Showing papers on "Fault current limiter published in 1992"

The utility requirements for a distribution fault current limiter

Abstract: The need for a distribution current limiting device (DCLD) by the utility industry is addressed. An evaluation was made of what specifications would be acceptable and what DCLD technique would fill the utilities' needs. Using this survey and a distribution system analysis, a DCLD that could limit a 20 kA fault to 10 kA in a 15 kV circuit was shown to be the primary candidate for further development. The study showed that gate turn-off thyristors (GTOs) are the best technology available that could be developed into a practical DCLD. A recommendation was made to develop a DCLD using GTOs. >

Principles of fault current limitation by a resonant LC circuit

Abstract: The reduction of fault current is one of the oldest problems of power systems engineering. Fault current reduction permits the interconnection of large networks without replacing circuit breakers, improves transient stability, and reduces the cost of equipment. The paper investigates the reduction of fault current by the insertion of a resonant LC circuit into the transmission line. The device consists of a capacitor and a thyristor-switched inductance, tuned to the supply frequency. The thyristor switches are operated at zero-current-crossing to eliminate the generation of harmonics. The system operation is analysed using analytic methods and transient simulation techniques. A parametric study determines the effect of components and network parameters on the current limiter operation. Design methods and component selection criteria are developed. The results demonstrate that the device can reduce both transient and steady-state fault current significantly. It can be built with commercially available components. The significant operation improvement is expected to justify the cost of the new device.

6.6 kV/1.5 kA-class superconducting fault current limiter development

Abstract: The authors have developed and tested a 6.6-kV/1.5-kA-class fault current limiter wound with a 42-strand AC superconducting wire having ultrafine NbTi filaments in a high-resistivity matrix. In experiments, voltages up to 7.2 kV were applied to the limiter with phase angles of 0, 45, and 90 degrees . The limiter was able to limit the fault current to 1.8 kA from the 55-kA short-circuit current that would flow in a circuit without a limiter. >

Hybrid superconducting AC fault current limiter principle and previous studies

Abstract: It is pointed out that one of the most promising uses of the low AC loss ultrafine wires in electrical devices is the fault AC current limiter. The superconducting AC current limiters may be separated into two kinds: resistive and inductive ones. For the resistive limiter, the superconducting winding triggers and assumes the limitation. For the inductive one, the superconducting winding plays only the role of trigger while the fault current is limited by another winding, superconducting or normal. In this case, a limited heating of the superconducting coil and then a very short recovery time may be anticipated. It will enable one to quickly restore the service. On the other hand, the current in the trigger coil may be chosen lower than the rated current so that the choice of the superconducting wire may be easier. The use of a judicious magnetic circuit improves the performance of the inductive current limiter as it decreases the voltage drop in rated operation and the heating of the superconducting coil during fault. >

Inrush current limiter in a magnetic flowmeter

Abstract: An AC powered field mounted process control transmitter includes an inrush current limiter which prevents excessive current flow to other circuitry in the transmitter. The transmitter senses a physical parameter, such as flow, and comprises a source of current, a current driven sensing circuitry, the inrush current limiter and measurement electronics for converting the sensed parameter into a transmitter output. The limiter includes a reference voltage source and is in series between the current source and the current driven sensing circuitry. When inactive (i.e. not limiting current), the limiter responds to the series current through itself so that when such current exceeds a predetermined maximum level the limiter becomes active and prevents further current flow. The limiter remains active until the voltage across itself is less than the reference voltage, at which time the limiter becomes inactive.

Superconducting fault current limiter

Abstract: There is disclosed a current limiter having a plurality of current limiting units provided for electric paths constituting a plurality of phases, Each current limiting unit is constituted by a superconducting coil functioning as a first current limiting element formed in a non-inductive winding manner by connecting two superconducting coils in series, which superconducting coils are wound in opposite directions and equal in size and number of turns, and a superconducting coil functioning as a second current limiting element connected in parallel to the first current limiting element and having a predetermined impedance value. These current limiting units are contained within a cryostat and separated by a magnetic shield member for electromagnetically isolating the respective phases.

Single-line-to-ground fault test of a 3-phase superconducting fault current limiting reactor

Abstract: The current limiting behavior of a 3-phase superconducting fault current limiting reactor (SCFCLR) in a model power system at a single-line-to-ground (SLTG) fault is experimentally confirmed. A small arc gap is attached on one phase of the model transmission line. A single-line-to-ground fault is activated. The behavior of the grounding current and the arc is observed. It is shown that: (1) the fault current is limited to a very small value by the large zero-phase-sequence reactance of the SCFCLR, and the self-extinction of the fault arc is observed; (2) the power flow is not disturbed by a SLTG fault at all, and no power system disturbances are observed; and (3) the windings do not quench for a SLTG fault. A supplementary experiment for a two-phase short circuit fault was also carried out. >

Control system for motors and inductive loads

Abstract: The present invention provides a system for controlling current through inductive elements by automatically switching between a pulse width modulation mode and a linear mode, depending upon the current demands of the inductive elements. A time-base circuit provides periodic pulses that allow current to flow through an inductive device. The current through the inductive device increases over time. If the current through the inductive device exceeds a specified value, the current is shut off until the next pulse from the time-base circuit. After the power supply current has been shut off, current through the inductive device continues to flow through flyback diodes, gradually decreasing over time. Another pulse is provided by the time-base circuit before the current is allowed to reach zero. By controlling the duration and rate of increase and decrease of current through the inductive device, a method of current control for inductive elements has been provided.

Method for making a superconducting current limiter as well as a current limiter produced with such a method

Abstract: The invention relates a superconducting current limiter (1) which has at least one conductor (2) which carries the rated current and which is manufactured at least partly from a superconducting material. According to the invention, to produce the current limiter (1) a strip-type conductor (2) is used which is bounded by a metallic layer (3). The conductor (2) is wound as a bifilar coil (7) and is permanently arranged in a holder (10) which is permeable to flowing media in such a way that its ends can be connected in an electrically conducting way in series or parallel with a further superconducting current limiter (1).

Power conversion equipment and detection ground fault method thereof

Abstract: PURPOSE: To detect a ground fault without connecting a current detector to all the phases of output-terminals for detecting the ground fault, to reduce the cost of a device and to miniaturize the device. CONSTITUTION: A base drive circuit 7 is operated by the signal (b) of a drive control circuit 8 at the time of normal operation. A signal (a) is generated in response to the requirement of ground fault inspection at the time of a shutdown, a DC/AC conversion circuit 3 brings only the Z-phase of a switching element constituted in a bridge to a conductive state, and ground fault currents IG at the time of the occurrence of a ground fault is detected by a current detector 5. An output from the current detector 5 is compared with a reference value by a ground fault detector 9, thus detecting the ground. When the ground fault is detected, the operation of the base drive circuit 7 which is the DC/AC conversion circuit 3 is stopped and protected while an alarm signal (g) is output. COPYRIGHT: (C)1993,JPO&Japio

Superconducting current limiter

Abstract: The invention relates to a superconducting current limiter (1) which is capable of carrying high rated currents. The superconducting current limiters (1) known hitherto have conductors (2) made of metallic superconductors which require a complicated helium cooling for their operation. The present patent application relates to a superconducting current limiter (1) whose electrical conductor (2) is manufactured entirely or partly of a ceramic superconducting material. The conductor (2) is protected by a carrier (3) against mechanical destruction.

Line fault test of model power system with three‐phase superconducting fault current‐limiting reactors

Abstract: A novel three-phase conducting fault current limiting reactor (SCFCLR) is fabricated. The SCFCLR has three superconducting windings with the same number of turns wound on an iron core. The rating of SCFCLR is 200 V, 10 A. Two SCFCLRs are inserted in the sending and the receiving ends of the model power-transmission line. The line fault test of a model power system with two SCFCLRs is undertaken. The fundamental behavior of this reactor is confirmed. In the case of single-line-to-ground fault, the fault current is limited to a very small value by the large zero-phase sequence reactance of the SCFCLR without quench. In the case of a three-phase short circuit, the SCFCLR quenches, and the short-circuit current is limited by the normal conducting resitance of the winding. It is confirmed that the transient stability of the system during line faults is greatly improved by the insertion of SCFCLRs.

Break-before-make control for form C solid-state relays with current limiter bypass

Abstract: A solid-state relay with delayed turn-on time without substantially increasing the time to bring the relay to full conduction after the delay. A current limiter disposed in series with photodiode array limits current therefrom to delay turn-on until the gate voltage of the output transistors is approximately the threshold voltage thereof. Once the threshold voltage is reached, the current limiter is bypassed so that the photodiode array provides full current to quickly turn-on the output transistors.

A Study on a High-Tc Superconducting Fault Current Limiter

Abstract: The application of a high-Tc superconductor with a high critical current density (Jc) to a fault current limiter has been investigated. When the superconductor changes to the normal conductor, it has a resistance which can limit fault currents. Experiments were made using a current limiting element of a YBaCuO film 0. 2 5 μ m thick. The element has a current limiting portion with 1mm wide and 2mm long to limit fault currents. For a half cycle, an alternating voltage (10 Vp, 5 0 H z) was applied to the element. A typical current limiting waveform was obtained in the experiment. The fault current, with a crest value of 420A, was limited to the crest value of 8A. After that, the current was rapidly decreased and was less than 1.6A.

Limitation of switching voltage on connecting inductive load e.g. compensation reactor coil in AC loop - connecting voltage limiter during high voltage periods and disconnecting during stationary operation of load

Abstract: The voltage limiter (6) is arranged on the load side of a system switch (2) in a current line (4) from a mains current bar (1) to an intermittent inductive load resistor (5). The voltage limiter (6) is made of resistive material with non-linear current-voltage characteristics. The voltage limiter (6) is electrically conductively connected to the current lead (4) and to earth (9) by a temporary controlled connection. During the operative period of the inductive load (5), this connection is interrupted by a controlled switch (7). The connection is made through the switch (7) during the period when the system switch (2) disconnects the load (5) from the mains (1). ADVANTAGE - Increases efficiency and life of voltage limiter while still effectively and safely limiting voltage.