Abstract: A fault protection arrangement for electric power distribution systems includes a plurality of power sources connected to a distribution bus through circuit breakers and a plurality of loads connected through switches to the distribution bus, along with fault sensors in each of the power source lines and load lines and a control means responsive to detection of a fault in a load line to open the circuit breakers in the power source lines connected to the distribution bus and then to open the switch in the load line containing the fault and then to reclose the circuit breakers in the power source line to resume power flow to unaffected loads. The embodiments provide automatic fault isolation and automatic system realignments using a minimum amount of circuit interrupting devices in conjunction with a distributed control system. The embodiments eliminate fault coordination difficulties and improve power continuity as compared to conventional hierarchal protective schemes.

Abstract: The invention relates to an automatic reset circuit for detecting much faster transient voltage variation between the supply voltage (VDD) and the electric ground (GND) of an electric system with noise and disturbance. The automatic reset circuit of the invention includes a plurality of detecting units, a plurality of voltage-couple devices connected with the detecting units, and a decision unit with an output port. The decision unit and the voltage-couple devices are also connected. The automatic reset circuit of the invention can detect nanosecond transient voltage variation between the supply voltage and the electric ground, and a reset is then enabled for protecting the inner circuits and surviving the normal operations of the electric system.

Abstract: A fault protection arrangement for protecting power conversion circuits, for example switch mode power supplies and the like, from overcurrent and short circuit faults. The fault protection arrangement includes multiple fault protection features, for example soft-start delay, fault delay and automatic reset, with the timing of each of these three features capable of being set independently of the other two while minimizing integrated circuit (IC) pin count and also minimizing the number of external components required for programming the timing of these features. The fault protection circuit may be used to advantage with any power conversion regulator topology.

Abstract: An installation for power transmission by high-voltage direct current has at least two converter stations which are interconnected by a dc line (DC), at least one station (SR1) having a line protection device (LP) adapted to detect a ground fault on the dc line and, when a ground fault is detected, to achieve a reduction of the voltage (U.sub.D) and the current (I.sub.D) of the line and thereafter to make a restart attempt. The installation has, in addition, a detection circuit (FD) for detection of a permanent low-impedance ground fault on the dc line. The detection circuit is activated after an intervention by the line protection device. During a detection interval, the detection circuit causes one of the stations (SR1) to feed a current into the line.

Abstract: The present invention provides a system and method for integrated reclosing of circuit breakers in a power substation by providing a programmable controller which is programmed to detect the opening of a circuit breaker and initiate a reclosing window during which time it can generate a command signal to the opened circuit breaker commanding it to close.

Abstract: A circuit recloser that limits current through a power line when a fault condition occurs. The recloser includes a circuit interrupter that is switchable between a closed state, in which current is permitted to flow through the power line, and an open state, in which the current is interrupted. The interrupter switches to its open state in response to a fault condition, such as a current surge. The recloser also has a movable member that is operatively coupled to the interrupter for resetting the interrupter to the closed state from the open state when the movable member is moved. The movable member is configured for being remotely movable to close the interrupter. Preferably the recloser includes an electric drive to remotely move the movable member from a remote station, and a projection extends from the movable member to enable manual movement thereof. The movable member includes a shaft which the electric drive rotates by turning a slotted hub coaxially about the shaft.

Abstract: A power operator for switchgear and the like is provided that is capable of either power or manual operation without the necessity of any decoupling or mode selection. The power operator is compact and easily affixed over a manual operating shaft of switchgear. The manual drive capabilities are always coupled for operation without any backdriving of the power source. The power operator includes a drive output affixed to the switchgear operating shaft, a manual operating shaft, and an arrangement for selectively coupling a power-driven input to the switchgear operating shaft. In a specific arrangement, the control arrangement of the power operator senses the position of the drive output and also senses the current drawn by the drive source. When controlling switchgear having a stored energy mechanism, operating positions are detected by sensing the tripping of the stored energy mechanism via the sensed current through the drive source.

Abstract: A power-line trip circuit models the transient characteristic of a change in load (e.g. appearance of a fault current, or switch-on to a normal load) and compares the current actually flowing in the power lines with this modelled or simulated transient. Line currents that do have a transient component but do not exceed normal limits are not then sufficient to trip a circuit breaker associated with the power lines, whereas transient-bearing currents that do exceed such limits, i.e. fault currents, are recognized as such and the circuit breaker is tripped. This circuit allows fast, reliable tripping even in the presence of a substantial transient overshoot.

Abstract: An improved auto-reclosing dead time control apparatus and a method thereof for a transmission cable protection relay system which is capable of providing an on-line stability evaluation method which is capable of controlling the dead time of the transmission cable automatic reclosing relay in accordance with the stability margin, which includes an electrical system for controlling an automatic reclosing operation in accordance with a variation of a transmission cable failure dead time, a transient stability margin evaluation means for evaluating a transient stability margin in accordance with a failure information inputted from the electrical system, and a reclosing relay means for varying the dead time in accordance with a transient stability margin evaluated by the transient stability margin evaluation means.

Abstract: Isolation circuitry for automatically disconnecting a load from a source upon detecting a short and for automatically reconnecting the load to the source after the short circuit clears. The isolation circuitry includes a first node connected to a second node via a first transmission path, and a third node connected to a fourth node via a second transmission path maintained at a different voltage than the first transmission path. There is a switch between the nodes on the first transmission path, and a sensing circuit that is connected between the first and second transmission paths. The sensing circuit includes a current generator that induces a fault indicating current into a load between the first and second transmission paths and monitors the fault indicating current for an increase over a threshold defined by an operating voltage setting circuit when the load impedance falls below a lower limit indicating a short circuit.

Abstract: A reclosing relay in accordance with the disclosed invention comprises a reclose initiate (RI) input and a drive to last reclosure (DTLR) input, and an output at which a close signal is provided to effect the reclosure of a circuit breaker associated with the reclosing relay. The reclosing relay is operative when it receives a first RI signal at its RI input to provide the close signal to the associated circuit breaker substantially immediately or with time delay as programmed by settings. The reclosing relay is operative when it receives a signal from a second RI contact at its DTLR input to provide the close signal to the circuit breaker only after synchronism is identified between the line voltages on either side of the associated circuit breaker.

Abstract: The base of a thermal shutdown bipolar transistor having a V.sub.BE(on) which decreases with increasing temperature is biased with a bias voltage V.sub.PTATbias which increases proportionally with increasing absolute temperature. By supplying the base of the thermal shutdown transistor with a bias voltage V.sub.PTATbias which increases with increasing temperature rather than a bias voltage that remains constant or decreases with increasing temperature, the temperature at which the thermal shutdown transistor turns on is made more predictable and the thermal shutdown transistor is made to turn on more sharply at a desired thermal shutdown temperature. The bias voltage V.sub.PTATbias may be generated by driving a current which increases proportionally with increasing absolute temperature across a resistor. Current sources employing feedback control loops are disclosed for generating such a current. Startup current sources are disclosed for starting control loop operation.

Abstract: The instant invention is a protection device for electrical equipment operating on a single or three phase alternating current power supplies. The device consists of an electrical circuit having at least one relay which is energized by at least one leg of an incoming power supply. The relay is energized by either a manual toggle or an automatic timer when the power supply is fully operational. Thus, upon placement of the device into an electrical line, power restoration after a power interruption is made possible only by manual initiation of the toggle or by an adjustable timer that counts down a preset period of time before initiation.

Abstract: A reset circuit for an overload relay includes a timing circuit coupled to a switching circuit for automatically resetting the relay a predetermined time after a trip. The timing circuit includes a capacitor and a resistor in parallel with a reset coil. The capacitor is charged during normal operation and begins to discharge through the resistor following a trip at a first rate determined by the size of the resistor. The switching circuit includes a pair of transistors, a pair of capacitors and a pair of resistors. When the capacitor in the timing circuit has discharged a predetermined amount following a trip, the switching circuit is triggered and couples the capacitor to ground through one of the transistors, causing a rush of current through the reset coil sufficient to reset the relay.

Abstract: The Hall-Effect Arc Protector is used to protect sensitive electronics from high energy arcs. The apparatus detects arcs by monitoring an electrical conductor, of the instrument, for changes in the electromagnetic field surrounding the conductor which would be indicative of a possible arcing condition. When the magnitude of the monitored electromagnetic field exceeds a predetermined threshold, the potential for an instrument damaging are exists and the control system logic activates a high speed circuit breaker. The activation of the breaker shunts the energy imparted to the input signal through a dummy load to the ground. After the arc condition is terminated, the normal signal path is restored.

Abstract: An electrically operated actuator stores power in a capacitor for returning the actuator output element to a preselected position upon power failure. The actuator has a controller having input power terminals connected across the capacitor and control terminals for controlling the power applied from the input power terminals to the motor which comprises the actuator's prime mover. A sensor monitors the presence of power provided to the controller's input power terminals. When failure of this power is sensed, the capacitor current flows to the controller, and the sensor applies signals to an override circuit of the controller causing the controller to apply current from the capacitor to the actuator motor in a way which drives the actuator toward the preselected position. A properly selected capacitor is capable of supplying adequate current over a period of time sufficient to return the actuator to the preselected position.

Abstract: An apparatus for restarting an inverter after momentary interruption by detecting a power restoration after a momentary outage of a power supply that supplies power to the inverter for driving a synchronous motor. The apparatus includes a frequency detecting portion that detects the frequency of a terminal voltage of the synchronous motor, a phase difference detector that detects the phase difference between the terminal voltage of the synchronous motor and the output voltage command value of the inverter, a phase controller that performs synchronous control so that the frequency and phase of the output voltage command value of the inverter and those of the terminal voltage of the synchronous motor agree with each other, and a restarting portion that restarts the inverter under the condition that the synchronization has been completed after the power restoration of the power supply.

Abstract: A solid state power controller is automatically reset if an overload trip occurs during a start-up delay period. If an overload trip occurs during load starting, the SSPC remains tripped for a reset delay period, and thereafter the SSPC is automatically reset, thereby allowing the starting process to continue by heating a lamp filament, accelerating a motor, etc., without indicating a system fault to an operator. At the expiration of the start-up delay period, the SSPC no longer automatically resets in response to an overload condition.

Abstract: An auto-recloser circuit-breaker has three vacuum interrupters driven from a single bistable magnetic actuator which is powered by a first lithium sulphur dioxide battery under control of an electronic protection relay which is powered by a second lithium sulphur dioxide battery. The drive mechanism, actuator and relay are designed to minimize current consumed by the batteries so that the recloser may be self-powered for its full life by these batteries independent of the power line in which it is connected.

Abstract: The present invention provides a circuit breaker trip unit configured to operate with a plurality of different plug-in display units. The display unit includes a memory which stores data representative of the particular display unit, and which allows the trip unit to automatically adapt to communicate with the display modules. The trip unit includes a processor and programming which permits a bi-directional flow of data between the units, such as display data and control data.

Abstract: A plug presence sensor comprises an LED and a light sensor in the form of a photo-transistor which senses presence of a plug in a receptacle. The sensor is monitored by a microcontroller to control latching of a relay. The microcontroller de-energizes the relay, so that no power is present at the receptacle, when no plug is inserted. When the plug is inserted, then the microcontroller causes the relay to be energized to provide power to the receptacle. The microcontroller is preprogrammed to communicate with a remote master controller. In the event that a loss of communication occurs between the microcontroller and the master controller, the microcontroller automatically de-energizes the relay so that no power is present at the receptacle. A communication error output signal is connected to an override circuit including a capacitor which differentiates an edge of the communication error signal to inject a pulse onto the plug presence sensor signal which simulates removal and reinsertion of the plug.

Abstract: An overcurrent protection circuit is provided with a counter which permits a preselected number of reinitiations of current following the detection of an overcurrent condition. Each stoppage of current in response to the detection of an overcurrent condition is followed by a predetermined time delay and a subsequent reinitiation of current. After the predetermined number of reinitiations, current is permanently stopped from flowing between first and second circuit points until a manual reset occurs.

Abstract: An automatic protection and recovery method for a telephone line interface circuit is described. The interface circuit monitors current on the line, and in the event of a fault producing an excessive current a protection relay interrupts a connection of the interface circuit to the line, and the interface circuit monitors common mode voltage on the line. The interface circuit is reconnected in response to the monitored voltage being below a relatively high threshold. If a second interruption results, the interface circuit is then reconnected in response to the monitored voltage being below a lower threshold. If a further interruption results, the interface circuit enters a ground fault recovery process. The method facilitates protection and rapid recovery from arbitrary fault conditions on the telephone line.

Abstract: A battery drain limitation circuit, for use in engine-powered vehicles and equipment that rely on a battery for starting the engine and for operating accessories, disconnects the battery from all loads when the battery voltage falls to a level below which the battery charge may be insufficient to start the engine. The circuit is rendered inoperable, when the engine is running, by means of a microphone that detects engine noise. The circuit includes a reset mechanism that reconnects the battery to all loads. The reset mechanism may be automatic or manually actuated. A timing circuit delays the disconnection for a period of time sufficient to start the engine. The drain limitation circuit employs a latching relay that, in its preferred embodiment, includes front and rear coils in tandem, axially separated by a collar with an internal detent. A front plunger and a rear plunger are disposed for axial movement within the coils and the collar.

Abstract: The electronic trip device comprises a device for selecting the faults which are to bring about locking of the circuit breaker contacts in the open position. When a fault in the power supply system protected by the circuit breaker leads to a trip, the trip device orders locking if this fault is one of the faults selected by the selection device.

Abstract: A main controller installed in a distribution substation of an electric power system sends a request signal to each of section controllers installed in individual section switches upon detecting a distribution line fault. Each of the section controllers performs fault detection individually. Each section controller judges whether its associated section switch is dividing the distribution line between faulty and normal line sections on the basis of fault detect signals from the other section controllers. If it is judged that its associated section switch is dividing the distribution line between faulty and normal line sections, that section controller opens its associated section switch.

Abstract: A number of arrangements for protecting an electrical circuit from an electrical overcurrent are disclosed. In the arrangements the base or gate of a switching transistor (4, 101, 161, 222, 401) is held in a voltage divider, one arm of which comprises a control transistor (6, 102, 162, 222, 404) whose base or gate is itself held in a voltage divider. When an overcurrent is experienced the control transistor switches on causing the switching transistor to turn off. The arrangement may include a shunt switching circuit to shunt the overcurrent across the load. It may include a resetting circuit that will attempt to reset the switching circuit after the overcurrent has been experienced. In one embodiment the arrangement includes means such as a battery, dc--dc voltage converter or Seebeck device in order to reduce or eliminate any initial voltage drop across the switching circuit.

Abstract: Method and apparatus are provided responsive to the circuit parameters at one or more locations of an electrical power transmission and/or distribution network for detecting protective device operation. The detection of the protective device operation is utilized to locate faults and also to ascertain the status of protective devices. This information is useful in automated power systems for desirable isolation and sectionalizing of faults for optimum restoration of the network. A fault detection unit of the present invention is responsive to sensed circuit parameters and provides at least first and second outputs indicative of protective device operations that open the circuit. The first output is provided upon the occurrence of an overcurrent followed by the loss of a circuit parameter, such as voltage, for a specified time duration. In a preferred arrangement, the timing for a specified time duration is started when the overcurrent ends.

Abstract: An electronically controlled recloser for an electrical power distribution system is powered by at least one current transformer coupled to give an output in response to power line current. A voltage is stored on a large and a small capacitor in response to the line current and is compared with a reference voltage for determining the level of line current. When abnormally high levels of current appear on the line, it is opened for a short period of time. The energy stored on the capacitors is supplied to power the recloser during low line current conditions. At an end of a given time period following the opening of said line, the recloser recloses the line. If the abnormal condition persists, the recloser again opens and closes the line. When there is a surge of line current, the large capacitor is effectively removed from the circuit so that a response will not be delayed while the large capacitor charges; therefore, the charge on the small capacitor provide a quick start for immediate response.

Abstract: A circuit arrangement for providing a store of energy for actuating an electrically operable device, incorporating a reservoir capacitor, comprising a transformer having low resistance windings, the primary winding of which is connectable to an alternating current high voltage supply in series with at least one resistance capacitor, and the secondary winding of which is connected to the reservoir capacitor through a rectifier, the capacitor being connectable to an electrically operable device, with the turns ratio of the transformer such as to produce a secondary current of sufficient magnitude to charge the reservoir capacitor in the time available for successive operations or successive operational sequences of the device.

Abstract: A circuit breaker system uses a microprocessor for calculating at least one function of a measured current flow.

Abstract: A microcomputer based reclosing relay performs a number of sequences to generate a succession of reclosure signals for a circuit breaker at timed intervals. The digital processing unit of the relay maintains flags, counts and running times for generating the succession of timed reclosures in a volatile memory. Periodically, these flags, counts and running times are copied to a non-volatile memory such as an EEPROM. Upon restoration of power following an interruption of power which results in loss of the contents of the volatile memory, the digital processing unit recopies the flags, counts and running times saved in the non-volatile memory back into the volatile memory, so that the relay can resume generating the succession of reclosures from the point at which power was lost. The flags and counts are copied to the EEPROM only when they change state, while the running times are only saved once a second to prolong the service life of the EEPROM.

Abstract: Apparatus for improving the performance of conventional electromagnetic reclosing relays under continuous lower magnitude ground or phase faults in electrical power distribution systems. An incomplete sequence relay is connected to the reclosing relay to render the timing drum or cam of the reclosing relay operative when the contacts of the circuit breaker are open, and to reset the reclosing relay after a selected time interval when the breaker is closed. This arrangement prevents timing problems associated with lower magnitude faults which otherwise keep the reclosing relay from reaching its lockout condition.

Abstract: Electronic circuit breakers safeguard a load connected to a power supply against damage from overload conditions. These circuit breakers interrupt flow of overload currents to the load by instantaneously reducing flow of such current from the power supply to the load to a harmless residual current when that electric current flow exceeds a predetermined value. These breakers also avoid downtime after cessation of such a condition by electronically monitoring that residual current to determine when it is safe to restore electric operating current flow to the load. Flow of electric operating current from the power supply to the electronic equipment is restored in response to the latter determination. Preferably, the monitored residual current is used for automatically switching the electronic circuit breaker and the flow of electric operating current electronically back on, when the electronic monitoring has determined that the overload condition has ceased to exist.

Abstract: A reclosing relay for use in an electrical power system with a circuit breaker for clearing line faults by tripping and reclosing. The breaker has auxiliary contacts defining the state of the circuit breaker as open or closed. The reclosing relay includes a circuit responsive to the auxiliary contacts for producing a first signal representative of the state of the breaker and another circuit for generating a second signal when a loss of power to the reclosing relay is anticipated.

Abstract: A transmission line between terminals of a three-terminal station is branched by a branching unit and power is transmitted between the terminals of the three-terminal station and a power feed system in the transmission line including: a switch for switching a power feed line feeding power to a repeater between a both-end power feed mode and a single-end power feed mode; and connection holding means for holding a power feed connection state without change upon an occurrence of a failure.

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 method for reclosing a temporarily opened circuit breaker in a manner which assures that generation of unwanted overvoltage stresses is avoided during the reclosure process. An oscillating line voltage typically develops in a shunt-compensated line after a circuit breaker connecting the line to a voltage source is opened. When the circuit breaker is reclosed the source voltage and the oscillating voltages must be properly phased to avoid the overstressing problem. In operation, the polarities of the feed voltage and the oscillating line voltage are detected and the instant when the circuit breaker may be reclosed is calculated. The periods T.sub.L and T.sub.S of the line voltage and the feed voltage are measured. Also measured is the time .DELTA.T which elapses from a zero crossing of the line voltage waveform to a subsequent zero crossing of the feed voltage waveform having the same phase angle as that of the line voltage zero crossing. The circuit breaker is reclosed upon satisfying the relationship:.

Abstract: A source of high-frequency voltage is applied directly across a series-resonant L-C circuit. A fluorescent lamp and a Varistor are both connected in parallel with the capacitor of this L-C circuit. The Varistor is operative: (i) to prevent the series-resonant L-C circuit from ever overloading the voltage source, and (ii) to limit the magnitude of the voltage provided across the lamp to a level appropriate for rapid-starting thereof. When power is initially applied, the lamp's cathodes are cold and the lamp does not conduct; which implies that a significant amount of power is dissipated in the Varistor. For sake of cost-effectivity and energy conservatiion, if the lamp fails to conduct for about 25 milli-seconds, a control means provides a short circuit across the capacitor. The resulting short circuit current is used for heating the fluorescent lamp cathodes. After about 1.

Abstract: The device includes two detectors of overvoltage (8, 9) each connected between a respective one of a pair of power line conductors (1, 2) and a respective input of an arrester (7). The outputs of the detectors are connected to an OR-gate (10) the output signal of which is applied to a threshold gate (12). The output of gate (12) is connected to a first monostable trigger (13) having a first time constant and controlling, through a latch gate (14), a bipolar insulating device (3, 4) isolating the load (90) from the power network. In order to achieve the automatic reconnection of the load after each perturbance, the output of the latch gate (14) is also connected to a second monostable trigger (16) having a second time constant higher than the first, and to the clock input of a counter (15) having its return-to-zero terminal connected at the output of the second monostable trigger. Preferably, an integrator (11) is connected between the OR-gate (10) and the threshold gate ( 12).

Abstract: An A.C. overload current sensing, remote power controller of minimum size and weight and integral construction. Current rate sensing wound toroids are used that are small enough to fit around the line terminal studs without having to enlarge the prior insulator space available therein. The electronic overload current detecting and tripping control circuit is replaced by a pair of modules, detector and control modules, having improved performance and a shape and size such that they fit within the relay housing alongside its operating magnet. The detector module has integrator means for converting current rate of change signals into current magnitude indicative signals thereby enabling use therewith of rate sensing wound toroids of about one-tenth the size of equivalent current transformer wound toroids.

Abstract: A distribution line powered switchgear control is provided which reliably initiates switchgear operations with stored energy. Stored energy is preferably maintained in a plurality of devices including a power capacitor. The power capacitor is preferably charged by a fast arming circuit which preferably selects among a plurality of independent power sources. The switchgear control additionally isolates sources of stored energy so that depletion of one does not affect the others. Further the switchgear control will preferably prevent closing of the switchgear unless sufficient energy is stored to allow the control to initiate a subsequent opening of the switchgear.

Abstract: A method of isolating a spur line of an electrical power system protected by a multi-shot resetting circuit breaker wherein at least two successive current surges in the spur line which activate the circuit breakers are detected. In response to the detection the spur line is isolated during a subsequent current dead period.A sectionalizer is described for isolating a spur line of an electrical power system protected by a multi-shot resetting circuit breaker. The sectionalizer comprises a metal casing 22 providing a current path across a fuse mounting 10 while the sectionalizer is in a conducting position. An electrical circuit 23 inside the tube detects at least two successive current surges in the casing and during the following dead period actuates a chemical actuator 14 to trip the sectionalizer out of its conducting position.

Abstract: A synchronism check relay includes both a high set and a low set slip cut-off circuit. The low slip cut-off setting is based upon the maximum slip frequency that can be tolerated and still allow reclosing. The high slip cut-off setting is a function of the maximum phase angle difference permissible between the voltages on the bus and line sides of the circuit breaker, and the time that the line is de-energized.

Abstract: A microprocessor based recloser control has a microcomputer for causing trip and close operations of a recloser in response to the conditions of the power distribution lines being protected and operator commands. The microcomputer may be overridden by a mechanical switch in the recloser control. If power to the recloser control is lost, the microprocessor will continue to function with power storage means for a limited duration. Towards the end of that duration, this microcomputer will power down the microprocessor in an orderly manner allowing automatic return to its functions when power is restored. After the microprocessor is no longer functioning, a secondary overcurrent trip circuit is relied upon to cause a trip operation of the recloser for extended durations of power outage. The secondary overcurrent trip circuit can be disabled by the microprocessor.

Abstract: An overcurrent relay comprises an input transformer (7), a rectifying circuit (8), a level detecting circuit (9) for providing an operation signal (S.sub.1) when a direct current signal voltage (E) exceeds a predetermined value, a determining means (10 to 15) for determining a time period of at least the positive and negative components of an ac signal voltage (V.sub.1) for providing a determination signal (S.sub.6) when the determined time period exceeds a predetermined time period, and a blocking means (16 and 17) responsive to the determination signal (S.sub.6) for blocking the operation signal (S.sub.1) from being output. In the case where the alternating current input current (I) and the ac signal voltage (V.sub.1) involve an attenuated direct current component due to magnetic saturation of a current transformer and the like, the reset time period of the operation signal (S.sub.1) is prolonged, while that time period of the ac signal voltage (V.sub.

Abstract: When the positive-phase voltage of one terminal of a transmission line involved in a fault detected by a positive-phase relay exceeds a predetermined value, an output is supplied to the reclosing instructing device from an AND circuit to first reclose this terminal. When it is less than the predetermined value, this terminal is reclosed only if reclosing of the other terminals have been successfully completed.

Abstract: A timing controller which supervises the reclosure of a fault responsive circuit breaker which includes a plurality of selectable switches for developing signals representing the reset and reclose delay times for the recloser relay operatively associated with the fault responsive circuit breaker; a plurality of multiplexers for receiving the signals developed by the selectable switches and for developing serially formatted digital words in accordance with such signals for delivery to an output controlling multiplexer; a first counter assembly for regulating the output of the output controlling multiplexer in accordance with the condition of the recloser relay; a storage device for receiving and storing the output of the output controlling multiplexer; and a comparison device for comparing the stored output of the output controlling multiplexer with a second counter assembly which develops a timed output signal.

Abstract: A reclosing system for d-c feeder circuit breakers used on transit systems is disclosed. Circuit breaker closure is prevented when the feeder circuit voltage is in a predetermined voltage range and when the feeder circuit impedance is less than a given value, which is less than the impedance which would be presented by a parked train in a deenergized portion of the transit rails. A Wheatstone bridge is inserted into the circuit during the load impedance measurement. The Wheatstone bridge circuit is compensated for positive or negative rail return voltage. The automatic reclosing scheme is locked out after two closures of the circuit breaker followed by automatic tripping within six minutes, or by twelve load impedance measurements, which are performed within three minutes and which all fail to lead to a circuit breaker closure.

Abstract: A circuit is provided for detecting a low power condition which is undesirable and effectively turns off a computer system to prevent incorrect operation thereof. The circuit does not turn on the computer system until the correct power condition is achieved. The circuit is also sensitive to the power condition to establish the time duration permissible for causing the computer system to be turned off.