Abstract: A microprocessor based switch such as a circuit breaker generates digital rms representations of analog load currents from n samples of the analog currents per cycle synchronized to the line frequency, where n is an odd integer equal to a selected highest order harmonic to be detected plus 2. A routine determines whether the power system is 50 or 60 Hz, and automatically sets the sampling interval to provide exactly n samples per cycle for the connected source. Terminals for rapidly resetting an analog memory for calibration and field testing of a long delay trip are hidden behind a removable rating plug.

Abstract: The monitoring device comprises a measuring channel of the ground fault voltage, a measuring channel of the ground fault current, and a digital processing circuit whose role is to search for and indicate the presence of a ground fault. The processing circuit determines the fundamental parts of the ground fault current and voltage to compute the phase difference .phi. between the two parts and the cos .phi. value. The evolution of this phase difference is representative of a fault.

Abstract: A method and a device for phase selection for single-pole tripping of high-impedance ground faults in direct grounded power networks. Starting from the ratio of the negative-sequence voltage to the zero-sequence current (U2/I0) and the ratio of the negative-sequence voltage to the positive-sequence voltage (U2/U1), two criteria with different conditions are formed, each of which indicating a faulted phase, and if both criteria indicate the same phase as faulted, single-pole tripping can take place.

Abstract: A circuit analyzing system includes a current transformer for extracting current from a phase or neutral conductor of a three phase line, a filter connected to the output of the current transformer and functioning to substantially trap current at the fundamental frequency while substantially passing currents at various harmonic frequencies thereof, and signal processing circuitry connected to the output of the filter to perform various functions with the harmonic frequency current input thereto. Among these functions, as shown in various preferred embodiments, are measurement of the harmonic signal in RMS and conveyance of the output to a display instrument for a user or utility's convenience in monitoring harmonic frequency circuits, which have become more common with the advent of electronic equipment having internal power supplies such as personal computers, work stations, printers, and the like.

Abstract: There is disclosed a monitoring apparatus for a multiphase electrical system of very simple and reliable circuit design capable of monitoring such a system and producing fault signals to operate protective relays and for visual indication. A main component of the apparatus is a multiphase, full-wave bridge rectifier circuit having matched voltage dropping input resistors so that the output of the bridge is a low voltage fluctuating DC signal such that neither the semiconductor diode rectifiers of the full-wave bridge or other internal components of the monitoring apparatus are exposed to high power line voltages. Phase unbalance in the apparatus is detected by evaluating the ratio of the peak to trough voltage of the fluctuating DC signal produced by the full-wave bridge.

Abstract: An adaptive sequential controller (50/50') for controlling a circuit breaker (52) or other switching device to substantially eliminate transients on a distribution line caused by closing and opening the circuit breaker. The device adaptively compensates for changes in the response time of the circuit breaker due to aging and environmental effects. A potential transformer (70) provides a reference signal corresponding to the zero crossing of the voltage waveform, and a phase shift comparator circuit (96) compares the reference signal to the time at which any transient was produced when the circuit breaker closed, producing a signal indicative of the adaptive adjustment that should be made. Similarly, in controlling the opening of the circuit breaker, a current transformer (88) provides a reference signal that is compared against the time at which any transient is detected when the circuit breaker last opened.

Abstract: A three-phase power monitor operates a contactor between a supply of three phase electrical power and a three phase load. A phase integrity detector has three inputs connected respectively to the three phases of the electrical power. If a loss, reversal, or dissymmetry is detected, a photoemitting device is actuated. Actuation can also result from low or high line frequency. A power supply circuit is input with the three phases of power and has an output providing a dc level corresponding to the voltage level of the three-phase electrical power. A hold circuit has a first time constant associated with it and attains a hold level when current is applied to its input, but reverts to a release level after this current ceases. An interrogator circuit is coupled to the power supply and to the input of the hold circuit and provides a periodic recharge current to the hold circuit at a period that is shorter than the period of the hold circuit.

Abstract: A digital voltage protection circuit (138) and a phase monitor circuit (154, 160, 162, 168) disconnect AC-powered user equipment (22,182) from the AC power supply (141) whenever the AC power line voltage is outside a predetermined operating voltage window and when any two phases of the power supply (141) are separated by more than a predetermined phase angle. The user equipment (182) is automatically reconnected to the power supply (141) only after the power line voltage and phase remain continuously within operating range for a predetermined delay period. The voltage monitor (138) contains a digital comparator (18) that uses integrated circuit digital logic thresholds as reference voltages for setting upper and lower voltage window limits. The controller protects the user equipment from both over-voltage and under-voltage (brownout) conditions and from phase errors.

Abstract: The present invention provides a simple, reliable, comprehensive electrical phase and amplitude fault detection and response system. The system includes means for detecting any of various electrical faults, such as impermissibly low voltage levels, impermissibly high voltage levels, phase dropouts, single-phasing, phase reversals, and/or total power loss. Further, the invention provides both fault detection and response customized to the plant equipment, providing power cut-off an appropriate time after a given fault is detected, and preventing premature power restoration when the line power has not been fully returned to normal. The system provides the fault detection and response functions without the need for electrical power of its own, avoiding dependence on line voltage, batteries or back-up generators. This functioning independent of the presence of electrical power is enabled through use of a pneumatic arrangement for interrupting power to plant equipment.

Abstract: A protection circuit for three-phase power systems incorporates overcurrent protection along with phase loss and phase imbalance by means of common current sensing transformers. The phase loss and phase imbalance are determined by a pairwise comparison algorithm.

Abstract: A sensor connected to two different phases of an electrical wiring system provides positive protection against overloading of any single phase by preventing operation of one circuit load when there is no phase difference between the wiring circuits.

Abstract: A system and method for detecting partial discharge of gas-insulated switchgear wherein a high-frequency component and the fundamental wave component of the voltage applied to the conductor of the gas-insulated switchgear are detected, the zero-cross point of the fundamental wave component is set as the starting point for the voltage, and the presence of partial discharge and the reason for the occurrence of partial discharge are ascertained based on the phase difference between the phase of the detected high-frequency component and the phase of the starting point of the voltage.

Abstract: A polyphase reversal detection and correction system which operates over a wide range of line frequencies and produces an automatic phase correction for maintaining proper phase sequence to a rotating device. The system includes a circuit arrangement for developing peak integrated signals by comparing the relation of various input phases, and developing an integrated reference phase signal. The input phase signals and the reference phase signals are compared to determine and correct the input phase sequence.

Abstract: A remotely controllable circuit breaker and switch for controlling the flow of current from a three phase AC power source to a three phase load, and usable in either wye or delta configurations. A latching relay controls the current for each phase. Current samples in the three phases are scaled and converted to DC values by scalers and RMS to DC converters. The DC values are converted to digital current values by an analog-to-digital converter which sequentially scans the DC values of the currents in the three phases. A central processing unit monitors the digital current values to detect significant phase imbalances and overcurrents which persist for time periods which exceed allowable limits according to a predetermined time-dependent function, and to initiate opening of the relays in response thereto. The central processing unit also opens and/or resets the relays in response to remote control signals.

Abstract: Faults in the operation of a multi-phase A.C. generator are detected by monitoring the phase difference between two line-to-line voltage of the generator and comparing this phase difference with a predetermined value or range of values to indicate a fault.

Abstract: A power supply for a video display device includes a protection circuitry which shutdown the power supply to prevent damage to the power supply or the display device. The protection circuitry monitors sync pulses generated in the video display device and disables the power supply switching transistor in the absence of the sync pulses. The protection circuitry is triggered in the event a fault occurs in the power supply or the video display device.

Abstract: Circuit breakers can be used to replace fuses in plant comprising centrifuge machines driven by small three-phase electric motors. The circuit breakers incorporate three bi-metal strips which bend due to the heat produced by current flow. Loss of current in one phase results in unequal bending of these trips. In one arrangement, a light-emitting diode 5 fitted to a first strip 2 produced light to pass through an aperture 8 in a plate 7 on the second strip 3 to fall on a photo-sensitive detector 6 on the third strip 4. Any unequal bending causes the light to be cut-off and the resulting signal can be used to trip the circuit breaker. In some cases the strips are the strips in the circuit breaker.

Abstract: An air-conditioning apparatus includes a control circuit adapted to detect, from among first to third line voltages of a three-phase AC power supply, the second or third line voltage not synchronizing with a serial signal. The control circuit detects a difference between a phase angle of the detected line voltage and that of the serial signal, compares the difference with set values and determines, by that comparison, whether the three-phase AC power supply is in a positive-phase sequence or in a negative-phase sequence. The operation of a compressor is inhibited when the negative-phase sequence is determined by the control circuit.

Abstract: An opposite phase detecting device for alternating current electrical equipments includes a zero cross circuit synchronizing positive half waves of first and second line voltages of a three-phase AC supply supplied to an AC electrical equipment and generating first and second synchronizing pulses each having a pulse width corresponding to an electrical angle of approximately 180 degrees, a counter circuit counting the first synchronizing pulses from the zero cross circuit, a one-shot multivibrator triggered by the second synchronizing pulse to thereby generate a reset pulse having a relatively short time interval, and an AND circuit generating a reset signal based on a logical multiplication of the reset pulse generated by the pulse generating circuit and the first synchronizing pulse generated by the synchronous circuit. The counter circuit is reset when supplied with the reset signal from the AND circuit.

Abstract: A protective device prevents electrical load, such as three-phase induction motor, from overheat fault caused by undervoltage and phase failure condition in a three-phase power supply system. The circuit arrangement of the protective device includes a rectifier circuit, a voltage dropping circuit, a filter circuit, a current limiting circuit, a photo coupling circuit, and a large current control switch for controlling actuating coil of an electromagnetic switch. When the fault condition of undervoltage and phase failure is happen, the protective device will cut the load off the three-phase power source so that both the load and electromagnetic can be protected.

Abstract: A device to locate internal faults in a high-voltage capacitor battery that has a plurality of symmetrically parallel and series-coupled capacitor banks arranged in parallel branches coupled by shunt branches. The phase angles of the shunt currents flowing in the shunt branches relative to the total current flowing in the parallel branches are determined. A fault is located in one of the capacitor banks based upon these determined phase angles.

Abstract: A three phase loss protection circuit for a three phase rectifier. The rectifier includes a circuit which inhibits its operation when either of two of the three phases are lost. In response to the loss of the third phase, the loss protection circuit causes one of the other two phases to be lost at the input to the inhibiting circuit. The loss protection circuit does not interfere with the operation of the inhibiting circuit when either of the two phases are lost. In an alternative embodiment, the loss protection circuit includes circuitry to ensure that the rectifier is inhibited even though part of a lost phase may be recreated by the rectifier's input filter.

Abstract: An adaptable current regulating system provides a regulated current in accordance with both the actual characteristics of a system under control and the actual measured period of an AC supply. The system constantly monitors its status, and provides a master controller with the status of the system, and is programmed to provide control in accordance with information received from the master controller.

Abstract: In an electrostatic paint spraying installation or the like, a high-tension voltage generator comprises a voltage rectifier-multiplier in a mobile subsystem and a grounding connection in a fixed subsystem. A conductive wire connects an input terminal of the voltage rectifier-multiplier to the grounding connection. When the high-tension voltage generator operates, a high-frequency alternating current residual signal injected into this conductive wire is sensed and measured. The measured value is compared against a reference value that may be variable. The high-tension voltage generator is disabled if the difference between the measured value and the reference value reaches or crosses a predetermined threshold.

Abstract: A single or multiple phase directional harmonic overcurrent relay device suitable for simultaneously monitoring overcurrents at either of two harmonic frequencies in an electric power system is provided which comprises current and voltage input means, upper and lower harmonic current and voltage filters, a trip means which can enable an appropriate protective or diagnostic device when a condition of harmonic overcurrent exists, and a phase detection means which receives signals from the voltage and current filters and transmits a signal to the trip means only when the phase angle between the harmonic voltage and harmonic current is within a specified range. The two harmonics that are to be monitored simultaneously, such as the 5th and 7th harmonics, can be selected by means of a series of simple filter cards which can be inserted into a card cage in an apparatus housing the relay of the present invention.

Abstract: A signal representative of the zero sequence current is obtained from current transformers associated with each phase and with the neutral if applicable by separate summing, in two distinct conductors, of the positive half-wave currents and of the absolute value of the negative half-wave currents produced by the set of current transformers, the difference between the currents flowing through these two conductors being representative of the zero sequence current.

Abstract: In a system interconnecting inverter apparatus, an inverter for controlling power of an AC power system is coupled, via a coupling reactor, to the AC power system having a system voltage. A system phase signal indicating the phase of the system voltage is detected by a system phase detection circuit in real time. Another phase signal indicating the phase of the system voltage is detected by a comparison phase detection circuit with a predetermined delay time, and the detection result is temporarily stored in the circuit as a comparison phase signal. The system phase signal and the comparison phase signal are phase-compared by a stop circuit. When a phase difference between the system phase signal and the comparison phase signal exceeds a predetermined value, the stop circuit stops the operation of the inverter.

Abstract: A detection device for detecting transitions to the normal state in a superconducting winding, in particular in an electricity generator, and a protection device for protecting such a winding.A detection device for detecting transitions in conductors from the superconducting state to the superconducting state in a superconducting winding at industrial frequency, in particular for the stator of an electricity generator (1). The device comprises an auxiliary generator (4) for generating a low current at a frequency which is considerably higher than industrial frequency, said current being single-phase or multi-phase depending on whether the main current through the winding is single-phase or multi-phase, said auxiliary generator being connected in parallel with the superconductor winding, the device further including means (5, 6) for detecting the change in phase difference between the auxiliary current and the auxiliary voltage which occurs when the conductors of said winding switch to the normal state.

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 electrical circuit for providing electrical energy to an electric motor which operates a liquid pump. The motor and the pump are adapted to be submerged in the liquid which is pumped by the pump. The circuit disclosed herein senses the phase angle between the current and the voltage applied to the electric motor. When the phase angle indicates that the motor is operating without a load, the circuit deenergizes the electric motor. Thus, the motor and the liquid pump are protected against damage. Recognizing that harmonics may exist in the current flow through the motor, the circuit provides for obtaining a filtered signal proportional to the fundamental frequency of the current flowing through the motor. Thus, an accurate measurement of the loading of a motor is obtained. The circuitry of this invention also provides an accurate method of compensation for applied line voltage variations, so that a change in the applied line voltage does not produce a false indication that the motor loading has changed.

Abstract: An indication that a motor has reached full speed operation is produced by generating an up to speed signal based upon measurement of the phase angle between the voltage applied to the motor and electric current flowing to the motor. A motor up to speed detector has; means for connecting an electric motor to an electric power source; means for measuring the time interval between the event of voltage applied to the motor crossing zero and the event of current flow to the motor reaching zero to obtain a measured value of current lag; and, means for comparing successive measured values of the current lag at predetermined time intervals after electric power is applied to the motor as the motor is started, and for generating a signal indicative that the motor has reached an up to speed condition in the event that successive measured values of the current lag increase.

Abstract: An apparatus for visually indicating abnormal phase relationships between incoming or outgoing phases for a plural phase device, comprised of a plurality of light emitting means interconnected between phases by a logic circuit arrangement whereby the various combinations of on/off indicators present a coded, visual presentation representing the specific mismatch condition of the network. The invention encompasses the concept of incorporating the indicating circuitry within the multiple phase device enclosure and providing an aperture in the enclosure so that the indicators may be viewed without the necessity of gaining access to the interior of the device and exposing individuals to the danger of high voltage/current circuits.

Abstract: A phase loss detection circuit for a three phase electrical system providing three phase power as to a motor, the three phase electrical being subject to a phase loss condition and a transient condition is disclosed. The transient condition includes starting transients, stopping transients or severe load transients. The phase loss detection circuit distinguishes between a phase loss condition and a transient condition and indicates when a loss of phase has occurred.

Abstract: A security apparatus adapted to a power converter, including a power converting circuit connected between a DC power source and an AC system; a phase detector circuit for detecting the voltage phase of the AC system to provide a phase detection signal; a reference signal generator circuit for generating a voltage reference in accordance with the phase detection signal; a control circuit for controlling an output voltage of the power converting circuit in accordance with the voltage reference. The security apparatus is characterized by a disturbance generator circuit for applying a disturbance to the phase detector circuit; and a detector circuit for detecting an abnormal state in which the phase or frequency of the output voltage of the power converting circuit deviates from a normal one.

Abstract: A system for sensing the phase of a three-phase AC system and detecting phase reversal and undervoltage and phase unbalance and for providing a switching function when the system is not functioning properly.

Abstract: A protective apparatus for use in an A.C. electrical power system with a circuit breaker for connecting and disconnecting first and second electrical conductors that are electrically energizable, the conductors normally having a negligible phase difference of electrical energization when the circuit breaker is closed, and the circuit breaker having auxiliary contacts defining the state of the circuit breaker as open or closed. The protective apparatus includes a circuit responsive to the auxiliary contacts for producing a first signal representative of the state of the breaker as open or closed and another circuit connected to the circuit for producing the first signal and operable when the breaker is closed for generating a second signal when the phase difference of electrical energization of the first and second electrical conductors exceeds a predetermined value. A further circuit provides an indication of malfunction of the circuit breaker when the second signal occurs.

Abstract: A power active filter circuit for an electric power system includes a reference generator for producing a plurality of balanced, constant amplitude, positive sequence, AC reference voltages, each being phase-locked to a corresponding phase voltage of the power system. Error signals are produced by subtracting the reference voltages from their corresponding phase voltages and a plurality of correction signals, which are proportional to the error signals, are combined with the phase voltages to produce a plurality of output voltages having substantially only a fundamental component.

Abstract: It is desirable to provide remote digital protection of distribution transformers. This specification discloses a protection system able to measure and compare increases in both negative and positive phase reference currents on a distribution cable feeding a transformer and to trigger a circuit breaker to isolate the cable only if the negative sequence current increase exceeds a predetermined proportion of any simultaneous positive sequence current increase. Consequently, engergizing with a 12.5% unbalance current has been found possible without false tripping.

Abstract: A method for sensing real load unbalance in an electrical power system having at least two clock based power sources which are connected for parallel operation combines a real load difference current signal, proportional to the difference in real load currents in corresponding phases of the power sources, with a phase angle signal which is proportional to the phase difference between an external clock signal and an internal clock signal of one of the power sources, to produce an error signal. When this error signal exceeds a predetermined threshold level, a trip signal is produced to indicate that an excessive real load unbalance situation exists.

Abstract: A characteristic timer, for a protective relay which provides protection for a portion of an AC transmission line, exhibits a phase characteristic which is always integrating and a ground characteristic which changes from non-integrating to integrating as a function of input signal pulse width and a preselected cut off time. The ground characteristic begins to integrate upon expiration of the preselected cut off time or if the input signal pulse width exceeds a predetermined check level of magnitude during the cut off time. If the pulse width magnitude of the input pulse is less than or equal to the predetermined check level magnitude during the cut off time, the characteristic will be non-integrating.

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: In a digital distance relay, the distance measuring operation is performed only regarding the phase on duty in the third step if there is no fault, and it is performed regarding either the third and first steps or the third and second steps if a fault is detected within the third step. Thereby the processing time for the distance measuring operation may be reduced is that corresponding to two steps per sampling.

Abstract: A phase comparison type ground distance relay for a predetermined phase of three-phase AC transmission line includes a phase coincidence detector responsive to phase coincidence between an operating signal and a plurality of polarizing signals. Zero suppression networks are utilized for deriving second and third polarizing signals in order to improve discrimination between internal and external faults; thereby increasing the reliability of the relay operation and the security of the protection system. The second polarizing signal comprises that portion of a signal which exceeds a predetermined threshold value and which is related to the product of a signal proportional to the net current flowing in all three phases of the power system and the positive sequence replica impedence of the transmission line.

Abstract: Direct transfer trip apparatus for sharing a common active communication channel utilized for signal transfer between at least two electromechanical units which form a current differential protective relay for protecting at least one power line in a power system network is disclosed. Each electromechanical unit includes an operating relay coil for effecting an interruption of current through the protected power line when an internal fault of the power line is detected. The direct transfer trip function induces signals to be transmitted through the common active communication channel either upstream or downstream from a faulted power line section where a breaker has failed to open. These direct transfer trip signals are supplied directly to an upstream or downstream breaker unit to operate the breaker to interrupt current through the faulted section independent of the energization of its corresponding operating relay coil.

Abstract: Active pilot wire apparatus for replacing a passive continuous metallic wire pair coupling between the electromechanical units of a conventional electromechanical pilot wire protective relay is disclosed. For the protection of a power line section, an electromechanical unit is coupled to each end thereof. Each electromechanical unit includes an operating relay coil which when energized operates breaker contacts to interrupt current through the protected power line section. A signal representative of the potential across the operating coil of each electromechanical unit is transmitted through an active communication channel to the other electromechanical unit where it is buffered by a high impedance amplifier. In each case, the output signal of the buffer amplifier is representative substantially of the corresponding operating relay coil potential. An impedance element is coupled between each buffer amplifier and the other operating relay coil.

Abstract: A circuit for providing a multiphase digitally synthesized sinusoidal output signal representative of a predetermined symmetrical component set of a multiphase source signal and having a predetermined relationship therewith is taught. The circuit comprises a phase comparator, a phase shifter and a synthesizer. The phase comparator produces an output representative of the phase error in the predetermined phase relationship between the source signal and the output signal. The phase shifter has a variable frequency output for shifting the phase of the synthesized output signal in response to the phase error output signal of the phase comparator. The synthesizer digitally synthesizes at a predetermined amplitude the multiphase sinusoidal output signal. The synthesizer is responsive to the phase shifting output of the phase shifter so as to decrease the phase error between the source signal and output signal.

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: A control system for protecting a computer system against external fault conditions, including, in combination, circuits for monitoring and reacting to a plurality of power supply fault conditions, circuits for monitoring and reacting to a plurality of environmental fault conditions, circuits for monitoring and reacting to unauthorized access fault conditions, and circuits for driving off the supply of 3-phase power to the computer system in response to any one or more of these fault conditions. The invention also includes the various monitoring and reacting circuits in specific subcombinations.

Abstract: A protective relay which hardly makes maloperation in itself regardless of mixing of low-order higher harmonics in its at least two sinusoidal input signals comprises a first and a second phase detection comparator generating two different-phase square signals indicative of the phase difference between the sinusoidal input signals, a first and a second timer receiving the square signals generated from the first and second phase detection comparators respectively and generating their output signals as a result of comparison between a first period of time and one of the periods or the period of presence or absence of the square signals, a third timer receiving the same square signal as that applied to the first timer and generating its output signal as a result of comparison between a second period of time and the other period or the period of absence or presence of the square signal, a fourth timer receiving the same square signal as that applied to the second timer and generating its output signal as a result

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.