Current-limiting Performance Research Articles

A mixture of Si3N4 powder and SiO2 sand as a novel DC arc quenching medium for improvement of the current-limiting performance of a model electric fuse

A current-limiting and consequent direct current (DC) arc interruption requires an increase in arc resistance rarc for a DC fuse. Flattery silica (SiO2) sand has been used as an arc quenching medium in fuses for decades. However, there are few reports about a novel arc quenching medium which enables more rarc increases compared to flattery SiO2 sand. This paper uniquely selected a novel arc quenching medium based on the following material properties: (1) electrical resistivity and thermal conductivity in the solid phase, (2) the possibility of rarc increasing in the gas phase, (3) the possibility of electrical insulation after re-solidification, and (4) the cost of materials. As a result, we originally selected a powder mixture of silicon-nitride (Si3N4) and flattery SiO2 sand as a promising novel arc quenching medium. Therefore, DC interruption experiments were performed using a Si3N4/flattery SiO2 sand powder mixture under different Si3N4 concentration conditions. As a result of 1000 A DC arc quenching experiments, the utilization of Si3N4 powder with the flattery SiO2 sand successfully increased the arc resistance rarc during the arc quenching process. The increasing Si3N4 concentration exhibited a further increase in rarc during the arc quenching process. As a result of the rarc increase, the arc quenching time was significantly shortened to 30 ms for 30 wt.% Si3N4 conditions from 54 ms for the SiO2 sand conditions. In addition, utilization of Si3N4 powder achieved high insulation resistance over few MΩ after DC arc interruption. The above results clearly indicate that utilization of Si3N4 powder with flattery SiO2 sand can increase the DC interruption performance of the fuse.

Fluid-chemical modeling of the near-cathode sheath formation process in a high current broken in DC air circuit breaker

When the contacts of a medium-voltage DC air circuit breaker (DCCB) are separated, the energy distribution of the arc is determined by the formation process of the near-electrode sheath. Therefore, the voltage drop through the near-electrode sheath is an important means to build up the arc voltage, which directly determines the current-limiting performance of the DCCB. A numerical model to describe the near-electrode sheath formation process can provide insight into the physical mechanism of the arc formation, and thus provide a method for arc energy regulation. In this work, we establish a two-dimensional axisymmetric time-varying model of a medium-voltage DCCB arc when interrupted by high current based on a fluid-chemical model involving 16 kinds of species and 46 collision reactions. The transient distributions of electron number density, positive and negative ion number density, net space charge density, axial electric field, axial potential between electrodes, and near-cathode sheath are obtained from the numerical model. The computational results show that the electron density in the arc column increases, then decreases, and then stabilizes during the near-cathode sheath formation process, and the arc column’s diameter gradually becomes wider. The 11.14 V–12.33 V drops along the 17 μm space charge layer away from the cathode (65.5 kV/m–72.5 kV/m) when the current varies from 20 kA–80 kA. The homogeneous external magnetic field has little effect on the distribution of particles in the near-cathode sheath core, but the electron number density at the near-cathode sheath periphery can increase as the magnetic field increases and the homogeneous external magnetic field will lead to arc diffusion. The validity of the numerical model can be proven by comparison with the experiment.

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.

CardioToxCSM: A Web Server for Predicting Cardiotoxicity of Small Molecules.

The design of novel, safe, and effective drugs to treat human diseases is a challenging venture, with toxicity being one of the main sources of attrition at later stages of development. Failure due to toxicity incurs a significant increase in costs and time to market, with multiple drugs being withdrawn from the market due to their adverse effects. Cardiotoxicity, for instance, was responsible for the failure of drugs such as fenspiride, propoxyphene, and valdecoxib. While significant effort has been dedicated to mitigate this issue by developing computational approaches that aim to identify molecules likely to be toxic, including quantitative structure-activity relationship models and machine learning methods, current approaches present limited performance and interpretability. To overcome these, we propose a new web-based computational method, cardioToxCSM, which can predict six types of cardiac toxicity outcomes, including arrhythmia, cardiac failure, heart block, hERG toxicity, hypertension, and myocardial infarction, efficiently and accurately. cardioToxCSM was developed using the concept of graph-based signatures, molecular descriptors, toxicophore matchings, and molecular fingerprints, leveraging explainable machine learning, and was validated internally via different cross validation schemes and externally via low-redundancy blind sets. The models presented robust performances with areas under ROC curves of up to 0.898 on 5-fold cross-validation, consistent with metrics on blind tests. Additionally, our models provide interpretation of the predictions by identifying whether substructures that are commonly enriched in toxic compounds were present. We believe cardioToxCSM will provide valuable insight into the potential cardiotoxicity of small molecules early on drug screening efforts. The method is made freely available as a web server at https://biosig.lab.uq.edu.au/cardiotoxcsm.

Modeling the limiting performance of resistive superconductor fault current limiters for 2G HTS tape

Modeling the limiting performance of resistive superconductor fault current limiters for 2G HTS tape

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.

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.

Study on Sustainable Current-Limiting Capability of a Saturation-Based dc I-SFCL Prototype

If the inductive superconducting fault current limiter (I-SFCL) cannot maintain its current-limiting capacity before the dc fault is isolated, it will lead to a secondary fault in the dc system, and cause an impact on the system primary equipment. Therefore, the study of sustainable current-limiting capability is an important aspect in the dc SFCL researches. In this paper, the sustainable current-limiting capability of a saturation-based dc I-SFCL prototype was discussed in details. Through the dc current-limiting performance experiments, it is found that the sustainable current-limiting capability of this type of SFCL has a negative correlation with its reverse saturation degree, which can be affected by the design parameters. The influence factors of reverse saturation were first analyzed through the mathematical model of this prototype. Afterward, combined with the experiments, the sustainable current-limiting capability of the proposed dc I-SFCL is fully explored by changing the coil current and the number of turns, which offers a reference for parameter design of I-SFCL in the future engineering application.

Prototype Current-Limiting Hybrid DC Circuit Breaker Incorporating a Fuse and a Semiconductor Device

Owing to the increased demand for DC interruption, a prototype current-limiting hybrid DC circuit breaker incorporating a fuse and a semiconductor device was developed, based on a completely novel design concept. Recently, hybrid DC breakers have been attracting attention because of their low conduction loss and high-speed current interruption capability. The superiority of this hybrid DC circuit breaker lies in the simultaneous use of the high-speed current-limiting performance of the fuse and the highly reliable current-interruption performance of the semiconductor device. Furthermore, the hybrid DC circuit breaker performs the current interruption without any mechanical contact, thus preventing any delay in operation induced by the mechanical contact. The feasibility of the proposed concept was demonstrated by the successful application of the circuit breaker in a 1 kA fault current interruption procedure. Hence, the current-limiting hybrid DC circuit breaker is suitable for low voltage and medium voltage DC system protection. As the fuses and semiconductor modules progress, the hybrid DC circuit breaker may also adapt to HVDC systems.

Centralized Locating Strategy of Fault Current Limiters in MMC-Based Multiterminal HVdc Grid

In this article, a centralized locating strategy of fault current limiter (FCL) in high-voltage direct current (HVdc) grid is proposed and analyzed. By employing FCLs at the output sides of modular-multilevel-converters (MMCs), the proposed centralized locating strategy could reduce the number of FCLs in multiterminal high-voltage direct current (MTdc) grid. A typical application scenario based on Zhangbei–Beijing four-terminal HVdc grid is introduced in this article. Mathematical model of the proposed strategy is built and numerical solutions are calculated. Then, the simulation model is built in PSCAD/EMTDC and different locating strategies of FCL are studied. Simulation results verify the rationality of theoretical analysis. Also, calculation and simulation results demonstrate that the proposed centralized strategy has similar current-limiting performance with the conventional distributed FCL locating strategy. When the proposed strategy is applied, the MMCs could be protected from overcurrents. What is more, the reliability and reconnection of partial system after faults are ensured. The healthy part of MTdc grid could maintain continuous operation and transmit active power as normal. When applying different FCL locating strategies, the total investment of FCLs is calculated and compared. Calculation results prove that the proposed centralized locating strategy can effectively reduce the investment of FCLs compared with the conventional distributed strategy and is more suitable for MTdc grid.

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.

R-Q curve based evaluation method for current-limiting performance of DC R-SFCL in high voltage DC system

The current-limiting performance of the dc resistive-type superconducting fault current limiter (dc R-SFCL) is vital to the reliability in the high voltage dc current (HVDC) transmission system. It is expensive and difficult to utilize the discharging process of the precharged dc capacitor to evaluate the current-limiting performance. In this paper, a R-Q curve based evaluation method for current-limiting performance of dc R-SFCLs in dc system is proposed, which replaces the dc impulse experiment with ac impulse experiment. A ± 160kV dc SFCL prototype is designed by Guangdong Power Grid Co., Ltd., and tested to acquire the experimental heat accumulation Q and the experimental R-Q curve. Accordingly, the mathematical model consistent with the prototype is built in PSCAD. Finally, a fault condition is simulated in dc system to verify the feasibility of the R-Q curve based evaluation method. It is shown that the proposed method has superior properties in simplifying the testing platform, reducing the test requirements and costs, and providing reference for precise modeling of SFCLs.

Design and Test of 40-kV/2-kA DC Superconducting Fault Current Limiter

In this article, a general scheme of a 40-kV/2-kA resistive type dc superconducting fault current limiter (SFCL) is suggested, which could be utilized to suppress the surge current caused by short-circuit faults in voltage-source-converter HVdc (VSC-HVdc) power grids. This dc SFCL is designed and fabricated with 6 coil modules in parallel and 4 in series. In order to investigate the current-limiting performance of the dc SFCL under the rapidly rising fault current, the SFCL is tested on the platform with a pulsed dc impact generator. Besides the property of current limitation, the current capacity, insulation and quench recovery performance of such SFCL are also tested. Results indicate that the critical current of SFCL is larger than 2050 A at 69 K, and the dc withstand voltage is larger than 74 kV in 2 h. During the 9-kV dc impact test, the short-circuit current could be limited to 8842 A, and the quench recovery time is less than 200 ms.

Analysis of R-SFCL With Shunt Resistor in MMC-HVDC System Using Novel R-Q Method

The resistive superconducting fault current limiter (R-SFCL) is considered as a promising protection device to restrict the DC fault current in modular multilevel converter based high voltage direct current (MMC-HVDC) system. One bottleneck of R-SFCL is that it needs to withstand an overcurrent impact during fault, which results in temperature rise and may damage superconducting coils. A shunt resistor connected in parallel with R-SFCL can reduce temperature and protect superconducting coils. However, there are few studies to quantitatively analyze the influence of shunt resistor. This paper applies a novel R-Q method to calculate the quenching resistance of R-SFCL. By combining the R-Q method and finite element method, the system simulation and electromagnetic field analysis are separated, and the calculation feasibility is greatly improved. Then, the effect of shunt resistor in reducing the temperature of R-SFCL is studied. The influence of shunt resistance to the economic and current-limiting performance of R-SFCL is discussed.

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

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

Current-limiting characteristics of saturated iron-core fault current limiters in VSC-HVDC systems based on electromagnetic energy conversion mechanism

A common method to examine the current-limiting performance of saturated iron-core fault current limiter (SI-FCL) in high-voltage direct-current transmission based on voltage source converter (VSC-HVDC) systems is to solve differential equations based on the system fault transient characteristics and the equivalent inductance calculation equation. This method analyzes the fault current of the VSC-HVDC system in the time domain. However, it is computationally complex and cannot directly reflect the relationship between parameters and the current-limiting effect of the SI-FCL. In this paper, the relationship between the magnetic flux density and magnetic field energy of the SI-FCL is analyzed. The energy exchange between the DC capacitor and the SI-FCL in the DC short circuit fault process is analyzed. From the perspective of electromagnetic energy conversion, the criterion for determining the current-limiting ability of the SI-FCL in the transient process is given based on the parameters of the SI-FCL and VSC-HVDC system. On this basis, the characteristics of the DC side fault current and the capacitor voltage when the SI-FCL has current-limiting ability are examined. Based on the parameters of the SI-FCL and VSC-HVDC system, a method for calculating the fault current peak value and capacitor voltage drop time is given. Finally, the accuracy of the analysis of the SI-FCL in the VSC-HVDC system based on the electromagnetic energy conversion mechanism is demonstrated through a case study and simulation results of the VSC-HVDC system with different SI-FCLs.

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.

Design and Test of 10 kV/400 A Flux-Coupling-Type Superconducting Fault Current Limiting Module

The flux-coupling-type superconducting fault current limiter (FC-SFCL) is suggested to suppress the surge current in voltage sourced converter based HVdc (VSC-HVdc) power systems. One 10 kV/400 A FC-SFCL module with two branches is designed and tested. For the FC-SFCL module, the two branches could use the same or different YBCO tapes. Furthermore, the electromagnetic analysis and parameter calculation of the module are performed. In order to study the current-limiting performance of the FC-SFCL under the rapid change of fault current, a dynamic simulation model is established. Finally, the transient properties of FC-SFCL module are simulated and tested. According to the measurement results, the maximum impact current could be limited from 12 kA to 6264 A, and the largest resistance of the SFCL module is about 1.5 Ω when the dc impact voltage is 10 kV, which is close to the simulation results.

Resistance varying characteristics of DC superconducting fault current limiter in MTDC system

Recent years, voltage source converter-based multi-terminal high voltage DC power transmission (MTDC) is widely developed in the world. However, it is difficult for the existing DC breaker to cut off the fault transmission line with large short-circuit fault current. Then, it would be helpful to develop DC fault current limiter for the MTDC system. In this paper, DC superconducting fault current limiter (DCSFCL) is proposed to limit fault current. In order to study the resistance-time performance of the DCSFCL under the rapid change of fault current, a simulation model of Zhoushan MTDC system with DCSFCL is established, and the current-limiting performance of the DCSFCL at different location of the grid is studied. The simulation results show that DCSFCL can effectively limit short-circuit current and improve the operation reliability of MTDC system.

Technical Evaluation of Superconducting Fault Current Limiters Used in a Micro-Grid by Considering the Fault Characteristics of Distributed Generation, Energy Storage and Power Loads

Concerning the development of a micro-grid integrated with multiple intermittent renewable energy resources, one of the main issues is related to the improvement of its robustness against short-circuit faults. In a sense, the superconducting fault current limiter (SFCL) can be regarded as a feasible approach to enhance the transient performance of a micro-grid under fault conditions. In this paper, the fault transient analysis of a micro-grid, including distributed generation, energy storage and power loads, is conducted, and regarding the application of one or more flux-coupling-type SFCLs in the micro-grid, an integrated technical evaluation method considering current-limiting performance, bus voltage stability and device cost is proposed. In order to assess the performance of the SFCLs and verify the effectiveness of the evaluation method, different fault cases of a 10-kV micro-grid with photovoltaic (PV), wind generator and energy storage are simulated in the MATLAB software. The results show that, the efficient use of the SFCLs for the micro-grid can contribute to reducing the fault current, improving the voltage sags and suppressing the frequency fluctuations. Moreover, there will be a compromise design to fully take advantage of the SFCL parameters, and thus, the transient performance of the micro-grid can be guaranteed.