Abstract: The disclosure is directed to systems and methods by which the lifetime, e.g., remaining life or amount of life used, of variable use items, such as rechargeable batteries, battery relays, vehicles and power tools, can be determined that takes into account the conditions of the use of the item. The systems and methods involve an algorithm that can be described as accumulating points based on the real time utilization of the item, e.g., rechargeable battery, battery relay, vehicle, or power tool, and when an agreed-upon number of points have been accumulated, the item can be considered to be at end of life or end of warranty.

Abstract: A solenoid plunger movement detection system and method can include: detecting current supplied to a solenoid with a current sensor; converting the current supplied to the solenoid into a digital signal with a counter coupled to a first comparator; detecting a peak within the digital signal with a peak detector; comparing the peak to the digital signal with a second comparator coupled to the peak detector; measuring a dip from the peak and measuring a trough with the second comparator; generating a fault when the peak and the trough indicate a smooth current ramp to the solenoid; receiving configurable parameters for processing the digital signal with a signal processor; and providing configurable parameters to the counter, the second comparator, the signal processor, or a combination thereof with an interface.

Abstract: A characteristic of edible oil may be evaluated using a spectrometer. For example, optical reflectance data may be obtained from edible oil in situ in a frying apparatus housing the edible oil, the reflectance data corresponding to a specified range of infra-red wavelengths. A model profile corresponding to the characteristic being assessed may be obtained, such as from a repository housing a secured library of such profiles. The model profile may define a regression vector for use in transforming the reflectance data to generate a value corresponding to the characteristic being assessed. A criterion may be applied to the value to establish a simplified representation of the characteristic for presentation to a user for assessment of oil quality.

Abstract: A method and system for monitoring a state of a relay switch. The method applies a voltage signal to a solenoid of the relay switch for actuation of the relay switch, monitors over time current flowing through the solenoid after application of the voltage signal, and calculates a back-emf voltage impressed on the solenoid based on an inflection in the current occurring as a plunger of the relay switch moves. The system includes a voltage source, at least one solenoid solenoid having a plunger, a switch connected to the plunger, and a controller configured to data log the voltage applied to the solenoid and the current flowing through the solenoid upon application of the voltage.

Abstract: A power contact EoL predictor includes a pair of terminals adapted to be connected to a set of switchable contact electrodes of a power contact; a power switching circuit configured to trigger activation of the contact electrodes based on a first logic state signal or deactivation based on a second logic state signal; a contact separation detector determining a time of separation of the switchable contact electrodes of the power contact during the deactivation, and a controller configured to generate the second logic state signal to trigger the deactivation, and determine a stick duration associated with the set of switchable contact electrodes. The stick duration is based on a difference between a time the second logic state signal is generated and the time of separation during the contact cycle. The controller generates an EoL prediction for the contact electrodes based on the determined stick duration for multiple contact cycles.

Abstract: An apparatus and method of detecting movement of a plunger of the solenoid includes detecting a peak (IPEAK) in a current signal applied to a coil of the solenoid. A predetermined threshold is added to the current signal applied to the coil of the solenoid to generate a level shifted signal. The level shifted signal and the peak signal are compared to detect movement of a plunger of the solenoid.

Abstract: A method for diagnosing an operating state, i.e.

Abstract: A circuit that detects if contacts in an HV contactor have been welded or stuck closed. The circuit includes a controller that generates a short duration pulse signal that closes a driver switch and allows current flow through a coil in the HV contactor. The current flow is converted to a voltage by a sensor, where the voltage is received by the controller. The controller uses the voltage, such as by comparing the voltage to a stored representative voltage of the coil current for when the HV contactor is open, to determine whether the HV contactor is closed, and possibly welded or stuck closed, or partially closed. The sensor can be the driver switch or another device, such as a resistor.

Abstract: A method for determining an actuation delay time for an electromechanical relay includes capturing a current waveform of an energized coil, determining a time at which the actuation component begins to move by analyzing the captured current waveform, and calculating the actuation delay time for the relay based on the time at which the actuation component begins to move. A method for determining a state of a latching relay includes energizing the coil of the latching relay, capturing a current waveform of the energized coil, and determining the state of the relay by analyzing the captured current waveform.

Abstract: A circuit breaker electronic trip unit includes a controller, and a memory that stores a threshold tripping duration. The memory is readable by the controller. The trip unit includes a trip signal output, and an input section that receives at least one of a phase current level signal, a phase or line voltage level signal, and a contact state change signal. The trip unit activates the trip signal output and monitors the input section for a predetermined signal change. The trip unit determines a tripping duration from a timing of the activation of the trip signal output and a timing of the predetermined signal change. The trip unit compares the tripping duration to the threshold tripping duration to determine a sluggish circuit breaker operation.

Abstract: A dual mode battery charging system and method of use are provided for use in an electric vehicle. The system utilizes at least two user selectable, charging operational modes. In a first operational mode, a state of charge circuit powers on the engine/generator system whenever the battery state of charge falls below a first level and until the battery state of charge reaches a second level, where the second level is higher than the first level. In a second operational mode, the state of charge circuit powers on the engine/generator system whenever the battery state of charge falls below a third level and until the battery state of charge reaches a fourth level, where the fourth level is higher than the third level, and where both the third and fourth levels are lower than both the first and second levels.

Abstract: The rechargeable battery abnormality detection apparatus is provided with an internal short circuit detection section (20b) that monitors rechargeable battery (1) voltage change when no charging or discharging takes place, and detects internal short circuit abnormality when battery voltage drop during a predetermined time period exceeds a preset threshold voltage; a degradation appraisal section (20d) that judges the degree of rechargeable battery degradation; and a threshold control section (20c) that incrementally increases the threshold voltage according to the degree of degradation determined by the degradation appraisal section (20d).

Abstract: A method for estimating a life status of a lithium battery applicable to a portable electronic device is described. The method includes the following steps. Firstly, a plurality of lithium battery life status intervals are sectioned out by a plurality of voltage-electric quantity curves representing characteristics of the lithium battery. Then, an actual voltage and an actual electric quantity of the lithium battery of the portable electronic device are measured. Afterwards, positions of the actual voltage and the actual electric quantity in the lithium battery life status intervals are determined to estimate the life status of the lithium battery.

Abstract: Forecasting the end of the service life of a relay more accurately due to the effects of the load conditions and the environmental conditions can occur through diagnosing the end of service life of the relay based on the time, until the point in time that the actual opening or closing of the relay is detected, from the point in time of the application of the power to the relay or the point in time of the end of application of power to the relay coil by the controlling portion. Forecasting the end of the service life of the relay based on time, increases accuracy because time is a value that is not affected by the external environment. Additionally, because the end of the service life is forecasted based on the actual opening/closing of the relay, not only is it possible to detect immediately a fault in the relay, but it is also possible to eliminate the effects due to individual differences.

Abstract: A valve has a valve piston, at least one coil and at least one magnetized component. An induction voltage is induced in the at least one coil, by a movement of the valve piston in the valve through a magnetic field produced by the magnetized component. A reference point is acquired, which is representative of a start of a current activation cycle of the valve. In the current activation cycle a point is determined as a function of a characteristic pattern of the induction voltage, which is representative of an end of a movement process of the valve piston in the valve. A current response time is determined as a function of the point and the reference point. At least one error condition is determined as a function of the response time. An error is identified, when the at least one error condition is satisfied.

Abstract: A method and apparatus for generating a status of an electrical contact pair in an electromagnetic switch by triggering an armature movement at a substantially consistent electrical phase angle, determining a magnetic lag angle between the electromagnetic switch closing and the electrical contact pair change of state, and generating a contact status using the magnetic lag angle is provided

Abstract: A contact welding detecting device includes: a relay including a first contact for permitting and breaking transmission of a first DC input potential to a first output and a second contact for permitting and breaking transmission of a second DC input potential; a relay open/close control unit that simultaneously controls to open and close the first and second contacts when welding of at least one of the first and second contacts is detected; a first potential difference detection unit that detects a potential difference between a first point at an input side of the first contact and a second point at an output side of the second contact; and a second potential difference detection unit that detects a potential difference between a third point at an output side of the first contact and a fourth point at an input side of the second contact.

Abstract: The present invention provides a method and apparatus for determining the functional status of an electromagnetic valve having a solenoid and plunger including determining the electro-mechanical switching time of a valve based on characteristics of an electrical characteristic responsive to the solenoid; comparing the valve electro-mechanical switching time to a predetermined value; and generating a valve status signal dependant on the results of the comparison.

Abstract: In a switching device, a method and device for determining the wear of the pole contacts (C1, C2, C3) actuated by an electromagnet (20) whose movement is controlled by an excitation coil (21) by the variation of a contact wear distance travel time (Tu) generated during an electromagnet closing movement, by measuring at least one electrical signal (Ip) representing the conducting state of at least one power pole, by measuring an excitation current (Is) passing through the coil (21) of the electromagnet and by comparing the electrical signal (Ip) and the excitation current (Is) as a function of time. The measured wear distance travel time (Tu) can then be compared with an initial travel time (Ti) stored in the switching device.

Abstract: A method for testing high-voltage alternating-current power switches in a synthetic test circuit has the step of connecting a high-voltage oscillating circuit in parallel to a test switch Bt in a time interval before the current zero of an interruptible high current, which is determined by a half-cycle duration (Th/2) of the oscillating current (ih) less the duration of equivalence (?tse) of the sole flow of the oscillating current as sequential current in the test switch with a stress exerted upon the switch by the homogeneous current in a direct test circuit. The sequential-current flow duration of the equivalence results, at least approximately, from the comparison of the values of common physical stress parameters acting in the test switch during the test, on the one hand, in the synthetic test circuit and, on the other hand, in the direct test circuit.

Abstract: A method for analyzing an electrical contact pair is provided. At least one of the contacts is coupled to a line-side of the contact pair, and at least one of the contacts is coupled to a load-side of the contact pair. The method includes electrically coupling the load-side contact and the line-side contact to electrical ground, applying a test voltage across the contact pair while the line-side contact and load-side contact remain electrically coupled to electrical ground, triggering a contact pair operation timer at a start of a test, detecting at least one of a first closure of the contact pair and a first opening of the contact pair using the test voltage, and determining the timing of the contact pair based upon the operation of the contact pair operation timer.

Abstract: A keyboard includes a plurality of key elements arranged in rows and columns in a matrix-like manner. Each key element has first and second break contacts which are decoupled for safety reasons and are commonly activated when the key element is actuated. An energy supply unit feeds to an evaluation unit electric energy serially via the first break contacts for each separate column and serially via the second break contacts for each separate row. In this way the location of the key element actuation can be reliably ascertained through column and row detection.

Abstract: Method and apparatus for conserving energy in a battery powered tag which comprises a battery, one or more sensors, and a transmitter. The tag may be used in a pneumatic tire monitoring system which senses and transmits tire pressure and temperature readings. The method fundamentally comprises: hibernating between transmissions by the transmitter; and reading at least one of the sensors after each of a plurality of sleep periods while hibernating. A hibernation period may be ended if one of the sensor readings, preferably tire temperature, is very low, and at least one of a plurality of qualification criteria is met.

Abstract: The invention concerns a method and apparatus for monitoring the polar compound content of a liquid bath disposed within a cooking vat to insure the liquid bath remains suitable for human consumption while in use. The invention thus teaches the use of a capacitive probe configured take an initial measurement of the dielectric constant of the liquid bath and thereby define a shutdown criterion. The dielectric constant is then continuously measured during subsequent heating cycles and compared with the initial measurement. A shutdown procedure is triggered when the difference between the initial measurement and subsequent measurements reach a predetermined threshold defined by the shutdown criteria. In this manner, the polar content of the cooking vat is continuously and automatically monitored such that operator supervision is not necessary.

Abstract: A method for fault detection in the operation of sensors with at least two decoupled signal-transmitting elements with contacts and with a closed conductor loop includes delaying, a first test output by a defined switching delay with reespect to a second test output and evaluating the input channels in accordance with a defined expectation. Faults being inferred from deviations between actual and expected signal variations and time intervals.

Abstract: A circuit and method for measuring the switch opening time, in cycles, of a medium voltage air circuit breaker. The circuit senses DC current feeding the trip coil in the circuit breaker. The timer starts a predetermined programmable time interval after the DC current starts flowing in the breaker trip coil circuit. The timer stops when the DC current stops flowing in the breaker trip coil circuit. The programmable time interval is a delay between the opening of the breaker's primary contacts and the opening of the trip coil circuit switch, and is used to determine the circuit breaker opening time from the starting and stopping of the timer. The timing device does not require connection to the circuit breaker's main power contacts.

Abstract: A test apparatus to determine the trip setting of a bimetallic element of a thermal tripping mechanism of the circuit breaker. The apparatus comprising a conveyance configured to receive and move the circuit breaker. A radio frequency induction heater positioned below the conveyance and including an induction coil operatively connected to the induction heater, wherein the induction coil is located below the bimetallic element of the thermal tripping mechanism of the circuit breaker. The radio frequency induction heater may operate with a frequency of 250 KHz to 750 KHz. The test apparatus can also include a mechanical ejection apparatus configured to remove the circuit breaker from the conveyance if the circuit breaker did not meet predetermined criteria and an electrical test apparatus configured to test the circuit breaker if the circuit breaker met predetermined criteria.

Abstract: To determine the remaining lifetime of contactor contacts, the contact spring action at the clearance gap can be determined as a substitute criterion for contact erosion, and to determine the erosion of the contact points, the change in spring action during the shutdown cycle can be measured and converted to the remaining lifetime, for which purpose, the time of the armature movement from the start of the armature movement to the start of contact opening is measured with the solenoid actuator having an armature with solenoids and associated yoke. The measured values of the time signal tk of contact opening on the load side of the switching device monitored and the time signal tA are determined by voltageless signaling of the start of armature movement. In particular for use in three-phase systems, the switching voltage is measured as a voltage change at an artificial neutral point. In the respective arrangement, a voltageless signal line is provided between the switching device and analyzer unit.

Abstract: It has been suggested that to determine the remaining lifetime of contactor contacts, the contact spring action at the clearance gap can be determined as a substitute criterion for contact erosion, and to determine the erosion of the contact points, the change in spring action during the shutdown cycle can be measured and converted to the remaining lifetime, for which purpose, the time of the armature movement from the start of the armature movement to the start of contact opening is measured with the solenoid actuator having an armature with solenoids and associated yoke. According to the present invention, the measured values of the time signal tk of contact opening on the load side of the switching device monitored and the time signal tA are determined by voltageless signaling of the start of armature movement. In particular for use in three-phase systems, the switching voltage is measured as a voltage change at an artificial neutral point.

Abstract: A method and apparatus for testing a thermal tripping mechanism having a bimetallic element deflectable in response to overload current by heating the bimetallic element by radio frequency induction heat.

Abstract: To determine the remaining lifetime of contactor contacts, the contact spring action at the gap is determined as a substitute criterion for contact erosion, and to determine the erosion of the contacts, the change in spring action during a shutdown cycle is measured and converted to remaining lifetime. With a yoke and armature solenoid actuator with a solenoid, the armature path from the start of the armature movement to the start of contact opening must be measured. The time of separation of the armature from the yoke of the contactor solenoid actuator is determined from the voltage on the solenoid. The increase in magnetic resistance of the magnetic circuit when the magnetic armature is raised is determined. In the respective arrangement with an analyzing unit for determination and display of the remaining lifetime, the analyzing unit has means for detecting and measuring the voltage on the solenoid.

Abstract: An electromagnet exhibits in its energization curve (I=f(t)) a characteristic feature or indicator, for example, in the form of a dip (1′, 2′) in the energization current. This indicator is used to control the operation of the magnet, for example, to synchronize its operation with that of another magnet. In a loom the operation of a weft stop magnet positioned next to a weft prewinder may be synchronized with the operation of a solenoid driving a valve that supplies air to the main weft insertion nozzle and/or relay nozzles. A magnet may also be controlled with reference to rated operation values so that its actual operation value coincides with the rated value or values or at least is maintained within a permissible tolerance range of rated values. The control takes place in closed loop fashion, for example, through the main loom control.

Abstract: In the functional test process for a mechanical switching element, particularly a trigger in a high-voltage power switch, a coil core (2) is set in motion by the magnetic action of a current flowing through a coil (1). The electrical pulse is cut off as soon as the derivative of the measured current characteristic reaches a particular valve. This makes it possible to stop the movement of the core (2) and the plunger (4) without triggering the power switch.

Abstract: A method and apparatus for the recognition of the state of a solenoid valve supplies an on/off control switching current to the coil of the solenoid valve. A high level of current is caused to flow through the coil for switching the device on, and a reduced level of current is applied to the coil for holding the solenoid armature in its on position. If the armature should be caused to drop off from its on position by a mechanical shock, an increase in the frequency of the switching current occurs, due to the decrease in magnetic circuit inductance. This frequency increase is detected and compared to a predetermined threshold value. If the detected frequency exceeds the threshold value, it is recognized as an armature drop off, and corrective action can be taken immediately.

Abstract: A system for detecting a gap of unknown width, the system having an RF signal generator having an output interface that outputs an RF signal and that interfaces with an input portion of a test device that is electromagnetically connected with a first surface of a gap. The system also comprises an RF signal receiver having an input interface that receives an RF signal and that interfaces with an output portion of the test device that is electromagnetically connected with a second surface of a gap. The RF signal receiver generates an electrical output to an output interface when an RF signal is detected. A processor has an input interface that interfaces with the output interface of the RF signal receiver and the processor converts the electrical signal from the receiver into an indication to the user of the presence of a gap in the test device.

Abstract: An apparatus for demonstrating and testing the operation of an arcing fault detector. The apparatus comprises an electrical circuit including line and neutral conductors connected between a power source and a load. A selector switch is movable between a first position and a second position in order to selectively route load current across either an arcing fault detector or standard circuit breaker. A pair of electrodes is positioned between said selector switch and the load for producing an arcing condition on the line conductor.

Abstract: A surface mountable reed switch, which is particularly useful for implantable devices such as pacemakers, defibrillators, drug pumps and neurostimulators. The switch includes reed contacts hermetically sealed within a tubular glass envelop, wherein the reed contacts extend through ends of the envelop to provide external contacts. A trilobular cross section mounting bar is attached to each external contact such that the reed switch can be mounted on a mounting surface such as a ceramic substrate or the like. A protective housing contains the reed switch while the attached trilobular bars extend from a side of the housing to allow communication between the switch and the mounting surface. Further, a testing apparatus is provided for evaluating how the housed reed switch will perform when installed in the implantable device and subjected to stray (must not operate) as well as designated (must operate) magnetic fields.

Abstract: A testing apparatus for testing a sample fault indicator (11) of the type which has a current sensor (15), an automatic reset, an inrush restraint feature, and an indicator display (13) that are widely used by electric utilities for fault location of overhead and underground distribution power circuits. The first objective of the testing apparatus is to test the predetermined current threshold level of the sample fault indicator (11) which is specified by the producer. It provides for the simulation of a fault current condition by means of a pulse driver circuit (99). The output response of properly working fault indicator (11) under this test will cause the indicator display (13) to register a fault state. The second object provided by this apparatus is to test the automatic resetting of the sample fault indicator (11). It provides for simulating a reset signal (105) for a controlled duration of time.

Abstract: A fusion detecting system for relays is provided for detecting a fusion of relay contacts. Two fully-interlocked or semi-interlocked relays are connected in such a manner that they operate under identical conditions, and a fused state is detected based on the states of signals sent from series-connected make contacts and series-connected break contacts of the two relays. In the case of semi-interlocked relays (R1, R2), if a make contact (r12) is fused during a current supply to a coil, the other contact (r22) remains in an open state or at a make-contact side after the current supply to the coil is cut off, and if a break contact (r11) is fused, the other contact (r21) remains in an open state or at break-contact side after a current is supplied to the relay coil.

Abstract: A method for detecting the motion and position state of a component of an inductive electric load. The component can be moved between two end positions by magnetic interaction, in which the total waveform of the drive current is divided into a plurality of states. By evaluating these individual states, comprehensive error diagnostics and a setting of operating parameters of the inductive electric load to operating conditions are possible.

Abstract: A relay device having a relay element mounted on a circuit board, the relay element having a pair of contacts which are closed and electrically conducted by a control signal of a first level and opened by the control signal of a second level to form a contact gap; an LED for emitting light toward the contact gap; a phototransistor for receiving light from the LED, the phototransistor not receiving the light while the pair of contacts are closed, and receiving the light passing through the contact gap while the pair of contacts are opened; and a checker circuit for checking if the relay device operates normally or abnormally in accordance with the relationship between an output from the phototransistor and the level of the control signal.

Abstract: A computer-controlled apparatus (1) for electrical testing of the make-and-break characteristics of electrical switches (15), including characteristics when the switches are actuated very slowly. The apparatus automatically feeds the switches into a test position (16), "breaks them in" by cycling them through many operations, and tests their switching parameters. The amount of hysteresis (54) between a switch actuator's (38) positions at actuation (30) and deactuation (56) is a criterion for sorting the switches. Switches are automatically classified and marked (14) according to their tested characteristics, and sorted into bins (28, 29). Any undesirable electrical "deadbreak" (an excessive transfer delay) during the operation of a double-throw switch's contacts is detectable by both a Timer Method and a Limit Switch Method, and faulty switches are reliably rejected. The apparatus increases accuracy in the testing of switches and reduces human errors such as those caused by fatigue.

Abstract: In a process for automatically detecting the response of an electromagnetic valve, in particular an electrovalve, an increasing testing voltage is applied to the valve and the instantaneous testing voltage at which the electromagnetic valve responds is fixed and indicated in that the monetary decrease of the current flowing through the valve is detected and utilized for fixing and indicating the instantaneous value of the testing voltage. A device for automatically detecting the response voltage of the electromagnetic valve includes an indicating device (8) which is controllable in such a way that it indicates and fixes the value of the testing voltage applied to the electromagnetic valve as soon as the valve responds to the testing voltage.

Abstract: There are provided a first switch which is switched to the on state or the off state in association with a displacement of an actuator which causes a displacement by a contact with an object and a second switch which is switched to the on state or off state later than the first switch in association with the displacement of the actuator. A switch output is produced and an abnormality is detected in accordance with the on and off states of these switches.

Abstract: A navigation system for an aircraft fitted with an autopilot, the system comprising at least one ground-based transmitter (2), receiver means (7,8) mounted in the aircraft and including two antenna (5,6) oriented such that their polar diagrams overlap and are inclined with respect to the fore-and-aft axis of the aircraft.

Abstract: A device for monitoring short circuits and overloads in electronic proximity switches of a transmission line. The device is a testing circuit which includes a current pickup which measures the current in the output circuit of a respective proximity switch which controls the output current flow by switching off or limiting the output current flow. The device also includes a circuit which provides a testing cycle for the current measurement with first and second delay times which control the output current during a short circuit or overload and a waiting time, substantially longer than the first delay time, between the start of two successive delay times. The length of the first delay time is chosen with respect to the time constant of the respective transmission line to be connected.

Abstract: A method and apparatus for testing the operability of an overload protection device for an induction motor, rapidly and without the need to mechanically load the motor output shaft. A rectifier circuit converts a standard AC input power signal to an unfiltered full wave rectified output power signal which is applied to the input terminals of the motor under test to rapidly heat the overload device to its trip temperature. The output power signal is periodically interrupted for brief periods of sufficient duration to extinguish any arcing occasioned by the opening of the overload device contacts. The period between successive interrupt periods is selected to be short enough to extinguish any such arcing before the contacts are damaged. If the contacts of the protection device fail to open within a predetermined time period, a signal is generated to indicate that the overload device has failed to operate properly.

Abstract: Electronic trip units employed within static trip circuit breakers are individually calibrated and automatically adjusted to ensure that the trip transfer characteristics are within specification requirements. A trimming network within the trip unit circuit contains a plurality of parallel resistors each separately connected within the circuit by means of a fusible link. Test input and output values are compard to idealized values that are binary-weighted within a look-up table in the test equipment computer. The percent correction required is determined and the appropriate links are interrupted to provide ideal trip response.

Abstract: Apparatus and method are disclosed for identifying and measuring random contact interruption events in a circuit interconnection device. A comparator circuit, adapted to be operated at high frequencies, identifies when an interrupt event has occurred. The comparator circuit, as a result of the interruption event, causes a high frequency counter circuit to count clock pulses. The count in the counter circuit is continuously applied to an RAM memory circuit, write-enabled at an addressed memory location. After the interruption event is terminated, the RAM memory circuit is no longer write enabled at the addressed location and the addressed location is changed (incremented) in preparation for the next event. The counter circuit is also reset to zero in preparation for the next interruption event. The number of counts from a clock unit having a known frequency provides the duration of the interruption event. With the use of a clock unit operated at 100 MHz, interrupt events from 10 nanoseconds to 9.

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:.