Fault Current Limiter Devices Research Articles

A review of superconducting fault current limiters compared with other proven technologies

• Fault Current Limiters Technologies. • Advantages and disadvantages of FCL technologies. • Commercial FCL Devices review. Several substations in operation were commissioned decades ago. These substations are overstressed, then their protection equipment cannot provide an effective safety condition to the system. In the worst cases, short-circuits can cause permanent damage to the system if the overcurrent is higher than the capacity of the installed equipment. There are some possible solutions for those cases: replace all the equipment in the overstressed substation, build a new one in parallel or install a fault current limiter (FCL) device. From an economic point of view, introducing FCLs in the power system is the best way to solve the described problem. The commercial solutions available are the pyrotechnic FCL, air coil reactor, neutral earthing resistor, and high impedance transformer. However, these devices are limited and present several drawbacks. Since the ’70s, there has been a search for reliable FCL devices that do not interfere in the regular operation of substations and could limit the fault currents to the protection system rated level. There were so many FCL technologies proposed in the last decades. These proposed new devices may use superconducting technologies, power electronics, or both. This paper reviews proven FCL technologies, focusing on full-scale devices demonstrated in field and lab tests. The goal is to introduce the main FCL technologies in development and discuss didactically their operation principle, the built prototypes, the commercial units, whether they exist, and the main drawbacks for each technology presented. A final analysis of the level of maturity for each FCL technology is discussed using the TRL (Technology readiness level) scale in order to find technologies with more potential for mass production. The three technologies closer to the full commercial application are: the Resistive Superconducting FCL, the Saturated Iron Core FCL, and the Series Reactor FCL.

A coordinated relay protection strategy of distribution network based on fault current limiting

In order to solve the problem of difficult coordination of traditional overcurrent relay protection caused by short supply radius and little difference of fault current along urban distribution network, a coordinated relay protection strategy based on economical fault current limiter (FCL) is proposed. The FCL device is configured at the export of the main transformer, by using quick fault identification method, setting different protection current value and relay protection delay time, once the fault occurs, the FCL can quickly limit the fault current first then cooperate with the circuit break and switches on the feeder line to achieved the coordinated relay protection. Combining with faults occurring at different locations along the feeder line, the composition and basic working principle of the FCL are discussed, the theory of fast fault identification method and the setting method of the coordinated relay protection parameters are emphatically discussed. The simulation results show that the proposed current limiting coordinated relay protection strategy can effectively reduce the short-circuit current level and bus voltage drop during the fault handle processing, thus reduce the damage to the distribution system and influence range of the fault, greatly improve the selectivity of the relay protection finally.

Tests and recovery under load simulations of a novel bifilar resistive SFCL having undulated shape configuration

Power systems are becoming more interconnected and complex. The distributed generation expands and spreads across the grids, reducing the distance between the load and the generation. In addition, several substations are aging after decades of operation and their equipment struggle to sustain the ever increasing fault levels. In this context, the fault current limiter (FCL) arrived as a solution to mitigate this problem. Considering the FCL devices, the resistive superconducting FCL (R-SFCL) is the most mature technology with potential to be produced in mass scale, due to its ability to quickly change its impedance during a fault current and its high current density capacity. In this paper, a novel R-SFCL topology is presented, which has an unique design that allows a compact size and the possibility of modulated assembly. These characteristics enable setups for various voltage and current levels. One advantage of this topology is the compromise between volume and high heat exchange that can reduce the recovery time under load. One bench prototype was modeled using the thermal–electrical analogy implemented in ATPDraw, tested in two different labs. Tests were performed at faults levels of 12 kA, 5 kA and 2.7 kA for 137 V. Measured and simulated results were compared, resulting in a relative error of less than 12%. Two contributions can be highlighted: the new design of the R-SFCL and the inclusion in the convection heat exchange model curves for the heating (during the quench) and cooling (after fault), which allows to predict the recovery under load.

Neuro Fuzzy Logic Controlled Parallel Resonance Type Fault Current Limiter to Improve the Fault Ride Through Capability of DFIG Based Wind Farm

Doubly fed induction generators (DFIGs) are vulnerable to grid related electrical faults. Standards require DFIGs to be disconnected from the grid unless augmented with a fault ride through (FRT) capability. A fault current limiter (FCL) can enhance the overall stability of wind farms and allow them to maintain grid-code requirements. In this paper, a neuro fuzzy logic controlled parallel resonance type fault current limiter (NFLC-PRFCL) is proposed to enhance the FRT capability of the DFIG based wind farm. Theoretical and graphical analysis of the proposed method are carried out by MATLAB/Simulink software. The performance of the NFLC-PRFCL is compared with other documented FCL devices, e.g., the bridge type fault current limiter (BFCL) and the series dynamic braking resistor (SDBR). The performance of the NFLC-PRFCL is also compared with that of the existing fuzzy logic controlled parallel resonance fault current limiter (FLC-PRFCL). From the simulation results, it is found that the NFLC-PRFCL outperforms its competitors and enables the DFIG to maintain a near-seamless performance during various fault events.

Application of a Resistive Superconducting Fault Current Limiter in a Distribution Grid

This article presents a study on short-circuit current limiting using resistive superconducting fault current limiters, based on a melt cast processed BSCCO-2212. The application of the resistive superconducting fault current limiter was analyzed when installed downstream of a substation, protecting a distribution feeder. The studied power system is based on a dynamic model of the IEEE 13-node test feeder considering a power system expansion scenario, including renewable power generation. As a result of the power system expansion, fault current levels tend to increase, and the resistive superconducting fault current limiter device is used for fault current mitigation. The main contribution of this article is the performance assessment of superconducting fault current limiters and its effects on power quality due to different fault locations in the system and by accounting the complexity of the power system topology. Results obtained demonstrate that the system expansion does not significantly raise fault current levels. It also demonstrated that the resistive superconducting fault current limiter has a desirable operation zone, and unwanted power interruption may occur due to its operation outside this zone.

Mitigation of Voltage Sag using Superconductor Fault Current Limiters

This paper presents a new Fault Current Limiter (FCL) topology based on the superconducting material. This device has the combined advantages of solid state FCL and impedance injecting fault current limiters. As compared the present existing devices, the proposed FCL device generally offers low conduction losses during normal operation while limiting the peak fault current to two times the rated current. Hence, the super conducting fault current limiters is an effective solutions as compared with the other limiters. This system experimentally verified in Matlab/Simulink under different fault conditions and verified the result with and without fault current limiters.

Meshed distribution network vs reinforcement to increase the distributed generation connection

Abstract The expected increase of distributed generation connected to the distribution network will bring many technical constraints. Meshing the network can be a cost effective solution but requires changing the protection scheme that does not suit to a meshed operation. The normally open switches of the network could be replaced by “quick deloopers” based on a fault current limiter device. This system would enable to mesh the network in normal condition and to bring it radial in case of fault so that the standard protection scheme could locate and isolate it. If loops are well selected, the more the network is meshed, the higher the amount of connectable distributed generation without violating technical constraints will be. This paper investigates on the best location to loop the network considering a given target of distributed generation penetration. Several algorithms are proposed to get closer to the optimal solution and tested on a real French network.

Development and Test of a Small Resistive Fault Current Limiting Device Based on a SmBaCuO Ceramic

Since the development of Low Critical Temperature Superconducting (low-Tc) materials, various studies have been published regarding this experimental concept. Recently, researchers have focused on the design and application of high-Tc superconductor (high-Tc) materials to develop fault current limiting circuit breakers. The operation of this circuit requires large prospective/limited current ratios, especially in hazardous areas. In spite of this, several studies describing the Superconducting Fault Current Limiter (SFCL) containing members of the bismuth, mercury or yttrium family cuprate have already been described. However, none of these studies included samarium cuprates. Consequently, we have conducted a study of a small superconducting current limiter device based on SmBa2Cu3O7-d samples. The preliminary results indicated that samarium cuprates could be applied to build superconducting fault current limiter devices. In tests using a polycrystalline sample, the superconducting properties were retained without modifications to its stoichiometry. These results suggest the possibility of future investigations into SFCL devices based on these superconducting ceramics. Keywords: High-Tc, Sm-123, Device, Fault current limiter.

Performance of 2G HTS Tapes in Sub-Cooled LN2 for Superconducting Fault Current Limiting Applications

Within the past few years a newer, more robust type of superconductor known as 2nd Generation High Temperature Superconductor (HTS) wire, has become available in sufficient quantity and lengths for developers to build prototype devices and test their capabilities. This new material offers the potential for revolutionary changes in superconducting transformers and Super conducting Fault Current Limiters to enable better thermal stability and fast quenching capabilities that can meet the stringent demands of large transient faults for distribution and transmission power lines. This manuscript discusses the manufacturing and latest tests and capabilities of sub-cooled superconducting fault current limiter device and modules designed for distribution and trans mission lines. We will also discuss the advantages and superior performance of the new 2nd Generation HTS superconductors under sub-cooled liquid nitrogen operation when used in super conducting fault current limiters. The feasibility demonstration and performance of sub-cooled SFCL superconducting modules for distribution and transmission SFCL devices will be discussed.

Numerical Modeling of the AC Limiting Properties of Insulated, Conduction Cooled ${\hbox {MgB}}_{2}$ Strands

It is known that MgB2-based strands may be used in fault current limiters as a low-cost alternative to high-temperature YBCO coated conductors. Numerical modeling of the ac limiting properties of MgB2 strands with Kapton insulation and conduction cooling have been performed using a finite element method. Two 2D ac Poisson equations, one for calculating the electric field and one for determining the heat transfer were solved simultaneously with input parameters taken from experimental results. As boundary conditions, we took the full non-linear curve of the heat flux into a cryocooler cold head as well as heat radiation from the free surfaces of the wire. The influence of different values and durations of fault electric fields were studied and the maximum temperatures, limiting currents and recovery times were calculated. Obtained results may be useful for understanding the behavior of different kinds of MgB2 multifilamentary wires under conditions encountered in fault current limiter devices.

Power system analysis of a resistive HTS fault current limiter

This paper investigates the performance of a prototype resistive fault current limiter (FCL) made using a high temperature superconductor (HTS). Its behavior under normal operation and short-circuit conditions in a 6 kV/1 kA power system is analyzed with regard to the feasibility of using this HTS FCL device in electrical power systems.

Superconducting fault current limiter device based on (Hg,Re)-1223 superconductor

A preliminary study of a small superconducting current limiter device based on Hg0.8Re0.2Ba2Ca2Cu3O8+δ, (Hg,Re)-1223 ceramic is described. A fault current test at 60Hz confirmed a reduction in the density of current value, from 1.55×102to0.82×102Apeak∕cm2. The prospective/limited density of current ratio observed was ∼1.9 for a 0.24cm thick sample, without any damage to the (Hg,Re)-1223 superconductor. A recovery test indicated that the polycrystalline sample kept its superconducting properties and had not shown modifications in its stoichiometry. In conclusion, (Hg,Re)-1223 can be used to build superconducting fault current limiter devices.

Resistive Fault Current Limiter Prototypes: Mechanical and Electrical Analyses

The problem of excessive short-circuit currents has become an important issue for power systems operators and there are clear indications for a growing interest in superconducting fault current limiter devices for MV and HV grids. In this work, we report on both simulation and electrical testing on single-phase SFCL prototypes developed in the framework of an Italian RTD project to be completed with a 3-phase SFCL unit by the end of 2005.

Rectangular (1 cm ×12 cm) YBCO films prepared by MOD using spin-coating and wire-bar coating

1 cm ×12 cm rectangular YBCO films for fault current limiter devices were prepared by MOD. Usually, solution coating in MOD is carried out by spin coating. However, there are some problems associated with spin coating of large-size rectangular substrates. Namely, the maximum substrate dimension is limited by cup size and motor torque of the apparatus. It was found that wire-bar coating is a promising alternative; this method is more easily scaled up to a large size at lower cost. By both methods, YBCO films with high Jc's around 2 MA/cm2 were obtained on CeO2-buffered sapphire. So far, the uniformity of Jc in the YBCO films prepared by spin coating was better than those by wire-bar coating.

FEM analysis of current limiting devices using superconducting thin film and AC losses of YBCO coated conductor

A numerical analysis tool has been developed to study electromagnetic characteristics of high‐temperature superconducting thin film used for a resistive‐type fault current limiter (FCL) and coated conductor. It adopts the finite element method based on current vector potentials with thin‐plate approximation. Transport current, temperature dependence and strong non‐linearity of electromagnetic properties, and state transition of superconductor are taken into account by solving a three‐dimensional coupled problem of electromagnetic field, an electric circuit and thermal field. Then using this numerical analysis tool the current imbalance and current limiting characteristics of a FCL device, the influence of inhomogeneity of superconducting properties on them, and AC losses in YBCO coated conductor are studied.

Polycrystalline HTS material for bearings and electric power devices

The choice of the material strategies to fabricate bulk high temperature superconductors larger than 10 cm has a significant influence on the performance and reliability of HTS components. The paper considers the various techniques in which magnetic bearings and local current transport devices (current leads and fault current limiters) may be provided: improvement in materials and design. Among bulk growth technique polycrystalline melt textured YBCO rings, rods and plates are a promising concept for the modular up-scaling of current transport and magnetic components if the weak-link behaviour of grain boundaries can be reduced. The fabrication is based on ceramo-crystal growth Bridgman-like directional solidification with an applied spatial and time-dependent thermal gradient on Y 1+ x Ba 2Cu 3O 7− δ ( x=0.30–0.60). Novel superconducting magnetic U-shaped bearings are designed, assembled and tested in a magnetically rotating Si wafer carrier. Rotor dynamics is studied in terms of unbalance and critical rpm's. Fabricating and assembling of current lead components and resistive fault current limiter devices with a transport J c of 5–10 kA/cm 2 at 10 μV/cm and at 77 K are discussed, including a galvanic metal surface deposition technology to contact, protect and stabilize the HTS.

A dc superconducting fault current limiter using die-pressedYBa2Cu3O7 ceramic

A model of a superconducting fault current limiter on apolycrystalline high-temperature superconductor basis is checked in the dcshort circuit regime. Protection of load takes place under the conditionsdescribed in this paper. The use of ceramic materials withsuperconducting-normal metal-superconducting Josephson junction networkhaving an S-type current-voltage characteristic (CVC) is shown to be effectivefor fault current limiter devices.

Design and development of a 15 kV, 20 kA HTS fault current limiter

A 15 kV class high temperature superconducting fault current limiter was developed as part of a Department of Energy Superconductivity Partnership Initiative (SPI) Phase II effort. This is an inductive/electronic fault current limiter (FCL) that can double as a fast sub-cycle solid state breaker. The said device was shipped to Southern California Edison (SCE) Center Substation at Norwalk, CA from General Atomics on June 15, 1999. Preliminary high voltage and high current testing was conducted. The pre-commercial FCL unit houses three of the world's largest Bi-2223 coils (solenoids each with an outside diameter of 1 m and a coil length of 0.75 m), collaborated by GA and IGC. These coils will operate at 35 K and be able to carry a continuous DC current of 2000 A as well as an AC pulsed current of 9000 A. Detailed specification of the FCL device and a brief description of its various subsystems will be given. Finally, test results at Center Substation are summarized and future work outlined. This Phase II FCL device is important as it has the potential to become the first major commercial product for HTS power utility application.

Anomalous behavior of inductive fault current limiter models based on high- Tc superconductors

Inductive fault current limiter device models using sintered or metl-textured YBa 2Cu 3O 7− x rings were tested. An anomalous feature in the primary-current behavior was observed in the presence of melt-textured YBCO rings, consisting of the appearance of instabilities in the form of several peaks in the primary-current signal. The connection of this effect with the form of the voltage-current characteristics and thermal processes in the superconducting ring is discussed.

Powersupply Quality Improvement By Short-circuit Current Limitation On Distribution Nets

Power supply quality improvement is a very real goal for utilities throughout the world because of the expanding diffusion of sensitive (electronic) loads. Among the various types of phenomena affecting voltage quality (i.e., surges, harmonics, spikes, etc.) a great amount of concern is given to the so-called voltage dips or voltage sags. The main source of such a dip or sag is connected with the M.V. distribution line's transient, quasitransient and permanent short circuits. Once a short circuit occurs on a distribution net, a voltage dip appears on all the lines departing from the same bus of the faulted line. Because of this fact, a significant degree of relief from the dip phenomena, or, in other words, a significant improvement in the power-supply quality, can be achieved if the fault current is limited by a proper device (a fault-current limiter (FCL))The design of a FCL device devoted to voltage dip limitation has less stringent requirements, as far as reliability and operation quickness are concerned, than does the design of the equivalent device which has as a target the reduction of the circuit breakers' rated capacity. Very attractive and rather simple solutions are possible using standard, electronically controllable power devices such as thyristors or GTOs. In the present paper, some possible circuits consisting in series-resonant and nonresonant impedance and controlled by static valves are proposed. Computer modelling and simulations of the above circuits and their static and dynamic performances are reported, compared and discussed