Fault Current Limiter Research Articles

Investigating Permanent Magnet Synchronous Generator Wind Turbine Performance During Low Voltage Using Series and Bridge Type Fault Current Limiters

Investigating Permanent Magnet Synchronous Generator Wind Turbine Performance During Low Voltage Using Series and Bridge Type Fault Current Limiters

Development of cryogenic insulation supporter module for a 220 kV 2G-tape-based resistive fault current limiter

Resistive type superconducting fault current limiter (R-SFCL) is one of the most promising candidates to suppress fault currents in power grids. However, the violently boiled cryogen liquids, commonly liquid nitrogen, occurred due to fault currents, poses a crucial cryogenic insulation challenge for R-SFCL. Here we report the design and development of a Cryogenic Insulation Supporter Module (CISM) for a 220 kV R-SFCL. First, we present the design and test of the prototype Cryogenic Insulations Supporter (CIS). The developed CIS passed the high voltage tests under operating conditions. Following on this, we then present the design of CISM, which consists of 14 CISs, with the length and outer diameter of 12 m and 2.5 m, respectively.

Protecting DFIG‐based multi‐machine power system under transient‐state by nonlinear adaptive backstepping controller‐based capacitive BFCL

The invention of doubly-fed induction generator (DFIG) brings the wind energy one step ahead as renewable power generation. But the performance of the grid-connected DFIGs are greatly affected by grid disturbances as their stator windings are interfaced to the grid directly. Different fault current limiters are capable of improving fault ride through capability during short circuit faults. Nonlinear controller based fault current limiters (FCLs) are superior to deal with the nonlinearity of the power systems. This paper proposes a nonlinear adaptive backstepping controller (ABSC) based capacitive bridge-type FCL (CBFCL) to enhance the fault ride through capability of a DFIG-based wind farm connected to a multi-machine power system. At first, a complete modelling of the CBFCL is derived to understand its behaviour during the normal and fault period more accurately. Then, the ABSC is designed based on that dynamic model, along with the backstepping controller (BSC) and sliding mode controller (SMC) for comparison purpose. Finally, the performance of the ABSC to control the CBFCL has been analysed and verified by comparing with that of the BSC and the sliding mode controller. All the graphical and mathematical analyses favour the ABSC based CBFCL under symmetrical and asymmetrical fault (both temporary and permanent) scenarios.

Integration of superconducting fault current limiter with solid-state DC circuit breaker

The onboard direct current (DC) system in electric aircraft could face a severe fault current, which is tens of times the nominal current in a short-circuit fault. It is critical to limit the fault current and clear the fault within a few milliseconds to prevent any damage to the DC system. A protection method using a resistive superconducting fault current limiter (SFCL) with a solid-state DC circuit breaker (SSCB) to manage the DC short-circuit fault is proposed and experimentally verified. A bifilar SFCL coil prototype with two types of connection to achieve low and high inductance is designed and tested, which reduces the fault current considerably from 2000 A to below 1000 A. The performance when integrating the low and high inductance SFCL with a solid-state DC circuit breaker are investigated. It is found that when integrating the SFCL with the SSCB, a high voltage is induced across the high inductance SFCL during current interruption tests. In terms of reliability and durability, the low inductance SFCL is preferred to integrate with the SSCB. The experimental results show that the low inductance SFCL can be an effective solution to protect the DC system from severe fault currents and then SSCB can rapidly and reliably interrupt the fault current at 1000 A.© 2017 Elsevier Inc. All rights reserved.

Improved Recovery Time and Voltage Stability for Resistive Superconductor Fault Current Limiters

Fault current levels occurring in power systems force the breaking capacities of the breakers. In the power system elements, the generator, transformer, cables, etc., are exposed to the dangerous effects of fault current until the breaker clears the fault. Various limiting methods have been developed to eliminate this adverse situation in recent years. One of these methods is Superconducting Fault Current Limiters (SFCL). With the discovery of High-Temperature Superconductors (HTS), SFCL's Resistive type has become more popular. Resistive SFCL (R-SFCL), based on the non-linear resistance property of superconducting materials, limits the fault within the first half period. However, it cannot provide such a fast response after the fault. The time required to regain the superconducting state after the fault is the recovery time. For R-SFCL manufacturers, recovery time is a design parameter that must be kept short. This study examines limiting performance, recovery time, and voltage stability with the dynamic model created using MATLAB/Simulink. With the shunt breaker method proposed in the study, the recovery time was shortened, and the voltage stability improved.

Forces and Stresses in the Windings of a Superconducting Fault Current Limiter

This paper presents the design of a Superconducting Fault Current Limiter (SFCL) and calculation results of forces and stresses in the windings of a resistive fault current limiter. The design of the fault current limiter consists of two parallelly connected and magnetically coupled windings, cooled by a single stage cryocooler. Magnetically compensated windings made of HTS tape give a very low voltage on the limiter at a nominal current. Limitation of the short-circuit time and the value of the maximum initial fault current reduces the thermal and dynamic effects of the passage of a fault current. Using devices which limit the value of a fault current can lower the level of required short-circuit capacity of the elements in a system. However, selected means of fault currents limitation must maintain the power quality standards. A perfect fault current limiter is required to have substantial impedance in fault conditions and zero impedance at work currents. Such requirements are met by a SFCL. An increase of current caused by the occurrence of a fault current results in the transition of the superconducting material from the superconducting state into the resistive state. This increases the impedance of short-circuit loop, allowing the fault current value to decrease. During a short-circuit, the forces generated from the short-circuit current also act on the limiter windings. Short-circuit current causes stresses in the superconducting tape. Exceeding the permissible stress value results in an irreversible reduction in the critical current of the superconducting tape. Calculations of the forces and stresses in the HTS tape for the maximum value of the short-circuit current were carried out using the finite element method. The constructed limiter was tested and the winding design ensures that the tape stresses are at a safe level even for short-circuit currents.

A review of superconducting fault current limiters compared with other proven technologies

• Fault Current Limiters Technologies. • Advantages and disadvantages of FCL technologies. • Commercial FCL Devices review. Several substations in operation were commissioned decades ago. These substations are overstressed, then their protection equipment cannot provide an effective safety condition to the system. In the worst cases, short-circuits can cause permanent damage to the system if the overcurrent is higher than the capacity of the installed equipment. There are some possible solutions for those cases: replace all the equipment in the overstressed substation, build a new one in parallel or install a fault current limiter (FCL) device. From an economic point of view, introducing FCLs in the power system is the best way to solve the described problem. The commercial solutions available are the pyrotechnic FCL, air coil reactor, neutral earthing resistor, and high impedance transformer. However, these devices are limited and present several drawbacks. Since the ’70s, there has been a search for reliable FCL devices that do not interfere in the regular operation of substations and could limit the fault currents to the protection system rated level. There were so many FCL technologies proposed in the last decades. These proposed new devices may use superconducting technologies, power electronics, or both. This paper reviews proven FCL technologies, focusing on full-scale devices demonstrated in field and lab tests. The goal is to introduce the main FCL technologies in development and discuss didactically their operation principle, the built prototypes, the commercial units, whether they exist, and the main drawbacks for each technology presented. A final analysis of the level of maturity for each FCL technology is discussed using the TRL (Technology readiness level) scale in order to find technologies with more potential for mass production. The three technologies closer to the full commercial application are: the Resistive Superconducting FCL, the Saturated Iron Core FCL, and the Series Reactor FCL.

Analysis on Three-Phase Ground Fault Current Limiting Operations of Three-Phase Transformer Type SFCL Using Two Superconducting Modules

Three-phase transformer type superconducting fault current limiter (SFCL) using two superconducting modules (SCMs) between secondary windings, which consisted of three-phase transformer windings wound on three legs of E-I iron core, one SCM with insulated connection with one secondary winding and another SCM with non-insulated connection between other two secondary windings, were suggested. For the suggested three-phase SFCL using two SCMs, its three-phase ground fault current limiting operations were analyzed through phasor diagram from electrical equivalent circuit. To verify three-phase ground fault current limiting operation of three-phase transformer type SFCL using two SCMs between secondary windings, three-phase ground faults were applied into three-phase power simulated system with the suggested SFCL. Through analysis on the test results, three-phase transformer type SFCL using two SCMs between secondary windings was confirmed to have effective three-phase ground fault current limiting operations through quenches of two SCMs.

Resistive SFCL Integrated Ultrafast DC Hybrid Circuit Breaker for Subsea HVDC Transmission Systems

High voltage direct current (HVdc) power transmission systems do not encounter any natural zero crossing unlike the ac systems, and hence, the dc circuit breakers employed should be fast-acting and reliable to ensure safe operation. Circuit breakers (CBs) that have fast response time with lower energy loss dissipation are required for subsea HVdc transmission systems. This article investigates the performance of various CB topologies, including ultrafast coupled inductor hybrid CB (CIHCB) topology without and with the integration of resistive-type superconducting fault current limiter (R-SFCL) for a 100-kV, 100-MW HVdc transmission systems. It is found that the addition of R-SFCL with 1.7-ms response time decreases the peak current through the breaker and, hence, the power dissipated in the CB during short-circuit fault conditions. Thus, the rating of CB can be significantly decreased with the proposed topology. Furthermore, a comparison of power loss in CIHCB with the existing topologies, such as mechanical CB, resonant CB, and HVdc-hybrid CB, are also presented in this article.

Surface Dielectric Characteristics of GFRP and PTFE in Cryogenic Environment Under the Switching Impulse Superimposed on DC Voltage

For insulation materials utilized in DC superconducting fault current limiter, surface discharge along the interface is more damaging to the insulation relative to penetration breakdown. Therefore, for the reliable and economical insulation design of DC superconducting fault current limiter, it is very important to investigate an insulation materials and study the surface dielectric characteristics. Additionally, DC superimposed switching impulse can cause critical stress to the insulation of DC superconducting fault current limiter and can potentially result in breakdown. Therefore, the insulation materials of DC superconducting fault current limiter must have sufficient surface distance to prevent surface discharge under DC superimposed switching impulse. In this paper, the surface breakdown tests were performed by applying DC superimposed switching impulse to glass fiber reinforced polymer (GFRP) and polytetrafluoroethylene (PTFE) specimen in cryogenic environment. Surface dielectric characteristics according to positive and negative polarities of DC and switching impulse were analyzed. In addition, the surface dielectric characteristics were analyzed by selecting the gap distance. From the experimental results, the surface dielectric strength of GFRP was higher than that of PTFE, but the difference in surface dielectric strength between GFRP and PTFE decreased as the gap distance increased. The surface breakdown voltage of PTFE was lowest at the superposition of positive DC and positive switching impulse. However, GFRP has the lowest surface breakdown voltage when negative DC superimposed positive switching impulse. Consequently, it is possible to design the optimal surface distance of solid insulation materials in DC superconducting current limiter by considering the superposition of DC and switching impulse polarity.

Comparison of Initial Current Limiting Performance of Two Inductive Superconducting Fault Current Limiters With Different Electrical Coupling Between Cores and Coils

It is possible to improve the performance of the superconducting fault current limiters and to apply power system as a method for reducing the volume and weight of the superconducting fault current limiters using iron core and coil. This study thus manufactured a superconducting current limiting element using a coated conductor with high specific resistance, and applied it to two models with an iron core and coil (a model consisting of three separated iron cores and coils and a model integrating three coils through one iron core) for the comparison and analysis of the current limiting characteristics. Of the two aforementioned models, the separate-iron-core/coil model with additive polarity wiring offered a higher current limiting rate, but under each wiring condition (subtractive polarity and additive polarity wirings), the two models' current limiting rates were found not to be very different. The superconducting current limiting element's thermal strain was determined to be smaller in the integrated model than in the separate-iron-core/coil model, but the integrated model created quench resistance of the superconducting current limiting element at the sound phase (S phase), suggesting that the result increased the critical current of the superconducting current limiting element. Further studies should be done, however, through the structural change of the integrated model.

A Fault Detection Scheme in MTDC Systems Using a Superconducting Fault Current Limiter

This article proposes a fault detection scheme for modular multilevel converter-based multiterminal dc (MMC-MTdc) girds based upon a resistive-type superconducting fault current limiter (RSFCL). By analyzing the characteristics of the currents through the faulted and healthy lines in an MMC-MTdc system, the theoretical foundations of the scheme are established. This yields a fault detection scheme with fault identification, fault pole discrimination, and high-resistance tolerance abilities. Extensive simulations confirm that the proposed detection scheme can identify the metallic short circuit fault within 1 ms, with the ability to promptly detect faults with high resistance in less than 3 ms taking the communication delay into consideration. This method does not cause any mal-operation of dc circuit breakers as a result of faults on adjacent lines and power order changes. The proposed scheme has immunity to noise and provides full-length protection of the protected transmission line. Simulation results show significant suppression of both the amplitude and the rate-of-rise of the fault current during the fault detection process, which enhance the reliability and stability of the protected grid.

A Robust Protection Scheme for Multimicrogrids Using Fault Current Limiter

The operation of multimicrogrids (MMGs) can cause significant impact on power system network, especially changes in level and direction of fault current. The fault current level may exceed rating of existing directional overcurrent relays (DOCRs) that lead to sympathetic tripping or fail to trip DOCRs in the network. It is expensive and extremely challenging to upgrade or replace the existing DOCRs in the network. If not properly addressed, this issue may hinder the deployment of MMGs in to the network. Hence, this article proposes a robust protection scheme for DOCRs coordination in MMGs without replacing existing DOCRs in network. First, the proposed scheme calculates optimal settings of DOCRs in all stand-alone microgrids of MMG during islanded mode. Then, optimal values of fault current limiters are obtained using calculated optimal settings. The main advantage of proposed scheme is that it provides one set of DOCRs settings valid for all operating modes of MMG. In this work, the DOCRs coordination problem is formulated as nonlinear problem and solved using proposed hybrid approach symbiotic organisms search (SOS) and nonlinear programming (NLP). The initial solution is determined by SOS and final solution is obtained using NLP. Further, the proposed scheme is examined during gird connected and islanded modes in two different configurations (series and parallel) of MMG, which are not stated in previous literature. Finally, simulation results are validated using numerical relay and real time digital simulator, which are interfaced through voltage and current amplifier to execute hardware-in-loop test bed.

Parameter Matching and Structural Optimization Design of H-SFCL in MMC Ship MVDC System

As a high-density and high-load system, ship DC system has the characteristics of short power supply line, low system damping. When a short-circuit fault occurs, it will cause serious damage and the direct current circuit breaker (DCCB) is required to cut off the fault current quickly. In our previous paper, a hybrid-type superconducting fault current limiter (H-SFCL) has been proposed, which can help DCCB reliably remove faults and realize fast reclosing. On this basis, the H-SFCL is selected and applied in ship medium voltage direct current (MVDC) system. In this paper, not only the current limiting principle of H-SFCL is introduced, but also its current limiting characteristics in modular multilevel converter (MMC) ship MVDC system are simulated and analyzed. In addition, the paraments selection and coil structural design of H-SFCL are optimized to improve the economy and ensure the safety and stability of the coil. Firstly, the parameter matching method is proposed based on the optimization algorithm in Matlab, and then the electromagnetic force coupling model in COMSOL is built to complete the structural optimization of the superconducting coil. The effectiveness of the optimization results is verified by stress analysis.

Fast Quench Detection in SFCL Pancake Using Optical Fibre Sensing and Machine Learning

A fast hotspot detection technique has been implemented and patented at École Polytechnique Fédérale de Lausanne (EPFL) under the European Union project FastGrid. The optical fibre sensing based technique uses the Mach-Zehnder Interferometer (MZI) and can detect even singular hotspots in the superconductor within 15ms. The MZI setup is very sensitive to external perturbations and mechanical stresses, which can manifest in the output along with the response to hotspots. The disturbance the setup is subject to, varies with the sample being tested and the environment it is being tested in. For example, the sample length and configuration, in addition to the routing of the optical fibre can determine the extent of the stresses on the optical fibre. Previous publications, showcased experiment results on relatively simple sample configurations which were straight HTS tapes with short lengths (0.3m or 1m). This manuscript will investigate the technique feasibility for a more complicated sample type: a pancake prototype for a superconducting fault current limiter (SFCL), comprising 12m of HTS tape in a bifilar winding, with taped optical fibre along the length of the conductor. The manuscript will also give a brief overview of a machine learning based post processing technique for the experimental data, developed at EPFL to supplement the MZI based quench detection for easy and reliable quench detection in large scale applications.

A New Method to Enhance the Low Voltage Ride Through Capability of Doubly Fed Induction Generator Using Resistive Type Superconducting Fault Current Limiter

A New Method to Enhance the Low Voltage Ride Through Capability of Doubly Fed Induction Generator Using Resistive Type Superconducting Fault Current Limiter

Electromagnetic Design and Performance Analysis of a Hybrid-Type Superconducting Fault Current Limiter in Shipboard MVDC IPS

As medium voltage dc-based (MVDC) technology is widely considered in the shipboard power system (SPS), the short fault protection of shipboard IPS is urgent. Superconducting fault current limiter (SFCL) is an efficient way to solve the short fault problems in shipboard MVDC IPS. A hybrid type SFCL (H-SFCL) based on a non-quenching inductor and two resistors is electromagnetic designed in this study. The H-SFCL can limit short fault current with no quenching and little heating. In this study, the short fault mechanism and mathematical model of MVDC SPS bipolar short fault is analyzed. According to current limiting performance requirements in MVDC SPS, components parameters of H-SFCL are optimized matching. The scheme of annular structure inductors is proposed and electromagnetic design of a 10 kV/6 kA H-SFCL is completed based on a genetic algorithm. The ac loss and thermal stress of the designed magnet are evaluated. The simulation results show that the H-SFCL with optimized electromagnetic parameters meets the design requirements.

Limitation Analysis of 1st and 2nd Generation Superconductors used in Resistive Superconductor Fault Current Limiters

Fault currents in power systems force valuable power system elements thermally, dynamically, and electromagnetically until the arc disappears. Installation elements that can withstand fault currents or damage existing components require a high cost. Installing components that withstand fault currents and the damage of fault currents to existing components are costly. Resistive Superconducting Fault Current Limiter (R-SFCL), one of the modern limiting methods, increases the safety and sustainability of the system by eliminating these risks. In this study, a dynamic model was created in MATLAB/Simulink for 1G and 2G HTS used in R-SFCL, and their response to single phase-to-ground fault was observed. According to the simulation results, the most advantageous HTS type for R-SFCL was determined. The fault current level, limitation rate, resistance and temperature values, and response times were compared in terms of limiting performance.

R-SFCL and RRCOCS-TVC Based Cooperative Control for Enhancing LVRT Capability of DFIG System

For the extraction of wind energy through a doubly-fed induction generator (DFIG), low voltage ride through (LVRT) is an essential technical requirement specified by the transmission system operator (TSO). Under a grid fault condition, DFIG should remain in connection with the grid for a certain minimum period and offer reactive power support as required by the TSO. A cooperative control scheme consisting of hardware solution through a superconducting resistance type fault current limiter (R-SFCL) and software solution constructed on the rotor reference current orientation control strategy (RRCOCS) with transient voltage control (TVC), is proposed in this paper to address the LVRT requirement. In the proposed control strategy, RRCOCS will limit the rotor current directly during a fault condition. The reactive power needs to be generated during fault to maintain grid code which is achieved through TVC. At the same time, improvement of stator terminal voltage, as well as suppression of stator current, is achieved by R-SFCL. The suppression of stator current by R-SFCL is also transformed to the rotor side aiding the rotor current limiting. The proposed cooperative scheme’s performance is simulated and tested on a 9 MW grid-connected DFIG wind system. The results obtained by the proposed strategy are compared with RRCOCS and RRCOCS-TVC.
 HIGHLIGHTS
 
 Independent software and hardware LVRT methods fail under severe faults and strict grid codes
 Software methods are challenged by current suppression and voltage support limits while the hardware methods involve high costs and undergo high thermal stress
 A cooperative LVRT can overcome the challenges and limitations associated with these independently deployed methods. The proposed R-SFCL device, in cooperation with RRCOCS-TVC, successfully meets the grid codes, and the transient behavior of the system's electrical and mechanical variables gets improved
 The proposed scheme helps reduce R-SFCL resistance, reduces its thermal stress, brings cost reduction in R-SFCL design, and improves its recovery characteristics. The listed improvement in R-SFCL can prevent the system from overcompensation and the adverse effects of recurring faults
 
 GRAPHICAL ABSTRACT

A coordinated relay protection strategy of distribution network based on fault current limiting

In order to solve the problem of difficult coordination of traditional overcurrent relay protection caused by short supply radius and little difference of fault current along urban distribution network, a coordinated relay protection strategy based on economical fault current limiter (FCL) is proposed. The FCL device is configured at the export of the main transformer, by using quick fault identification method, setting different protection current value and relay protection delay time, once the fault occurs, the FCL can quickly limit the fault current first then cooperate with the circuit break and switches on the feeder line to achieved the coordinated relay protection. Combining with faults occurring at different locations along the feeder line, the composition and basic working principle of the FCL are discussed, the theory of fast fault identification method and the setting method of the coordinated relay protection parameters are emphatically discussed. The simulation results show that the proposed current limiting coordinated relay protection strategy can effectively reduce the short-circuit current level and bus voltage drop during the fault handle processing, thus reduce the damage to the distribution system and influence range of the fault, greatly improve the selectivity of the relay protection finally.