilities. Low voltage ride-through capability helps the system to achieve the standard of grid code by remaining connected with the grid during fault occurrence. Direct current-based saturated core fault current limiter (DC-SCFCL) is a type of fault current limiter with superior influence in fault ride-through (FRT) capability. It has an arrangement of embedded alternating current coil and direct current (DC) coil across the side and centre of the core limb. However, being more effective in FRT, the ideal DC-SCFCL has some of its drawback such as development of high voltage across the DC coil and more current difference during fault occurrence. To limit these drawbacks a modified DC-SCFCL with shorted ring and also working with the coil below its critical temperature has been proposed in this study. The voltage profile, as well as the current profile, has been analysed which comprises its behaviour in all conditions. The proposed technique is applied to DFIG-based wind energy system to restrict the fault current and enhance the FRT capability.

A Novel Six-Leg Three-Phase Fault Current Limiter

A fault current limiter is an effective mean of limiting fault currents. The simultaneous use of three single-phase current limiters requires significant amounts of ferromagnetic material and space. This article proposes a three-phase saturated-core fault current limiter (T-SCFCL) that employs a common yoke and a permanent magnet to mitigate the restrictions of material and space. T-SCFCL delivers good performance for single-phase, two-phase, and three-phase faults. In this configuration, flux flowing through the permanent magnets is generated by a three-phase unbalanced current, thereby reducing the loss in eddy current and improving stability while significantly reducing the volume of the core. An algorithm is provided for use in the design of the FCL structure. A simulation was conducted based on the finite element method and a prototype manufactured and tested to verify effectiveness. The results prove that the proposed method is efficient.

Performance Investigation on a Novel High Inductance Changing Ratio MMC-Based Direct Current System Saturated Core FCL

Large fault direct current with fast rising speed has always been a significant threat to high voltage direct current systems. Fault current limiters (FCLs) are one of the most promising solutions. However, the biased permanent magnets (PM)s in traditional FCLs have large magnetic reluctance that causes FCLs to have small inductance changing ratios when a fault occurs. In this study, a novel three-limb topology of a saturated iron core-type fault current limiter (TSFCL) is proposed and a central PM bias limb is inserted to force flux flow through this limb. Therefore, the inductance changing ratio is greatly enhanced and the steep rising trend of fault current will be restrained effectively. The operating principles and characteristics of the TSFCL are analyzed to verify the deductions. Moreover, different lengths and cross-sectional areas of the inserted PM are tested and optimization study is carried out. The results show that the clipping inductance has a 55% increase compared with a traditional two-limb model. Moreover, compared with the existing smoothing reactor and traditional two-limb model, proposed topology can decrease the fault current by 45% and 16% within 5 ms, respectively. Finally, a typical HVDC system was built and the effectiveness of proposed TSFCL was verified.