Fault Current Limiters

This 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.

In this paper a variable and controllable resistor
type fault current limiter (FCL) is introduced for enhancement of
transient stability of single machine infinite bus (SMIB) system
with a double circuit transmission line. The optimal value of
resistor during fault to reach the maximum stability of power
system is computed. It is shown that, this optimal value depends
on the fault location and the pre-fault active power of
synchronous generator considering power demand changing. To
show the effectiveness of the proposed FCL, analytical analysis
including transient stability study and optimum resistor value
calculation are presented. In addition, simulation results using
PSCAD /EMTDC software are included to confirm the analytical
analysis accuracy.

In this paper, power quality improvement by using a new structure of non superconducting fault current limiter (NSFCL) is discussed. This structure prevents voltage sags on Point of Common Coupling (PCC) just after fault occurrence, because of its fast operation. On the other hand, previously used structures produce harmonics on load voltage and have ac losses in normal operation. New structure has solved this problem by using dc voltage source. The proposed structure is simulated using PSCAD/EMTDC software and ...

In this paper, voltage sag compensation of point of common coupling (PCC) using a new structure of fault current limiter (FCL) is proposed. The proposed structure prevents voltage sag and phase-angle jump of the substation PCC after fault occurrence. This structure has a simple control method. Using the semiconductor switch (insulated-gate bipolar transistor or gate turnoff thyristor at dc current rout leads to fast operation of the proposed FCL and, consequently, dc reactor value is reduced. On the other hand, the ...

Smart grid is an advancement of the existing electrical grid. The key feature of the future smart grid is the decentralization of the main power grid into number of smaller grids (known as micro grids). Interconnection of the distributed generating (DG) sources is required with the existing electrical grid to enhance the reliability of the power system. Extensive integration of DG sources within a smart grid causes failure of a successful implementation of smart grid due to the presence of enormous fault current. Superconducting Fault Current Limiter (SFCL) has the capability to reduce the fault current level within the first cycle of the fault current resulting in an increased transient stability of the power system. In this paper an application of a resistive type SFCL, designed in Simulink / SimPower System has been proposed to limit the fault current that occurs in an interconnected power system. A resistive type SFCL model has been developed in Simulink and the performance of SFCL at different locations has been analysed in the proposed system considering wind farm (10 MVA) as a distributed generating (DG) source with the conventional power plant, to reduce the fault current in micro grids. The feasible location of the SFCL having no negative effect on the DG source has been evaluated in three phase and single line to ground faults at various positions in the smart grid. Index Terms-conventional power plant, wind farm, micro grid, smart grid, superconducting fault current limiter, fault current.

In this paper, enhancement of transient stability of
Single Machine Infinite Bus (SMIB) system with a double circuit
transmission line using a Non-superconducting Fault Current
Limiter (NSFCL) is proposed. Stability analysis for such system
is discussed in detail. It is shown that, the stability depends on the
resistance of NSFCL in fault condition. To effective improvement
of stability, the optimum value of NSFCL resistance is calculated.
Simulation results by PSCAD/EMTDC software are presented to
confirm the analytic analysis accuracy.

This paper proposes a new parallel LC resonance type
Fault Current Limiter (FCL). This structure has low cast because
of using dry capacitor and non-superconducting inductor and
fast operation. The proposed FCL is able to limit fault current in
constant value near to pre-fault condition value against series
resonance type FCL. In this way, the voltage of point of common
coupling (PCC) will not change during fault. Analytical analysis
is presented in detail and simulation results are involved to
validate the effectiveness of this structure.

Fault current magnitude and transient recovery voltage (TRV) are two important factors effecting circuit breaker (CB) operation during short-line faults. In this paper an inductive fault current limiter (FCL), which is a traditional kind of FCL, is modeled and simulated using electromagnetic transient program (EMTP) to study its effects on these two factors. It is assumed that the FCL is placed following the circuit breaker at the beginning of the line. Mathematical formulas are obtained for describing the relationship between the current limit factor and the recovery voltage of a CB as well as the rate of rise of recovery voltage (RRRV) based on theoretical analysis. The mathematical analysis is compared and verified with simulation results.

the demand for electricity is increasing rapidly and demand for power is running ahead of supply. The short-circuit capacity increases with the growth of interconnections in electrical systems. .The system parameters such as voltage and current are analysed during normal operating conditions and also during various fault conditions. The fault current limiter can be effectively used to limit the increase in over current during the fault condition. A Fault Current Limiter (FCL) is a revolutionary power grid device that limits the problems due to increase in fault current levels. It reduces prospective fault currents to a lower manageable level. The Super conducting Fault Current Limiter (SFCL) is one of the promising technologies to unravel fault current problem, because of its effective fault current limiting and quick recovery characteristic. The microgrid system with distributed generation during a three phase fault condition were simulated with and without SFCL in MATLAB/SIMULINK environment.

In this paper, power quality improvement by using a
new structure of non superconducting fault current limiter
(NSFCL) is discussed. This structure prevents voltage sags on
Point of Common Coupling (PCC) just after fault occurrence,
because of its fast operation. On the other hand, previously used
structures produce harmonics on load voltage and have ac losses
in normal operation. New structure has solved this problem by
using dc voltage source. The proposed structure is simulated
using PSCAD/EMTDC software and simulation results are
presented to validate the effectiveness of this structure.

The consumption increase, generating capacities
and electric grid development in Moscow region and especially on Moscow-City territory in short-term and long-term perspective will lead to the short circuit current increase to ultrahigh values which exceed the disconnection capability of the serial equipment. The present article covers the issues of short circuit current limitation in megalopolis power system taking Moscow Power System as an example. The issues of consumers’ power supply reliability were considered. The foreign experience of short circuit current limitation in megalopolis was analyzed.
The system approach for solving this problem was proposed. The future recommendations for energy companies were developed.

Power system is getting complex due to a boost in the number of new power plants and the expansion of the transmission system in order to meet the growing for electricity. This scenario results in a large number of short circuits in the system, which may exceed the rating of existing circuit breakers (CBs) and may severely destroy system equipment. Installing fault current limiters (FCLs) into the power system is one of the most cost-effective ways to degrade fault current levels. This paper presents a method to specify the optimal numbers and locations for FCLs placement in terms of installing the smallest FCL parameters to restrain short-circuit currents below the interrupting currents of circuit breakers, to minimize transmission loss. Due to a lack of genetic, PSO and other optimization algorithms, an Elitist Gravitational Search Algorithm (EGSA) for more accurate and better results is used. This algorithm is employed to search for the location and parameter of FCLs to meet the specific requirements. The proposed method is applied to the IEEE 30-bus test system. Simulation results indicated the adequacy and precision of the proposed method.

Employing Resistive Superconducting Fault Current Limiters (RSFCL) is one of the practical and effective methods to improve the transient stability of a power system by limiting the fault current. Regarding technical and economical constraints, optimal sizing and allocation of RSFCLs in a power system is of significant importance. It is the purpose of this paper to propose an algorithm based on the Particle Swarm Optimization (PSO) in order to improve the transient stability of a power system by optimal sizing and allocation of RSFCLs. The proposed algorithm is next applied to the New England 39-bus test system as a case study and the results are simulated in Matlab. Simulation results reveal that in the case of employing RSFCLs with sizes and locations resulted from the optimization algorithm, the transient stability of the power system under study is improved. Furthermore, it seems that the optimal locations of RSFCLs are to some extent near the fault location. KEYWORDS Transient Stability Improvement, Resistive Superconducting Fault Current Limiters (RSFCL), Particle Swarm Optimization (PSO)

The distribution network has many advantages when it is connected to distributed generation (DG). Some
problems in coordination of protection devices will occur in the presence of DG, due to change in short
circuit level at different points. Fault current limiter (FCL) is applying limit to the fault current levels and
the effect of DGs on coordination of overcurrent (O/C) relay during the faults. In distribution network the
use of FCL & DG causes some transient current during fault condition. In such network steady state
coordination method do not result inaccurately. In this method we use fault current limiter for reducing the
transient fault current in the network. The method gives feasible and effective solutions for optimal
coordination in the practical power system networks in comparison to the previous steady state methods
when simulations are carried out on a sample network and the results are demonstrated.

With the short circuit level increase in power grids, there is a need to increase rating of switch type fault current limiters (STFCLs), therefore, modularization of STFCLs is inevitable. This paper presents a comparative reliability analysis between the modular and non-modular STFCL topologies. It is demonstrated that modular design causes a considerable reduction in reliability. The aim of the presented study is to increase the reliability of modular fault current limiters using thermal management. The failure rate of STFCL module and junction temperature calculation is developed. The mean time to failure (MTTF) is used as the reliability metric. MTTFs of two topologies are calculated and compared. It is demonstrated that reliability of STFCL depends on the junction temperature of the semiconductor switches in the steady state, that it can be controlled by the thermal resistance of the heat sink. Ranges of the junction temperature and thermal resistance in which the modular configuration is more reliable are formulated. Then numerical studies are presented to verify the efficacy of the proposed approach.

Designs of saturated-cores fault current limiters (FCLs) usually implement conducting or superconducting DC coils serving to saturate the magnetic cores during nominal grid performance. The use of coils adds significantly to the operational cost of the system, consuming energy, and requiring maintenance. A derivative of the saturated-cores FCL is a design implementing permanent magnets as an alternative to the DC coils, eliminating practically all maintenance due to its entirely passive components. There are, however, various challenges such as the need to reach deep saturation with the currently available permanent magnets as well as the complications involved in the assembly process due to very powerful magnetic forces between the magnets and the cores. This paper presents several concepts, achieved by extensive magnetic simulations and verified experimentally, that help in maximizing the core saturation of the PMFCL (Permanent Magnet FCL), including optimization of the permanent magnet to core surface ratios and asymmetrical placement of the permanent magnets, both creating an increase in the cores' magnetic flux at crucial points. In addition, we point to the importance of splitting the AC coils to leave the center core point exposed to best utilize their variable inductance parameters. This paper also describes the stages of design and assembly of a laboratory-scale single phase prototype model with the proposed PMFCL design recommendations, as well as an analysis of real-time results obtained while connecting this prototype to a 220 V grid during nominal and fault states.

In this paper, voltage sag compensation of point of common coupling (PCC) using a new structure of fault current limiter (FCL) is proposed. The proposed structure prevents voltage sag and phase-angle jump of the substation PCC after fault occurrence. This structure has a simple control method. Using the semiconductor switch (insulated-gate bipolar transistor or gate turnoff thyristor at dc current rout leads to fast operation of the proposed FCL and, consequently, dc reactor value is reduced. On the other hand, the proposed structure reduces the total harmonic distortion on load voltage and it has low ac losses in normal operation. As a result, other feeders, which are connected to the substation PCC, will have good power quality. Analytical analysis and simulation results using PSCAD/EMTDC software and experimental results are presented to validate the effectiveness of this structure.

This paper proposes a new parallel-LC-resonance type
fault current limiter (FCL) that uses a resistor in series with
a capacitor. The proposed FCL is capable of limiting the fault
current magnitude near to the prefault magnitude of distribution feeder current by placing the mentioned resistor in the structure of the FCL. In this way, the voltage of the point of common coupling does not experience considerable sag during the fault.
In addition, the proposed FCL does not use a superconducting
inductor which has high construction cost. Analytical analysis for this structure is presented in detail, and simulation results using power system computer-aided design/electromagnetic transients, including dc software are obtained to validate the effectiveness of this structure. Also, an experimental setup is provided to show the accuracy of the analytic analyses and simulation results.

Distributed Generation Resources are increasingly used in distribution systems due to their great advantages. The presence of DG, however, can cause various problems such as miss-coordination, false tripping, blinding and reduction of reach of protective devices. Using superconducting fault current limiters (SFCLs) is one of the best methods to minimize these problems comparing to the other conventional methods. The active SFCL can as well suppress the short-circuit current induced by a three-phase grounded fault effectively, and the power system's safety and reliability can be improved and it 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 over voltages suppressing characteristics are presented In extension the proposed concept can be implemented for over voltages and over currents in wind energy system by using Matlab/simulink software.

Doubly-fed induction generator (DFIG)-based wind turbines utilise small-scale voltage sourced converters with a limited overcurrent withstand capability, which makes the DFIG-based wind turbines very vulnerable to grid faults. Often, modern DFIG systems employ a crowbar protection at the rotor circuit to protect the rotor side converter (RSC) during grid faults. This method converts the DFIG to a squirrel cage induction generator, which does not comply with the new grid codes. The recent grid codes need wind turbines to stay connected to the utility grid during and after power system faults, especially in high penetration level of wind power. Furthermore, the crowbar switch is expensive. This paper proposes a novel DC-link switchable resistive-type fault current limiter (SRFCL) to improve the LVRT capability of the DFIG. The proposed SRFCL is employed in the DC side of the RSC. The SRFCL solves crowbar protection activation problems and eliminates subsequent complications in the DFIG system. The proposed SRFCL does not have any significant impact on the overall performance of the DFIG during normal operation. Whenever the fault, whether symmetrical or asymmetrical, occurs, the SRFCL not only limits rotor over-currents but also prevents rotor speed acceleration and restricts high torque oscillations even during zero grid voltage, as recommended by some grid codes. To prove the effective operation of the SRFCL on the RSC fault current limitation, analytical analysis is performed in each switching interval. The proposed approach is compared with the crowbar-based protection method. Simulation studies are carried out in PSCAD/EMTDC software. In addition, a prototype is provided to demonstrate the main concept of the proposed approach.

Smart grid is an advancement of the existing electrical grid. The key feature of the future smart grid is the decentralization of the main power grid into number of smaller grids (known as micro grids). Interconnection of the distributed generating (DG) sources is required with the existing electrical grid to enhance the reliability of the power system. Extensive integration of DG sources within a smart grid causes failure of a successful implementation of smart grid due to the presence of enormous fault current. Superconducting Fault Current Limiter (SFCL) has the capability to reduce the fault current level within the first cycle of the fault current resulting in an increased transient stability of the power system. In this paper an application of a resistive type SFCL, designed in Simulink / SimPower System has been proposed to limit the fault current that occurs in an interconnected power system. A resistive type SFCL model has been developed in Simulink and the performance of S...

In this paper, transient stability improvement using bridge type fault current limiter (FCL) is presented in single machine infinite bus (SMIB) system with a double circuit transmission line. Three single-phase sets of the proposed FCL are installed at the beginning of feeder. The proposed FCL inserts an inductance and a resistance in the fault current pass. The insertion inductance and resistance not only limits the fault current level in an acceptable value but also improves transient stability of power system by consuming ...

This paper proposes an optimum resistive type fault current limiter (OR-FCL) as an efficient solution to achieve maximum fault ride-through (FRT) capability of fixed-speed wind turbines (FSWT) during various grid faults. In this paper, a dedicated control circuit is designed for the OR-FCL that enables it to insert an optimum value of resistance in the FSWT's fault current's path for improving transient behavior of the FSWT. The optimum resistance value depends on fault location and prefault active power. The control circuit of the proposed OR-FCL is capable of calculating the optimum resistance value for all the prefault conditions. By using the proposed control circuit, the FSWT can achieve its maximum FRT capability during symmetrical and asymmetrical faults, even at zero grid voltage. Analysis is provided in detail to highlight the process of calculating the optimum resistance of the OR-FCL. Moreover, the effect of the resistance value of the OR-FCL on the FRT behavior of FSWT is investigated. To show the efficiency of the proposed OR-FCL, its performance during various operation conditions of the FSWT is studied. It can be proved that each operation condition needs its own optimum resistance value, which can be obtained by using the proposed control circuit during the fault to achieve the maximum FRT capability of the FSWT. Comprehensive sets of simulations are carried out in PSCAD/EMTDC software and the results prove the effectiveness of the proposed approach.

In this paper, a non-controlled fault current limiter (FCL) is proposed to improve fault ride through capability of doubly fed induction generator (DFIG)-based wind turbine. Cooperative operation of chopper circuit and the non-controlled FCL, which is located in rotor side of the DFIG, is studied. It is demonstrated that locating the proposed topology in the rotor side is effective from leakage coefficient point of view in limiting transient over currents rather than stator side. Furthermore, it is shown that, by obtaining optimum non-superconducting reactor value, rate of fault current change is limited to lower than maximum rate of current change in semiconductor switches of the DFIG's converters during fault. Design methodology of non-superconducting reactor value is investigated. Operation of the non-controlled FCL in the rotor side is compared to crowbar protection scheme and results will be discussed. PSCAD/EMTDC software is employed to simulate the proposed scheme and prove its effectiveness.

Designs of saturated-cores fault current limiters (FCLs) usually implement conducting or superconducting DC coils serving to saturate the magnetic cores during nominal grid performance. The use of coils adds significantly to the operational cost of the system, consuming energy, and requiring maintenance. A derivative of the saturated-cores FCL is a design implementing permanent magnets as an alternative to the DC coils, eliminating practically all maintenance due to its entirely passive components. There are, however, various challenges such as the need to reach deep saturation with the currently available permanent magnets as well as the complications involved in the assembly process due to very powerful magnetic forces between the magnets and the cores. This paper presents several concepts, achieved by extensive magnetic simulations and verified experimentally, that help in maximizing the core saturation of the PMFCL (Permanent Magnet FCL), including optimization of the permanent ...

In this paper, voltage sag compensation of point of common coupling (PCC) using a new structure of fault current limiter (FCL) is proposed. The proposed structure prevents voltage sag and phase-angle jump of the substation PCC after fault occurrence. This structure has a simple control method. Using the semiconductor switch (insulated-gate bipolar transistor or gate turnoff thyristor at dc current rout leads to fast operation of the proposed FCL and, consequently, dc reactor value is reduced. On the other hand, the ...

This paper proposes a controllable resistive type fault current limiter (CR-FCL) with its modified control strategy to improve fault ride-through capability (FRT) of fixed speed wind turbine (FSWT). Investigated system includes squirrel cage induction generator, the CR-FCL, and the FSWT connected to infinite bus through double-circuit transmission line. The CR-FCL is located in beginning of the parallel line. The proposed structure with its modified control method inserts an optimum value of resistance during fault to achieve maximum FRT capability. It will be shown that this optimum value depends on fault location and pre-fault active power. Two different wind speeds will be applied to the investigated system, which cause two various output powers. Then, it will be proved that each condition needs its own optimum resistance during the fault to achieve the maximum FRT capability of the FSWT. PSCAD/EMTDC is utilised to show accuracy of the proposed scheme and analytical analysis.

Abstract In this paper, enhancement of transient stability of Single Machine Infinite Bus (SMIB) system with a double circuit transmission line using a Non-superconducting Fault Current Limiter (NSFCL) is proposed. Stability analysis for such system is discussed in detail. It is shown that, the stability depends on the resistance of NSFCL in fault condition. To effective improvement of stability, the optimum value of NSFCL resistance is calculated. Simulation results by PSCAD/EMTDC software are presented to confirm the analytic ...

Directional overcurrent relays are used in this paper for relay coordination process. Here we consider operational characteristics, pickup current and time multiplier settings as the parameter of relays. The approach is used to figure out overcurrent relay coordination bearing distributed energy resource (DER) in a distributed system. The impingement of DER in a power distributed system varies the protection design of the system. So on implementing fault current limiter (FCL) alleviates the DER fault current and restores the archetypical relay coordination. The methodology of selecting FCL resistive type, inductive type, impedance type and its minimum value is illustrated and real power losses are minimized. The following pros and cons of all three types of FCL are also mentioned in this paper. Three scenarios are discussed: no DER, the implementation of DER with FCL and without FCL. Simulations are carried for single DER placement and fault location. The application is implemented on a simple radial distribution system. The results are reported and discussed.

In this paper, transient stability improvement using bridge
type fault current limiter (FCL) is presented in single
machine infinite bus (SMIB) system with a double circuit
transmission line. Three single-phase sets of the proposed
FCL are installed at the beginning of feeder. The proposed
FCL inserts an inductance and a resistance in the fault
current pass. The insertion inductance and resistance not
only limits the fault current level in an acceptable value but
also improves transient stability of power system by
consuming excessive energy of synchronous generator
during fault. To reach maximum transient stability, the
optimal resistor value of the proposed FCL is calculated.
Analytical analysis and simulation results using
PSCAD/EMTDC software are presented to show the
current limiting future and transient stability enhancement
using the proposed FCL in SMIB.