Showing papers on "Fault indicator published in 1971"

Fault detection in digital circuits

Abstract: Introducing a new hobby for other people may inspire them to join with you. Reading, as one of mutual hobby, is considered as the very easy hobby to do. But, many people are not interested in this hobby. Why? Boring is the reason of why. However, this feel actually can deal with the book and time of you reading. Yeah, one that we will refer to break the boredom in reading is choosing fault detection in digital circuits as the reading material.

A Nand Model ror Fault Diagnosis in Combinational Logic Networks

Abstract: A network model colled the normal NAND model is introduced for the study of fault diagnosis in combinational logic circuits. It is shown that every network can be transformed into an equivalent normal NAND network from which all the information pertaining to the diagnosis of the original network con be obtained. The use of this model greatly simplifies fault analysis and test generation.

Alternating current fault indicating means

Abstract: Fault current flow in an alternating current carrying conductor is shown by operation of a target to fault indicating position from which it is restored in response to the energizing voltage of the conductor. A C-shaped magnetic core embraces the conductor and has a winding thereon the output of which is rectified and, when it reaches a predetermined value, is applied to a trip winding of a fault indicator to operate the target. A reset winding of the fault indicator is energized from a capacitor that is charged from the conductor voltage a source of which may be obtained from a capacitor plate embedded in the insulation of a conductor terminator. In a modification alternating current is applied to the trip winding to demagnetize the magnetic core of the indicator and allows a permanent magnet to bias the target to fault indicating position. Other modifications include energization of the reset circuit from the secondary winding of a distribution transformer, provision for magnetizing the distal ends of a U-shaped yoke embracing a conductor carrying fault current, and application of the yoke to the conductor of a pad mounted switching arrangement for a transformer.

Automatically resettable fault indicator

Abstract: A pair of opposed L-shaped pole pieces of demagnetizable low coercive force material is arranged to embrace an alternating current carrying conductor with the short legs in opposition and the long legs carrying reset windings which are energized with unidirectional current from a capacitor that is charged by a rectifier energized from a capacitor plate electrostatically related to the conductor or a secondary winding of a transformer the primary winding of which is energized from the conductor A four pole fault indicating rotor is held in a normal position by the magnetic fields from the short legs A biasing permanent magnet, having magnetic poles of opposite polarity, is offset from the short legs and biases the rotor to fault indicating position when the L-shaped pole pieces are demagnetized by alternating magnetic flux generated by flow of fault current in the conductor Permanent magnets at the distal ends of the long legs of the L-shaped pole pieces are effective to change the fault current response of the rotor

Data transmission system with immunity to circuit faults

Abstract: A system for use with a data transmission network having a central station and a plurality of remote stations connected in series by a low grade transmission line such as a telephone pair. The system of the invention is immune to common transmission line faults, such as a line to ground short, a line open circuit, a line to line short, etc. and will continue to operate in spite of such faults. The system is also capable of identifying a transmission line fault when it occurs, the nature of the fault, and the approximate location of the fault in the network.

Fault indicator and locator for buried cables and zero sequence current sensing device

Abstract: An underground cable fault indicator and locater is provided to indicate the location of a fault or short circuit in the cable. The cable is passed through the apertures of a plurality of spaced transformer sensors connected to indicating elements located in below grade vaults or above the ground. Upon the occurrence of a fault in the cable, the indicating elements provide a visual indication of the section of the cable in which the fault has occurred.

Current measuring and automatically resettable fault indicating means

Abstract: A capacitor is charged through a capacitive coupling to a high voltage alternating current electric power conductor and is discharged when the charge reaches a predetermined value to reset fault indicator that previously had been operated by flow of fault current in the conductor. The magnetic circuit employs a demagnetizable low coercive force core in the form of a bifurcated yoke or a ring having magnetizing windings energized on discharge of the capacitor. A manually resettable fault indicator employing a demagnetizing winding on a low coercive force ring also is disclosed.

Ground fault detector and method of ground fault detection

Abstract: A ground fault detector for detecting both balanced and unbalanced faults, eg. leakages to ground or other faults in a floating direct current system, comprises, first and second resistances connectible respectively to the positive and negative buses of the system, a two-way switching device operable to connect to the first and to the second resistances alternately, a fault condition being detected by voltage level detecting means connected between the switching device and ground, and a method of detecting ground faults in such a system by continuously alternately checking positive and negative sides of such system against predetermined known reference resistances.

Isolated power ground fault detector system

Abstract: A ground fault detector system for isolated power lines, especially those for use with operating room and intensive care monitoring equipment including an isolated test circuit arrangement for checking the operation of the system, that does not itself introduce potentially hazardous and dangerous ground faults into the isolated power lines being monitored. More specifically, the isolated power ground fault detector system of the present invention functions to alternately connect a detector circuit to the power lines at a frequency which is a submultiple of the source frequency. The detector senses both capacitive and resistive ground faults and provides an output voltage signal representative of the magnitude of the ground fault. This output voltage signal is compared to a reference voltage in a voltage comparator which activates alarms and indicators if the ground fault exceeds a preset threshold value. The system also includes a test circuit for checking the operation of the system which when actuated simultaneously switches the detector system from the isolated power lines to auxiliary power lines and introduces a simulated capacitive resistive fault into either of the auxiliary lines. By this arrangement, the system may be checked without introducing a potentially hazardous and dangerous ground fault into the isolated power line supplying the equipment.

Ground fault detection system with sequential line testing

Abstract: An a-c line, isolated from ground by a transformer, is continuously tested for ground faults through a switching network which sequentially completes a circuit between the a-c conductors, an apparent active power source, and a ground fault detection network. A fault condition detection network is coupled through a bridge circuit to the a-c lines, to provide an indication of a simple fault on either line, or a substantially unbalanced fault on both lines. An oscillator and ring counter arrangement continuously drives a switching network to test for individual line grounds, and balanced and unbalanced double line faults. A self-contained power supply arrangement is provided.

Fault locating system for electrical circuits

Abstract: A fault locating system for electrical circuits consisting of three major components, a fault sensor, a control circuit or channel, and an indicating device. The fault sensors indicate an abnormal current flow when a fault occurs and transmit the information through the control circuit or channel to the indicating device which in turn displays the information. The control circuit connects the fault sensors in series or parallel, and the sensors are oriented in spaced relationship along the cable or electrical circuit being monitored so that fault detection between adjacent sensors is determined by the indicating device. The system may be set up for automatic resetting. The preferred sensor is a magnetic reed switch, and the fault indicator preferably incorporates a circuit with fast response.

Transmission line fault indicator and locator utilizing variable frequency source coupled to one end of line

Abstract: A system is disclosed which locates open and short-circuit faults on a transmission line by sensing a minimum occuring at the input end of the line. The apparatus comprises a variable frequency test signal source coupled to the input of an amplifier the output of which is adapted for connection to the input end of the transmission line. The frequency of the test signal is varied until a minimum is sensed at the output of the amplifier indicating the presence of a fault on the line. The location of the fault, that is, the distance from the input end of the line to the fault, is determined by the frequency of the source signal at which the minimum is produced. Means are provided in the system for resolving the ambiguity between an open-circuit fault and a short-circuit fault.

First fault annunciator system

Abstract: Fault occurrence displaying system, for use with machinery, which automatically signals and initially displays only a firstoccurring of perhaps several machine faults which occasion machine shut-down. The system includes means for automatically signaling and displaying both system failure and proper system functioning as well as means automatically operative to hold a fault signal on until manually turned off and means to hold successive fault signals inoperative until the first-occurring fault signal is silenced (i.e., turned off).

Electrical apparatus including a ground fault sensor

Abstract: A ground fault detecting system including a current monitor, a ground fault sensor and a circuit breaker. The ground fault sensor responds to the presence of ground fault current to actuate a circuit breaker to open the circuit in which the ground fault current is flowing. The ground fault sensor includes circuit elements which perform corresponding circuit functions such as time delay and reset. The ground fault sensor is adapted to provide an adjustable or variable time delay so that the circuit breaker to be tripped may be delayed in tripping through a wide range of time periods after the initial sensing of the ground fault current.

Determination of Fault Surge Waveshapes with Particular Reference to Fault Detection

Abstract: This paper describes the analytical procedure of determining the attenuation and distortion of fault-generated surges on transmission lines when the skin effects of conductor and earth are taken into account. Herein, the term which considers the skin effect of the earth has been modified. After comparing the results with known approaches, a method, for selecting the circuit parameters of the detection circuit which is used to couple the fault signal from the transmission line to the fault-locating equipment, is given.

Fault indicating apparatus

Abstract: Disclosed is fault indicating apparatus responsive to normal and excessive current associated with an external circuit conductor being monitored, the fault indicating apparatus including an indicator for providing a visual indication of the normal or fault current condition in the external circuit conductor, a fault responsive network portion for selectively switching current through a fault winding associated with the indicator during excessive current flow, a reset network portion for selectively providing current pulses through a reset winding associated with the indicator during normal current flow, the reset network including a relaxation oscillator for periodically triggering a transistor switch into conduction for providing the current pulses to the reset coil, a diode-capacitor network operatively responsive to the excessive current through the monitored conductor for controllably disabling the relaxation oscillator during the fault cycle, the fault indicator apparatus automatically providing a visual indication of the normal or fault condition of the monitored conductor.

Location of faults in cables

Abstract: Apparatus for reducing the resistance of a high resistance fault between two cores or between one core and the sheath of an electrical cable comprising a first transformer having a high open circuit voltage rating and a low short circuit current rating and a second transformer having a low open circuit voltage rating and a high short circuit current rating. The two transformers are connected in series and across the two faulty cores or between the faulty and the sheath and their respective primary windings are energized. Initially the sum of the two secondary voltages will be applied to the cable to reduce the fault resistance. This will cause the fault current to increase. When the fault current increases beyond the short circuit current rating of the first transformer this transformer will zero leaving only the second transformer to burn the fault down to a point where conventional fault locating apparatus can be employed to locate the fault.

Power control system having fault sensing means

Abstract: A SYSTEM FOR CONTROLLING THE SUPPLY OF ELECTRICAL POWER FROM A BALANCED POLYPHASE POWER SOURCE TO A LOAD SUCH AS THE PHASE WINDINGS OF AN ELECTRICAL MOTOR IN WHICH MEANS ARE PROVIDED FOR SENSING IMPROPER APPLICATION OF THE POWER TO THE LOAD. A PLURALITY OF SELECTIVELY ENERGIZABLE A.C. POWER SWITCHES EACH HAVING FIRST AND SECOND POWER TERMINALS AND A CONTROL TERMINAL ARE ADAPTED TO COUPLE ASSOCIATED ONES OF THE POWER TERMINALS OF THE SOURCE TO THE LOAD. A SUBSTANTIALLY NON-REACTIVE, HIGH IMPEDANCE LINE NEUTRAL SENSING NETWORK HAVING A JUNCTION DEFINING A LINE NEUTRAL POINT IS CONNECTED ACROSS THE FIRST POWER TERMINALS OF THE A.C. POWER SWITCHES, WHILE SIMILAR LOAD NEUTRAL SENSING NETWORK HAVING A JUNCTION DEFINING A LOAD NEUTRAL POINT IS CONNECTED ACROSS THE SECOND POWER TERMINALS OF THE A.C. POWER SWITCHES. MEANS ARE COUPLED BETWEEN THE LINE NEUTRAL JUNCTION AND THE LOAD NEUTRAL JUNCTION FOR SENSING A DIFFERENCE IN ELECTRICAL POTENTIAL THEREBETWEEN AS AN INDICATION OF SYSTEM MIS-OPERATION.

Unbalanced Faults in Series Compensated Transmission Lines

Abstract: This paper presents a technique using the Gauss-Seidel iterative approach for the analysis of power systems which contain series compensated lines. This approach includes the effect of system dissymmetries due to a single unbalanced fault and due to a single or -two phase series capacitor short circuit caused by the excessive fault currents. Single phase to ground, two phases and two phase to ground fault studies of a series compensated power system are included.