T. Janowski

Design and Tests of Coreless Inductive Superconducting Fault Current Limiter

In this work, we report on the design and tests results of a coreless inductive SFCL with a 600 A rated current for MV distribution system. The fault current limiter comprises of 4 identical units immersed in liquid nitrogen bath. Each unit consists of 3 windings. The primary and secondary windings made of 2G HTS tape SF12050 are magnetically coupled with the primary Cu winding. The high magnetic coupling between superconducting primary and secondary windings gives a low voltage drop on the limiter at nominal current. The presented solution reduces the size and the weight of the device. Tests performed at high power test facility prove the limiting capability of the coreless inductive SFCL.

Comparison of Inductive and Resistive SFCL

This article presents a comparison of inductive and resistive superconducting fault current limiter built with the same length of high temperature superconducting (HTS) tape. The resistive limiter is constructed as a noninductive bifilar winding. The inductive coreless limiter consists of primary winding and secondary shorted winding. Both limiters are connected parallel to the additional Cu primary winding, which helps to reduce the power dissipated in the HTS windings during and after a fault. It also ensures that in cases of an HTS tape failure, the protected circuit will not be disrupted. The limiters are very fast and the first peak is almost equally limited by both types of limiters.

Tests and Performance Analysis of Coreless Inductive HTS Fault Current Limiters

Superconducting fault current limiters (SFCL) are designed to protect the electrical grid from faults that result from lightning strikes, downed power lines and other system interruptions. The rapid increase of impedance of the SFCL reduces the short current in the circuit. Several coreless constructions of inductive SFCLs have been tested. The space between the windings is the thick of the polyimide film kapton insulation to increase the coupling and reduces the leakage reactance. Both primary and secondary windings have been immersed in liquid nitrogen. The presented solutions reduce the size and the weight of the device. A few limiters based on HTS 1G and HTS 2G tapes has been described, tested and compared.

Analysis of Transformer Type Superconducting Fault Current Limiters

The inductive type SFCLs and the transformer type SFCLs need the iron cores. In both, the fault current is transformed from the primary winding to the secondary winding. The difference is in the secondary windings. The superconducting materials for every kind of SFCL should have both high value of resistivity in the resistive state,rhotau , and high critical current density . The paper shows, that the transformer SFCL can be made using every type of commercial HTS elements. The inductive SFCLs need the HTS materials with very large value of the rhotauJc parameter.

Experimental and Numerical Analysis of Electrothermal and Mechanical Phenomena in HTS Tube of Inductive SFCL

The superconducting fault current limiter (SFCL) can be successfully used to limit the short-circuit current level in electrical networks to 5 (or less) times of rated current level. The inductive SFCL works like transformer with shorted secondary winding in a shape of HTS tube. The SFCL 625-A consists of superconducting Bi-2223 tube (critical current=625 A at 77 K), iron core and copper primary winding. The numerical model using the thermal physical domain of CAD package FLUX2D has been used to analyze of temperature distribution in HTS tube during the fault. The numerical model using the magnetodynamic physical domain of FLUX2D package was used to analyze the mechanical force in HTS tube during fault. We attempt to provide explanation why HTS tubes quite often break during current limitation

The 15 kV Class Inductive SFCL

The Superconducting Fault Current Limiter (SFCL) is one of the most attractive devices for the electrical power network. The inductive SFCL consists of two coaxial windings and an optional magnetic core. The primary winding, connected in series to the circuit, is conventionally made of the copper wire, the secondary is made of a superconductor. The 15 kV class SFCL has been designed. It consists of 7 units. The primary copper winding of units has 27 turns/unit and the operating current is 1 kA. The HTS winding of units is wound with 140 turns of YBCO coated conductor SF12050 tape (SuperPower Inc.). The HTS winding has an internal diameter of 0.455 m. The SFCL is cooled in the liquid nitrogen bath. In this paper, we have described the numerical model and the numerically calculated electric parameters of the 15 kV class inductive type SFCL in the stand-by state and during current limitation.

Bi-2223 and Bi-2212 tubes for small fault current limiters

The superconducting fault current limiters (SFCL) can be used to limit the short-circuit current level in electrical transmission and distribution networks. In one concept of SFCL-serial resistive limiter, the superconductor is inserted in the circuit directly. During a fault, the fault current pushes the superconductor into a resistive state and resistance, which limits the fault current, appears in the circuit. Another concept-inductive limiter works like transformer with shorted superconducting secondary winding. The impedance of this limiter under standard operation conditions is nearly zero, since the zero impedance of the secondary superconducting winding is reflected to the primary. In the event of a fault, the resistance in the secondary winding is reflected into the circuit and limits the fault current. The small inductive type SFCLs with Bi-2223 tubes with critical current=112 A, 625 A, and 1210 A (at 77 K and self-magnetic field) and various numbers of primary winding turns are presented with their limitation coefficients. The resistive type SFCL based on Bi-2212 tube with critical current=125 A (at 77 K and self-magnetic field) is presented too.

Analysis of Alternating Overcurrent Response of 2G HTS Tape for SFCL

The scope of this article was to find the transient response of the 2G high-temperature superconducting (HTS) tape under alternating overcurrent. The authors performed a series of measurements for the SF12050 HTS tape produced by SuperPower Inc. The tape was fed by a 50-Hz ac voltage source with adjustable amplitude. The temporal dependences of the tape current and voltage drops in each test segment were recorded simultaneously. The measurements were performed for the current amplitudes exceeding the critical value specified by the manufacturer ( Ic = 270 A @77 K, self-field). The instantaneous values of the tape temperature during overcurrent transient period were also determined. Additionally, the numerical analysis of the SF12050 tape was performed. A numerical model was built using PSPICE environment. The model assumes the nonlinear dependence of tape parameters in the function of temperature, as well as the variable cooling conditions during transient state. The constructed model was verified with measurement results.

Superconducting Winding for Inductive Type SFCL Made of HTS Tape With Increased Resistivity

Currently produced and available HTS tapes with increased resistivity, like 2nd generation YBCO 344S tape made by American Superconductors, have enough parameters, e.g., resistivity, critical current density, to build inductive type current limiters to limit faults in medium-voltage power grid. The paper describes the assumption for 6,9 kV/1.15 kA superconducting fault current limiter with superconducting secondary winding made of high resistivity HTS tape as well as the results of numerical analysis.

Experimental Investigation of a Model of a Transformer-Type Superconducting Fault Current Limiter With a Superconducting Coil Made of a 2G HTS Tape

A superconducting fault current limiter (SFCL) reduces the short-circuit current level in a power system and thus provides protection for and significantly reduces the wear and tear of circuit breakers and other substation power equipment. This paper describes a design and test results of a model of a transformer-type superconducting fault current limiter (TrSFCL) with a 1-phase 10 kV copper transformer and a secondary winding shorted by a superconducting current limiting coil made of 2G HTS tape. Special regard is given to the ability of this device to limit a short-circuit current thanks to the parameters of both the HTS coil and the 2G HTS tape used, and in particular to its resistivity in the resistive state at a temperature of 77 K.