Abstract: A system and method is disclosed for detecting an abnormality in a network for distributing or transmitting electric power at a predetermined fundamental frequency. The system produces a signal representing the fundamental frequency and another signal representing a harmonic current occurring in the network. The phase relation between the fundamental voltage and harmonic current representing signal are compared. The system produces a signal indicating the occurrence of a high impedence fault in response to a predetermined change in the compared phase relationship.

Abstract: An inverse-time timer for a volt/Hertz ratio relay includes a ladder of level detectors associated with a like series of counters connected in cascade with a variable voltage-to-frequency connector responsive to the v/Hz ratio signal for controlling the counters to establish the time delay for tripping.

Abstract: A resettable current limiter is started using an externally generated reset signal, latches on and continues conducting until an overload current is sensed, at which time the limiter shuts off load current. An FET is used both as a series pass element anda load current sensing element. A comparator senses the source of drain voltage drop across the FET and provides a shutdown signal to the FET's gate upon sensing an overload. The limiter may also comprise a solid state switch for positively shutting off the FET using an externally generated off signal. The reset signal reponse circuitry may be set up to be edge triggered to protect against an external short. The reset signal may be a level change or may be a periodic signal. A zener diode may be used for both protecting the FET against excessive voltages and against current surges.

Abstract: A bi-directional DC power controller is provided with a bi-directional DC switch connected between a pair of terminals for connection to a pair of line power conductors. A first difference amplifier is connected to receive voltages at these terminals and to produce an output voltage signal which is proportional to the difference in voltages between these terminals when the voltage at one of the terminals is greater than the voltage at the other terminal, and is constant when the voltage at the second terminal is greater than the voltage at the first terminal. A second differential amplifier also receives voltage signals from these terminals and produces an output voltage signal which is proportional to the difference in voltages between the terminals when the voltage at the second terminal is greater than the voltage at the first terminal, and which is constant when the voltage at the first terminal is greater than the voltage at the second terminal.

Abstract: Loss-of-potential supervision for a distance relay controlling a circuit breaker in a poly-phase electric power transmission system is provided by blocking circuit breaker trip signals in the presence of a low voltage condition and the absence of an increase in current of more than a predetermined amount. Overblocking is prevented for weak feed conditions, a circuit breaker closing on a fault, transients induced by replacement of a fuse, and sequencing caused by tripping of a remote breaker.

Abstract: A phase selector for identifying a faulted phase in a three-phase alternating current electrical current distribution system generates, for each of the three phases, an output signal which includes the phasor sum of a signal related to a fault component of current flowing in the phase, a signal related to a negative sequence component of current flowing in the phase and a signal related to a zero sequence component of current flowing in the phase. The phase selector also generates at least one restraint signal which includes the phasor sum of a signal related to a fault component of current flowing in one of the two other phases of the three phase power distribution system, a signal related to a fault component of current flowing in the other of the two other phases of the three phase electrical power distribution system and a signal related to the negative sequence component of current flowing in the phase.

Abstract: A power supply system for processing current and voltage faults is disclosed. Each phase of a first power source (12) and each phase of a second power source (28) has a pair of switches (60, 64) for controlling the conduction of current from the phase of the power source to a phase load (29). In each of the phases of the first power source (12), a first switch (60) is controlled by a first control signal which has a high level when a voltage fault or current fault condition does not exist. When either a voltage fault or a current fault condition exists, the first switch (60) is turned off. The second switch (64) is turned on by a second control signal during a determination of whether a current fault exists. Furthermore, a logic network causes the first control signal to assume the second level in response to any one of an RMS over/under voltage fault, an instantaneous overcurrent fault, an I.sup.

Abstract: The invention relates to a configuration for rapid detection of short-circuits and for generating an electrical trigger command with an electronic measuring and processing configuration for current values, which compared in a digital comparison circuit with predetermined limit values transmits the trigger command. The measuring configuration determines the current over time as well as the voltage of the grid and the resulting complex impedances and power. In addition to segmentation, standardization and scaling of the current and voltage values, a cross correlation function as well as the respective product and quotient of the Fourier transforms of the voltage and the current for frequency ranges associated with each other are determined, so that a respective power and impedance spectrum are obtained for evaluating the state of the installation.

Abstract: A power supply system, which supplies a number of different A.C. and D.C. voltage levels to a plurality of loads, is monitored at a number of points for undervoltage, overvoltage and/or overcurrent fault conditions. A diagnostics logic circuit, which is formed from relatively inexpensive, readily available logic units, generates a BCD code signal indicating a fault in response to the occurrence of a fault condition at one of the monitored points. The system responds to this BCD fault indicating code signal by, on the one hand, protecting the power system by actuating a main relay to open the A.C. power line to the system and generating a shutdown signal applied to a pulse width modulator of a converter in the system and, on the other hand, by driving a seven-segment display which displays a numeral to indicate the location of the fault condition.

Abstract: Faults in a three-phase power transmission line are identified by vectorially subtracting from the postfault current for each phase, the zero sequence current and the prefault current. The resultant currents which are the vectorial sums of the postfault positive and negative sequence currents are then compared. If the magnitude of the resultant current in one phase exceeds that in each of the other two phases by a preselected factor, than one phase is identified as the phase to ground faulted phase. If the magnitudes of the resultant currents of two phases exceed that of the third, those two phases are involved in either a phase to phase or a phase to phase to ground fault with the distinction being made by the presence of zero sequence current in the later case.

Abstract: The invention relates to a two-wire switch with a power transistor, in pacular, a VMOS transistor which is arranged in series with an auxiliary impedance between two switch connection lines. In accordance with the invention, a logic circuit with an OR function and an AND function is used in the realization of a kind of phase angle control for the power transistor in the presence of an activating signal of an initiator at the switch input.

Abstract: A dimming circuit adjusts the light output of a lamp by controlling the current flow in the lamp that is connected to a transistor, through turning on and off the transistor with a predetermined timing which is changed by the control signal from a control signal generating circuit. The dimming circuit has a protective circuit for applying an off-state command signal to switch the transistor to the off-state by detecting an excess current flowing in the transistor when an input signal is applied as a control signal for switching the transistor to the on-state.

Abstract: A monitoring device connected to an LC filter circuit for determining the occurrence of faults therein includes sensors for measuring the voltage drop across the LC filter circuit and the current flow therethrough. The monitoring device includes simulation circuits for estimating the voltage drop and current flow in response to the actual values of the current flow and voltage drop, respectively. In one position of the double-throw switch, the actual value of the current is compared with an estimated value thereof while in another position of the double-throw switch, an estimated value of the voltage drop is compared with the actual value thereof. Differences between the compared values are detected by a multiplicity of Y-connected limit and counting stages activatable by voltages of different magnitudes and directions for indicating different kinds of faults and for selectively disconnecting the LC filter circuit from a power supply network.

Abstract: An underload protection system for an electric motor connected to first and second power supply lines, the lines being connectable to an AC power supply. The system comprises a line voltage sensing circuit connected to the first line and having a line voltage signal impressed therein, and an amplitude adjustment circuit connected to the voltage sensing circuit for adjusting the line voltage signal to produce an amplitude adjusted voltage signal. A line current sensing circuit is connected to the second line and has a line current signal impressed thereon, and a phase adjustment circuit is connected to the current sensing circuit for adjusting the phase of the current signal to produce a phase adjusted current signal.

Abstract: A short circuit protection device for a unitary voltage gain signal transducer circuit (G.sub.v) and for a load impedance (R.sub.L) coupled to the transducer circuit includes a first (A.sub.1) and a second (A.sub.2) threshold comparator circuit and an actuator circuit (ACT). The input terminals of the first comparator (A.sub.1) are coupled to the transducer circuit input and output terminals and the output terminal of the first comparator is coupled to an activation terminal of the actuator circuit. The input terminals of the second comparator (A.sub.2) are coupled to the ends of the load impedance and the output terminal is coupled to an inhibit terminal of the actuator circuit. A first output terminal of the actuator circuit is coupled to an inhibit terminal of the transducer circuit, while a second output terminal of the transducer circuit is used to deliver a small current I.sub.1 to the load impedance.

Abstract: Apparatus and method for monitoring a self-regulating heater comprising a PTC conductive polymer while it is being powered by a power supply signal. The apparatus is connected to a power supply and to the heater, the heater then producing a heater signal which is fed to a comparator. The comparator deterines the phasal relationship between the power supply signal and the heater signal and indicates when the signals are out of phase by a predetermined magnitude.

Abstract: A safety mechanism is described which is used in an electrical distributing system with a bus-bar and of branches emanating from the bus-bar and has safety relays which turn off the malfunctioning part of the system in case of error. In this safety mechanism, redundancy is increased with respect to a malfunctioning of any one of the relays while the number of safety relays remains the same. This is achieved by the fact that each of the safety relays responds to a measurement of currents and voltages of two branches and acts upon both branches via the switches separating them from the mains.

Abstract: The root mean square value of sensed current within a protected circuit is used to determine the occurrence of an overcurrent condition. A frequency multiplying circuit produces a pulse stream having a frequency proportional to the square of the amplitude of an analog signal representation of the circuit current. A root mean square value over a prescribed interval is developed from the squared current value. The RMS value is processed within an integrated circuit trip unit to determine an overcurrent condition and to operate a pair of separable contacts to interrupt the circuit current.

Abstract: An apparatus and method for detecting an AC power failure condition employs a fast attack, slow decay, energy storage circuit for tracking an AC input signal and for providing a slowly decaying output based upon a last received peak voltage input value. A current detection circuit monitors the current flow to the storage circuit from the AC mains and generates a current detection signal in response thereto. A power failure condition is declared when either the voltage across the energy storage circuit decays below a selected threshold value or current is not detected flowing to the energy storage circuit at a selected time. A particular current detection circuit employs a high permeability core which is saturated by a current in the sensed line having a current value below an expected peak current flowing to the energy storage circuit. An interrogation pulse periodically energizes an interrogation winding which, in the absence of current in the sensed line, induces a signal across an output winding.

Abstract: An intrinsically safe battery pack arrangement for electrically powering electrical devices is disclosed. The power pack has a device for electronically determining a short in a cable or device and switching off the voltage to the power pack. The electronic device includes a transisterized circuit for sensing and controlling current through the cable. When the current exceeds a predetermined maximum, the circuit limits the current in the cable to a maximum value. The circuit is latched in the off position when the short is present for an extended time and the circuit may be reset after the short is removed and the problem corrected. This form of circuitry in power packs for use with mining equipment such as lamps, provides a unit which will not cause hazardous sparks when shorted thereby constituting an intrinsically safe device for use in mines.

Abstract: A protective device for a power element of an integrated circuit includes a circuit element for detecting and processing the value of the current flowing through the power element and the voltage supplied to the power element. The circuit element generates a measuring signal which, when it reaches a predetermined limit value, activates a threshold circuit which reduces the current level in the power element. The protective device also includes a circuit element for amplifying the measuring signal when it reaches the predetermined limit value.

Abstract: A data transmission system for transmitting and receiving data over a transmission line includes a receiving station having a receiving circuit for simultaneously detecting current and voltage signals including the data in the transmission line and applying these signals to a common output impedance, so that an output voltage signal developed across the output impedance will have a sufficient signal level irrespective of the value of other load impedances on the transmission line.

Abstract: A fault in a section of an electrical power supply line is detected by measurement of voltage and current, filtering out high frequency components, and calculating approximations of Fourier transforms of a time window of the voltage and current at a predetermined frequency modified by a continuous phase change at that frequency and then calculating the impedance of the section from the modified Fourier transforms of voltage and current (FIG. 2).

Abstract: An over-current sensing circuit for use with a switching-type power supply for achieving fold-back, which senses not only the load current drawn from the power supply, but also the voltage at the load and the voltage across the power supply potentiometer which is used to set the output voltage. The sensing circuit thereby serves to maintain the current limit point at which fold-back occurs virtually constant in the presence of adjustments of the output voltage of the power supply and regardless of the resistance of the bus which connects the power supply to the load.

Abstract: To protect a transistor its emitter current is converted by a resistor into a voltage which by means of a voltage-current converter is converted into a current which is proportional to the emitter current. The collector-emitter voltage is converted by means of a voltage-current converter into a current which is proportional to the difference between a knee voltage which is applied to the converter, and the collector-emitter voltage, the converter not producing an output current for collector-emitter voltages exceeding the knee voltage. The difference between the output currents of the converters is compared with the current carried by a current source. The protection circuit becomes operative when this difference current exceeds the current carried by the current source. A control amplifier then drives the transistor in such manner that the difference current becomes equal to the current.

Abstract: In direction identification for a close-in fault when the voltage becomes very small, direction of the fault is determined from the discriminant D given by:D=V.sub.k1 i.sub.k2 -V.sub.k3 i.sub.k4where V.sub.k1, V.sub.k3 represent sample values of the voltage at time points k1, k3, and i.sub.k2, i.sub.k4 represent either sample values of the current at time points k2, k4 or such sample values minimum current component values corresponding to pre-fault power flow. Here, k1=n-m-M; k2=n; k3=n-m; k4=n-M, where m represents the number of sampling operations over an interval equal to a multiple of half cycle of the system frequency, M represents an integer, and n represents a sampling time point. A signal for use, e.g., as a condition for tripping a circuit breaker is produced when the fault is found to be in the direction of the protection zone.

Abstract: A protection circuit for a push-pull amplifier includes two sensing transistors arranged in respective feedback circuits. The output signals of such sensing transistors, which are indicative of the output voltage, are used to limit the output current of the amplifier in such a manner that the output current is limited to a first threshold decreasing with a steeper slope as a function of the output voltage of the amplifier between predetermined two output voltage values, and a second threshold decreasing with increasing output voltage at a lesser slope above the higher one of the two predetermined output voltage values. This characteristic response can be overridden by appropriate circuitry so long as the temperature of the amplifier is below a predetermined maximum value, so as to make the output current threshold independent of the output voltage.

Abstract: An apparatus for reducing the difference in electrical potential between two electrical conducting objects located a distance from each other in an electrical conducting medium includes an equalizing cable with a predetermined resistance valve detachably connected between the two objects. A current detector is coupled in series with the equalizing cable between the two objects and generates a first output voltage with a value dependent on the equalizing current in the equalizing cable. An instrument lead is also detachably connected between the objects. A voltage detector connected in series with the instrument lead between the objects senses the potential difference between the objects and generates a second output voltage having a value dependent on the sensed potential difference.

Abstract: A protective relay system for protecting a power system includes a selection circuit, a comparing circuit, and a data processing unit. The selection circuit time-sequentially switches a plurality of input signals having electrical quantities from the power system under control of the data processing unit and applies the input signals to the comparing circuit. The comparing circuit applies to the data processing unit a discriminated output signal representing the result of the comparing of a level of a signal having an electrical quantity and obtained from the input signals to the comparing circuit with a reference level. At a time point upon lapse of a time corresponding to an electrical angle of 90.degree.

Abstract: The invention comprises a method and a device for locating, isolating and by-passing a defective electrical device in an electrical circuit, and comprising sensing current and voltage at a first point in such circuit, on one side of such device, whereby the current and voltage are not significantly altered by the sensing process, sensing current and voltage at a second point in such circuit, on the other side of such device, whereby the current and voltage are not significantly altered by the sensing process, comparing such currents and voltages as between such two points, creating a control signal responsive to such compared currents and voltages, and, isolating such device from such circuit, and thereafter re-establishing such circuit whereby to by-pass such device, in response to a control signal of predetermined characteristics.

Abstract: An output transistor protection circuit in a power amplifier comprises a limiter circuit which limits a collector power dissipation of the output transistors to a predetermined magnitude in accordance with an output voltage level of the amplifier and a current level of the output transistors. For sure limitation operation with a low cost construction, and without destruction of signal waveform, limitation characteristics of the limiter circuit is varied in accordance with detection results of an output voltage level detection circuit which detects whether the output voltage level is smaller than a predetermined magnitude, and a clipping condition detection circuit which detects whether an output stage of the amplifier is clipped.

Abstract: Protection circuitry interposed between a power source and a load is arranged to gradually apply high voltage to the load until the voltage has attained a predetermined percentage of its nominal value. In the event that the load current exceeds a prescribed maximum limit, or in the absence of additional load voltages, the high voltage supply is disconnected from the load.

Abstract: A protection circuit for a switching power amplifier comprises a first detection circuit which detects a current flowing through an output stage switching circuit, a second detection circuit which detects an output voltage of the output stage switching circuit, and an amplitude limitation circuit which limits the amplitude of an input signal to the output stage switching circuit in accordance with both the first and second detection. Thus the switching circuit is surely protected from destruction.

Abstract: Two output transistors constituting a push-pull output amplifier circuit are connected in series between a power supply and a grounded point, and an output terminal is disposed at a point where the two output transistors are commonly connected. An operation detector circuit detects the operation of one output transistor. A level detector circuit detects a d-c voltage level at the output terminal. The two output transistors are driven by a drive circuit in a push-pull manner. The output of the operation detector circuit and the output of the level detector circuit control the drive circuit via a control circuit. When the operation detector circuit detected the fact that the operation of one output transistor has deviated beyond a predetermined detection level, the control circuit works to confine the operation of the abovementioned output transistor within a predetermined restriction level via the drive circuit. The power loss in the restriction level is smaller than the power loss in the detection level.

Abstract: This invention relates to a shorted diode protection system for a brushless alternating current generator of the type having an energizeable exciter field winding. The system includes a circuit arrangement for sensing the voltage difference across the exciter field and pairing the voltage difference with generator load current to thereby provide an output signal that falls within a predictable range of values over a normal generator load current range. The output signal is of such a nature that it falls within a higher range of values upon the occurrence of a shorted diode. Another circuit arrangement is responsive to the output signal such that whenever the output signal exceeds a preset value over the normal load current range, an output is generated that operates to cause the interruption of the exciter field.

Abstract: A secondary arc extinction device in an electric power system, including a bus bar; an electric power line connected to said bus bar; protective relaying means connected to said bus bar; a first reactance means having a first terminal connected to said electric power line; a second reactance means connected between a second terminal of said first reactance means and ground; line voltage detecting means connected to said electric power line for detecting the voltage of said electric power line; current detecting means coupled to said second reactance means for detecting the current flowing in said second reactance means; and controlling means connected to said second reactance means for controlling the reactance of said second reactance means in response to said protective relaying means, line voltage detecting means and current detecting means.

Abstract: A protective relay for protecting a power system from sub-synchronous current oscillations. The protective relay determines both the amplitude and frequency of sub-synchronous current oscillations occurring in the power system. A series of logic relationships, based in part on the parameters of the power system, are implemented by the protective relay such that when the frequency and amplitude of the sub-synchronous oscillation signal satisfy these relationships a trip signal is produced.

Abstract: A protective relay which carries out various relay functions by converting externally received AC data into time widths in accordance with protective ranges and determining whether or not the protective operations are necessary on the basis of the time widths. The protective relay receives a plurality of input AC data through a time-dividing device and converts the time-divided data into the time widths for the relay functions to determine the relay operations of the relay functions on the basis of the time widths.

Abstract: Apparatus for electronically protecting output transistors of electronic amplifiers against thermal overload, overcurrent, overvoltage, and second breakdown mechanism. An analog multiplier circuit, together with a novel circuitry for deriving the instantaneous voltages across, and the currents through, each of the output transistors, is used to obtain the instantaneous power dissipation in the transistors. A thermal sensor, the electrical signal of which is used as an additional variable in the multiplication, yields the thermal derating necessary for the transistors, and an integrating time constant used to weigh the output signal of the multiplier, takes into account the time derating of the transistors.

Abstract: The invention relates to a low impedance excitation system for use in distance relays. In such a system the low impedance check is carried out by comparing the phases of signals (U.sub.D,U.sub.S) which are obtained by forming the sum and the difference from an image voltage signal (U.sub.A) and a line voltage signal (U.sub.K). The triggering characteristic is formed in the complex impedance plane by means of the combination of at least two different triggering characteristics, mainly a circular (K) and a lenticular (L) characteristic, in order to avoid overlapping between the triggering area and the active load area (W) and in order to achieve an adequate arc reserve on the whole length of line to be monitored. The switching over between the different triggering characteristics (K,L) takes place as an operational function of the phase difference (.beta.) between the image voltage signal (U.sub.A) and the line voltage signal (U.sub.K).

Abstract: For the protection of electrical networks in the event of power transients, a surge arrester is employed which, independently of the value of the impedance at any time, continuously monitors and evaluates the change over time either of the measured impedance of the network or of the voltage multiplied by the cosine of the phase shift between current and voltage. Two parallel connected latch circuits store signals related to the current and voltage in the network. The difference between the signals stored in the two latch circuits is fed to a trigger circuit that controls a counter to emit a logic signal at the output terminal of the surge arrester only when the trigger circuit emits a logic signal twice in succession within a predetermined time. With this protection the electrical network is adequately protected against incorrect shutdown in the event of power transients in cooperation with any kind of short-circuit protective relay.

Abstract: A water pump protector which includes electrical circuitry through which an electric motor is energized. The electric motor operates a water pump. The circuitry senses the phase angle between the voltage and the current applied to the electric motor. When the phase angle indicates that the motor is operating without a load, the circuitry deenergizes the electric motor. Thus, the water pump is protected against damage which may occur when the water pump is operated without pumping water.

Abstract: A protective relaying system is disclosed which includes a selection circuit for receiving a plurality of input signals from a power system and for selecting one of the input signals to provide a selected input signal. The system also includes a comparison circuit connected to the selection circuit for receiving the selected input signal, comparing the selected input signal with a predetermined reference signal, and producing a decision signal according to the result of the comparison. The system further includes a processing unit connected to the comparison circuit for receiving the decision signal and processing the decision signal to produce a relay output signal.

Abstract: A circuit protects a high voltage supply for x-ray tubes from the damaging effects of a tube flashover or the like. The circuit monitors line current, and high voltage and reacts to an increase in line current occurring with a corresponding drop in high voltage to turn off the high voltage.

Abstract: A digital controller used in regulating the output of a power supply including a diagnostic circuit for sensing the failure of a component in the power supply. Upon the occurrence of a fault, signals are generated locating the component which caused the shutdown of the power supply. The fault signals are inputted into a plurality of encoders which determine the priority between two or more simultaneous occurring faults and which further outputs binary signals identifying the faulty component. The binary signals are then latched and displayed in a LED display which may be actuated any time after the fault has occurred by the operation of a switch member.

Abstract: Methods and apparatus for detecting a single-phase-to-ground fault on a three-phase electrical power system, and for identifying a faulted phase. A single-phase-to-ground fault is correctly distinguished from other faults, including phase-to-phase-to-ground faults, even with transmission lines which utilize series capacitors, by taking into consideration the phase-to-phase voltage which is in quadrature with the voltage to ground of the monitored phase.

Abstract: A method of identifying faults in a polyphase alternating current electric power transmission system wherein determination of the type of fault occurring is effected by monitoring, using analogue techniques, the instantaneous values of quantities derived from superimposed currents and/or voltages arising in the system on occurrence of a fault. Apparatus for carrying out the method is also disclosed.

Abstract: A method of, and apparatus for, detecting shorted turns in an electrical reactor. The impedance of the reactor, and its rate of change, are monitored. A reduction in impedance which exceeds a predetermined rate of change indicates the impedance change is due to shorted turns, and not to some normal cause, such as temperature.

Abstract: Protective relay apparatus and methods for detecting direction to a fault from a measuring point on an A.C. electrical power transmission line using current and voltage deviation signals which may include traveling wave transients, and for providing both directional and distance information from the same signals after traveling wave transients have been removed. Fault generated current and voltage deviations from the steady-state, prefault magnitudes are used to generate trajectories in one embodiment by differentiating the current deviation and using it as one coordinate, and by using the voltage deviation as the other coordinate. A forward fault produces a straight line trajectory which crosses the origin between the second and fourth quadrants, and the reverse direction fault produces a straight line trajectory which crosses the origin between the first and third quadrants.

Abstract: A digital protective relay system includes a read only memory (ROM) in which a program for executing calculations on a judgment formula for a predetermined protective relay function is stored. Switching of the judgement formula, from one form (e.g., over current protection) to another form (e.g., undervoltage protection), is facilitated by a setting unit and an operation mode switching unit which permit changing of judgement formula constants without changing the ROM program. The setting is used to input desired relay operation threshold values. The operation mode switching unit is used to specify the kind and sign of constants contained in a predetermined term in the judgment formula and also the kind of inequality in the formula.