Showing papers on "Fault current limiter published in 2007"

High-temperature superconductor fault current limiters: concepts, applications, and development status

Abstract: The application of superconducting fault current limiters (SCFCLs) in power systems is very attractive because SCFCLs offer superior technical performance in comparison to conventional devices to limit fault currents. Negligible impedance at normal conditions, fast and effective current limitation within the first current rise and repetitive operation with fast and automatic recovery are the main attributes for SCFCLs. In recent years there has been a significant progress in the research and development (R&D) of SCFCLs. This paper gives an extended review of different SCFCL concepts, SCFCL applications and the R&D status. Within the first part of this paper the most important SCFCLS and, to a limited extent, non-superconducting fault current limiter (FCL) concepts are explained and compared. The second part reviews interesting SCFCL applications at the distribution and transmission voltage level and the third part shows in detail the R&D status. It can be summarized that SCFCLs are, at present, not commercially available but several successful field tests demonstrated the technical feasibility of SCFCLs. First distribution level applications are expected soon. Considerable economical and technical benefits can be achieved by applying SCFCLs at the distribution and transmission voltage level.

Recent Progress in Second-Generation HTS Conductor Scale-Up at SuperPower

Abstract: YBa2Cu3Ox (YBCO) second-generation (2G) HTS conductors have been produced in lengths over 300 m in pilot scale facilities established at SuperPower. High throughput pilot-scale manufacturing has been demonstrated with tape speeds at or above 30 m/h of 12 mm wide tape (corresponding to 90 m/h of 4 mm wide conductor) in all steps. A 322 m long conductor with a minimum critical current value of 219 A/cm has been produced, which corresponds to a critical current x length value of 70,520 A-m. A 270 m long, 4 mm wide conductor with an end-to-end critical value of 100 A has also been demonstrated. In a campaign to manufacture 2G conductor for the Albany cable project, SuperPower has produced 12,470 m of conductor that meets or exceeds the specification for piece length (42.4 m) and critical current (100 A/cm). In fact, more than 55% of the conductor produced is at least 100 m in piece length and more than 27% greater than 200 m in piece length. In addition to scaling up 2G conductors to high-throughput pilot-scale manufacturing, we have demonstrated high critical currents in short samples produced by Metal Organic Chemical Vapor Deposition (MOCVD). Critical current values of 557 A/cm have been achieved in 2.1 micrometer thick films in 12 mm wide, 10 cm long tapes. These samples exhibit a critical current value of 116 A/cm at 1 T and 76 K, in the orientation of field parallel to the c-axis. We have also constructed a 4-pancake coil that generated a magnetic field of 1.1 T at 77 K and 2.4 T at 64 K. A Fault Current Limiter (FCL) assembly has been successfully constructed and tested at high power levels. A prospective current of 90 kA was successfully limited to 32 kA within 1 ms without any HTS element failure.

Development of Saturated Iron Core HTS Fault Current Limiters

Abstract: We have been carrying out a saturable iron core reactive type superconducting fault current limiter (SFCL) development program since 2002. The major two disadvantages that people used to be foretold for a saturable iron core reactive type SFCL are the massive use of iron (resulting in large size, heavy weight, and high cost) and the high induced voltage hazard to the dc superconducting coil (this may damage the current supply of the dc bias) as a fault takes place. We have found the ways to deal with these two problems, making such kind of equipment reliable and cost effective. In this paper, we will report the technical data and testing results of a 3 phase lab testing model. Some key design parameters of the 35 kV/100 MVA prototype will also be presented.

IGBT Fault Protection Based on di/dt Feedback Control

Abstract: Customer power modules built with the latest IGBT chips may be operated to their extreme conditions in terms of junction temperature, switching speed and voltage and current ratings This is of particular advantageous in electric/hybrid vehicle applications where power density is a critical design factor With IGBTs operated at extreme conditions the fault response time with a traditional IGBT fault protection approach, such as Vce sensing approach, may not be fast enough This paper presents a circuit configuration to identify an IGBT fault current by means of measuring the induced voltage across the stray inductance between the IGBT Kelvin emitter and power emitter Upon fault current detection a feedback control is introduced to dynamically control the di/dt of the fault current Once the fault current is contained at a predetermined level, a slow turn off mechanism is deployed The effectiveness of the proposed IGBT protection scheme was validated with customer power modules using Infineon 3rd generation IGBT chips rated at 600 V 1000 A for 100 kW electric drive systems used in fuel cell powered electric vehicles

The Development of Second Generation HTS Wire at American Superconductor

Abstract: Development of the second generation (2G) YBCO high temperature superconducting wire has progressed rapidly and its performance is approaching, and in some areas exceeding, that of first generation (1G) HTS wire. American Superconductor's approach to the low-cost manufacturing of 2G wire is based on a wide-strip (4 cm) process using a metal organic deposition (MOD) process for the YBCO layer and the RABiTS (rolling assisted biaxially textured substrate) process for the template. In addition, the wide-strip RABiTS/MOD-YBCO process provides the flexibility to engineer practical 2G HTS wires with architectures and properties tailored for specific applications and operating conditions through slitting to custom widths and laminating with custom metallic stabilizers. This paper will review the status of the 2G manufacturing scale up at AMSC and describe the properties and architecture of the 2G wire being developed and tested for various applications including in cables, coils and fault current limiters. Performance of 100 meter class, 4 mm wide wires at 77 K, self-field has reached 100 A (250 A/cm-width) with single-coat YBCO and 140 A (350 A/cm-width) with double-coat YBCO. A 5 cm inner diameter coil fabricated from the latter wire achieved 1.5 T at 64 K, confirming the capability of the wire for coil applications.

Current source with indirect load current signal extraction

Abstract: A switching circuit for supplying current to a load has a switching element, an inductive element coupled to the switching element, and a load current extraction circuit responsive to current in the inductive element for producing a load current signal as a simulated current approximating current in the load.

Second Generation High-Temperature Superconducting Wires for Fault Current Limiter Applications

Abstract: In this paper, we report the results from evaluation on the use of 2nd generation high-temperature superconducting wires, or 2G HTS conductors, as elements for superconducting fault current limiter (SFCL). The unique features of 2G HTS conductors such as high N-values, superior electromechanical performance, large surface area available for cooling, and their availability in long-lengths that could be produced by high-throughput and low-cost manufacturing, may provide advantages for SFCL applications. We tested SuperPower's standard ion-beam-assisted-deposition based 2G HTS conductors under various conditions. First, individual conductors 10-20 cm long with dc critical current (Ic) ranging from 180 amps to 277 amps were tested at prospective fault current up to 3 kA (peak). 2G HTS conductors demonstrated good fault current limiting performance, including first peak limitation. Quench current was in the range of 1.8 to 3 times Ic, and the response time was within 1 ms. Secondly, 3-5 conductors in parallel connections demonstrated uniform current sharing and fast recovery under no-load condition. Finally, an assembly consisted of 12 elements in series connection was tested at high-power condition at KEMA PowerTest. Each element had four 40 cm long conductors with Ic 120 A in parallel connection. With 1080 V supply voltage and 90 kA prospective fault peak current, the fault current was limited to 32 kA at the 1st peak with 3.2 kA in the HTS elements. The response time was less than 1 ms. All these testing results indicate that our 2G HTS conductors are promising for practical SFCL applications.

System Studies of the Superconducting Fault Current Limiter in Electrical Distribution Grids

Abstract: A superconducting fault current limiter (SFCL) in series with a downstream circuit breaker could provide a viable solution to controlling fault current levels in electrical distribution networks. In order to integrate the SFCL into power grids, we need a way to conveniently predict the performance of the SFCL in a given scenario. In this paper, short circuit analysis based on the Electromagnetic Transient Program was used to investigate the operational behavior of the SFCL installed in an electrical distribution grid. System studies show that the SFCL can not only limit the fault current to an acceptable value, but also mitigate the voltage sag. The transient recovery voltage (TRV) could be remarkably damped and improved by the presence of the SFCL after the circuit breaker is opened to clear the fault.

New Method for Detecting Low Current Faults in Electrical Distribution Systems

Abstract: In electrical distribution systems, low current faults may be caused by a high impedance fault or by the fault current limitation caused by the neutral to ground connection. In the former case, an indirect contact or insulation degradation give a high value of the fault impedance. In the latter, the neutral grounding may be either isolated or compensated. Nevertheless, these types of faults do not produce enough current so that the traditional overcurrent relays or fuses are not able to detect the fault. This paper presents a new methodology, based on the superposition of voltage signals of certain frequency, for the detection of low current single phase faults in radial distribution systems. The simulation analysis and laboratory tests carried out have proved the validity of the methodology for any type of grounding method.

Finite-element modelling of YBCO fault current limiter with temperature dependent parameters

Abstract: In this paper, we present a numerical model which takes into account both the thermal and the electromagnetic aspects of the over-critical current regime for high-temperature superconducting (HTS) materials. The electromagnetic and thermal equations have been implemented in finite-element method (FEM) software in order to obtain a novel model for investigating the behaviour of the materials when the current exceeds Ic and the superconductor material goes to the normal state. The thermal dependence of the electrical parameters, such as the critical current density Jc, has been introduced. This model has been used to analyse the behaviour of strip lines of a YBCO/Au fault current limiter (FCL) on a sapphire substrate. Simulations with currents exceeding Ic have been performed, showing that the current limitation phase can be correctly reproduced. Such a model can be used to study the influence of the geometry on the performance of the FCL. It can replace experiments with currents exceeding Ic which may damage or destroy HTS samples and devices.

Investigation of YBCO Coated Conductors for Fault Current Limiter Applications

Abstract: The switching behavior of second generation (2G) HTS wires with a coated conductor (CC) architecture for application in fault current limiters (FCL) has been studied. Measurements have been performed on short pieces of meter length, as well as on bifilar coils wound from 20 meters of CC. CCs with and without stainless steel stabilizers have been compared regarding the temperature reached after applying a constant voltage per length to the conductor for a certain time (typically 50 ms). Three coils from stainless steel stabilized wires have been connected in series to demonstrate uniform switching of the individual coils in a single phase FCL model with 120 kVA nominal power. The response to transient currents has been investigated by applying currents above the critical current Ic with different amplitudes and measuring the time at which an irreversible voltage increase occurs. All CCs investigated proved well suitable for FCL applications exhibiting the required uniformity and excellent current limiting performance.

Thermal and Electrical Analysis of Coated Conductor Under AC Over-Current

Abstract: In order to design a high temperature superconducting (HTS) winding for the fault current limiter (FCL), the resistance and the temperature of the winding should be calculated quantitatively under the over-current caused by fault condition. In this paper, a transient analysis is performed to estimate the resistance development and the temperature rise of coated conductor (CC) under AC over-current. A one-dimensional thermal conduction model with an electrical circuit model is developed for the solenoid coil configuration at 65 K cooling condition. All the composite materials except the buffer layer in CC are considered in the model. Two kinds of stabilizer materials (copper/stainless steel) are considered to investigate the current limitation of CC. The simulation results are compared with the experimental data of the commercial CC. The effect of Ag and solder layer on the simulation result are revealed for CC.

Study on the Effect of Fault Current Limiter in Power System With Dispersed Generators

Abstract: Dispersed generators are being introduced to power systems to secure the electric power supply. However, a short-circuit capacity of the power system increases with the introduction of dispersed generators. As a result, there is concern that a fault current will increase further, and instantaneous voltage sag might be caused. It is proposed to apply a superconducting fault current limiter in the distribution system with dispersed generators to solve these issues. In this paper, the effect of superconducting fault current limiter in this power system is studied by the analysis with EMTP and the confirmation test is conducted with a simulator.

Simulations and experimental analyses of the active superconducting fault current limiter

Abstract: This paper presents the operation principle of a new type active superconducting fault current limiter (SFCL). The SFCL is composed of an air-core superconducting transformer, a PWM converter and a superconducting magnet. The primary winding of the air-core superconducting transformer is in series with AC main circuit, and the second winding is connected with the superconducting magnet through a PWM converter. In normal (no fault) operating state, the flux in air core is compensated to zero, so the SFCL has no influence on main circuit. In the case of short circuit, by controlling the amplitude and phase angle of the second winding’s current, the limiting impedance which is in series with the AC main circuit can be regulated and the fault current will be limited to a certain level. Using MATLAB SIMULINK, the simplified model of the active SFCL is created, and simulations validate this SFCL can suppress the fault current effectively. In addition, the current-limiting experiment is done with a small conventional transformer. Experimental results correspond well with simulation results.

Fault Current Limiting Characteristics of Separated and Integrated Three-Phase Flux-Lock Type SFCLs

Abstract: The fault current limiting characteristics of the separated and the integrated three-phase flux-lock type superconducting fault current limiters (SFCLs) were analyzed. The three-phase flux- lock type SFCL consisted of three flux-lock reactors and three high-TC superconducting (HTSC) elements. In the integrated three-phase flux-lock type SFCL, three flux-lock reactors are connected on the same iron core. On the other hand, three flux-lock reactors of the separated three-phase flux-lock type SFCL are connected on three separated iron cores. The integrated three-phase flux-lock type SFCL showed the different fault current limiting characteristics from the separated three-phase flux- lock type SFCL that the fault phase could affect the sound phase, which resulted in quench of the HTSC element in the sound phase. Through the computer simulation applying numerical analysis for its three-phase equivalent circuit, the fault current limiting characteristics of the separated and the integrated three-phase flux-lock type SFCLs according to the ground fault types were compared.

Investigation of YBCO Coated Conductor for Application in Resistive Superconducting Fault Current Limiters

Abstract: These R&D of YBCO coated conductor wire is progressing very fast. The manufacturing lengths for a single wire have reached up to several hundred meters with high quality. Due to its promising cost predictions, YBCO coated conductor (CC) material might considerably increase the economic feasibility of superconducting power devices (cables, transformers, machines, current limiters and energy storage) in near future. The main requirement for YBCO wire in resistive superconducting fault current limiters (SCFCLs) is quench safety for various short-circuit conditions. Up to now, only a few authors report on this subject. This paper presents experimental quench test results with short and medium length samples of YBCO coated conductor wire for different test conditions. The experimental results confirm the feasibility of YBCO coated conductor wire for application in resistive SCFCLs. Short samples showed fast and effective limitation up to an electric field of 2.7 V/cm for a short-circuit time of 100 ms without material degradation. Even relatively inhomogeneous short samples showed a non-destructive quench. The tests clearly demonstrate that a good contact between the cap layer and the substrate is mandatory to avoid hot spots during quench.

Development of 220 V/300 A Class Non-Inductive Winding Type Fault Current Limiter Using 2G HTS Wire

Abstract: As a part of the 21st Century Frontier R&D Program in Korea being performed from 2004, a non-inductive winding type superconducting fault current limiter (SFCL) is being developed. The target of the second year in phase II of the program is to develop a 220 V/300 A class non-inductive winding type SFCL as a prototype for a 13.2 kV/630 A class, the final goal of phase II. This SFCL has three solenoid type non-inductively wound coils in series using a 2G high temperature superconducting (HTS) wire and it was tested in sub-cooled nitrogen of 65 K, 1 atm. A coil which is composed of four parallel windings in a bobbin and winding directions are opposite to have non-inductive characteristics. Three coils were connected in series and the total length of 108 m of 2G HTS wire was used. Short-circuit tests were performed at applied voltage of 220 V and the SFCL limited the fault current to a few kA extents at the tests. Recovery time of the SFCL was measured after short-circuit tests.

Optimum Fault Current Limiter Placement

Abstract: Due to the difficulty in power network reinforcement and the interconnection of more distributed generations, fault current level has become a serious problem in transmission and distribution system operations The utilization of fault current limiters (FCLs) in power system provides an effective way to suppress fault currents and result in considerable saving in the investment of high capacity circuit breakers In a loop power system, the advantages would depend on the numbers and locations of FCL installations This paper presents a method to determine optimum numbers and locations for FCL placement in terms of installing smallest FCL parameters to restrain short-circuit currents under circuit breakers' interrupting ratings In the proposed approach, sensitivity factors of bus fault current reduction due to changes in the branch parameters are derived and used to choose candidates for FCL installations A genetic-algorithm-based method is then designed to include the sensitivity information in searching for best locations and parameters of FCL to meet the requirements Test results demonstrate the efficiency and accuracy of the proposed method

High-Tc Superconducting Fault Current Limiting Transformer (HTc-SFCLT) With 2G Coated Conductors

Abstract: We developed a 3-phase, 100 kVA, 6600 V/210 V high temperature superconducting fault current limiting transformer (HTc-SFCLT) with functions of both superconducting transformer and fault current limiter. The HTc-SFCLT is characterized by the application of 2G coated conductors with the higher current limiting performance and flexibility than that of the HTc-SFCLT with 1G Bi2212/CuNi composite bulk material. Fundamental tests of the HTc-SFCLT were carried out, and the design parameters as a superconducting transformer and as a superconducting fault current limiter were verified.

A fault current limiter based on an LC resonant circuit: Design, scale model and prototype field tests

Abstract: This paper presents relevant aspects of a project to design and install a FCL of the resonant link type. This device consists of a series reactor and capacitor, tuned to 60 Hz. The series capacitor is shunted by a saturable reactor when a fault occurs.

Fault current limiting

Abstract: An alternating current system 10 has a primary circuit 11 which forms a primary winding 18 on a core 16. A secondary winding 24 is connected with a current source 26 or, alternatively, with an impedance 60. The core 16 is threaded by a superconducting coil 20 having a current source 22. In normal use, current in the coil 20 provides a DC bias level of flux in the core 16, and the source 26 is varied to maintain substantially constant flux, thereby minimising losses in the primary circuit 11. In fault conditions, current in the coil 20 is reduced or removed to increase voltage losses across the coil 18, thereby limiting fault current. The impedance 60 can also be switched into circuit, creating further current limiting by virtue of the transformer effect of the windings 18, 24.

High current capable circuit testing closer apparatus and method

Abstract: A circuit testing closer may include a fault isolating switching device coupled between a supply side and a load side of a power distribution system and a current pulse generator coupled in parallel to the switch to generate a current pulse within the power distribution system subsequent to a fault isolation for testing the power distribution system. The current pulse generator may include an electromechanical actuator, an electromagnetic actuator or a solid state switching device. The circuit testing closer may be a purpose-built combination device, or the fault isolating switching device and the current pulse generator may be separately coupled and commonly controlled devices. The fault isolating switching device may have continuous current rating greater than a continuous current rating of the pulse generating device.

New types of FACTS-devices for power system security and efficiency

Abstract: This paper provides an overview of new types of FACTS devices. These devices are considered for applications in real network cases in Europe and China. The value of these FACTS is the improvement of security and efficiency of power transmission networks. Fast controllability in emergency situations provides increased flexibility and therefore stability and security advantages. The flexibility in control allows operating closer to stability limits and improves the efficiency of existing networks. The considered devices are dynamic power flow controller (DPFC), fault current limiter (FCL), Static Synchronous Compensator (STATCOM) with energy storage and Voltage Source Converter based HVDC (VSC-HVDC). The application scenarios are taken from UCTE (Benelux, Austria) and China (Shanghai). The studies are based on public available simplified network data.

Thermal regimes of HTS cylinders operating in devices for fault current limitation

Abstract: We reveal obstacles related to the application of HTS cylinders in current limiting devices based on the superconducting–normal state transition. It is shown that, at the critical current density achieved presently in bulk materials, and especially in BSCCO-2212, the required thickness of the cylinder wall in a full-scale inductive device is several centimetres. A simple mathematical model of the operation of an inductive fault current limiter (FCL) is used to show that such cylinders cannot be cooled in an admissible time after a fault clearing and, hence, the inductive FCLs and current-limiting transformers employing BSCCO cylinders do not return to the normal operation in the time required. For the recovery even with a non-current pause in the circuit, cylinders are needed with a critical current density an order of magnitude higher than the existing one.

Experimental studies of the quench behaviour of MgB2 superconducting wires for fault current limiter applications

Abstract: Various MgB2 wires with different sheath materials provided by Hyper Tech Research Inc., have been tested in the superconducting fault current limiter (SFCL) desktop tester at 24–26 K in a self-field. Samples 1 and 2 are similarly fabricated monofilamentary MgB2 wires with a sheath of CuNi, except that sample 2 is doped with SiC and Mg addition. Sample 3 is a CuNi sheathed multifilamentary wire with Cu stabilization and Mg addition. All the samples with Nb barriers have the same diameter of 0.83 mm and superconducting fractions ranging from 15% to 27% of the total cross section. They were heat-treated at temperatures of 700 °C for a hold time of 20–40 min. Current limiting properties of MgB2 wires subjected to pulse overcurrents have been experimentally investigated in an AC environment in the self-field at 50 Hz. The quench currents extracted from the pulse measurements were in a range of 200–328 A for different samples, corresponding to an average engineering critical current density (Je) of around 4.8 × 104 A cm−2 at 25 K in the self-field, based on the 1 µV cm−1 criterion. This work is intended to compare the quench behaviour in the Nb-barrier monofilamentary and multifilamentary MgB2 wires with CuNi and Cu/CuNi sheaths. The experimental results can be applied to the design of fault current limiter applications based on MgB2 wires.

Test Results on 500 kVA-Class ${\rm MgB}_{2}$ -Based Fault Current Limiter Prototypes

Abstract: The growth in generation and the increased interconnection of electrical grids lead to higher fault currents and therefore there is a considerable interest in fault current limiter (FCL) devices In this work, we refer on the results of electrical testing on resistive-type superconducting FCL prototypes made by Ni-sheathed MgB2, developed in the framework of the Italian Project LIMSAT This is the first time ever that short circuit testing results are reported on MgB2-based FCL prototypes at 27 K, cooled by a liquid neon bath The time evolution of limited current and voltage across SFCL prototypes are reported and analysed Critical aspects associated to the fault event such as the steep HTS tape temperature rise and electrical insulation at cryogenic temperature are also discussed

Conceptual Design of a 110 kV Resistive Superconducting Fault Current Limiter Using MCP-BSCCO 2212 Bulk Material

Abstract: Superconducting fault current limiters (SCFCLs) are new and attractive devices to limit short-circuit currents in power systems. In recent years, the technical feasibility of SCFCLs in medium voltage applications was successfully demonstrated in several field tests. In high voltage power systems the application of SCFCLs is very attractive too, because at this voltage level conventional devices to limit short-circuit currents are hardly applicable and system studies showed considerable economical benefits. Therefore, a German project started recently to develop a first 110 kV, 1.8 kA prototype of a resistive SCFCL. A magnetic triggered resistive concept using MCP-BSCCO 2212 bulk material will be used for the demonstrator. This paper reports about the conceptual design of this SCFCL and the project status. Focus is given on the main data of the 110 kV prototype, the SCFCL modules, the general design of the whole system and the most important high voltage design aspects. The calculations and estimations show that the conceptual design presented in this paper seems feasible and that a major technical challenge is to ensure a reliable electrical insulation system.

Current Limiting Characteristics of a Flux-Lock Type SFCL Dependent on Fault Angles and Core Saturation

Abstract: The flux-lock type superconducting fault current llmiter (SFCL) uses the magnetic coupling between two coils connected in parallel with each other. This SFCL has the merit that both the resistance of high-TC superconducting (HTSC) element and the limiting current capacity can be simultaneously increased through the application of magnetic field into HTSC element. However, like other type of SFCLs using an iron core, unless the saturation of the iron core in the design is considered, the actual limited fault currents can be higher than expected as the saturation of the iron core occurs, and can lead to damage the electrical equipment of the power system. To analyse the dependence of the fault current in the flux-lock type SFCL on the fault angles, its electrical equivalent circuit with the magnetization branch was derived. From the electrical equivalent circuit, the fault current and the inner magnetic flux considering the fault angles as well as the design parameters such as winding direction and inductance ratio of two coils were calculated. The analysis results were compared with the experimental ones, and both the results agreed.

Development and Test of a Superconducting Fault Current Limiter-Magnetic Energy Storage (SFCL-MES) System

Abstract: A superconducting fault current limiter-magnetic energy storage (SFCL-MES) system for substation applications is proposed. SFCL-MES system can limit not only the peak fault current, but also the steady fault current. Moreover, it can provide high-quality power for the critical customers of the substation at the same time. A 100 kJ/1000 A/20 kVA SFCL-MES prototype system is developed, and it mainly consists of a NbTi magnet with two coaxial and homocentric solenoids for reducing stray field, a three-half-bridge converter and a current regulator. The principle of SFCL-MES is analysed, the design and experiment results for the SFCL-MES system are described.