Showing papers on "Fault indicator published in 1973"

Ground fault detector circuit with feedback to sensor

Abstract: A ground fault circuit breaker is disclosed in which a differential transformer used to sense ground faults is provided with feedback current for generating a magnetic flux which opposes the ground fault induced flux. The resulting flux nulling cancels out the effects of variable core permeability on the breaker trip signal. This permits the use of less expensive and smaller sensor cores together with more consistant and stable calibration. The feedback current is derived from the output signal of a high gain differential amplifier connected to a secondary winding on the core. The output signal from the amplifier is also utilized for actuating a trip circuit which interrupts power and prevents electrocution. Because of the flux nulling, the output signal from the amplifier is an extremely linear and stable function of the ground fault current which facilitates calibration of the circuit breaker. This circuit also permits the use of clamp on ground fault sensor cores in conjunction with a portable ground fault indicator instrument. The instrument reading is then unaffected by dirt and variation of preasure of the split sensor core.

Generator Differential Protection Using a Hybrid Computer

Abstract: This paper presents a rea1-time hybrid, analog-digital, computer technique for differential protection of generators. The fault/no fault decisions are based on the amplitude ratio of the "fault"' and "average through" currents from a selected generator phase. Analog input data pre-processor, fault monitor and soft-ware segments suitable for valid comparison during the transient period after the inception of a fault are described. Typical examples, from out of approximately 800 case studies, including internal and external faults using a three phase generator are presented.

Improved surge tester for electrical windings

Abstract: A surge tester simultaneously applies oppositely polarized surge pulses to a test winding and a standard winding. If there is an unbalance in the electrical characteristics of the two windings, a difference voltage representative of the difference in the voltages developed across the windings is applied to a fault detecting circuit. If the unbalance is sufficiently great, a fault indication is provided. A fault indicator circuit includes an electronic control device arranged so that it can be gated into a conductive condition in response to a fault condition only during half cycles of line voltage of one polarity and the surge pulses are applied to the windings only during half cycles of the opposite polarity. The magnitude of the difference voltage, representative of an unbalance condition, is compared against a reference voltage which varies in accordance with fluctuations in the line voltage. A ground fault condition is represented by an oscillatory voltage and this is detected by providing a fault indication only if the number of pulsations of the oscillatory voltage attains a given pulse count within a given period of time.

Use of SPOOF's in the Analysis of Faulty Logic Networks

Abstract: In general, one cannot predict the effects of possible failures on the functional characteristics of a logic network without knowlegde of the structure of that network.

Monitor system for ground fault relay

Abstract: A ground fault responsive protection system having a ground fault trip relay operable by a ground fault current sensor for operating a circuit interrupter when the ground fault current reaches a pre-established trip level and a monitoring system operable for testing the operation of the ground fault trip relay with selective operation of the circuit interrupter.

Method and system for testing signal transmission paths

Abstract: The disclosure relates to a method and system for testing a plurality of paths over which discrete d.c. signal levels are transmitted between a digital computer and external equipment. A particular configuration of discrete d.c. signal levels is applied to the input or output paths and a signal generated which is related to the sum of the d.c. signal levels on the paths to be tested. A test circuit in a computer input/output unit generates a reference signal and the sum signal may then be evaluated. An unfavorable evaluation may activate a fault indicator.

Ground fault interrupter with pulsed neutral-to-ground fault detector

Abstract: Apparatus for monitoring an alternating-current circuit having a differential current transformer to sense line-to-ground faults includes a pulsed ringing circuit for evidencing freedom of the alternating-current circuit from neutral-to-ground faults that could reduce the sensitivity of the line-to-ground fault detector.

Ground current powered ground fault protector

Abstract: An equipment protection system uses a differential transformer to detect ground faults and energizes a shunt trip coil of a circuit breaker solely with energy induced in secondary windings of the differential transformer by the fault current. Uniform time delay is provided regardless of the magnitude of the fault current and means are provided to prevent partial timing out of the time delay circuit at fault currents below the minimum tripping point. The system provides instantaneous tripping of the circuit breaker upon occurrence of large ground fault currents. A switching triac avalanches into conduction upon occurrence of a relatively large ground fault current to protect circuit components from damage while still permitting energization of the shunt trip coil.

Machine tool fault indicator

Abstract: The crankpins of a crankshaft mounted in a workpiece carriage are successively ground to a desired size by a sequence of movements of a grinding wheel moved under the control of a control circuit. The crankshaft is mounted in clamping mechanisms latched closed and rotatably driven by associated headstocks. During the grinding operation, each crankpin to be ground is axially positioned by an axial locator mechanism mounted on a positioner mechanism which is moved between rest and operating positions, and the final grinding of each crankpin is effected while a retractable work rest mounted on the positioner is pressed against the crankpin. After each pin is ground, the workpiece carriage is traversed and the crankshaft is rotated to position the next crankpin for grinding, and when the final crankpin has been ground the machine returns to an initial position where the clamps are unlatched and opened to enable the ground crankshaft to be replaced by another workpiece. The movements of the various mechanisms of the machine are detected by the operation of limit switches and other switches interfacing with a sequence controller which produces signals continuing the operation of the machine. To facilitate the detection and correction of a fault condition disabling the automatic operation of the machine, a fault detector arrangement is provided which senses an incorrect inital condition by the absence of the operation of one of the limit switches and provides a visible indication of the fault by energizing a light associated with the particular fault. In addition, the fault detection arrangement disables the further operation of the machine in the automatic mode until the specific fault is corrected and the machine placed in a proper initial condition for automatic operation. The operation of the various mechanisms of the grinding machine occur in a predetermined sequence in which the signals provided by the limit switches must occur in proper sequential relationship. The movements of the mechanisms of the machine are divided into events which are clocked by a timer, and the occurrence of a sequential fault will be indicated by the energization of the general fault light and the disablement of the machine from further operation in the automatic mode as well as by the energization of a light associated with the particular sequential fault. Upon correction of the particular fault as determined by the manual operation of the switches associated with the indicated sequence fault, the machine may be returned to the automatic operation by first returning it to the proper initial condition under the control of separately energized push buttons associated with a manual mode of operation.

Safety aspects of high voltage power line fault location techniques

Abstract: This paper considers hazards to personnel and apparatus caused by the use of high voltage techniques of fault finding on power cables.

Fault detecting device for multiplex signal transmission system

Abstract: There is provided a fault detecting device for a multiplex signal transmission system which comprises a fault detecting circuit, whereby when a fault occurs in the level signal line for sending load actuating command signals in a multiplex signal transmission system operated in a time-shared manner, the fault detecting circuit generates a signal for preventing the actuation of the loads due to the fault.