Showing papers on "Fault current limiter published in 2014"
TL;DR: Results show the implementation approach can consistently achieve protection system operating within the order of a few microseconds and validate the overall protection operating times in a low voltage environment.
Abstract: This paper presents a high speed current differential implementation approach for smart dc distribution systems capable of sub-millisecond fault detection. The approach utilizes the natural characteristics of dc differential current measurements to significantly reduce fault detection times compared to standard applications and hence meet requirements for dc converter protection (around 2 ms). Analysis is first developed to help quantify protection implementation challenges for a given dc system. Options for implementing the proposed technique are then illustrated. Results of scaled hardware testing are presented which validate the overall protection operating times in a low voltage environment. These results show the implementation approach can consistently achieve protection system operating within the order of a few microseconds .
211 citations
TL;DR: In this paper, a fault-diagnostic method for interleaved dc-dc converters using only the dc-link current derivative sign features is presented, which is robust to transients and current imbalance between phases and no additional sensors are required.
Abstract: Interleaved dc-dc converters have been widely applied, because of their benefits related to efficiency, size, thermal management, modularity, and output current ripple cancellation. These converters present an enhanced fault tolerance capability, but an open-circuit fault can leads to ripple beyond load requirements. This paper presents a fault-diagnostic method for interleaved dc-dc converters using only the dc-link current derivative sign features. The dc-link current derivative is thoroughly studied for both healthy and faulty modes. Its sign variation during different time intervals defined by the number of switches in conduction mode contains important information for open-circuit fault detection. The presented method is robust to transients and current imbalance between phases and no additional sensors are required. A photovoltaic system application is presented to validate this method.
119 citations
TL;DR: In this article, a tristate pulse-width modulation technique has been employed, in which three adjacent switching states are used to construct the reference voltage, and the active switching states were arranged at the edge and the center of a PWM cycle.
Abstract: Three-phase current reconstruction technique using dc current information in conventional two-level inverters can be used for the purpose of cost reduction and sensor fault tolerance. A novel phase current reconstruction scheme, with reduced immeasurable area and common mode voltage, is proposed in this paper. A tristate pulse-width modulation technique has been employed, in which three adjacent switching states are used to construct the reference voltage. The active switching states are arranged at the edge and the center of a PWM cycle. Fixed sampling and simultaneous three-phase currents can be easily achieved with very little hardware and software requirements. A detailed analysis of the effects of nonidealities leads to regional modifications of the switching sequence resulting in almost the whole hexagon as the feasible area. The usefulness of the proposed reconstruction algorithm has been verified by experimental results obtained from a 4-kW induction motor drive system. Smooth transitions between the redundant and fault-tolerant modes were observed.
106 citations
TL;DR: The resistive value of the SFCL as well as the superconducting coil inductance of the SMES are simultaneously optimized so that a sudden increase in the kinetic energy in the DFIG rotor during faults, an initial stored energy inThe SMES coil, an energy loss of theSFCL, and an output power fluctuation of the D FIG are minimum.
Abstract: This paper deals with a cooperative control of a resistive type superconducting fault current limiter (SFCL) and a superconducting magnetic energy storage (SMES) for enhancing fault ride through (FRT) capability and smoothing power fluctuation of the doubly fed induction generator (DFIG)-based wind farm. When the system faults occur, the SFCL is used to limit the fault current, alleviate the terminal voltage drop, and transient power fluctuation so that the DFIG can ride through the fault. Subsequently, the remaining power fluctuation is suppressed by the SMES. The resistive value of the SFCL as well as the superconducting coil inductance of the SMES are simultaneously optimized so that a sudden increase in the kinetic energy in the DFIG rotor during faults, an initial stored energy in the SMES coil, an energy loss of the SFCL, and an output power fluctuation of the DFIG are minimum. The superior control effect of the cooperative SFCL and SMES over the individual device is confirmed by simulation study.
85 citations
TL;DR: In this article, a superconducting magnetic energy storage with fault current limiting function (SMES-FCL) was proposed to suppress the power fluctuation and low-voltage ride-through performance of doubly fed induction generator (DFIG) wind turbine.
Abstract: The vital problems of doubly fed induction generator (DFIG) wind turbine are power fluctuation and low-voltage ride-through performance. To tackle both problems, the new circuit configuration and optimization technique of the superconducting magnetic energy storage with fault current limiting function (SMES-FCL) in a DC microgrid are presented. The SMES-FCL circuit mainly consists of two DC choppers with common superconducting coil (SC). During normal operation, the SMES-FCL acts as the SMES unit to suppress the power fluctuation of DFIG. When severe faults occur in the system, the SC is automatically connected to the system and used as the fault current limiter. Consequently, the fault current and the terminal voltage drop of DFIG can be alleviated. The energy function method is used to formulate the optimization problem of SC inductance, initial stored energy, and proportional-integral control parameters of choppers. Simulation study confirms the superior control effect of the SMES-FCL over the conventional SMES.
73 citations
TL;DR: In this article, an iterative learning control (ILC) is applied as a current control technique for recovering performance in multiphase permanent magnet (PM) motors under fault conditions, which is well suited for high-performance safety critical applications.
Abstract: Fault-tolerant control (FTC) techniques for multiphase permanent magnet (PM) motors are usually designed to achieve maximum ripple-free torque under fault conditions with minimum ohmic losses. A widely accepted approach is based on flux distribution or back EMF (BEM) model of the machine to calculate healthy phase currents. This is essentially an open-loop technique where currents are determined (based on motor fault models) for each fault scenario. Therefore, it is highly model dependent. Since torque pulsation due to open-circuit faults and short-circuit faults are periodic, learning and repetitive control algorithms are excellent choices to minimize torque ripple. In this paper, iterative learning control (ILC) is applied as a current control technique for recovering performance in multiphase PM motor drives under fault conditions. The ILC-based FTC needs torque measurement or estimation, but avoids the need for complicated fault detection and fault diagnosis algorithms. Furthermore, BEM-based FTC and ILC-based FTC are proposed that initiates the learning from a model-based approximate guess (from the BEM method). Therefore, this method combines the advantages of both model information as well as robustness to model uncertainty through learning. Hence, the proposed method is well suited for high-performance safety critical applications. Finite element analysis and experimental results on a five-phase PM machine are presented for verification of the proposed control schemes.
66 citations
TL;DR: In this paper, a dc resistive type superconducting fault current limiter (SFCL) was designed for the HVDC system, and experiments were conducted to prove the current limiting ability of superconding materials in dc system.
Abstract: A dc resistive type superconducting fault current limiter (SFCL) is presented in this paper. This SFCL is designed for the HVDC system. Experiments are conducted to prove the current limiting ability of superconducting materials in dc system. Uniform current and voltage sharing among the SFCL modules can be observed through contact resistance tests, dc flow-through tests, and ac flow-through tests. Results of tests show that each limiting module has good uniformity in higher current system. Then, system simulation model based on these experimental data is built in PSCAD, and simulations are carried out to determine the value of shunt resistor. Results of simulation show that SFCL has fast responding time and good current limiting performance in dc network.
66 citations
TL;DR: In this paper, a modified configuration of bridge-type fault current limiter (BFCL) is proposed to check the effectiveness of the proposed BFCL, its performance is compared with that of the series dynamic braking resistor (SDBR).
Abstract: Fault ride-through (FRT) is a common requirement to abide by grid code all over the world. In this paper, to enhance the FRT capability of fixed speed wind generator system, a modified configuration of bridge-type fault current limiter (BFCL) is proposed. To check the effectiveness of the proposed BFCL, its performance is compared with that of the series dynamic braking resistor (SDBR). A harmonic performance improvement by the proposed method is also analyzed. A three-phase-to-ground (3LG) fault was applied to one of the double circuit transmission lines connected to the wind generator system. Simulation was carried out by using MATLAB/Simulink software. Simulation results show that the proposed BFCL is a very effective device to achieve the FRT and suppress fault current that eliminates the need for circuit breaker replacement. Also, the BFCL improves the harmonic performance and helps follow harmonic grid code. Moreover, it was found that the BFCL works better than the SDBR and has some distinct advantages over the SDBR.
60 citations
TL;DR: In this paper, a field discharge circuit was proposed to limit the generator's fault current, thus leading to a synchronous-machine DG with little impact on distribution system protection, and the results demonstrate that the proposed field discharge circuits are sufficient to prevent miscoordination of the feeder protections when short time-delay and/or inverse-time overcurrent relays are involved in the protection scheme.
Abstract: Synchronous-machine DGs are well known to cause miscoordination of distribution system protections because of the generator's ability to contribute large fault currents to the fault. This paper proposes a field discharge circuit to limit the generator's fault current, thus leading to a synchronous-machine DG with little impact on distribution system protection. In this paper, the operation of a solid-state switch-based field discharge circuit is studied, and its effects on the generator's output current during the fault are investigated. It is shown that the proposed scheme removes the steady-state component of the fault current and accelerates the decay of the transient ac component of the current. The results demonstrate that the proposed field discharge circuit is sufficient to prevent miscoordination of the feeder protections when short time-delay and/or inverse-time overcurrent relays are involved in the protection scheme.
60 citations
TL;DR: The active saturated iron-core superconducting fault current limiter (SISFCL) is one of the best solutions to coping with high fault current levels and may be helpful in building future smart distribution networks.
Abstract: The active saturated iron-core superconducting fault current limiter (SISFCL) is one of the best solutions to coping with high fault current levels and may be helpful in building future smart distribution networks. The application of an SISFCL in a distribution system can reduce the fault current to an acceptable level when a short-circuit fault occurs at different positions. The operational principle and the current-limiting characteristic of an active SISFCL are briefly introduced in this paper. The influence of an active SISFCL on the conventional inverse and definite time-delay overcurrent protective relays is discussed. In order to maintain reliable operation of the distribution system with an SISFCL, the protection coordination and setting solution is proposed. A model of a real 35-kV distribution system with an active SISFCL was built and simulated with the Electro-Magnetic Transients Program including DC software. Simulation tests have demonstrated the correctness and validity of theoretical analyses.
60 citations
TL;DR: A new technique for detecting turn-to-turn short-circuit faults in one or two stator phases of an induction motor using the extracted features from the corresponding three-phase current pattern in 3-D space, capable of detecting a phase- to-ground fault.
Abstract: The main objective of this paper is to develop a new technique for detecting turn-to-turn short-circuit faults in one or two stator phases of an induction motor. Hence, modeling a turn-to-turn short-circuit fault in more than one phase and a phase-to-ground fault is the first novelty of this paper for calculating phase currents under faulty conditions. This strategy uses the extracted features from the corresponding three-phase current pattern in 3-D space. Identification of faulty phases and of the severity of the fault is the outcome of this technique. This technique is also capable of detecting a phase-to-ground fault. This method just requires current sensors that are available in most drive systems to provide good controllability, and details of the machine design are not necessary. Experimental results are included to show the ability of the proposed strategy for detecting and locating phase/phases under different faults and load conditions.
TL;DR: Two fault tolerant current control strategies for a nine-phase flux-switching permanent magnet (FSPM) machine are proposed and implemented when one or two phases meet the open-circuit fault.
Abstract: The fault tolerant capability of electrical machine-based driving systems is extremely important in many applications. Hence, in this paper, two fault tolerant current control strategies for a nine-phase flux-switching permanent magnet (FSPM) machine are proposed and implemented when one or two phases meet the open-circuit fault. The basic concepts of the two control strategies are to keep the rotating magnetomotive force unchanged under both healthy and faulty conditions. Based on the principle, an optimal solution is derived through comparing the magnitudes of fault tolerant currents, average output torque, and torque ripple. The finite element analysis-based predictions of the nine-phase FSPM machine verify the effectiveness and difference of the two fault tolerant control strategies.
TL;DR: In this paper, the authors proposed a new approach to fault location for double-circuit transmission lines based on only the voltage data of both ends of the faulted circuit, where the ratio between the magnitudes of negative-sequence voltages measured at both ends is utilized to estimate the fault location.
Abstract: This paper describes a new approach to fault location for double-circuit transmission lines based on only the voltage data of both ends of the faulted circuit. The ratio between the magnitudes of negative-sequence voltages measured at both ends of the faulted circuit is utilized to estimate the fault location. Since only the magnitudes are used, the data of both ends are not required to be synchronized, which removes any concern about data synchronization. Moreover, since only the voltage data are required, the errors caused by current transformers can be avoided. The proposed method can effectively locate the single-phase-to-ground, double-phase-to-ground, and phase-to-phase faults disregarding the fault resistance and prefault conditions and without any need for fault classification and phase selection. Unlike the iterative methods, the proposed method is fully analytical and does not cause much computing burden to the line relays. The accuracy and practicality of the proposed method make it an attractive function to implement in numerical relays.
TL;DR: In this paper, an improved phase-locked loop (IPLL) is used to extract the fifth harmonic zero-sequence currents in this study and fifth harmonic current characteristics are employed to select the fault line.
Abstract: Fault line detection timely and accurately when single-phase-to-earth fault occurs in neutral point ineffectively grounding power system is still a focus of research. To perfect these existing detection methods and enhance their accuracy, an improved phase-locked loop (IPLL) is used to extract the fifth harmonic zero-sequence currents in this study and fifth harmonic current characteristics are employed to select the fault line. Through relative processing, the fifth harmonic data differences of all lines are more noticeable, which is better for fault line detection. The line-detection function of IPLL is shown based on Matlab/Simulink. Simulation result reveals the good performance of this proposed method in effectively fault line detection. This method is able to detect different types of grounding faults in power system. This study gives a new train of thought for fault line detection.
14 Apr 2014
TL;DR: The German AmpaCity project as discussed by the authors is the first one kilometer superconducting (HTS) cable system to be installed in a real grid application within a city center area.
Abstract: In this paper the German AmpaCity project, which started in September 2011, will be introduced and the conceptual design of the main components will be described. The objective of the project is developing, manufacturing and installing a 10 kV, 40 MVA high temperature superconducting (HTS) system consisting of a fault current limiter and of a 1 km cable in the city of Essen. AmpaCity serves as a lighthouse project, since it is the first time that a one kilometer HTS cable system will be installed together with an HTS fault current limiter in a real grid application within a city center area. In addition it will be the longest installed HTS cable system worldwide. Within the project the development phase was finished in March 2013 with successfully completing the type test of the cable system. Subsequently, manufacturing of the different components for the installation has started and the system is expected to be commissioned by the end of 2013.
01 Oct 2014
TL;DR: In this paper, a fault location method and a fault clearance strategy for medium voltage dc (MVDC) distribution system are presented, where a communication link between O/C relays is used to diagnose the fault location and the fault clearance is done by the operation of dc circuit breakers and isolator switches.
Abstract: A fault location method and a fault clearance strategy are presented in this paper for medium voltage dc (MVDC) distribution system. MVDC systems are applicable for connection between microgrids (MGs) and integration of renewable energy systems (RESs) to distribution systems. Due to the specifications of fault current in dc systems, it is difficult to coordinate the over current (O/C) relays based on the time inverse grading. Hence, in this paper, a communication link between O/C relays is used to diagnose the fault location. On the other hand, the fault clearance is done by the operation of dc circuit breakers (DCCB) and isolator switches. In this protection strategy, O/C relays detect the faulty part using communication links and after the fault extinguishing by DCCBs, the dc switches isolate the faulty part. Finally, the sound parts of the system re-energize when DCCB are re-closed. Moreover, data transmission by communication links is based on the standard messages of IEC61850 protocol.
TL;DR: In this article, the design, set-up and short-circuit testing of an air coil superconducting fault current limiter demonstrator is discussed. But the main limitation of the air coil limiter is that the secondary winding can generate a resistance and significantly increase the impedance of the limiter.
Abstract: This paper discusses the design, set-up and short-circuit testing of an air coil superconducting fault current limiter demonstrator. The demonstrator was specified for 60 kVA, 400 V, z = 6%. It consists of a primary winding made of copper, which is basically the equivalent of an air core reactor and a secondary superconducting winding made of commercially available (RE)BCO tapes, which are individually short-circuited. Both windings are inductively coupled and intended to work in liquid nitrogen. The measurements results show significantly lower impedance during normal operation compared to the air core reactor. If a fault current occurs the induced current in the secondary winding quenches the superconducting tapes, which generates a resistance and significantly increasing the impedance of the limiter. The built demonstrator achieves a current limiting capability of up to 40% for fault currents 17 times higher than the nominal current. The demonstrator proves the concept of the air coil superconducting fault current limiter and verifies the underlying design method.
TL;DR: In this paper, a sensor fault diagnosis method of Support Vector Machine (SVM) is presented based on the control system model of superconducting fault current limiter (SFCL) with saturated iron core.
Abstract: To improve reliability, a sensor fault diagnosis method of Support Vector Machine (SVM) is presented based on the control system model of superconducting fault current limiter (SFCL) with saturated iron core. It is used for the state estimation of the bias current of the excitation system. In this paper, the SVM is used to approximate the nonlinear function between ac voltage, ac current of SFCL, ac impedance of SFCL, and dc bias current. It is equivalent to an inverse model to estimate the dc bias current from the ac voltage, ac current, and ac impedance. If the error between estimated value of dc bias current and the sample value of current sensor is beyond some threshold value, it shows a fault occurs on the current sensor. Through simulations, this kind of sensor fault diagnosis method based on SVM is proved to be effective.
TL;DR: In this paper, a controllable resistive type fault current limiter (CR-FCL) is introduced, which inserts a pre-specified value of resistance based on a predefined function, by using a simple switching method, in series with the fault current path.
TL;DR: In this article, the authors propose a fault current classification technique that replaces the conventional directional element during problematic conditions and provides accurate fault direction quickly based on waveshape properties of the current.
Abstract: Distributed generation (DG) integration necessitates upgrading some distribution system overcurrent relays to directional ones to offer selective protection. The directional feature is conventionally achieved by phase angle comparison between phasors of the fault current and a polarizing quantity, normally a voltage signal. Doubly fed induction generator (DFIG)-based wind turbines constitute an appreciable portion of today’s DG power. This paper unveils that conventional directional elements malfunction during three-phase short-circuits when a distribution system incorporates DFIG-based wind DG. The maloperation is due to the exclusive fault behavior of DFIGs, which affects the existing relaying practices. The paper also proposes a fault current classification technique that replaces the conventional directional element during problematic conditions and provides accurate fault direction quickly based on waveshape properties of the current. An extensive performance evaluation using PSCAD/EMTDC simulation of the IEEE 34 bus system corroborates the effectiveness of the proposed method. Results are exceptionally encouraging in the case of resistive crowbar circuits for DFIGs, which is the typical scenario in practice.
TL;DR: In this paper, a multiagent-based fault-current limiting scheme for micro-grids is presented, where a typical microgrid is divided into several sections, and the fault condition is identified by analyzing the information of FLIUs in the network.
Abstract: Penetration of distributed generations (DGs) are becoming more widespread in the current electric power networks. One of the most important issues regarding utilization of DG in power systems is related to their impact on fault-current level. In this regard, a multiagent-based fault-current limiting scheme for microgrids is presented in this paper. A typical microgrid is divided into several sections. A number of superconducting fault-current limiters, which are located in suitable locations of the network, can suppress transient fault currents. Fault location is identified using several fault-location identification units (FLIUs), which are installed in suitable places. In each FLIU, fault current is estimated using a Kalman filter and then the residual signal is generated from the calculated and measured fault current. In the fault condition, the faulty section is identified by analyzing the information of FLIUs in the network. Then, the impact of the faulty section on the sound sections is minimized by utilizing the proposed fault-current limiting scheme. Capabilities of the proposed method are evaluated using different simulations on a benchmark microgrid.
TL;DR: In this article, the optimal location of a resistive superconducting fault current limiter (SFCL) to improve the transient stability of an electric power grid (EPG) was determined using the angular separation of the rotors of synchronous machines present in the power system.
TL;DR: In this article, the authors presented a novel protection criterion of fault locating in multi-terminal DC transmission systems. But the traditional protection cannot locate the fault because there is no smoothing reactor (equipped at the converter output) in the transmission lines.
Abstract: This study presents a novel protection criterion of fault locating in multi-terminal DC (MTDC) transmission systems. When a fault occurs on the DC transmission line of the MTDC system, the traditional protection cannot locate the fault because there is no smoothing reactor (equipped at the converter output) in the transmission lines. In the circumstance of AC/DC conductor contact (ADCC) fault, the varieties of the transient voltage and current components are given based on the symmetrical fault analysis. According to the Bergeron equation, the travelling wave characteristic is analysed. A new criterion of fault locating using the change rate of the current travelling wave is presented which can reduce the impacts of the related fault on the AC system. Finally, simulation results verify the effectiveness of the proposed protection criterion.
15 Jun 2014
TL;DR: In this article, a diagnostic method for identifying an external short circuit (ESC) fault for a lithium-ion battery is developed based upon active characterization experiments and online validation The proposed method examines three criteria: voltage variation, current variation and temperature change rate.
Abstract: In this paper, a diagnostic method for identifying an external short circuit (ESC) fault for a lithium-ion battery is developed based upon active characterization experiments and online validation The proposed method examines three criteria: voltage variation, current variation and temperature change rate These criteria can be used to identify the fault independent of the battery state of charge (SoC) when an ESC fault occurs Experimental results are presented to validate the feasibility of the proposed diagnostic method
TL;DR: The simulation results show that the active SFCL can play an obvious role in restraining the fault current and overvoltage, and it can contribute to avoiding damage on the relevant distribution equipment and improve the systems safety and reliability.
Abstract: For a power distribution system with distributed generation (DG) units, its fault current and induced overvoltage under abnormal conditions should be taken into account seriously. In consideration that applying superconducting fault current limiter (SFCL) may be a feasible solution, in this paper, the effects of a voltage compensation type active SFCL on them are studied through theoretical derivation and simulation. The active SFCL is composed of an air-core superconducting transformer and a PWM converter. The magnetic field in the air-core can be controlled by adjusting the converters output current, and then the active SFCLs equivalent impedance can be regulated for current-limitation and possible overvoltage suppression. During the study process, in view of the changes in the locations of the DG units connected to the system, the DG units injection capacities and the fault positions, the active SFCLs current-limiting and overvoltage-suppressing characteristics are both simulated in MATLAB. The simulation results show that the active SFCL can play an obvious role in restraining the fault current and overvoltage, and it can contribute to avoiding damage on the relevant distribution equipment and improve the systems safety and reliability.
TL;DR: In this article, a bridge-type fault current limiter (BFCL) is proposed to moderate transient overcurrent in abrupt load change condition and dramatically limit the fault current in fault condition.
Abstract: A new high-performance bridge-type fault current limiter (BFCL) is proposed in this study. The proposed BFCL can moderate transient overcurrent in abrupt load change condition and dramatically limit the fault current in fault condition. The key feature of this new BFCL is based on using a switched transformer-type DC reactor. In fact, the secondary side of the transformer is short-circuited during normal condition. Therefore, the transformer has negligible effect on the circuit in this condition. When the load current exceeds a predefined threshold (permissible maximum load current), secondary side of the transformer is opened by an insulated gate bipolar transistor. Consequently, inrush current of the load suppresses in abrupt load change condition or the current increases at a constant rate in fault condition. When current exceeds a higher predefined threshold (in the order of fault current), it is limited via the switched DC reactor and a discharging resistor. Analytical analysis of the proposed BFCL is presented in detail. Simulation and experimental results validate the effectiveness of this structure in abrupt load change and fault conditions.
01 Jan 2014
TL;DR: In this paper, the authors present a survey about Fault Ride Through (FRT) techniques and controllers which are employed with all wind generation system types, and propose three FRT controllers for keeping stability of fixed speed wind generation (FSWG) system serving in isolated micro-grid (MG).
Abstract: This paper presents survey about Fault Ride Through (FRT) techniques and controllers which employed with all wind generation system types. After presenting a comprehensive FRT survey, paper proposes three Fault Ride Through (FRT) controllers for keeping stability of Fixed Speed Wind Generation (FSWG) system serving in isolated Micro-Grid (MG). The first controller has been implemented by inserting Superconductor Fault Current Limiter (SFCL) in series with wind generator terminals during fault instant. The second proposed FRT controller is modifying the conventional Pitch Angle Controllers (PAC) to can spill and reduce high percentage of extracted mechanical wind power during and subsequent fault occurrence which in turns help stability improvement and restoration. Third FRT technique is performed by adapting the wind turbine gearbox ratio which forces the wind generation system to run far from the maximum power point. The best performance is obtained with the SFCL controller. Superior results are obtained when the three proposed FRT controllers are employed simultaneously. The three developed FRT controllers are simple, reliable and economical attractive. Effects of fault type on SFCL FRT controller performance are analyzed and investigated in details. The proposed SFCL FRT controller has been tested under single phase, double phase, phase to phase, and three phases to ground faults. Results display that the three phases to ground fault is the most severe type on SFCL FRT performance from stability point of view. On the other hand, double phase to ground fault is the most severe one from fluctuations and oscillations points of view. Parameters of the SFCL must be adjusted based on the three phases to ground fault. If the SFCL FRT controller is designed to can deal with three phases fault, it sure can deal with the other fault types successfully.
TL;DR: In this article, the authors proposed a new method of ground fault phase selection for high-voltage/extra-highvoltage transmission-line protection under weak-infeed conditions.
Abstract: The sequence current-based fault phase selector and traditional low-voltage fault phase selector have difficulties in being applied to the weak-infeed side. This study proposes a new method of ground fault phase selection for high-voltage/extra-high-voltage transmission-line protection under weak-infeed conditions. The method utilizes the relative phase-angle relationship between negative- and zero-sequence voltages and a relative phase relationship between superimposed positive-sequence voltage and superimposed negative-sequence voltage to identify the fault phase under weak-infeed conditions. Theory analysis and simulation have proven that the proposed method has high immunity against fault resistance as well as impedance phase-angle inequality and overload.
TL;DR: In this article, a fast solid state DC breaker design method is proposed based on the fault current characteristics of the inverter in multi-terminal HVDC systems (MTDC), where a fault current appears at the natural zero-crossing point near the inverters.
Abstract: The DC fault characteristics of voltage source converter based high voltage direct current (VSC-HVDC) systems are analyzed in this paper. The phenomenon whereby the capacitor on DC side discharges quickly during a DC fault contributes to a large short-circuit fault current. Neither traditional DC breakers nor DC switches can cut off the fault current under this condition. A fast solid state DC breaker design method is proposed in this paper. This method is based on the fault current characteristics of the inverter in multi-terminal HVDC systems (MTDC), where a fault current appears at the natural zero-crossing point near the inverter. At this point, by coordinating the AC breakers near the rectifier, the DC breaker could reliably cut off the DC fault current and protect the system. A detailed model for this fast solid state DC breaker and its operation sequence are studied, based on this design method. Simulations modeling a five-terminal meshed DC grid and a fast DC breaker were carried out with PSCAD/EMTDC using this design method. The results from the simulations confirmed the validity of the design method.