Fault Current Limiter Topology Research Articles

Multi-physics modelling and performance analysis of an air-core reactor in the framework of solid-state fault current limiters

This study presents a comprehensive multi-physics modelling of an air-core reactor operating within a solid-state fault current limiter. By utilizing an air-core reactor in the solid-state fault current limiter, it is aimed to avoid magnetic saturation and assess a conventional fault current limiting device within a contemporary fault current limiter topology. Within the employed fault current limiter topology, the air-core reactor not only limits fault current during grid faults but also carries nearly the entire network current under normal operational conditions. Therefore, the performance of air-core reactor is investigated through thermal, electromagnetic and electrostatic aspects for normal and fault conditions. A 380 V test prototype is employed to validate the coupling of reactor model and electric circuit dynamics in the simulations. Furthermore, current results of high voltage simulations are supported by PSCAD results to reveal the results accuracy. During the operation of air-core reactor in normal and fault cases, the distribution of heat originating from eddy and resistive losses was examined through convection, radiation and conduction mechanisms. Moreover, the electric field intensities affecting the reactor are obtained for different operating conditions through electrostatic analysis, whereas the electromagnetic analysis reveals the magnetic flux densities and magnetic forces acting on the reactor.

Research on a Secondary Active Limiting DC Fault Current Limiter Topology

The current-limiting performance of the smoothing reactor is weak. The traditional saturated core-type fault current limiter (TFCL) is better, but will cause the dc circuit breaker (DCCB) to endure high overvoltage, energy absorption and also increase the current fall time. When DCCB recloses on the permanent fault, the whole dc system will face a harmful second shock that cannot be solved effectively by TFCL. To solve the above problems, a secondary active limiting fault current limiter (SAFCL) topology is proposed. It can reduce the DCCB overvoltage and energy absorption greatly. Meanwhile, it can store fault energy and uses it to active limit the current when the DCCB recloses on the permanent fault. The secondary active current limiting effect is better than the first and the DCCB breaking electric stress is lower than the first. First of all, the topology and principle of the SAFCL are introduced. The main electromagnet parameters are then analyzed. The performance of different FCLs are simulated comparatively to verify the superiority of the SAFCL. Final, the experiment is carried out, the comparison with simulations verifies the feasibility of the SAFCL.

A novel fault current limiter topology design based on liquid metal current limiter

The liquid metal current limiter (LMCL) is regarded as a viable solution for reducing the fault current in a power grid. But demonstrating the liquid metal arc plasma self-pinching process of the resistive wall, and reducing the erosion of the LMCL are challenging, not only theoretically, but also practically. In this work, a novel LMCL is designed with a resistive wall that can be connected to the current-limiting circuit inside the cavity. Specifically, a novel fault current limiter (FCL) topology is put forward where the novel LMCL is combined with a fast switch and current-limiting reactor. Further, the liquid metal self-pinch effect is modeled mathematically in three dimensions, and the gas-liquid two-phase dynamic diagrams under different short-circuit currents are obtained by simulation. The simulation results indicate that with the increase of current, the time for the liquid metal-free surface to begin depressing is reduced, and the position of the depression also changes. Different kinds of bubbles formed by the depressions gradually extend, squeeze, and break. With the increase of current, the liquid metal takes less time to break, but breaks still occur at the edge of the channel, forming arc plasma. Finally, relevant experiments are conducted for the novel FCL topology. The arcing process and current transfer process are analyzed in particular. Comparisons of the peak arc voltage, arcing time, current limiting efficiency, and electrode erosion are presented. The results demonstrate that the arc voltage of the novel FCL topology is reduced by more than 4.5 times and the arcing time is reduced by more than 12%. The erosions of the liquid metal and electrodes are reduced. Moreover, the current limiting efficiency of the novel FCL topology is improved by 1%‒5%. This work lays a foundation for the topology and optimal design of the LMCL.

A Novel Fast Energy Storage Fault Current Limiter Topology for High-Voltage Direct Current Transmission System

The traditional saturated core type fault current limiters (TFCLs) cause large energy absorption and high overvoltage in direct current circuit breakers (DCCBs). Energy absorbing FCLs (AFCLs) cause coils to bear the fault current for a long period and the fault energy absorption is slow. In order to solve the problems of TFCLs and AFCLs, a novel fast energy storage dc FCL (EFCL) topology is proposed in this article. The EFCL not only reduces the overvoltage and energy absorption of DCCBs but also quickly stores energy. First, the working principle and topology of the EFCL are proposed. The design requirements of the main electrical and core size parameters are then analyzed. Then, the key electrical parameters are optimized by electromagnetic circuit simulations. The economy is analyzed. Finally, the whole process simulation and FCL comparison simulation are carried out. The feasibility of the EFCL is verified by the comparison of simulation with experiment.

A New Type of Fast-Response Fault Current Limiter Topology for HVDC Application

The inductance of a permanent magnet-biased saturated fault current limiter (PMFCL) increases automatically with the fault current. It can quickly restrain the rising speed of direct current (dc) fault current. However, when the dc circuit breaker (DCCB) opens, the PMFCL will delay the current drop speed and generate overvoltage, which will increase the voltage stress on the DCCB. In this article, a new type of fast-response FCL (NFCL) is proposed. It has the advantage of improving the fault current drop speed. Besides, it can reduce DCCB overvoltage, thus protecting the expensive insulated gate bipolar transistors in the DCCB. In addition, it greatly reduces the energy absorption in the DCCB, thus reducing its manufacturing cost. The NFCL operates automatically without a control device, which means that it responds faster. Moreover, the diode is on the low-voltage side, meaning that insulation manufacturing cost can be reduced. First, the working principle of NFCL cooperation with the DCCB is introduced. Then, the main electromagnetic parameter design requirements of the NFCL are analyzed. Their feasibility is verified by electromagnetic circuit simulation, and a prototype is built and tested. Finally, the experimental and simulation results show that NFCL can improve current drop speed effectively.

Simulation and experiment of a new DC fault current limiter topology

With the development of high voltage direct current (HVDC) power transmission system, it is imperative to develop a practical current limiting device which can effectively protect the converter from the influence of fault current. Based on the topology of current limiter proposed in previous papers, considering the requirements of practical application conditions, an optimized topology is proposed, which consists of snubber circuit and arrester, both in simulation and experiment. In addition, the RC buffering circuit is added and the parameters are optimized to reduce the voltage impulse that the IGBT of fault current limiter would else bear. Simulation and experiment are carried out in DC system. Both simulation and experiment results can prove the effectiveness of the optimized current limiter circuit.

Study of Liquid Metal Fault Current Limiter for Medium-Voltage DC Power Systems

Fault current limitation is an urgent but challenging technology for medium-voltage dc (MVDC) power systems. For a liquid metal current limiter (LMCL), the arc discharge characteristics often determine its current-limiting properties. The evolving arc in liquid metal is measured by contacting voltage probes, and the properties of the formed dumbbell-like arc column are studied and discussed in detail. It indicates that the total arc voltage almost behaves as a linear function of arc current for an LMCL. Besides, a simplified numerical arc model based on magnetohydrodynamics theory is built and solved by the software FLUENT. It is concluded that the temperature rather than the slightly fluctuant pressure dominates the arc properties, which coincides well with test results to some extent. Finally, a fault current limiter topology including serial LMCLs and parallel resistors is put forward, whose feasibility for MVDC application is discussed on the basis of its current-limiting behaviors.

A Novel Hybrid Saturated Core Fault Current Limiter Topology Considering Permanent Magnet Stability and Performance

The saturated core fault current limiter (SFCL) is one of the most effective methods for limiting fault current. A permanent magnet (PM)-biased SFCL (PFCL) can reduce dc bias current and additional energy consumption. However, the thermal stability of NdFeB PMs in PFCL poses a major challenge. This paper proposes a novel hybrid-type SFCL (HSFCL) topology that can reduce this risk. In the HSFCL, a hybrid PM/dc coil is designed to saturate the core, and a fault-limiting reactor is used to guarantee fault-clipping performance. The new structure provides air-gap branches for the time-varying magnetic field produced by alternating current, which reduces the eddy current in the PMs and enhances their stability. Electromagnetic coupling is used to analyze the operating principles and characteristics of HSFCL. Finite-element analysis simulations were performed using Maxwell and compared with verification experiments, proving that HSFCL is efficient in fault clipping and PM reliability enhancement.

A neodymium hybrid fault current limiter

This paper presents a new hybrid type fault current limiter topology for use in distribution systems. The proposed system includes a fast mechanical contact switch, a semiconductor switch, a neodymium magnetic core, and a metal-oxide varistor. A custom control algorithm is developed to detect the fault occurrence and perform the correct switching order of the proposed hybrid fault current limiter. A novel feature included in the proposed hybrid fault current limiter is the ability to control the fault current magnitude through the use of pulse-width modulation. In addition, the Jiles–Atherton method of hysteresis is used to model the nonlinear permeability of the NdFeB core. Simulations are performed using Power System Computer Aided Design (PSCAD) for both a high voltage and a low voltage system. A low voltage (20 V, 1.25 A) hardware system is built to verify the PSCAD simulations, and the results are presented. In conclusion, a comparison between the PSCAD simulations and the hardware experimental results verify the correct modeling of the proposed topology and confirm its feasibility. Copyright © 2014 John Wiley & Sons, Ltd.

Comparison of Four Different Types of Ferromagnetic Materials for Fault Current Limiter Applications

A comparison of neodymium, samarium-cobalt, aluminum-nickel-cobalt, and laminated steel is presented for use in fault current limiter applications. The ferromagnetic material properties are modeled using the Preisach method of hysteresis. The nonlinear inductance of each magnetic core is calculated and displayed. Only the material properties are changed during each consecutive simulation and are subjected to distribution system parameters to assess their fault current limitation applicability. Finite-element analysis is performed on the casing and coils of the mechanical design structure of the new hybrid fault current limiter. A new fault current limiter topology is presented and simulated in Piecewise Linear Electrical Circuit Simulation. The simulated results show the effect of different materials on the current limiter's performance. Conclusions are made that neodymium is the most suitable ferromagnetic material (of the materials tested) for fault current limiter applications.

Experimental Analysis of the Magnetic Flux Characteristics of Saturated Core Fault Current Limiters

A fault current limiter (FCL) is a device that is designed to reduce the impact of fault currents on electricity networks and increase the availability of such networks to consumers. One particular FCL technology that is currently attracting worldwide attention, from both researchers and commercial engineering companies, is the saturated core FCL. This device utilizes the change in permeability between the saturated and unsaturated states of a magnetic core to provide both low steady state losses and effective fault current limiting. Typically the core is saturated using an electromagnetic coil, which can be either superconducting or non-superconducting. Although there have been several studies on the electrical characteristics of this device, the transient magnetic behavior has been largely overlooked. In this paper the magnetic flux characteristics of saturated core FCLs are experimentally analyzed. The study includes the magnetic behavior during both the initial biasing of the cores and during transient fault conditions. The influence of FCL topology and alternative low-cost core materials, on the flux characteristics and overall device performance, is also discussed.

New saturable‐core fault current limiter topology with reduced core size

AbstractFault current limiters (FCLs) are expected to play an important role in protection of future power grids. By inserting a limiting impedance in series with a line, they limit the increasing levels of the fault currents to acceptable values. Inductive FCLs based on core‐saturation effect are particularly interesting due to their inherent reaction on a fault. However, some challenges are to be solved: too large amount of required material and induced over‐voltage across the DC winding that is used to drive the core into saturation. This paper introduces a new configuration of the inductive FCLs, where the amount of the required material is reduced considerably and the induced over‐voltage across the DC winding is decreased. The amount of magnetic material is reduced by employment of one core per‐phase instead of two. The middle leg of the three‐leg core is used as a shunt path for the AC flux. It enables a gap insertion in the AC magnetic circuit without influencing the DC magnetic circuit, i.e. the amount of DC winding material. Thus, a smaller core (less magnetic material) can be used for the same power level. Results obtained from the lab prototype match very well the one from simulations. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Fault Current Limiter Based on Resonant Circuit Controlled by Power Semiconductor Devices

This work presents a resonant fault current limiter (FCL) controlled by power semiconductor devices. Initially the operation of two ideal resonant circuit topologies as fault current limiter are discussed. The analysis of these circuits is used to derive an alternative topology to the fault current limiter based on the connection of a series and a parallel resonant circuit. Digital models are implemented in the SimPowerSystem/Matlab simulation package to investigate the performance of the proposed FCL to protect transmission and distribution electric networks against short circuit currents. Transfer functions of the linear limiter models are used to identify the effect of each element of the FCL over its stability and its transient response. The developed analysis will be used to derive modifications in the FCL topology in such a way to improve their dynamic response.