Showing papers on "Fault indicator published in 1974"

Bridging and Stuck-At Faults

Abstract: The commonly used stuck-at fault fails to model logic circuit shorts. Bridging faults are defined to model these circuit mal-functions. This model is based on wired logic which is a characteristic of many logic families such as resistor-transistor logic (RTL), diode transistor logic (DTL), emitter-coupled logic (ECL), etc. It does not apply to TTL circuits. The model also limits to fan-out-free leads.

Ground fault protector with arcing fault indicator

Abstract: A ground fault detector having an indicator which indicates the presence of a ground or similar fault in an electrical line to be protected where the fault current is not of sufficient magnitude to cause the ground fault indicator to trip a circuit breaker to thereby interrupt the circuit in which the ground fault current is flowing. The indicating circuit provides a recognizable warning that a ground fault has begun or is in progress so that appropriate steps may be taken to cure the fault to locate the fault, or to indicate the relative magnitude of the fault current before it worsens.

Current Limiting Device - A Utility's Need

Abstract: Dramatic growth of today's utility systems is causing fault currents to exceed circuit breaker capabilities at existing major stations. Moreover, mathematical projections indicate that this trend will continue at an accelerated rate. Development of a device to limit the instantaneous magnitude of the fault currents to predetermined levels is actively being pursued. This paper discusses the need and application of such a current limiting device.

First fault indicator for engines

Abstract: A plurality of indicating circuits are coupled to monitor the operating parameters or conditions, such as, for example, oil pressure, temperature, fuel level, and speed, of an engine or the like, and such indicating circuits provide an indication of the first occurring fault or failed parameter capable of causing engine shut down. Optical isolators are used to facilitate coupling respective indicating circuits to conventional condition responsive switches, such as oil pressure and engine temperature switches, and in response to an analog input signal proportional to engine speed a speed detector provides a digital output signal indicative of whether the engine speed is above or below a predetermined level. Moreover, after one indicating circuit has indicated a fault, a disabling circuit disables the other indicating circuits from indicating subsequent faults, and an automatic reset circuit effectively over-rides the disabling circuit to reset each of the indicating circuits upon engine start-up.

Fault indicator in test point cap

Abstract: A plug-in connector for high voltage alternating current circuits includes a conductor embedded in insulating material with a test point terminal capacitively associated therewith together with fault responsive means mounted on the connector and having a target that is shifted to fault indicating position on flow of fault current in the conductor and is reset from the fault indicating position on restoration of energizing voltage to the conductor

One-Cycle Fault Interruption at 500 kV: System Benefits and Breaker Design

Abstract: The need for ultra-rapid fault interruption is identified on the basis of improvements to generator stability and the power transmission capability of the BPA 500 kV system. The development of a modified 500 kV air blast circuit breaker and a special fault sensor, which in combination should reduce total fault duration to essentially one cycle, is then described.

Selective tripping of two-pole ground fault interrupter

Abstract: A ground fault detector-interrupter for a single phase three wire electrical system includes a polarity sensitive fault detector controlling a gate in a manner such that only the hot line that has a ground fault will be interrupted.

Electrical ground fault detecting device

Abstract: A self-contained, hand-held device for detecting ground fault to the housing or casing of AC energized electrical equipment, appliances, tools or building wiring is described. A metal probe at one end of the device held against the conductive housing or casing of the equipment to be tested for ground fault applies, under ground fault conditions, a capacitively induced signal voltage to the conductive equipment housing in contact with the input circuit of the device operative to energize an output circuit including an indicator presenting a visual indication of ground fault.

Ground Fault Tests on High-Resistance Grounded 13.8-kV Electrical Distribution System of Modern Large Chemical Plant---II

Abstract: Actual ground fault tests were conducted to determine the behavior of low-magnitude arcing ground faults in a closed air-filled 13.8-kV terminal chamber. Ground current magnitudes between 10 and 50 A were allowed to flow under various ground fault conditions. The tests that were performed support the value of high-resistance grounding to promote safety and reduce damage to equipment. At higher ground fault current levels the ionization of the air-filled chamber progresses at a rapid rate, and the arc is sustained or phase-to-phase faulting quickly occurs. The lower the ground fault current can be limited the less damage that occurs and the less possibility there is of creating a phase-to-phase fault. The practical consideration appears to be that if ground fault current can be limited to 10 A or less then initial ground faults will either clear themselves or create solid ground paths. This can allow the system to operate until an orderly shutdown procedure can be initiated.

Ground fault detector with a nonlinear sensing means

Abstract: A ground fault detector for an ungrounded electrical distribution system responds to a wide range of ground fault current levels by providing the ground fault sensing circuitry with a high impedance at low ground fault signal levels and a low impedance at higher ground fault signal levels. The varying or nonlinear impedance of the sensing circuitry occurs due to the presence of the series combination of a Zener diode and a resistor connected in parallel with a level sensing means. At ground fault signals below the Zener voltage of the Zener diode, the impedance of the sensing circuitry is that of the level sensing means. When the ground fault signal exceeds the Zener voltage, the impedance of the sensing means is significantly reduced since the Zener resistor is now in effective parallel combination with the impedance of the level sensing means. Varying degrees of filtering of the ground fault signal are accomplished through provision of alternate connection terminals of increasing resistance for a filtering capacitor. A ground fault test circuit for the detector provides the equivalent of one-half ampere ground fault. Higher ground faults may easily be simulated by winding additional turns of a test winding on a differential transformer of the detector; each additional turn simulates an additional one-half ampere ground fault.

Fault detection indicator

Abstract: A fault detection indicator comprises an electromagnetic core and coil assembly, a repulsion permanent magnet and two trip-latch permanent magnets. In addition, an indicator button may be employed to present the state of the indicator. The indicator design presents a simple construction which will electrically change its indicated state, remain in latched position and be capable of being manually restored. Internal switches may be included in the indicator which function in conjunction with the trip-latch magnets.

Monitoring system for an automobile light circuit

Abstract: There is provided a monitoring system for an automobile light circuit which monitors the faulty conditions of the light circuit as well as the light failures. The monitoring system comprises a light fault detecting circuit, a supply cable fault detecting citcuit, a monitoring indicator operation control citcuit, an indicator, etc.

Ground fault and neutral fault detection circuit

Abstract: A circuit is disclosed for detecting ground faults and neutral faults and for providing power interruption in response thereto. The circuit monitors the current flow in the line and neutral conductors and provides a signal to a power interruption circuit in the event that a ground fault or a neutral fault condition is detected. In addition, a signal having a certain frequency is generated and coupled on the neutral line to enhance the probability of detecting neutral faults.

System and apparatus for detecting ground faults on ungrounded, polyphase power distribution systems

Abstract: The disclosure is directed to apparatus for sensing a ground fault in a normally ungrounded, polyphase power distribution system. One of the phase lines is coupled to ground through a first inductor which is transformer coupled with a second inductor connected across two other phase lines. A current sensor responses to current flow in the ground circuit including the first inductor resulting from a ground fault on any of the phase lines by signaling a ground fault relay to either provide a fault indication, interrupt the ground circuit or interrupt the phase lines. A system of ground fault sensors and signal interlocked ground fault relays operating in a multi-zone power distribution system is also disclosed.

Surge tester for testing an electrical winding and including voltage comparison means

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.

Ground fault current detector

Abstract: A ground fault current monitoring and limiting circuit is connected between an isolated electrical power distribution system and ground. Means are included for connecting the power lines alternately to fault current monitoring and detection means. The last-named means provides a low impedance from a line to ground for low values of fault current. The impedance increases sharply for values of fault current above a predetermined magnitude and a warning is provided when the fault current exceeds such predetermined magnitude.

Surge tester for detecting a ground fault in an electrical winding

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.

General fault analysis using phase frame of reference

Abstract: Traditionally, the analysis of power systems under unbalanced fault conditions is carried out using symmetricalcomponent theory. In the paper, an alternative approach, using phase frame of reference, is presented. Full network representation is used, which allows for network asymmetry arising from unbalanced generator impedances or nontransposition of transmission lines. Any type of fault can be represented singly or in combination. Sparsity methods are used to reduce the computation time and storage to a minimum. A special method is incorporated for quadrature-boosting transformers that provides direct solution and retains symmetry of the network equations

Multiple-Fault Detection and Location in Fan-Out Free Combinational Circuits

Abstract: Two algorithms are presented for the detection and location of single or multiple stuck faults in a fan-out free combinational circuit. The algorithms are based on a canonic representation of the indistinguishability classes of faults. The number of tests required in these algorithms are shown to be a linear function of the number of gates in the circuit.

Vehicle fault detecting and indicating system

Abstract: There is provided a fault detecting and indicating system for a vehicle whereby when the level of engine oil or the thickness of brake lining becomes smaller than a predetermined value, such an abnormal condition is detected by a fault detector and an indicator lamp is lighted by a detection holding circuit. The indicator lamp is designed so that it is not allowed to go on in response to any transient fluctuations in the level of the engine oil, whereas once the indicator lamp has been lighted it is held on until a power switch is opened and it is thus independently of the fault detector. The fault detecting and indicating system is further provided with a check circuit which is capable of separately checking the indicator lamp for burnout.

Fault detection and signaling system

Abstract: A fault detection and signaling system is responsive to a fault detection to generate a first type of warning signal indicative of fault detection and includes means operable to indicate that a fault is "acknowledged" and for causing the generation of a second type of warning signal if the fault still exists and to cause ceasing of generation of the first type of warning signal if the fault no longer exists. Further provided is means responsive to fault detection by another fault detection and signaling system for causing generation of a third type of warning signal when a fault is indicated by the present system subsequent to a fault detection by another system.

Short-Circuit Calculations and Relay Coordination Applied to Cement Plants

Abstract: Today's codes and regulations make a coordinated power system a must for cement plants, both new ones and also the older plants. Short-circuit calculations must be made for ali possible fault points in the system. Based on calculated fault currents, all the system protective devices must be applied and coordinated properly to achieve a coordinated power system.

Comments on "Multiple Fault Detection in Combinational Networks"

Abstract: Some comments on a recent contribution on multiple fault detection using test sets for single fault detection are presented. A counter example that shows some defects in generalizing from a tree to an arbitrary network are also included.

Identification of Electrical Parameters in Large Earth Grids

Abstract: The conductors in the earth-grid of a large electric power station must withstand for the maximum fault duration, current due to the worst case unbalanced fault. The fault duration and the worst case fault current may be calculated by well known means. However, the division of fault current when it is injected into the earth grid is difficult to determine with confidence. The authors describe a scale modelling experimental technique, which can yield improved data on the division of fault return current within an earth grid. Some results are quoted taken on a 1 : 400 scale model of the earth grid of the Liddell power station of the Electricity Commission of New South Wales, Australia.