DC Reactor Type Research Articles

System Studies of DC Reactor Type Fault Current Limiter in Distribution Grid

A DC reactor type fault current limiter (FCL) in series with a downstream circuit breaker can be a solution to control fault current levels in electrical distribution systems. In order to integrate the DC reactor type FCL in to power grid, the performance of the DC reactor FCL should be studied. In this paper, short circuit analysis, based on the electromagnetic transient program (EMTP), has been used to investigate the behavior of the DC reactor type FCL installed in an electrical distribution grid. System studies show that the DC reactor type FCL can not only limit the fault current to an acceptable value, but also can mitigate the voltage sag. The Transient Recovery Voltage (TRV) could be damped in the presence of the DC reactor type FCL during fault clearing period, too

Distribution system protection by coordinated DC Reactor Fault Current Limiters (DCRFCL)

One of the most serious issues that requires special attention is the protection of distribution networks. Using the proper protective equipment improves the safety of the power distribution network during fault conditions. Fault current limiter (FCL) is a type of modern preservation system used to protect power networks and equipment. The voltage restoration of buses during faulty conditions is one of the main concerns of power networks. A group of coordinated DC reactor type fault current limiters are designed and tested in this study to protect the network and restore its bus voltage during the fault period. The proposed FCLs coordination strategy is modelled and simulated in the MATLAB platform, and the results are validated.

Distribution system protection by coordinated fault current limiters

The protection of distribution networks is one of the most substantial issues, which needs special attention. Using appropriate protective equipment enhances the safety of the power distribution network during the fault conditions. Fault current limiter (FCL) is a kind of modern preserving system being used for protecting power networks and equipment. One of the main concerns of power networks is the voltage restoration of buses during faulty conditions. In this study, a group of coordinated DC reactor type faults current limiters are designed and tested to protect the network and restore its buses voltage within the fault period. To coordinate FCLs and measurement devices during the fault sequences, a wireless communication system and decision-making computer are used. The proposed FCLs coordination strategy is modelled and simulated in MATLAB platform and the results are validated by the developed laboratory test setup.

Novel high performance DC reactor type fault current limiter

This paper presents a novel structure for DC reactor type fault current limiter (DRFCL), which can suppress the fault current in distribution networks. The proposed DRFCL is composed of a DC reactor, a bridge rectifier, and anti-paralleled IGBTs power electronic (PE) switch. The DC reactor contains main and supplementary windings. The main winding has a high inductance and acts as a DC reactor. The supplementary winding is used as a control means for fast FCL operation. The fast response allows the cost, weight and volume of the DC reactor to be reduced. The proposed DRFCL reduces the overvoltages on the devices and it has lower number of components, therefore, it can be economic. Analytical solutions, to describe the performance of the proposed DRFCL are presented and the proposed model is simulated via MATLAB software. Finally, a one-phase prototype structure is built and experimental results are studied to show the capability of the proposed DRFCL.

Non‐superconducting fault current limiters

AbstractThis paper proposes the use of non‐superconducting DC reactor type fault current limiter (NSFCL) instead of superconducting fault current limiters (SFCLs) which has high cost and technology. Proposed FCL consists of three similar sets, each including a diode bridge and a single non‐superconducting DC reactor. The device is connected in series with distribution line and it has almost no effect on the normal system operation. It is not necessary to use a control circuit and it has a simple and cheap power circuit. Design characteristics, analytical analysis and overall transient and steady‐state performance of NSFCL in normal and fault conditions are presented in this paper. The comparison between experimental and simulation results indicate good agreements. The results confirm that the power loss of NSFCL is a very small percentage of distribution line power. Also, the system current and load voltage distortions due to using NSFCL is explained and simulated. Copyright © 2008 John Wiley & Sons, Ltd.

Performance Comparison of a DC Hybrid Type FCLI With Other Types

Fault current limiting and interrupting performances of three types of fault current limiting interrupter (FCLI) are compared; a DC reactor type, a DC S/N transition type and a DC hybrid type, which are made of the Bi-2223 tape and bulk. The DC hybrid type FCLI can limit a fault current by means of the inductance of HTS coil and the normal resistance of high temperature superconducting bulk (HTSB). In the case of an accident, the normal transition of the bulk can be accelerated by the magnetic field of the HTS coil. In this paper, performances of the DC hybrid type three-phase FCLI are compared analytically with the DC reactor type and the DC S/N transition type. Features derived from the combination of a reactor coil and an S/N transition element for the DC hybrid type are discussed and as an example it is applied to 6.6 kV-2000 A power distribution system.

The Short-Circuit Characteristics of a DC Reactor Type Superconducting Fault Current Limiter With Fault Detection and Signal Control of the Power Converter

In general case of DC reactor type superconducting fault current limiter (SFCL), a fault current gradually increases during the fault. It takes above 5 cycles to cut off the fault in the existing power system installed the conventional circuit breakers (CBs). Therefore, the fault current increases during the fault even if the SFCL is installed. This paper proposes a technique for decaying the fault current with the function of the fault detection and control of power converter of the SFCL. Using the proposed method, the fault current can decay after 1-2 cycles when the fault occurs. To analyze this technique, three-phase 6.6 kV/200 A SFCL was fabricated. The SFCL has just one DC reactor, an AC to DC power converter which has thyristors as the rectifying device, and a three-phase transformer, which is called magnetic core reactor (MCR). The short-circuit tests of this SFCL were performed successfully. Comparing the result using the proposed technique with the typical result, the fault current is decreased effectively by the proposed technique. This result shows that this SFCL using the fault detection and control of power converter can be applied to the existing power system which has conventional CBs.

DC dual reactor type superconducting fault current limiter using switching operation of YBCO thin films

In this paper, we propose DC dual reactor type superconducting fault current limiter (SFCL) using switching operation of YBa2Cu3OX–7(YBCO) thin films. The proposed DC dual reactor type SFCL consisted of a bridge diode, inductively coupled two coils and YBCO thin films. Two coils, each of which was connected in series with an YBCO thin film, were wound in parallel to the opposite winding direction. DC dual reactor type SFCL using the switching operation of YBCO thin films do not require the interrupter and its controller for the detection of the fault current unlike the conventional DC reactor type SFCL. In addition, the magnetic coupling between two coils in the DC dual reactor type SFCL can not only contribute to the equal balancer for currents passing through each coil before a fault accident but also achieve the balanced power burden between two YBCO thin films during a fault time. Through the experiments, the fault current limiting characteristics of the DC dual reactor type SFCL were investigated and its merits were described. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

전원단 및 부하단 사고에 따른 DC 리액터형 고온초전도 전류제한기 동작특성

본 논문은 사이리스터 또는 GTO사이리스터를 이용한 변형된 DC리액터형 고온초전도 전류제한기의 부하단 사고시 사고전류 제한동작 뿐아니라 전원단 사고로 인해 부하로의 전력공급이 중단되었을 경우, 평상시 초전도코일에 저장된 에너지를 이용하여 부하에 연속적인 전력을 공급할 수 있는 기능을 수행할 수 있음을 분석하였다. 시뮬레이션결과는 이론적인 분석과 일치함을 나타내었다.<br/>

Development of 6.6 kV-200 A DC Reactor Type Superconducting Fault Current Limiter

As a part of the 21st Century Frontier R&D Program in Korea being performed from 2001, a DC reactor type superconducting fault current limiter (SFCL) is being developed. The target of the first phase is to develop a 6.6 kV/200 A class 3-phase SFCL as a prototype for a 154 kV class. This prototype SFCL has a magnet wound with a high-T/sub c/ superconducting wire (Bi-2223) operating at 65 K. The magnet uses solenoid bobbins with grooves for the tape wire. Its inductance is about 84 mH. An AC-DC power converter was made with light trigger thyristor (LTT) having a phase controller. The maximum voltage is 7 kV. The DC reactor, which is cooled by sub-cooled nitrogen, uses a three phase transformer with dual tap for series connection with a power line. Through several experiments this SFCL shows current limiting performance about 50% of short circuit current at short run tests.

Characteristic Analysis of Solid Materials for Electrical Insulation of HTS Magnets

Following the successful development of practical high temperature superconducting (HTS) wires, there have been renewed activities in developing superconducting power equipment. HTS equipment has to be operated in a coolant such as liquid nitrogen (LN/sub 2/), or cooled by conduction-cooling method such as using Gifford-McMahon (G-M) cryocooler to maintain the temperature below critical level. In this paper, the dielectric strength of some insulating materials, such as polyimide film, epoxy, and Teflon tape in LN/sub 2/ were measured. The insulation materials for HTS current lead cooled by cryocooler needs to satisfy two opposing requirements: electrical insulation and heat conduction. To meet the two requirements, a thermal link that consists of oxide free copper (OFC) sheets, polyimide films, glass GFRP plates, and interfacing material was fabricated. Polyimide film was used as an electrical insulator for the current lead. Surface flashover voltage of glass fiber reinforced plastic (GFRP), the basic property of designing HTS solenoid coil, was also analyzed. Epoxy is a good insulating material but fragile at cryogenic temperature. The multi-layer insulating method for current lead has been suggested to compensate for this fragile property. It consists of Teflon tape layer and epoxy layer fixed by fiber material. Based on these measurements, conduction-cooled HTS current lead for 1.2 kV class DC reactor type high temperature superconducting fault current limiter (HTSFCL) and 6.6 kV class HTS magnets for same type HTSFCL cooled by sub-cooled LN/sub 2/ were successfully fabricated and tested.

Design, Fabrication, and Test of High-Tc Superconducting DC Reactor for Inductive Superconducting Fault Current Limiter

A high-T/sub c/ superconducting (HTS) DC reactor has been developed as a part of DC reactor type superconducting fault current limiter (SFCL) rated on 6.6 kV/200 A. The DC reactor was a solenoid coil and was wound with a 4-parallel stacked tape. This coil has 5 layers which are connected in series each other. The inductance of the coil is about 84 mH. This paper deals with the design, fabrication and testing of the DC reactor. For this design of the coil, a prototype solenoid coil had been used. Using the experimental result of a prototype solenoid, the number of stacks and the inductance were designed. The winding machine for the HTS solenoid was manufactured. Using this machine, the large-scale HTS solenoid using a Bi-2223 tape was fabricated successfully. Characteristics of the fabricated coil were observed through a measurement of voltage as current transportation.

Proposal of DC shield reactor type superconducting fault current limiter

Saturated DC reactor type superconducting fault current limiter (SFCL) had been proposed two years ago. It was classified to rectifier type SFCL. The changing inductance value with the operating mode has superior characteristics to reduce voltage sag during step increase of the load current. But it has the disadvantage of its weight. In this paper, rectifier type SFCL with shielded reactor has been proposed. The reactor which has superconducting ring or tube inside its winding is substituted to the DC link of the rectifier. The configuration looks like an air core transformer with secondary short winding. When the current through the bulk shield-ring reaches to a certain level, the flux penetrates to the shield body and finite impedance appears in the primary winding. In other words, when the surface flux density exceeds its critical flux density, the flux penetrates into the bulk superconductor, and increases equivalent inductance. The equivalent transient resistance of the shield was represented as a function of exponential of the time. Using this equivalent transient resistance, the transient impedance was expressed. The transient wave analysis using EMTDC (electro-magnetic transients in DC systems) has been described. Simulated waveforms are shown considering the source inductance, the leakage inductance, the coupling coefficient and the forward voltage drop of the semiconductor. And voltage sag was also investigated with 50% step load increase. Preliminary design was also performed. The coil size and number of turns are designed to obtain adequate inductance for the current limitation, and the central magnetic field of the coils are calculated. There is optimal aspect ratio to minimize the magnetic field with restriction in outer diameter of the coil.

DC reactor type 고온호전도 한류기의 턴간 절연 특성

Fault current limiters (FCL) are extensively needed to suppress fault currents, especially for trunk power systems heavily connected to high voltage/large current transmission lines. Due to its ideal electrical behavior, high-temperature superconductor fault current limiter (HTSFCL) becomes one of the most important developing trends of limiters in power system. This paper describes the result of an investigation of the dielectric characteristics of turn-to-turn insulation for pancake and solenoid type reactor coil in liquid nitrogen. The influence of thickness in a variety length, on AC, DC and impulse surface flashover has been investigated. Also, the relationships between the number of turn and breakdown characteristics were clarified. The information gathered in this test series should be helpful in the design of liquid nitrogen filled DC reactor type HTSFCL.

A Study on the Modeling of Superconducting Fault Current Limiters Using EMTDC

An effective modeling and simulation schemes of a resistive type Superconducting Fault Current Limiter (SFCL) and DC reactor type SFCL using PSCADIEMTDC are proposed in this paper. In case of resistive type SFCL, current limiting is implemented by the ultra-fast transition characteristics from the superconducting (non-resistive) state to the normal (resistive) state by overstepping the critical current density. The states can generally be divided into three sub-states: the superconducting state, the quench state and the recovery state, respectively. In case of DC reactor type SFCL, it is composed of a superconducting coil and a diode bridge through which AC line current is rectified, and the increase in fault current is limited by the inductance of a superconducting coil. An actual experiment based component model of the real resistive type SFCL is developed and applied for the simulation. The proposed modeling and simulation schemes can be implemented to the grid system readily under various system conditions including sort of faults and the system capacity as well. The simulation results demonstrate the effectiveness of the proposed model and simulation schemes.

Design and test of modified bridge type superconducting fault current limiter with reverse magnetized core

To develop a DC reactor type Superconducting Fault Current Limiter (SFCL), the most important elements are superconducting magnets or inductors. Recently large size magnets have been developed, according with the improvement of high temperature superconducting wire. In the DC reactor type SFCL, the purpose of a magnet is to store the generated electric energy of the power system immediately after a fault. Therefore most inductors are designed with an air core since the magnetic core inductor is too easy saturated to absorb the energy. Therefore the inductor consumes so much superconducting wire to make a large inductance and these expensive coils are a weak point of the DC reactor type SFCL. To solve this problem, the Reverse Magnetization Bias (RMB) method is introduced. The energy capacity of magnetic core is expanded to several times. With a shorter length of HTC superconducting wire, a much improved effect was obtained in the 40 V prototype SFCL.

Design of 6.6 kV, 100 A saturated DC reactor type superconducting fault current limiter

Proposed saturated DC reactor type superconducting fault current limiter (SFCL) was designed and fabricated. The rated value was 100 V and 10 A for small scale experiment. The relationships between the one-turn voltage and the cross section of the core, the inductance value are obtained. The optimized cross section of the core was 90 mm /spl times/ 45 mm under restriction of the core manufacturer. The core material was ultra fine grain steel named FINEMET/sup /spl reg// FT-3H. The number of main winding turns was 100 and that of the control winding was also 100 turns. The wires are of NbTi superconductor with different filament diameter. We enhanced this design scheme to 6.6 kV, 100 A SFCL. The core cross section size and core gap and core length of 6.6 kV design are presented.

Waveform analysis of the bridge type SFCL during load changing and fault time

DC reactor type superconducting fault current limiter (SFCL) has drawn the interest of some researchers in developing such device and more research work is being carried out in order to make it practically feasible. We have pointed out one issue that is not properly examined yet on such a device during load changing time. As we know, it is very difficult to introduce DC bias voltage to the reactor coil of the bridge type SFCL and some researchers are developing such device without using DC bias current. In such a case, the voltage drop occurs at the load terminal during the load increasing time caused by the DC reactor's inductance. By using the Electro-Magnetic Transients in DC systems which is the simulator of electric networks (EMTDC) software we carried out analysis of first few half cycles of the voltage and current waveforms after the load is increased. We also performed the same analysis for fault conditions. The peak value of the waveforms is considered in calculating the voltage drop at load terminal during the load changing time. The analysis can be used in selecting an appropriate inductance value for designing such SFCL.

Preliminary experiments on saturated DC reactor type fault current limiter

Preliminary experiments have been performed on our proposed saturated DC reactor type superconducting fault current limiter (SFCL). The proposed SFCL is similar to a DC reactor type but an additional control winding is used. The DC bias current in the control winding saturates the core. The B-H curve of a magnetic circuit shows that low inductance value can be achieved in saturated region and high value in unsaturated region. The inductance of the saturated reactor depends on type of magnetic material, core size, number of turns and biasing conditions. The advantage of this type of SFCL over the existing DC reactor type is that, it shows low inductance value at normal operation and high value during fault time. On the other hand, the present DC reactor type SFCL shows a fixed value of inductance both in normal and fault time. In our experiment, we observed the inductance behavior of the saturated reactor by changing the control current. In order to make the work simple and convenient we have chosen a ferrite core. The experimental results are presented in this paper.

A variation of impedance of a high-Tc superconducting fault current limiter with an open core

The high-Tc superconducting fault current limiter (SFCL) is studied worldwide to be classified into a resistive type and an inductive type such as a magnetic shielding type and a DC reactor type. The high-Tc SFCL with an open core belongs to the magnetic shielding type SFCL. Unlike conventional magnetic shielding type SFCLs, it uses the open core to reduce the mechanical vibrations and installed space. The high-Tc SFCL with an open core was designed and manufactured by stacking three BSCCO-2212 tubes and it was tested in the maximum source voltage of 400 Vrms and the results such as the reduction of fault current and impedance of the SFCL are described in this paper. The results show that the fault current in the source voltage of 400 Vrms was reduced to be about 123 A peak and it is about 3.9 times as the normal state current. Also, the impedance of the high-Tc SFCL was about 9 /spl Omega/ to be about 9 times the normal state impedance. The impedance of the SFCL appears just after the fault, and the size of it is dependent on the source voltage. From the impedance, the inductance of the SFCL was calculated.