Non-superconducting Fault Current Limiter

The application of flat superconductor rings has been investigated in the structure of inductive shieldtype high temperature superconducting fault current limiters, HT c-SFCL. A laboratory scale inductive shield-type HT c-SFCL has been designed and fabricated using flat superconductor rings. The fabrication process has been fully presented. YBCO powder has been used for the fabrication of superconductor rings. This fabrication process, being quite innovative, is introduced completely. The method of the trapped field measurement has been used for the critical current density measurement of the fabricated superconductor rings. The device with nominal current of 2 A was tested in a 30 V circuit. The SFCL successfully limited the fault currents of up to 10 times the nominal current to an approximately fixed value of 3 A. The voltage-current characteristic of the fabricated prototype has also been obtained and has shown compatibility with the fault current limitation results.

All electric equipment in a power system has to be designed to withstand the mechanical and thermal stresses of potential short-circuit currents. Any reduction of these currents can lead to significant cost savings. Among all current limiting devices, superconducting fault current ...

This paper proposes a new topology for fault current limiter (FCL) that is based on series LC resonance circuit. The proposed FCL uses a high speed switch to put an inductor in series with a capacitor and make resonance condition between them. This structure can hold the peak of fault current in the constant value that is not possible in previously introduced series resonance type FCLs. In such conditions, if fault continues, power system will not be experience large short circuit currents. Using non-superconducting inductor instead of superconducting one, leads to low construction and maintenance costs in this structure. In addition, in normal operation, capacitor of this FCL can be used as a series compensator. Analytical analysis for the proposed series resonance type FCL is performed in detail. Simulations are presented using PSCAD/EMTDC software to show the operation of the proposed FCL. Also, comparison between the proposed FCL and previous series resonance type FCLs is included in simulations.

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.

High temperature superconductivity (HTS, discovered in 1986) remains an active area of research worldwide, because its higher T c and, thus, more economical cryogenic cooling have raised the prospects for electric power application. The discovery of MgB 2 has rekindled the search for new superconductors with higher T c . Recently, various acceleration programs have been launched in Europe, USA and Japan. The advance in HTS conductor has enabled the demonstration of various application prototypes, including, power cables, transformers, motors, and fault current limiters. However, full commercialisation of HTS application critically relies on the realisation of HTS conductors that are reliable, robust and low cost with low AC-losses. Worldwide activities are, therefore, focused on developing processing technologies to fabricate the so-called coated conductor based on YBCO to fulfil the stringent specifications. While a high critical current density of around 5 MA/cm 2 (77 K) has been achieved, the conductor cost is currently estimated to be 10-50 times higher than what would be accepted. #

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, a diode-bridge-type nonsuperconductor fault current limiter (NSFCL) is proposed. The structure has the capability of controlling the dc reactor current that yields to control the magnitude of fault current. In order to control the magnitude of dc reactor current, a discharging resistor is used in the proposed structure. By controlling the magnitude of dc reactor current, it is possible to reduce the current rating and inductance of dc reactor. In addition, a series connection of dc voltage source with dc reactor is used to compensate the power loss of both nonsuperconducting dc reactor and diodes of fault current limiters (FCLs). By means of proposed NSFCL, it is possible to eliminate all disconnecting switches in the distribution network. The simulation and experimental results are presented to clarify the theory and possibility of implementation of the proposed NSFCL.

Design, parameters, and application areas of a superconducting fault current limiter (FCL) are analyzed on the basis of the requirements of power systems. The comparison of resistive and inductive designs is carried out. An example of the effective application of FCLs in distribution substations is considered and the gain from the FCL installation is discussed. It is shown that an FCL not only limits a fault current but also increases the dynamic stability of the synchronous operation of electric machines. The calculation procedure of the parameters of an inductive FCL for a specific application case is described.

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 ...

The development of superconducting systems for electric power is driven by the promise of improved efficiency, smaller size, and reduced weight as compared to existing technologies and by the possibility of new applications. Superconducting power components can also contribute to improved power quality and increased system reliability. This paper addresses historical developments and technology status of four superconducting power applications: cables, superconducting magnetic energy storage (SMES), fault-current limiters, and transformers. Today, SMES is the only fully functional superconducting system and it has seen only limited use at grid power levels. A few model or demonstration units exist for each of the other three applications. Superconductivity faces several hurdles on the path to widespread use. Perhaps the most important is the need for operating voltages of 100 kV or more. Though progress in this and other areas has been rapid, considerable development is needed before superconducting devices perform reliably in the utility environment. As a result, today, most initial installations are aimed at niche applications and will be installed where space is limited, where power demands are increasing over existing corridors, and/or where initial development costs can be offset by enhanced power grid performance.

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 achieves several centimeters. 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 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, the cylinders are needed with the critical current density by an order higher than the existed ones.

Doubly fed induction machine (DFIM) based wind generators are vulnerable to the grid faults, as their stator windings are directly connected to the grid. Besides the symmetrical faults, asymmetrical faults are also problematic to DFIM, as asymmetrical faults put turbine generator system into high electromechanical stress leading to instability and mechanical damage. There are also requirements to abide by grid

The saturated cores FCL exhibits several attractive technological advantages: Inherent fail-safe and selectivity design, superconductivity is maintained during both nominal and fault states, the limiting process as well as the recovery after fault are passive and immediate, operation in limiting state is not time-limited, and the superconducting bias coil is made of wires available as commercial shelf-product. Despite these advantages, saturated cores FCL did not make it to commercial phase because of the large volume and heavy weight associated with its realization, a coupling problem between the AC and bias coils while in limiting state, and non-optimal limitation resulting from the presence of the bias field during fault. This work presents a novel, improved saturated cores FCL concept that overcomes the above difficulties and reopens the possibility for commercialization. Unique design topography reduces the cores volume and at the same time reduces the AC and DC magnetic coupling to about 2%. In addition, a control circuit, triggered by voltage drop across the FCL terminals, is added and disconnects the bias coil during a fault for increased limiting performances. All above-mentioned advantages of the saturated cores concept are maintained in this new design. First, a 4.2 kVA laboratory scale FCL has been designed built and studied proving the feasibility of the new design. Then, an up-scaled, 120 kVA model has been designed, built and tested at the testing laboratory of the Israel Electric Company. The prospective short current in the test bed was 5000 A, successfully limited to 2400 A. The 120 kVA model is a single phase FCL designed for 400 V, 300 A nominal conditions. Core losses and AC coils losses are 0.09% and 0.18%, respectively.

The growth of the generation of electrical energy and the increased interconnection of networks lead to higher fault current levels. The short circuit current will impose high dynamical and thermal stresses on electrical equipments. All equipments have to have a short circuit rating capable of withstanding this level.

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 ...

The penetration of DG systems in distribution systems can result in the increase of the short circuit current level. The application of the fault current limiter (FCL) would not only decrease the stress on network devices, but also can offer a connection to improve the reliability of the power system. There are various types of FCLs, which are made of different superconducting materials and have different designs. There are several kinds of SFCLs, which can be classified in three types such as the resistive type, the inductive type and bridge type SFCL. In this paper, the transient recovery voltage (TRV) analysis, based on the electromagnetic transient program (EMTP), is used to investigate the behavior of the each three types SFCL installed in an electrical distribution grid. Simulation results show that the TRV can be damped in the presence of the resistive and bridge type SFCL during fault clearing period.

An important aspect of wind power plant (WPP) impact studies is to evaluate the short-circuit current (SCC) contribution of the plant into the transmission network under different fault conditions. This task can be challenging to protection engineers due to the topology differences between different types of wind turbine generators (WTGs) and the conventional generating units.

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.

Este artigo apresenta uma metodologia para auxiliar nos estudos de limitação de correntes de curto-circuito em sistemas elétricos com problemas de superação de disjuntores, através da alocação ótima de dispositivos limitadores. O problema de otimização é solucionado aplicando-se Algoritmos Genéticos e levando em consideração os requisitos de custo mínimo, alocação de um número mínimo de dispositivos e a máxima redução da corrente de curto-circuito. A detecção da superação do disjuntor é feita pela análise tanto da corrente de curtocircuito que o disjuntor deve interromper como também da relação X/R do sistema. O modelo computacional desenvolvido utiliza de modo integrado o programa ANAFAS do CEPEL, mantendo a compatibilidade com as bases de dados utilizadas em estudos de curto-circuito no setor elétrico brasileiro. Os resultados obtidos com o sistema IEEE14 e com um sistema real brasileiro de grande porte comprovam a robustez do modelo, apresentando soluções que satisfazem às restrições com custo de investimento reduzido para todos os cenários analisados.

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.

A bifilar Bi-2212 bulk coil with parallel shunt resistor was tested under fault current condition using a 3 MVA singlephase transformer in a 220 V-60 Hz line achieving fault current peak of 8 kA. The fault current tests are performed from steady state peak current of 200 A by applying controlled short circuits up to 8 kA varying the time period from one to six cycles. The test results show the function of the shunt resistor providing homogeneous quench behavior of the HTS coil besides its intrinsic stabilizing role. The limiting current ratio achieves a factor 4.2 during 5 cycles without any degradation. Index Terms-Bi-2212 bulk coil, HTS bifilar coil, HTS coils, superconducting fault current limiter.

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 grid-connected power electronic inverters are highly sensitive to grid disturbances and it is important to emphasize the necessity to reduce the effects of voltage disturbances on their operation. Among the wide range of power quality disturbances, voltage sags severely affect the performance of voltage source converters (VSC) operation of distributed generation (DG) units. In this paper, small signal model of photovoltaic, DC-DC boost converter and inverter are simulated in Matlab simulink software. The photovoltaic system is connected to a 20kV distribution feeder via a transformer. It can be seen if the voltage sag is happened in the system, the inverter switch current will be increased significantly. In order to protect the power electronic converters' switches during a voltage sag and increase the voltage sag ride through capability, use of fault current limiter (FCL), is proposed. It is shown that if the voltage sag happened with duration of half to thirty cycles, FCL limits the current of power electronic switches. So, the photovoltaic system although is kept connecting with grid during the voltage sag condition, the power electronic switches aren't harmed and have normal current during voltage sag duration.

With the advent of high power high voltage IGBTs, it is feasible to use sophisticated gate drive circuits to obtain improved switching performance and ruggedness. Short-circuit and over-current fault protections are critical issues in gate drive circuits for high power converters. This paper evaluates the effect of gate control to limit the fault current in an IGBT in terms of its internal dynamics. The internal dynamics are analyzed using a two-dimensional device simulator. The effects of short-circuit and over-current faults in an IGBT power converter are studied by examining the fault characteristics over a range of fault inductance values. This study highlights the advantages of reduced fault current level, reduced power dissipation, and improved ruggedness that can be gained by the fault current limiting gate protection techniques. The simulation studies match trends observed in experimental results

We found well operational property of superconducting fault current limiter (SFCL) substituting variable reactor to dc link of the rectifier type SFCL without bias current source. We proposed double bridge configuration with mutual coupled dc inductor to implement variable reactor. In the hybrid bridge circuit of the SFCL, two superconducting coils: a trigger coil and a limiting coil connected in anti-parallel mode. Both the coils are magnetically coupled with each other and could have the same value of self inductance so that they can share the line current equally. In this paper, we describe the SFCL model in the PSCAS / EMTDC○ R simulator for three phase bus and three phase voltage source.

Besides critical current and conductor length, thermal stability, mechanical properties and ac loss characteristics of second-generation (2G) HTS wire are very important performance parameters to electric power device applications. Each application sets specific technical requirements on conductors. The properties of the practical 2G HTS wire manufactured at SuperPower, Inc. have enabled satisfactory performance in a number of demonstration devices including cable, high-field magnetic coil and fault current limiter. Yet, effort is being made to develop new conductor structures and configurations toward further enhanced performance in order to extend the potential of 2G HTS wire over a wider application range. This paper describes a variety of newly developed configurations: striation, narrow width, low-resistance joints and high quality insulation. The performance of wire with new configurations will promote the wide use of 2G HTS wire.

Simulations of a resonance event were performed based on actual field data of a commercially operating distribution feeder and a superconducting saturable core fault current limiter. The analysis was conducted from both the system's and the fault current limiter's perspectives. Agreement in the results of the two approaches showed that under certain values of reactive shunt compensation, full insertion of the limiter's reactance, and low load conditions, a sustained but damped resonance can occur. Resonance suppression preventive measures for these conditions are proposed.

This paper presents an improved simulated annealing (SA) algorithm for multiobjective optimization, which is a positive approach in the design of high-temperature superconducting (HTS) fault-current limiters (SFCLs). The main goal of this paper is to achieve an effective and feasible approach in the structural design of HTS FCLs by means of multiobjective decision-making techniques, based on normalized SA. The combination of electrical and thermal models of a purpose-designed resistive-type HTS FCL is defined as a component in PSCAD/EMTDC simulations from which the proposed method will be used to optimize the selective parameters of the SFCL. The above requires the need of advanced numerical techniques for simulation studies by PSCAD on a sample distribution system for determining a global optimum HTS FCL, by considering individual parameters and accounting for the constraints, which is the main motivation for initiating this paper.

Current injection transformer (CIT) systems are within the major group of the standard type test of high current equipment in the electrical industry, so their performance becomes very important. When designing high current systems, there are many factors to be considered from which their overcurrent protection must be ensured. The output of a CIT is wholly dependent on the impedance of the equipment under test (EUT). Therefore current flow beyond the allowable limit can occur. The present state of the art provides an important guide to developing current limiters not only for the grid application but also in industrial equipment.

The prototype of a fault current limiter (FCL) based on Bi 1.8 Pb 0.3 Sr 1.9 Ca 2 Cu 3 O x high temperature superconductor (HTSC) was tested on switch-on/switch-off processes in the short circuit regime. The switch-off processes may result in voltage and current jumps, accompanied by energy dissipation large enough to destroy the FCL. Experimental results, together with numerical simulations for switch-off processes are presented and discussed.

Absfract-AC losses in hollow BSCCO cylinders used in an inductive fault current limiter model have been investigated theoretically and experimentally. Discrepancies, becoming more pronounced with increasing current, between the experimental results and predictions of Bean's critical state model were observed. A simple procedure of calculating AC losses by taking into account the real form of the E J characteristics was proposed. AC loss characteristics were employed to evaluate the nominal and activation currents of the full-scale 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.

The penetration of DG systems in distribution systems can result in the increase of the short circuit current level. The application of the fault current limiter (FCL) would not only decrease the stress on network devices, but also can offer a connection to improve the reliability of the power system. There are various types of FCLs, which are made of different superconducting materials and have different designs. There are several kinds of SFCLs, which can be classified in three types such as the resistive type, the inductive type and bridge type SFCL. In this paper, the transient recovery voltage (TRV) analysis, based on the electromagnetic transient program (EMTP), is used to investigate the behavior of the each three types SFCL installed in an electrical distribution grid. Simulation results show that the TRV can be damped in the presence of the resistive and bridge type SFCL during fault clearing period.

Due to its simple structure and lower price, the resistive type superconducting fault current limiter (RSFCL) is being used widely in practical experiences. Since these equipments are installed to provide high levels of power quality for sensitive consumers, it is necessary to investigate their harmonics generation. In this paper harmonics generation of a RSFCL is considered and a method is presented for harmonics reduction.

A rectifier type superconducting fault current limiter with noninductive reactor has been proposed by the authors. The concept behind this SFCL is that the high impedance generated during superconducting to normal state of the trigger coil limits the fault current. In the hybrid bridge circuit of the SFCL, two superconducting coils: a trigger coil and a limiting coil are connected in anti-parallel. Both the coils are magnetically coupled with each other and could have the same value of self inductance so that they can share the line current equally. At fault time when the trigger coil current reaches a certain level, the trigger coil changes from superconducting state to normal state. This super to normal transition of the trigger coil changes the current ratio of the coils and therefore the flux inside the reactor is no longer zero. So, the equivalent impedance of both the coils is increased and limits the fault current. We have carried out computer simulation using PSCAD/EMTDC and observed the results. Both the simulation and preliminary experiment shows good results. The advantage of using hybrid bridge circuit is that the SFCL can also be used as circuit breaker.