Schweitzer Engineering Laboratories, Inc.

Ritwik Chowdhury

Dale S Finney

Normann Fischer

Matchyaraju Alla

Gabriel Benmouyal

Satish Samineni

Rogerio Scharlach

Carolyn Sun

Douglas I Taylor

Vinod K Yedidi

Brett Mitchell Cockerham

Wasif Ahmad

John C Town

Jon Steinmetz

Jakov Vico

Jason Andrew Young

Dale Finney

Breaker control units (BCUs) may include an output to selectively cause a circuit breaker (CB) to open and close a circuit, a voltage input to monitor a voltage of at least one of a bus and a line, a processor to calculate a point-on-wave switching time, and a remote input configured to be coupled to a remote intelligent electronic device (IED) to receive commands to selectively open and close the CB at a specified optimal time. Electric power systems may include such BCUs. Methods of switching CBs may include monitoring at least one of a bus and a line with a BCU and controlling switching of the CB at a predetermined point-on-wave value with onboard electronics of the BCU. The methods may additionally include calculating a trapped charge and/or a residual flux with an IED and causing the BCU to switch the CB at a specific optimum point-on-wave value.

Breaker control units and related systems and methods

The present disclosure pertains to devices, systems, and methods for monitoring a generator. In one embodiment, the system may include a measurement subsystem to receive a plurality of split-phase measurements of branch currents associated with the at least one generator. A split-phase transverse differential monitoring subsystem may receive the plurality of split-phase measurements of branch currents associated with the at least one generator and may generate an offset value representing a standing split-phase current. A protective action subsystem may generate a first protective action based on the phasor operating current.

Split-phase protection of generators

The present application discloses systems and methods related to protection of a reactor in an alternating current (AC) electric power system. In one embodiment, a system may include a protective action subsystem to implement a protective action based on identification of a fault condition associated with a reactor. A frequency determination subsystem may determine when a frequency of the AC voltage is outside of a range defined by a lower threshold and an upper threshold and may identify a change in the frequency associated with de-energization of a line in electrical communication with the reactor. A supervisory subsystem may restrain implementation of the protective action when the frequency is outside of the range or when the change in the frequency is associated with de-energization of the line in electrical communication with the reactor.

Line reactor protection security using local frequency measurement

An intelligent electronic device (IED) may obtain a voltage measurement matrix based on an arrangement of a transformer in a power system. The IED may obtain a delta connection compensating angle based on the location of the circuit breaker and the transformer arrangement. The IED may obtain voltage measurements of the transformer. The IED may determine a residual flux value of the transformer based at least in part on the voltage measurements, the voltage measurement matrix and the delta connection compensating angle. The IED may send a signal to a circuit breaker of the transformer to connect the transformer to the power system based at least in part on the system voltage and residual flux value.

Method of controlled switching for transformers using transformer residual flux

Disclosed are systems and methods to determine a direction to a ground fault of an electrical generator or motor using a known steady-state standing error referenced to a positive-sequence voltage measurement to determine a system standing error and utilizing the system standing error to determine an operating current with anomalies attributable to a fault. A ground fault may be determined using zero-sequence voltage signals from the generator or motor installation. The operating current, along with the zero-sequence voltage, may be used to determine a direction to the fault. The generator or motor may be high-impedance grounded. The systems and methods further indicate the direction to a fault where multiple generators or motors are connected to a common bus.

Selective stator ground fault protection using positive-sequence voltage reference

Systems and methods are described herein to detect an open-phase condition associated with an inverter-based resource for electric power generation within an electric power delivery system. An electric power delivery system may include one or more inverter-based resources that provide three phased electric power to one or more loads of an electric utility. A controller may include circuitry to measure voltage unbalances between different phases, high voltage sequences, phase voltage waveform harmonic distortions, voltage levels, and current levels to dependably detect an open-phase condition of the electric power delivery system.

Dependable open-phase detection in electric power delivery systems with inverter-based resources

The present disclosure relates to systems and methods for protecting against and mitigating the effects of over-excitation of elements in electric power systems. In one embodiment, a system consistent with the present disclosure may comprise a point pair subsystem to receive a plurality of point pairs that define an over-excitation curve for a piece of monitored equipment. The system may receive a plurality of measurements corresponding to electrical conditions associated with the piece of monitored equipment. A logarithmic interpolation subsystem may determine a logarithmic interpolation corresponding to one of the plurality of measurements based on the plurality of point pairs. An over-excitation detection subsystem may detect an over-excitation condition based on the logarithmic interpolation, and a protective action subsystem may implement a protective action based on the over-excitation condition.

Accurate modeling of equipment overexcitation damage curves

Systems and methods to estimate trapped charge for a controlled automatic reclose of a power line using a ganged switching device are described herein. For example, an intelligent electronic device (IED) may calculate a voltage amount associated with trapped charge of each phase of a power line based on voltage measurements of the power line. The IED may send a signal to close a ganged switching device at a time based at least in part on the trapped charge of each phase of a power line.

Controlled three-pole close for transmission lines

Systems and methods to estimate trapped charge for a controlled automatic reclose are described herein. For example, an intelligent electronic device (IED) may calculate an analog amount of trapped charge of each phase of a power line based on voltage measurements of the power line. The IED may close a switching device of each phase at a time corresponding to a point-on-wave associated with the analog amount of trapped charge of the respective phase.

Trapped charge estimation

Detection of, and protection against faults within a restricted earth fault (REF) zone of a transformer or a generator is disclosed herein. Security of the REF protection element uses comparison of a negative-sequence reference quantity. The REF condition is only detected when there is sufficient ground involvement and a fault in the reverse detection has not been detected. Dependability of the REF protection element in low-impedance grounded systems is improved by ensuring that the element operates when a zero-sequence reference quantity and a neutral operate quantity are orthogonal to each other. The REF protection element further determines an open CT condition and blocks detection of an REF fault upon determination of the open CT condition. A tripping subsystem may issue a trip command based upon detection of the REF condition.

Secure and dependable restricted earth fault protection for electric power generators and transformers

Detection and protection against electric power generator rotor turn-to-turn faults, rotor multi-point-to-ground faults, and rotor permanent magnet faults is provided herein. A fractional harmonic signal is used to determine the rotor fault condition. The fractional harmonic signal may be a fractional harmonic magnitude of the circulating current of one phase. The fractional harmonic may be a fractional harmonic magnitude of a neutral voltage. A tripping subsystem may issue a trip command based upon detection of a rotor turn-to-turn fault condition.

Generator rotor turn-to-turn fault detection using fractional harmonics

An intelligent electronic device (IED) may obtain a residual flux of each phase of a transformer. The IED may determine a maximum difference (DIF) signal based on the residual flux and the prospective flux associated with potential close POWs of the corresponding phase. The TED may select a closing POW that results in a minimum DIF signal. The TED may send a signal to close a ganged switching device of the transformer at a time based on the selected closing POW.

Controlled three-pole close for transformers

A transformer system including a transformer including a set of wye windings, a three-phase current transformer, a neutral-current transformer, and a controller. The three-phase current transformer outputs a first signal indicative of a three-phase current conducting through the set of wye windings and the three-phase current transformer. The neutral-current transformer couples the current flowing from the ground to the neutral node of the transformer, and outputs a second signal indicative of a neutral current conducting from the ground node to the neutral node of the transformer. The controller receives the first signal and the second signal, determines whether an external ground fault condition or an internal ground fault condition is present based on the three-phase current and the neutral current, and determines whether a wiring error is present for the three-phase current transformer or the neutral-current transformer based on the three-phase current and the neutral current.

Systems and methods for improving restricted earth fault protection

Detection of electric power generator stator ground fault conditions and protection of the generator due to such conditions is provided herein. In one embodiment, a generator protection element may calculate generator third harmonic voltage quantities using measurements from the generator terminals, and determine a stator ground fault condition using the calculated generator third harmonic voltage quantity. A tripping subsystem may issue a trip command based upon detection of a stator ground fault condition.

Generator stator ground protection using third harmonic

Electric power generator protection is secured by detecting wiring errors to an intelligent electronic device using terminal third voltages at the terminal (VT) and third harmonic voltages at the neutral (VN). When an angle between VTand VNis outside of an acceptable range, a wiring defect is detected, and certain protective operations are blocked. An alarm may be generated, facilitating personnel to identify and rectify the wiring defect. Wiring defects may further be detected when a torque calculated using VTand VNexceeds a predetermined error threshold. Security of protection elements is increased by detection of wiring defects that may have resulted in misoperation of the protection elements.

Growing community of inventors

Charlotte, NC, United States of America

Ritwik Chowdhury