Saturated Iron-core Fault Current Limiter 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 Novel Saturated Amorphous Alloy Core Based Fault Current Limiter for Improving the Low Voltage Ride Through Capability of Doubly-Fed Induction Generator Based Wind Turbines

This article proposes the use of a novel saturated amorphous alloy core-based fault current limiter (SAACFCL) to improve the low voltage ride through (LVRT) capability of doubly-fed induction generator (DFIG) based wind energy systems, especially during voltage sag events. Compared to the traditional cores, which are widely used in fault current limiter (FCL), amorphous alloy core possesses a very narrow B-H loop, which indicates that the SAACFCL requires a smaller dc excitation current, and it will incur low core losses. Under normal conditions, this developed SAACFCL accomplishes low impedance and has a negligible impact on the network operation. During grid faults, a deep voltage sag causes large fault currents that desaturate the SAACFCL core, increasing its impedance, which limits the fault currents and improves the LVRT capability of DFIG systems. The SAACFCL is designed and characterized by ANSYS software. To validate the performance of the SAACFCL, a DFIG-based system equipped with the SAACFCL has been modeled in MATLAB/Simulink. The simulation results with and without the SAACFCL show that the SAACFCL is capable to achieve the LVRT successfully and can meet the grid code requirement. The performance of the SAACFCL has also been compared with that of the saturated iron core FCL (SICFCL) and superconducting FCL (SFCL). The SAACFCL promises better performances than SICFCL and SFCL. A small scale SAACFCL has been designed, developed, and tested in the laboratory to check its performance. The experimental results show that the proposed SAACFCL can effectively reduce the level of fault current and mitigate voltage sag experienced by the DFIG.

Method to design saturated iron‐core fault current limiters

Fault current limiter (FCL) is a kind of device with current-dependent impedance that has low impedance in normal state of power system, and high impedance during fault condition. Among all classes of FCLs, the saturated iron-core FCL (SICFCL) is practically the most favourable one nowadays. In this study, a numerical method for design and cost optimisation of SICFCLs is presented. It uses a set of constraints to ensure the desirable operation of the SICFCL based on its electrical and magnetic characteristics. For numerical calculations and optimisations, GAMS software has been used. Suitability of the method is approved by design, simulation and test of a 3500 VA prototype. Magnetic field distributions are simulated using COMSOL Multiphysics and performance of the designed SICFCL is evaluated in a power system hardware model. Simulation and experimental results show the satisfying agreement with predicted results by the proposed numerical method.

Current-limiting characteristics of saturated iron-core fault current limiters in VSC-HVDC systems based on electromagnetic energy conversion mechanism

A common method to examine the current-limiting performance of saturated iron-core fault current limiter (SI-FCL) in high-voltage direct-current transmission based on voltage source converter (VSC-HVDC) systems is to solve differential equations based on the system fault transient characteristics and the equivalent inductance calculation equation. This method analyzes the fault current of the VSC-HVDC system in the time domain. However, it is computationally complex and cannot directly reflect the relationship between parameters and the current-limiting effect of the SI-FCL. In this paper, the relationship between the magnetic flux density and magnetic field energy of the SI-FCL is analyzed. The energy exchange between the DC capacitor and the SI-FCL in the DC short circuit fault process is analyzed. From the perspective of electromagnetic energy conversion, the criterion for determining the current-limiting ability of the SI-FCL in the transient process is given based on the parameters of the SI-FCL and VSC-HVDC system. On this basis, the characteristics of the DC side fault current and the capacitor voltage when the SI-FCL has current-limiting ability are examined. Based on the parameters of the SI-FCL and VSC-HVDC system, a method for calculating the fault current peak value and capacitor voltage drop time is given. Finally, the accuracy of the analysis of the SI-FCL in the VSC-HVDC system based on the electromagnetic energy conversion mechanism is demonstrated through a case study and simulation results of the VSC-HVDC system with different SI-FCLs.

Electromagnetic Design of High-Temperature Superconducting DC Bias Winding for Single-Phase 500 kV Saturated Iron-Core Fault Current Limiter

The dc bias winding of a single-phase 500 kV saturated iron-core fault current limiter is presented. The winding is mainly made of Bi-2223 tape, and some YBCO tape is used to optimize the magnetic field distribution. By using YBCO winding, maximal radial component of the magnet flux density on top of Bi-2223 winding is reduced from 0.29 to 0.22 T. Therefore, the corresponding maximum operation current of Bi-2223 could increase more than 20%. Since the critical current of YBCO and Bi-2223 winding is different, two power supplies are used to excite the windings, where the prospected operation current of YBCO and Bi-2223 winding is 160 and 1045 A, and the corresponding magnetomotive force is 468 000. In order to satisfy the operation condition, the winding must be cooled by liquid nitrogen at 72 K. The experimental results of the developed winding at 77 K show that the operation parameter is consistent with the electromagnetic designed.

Safety Considerations in the Design, Fabrication, Testing, and Operation of the DC Bias Coil of a Saturated Iron-Core Superconducting Fault Current Limiter

The function of the superconducting bias coil in a saturated iron-core fault current limiter is to magnetize the iron cores. For practical utility devices of HV power grids, the rated capacity is usually 100 MVA or higher. The size and weight of the iron cores of a saturated iron-core fault current limiter with such capacity is quite large, so the bias coil needs to have high magnetization capacity and consequently a large diameter. The stability and safety of the bias coil are of critical importance for the reliability required by power utilities. Experience taught us that great care must be taken in the design, fabrication, testing, and grid operation to avoid potentially fatal risks. In this paper, we will discuss and analyze the possible safety hazards for a large size superconducting bias coil, which may result in mechanical failure and electrical impact, causing significant damage to the coil. Possible causes of the hazards are improper configuration, mismatch of component materials during thermal cycling, manufacturing failures in fabrication, lack of protection in testing and operation, etc. We will also report measures we took to eliminate or reduce these safety hazards.

DC Magnetization System for a 35 kV/90 MVA Superconducting Saturated Iron-Core Fault Current Limiter

A dc magnetization system, comprises a HTS dc bias coil, a current source, a high-speed switch, and an energy release circuit, was built for a 35 kV/90 MVA saturated iron-core fault current limiter to enhance its functional capability and reliability and to reduce its size and weight. The dc bias coil is made of high temperature superconducting silver sheathed Bi-2223 tapes with a magnetization capacity of 141,000 ampere ldr turns. The current source is able to supply a maximum of 350 A constant current. The energy release circuit was designed to quickly discharge the magnetic energy of the saturated iron cores and to suppress the voltage surge across the dc coil when the magnetization circuit was switched to open in a short-circuit event. This controllable magnetization system enables the fault current limiter to respond to a short-circuit fault in one millisecond, to reach full current limiting function in 5 milliseconds, and to re-saturate the iron cores in 800 milliseconds after the clearance of a fault. In this paper, we introduce the configuration and specifications of the system. Some experimental results are also reported.

HTS dc bias coil for 35 kV/90 MVA saturated iron-core fault current limiter

A superconductive coil with 141,000 ampere-turns designed magnetizing power, made of 17,600 meters of BSCCO 2223 HTS tapes, was fabricated and tested. This coil was built for a 35 kV/90 MVA saturated iron-core fault current limiter. Computer simulations on the performance of the coil were carried out using ANSYS. The critical current of the superconducting coil and the dc resistance of the coil, including the non-superconducting joints, were investigated. Spatial distribution of the magnetic field was measured and compared with the simulation results. In this paper, we will report the configuration and the key parameters of the coil as well as the experimental and simulation results.

The adaptation of magnetic support to air-driven ultracentrifuges.

A superconductive coil with 141,000 ampere-turns designed magnetizing power, made of 17,600 meters of BSCCO 2223 HTS tapes, was fabricated and tested. This coil was built for a 35 kV/90 MVA saturated iron-core fault current limiter. Computer simulations on the performance of the coil were carried out using ANSYS. The critical current of the superconducting coil and the dc resistance of the coil, including the non-superconducting joints, were investigated. Spatial distribution of the magnetic field was measured and compared with the simulation results. In this paper, we will report the configuration and the key parameters of the coil as well as the experimental and simulation results.