Showing papers on "Fault current limiter published in 1976"

Fault indicator for motor vehicle battery charging systems

Abstract: A fault indicator for a motor vehicle battery charging system of the type in which a diode-rectified alternating current generator supplies charging current to the vehicle battery and supplies other loads on the vehicle. The fault indicator is capable of detecting certain faults in the diode-rectified alternator and is capable of detecting certain faults in the generator voltage regulating system. The fault indicator system utilizes current difference operational amplifiers, one of which is connected to detect sharp negative voltage transitions caused by certain faults in the system. The fault indicator also has Zener diodes connected to provide an indication of faults that cause abnormally low or high voltage outputs of the diode-rectified alternator such as an open or shorted voltage regulator. The signal indicator utilized is a light emitting diode and the fault indicator circuit is arranged so as to cause continuous illumination of the light emitting diode under certain fault conditions and a blinking of the light emitting diode during other fault conditions.

People-protecting ground fault circuit interrupter

Abstract: A ground fault circuit interrupter comprises separable contacts for interrupting current flow through a power circuit being protected, trip means operable upon energization to effect separation of the contacts, means for detecting ground fault current, means for monitoring voltage upon the power circuit, and means responsive to the ground fault current detecting means and the voltage monitoring means for energizing the trip means when ground fault current reaches a trip current level. The trip current level varies as a function of the power circuit voltage.

Superconducting fault current limiter. Final report

Abstract: The use of a superconducting element as the active part of a fault current limiter for the power utilities is considered. Such a device is technically feasible over a wide range of parameters for the required electrical power source and material properties of the superconductors available. Limiting is achieved by driving the superconductor into its resistive state and commuting the current into a shunt resistor. For a three phase, 145 KV (RMS), 2 KA (RMS) line, the total cost excluding installation in the power system and shunt resistor is approximately $300,000. The specific advantages and disadvantages are indicated, as well as the outstanding problems to be tackled next.

Current differential fault detection circuit

Abstract: A current differential fault detection circuit. This circuit is used with a plurality of main current transformers respectively coupled to a plurality of separate conductors through which current flows into and out of a sectionalized portion of an a-c electric power system. The secondary windings of the main current transformers are connected in parallel with one another. A normally non-conducting solid state a-c switch is connected in series with the primary winding of an auxiliary transformer and the series combination is connected in parallel with the secondary windings of the main current transformers. Circuit means is provided for sensing the voltage across the secondary windings of the main current transformers. When the secondary winding voltage exceeds a predetermined level the a-c switch is triggered into conduction thereby allowing the fault current to flow through the primary winding of the auxiliary transformer. Circuitry connected to the secondary winding of the auxiliary transformer senses the fault current level and produces an output when the fault current exceeds a predetermined level.

Tungsten lamp circuit for current limiting and fault indication

Abstract: A current limiting and fault indicating circuit for connection between a load and a source of electrical current including a pair of tungsten lamp filaments connected in parallel. The lamp filaments are chosen so that the current drawn by the load during the normal operation of the load produces only a small voltage drop. In the event of an overload or a short circuit, however, the increased current flow through the lamp filaments will heat the filaments to incandescence and the non-linear increase in impedence will absorb the source voltage and indicate the circuit to malfunction by the emission of bright light. The current flowing as a result of the fault will be limited to the rated current of the lamps. Since the rated current of the lamps may be high relative to the normal load current to minimize the voltage drop across the lamps under normal conditions, further limiting the flow of current through the circuit in the event of a short circuit may be achieved through the use of two lamp filaments of different characteristics, i.e., a high wattage-low voltage filament and a low wattage-high voltage filament. The high wattage-low voltage filament can be automatically switched out of the circuit in the event of a fault to force all of the fault current through the low wattage filament. The fault current can thus be limited to the rated current of the low wattage filament. Even this current will be sufficient to raise the filament to incandescence indicating the existence of the fault. The two lamp filaments may be enclosed within a single glass envelope which may be filled with an inert gas at atmospheric pressure to effect cooling of the filaments under normal current conditions. A resettable remote status indicator lamp may be included in the circuit to indicate the existence of an intermittent short circuit.