Abstract: A method for operating a power generation system having a drivetrain connected to an electrical grid during one or more grid transient events includes receiving an indication of the one or more grid transient events occurring in the electrical grid. The method also includes selecting between a first set of drivetrain damping control settings or a different, set second set of drivetrain damping control settings based on the indication. The first set of drivetrain damping control settings is for handling a single, first grid transient event, whereas the second set of drivetrain damping control settings is for handling additional, subsequent grid transient events following the first transient event. The method also includes controlling the power generation system based on the selected first or second sets of the drivetrain damping control settings such that the power generation system can remain connected to the electrical grid during the grid transient event(s).

Abstract: A method generates a classification signal classifying an electrical impedance. The time characteristic of the impedance is measured resulting in impedance values. Impedance change vectors whose direction describes the movement of the impedance in the complex impedance plane and whose length describes the amount of the respective impedance change are formed with temporally successive impedance values. A check is carried out to determine whether the impedance shows a directional, continuous impedance movement. In the event of a subsequently detected change of direction of the impedance movement, the reaching of a reversal point is inferred and the rotation of the impedance change vectors is monitored with the result of a formation of an angle of rotation measured value. A classification signal indicating a fault is generated if the impedance change vectors have rotated in the area of the reversal point through a predefined maximum angle of rotation.

Abstract: Distance protection for electric power systems disclosed herein uses an operating signal and a sequence polarizing signal made up of a supervised sequence current and a supervised sequence voltage. The polarizing signal may be determined based on the fault type and may be weighted toward sequence currents or sequence voltages depending on the power system conditions. For phase-to-ground faults, the sequence currents may include negative-sequence and zero-sequence currents. For phase-to-phase faults, the sequence currents may include negative-sequence currents. The current portion of the sequence polarizing signal may be weighted based on detection of insufficient negative-sequence current magnitude, standing unbalance, current transformer saturation, open pole, three-phase fault, and the like. The distance elements described herein provides improved protection during real-world power system conditions and changes.

Abstract: The invention relates to a method and a device for identifying arc faults in an ungrounded power supply system. This object is attained by detecting a displacement voltage to ground at an active conductor or at a neutral point of the ungrounded power supply system; by providing a value of an operating frequency occurring in the power supply system; and by analyzing a frequency spectrum of the detected displacement voltage by calculating and assessing Fourier coefficients at the locations of the operating frequency and its harmonics. Due to the broadband detection of the displacement voltage interacting with the “quick” generation of the basic functions by means of a DDS generator, arc faults can be identified reliably in an ungrounded power supply system.

Abstract: Polarizing signals for electric power system directional overcurrent and distance protection are disclosed herein. The polarizing signal may be determined using a power system tracking signal, generated using a synchronous reference frame to track to a pre-fault voltage, and maintained using a phase-locked loop. The power system tracking signal may be used for a time after a voltage signal is lost, after which a self-polarizing signal may be used. Where voltage signals are not available, a current may be used to generate the polarizing signal.

Abstract: A method detects a fault on a line of an electrical power supply system, in which current values are measured at the line ends of the line and the current values are used to check whether there is a fault on the line. In order to perform monitoring of the line such that faults can be detected comparatively quickly and sensitively, it is proposed that voltage values are also measured at the line ends. The respective measured current and voltage values are used to ascertain respective comparison current values indicating the current flowing at a comparison location on the line and the respective comparison current values are used to check for the presence of a fault on the line, and a fault signal is generated if the check has resulted in a fault present on the line being detected.

Abstract: A method and controller to automatically determine a grounding condition of a motor drive, in which an inverter is operated at a predetermined frequency while a load resistor is connected between a single phase of a motor drive inverter output and a reference node, a leakage flux linkage value is computed according to a neutral-ground voltage of the motor drive, and a processor determines whether the motor drive is solid grounded, high-resistance grounded, or floating according to the leakage flux linkage value. In certain examples, the processor automatically turns the inverter off while the load resistor is connected between the single phase of the inverter output and the reference node, and automatically determines whether the motor drive is delta corner grounded according to the neutral-ground voltage.

Abstract: A method for identifying a system anomaly in a power distribution system is described herein. The system anomaly may indicate a non-technical loss or a topology error, including schematic entry errors and component modelling errors in the power distribution system. The method includes a) selecting a common coupling point in the power distribution system, wherein downstream branches are connected to the common coupling point; b) determining voltage estimates of the common coupling point according to electrical measurements from the downstream branches; and c) identifying the system anomaly by determining whether a detection criterion is satisfied using the voltage estimates.

Abstract: Determination of information relating to a location of an electrical fault in an electrical energy distribution system based on phasor information is disclosed. A component can receive phasor information and electrical energy distribution system information. The system can determine a distance factor based on the phasor information. The distance factor can be employed to determine fault location information. A set of fault location information can be generated. Fault location information can be corrected for fault characteristics. Equivalent circuit models can be employed in determining the distance factor. Fault locations can be validated to facilitate generating subset of fault location information. Access to fault location information can be facilitated.

Abstract: Methods and apparatus are provided for fault detection and direction determination with a phase overcurrent relay using individual phase torques and the negative sequence torque, and with a ground overcurrent relay using the zero sequence torque. A directional element includes a ground element logic circuit, a negative element logic circuit and a phase element logic circuit to evaluate the operation state of the system, detect a fault condition and determine the direction of the fault condition in an electrical power distribution system having multiple sources on a power grid.

Abstract: Methods and systems for monitoring devices in a power distribution system are described. In one example, a method for use in a power distribution system including a plurality of devices is described. The method includes receiving a plurality of data signals associated with the power distribution system, determining a measurement error value associated with the power distribution system based on the plurality of data signals, comparing the determined measurement error value to a dynamic threshold, and generating an alert when the determined measurement error value exceeds the dynamic threshold.

Abstract: The present disclosure relates to a method of monitoring an electric motor serving to drive a pump, wherein, within a time interval T, current values are measured, an average value of the current values measured is determined and this average value is compared to a predetermined reference value. According to the disclosure, it is provided that the method extends to controlling the electric motor, wherein the current values measured reflect the profile of the winding current of the electric motor and, irrespective of whether they can be associated with an instantaneous maximum value of the current profile, are included in determining the average value, and wherein the average value is considered by the motor control as input parameter.

Abstract: Described examples include controllers and methods for controlling an inverter to drive a load and for detecting load faults by determining phasor values representing voltages and currents associated with the individual load phases based on sets of input values, determining voltage and current sequence components according to the phasor values, determining a sequence impedance value by recursively solving a set of update equations at least partially according to the voltage and current sequence components, and detecting a load fault when the sequence impedance value exceeds a threshold value.

Abstract: A first protective device monitors a first section of a power supply network for a symmetrical short-circuit and a second protective device monitors a second section for a symmetrical short-circuit. The second protective device is a reserve protective device, which emits a shut-off command to a power switch after a time lag when a symmetrical short-circuit in the first section is recognized. An oscillation recognition unit emits an oscillating signal which blocks the shutoff command if an oscillation in the power supply network has been recognized. External symmetrical short-circuits can be disconnected independently of an occurring oscillation, when the second protective device has recognized a symmetrical short-circuit in the first section, before the oscillation recognition unit recognizes an oscillation in the power supply network, the shut-off command is emitted independently of the presence of an oscillating signal if the lag time has elapsed.

Abstract: The invention is directed to a method for controlling a wind turbine connected to a three-phase electrical supply grid during an asymmetrical grid fault. The method is configured for wind turbines with a doubly-fed induction generator. The reactive current to be fed into the electrical supply grid in the negative phase-sequence system is generated by the line-side and the rotor-side converter in a coordinated manner and depends on the line voltage. The reactive current to be fed into the electrical supply grid is distributed among the rotor-side and line-side converters. As a result, even in the case of severely asymmetrical grid faults, the reactive current to be fed into the electrical supply grid can be provided and excessive loading of the rotor-side converter can be prevented using simple means. The invention is also directed to a wind turbine for performing the above method.

Abstract: The present invention relates to current measurement apparatus. The current measurement apparatus comprises first and second measurement devices with each of the first and second measurement devices being operative to measure current in a respective one of a live conductor and a neutral conductor substantially simultaneously. The current measurement apparatus is operative to make plural different determinations in dependence on the substantially simultaneous current measurements.

Abstract: A gateway may be configured to synchronize transmissions of a plurality of faulted circuit indicators (FCIs). The gateway may determine a time delay from a zero crossing of a power line signal and obtain network information from the at least one FCI from the plurality of FCIs. The gateway may identify a proximate FCI that is closest to a gateway based on at least one link parameter, and assign the determined time delay to the proximate FCI. The gateway may receive confirmations that at least one FCI received the determined time delay, and has synchronized transmissions based on the determined time delay and the zero crossings of the power signal.

Abstract: According to one embodiment, a protective relay performs the following steps. A/D converter 11 acquires an electric current of a power transmission line 4 via a CT 5. A computing part 12 performs various protection computations such as current differential computation using a current data measured at the end of itself and a current data measured at the opposite end. A transmitting and receiving circuit 13 transmits the current data of itself to the other protective relay 1 at the opposite end via a transmission path 3. A received level detection part 14 detects the received level of the transmission data that has been transmitted from the opposite end and received by the transmitting and receiving circuit 13.

Abstract: A generator protection device is provided. The generator protection device includes a safety factor estimation module configured to estimate a safety factor as a function of a terminal voltage (VS) of a source-end generator, and a swing center voltage (SCV) between the source-end generator and a receiving-end generator. The system further includes a comparison module configured to compare the estimated safety factor with a defined safety threshold limit, and a decision module configured to trigger an alarm or a generator circuit breaker trip action or both, based on the comparison between the estimated safety factor and the defined safety threshold limit.

Abstract: An OVP system which includes a plurality of OVP circuits coupled to respective parallel-connected switching power supplies. Each OVP circuit comprises a bus voltage overvoltage detection circuit having a first output which toggles when the voltage on the common power bus exceeds a reference voltage, a modulation flag detection circuit which receives a value that varies with a parameter associated with the PWM or PFM drive signals generated for the switching power supply to which the OVP circuit is coupled and has a second output which toggles when the parameter value exceeds a reference parameter value, logic circuitry which toggles an output when both the first and second outputs toggle, and an overvoltage response circuit which initiates a course of action such as latching or shutting down the switching power supply to which the OVP circuit is coupled when the logic circuitry's output toggles.

Abstract: A fault signal indicates a single-pole or a double-pole fault in a three-phase electrical power grid which occurred during a present electric oscillation in the electrical power grid. The method assures that single-pole or double-pole faults occurring during oscillation can be detected with high reliability in that a symmetry signal is produced during the oscillation, which indicates whether the oscillation is symmetrical or unsymmetrical, and the phases of the electrical power grid are checked for an existing fault, wherein the symmetry signal is used for carrying out the check. The fault signal is produced if a fault was detected during the check. A protective device has an accordingly equipped control unit.

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: The present invention relates to methods for providing impedance protection differentiating between in-zone and out-of-zone faults based on instantaneous, digitally derived operating and polarizing distance comparator signals. The method uses a pair of fast orthogonal filters to derive D and Q components of the input voltages and currents. Two sets of operating and polarizing signals are derived for better speed of response under varying fault moment with respect to the peaks and zero crossings of power signals. Three stages of comparison between the operating and polarizing impedance terms are used. These comparator stages use half a cycle averaging windows, and three-quarters-of-a-cycle windows. The first stage of comparison is based on energy comparator responding to both magnitude and phase information in the signals. Stages 2 and 3 are of phase comparison type, responding mostly at the phase information and neglecting the magnitude information for better immunity to noise and signal distortions.

Abstract: A method and a protection IED for supervising a secondary circuit of an instrument transformer in a power system are disclosed. The instrument transformer is connected to a power system component. The method includes: detecting, by a protection IED which is connected to the secondary circuit of the instrument transformer and protects the power system component, disturbances in a signal from the instrument transformer; and determining whether a failure occurs in the secondary circuit of the instrument transformer, according to both a disturbance detection result from the protection IED and another disturbance detection result from at least one of other protection IEDs.

Abstract: This invention relates to non-contact measurement methods and an apparatus for the identification of hazardous contact voltages on energized objects and surfaces. The apparatus includes an electric field sensor structured to sense an electric field and a gain amplifier electrically connected to the electric field sensor to amplify electric signals from the electric field sensor. The apparatus further includes a signal conditioning circuit adapted to process the amplified electric signals and form time-coordinated signals and a digital signal processor adapted to evaluate the time-coordinated signals and provide a user with a status of a contact voltage source by activating an appropriate status indicator.

Abstract: A driving device of a brushless DC motor for a fan includes a protection circuit, a storage circuit, a control circuit and a bridge circuit. The protection circuit is electrically connected with an auxiliary power. The storage circuit electrically connected with the protection circuit receives the auxiliary power. The control circuit is electrically connected with the protection circuit and the storage circuit. The bridge circuit electrically connected with the control circuit has a first switching unit, a second switching unit, a third switching unit and a fourth switching unit. The first and second switching units are coupled with one end of a motor coil. The third switching unit and the fourth switching unit are coupled with the other end of the motor coil. The first switching unit is electrically connected with the third switching unit, and the second switching unit is electrically connected with the fourth switching unit.

Abstract: A method for producing an oscillation signal which indicates oscillation in an electrical power supply system, in which measured values that characterize current and voltage at a measurement point in the electrical power supply system are detected and are converted to digital current and voltage vector measured values. Impedance values are calculated in the complex numerical domain from the current vector measured values and the voltage vector measured values. A curve profile formed by the impedance values is considered and, if appropriate, the oscillation signal is produced using characteristic properties of the curve profile.

Abstract: Provided is a high-precision and highly functional digital protective relay device and a data transmission device for a digital protective relay device, by enabling transmission of large amounts of system electrical quantity data. The data transmission device for a digital protective relay device, the transmission device comprising: an analog/digital conversion portion 6, which, after sampling a system electrical quantity signal acquired from an electric power system at m times the fundamental frequency f0 (m>12) thereof, performs conversion into n-bit digital data (n>12); a data processing portion 7, which converts m sampling data of n bits with frequency m·f0, obtained by the analog/digital conversion portion, into k sampling data with frequency k·f0 (k?m) at or below the former frequency; and a transmitting portion 8, which transmits k sampling data obtained by the data processing portion to another protective relay device in a prescribed transmission format.

Abstract: One or more attributes (e.g., pan, gain, etc.) associated with one or more objects (e.g., an instrument) of a stereo or multi-channel audio signal can be modified to provide remix capability. An audio decoding apparatus obtains an audio signal having a set of objects and side information. The apparatus obtains a set of mix parameters from a user input and an attenuation factor from the set of mix parameters. The apparatus then generates a plural-channel audio signal using at least one of the side information, the attenuation factor or the set of mix parameters.

Abstract: A system, method and computer program product for processing utility data of a power grid is provided. In one embodiment, the system includes a datamart comprised of a plurality of physical databases storing utility data, a plurality of applications comprising an automated meter application configured to process power usage data from a plurality of automated meters, a power outage application configured to identify a location of a power outage, and a power restoration application configured to identify a location of a power restoration. The system may include an analysis engine comprising a plurality of analysis objects with each analysis object configured to process data to provide a specific analysis, wherein said analysis engine is accessible via one or more of the plurality of applications, and the system may include a report module configured to receive an output from the analysis engine and to output a report.

Abstract: A system includes a power control module, a period determination module, and a control module. The power control module controls current through stator coils of a motor to rotate a rotor. The period determination module determines a first length of time between a first set of induced stator coil voltages and determines a second length of time between a second set of induced stator coil voltages. The control module determines whether an external disturbance disturbs rotation of the rotor based on a difference between the first and second lengths of time.

Abstract: A load compensation method for phase-to-ground loops in distance protection. A first reactive reach is estimated assuming zero fault resistance or with a positive sequence current. A second reactive reach is estimated with a zero sequence current. A third reactive reach is estimated with a negative sequence current. An import or export condition is estimated. A fourth reactive reach for import or export condition is estimated based on the first, second and third reactive reach. A fault impedance is estimated based on the estimated fourth reactive reach.

Abstract: Disclosed herein is a Fourier transform-based phasor estimation method and apparatus capable of eliminating the influence of exponentially decaying DC offsets. According to a Fourier transform-based phasor estimation method according to an embodiment of the present invention, an input signal is sampled, and samples of one-cycle data of the input signal are separated into at least two sample groups. A Discrete Fourier Transform (DFT) is performed on each of the sample groups. A DC offset included in the input signal is calculated on a basis of results of the DFT on each of the sample groups, and an error caused by the DC offset is calculated using the calculated DC offset. A phasor of a fundamental frequency component included in the input signal is estimated by eliminating the calculated error, caused by the DC offset, from the results of the DFT on the input signal.

Abstract: A method of identifying fault conditions in a three phase power system includes monitoring the changes of both the current and voltage properties on a three phase power network. A maximum phase change value of both the current and voltage is determined. Either the voltage or the current values are selected, whichever includes the largest maximum phase change. Thereafter, the selected set of measurements is analyzed to determine whether a fault condition exists on any phase of the three phase power.

Abstract: A method and a system for determining a circular characteristic for distance protection of a three-phase electric line, the system comprising means for detecting a fault on the electric line, means for identifying a faulted phase or phases of the electric line, means for determining, at a measuring point, a first fault loop impedance by using voltage(s) of the faulted phase(s), a second fault loop impedance by using a polarization voltage and a third fault loop impedance by using predetermined line parameters, and means for determining a radius and midpoint of the circular characteristic.

Abstract: An apparatus includes at least one Rogowski coil and a processor. The at least one Rogowski coil is positioned within an electrical power distribution network to detect a first traveling wave current caused by a fault on an electrical power transmission line of the network, generate a first signal indicative of detection of the first traveling wave, detect a second traveling wave current caused by the fault on the transmission line, and generate a second signal indicative of detection of the second traveling wave. The processor is adapted to receive the first signal and the second signal and to determine, based on the first signal and the second signal, where on the transmission line the fault occurred.

Abstract: A method and an adaptive distance protection relay for compensating for a remote line end infeed effect during determination of a distance to a resistive fault on a three-phase power transmission line. It is assumed that a fault current flows through the fault resistance. A fault loop impedance is first calculated by a known algorithm from phase voltages and phase currents. A shift of the fault loop impedance is determined from the fault loop impedance, the impedance of the transmission line for the positive current sequence and the phase angle of a complex fault current distribution factor, where the fault current distribution factor is the ratio of the fault loop current to the fault current. The distance to fault is calculated by subtracting the impedance shift from the fault loop impedance and dividing the result by the impedance of the transmission line for the positive current sequence.

Abstract: Provided is an intelligent electronic device for protection, monitoring, controlling, metering or automation of electrical power system. The system, method and device of the present invention preserves current differential protection active during a breaker bypass or similar operation. A current differential protection system is coordinated by one relay (transfer), which simultaneously establishes and handles multiple two-terminal 87L protection zones with several relays. This “enhanced multiple-terminal system” requires no change to protection settings on any local or remote relays during a bypass process.

Abstract: An apparatus and method provide protection for a synchronous generator in a power system. The method includes deriving a plurality of generator safe operating boundary data expressions from power system data and/or user-defined inputs. The power system data may include a plurality of generator data supplied by a manufacturer of the generator and/or power system parameters such as power system equivalent impedance. Each generator safe operating boundary data expression may relate to a generator capability curve, a steady-state stability limit curve, a minimum excitation limiter curve, an over excitation limiter curve, or an user-defined curve. The method also includes calculating an active power value sum and a reactive power value sum based on generator three-phase currents and voltages, comparing these sums to at least one of the plurality of generator safe operating boundary data expressions, and to provide protection and/or alarming functions for the generator based on this comparison.

Abstract: A method of identifying fault conditions in a three phase power system includes monitoring the changes of both the current and voltage properties on a three phase power network. A maximum phase change value of both the current and voltage is determined. Either the voltage or the current values are selected, whichever includes the largest maximum phase change. Thereafter, the selected set of measurements is analyzed to determine whether a fault condition exists on any phase of the three phase power.

Abstract: A protection circuit limits operating power supplied to an electrical device from an electrical power source below a predetermined power rating. The protection circuit comprises a switching device for adjusting electrical power supplied from the power source to the electrical device; a sensor sensing a parameter relating to the operating power; and a comparator comparing the parameter sensed by the sensor and, in response to identifying an undesirable operating condition, controlling the switching device to adjust electrical power supplied to the electrical device to below a predetermined power rating.

Abstract: A method of operating a relay device, in an electrical circuit comprising first and second main circuit breakers, and a bus tie circuit breaker connecting the first and second main circuit breakers, the method comprising computing a first positive sequence current phasor for the first main circuit breaker and a second positive sequence current phasor for the second main circuit breaker computing a first positive sequence voltage phasor for the first main circuit breaker and a second positive sequence voltage phasor for the second main circuit breaker; computing a correction of the first positive sequence voltage and second positive sequence voltage to a line-to-neutral phase angle reference if there is any rotation in a potential transformer connection; determining a fault has occurred when a magnitude of a current through at least one of the first main circuit breaker or the second main circuit breaker exceeds a predetermined threshold; determining a phase angle difference by comparing the phase angle of the

Abstract: A method of operating a relay device, the method comprising the steps of: providing main circuit-breakers and a bus-tie-breaker connecting the main-circuit-breakers; defining a partial-differential-zone comprising a main circuit breaker and the bus-tie breaker; assigning a first value to the direction of the fault current flowing into the partial differential zone;—assigning a second value to the direction of the fault currents flowing out of the partial-differential-zone, wherein the first value is not equal to the second value;—comparing the values assigned to the fault currents; determining if the fault currents are flowing into the partial differential zone; and determining if at least two of the fault-currents is flowing in a different direction with respect to the partial-differential-zone wherein one of the fault currents is flowing into the partial-differential-zone and one of the fault currents is flowing out of the partial differential zone.

Abstract: An apparatus includes at least one Rogowski coil and a processor. The at least one Rogowski coil is positioned within an electrical power distribution network to detect a first traveling wave current caused by a fault on an electrical power transmission line of the network, generate a first signal indicative of detection of the first traveling wave, detect a second traveling wave current caused by the fault on the transmission line, and generate a second signal indicative of detection of the second traveling wave. The processor is adapted to receive the first signal and the second signal and to determine, based on the first signal and the second signal, where on the transmission line the fault occurred.

Abstract: A system and method for locating faults on multi-terminal power system transmission lines uses synchronized phasor measurements to accurately determine fault location and fault impedance regardless of fault type, fault resistance, and coupling to other adjacent power system transmission lines.

Abstract: A system and method for accomplishing power swing blocking and unstable power swing tripping schemes during disturbances of electrical networks is disclosed. The disclosed system and method eliminates the requirement of stability studies. The no-setting scheme utilizes the swing center voltage of the electrical network to carry out its functions.

Abstract: A method of operating a relay device, the method comprising the steps of: computing positive-sequence first and second current-phasor for the first and second main circuit-breakers and computing currents from phasors, and the bus-tie-breaker; computing positive-sequence voltage for the bus-tie-breaker; triggering a method when at least one fault current at the bus-tie-breaker exceeds a threshold, without the presence of a fault on one of the feeders; determining whether the fault is internal or external, wherein the fault is internal if the positive-sequence current of the first and second main circuit breakers is in phase; and wherein if the positive-sequence current through the first main circuit breaker is not in-phase with the positive-sequence current through the second main circuit breaker, the fault is external to the bus; determining whether the fault is on a first or second side of the tie circuit; and locating the fault.

Abstract: The system is used in a distance-type protective relay which includes a calculation circuit responsive to voltage and current values from a power line to produce a quantity which is analogous to the distance between the relay and a fault on the line, referred to as an m quantity. This quantity is then applied to a distance element/circuit for comparison of said quantity with a setting reach value for a zone one distance protection to determine whether the fault is within zone one protection. The system includes a filter circuit which filters the quantity before it reaches the distance element, resulting in a smoothing of said quantity and rejection of noise therefrom. The system further includes a control circuit which determines whether the filter is to be used in the system in a particular situation, depending upon whether when the value of the quantity is above a selected percentage of the setting reach value.

Abstract: Provided is an apparatus and method for identifying a specific lost current transformer (CT) signal of number of CT signals provided by a corresponding number of CTs coupling a protective device to at least one protection zone. The method includes selectively providing pairs of first and second binary control signals corresponding to each of the CT signals in response to comparisons of RMS current changes of respective CT signals. A third binary control signal associated with a protection zone is provided in response to receipt of the pairs of first and second binary control signals. A first value for only one of the first binary control signals, a second value for all of the second binary control signals and the first value for the third binary control signal for a predetermined time indicates the loss of the CT signal corresponding to the first binary control signal having the first value.

Abstract: The present invention is directed to a method and apparatus for improving operational reliability during a loss of a phase voltage (LOV) in a multi-phase power system, wherein a voltage representative of the LOV phase is calculated. The representative voltage is used for computing a reference polarizing voltage suitable for a protection unit.