Abstract: This invention relates to a time alert device (1) for use with an earth leakage protection device comprising a microprocessor system (10) provided with a software controlled alert trigger timer (22). On time out of the alert trigger timer, the microprocessor system (10) initiates an audible and/or visual annunciation to remind the user of the earth leakage protection device to perform integrity test on the earth leakage protection device. If the earth leakage protection device fails the integrity test, the user detects that the earth leakage protection device could be faulty and needs expert attention. If the earth leakage device passes the integrity test, the alert trigger timer is reset for another predetermined time interval to remind the user to perform another integrity test on the earth leakage protection device. The time alert device can be further provided with a message display panel.

Abstract: An intelligent electronic device may provide restricted earth fault protection to components of an electrical power delivery system using both an amplitude comparator and a phase angle comparator configured to independently detect faults. The IED may include selection logic configured to select the output of one of the phase angle comparator and the amplitude comparator, to the exclusion of the other, based on system conditions. Accordingly, when system conditions are such that a phase angle comparator is better suited to detect a fault, selection logic may select the output of the phase angle comparator. Similarly, when system conditions are such that an amplitude comparator may better detect a fault, selection logic may select the output of the amplitude comparator. A protection system may further include an in-zone fault detector configured to detect in-zone faults.

Abstract: A circuit breaker apparatus may be used to interrupt overcurrent and ground fault in a circuit. The circuit breaker apparatus may include an overcurrent coil for tripping the circuit breaker apparatus, a voltage coil also for tripping the circuit breaker apparatus located proximate to the overcurrent coil, ground fault electronics connected to the voltage coil and structured to detect a ground fault in the circuit when the ground fault exceeds a threshold level, and a solid state switch. The ground fault electronics can be structured to send a trip signal to close the solid state switch when a ground fault is detected, the solid state switch is configured to force a current through the voltage coil when the solid state switch is closed, the current being of sufficient magnitude to trip the circuit breaker apparatus.

Abstract: There is disclosed a circuit interrupting device with symmetrical inputs comprising a first input configured for connection to a power source or a load circuit and a second input configured for connection to a power source. There are a plurality of electrical conductors extending from the first and second inputs and a third input configured for connection to a load provided by a user. There is also a first set of transformers comprising at least one differential transformer and at least one neutral transformer connected to detect leakage current in a load circuit coupled to the first set of terminals. There is also a second set of transformers comprising at least one additional differential transformer and at least one additional neutral transformer connected to detect leakage current in a load circuit coupled to the second set of terminals.

Abstract: An apparatus is provided for fault protection. The apparatus may include one or more electronic components configured to receive a single phase-to-ground fault signal and a double phase-to-ground fault signal subsequent to receiving the single phase-to-ground fault signal. The one or more of electronic components may be further configured to provide for a delay while the single phase-to-ground fault signal indicates that a single phase-to-ground fault is present on the ungrounded power system and the double phase-to-ground fault signal indicates that the double phase-to-ground fault is present on the ungrounded power system. The delay may allow for an opportunity to isolate a phase-to-ground fault on a first phase from a phase-to-ground fault on a second phase. Associated methods and computer program products are also provided.

Abstract: A circuit is disclosed for disconnecting a power source upon the detection of a leakage current comprising a power cable having an insulated first and a second wire. The power cable has a conductive shield surrounding the first and second wires with a drain wire electrically contacting the conductive shield. A disconnect switch is interposed between the power source and the power cable. A primary circuit controls the disconnect switch. A secondary circuit is connected to the drain wire for sensing a leakage current between the conductive shield and one of the first and second wires. An optical switch interconnects the primary circuit and the secondary circuit for opening the disconnect switch upon the secondary circuit sensing a leakage current.

Abstract: A ground fault interrupter to be used by utility company while effecting repairs to the electrical service for a building is positioned to interrupt the power supply to the building in case of a detected ground fault and utilizes a sensor for detecting the fault current at the service entrance to a building; a contact switch, selectively movable between open and closed positions, mounted for temporary use in series with said power supply to the building; and a microprocessor based circuit for measuring and evaluating fault current detected by the sensor and controlling the selective movement of the contact switch between its open and closed positions.

Abstract: A switching circuit, e.g. an RCD, comprises a pair of mechanical contacts (M) in an alternating current electricity supply (N, L) and circuit means (SCR) for opening the contacts to cut off the supply in response to a switching signal (S). The switching circuit includes further circuit means (Rs, Cs, D2, D3, Q1, Q2) for defining successive periods of time (“activation windows”) during which the magnitude of the supply voltage is not at a maximum and allowing the contacts to open in response to a switching signal only during such windows.

Abstract: Various methods and apparatus are described for a photovoltaic system. In an embodiment, a hybrid grounding circuit as well as a ground fault monitoring circuit are in the inverter circuitry with its switching devices that generate three-phase Alternating Current (AC) voltage. The three-phase AC voltage is supplied to a utility power grid interface transformer, where a primary-side common node of the Utility Power grid interface transformer is connected to Earth ground. Each inverter has 1) its own set of isolation contacts to connect as well as isolate this particular inverter from the utility grid interface transformer, and 2) control components in the ground fault monitoring circuit for controlling operation of the isolation contacts based off a presence of the ground fault detected by the ground fault monitor circuit for that inverter. The inverter circuit receives a DC voltage supplied from its own set of ungrounded Concentrated PhotoVoltaic modules.

Abstract: A short-circuit distance relay is provided which has a high accuracy and an excellent reliability such that the relay can determine the fault phase based on impedance values measured by each phase, prevent misjudgment and unnecessary operation due to overreach without depending on the power system conditions, and operate even if multiple faults occur. An impedance calculation part (11) calculates an impedance value of the phase in which the direction element (SM) has operated. A minimum phase selection part (12) selects as a fault phase, the phase having a minimum impedance value. When the impedance value of the selected phase is equal to or less than the setting impedance value of the distance element of the phase, an output of the distance element of the phase is made to be valid to output an opening command to a circuit breaker. As a result, it is possible to prevent misjudgment and unnecessary operation due to overreach without depending on the power system conditions.

Abstract: A system and method for detecting a fault condition by a relay is provided. The system includes means for detecting phase currents through three electrical phases, means for detecting a ground fault current, a processor configured to perform a current-based function based upon at least one of the phase currents and a filter. The processor is configured to perform current-based functions based on whether the filter is enabled or disabled.

Abstract: An exemplary ground fault detection device is capable of detecting a ground fault on multiple phases. The ground fault detection device includes a monitoring module that monitors the phases and determines if there is a non-zero electrical energy value sum for a selected interval on each phase. An output module provides a ground fault indication when all of the phases have a non-zero electrical energy sum for the selected interval.

Abstract: A differential protection device comprising: differential current measuring means, processing means connected to the measuring means and comprising operating rating selection means and time delay selection means to select tripping curves, actuating means, and test means connected to the measuring means. In the protection device the test means are associated with the operating rating selection means and with the time delay selection means to select a minimum or reduced operating rating and to select a minimum or reduced time delay when said test means are actuated.

Abstract: A multi-pole circuit breaker for a power distribution system having multiple line conductors carrying AC currents that are out of phase with each other, and a common neutral conductor, comprises first and second current sensors, a ground fault detection circuit, and an arcing fault detection circuit. The first current sensor is adapted to be coupled to both of the line conductors and to the neutral conductor and produces a first output signal indicative of the resultant of the electrical currents flowing in the line and neutral conductors. The ground fault detection circuit receives the first output signal and produces a trip signal in response to the detection of a ground fault.

Abstract: A generator winding-to-ground fault detection system is disclosed that includes a signal injection source in electrical communication with a winding of an electric power generator via an injection transformer. The winding may be coupled to ground via a winding-to-ground path and the signal generation source may generate an injection signal capable of being injected to the winding using the injection transformer. The disclosed system may further include a protection module in communication with the signal injection source and the electric power generator configured to receive the injection signal and a signal relating to the current through the winding-to-ground path, and to determine the occurrence of a winding-to-ground fault condition based at least in part on the injection signal and the signal relating to the current through the winding-to-ground path.

Abstract: A ground-fault circuit-interrupter (GFCI) system is provided that provides reliable and timely tripping of faulted circuits while minimizing so-called “nuisance” tripping. The GFCI includes a voltage unbalance detection device coupled to the main bus circuit for detecting a voltage unbalance during a fault condition. A computer processor in communication with the voltage unbalance detection device is programmed to determine when an actual fault condition exists based on a state of the voltage unbalance and certain predetermined among the fault signal generated by a GFCI unit in the main bus circuit and the fault signals generated by GFCI units in individual feeder circuits.

Abstract: A method and apparatus for identifying a ground fault in a motor drive system that includes at least one three phase power conditioner that is linked to three phase supply lines and to positive and negative DC buses, the method comprising the steps of controlling the power conditioner at an operating frequency to convert power, while controlling the power conditioner to convert power, controlling the power conditioner to apply a common mode signal on each of the three phase supply lines where the common mode signal has a frequency that is different than the operating frequency, sensing the common mode signal on at least one of the three phase supply lines and when the common mode signal on the at least one of the three phase supply lines is greater than a threshold level, indicating that a ground fault has occurred.

Abstract: A system and method for detecting a fault condition by a relay is provided. The system includes means for detecting phase currents through three electrical phases, means for detecting a ground fault current, a processor configured to perform a current-based function based upon at least one of the phase currents and a filter. The processor is configured to perform current-based functions based on whether the filter is enabled or disabled.

Abstract: A circuit breaker apparatus may be used to interrupt overcurrent and ground fault in a circuit. The circuit breaker apparatus may include an overcurrent coil for tripping the circuit breaker apparatus, a voltage coil also for tripping the circuit breaker apparatus located proximate to the overcurrent coil, and ground fault electronics connected to the voltage coil and structured to detect a ground fault in the circuit when the ground fault exceeds a threshold level. The ground fault electronics can be structured to send a trip signal to the voltage coil when a ground fault is detected, and the voltage coil can be structured to trip the circuit breaker apparatus when it receives the trip signal from the ground fault electronics.

Abstract: A circuit breaker includes for each neutral and phase power conductor, a current sensor sensing an alternating current flowing in a corresponding power conductor, a comparator determining whether the sensed alternating current is positive or negative, a rectifier rectifying the sensed alternating current to provide a rectified current value, and an analog-to-digital converter converting the rectified current value to a signed digital value having a positive sign. A processor cooperates with the comparators and the analog-to-digital converters and includes a routine that changes the positive sign of the signed digital value to a negative sign if the sensed alternating current is negative, adds the signed digital value for each power conductor to provide a sum, and employs the sum to determine whether to output a ground fault signal. The processor further cooperates with an operating mechanism to trip open separable contacts responsive to the ground fault signal.

Abstract: An inverter-driven rotating machine system is provided in which three-phase AC electric power of the inverter is supplied to a rear motor generator by using a cable. One end of an additional cable is connected to rotating machine terminals, namely motor input terminals of a motor case. The other end is connected to fixed voltage terminals, namely inverter additional terminals on an outer case of the inverter via resistors.

Abstract: A circuit is disclosed for disconnecting a power source upon the detection of a leakage. The circuit comprises a disconnect switch for disconnecting the power source. A primary circuit controls the disconnect switch. A secondary circuit senses a leakage current. An optical switch interconnects the primary circuit and the secondary circuit for opening the disconnect switch upon the secondary circuit sensing a leakage current. The circuit is suitable for use as a leakage current detection and interruption circuit for completely electrically disconnecting and isolating the power source and the primary circuit from the secondary circuit.

Abstract: A multi-pole circuit breaker for a power distribution system having multiple line conductors carrying AC currents that are out of phase with each other, and a common neutral conductor, comprises first and second current sensors, a ground fault detection circuit, and an arcing fault detection circuit. The first current sensor is adapted to be coupled to both of the line conductors and to the neutral conductor and produces a first output signal indicative of the resultant of the electrical currents flowing in the line and neutral conductors. The ground fault detection circuit receives the first output signal and produces a trip signal in response to the detection of a ground fault.

Abstract: A motor drive ground fault detection device operates by computing the total RMS voltage of all the phases, and comparing the total RMS voltage to a threshold to determine if a ground fault has occurred.

Abstract: An apparatus is provided for fault protection. The apparatus may include one or more electronic components configured to receive a single phase-to-ground fault signal and a double phase-to-ground fault signal subsequent to receiving the single phase-to-ground fault signal. The one or more of electronic components may be further configured to provide for a delay while the single phase-to-ground fault signal indicates that a single phase-to-ground fault is present on the ungrounded power system and the double phase-to-ground fault signal indicates that the double phase-to-ground fault is present on the ungrounded power system. The delay may allow for an opportunity to isolate a phase-to-ground fault on a first phase from a phase-to-ground fault on a second phase. Associated methods and computer program products are also provided.

Abstract: The invention refers to a method and an apparatus (1) for protecting people against leakage currents while using appliances such as home appliances or the like. The apparatus (1) is provided with a differential switch (20) normally open and a differential current transformer (39) which generates a signal proportional to the leakage current, an elaboration unit (50) interfaced with the latter acquires said signal and keeps the switch (20) closed until a dangerous condition is met, corresponding to an acquired signal having a magnitude greater than a limit value.

Abstract: An arc fault circuit interrupter includes separable contacts, an operating mechanism, a current sensor sensing current flowing through the contacts and outputting a sensed current, and a processor determining and storing peak values of the sensed current for plural half-cycles. The processor provides arc fault detection, determines whether a first predetermined plurality of half-cycles occur in succession and correspond to non-unity power factor, and responsively inhibits the detection for a first predetermined time, and whether a second predetermined plurality of half-cycles occur in succession, each with smaller peak amplitude than that of an immediately preceding half-cycle of like or differing polarity, and responsively inhibits the detection for a second predetermined time.

Abstract: A circuit interrupter includes band pass filters cooperating with a current sensor to output bands having different, non-overlapping ranges of frequencies, peak detectors cooperating with the filters to detect corresponding peak current values, envelope detectors cooperating with the filters to detect corresponding occurrences from the bands being within corresponding predetermined magnitude ranges, a counter counting the occurrences, and a processor providing and disabling series arc detection when sensed current is greater than a first predetermined value. The processor determines tallies responsive to peak current values exceeding corresponding thresholds, determines series arcing from sensed current being less than the first predetermined value for a predetermined time, the tally for a current half-cycle being nonzero, and a count for the current half-cycle being different than the count for an immediately previous half-cycle of like polarity by at least a second predetermined value.

Abstract: A method and apparatus for identifying a ground fault in a motor drive system that includes at least one three phase power conditioner that is linked to three phase supply lines and to positive and negative DC buses, the method comprising the steps of controlling the power conditioner at an operating frequency to convert power, while controlling the power conditioner to convert power, controlling the power conditioner to apply a common mode signal on each of the three phase supply lines where the common mode signal has a frequency that is different than the operating frequency, sensing the common mode signal on at least one of the three phase supply lines and when the common mode signal on the at least one of the three phase supply lines is greater than a threshold level, indicating that a ground fault has occurred.

Abstract: A circuit is disclosed for disconnecting a power source upon the detection of a leakage current comprising a power cable having an insulated first and a second wire. The power cable has a conductive shield surrounding the first and second wires with a drain wire electrically contacting the conductive shield. A disconnect switch is interposed between the power source and the power cable. A primary circuit controls the disconnect switch. A secondary circuit is connected to the drain wire for sensing a leakage current between the conductive shield and one of the first and second wires. An optical switch interconnects the primary circuit and the secondary circuit for opening the disconnect switch upon the secondary circuit sensing a leakage current.

Abstract: A trip actuator assembly is provided for a circuit breaker including a housing having a mounting surface, separable contacts enclosed by the housing, and an operating mechanism structured to open and close the separable contacts. The trip actuator assembly includes a trip actuator cooperable with the operating mechanism, and a planar member having first and second ends, first and second edges, and an aperture. The trip actuator is at least partially disposed within the aperture and is further disposed between the planar member and the mounting surface of the housing. The first edge of the planar member is removably coupled to the mounting surface, thereby removably coupling the trip actuator to the housing. The circuit breaker may include an accessory tray which is insertable on and is removable from the mounting surface. When inserted, the accessory tray abuts the body of the trip actuator enclosure further securing the trip actuator.

Abstract: An arc fault circuit interrupter includes separable contacts, a neutral conductor, an operating mechanism structured to open and close the separable contacts, at least one current sensor structured to sense current flowing through the separable contacts and output a sensed current value; and a processor. The processor includes a first routine structured to provide parallel arc fault detection, a second routine structured to provide series arc fault detection, and a third routine structured to enable the first routine and disable the second routine for a predetermined time when the sensed current value is greater than a predetermined value and to enable the second routine and disable the first routine for the predetermined time when the sensed current value is less than the predetermined value.

Abstract: A ground fault circuit interrupter device is described.

Abstract: A signal analyzer for calculating the power consumption and power factor of a three-phase power system driving a motor includes logic that determines whether the analyzer's own input terminals are wired in a proper or inverted manner. To do this, the signal analyzer observes a pattern of zero crossing slope values of the three line-to-line voltages of the three-phase power system and observes a pattern of zero crossing slope values of the current in the three power lines. The analyzer also compares the slope of a voltage signal as the signal passes through zero volts and the sign of a corresponding current signal that exists as the voltage signal crosses zero volts. Based on the observed voltage and current patterns and the voltage-to-current relationships, the analyzer can positively identify which of a plurality of inputs or signal wires are inverted.

Abstract: In one aspect, a polyphase power converter includes an input adapted to couple to a polyphase AC source, a positive DC output, and a negative DC output. The polyphase power converter also includes a first plurality of circuits and a second plurality of circuits. In one embodiment, each of the first plurality of circuits is adapted to receive a plurality of phases of the polyphase AC source and to produce a DC voltage at the positive DC output. Each of the second plurality of circuits is adapted to receive a plurality of phases of the AC source and to produce a DC voltage at the negative DC output. In one embodiment, the polyphase power converter includes a plurality of switching devices and each of the plurality of switching devices is adapted to isolate at least one phase of the polyphase AC source from at least one of the plurality of circuits.

Abstract: The present disclosure relates to resettable circuit interrupting devices and apparatus capable of being tested and reset from remote locations, and in particular to portable circuit interrupting devices and apparatus capable of being tested and reset from remote locations.

Abstract: Low cost apparatus and methods of detecting arc faults for better discriminating electrical events. The arc fault detection apparatus includes a current sensor, a di/dt input sense circuit, a dv/dt input sense circuit, and a processing unit. The current sensor monitors a power line current, and provides high frequency components of the power line current to the di/dt input sense circuit. The dv/dt input sense circuit monitors a power line voltage. The di/dt and dv/dt input sense circuits generate signals carrying information relating to changes in the power line current and the power line voltage, respectively. The processing unit analyzes these changes in the power line current and the power line voltage to discriminate detected electrical arcing events from nuisance loads with increased accuracy.

Abstract: Apparatus for protecting a two-line electric power distribution system includes a circuit breaker pole in each line. Each pole includes a fault detector generating a fault signal in response to either an arc fault or a ground fault in the protected line, and a trip unit responsive to the fault signal. Each trip unit includes a trip coil and an SCR connected in series at a node with the trip coil connected to the neutral conductor and the SCR connected to the associated line conductor. A jumper connects the two nodes together directly without electrical isolation so that a fault signal from either detector energizes both trip coils to open both poles in response to an arc fault or a ground fault in either line, even if one of the line conductors is not energized.

Abstract: The invention relates to a method for detection of a ground fault (18), which occurs in the vicinity of a neutral point (22), in a polyphase electrical device which is operated at a fundamental frequency, in particular an electrical machine (10) or a transformer which has a number of windings (11, 12, 13), which are associated with the individual phases, one end of each of which windings (11, 12, 13) is connected to the neutral point (22) and the other end of each of which windings (11, 12, 13) is connected directly to a power supply network via a power supply system connection (14, 15, 16). Simple and reliable detection is achieved in that the change in the physical variables which is associated with a ground fault (18) is measured in the immediate vicinity of the ground fault (18), and is evaluated.

Abstract: To protect people and equipment, three-phase AC drives need to be properly grounded, and ground faults need to be quickly detected. Conventional methods of detecting ground faults are affected by external factors that reduce their sensitivity. As an improvement on conventional methods, ground fault detection is accomplished by deriving a neutral point from the three-phase output of an AC drive, decoupling normal operating currents of the AC drive from the neutral point, resistively grounding the neutral point, and sensing when a magnitude of signals between the neutral point and ground exceed a maximum threshold level, ground faults are quickly detected. By effectively filtering normal operating currents from ground fault current, detection sensitivity is improved.

Abstract: Disclosed is a power supply for measuring the line impedance of an underground cable, which includes an input terminal section having a plurality of input terminals, a plurality of autotransformers, a transformer adjustment tap, a plurality of 3rd-harmonics cancellation transformers, and an output terminal section having a plurality of output terminals. The autotransformers are connected respectively to the input terminals. The transformer adjustment tap is connected to all of the autotransformers. The 3rd-harmonics cancellation transformers are connected respectively to the autotransformers. The output terminals are connected respectively to the 3rd-harmonics cancellation transformers.

Abstract: Three single-phase transformers are provided, the primary sides connected in a Wye configuration. One terminal on the primary side of each transformer is coupled to a reference node and the other terminal on the primary side of each transformer is coupled to one phase of the power supply bus. The secondary sides of the transformers are connected in a delta configuration through a resistor. The circuit connecting the secondary sides of the transformers is not electrically connected to ground.

Abstract: A three-phase motor protector uses two toroids to monitor all three phases of a three-phase motor. Current and phase loss are monitored directly in phases A and B while the phase C current level is determined by analysis of the phase A and B relationship. Current is induced into the phase A and B toroids from the motor supply lines with the resulting wave fed to an input of high-gain inverting amplifiers to provide A and B square waves which are inputted to separate channels of a microprocessor (U3). The square waves are processed by an AND gate providing an output square wave with a 16.66 percent duty cycle for normal operation. Upon loss of phase C the ANDed result is a digital low since the individual waves of phases A and B become an inverse of one another. In order to prevent nuisance tripping an AND output of less than 2 percent duty cycle is treated as a phase loss.

Abstract: The directional element, following enablement under selected input current conditions, calculates a zero sequence impedance, in response to values of zero sequence voltage and zero sequence current. The current value is selected between two possible values, one being the value from an associated current transformer, the other being the sum of the currents IA+IB+IC. The calculated zero sequence impedance is then compared against sensitive selected threshold values, established particularly for ungrounded systems. A forward fault indication is provided when the calculated zero sequence impedance is above a first established sensitive threshold value, and a reverse fault indication is provided when the calculated zero sequence impedance is below a second established sensitive threshold value.

Abstract: A distributed monitoring and protection system for a distributed power network. The system includes a plurality of high-speed measuring units (MUs), wherein each MU is coupled to a power line to measure values of electrical parameters of the power line. Electrical parameters, such as current, voltage, power and frequency are measured by the MUs. The MUs communicate with a control unit (CU) over a high-speed communications network. The CU includes a processor executing algorithms for evaluating the measured parameters to determine the status of the power network and the MUs. The processor also executes fault detection and isolation by comparing the measured values against predetermined threshold values. When a fault is detected by the CU, protective action, such as tripping of a circuit breaker, may be initiated by the CU directly or by transmitting the tripping command over the high speed data network to a local MU. The local MU may then trip the circuit breaker.

Abstract: Two detection systems are provided for a protective device, in particular an FI protective device, having a core balance transformer whose secondary winding is followed by a tripping relay for operating a switching mechanism, which switches a conductor network. In this case, a first detection system carries out the tripping function for fault currents at a fault current frequency below a changeover frequency. The second detection system carries out the tripping function for fault currents above the changeover frequency. The changeover frequency is in this case preferably not less than 1 kHz.

Abstract: To protect people and equipment, three-phase AC drives need to be properly grounded, and ground faults need to be quickly detected. Conventional methods of detecting ground faults are affected by external factors that reduce their sensitivity. As an improvement on conventional methods, ground fault detection is accomplished by deriving a neutral point from the three-phase output of an AC drive, decoupling normal operating currents of the AC drive from the neutral point, resistively grounding the neutral point, and sensing when a magnitude of signals between the neutral point and ground exceed a maximum threshold level, ground faults are quickly detected. By effectively filtering normal operating currents from ground fault current, detection sensitivity is improved.

Abstract: The fault circuit interrupter with fail safe mode and method can include a detection circuit for determining whether an error has occurred in an exterior circuit, and an interrupter device for stopping current flow to the exterior circuit when an error has been detected. The fault circuit interrupter can also include a fail safe mode, wherein if any of the fault circuit interrupter's key electrical and/or mechanical components malfunction or are not working, the fault circuit interrupter is incapable of being reset after a trip.

Abstract: An apparatus and method for detecting a short in a load which receives power from a transformer having a primary winding and a secondary winding with the load being connected to the secondary winding. The apparatus has a waveform conversion circuit, a phase detector circuit and a filter. The waveform conversion circuit converts voltage and current signals that represent the voltage and current, respectively, of the primary winding into generally squarewave voltage and current signals, respectively. The phase detector circuit outputs a control signal having a first state when the generally squarewave voltage and current signals are substantially in phase and a second state when there is a difference in phase between the generally squarewave voltage and current signals that is greater than a predetermined phase difference. The filter filters the control signal outputted to the phase detector circuit.

Abstract: A method and device for providing series compensation for rotating electric alternating current machines connected either directly, or via a static current converter, to a three-phase distribution or transmission network. The stator of the electric machine is Y-connected. A capacitive circuit for the fundamental frequency of the voltage is connected to each phase between the low voltage side of the winding and a ground of the transmission network.