Showing papers on "Fault current limiter published in 1975"

Ground fault circuit interrupting device with grounded neutral detection

Abstract: The secondary winding of the differential current transformer in a ground fault circuit interrupter is normally short circuited through an electronic switch. A relaxation oscillator, including a timing capacitor, acts to periodically open the switch and divert any secondary current through a burden resistor, developing thereacross a relatively high amplitude fault signal voltage indicative of a liine ground fault. The timing capacitor discharges through the primary winding of a second transformer coupled with the neutral conductor to develop, in the event of a desensitizing neutral ground fault, a fault signal voltage across the burden resistor.

Ground monitor and circuit breaker actuating device

Abstract: A ground monitor and circuit breaker actuating apparatus for monitoring the continuity of the ground and pilot conductors in a power distribution system and for deenergizing the power supply system when a true fault in the ground or pilot conductor occurs, including a DC power supply, an impedance bridge which passes a test signal whenever a bridge imbalance occurs in response to a fault logic signal or a fault in the pilot conductor or the ground conductor, an oscillator which generates a test signal for use by the bridge, a fault logic generator which generates a fault logic signal for causing intermittent unbalancing of the bridge and for use by a pulse rate discriminator, a filter which eliminates spurious signals passed by the bridge, a pulse former which converts the filtered signal into a pulsed fault signal, a threshold detector which passes the fault signal if the voltage level of the pulses exceed a predetermined threshold voltage level, a phase detector and a null output detector which compare the phase relationship between the test signal and the fault signal and which indicate when the bridge is in an unbalanced condition, a pulse rate discriminator which compares the timing of the pulses of the fault signal with the pulses of the fault logic signal and develops a control signal commensurate therewith, and a relay which breaks the circuit of the power system in response to the control signal.

Polyphase fault current flow detecting and resetting means

Abstract: Detection of fault current flow in any conductor of a polyphase alternating current system is provided by a fault responsive device that is reset only when normal current flows in each conductor A reed relay is latched in operated condition on the occurrence of a fault and is unlatched by application of a direct current source

Fault commutation system for static inverters

Abstract: An inverter system having a dc input and an ac output has a fault sensor and switching provisions for diverting current to an additional path away from overloaded semiconductors of the inverter upon a fault. The system has a resonant inductance and capacitance circuit at the dc input, whose capacitance discharges through the inductance upon a fault and recharges with an opposite polarity to apply the reverse polarity to semiconductors of the inverter in an attempt to interrupt the fault. Initially the discharge of the capacitance is blocked by a second switching circuit until the fault sensor produces a fault indication signal, so that no portion of the initial charge of the capacitance is wasted by discharging into the faulting semiconductors of the inverter before the current diverting path is established.

Mass of current inrush limiters

Abstract: An arrangement to eliminate the initial current overshoot which normally occurs when a tungsten incandescent lamp is connected to a power source. The arrangement uses a negative temperature coefficient thermistor having a certain predetermined mass. It has been determined that a practical limiter to eliminate current overshoot can be made only when the mass of the limiter is within a relatively narrow range. The hot and cold resistance of the limiter must also be within prescribed ranges to give a limiter which is not only effective in eliminating the current overshoot, but also efficient in steady state operation such that the limiter dissipates less than 1% of the total power.

Fault current flux detector - trips on AC or DC fault or component failure

Abstract: The current flux determining device has a magnetic flux conductor linked with a current loop and carrying the collected flux, especially for application in a fault current circuit breaker, which responds to both AC and DC faults and to changes in normal operation due to component failure in the instrument itself. The current loop is the constituent part of a detector circuit which determines its induction and means to monitor the characteristics of the detector circuit are also provided. The detector circuit may be an oscillatory circuit or the frequency determining part of a relaxation oscillator.

Circuit interrupter with ground fault trip control

Abstract: A circuit interrupter having an associated control system which senses overload current or ground fault current and causes an appropriate tripping of the circuit interrupter. Tripping energy for causing the circuit interrupter to open under a normal fault condition is derived from the fault current itself. In addition, tripping energy for causing the circuit interrupter to open due to a ground fault condition is derived from the ground fault current.

Vacuum fault current limiter

Abstract: A vacuum current limiting circuit interrupter having rapidly separable contacts and magnetic field coils disposed to produce a magnetic field transverse to the arc formed during circuit interruption. The transverse magnetic field creates arc instability and causes rapid arc extinction. The relatively movable contacts are disposed in an evacuated insulating envelope and are movable between a closed position completing an electrical circuit through the vacuum interrupter and an open position wherein the contacts are spaced relatively far apart with respect to the necessary voltage withstand level of the circuit interrupter. Magnetic field coils are supported to produce a magnetic field transverse to the arc plasma when the contacts approach maximum separation creating arc instability. An alternate current limiting path is provided in parallel with the vacuum interrupter through which reduced current flows until complete circuit interruption.

Ground fault detector circuit with high current inhibit

Abstract: A current transformer couples to the power lines leading to a motor starter and it generates a current proportional to the current which flows as a result of ground faults. When the ground fault current reaches a first level, the circuit is tripped and a circuit breaker deenergizes the motor starter. When the ground fault current reaches a second, much higher, level the circuit is inhibited from operating to allow circuit interrupting devices in the motor starter to interrupt the circuit to the motor.

Ground fault circuit interrupting device and differential current sensor therefor

Abstract: The secondary winding of a differential current transformer in a ground fault circuit interrupter is short circuited through an electronic switch The switch is periodically opened to force any secondary current occasioned by the existence of a ground fault to flow through a burden resistor, thereby developing a relatively high amplitude signal voltage thereacross for processing by a signal processor pursuant to initiating circuit interruption

Power transmission control system

Abstract: The ac transmission system is protected by circuit breaker apparatus capable of responding to fault current levels exceeding a predetermined critical fault level, but less than the maximum fault current. The fault current levels exceeding the critical level are detected by comparison of actual line current to a simulation of the critical level of fault current for one of a plurality of phases 01, 02, 03. Reference signals in quadrature with the three line voltages are continuously fed to differential amplifiers having both inputs connected in parallel until a potential fault is detected when one input is disconnected and clamped at the potential it had at the time of disconnect. The resulting output of the differential amplifiers accurately simulates the time-varying current of a system fault. The simulated signals are compared to actual line current to determine in less than one cycle if a fault is occurring and to order the appropriate breaker action.

The fault recovery performance of a helium-insulated rigid AC superconducting cable

Abstract: If a through fault causes overheating of a superconducting cable, the cable cannot be used until the normal operating temperature is re-established. Since this could take more than a day, the cable must be designed so that the largest through fault expected will not overheat the cable system. This paper describes both a theoretical analysis of the behavior of a rigid coaxial ac superconducting cable system during and following a through fault as well as the theoretical and experimental verification of the ability of this design to continue to deliver power following a through fault.