Resistive Fault Current Limiter Research Articles

A novel current-limiting method for MMC-HVDC by coordinating virtual impedance control and fault current limiter

The modular multilevel converter (MMC) topology is very suitable for high voltage direct current (HVDC) system to achieve feasible power control, favorable black start capability as well as long-distance power transmission. This paper proposes a novel current-limiting method based on the coordination of virtual impedance control (VIC) and resistive fault current limiter (R-FCL) for MMC-HVDC, and it aims to effectively decrease the DC fault current level and assist the DC circuit breaker (DCCB) to remove the fault reliably and smoothly. Firstly, the MMC-HVDC’s topology and control strategy are expounded, and the modeling method of the VIC and the R-FCL is presented. According to the DC fault evolution, the time sequence coordination scheme of the VIC and the R-FCL for the MMC-HVDC is put forward. Then, considering the introduction of the proposed current-limiting method, the fault characteristics of the MMC-HVDC are theoretically deduced, and the capacity design of the VIC and the R-FCL is conducted. Using MATLAB, a typical ±320 kV MMC-HVDC system with VIC, R-FCL, and DCCB is built, and comparative simulations are performed. The results indicate the proposed approach can strongly limit the DC fault current within the acceptable range, and reduce the electrical stress and thermal stress in the MMC and DCCB. The proposed approach possesses better techno-economics than the R-FCL alone to solve the DC fault problem, and a more efficient protection of the MMC-HVDC is realized.

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.

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.

Lamination process of second generation high temperature superconducting tape at Shanghai Superconductor Technology

As the second generation high temperature superconducting (HTS) tape enters the stage of commercialization and mass production, it has been successfully applied in several power and magnet devices. Different application scenarios also put forward different requirements for the electrical and mechanical properties of the HTS tape. This paper focuses on introducing the post-processing treatments of HTS tape, primarily copper plating and lamination. By preparing typical samples, the properties of copper-plated tapes and laminated tapes have been experimentally compared. The results show that under the condition of sufficient liquid nitrogen flow, the steady-state over-current tolerance of copper-laminated tape is significantly better than that of stainless steel-laminated and copper-plated tapes. At the same room temperature resistance, the over-current impact tolerance of stainless steel-laminated tape is 2–3 times that of copper-plated tape; the maximum transient current beared by the tapes reached 3896 A when they were put under shock for 8 ms, which has significant advantages in the application of resistive fault current limiter. At 77 K, yield strength Rp0.2 of the three types of superconducting tapes are > 1100 MPa for stainless steel-laminated tape, 645–1037 MPa for copper-plated tape and < 500 MPa for copper-laminated tape. The critical tensile stress of stainless steel laminated-tape is higher than that of copper-plated tape and copper-laminated tape. The tape reinforced structure described in this paper can provide a helpful reference for future design and manufacture of superconducting applications in power and magnet industries.

Progress on Second-Generation High-Temperature Superconductor Tape Targeting Resistive Fault Current Limiter Application

The resistive superconducting fault current limiter is well known for its simple structure and outstanding current-limiting effect, and it is broadly applied in power grid systems. The second-generation high-temperature superconductor (HTS) tape, of higher structural strength and greater room-temperature resistance, is well suited for application in resistive superconducting fault current limiters. The quenching caused by overcurrent in the HTS tape is a complexed coupling effect of several physical factors. The tape structure and properties directly impact the ultimate HTS tape’s quench performance. In this study, various SS316-laminated HTS tapes, of different critical currents, room-temperature resistances, and masses, were prepared. The pulse impact parameters of the various tape samples were measured using the RLC high-current impact test platform. By analyzing the resultant data, a quantitative assessment methodology to measure a tape’s tolerance toward impact was developed. The dependence of the HTS tape’s tolerance toward impact on its critical current, room-temperature resistance, and mass was studied. This provides numerical guidance on HTS material selection for resistive superconducting fault current limiters.

Superconductors for power applications: an executable and web application to learn about resistive fault current limiters

High-temperature superconductors (HTS) can be superconducting in liquid nitrogen (77 K) at atmospheric pressure, which holds immense promises for our future such as nuclear fusion, compact medical devices and efficient power applications. In a power system, high short-circuit currents can exceed the operational current by more than ten times, putting many parts of the system at risk. Superconducting fault current limiters (SFCLs) can limit the prospective fault current without disconnecting the power system, and are thus becoming increasingly attractive for future grids. With a growing interest in modeling and commercializing SFCL, the question of how to teach and to explain their operation to students has arisen. In order to help students visualize the potential use and benefits of an SFCL, we created an executable and a web application using COMSOL Multiphysics. This executable allows students to investigate the electro-thermal response of a resistive SFCL. The executable solves a 1D electro-thermal model of the SFCL under AC fault conditions, evaluating important figures of merit such as the limited current, the prospective current and the maximum temperature reached within the tape. Finally, the geometrical parameters as well as the superconducting properties of the device can be modified. The importance of the amount of silver stabilizer necessary to protect the device from over-heating occurring during a fault current can be investigated. In addition, the effects of having a sharp nonlinear transition from the superconducting to the normal state (intrinsic property of the superconductor) to obtain a current limitation can be explored. The executable allows the users to learn about the benefits of superconductors in real-life applications, without the prerequisite of extensive modeling or experimental setup. The executable can be downloaded from the HTS modeling website and run on the most commonly used operating systems.

SSR Alleviation in SCIG-Based Wind Power Plants Using Resistive Bridge-Type FCL

Series-Compensated Transmission Lines (SCTLs) are widely used for connection of large scale wind power plants (WPPs) to the power system to transmit the active power generated from WPPs. However, it can lead to sub synchronous resonance (SSR) phenomena in WPPs connected with SCTLs. Also, capacitive compensation of transmission lines reduces the line impedance, which leads to increasing short circuit current level in WPPs. This study proposes the resistive bridge-type fault current limiter (RBFCL) for SSR mitigation and limiting short circuit current in WPPs connected with SCTLs. Also, its performance is compared with the static synchronous compensator (STATCOM) and thyristor controlled series capacitor (TCSC) to demonstrate the effectiveness of the RBFCL in terms of SSR mitigation. The WPP used in this paper is modelled based on an aggregated squirrel-cage induction generator (SCIG) derived by an aggregated wind turbine (WT). The PSCAD/EMTDC software and the IEEE first benchmark model are used for this study. Simulation results demonstrate that the RBFCL not only limits the short circuit current contribution of WPPs, but also effectively damps the SSR oscillations due to IGE as well as TI, when the WPP is subjected to a large disturbance.

Current density distribution in resistive fault current limiters and its effect on device stability

The increase of current uniformity along of a Resistive type Superconductor Fault Current Limiter (R-SFCL) in the design of this type of limiters is well perceived as an important issue. The non-uniform distribution of current in R-SFCL only increases the current in some superconducting regions, as a result, in the fault conditions, only certain parts of the superconductor undergo a phase change that increases the heat pressure in those areas and causes the breakdown and destruction of the device. In this paper, the current density distributions in common patterns used in R-SFCs constructions have been simulated and investigated. To this end, an effective model is proposed for R-SFCL to achieve the highest uniformity of current and harmonic phase change over superconductors compared to other patterns. The simulation results in the Ansys Maxwell Software advocate the appropriate and satisfying performance of the proposed model.

Research on the Vacuum Arc Commutating Characteristic of Resistive Fault Current Limiters

The paper focuses on the vacuum arc commutating characteristic which is a common basic problem in resistive fault current limiters. The current commutating characteristic of the current can be diverted into the current limiting resistor from the vacuum circuit breaker is mainly researched. The influence of the current amplitude, the current limiting resistor resistance, the arcing time, the transverse magnetic field and the current frequency on the time of the current commutation and the current in the moment of the completion transition is investigated and analyzed. According to the experimental results, the mathematical description of the vacuum arc commutating characteristic is obtained. The interaction between the vacuum arc and the transverse magnetic field is discussed. The paper provides the foundation for the structure and parameters optimization of the resistive fault current limiter.

Analysis of thermo-physical properties of materials suitable for thermal stabilization of superconducting tapes for high-voltage superconducting fault current limiters

High-temperature superconducting coated conductors (CC) are attractive materials for high-voltage resistive fault current limiters. Commercially produced CC tapes cannot withstand electric fields over 100 V m−1, and therefore, they have to be modified by addition of thermal stabilization layer. We investigated several composite systems suitable for such thermal stabilization. As a matrix of composites, Stycast resins were used, which contain various contents of powder particles from SiC, SiO2, PbTiO3, ZrW2O8, or synthetic diamond. The thermo-physical properties such as thermal expansion, heat capacity, thermal diffusivity and direct-current electrical conductivity were measured because they are influenced by filler content in the composite. The possible highest amount of the powder can slightly increase the thermal conductivity and decrease the thermal expansion of the system to an acceptable value needed for the coating of CCs. A side effect is simultaneous drop of heat capacity; however, its value stays still high enough for the purpose of heat sinking. Overall, the best results were achieved in system with 20 vol% of SiC filler in Stycast 2850FT + Catalyst 23LV resin matrix. There the contribution of the semiconducting SiC addition to the electrical conductivity of composite was negligible.

Improvement of operation of power transformer protection system during sympathetic inrush current phenomena using fault current limiter

Power transformer protection has a high sensitivity due to its important role in power systems. Various factors such as inrush and sympathetic inrush currents may result in the inappropriate performance of protective relays and cause problems such as power outage or blocking of sensitive loads. Until now, several studies have been performed on the detection and reduction of inrush current, however, the effect of sympathetic inrush current on transformer protection has not been addressed. In this study, the operation of the protection system during the sympathetic inrush current is comprehensively analysed. Furthermore, the use of a fault current limiter is proposed to reduce the undesirable effects of the phenomena. The effects of the limiter on the saturation of power and current transformers are investigated. A real transmission station is simulated using DIgSILENT Power Factory Software to perform these studies by considering the resistive and impedance fault current limiter. Results show that protective relays do not have an improper operation during the phenomena with limiters. Moreover, with the resistive fault current limiter, sympathetic inrush and inrush currents are decreased by 5 and 15% more than the impedance fault current limiter, respectively. Saturation of power and current transformers is significantly reduced with limiters, especially with a resistive fault current limiter.

High-Voltage Superconducting Fault Current Limiters Based on High-Diffusivity Dielectric Substrates

High-temperature superconducting (HTS) tapes currently used for the manufacture of resistive fault current limiters use metallic substrates upon which the HTS film is grown. Because the alloys used for these substrates, such as Hastelloy, have a rather high resistivity and low thermal conductivity, the HTS film must be protected by a more conducting metallic layer acting as a shunt to avoid burn out during a fault. This shunt layer limits severely the electric field generated during the fault to values smaller than 100 V/m. A long length of tape is then necessary to achieve the desired high voltage. We show here that by using a high thermal diffusivity dielectric substrate such as sapphire, it is possible to obtain much higher electric fields of up to several kilovolts per meter.

New Technique for Using SMES to Limit Fault Currents in Wind Farm Power Systems

This paper introduces a new scheme, which uses a multifunctional superconducting device that can be used as an energy storage and as a fault current limiter. It is denoted as a superconducting magnetic energy storage - fault current limiter (SMES-FCL) and is modeled as a number of pancakes. It is connected to a wind turbine power system via tertiary transformer and power converters. A complete control scheme is built to achieve effective power transfer between the superconducting coil and the power system during normal operation to smooth the wind turbine output power. The fault current limiting function is implemented using a new technique that inserts a few pancakes from the whole SMES coil into the main electrical system during the fault and isolates the remaining pancakes. The number of pancakes used to limit the fault is quenched and operates as a resistive fault current limiter. The whole system including the wind turbine, the SMES-FCL model, and the interface circuit are implemented using PSCAD/EMTDC computer package. Also, the control scheme of SMES-FCL is built based on a feedback current signal to enable its operation into the two modes.

Improvement of Recovery Characteristics of REBCO Tape With Several Surface Conditions for Resistive Fault Current Limiter

Superconducting fault current limiters (SFCLs) are required to return to the superconducting state within the proper time (recovery time) after limiting a fault current according to a relay operation scheme in a power system. In order to apply SFCLs to power systems, the recovery time is important property and deeply depends on the heat transfer property of the heated surface of the superconducting tape (normal conducting state) to liquid nitrogen. It has been confirmed that REBCO tapes with various shaped fins or PTFE coating improved cooling property. In this paper, to clear the mechanism of cooling property improvement of fins or PTFE coating, boiling phenomena on REBCO tapes with some types of fins or PTFE coating was observed by use of a high-speed video camera. The influence on the cooling improvement property of cooling fins and PTFE coating was discussed according to the photographical view of the boiling phenomenon.

RETRACTED: Transient stability improvement analysis in a grid-connected doubly fed induction generator–based wind generator

In this article, transient stability enhancement analysis of the doubly fed induction generator–based variable speed wind generator is performed among the most promising series compensating devices like the diode-bridge-type non-superconductor fault current limiter, bridge-type fault current limiter, series dynamic braking resistor, resistive solid-state fault current limiter, and DC resistive superconducting fault current limiter. Although all series technologies are well documented in literatures, so far no comparison among them is reported. Therefore, to fill this gap, this article provides a detailed analytical analysis, and comparison is done the among the series compensators in terms of transient stability performances, implementation feasibility, control structure, and cost. A temporary balanced and unbalanced fault was applied in the doubly fed induction generator–based test system model to demonstrate the transient stability performance among the series compensating devices. In this work, extensi...

Insulation effect on thermal stability of Coated Conductors wires in liquid nitrogen

Superconducting wires are not perfectly homogeneous in term of critical current as well as stabilization. In resistive fault current limiter applications this could lead to hot spots if the fault current is only slightly above the nominal current of the device. Increasing stabilization by using thicker silver coating for example may prevent this problem but this method implies longer wire length to maintain the same impedance during a fault. Very efficient cooling in another way to prevent hot spots, this can be achieved in nucleate boiling regime. Optimal insulation can be used to prevent film boiling regime, staying in nucleate boiling regime in a much broader temperature range. In this work a novel technique is used to monitor in real time the temperature of the wire during the quench. Using this method several increasing insulation thicknesses are tested, measuring for each the heat exchange rate to the nitrogen bath. Exchange rate measurements are made in quasistatic regime and during the re-cooling of the wire. SuperOx wires provided with different insulation thicknesses exhibit an excellent stability, far above a bare wire. On the other side, for very thick insulations the stability gain is lost. Re-cooling speeds dependency on insulation thicknesses is measured too.

Finite Element Method simulation study of heat propagation in a novel YBCO-based Coated Conductor for resistive fault current limiters

YBCO-based Coated Conductors (CCs) used for applications in Resistive Superconducting Fault Current Limiters (RSFCLs) are well known to have fairly low values of Normal Zone Propagation Velocity (NZPV) during quench avalanche phenomena. Slow propagating normal zones result in the Joule heating localization that may lead to permanent damages of the devices. A marked improvement can be made by enhancing the thermal conductivity of the underlying substrate of YBCO-based CC. We propose an electrically isolated multilayered substrate containing a micron scaled copper layer on the top of a massive fused silica substrate. In order to compute NZPV values, Finite Element Method (FEM) simulations have been performed in COMSOL Multiphysics on a 3D meander-like configuration of such a novel YBCO-based RSFCL. The simulation results have demonstrated an enhancement in NZPVs by promoting the novel RSFCL multistructure as a radical alternative to earlier studied cases. The relevance of copper thickness variation has also been examined.

Recovery Characteristics of GdBCO Superconducting Tape With Cooling Fins and Teflon Coating for Resistive Fault Current Limiter

Recovery time, which is defined as the time during which the superconducting component recovers to its initial condition after the current-limiting operation, is very important to design an SFCL. In this paper, the cooling properties of GdBCO superconducting tape with various types of fins or PTFE (polytetrafluoroethylene:Teflon) coating were investigated. Superconducting tape was heated by current, which was larger than its critical current, in liquid nitrogen. The cooling down speed after the current shut down from film boiling to nonboiling and to the superconducting state was investigated. To clarify the effect of surface condition on the heat transfer characteristics, the superconducting test tapes with various shaped fins or PTFE coating were compared with that without fins/coating. According to the experimental results, it was confirmed that superconducting tape with fins or PTFE coating recovered to the superconducting state faster than that without fins/coating and is hopeful for the cooling design of SFCL.

Can Resistive-Type Fault Current Limiter Operate in Cryogen-Free Environment?

Superconducting fault current limiters are unique devices that offer fast response to fault without need of an external triggering system. Therefore, they are interesting for industrial use, although their price is high. The principle of the resistive fault current limiter is based on the steep current-voltage characteristic of superconductors. When the current rises over the critical one, voltage on the superconductor rises steeply, and this mechanism blocks the increase of the current. Simultaneous appearance of voltage and current during this limiting period of operation generates a substantial amount of heat that is dissipated in the superconducting wire causing a rapid increase of its temperature. In this contribution, we further develop the idea that, during a limiting period, there is only a small difference between cooling by liquid nitrogen and adiabatic conditions. Using this approach, one can think about a current limiter free from a liquid coolant using a cryocooler. In this contribution, we discuss main differences in cooling conditions and test the idea on a short sample of the high-temperature superconductor REBCO conductor. We compare the behavior of identical samples cooled to the same temperature by liquid nitrogen and conduction cooled. If the realization can be achieved, the huge benefit would be an FCL with a tunable triggering current via its operating temperature.

Transient stability improvement of doubly fed induction generator based variable speed wind generator using DC resistive fault current limiter

Currently, the doubly fed induction generator (DFIG) is getting wider popularity due to its ability to adapt with variable wind speed and to capture more wind energy. According to the grid code, transient stability enhancement of the DFIG system is very important. Though DFIG has a salient feature of the fault ride through capability, this is not sufficient to preserve the necessity of the grid code when the DFIG system is connected with the grid. To accomplish this goal, a DC resistive superconducting fault current limiter (SFCL) is proposed, as it reduces the system power losses during stable operation of the network with improved system efficiency, in comparison with the conventional SFCL. To verify the performance of the transient stability of the DFIG based wind power system with the DC resistive SFCL, both the symmetrical and asymmetrical faults are considered. The performance of the DC resistive SFCL is compared with that of the series dynamic braking resistor (SDBR) and the crowbar system. Simulations are carried out by using the Matlab/Simulink software. Simulation results clearly indicate that the proposed DC resistive SFCL improves the transient stability of DFIG based variable speed wind generator well. Moreover, the overall performance of the proposed method is better than that of the SDBR, as well as the crowbar system.