Abstract: A power system may comprise two or more transformers operating in parallel. A voltage differential may exist between the transformers, which may create a circulating current in the power system. The system voltage of the power system may be modified by performing a tap change operation on one or more of the transformers. The tap change operation may be configured to minimize the circulating current. The circulating current may be minimized by determining the bias between the transformers using an angular difference between the transformer currents. The angular difference may be calculated using time-aligned measurement data. A tap change operation configured to modify the system voltage, while minimizing circulating current, may be determined using the transformer bias.

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 distributed busbar protection system using time-stamped data gathered from measurement devices in an electrical power system bus arrangement by respective intelligent electronic devices (IEDs). The IEDs may derive the timestamp information from a clock or other time source, which may be synchronized to a common time source and/or an absolute time. The time-stamped measurement data may be used by a protection device to monitor and/or protect the electrical power system. The protection device may include a real-time vector processor, which may time-align the time-stamped data, determine one or more bus differential protection zones, and implement a differential protection function within each of the protection zones. One or more protective control signals may be transmitted to the IEDs to trip the corresponding breakers and clear the bus fault.

Abstract: An apparatus, system and method in an electrical system using power system information or data associated therewith having a time component associated therewith sampled or obtained from the electrical system at a local and a remote location, wherein the local and remote data are time aligned and used to provide control, monitoring, metering, and/or automation to the electrical system. The local IED may be adapted to receive power system data from the remote IED, time align the local and remote synchronized power system data, and perform math operations on the local and remote power system data.

Abstract: Provided is a compensated inverse-time undervoltage load shedding system and method for use in an electrical power system. The compensated inverse-time undervoltage load shedding system includes a compensation element for determining a compensated value and an inverse-time undervoltage element operatively coupled to the compensation element and enabled based on the compensated value. When enabled, the inverse-time undervoltage element calculates a load shedding time delay value based on the compensated value, and determines a load shedding signal based on the load shedding time delay value. An associated load of the electrical power system is shed based on the load shedding signal. The compensation element may determine the compensated value using a voltage magnitude, a rate-of-change of power system voltage over time, a weighted rate-of-change of power system voltage over time, a current magnitude, a weighted current magnitude, and an impedance phasor value, to name a few.

Abstract: A dynamically configurable relay element configured to protect an electrical system, including a dynamically calculated relay operating quantity, a dynamically calculated relay pickup setting, a dynamically calculated time dial, a plurality of dynamically calculated variables that define a characteristic of the dynamically configurable relay element, and a dynamically calculated operating time, the dynamically calculated operating time based on the dynamically calculated relay operating quantity, the dynamically calculated relay pickup setting, the dynamically calculated time dial and the plurality of dynamically calculated variables. The relay element may be an inverse-time overcurrent element, an instantaneous overcurrent element, an adaptive pickup overcurrent element, and inverse-time overvoltage element, a voltage restrained overcurrent element, and an inverse-time undervoltage element.

Abstract: A State and Topology Processor (STP) may be communicatively coupled to one or more intelligent electronic devices (IEDs) communicatively coupled to a electrical power system to obtain one or more current measurements, voltage measurements, and dynamic topology data therefrom. The STP may receive the measurement data and may determine a current topology and a voltage topology therefrom. A current processor may use the current topology and the current measurements to refine the measurements, perform KCL, unbalance, symmetrical component, and consistency checks on the electrical power system. The voltage processor may use the voltage topology and the voltage measurements to perform similar checks on the electrical power system. One or more alarms may be generated responsive to the checks. The data may be displayed to a user in a display of a human machine interface and/or may be transmitted to a user programmable task module, and/or an external control unit.

Abstract: A power system oscillation detection device is provided for use in an electric power system. A plurality of sample signals are acquired from the electrical power system via a plurality of intelligent electronic devices (IEDs) in communication with the power system. The power system oscillation detection device includes a real-time modal analysis module, a real-time mode identification module, and real-time decision and control logic. The real-time modal analysis module calculates modes of at least one of the signals, each mode including mode information. The real-time mode identification module together with the real-time decision and control logic determines, from the mode information, whether there is an undesirable oscillation in the electric power system and activates a remedial action.

Abstract: A device is provided for monitoring through-fault current in an electric transformer on an electrical power system. The device generally includes a magnitude calculator for calculating the magnitude of current (e.g., a root means square value of current or magnitude of a fundamental of current) based on the current through the electric transformer. A through-fault energy calculator is further provided which is coupled to the magnitude calculator for calculating a through-fault energy value based on the magnitude of current or the calculated current through the transformer. An accumulator is coupled to the through-fault energy calculator for accumulating a plurality of through-fault energy values, and an alarm coupled to the accumulator for indicating that the accumulated through-fault energy values exceed a selected threshold.

Abstract: A set of current measurements may be transmitted from a remote Intelligent Electronic Device (IED) to a local IED. The current measurements may comprise a timestamp and/or be associated with timestamp information to allow the local IED to time align the local current measurement with the remote current measurement. The local IED may detect a fault within the power system segment defined by the local and remote IEDs by comparing an operating current to a scaled restraint current. A fault may also be detected by comparing the operating current to a scaled nominal current. The operating and restraint currents may be derived from the local and remote current measurements. The restraint current scale may be derived from the characteristics of the local and/or remote IED. The current measurements may correspond to a negative-sequence component and/or a zero-sequence component of a three-phase current measurement set.

Abstract: A first intelligent electric device (IED) may be placed at a first location in an electrical power system and a second IED may be placed at a second location in the electrical power system. Voltage measurements may be received from the first and second IEDs. The measurements may be time aligned and used to calculate an angle difference between the first location and the second location in the electrical power system. A slip frequency and acceleration may be derived from the angle difference. The angle difference, slip frequency, and acceleration may be used to detect an out-of-step (OOS) condition in the electrical power system and/or a power swing between the first location and the second location in the electrical power system. The angle difference, slip frequency, and acceleration may also be used to predicatively detect OOS conditions.

Abstract: A device is provided for monitoring and controlling various power system device and elements. The device generally includes a communications channel for receiving phasor data associated with a location on the power system. The device further includes a logic engine which performs scalar, vector and/or other complex calculation based on the phasor data to provide control data or an output signal for effecting the various other power system devices or elements to provide local or wide area protection, control, and monitoring to maintain power system stability.

Abstract: An apparatus and method estimates a plurality of synchronized phasors at predetermined times referenced to an absolute time standard in an electrical power system. The method includes acquiring and determining a frequency of a power system signal, sampling the power system signal at a sampling interval rate based on a frequency of the power system signal to form signal samples, and generating a plurality of acquisition time values based on an occurrence of each of the signal samples at a corresponding plurality of different times referenced to the absolute time standard. The method further includes adjusting a phasor of each of the signal samples based on a time difference between a corresponding selected acquisition time value and a predetermined time referenced to an absolute time standard to form the plurality of synchronized phasors.

Abstract: An apparatus and method estimates a plurality of synchronized phasors at predetermined times referenced to an absolute time standard in an electrical power system. The method includes acquiring and determining a frequency of a power system signal, sampling the power system signal at a sampling interval rate based on a frequency of the power system signal to form signal samples, and generating a plurality of acquisition time values based on an occurrence of each of the signal samples at a corresponding plurality of different times referenced to the absolute time standard. The method further includes adjusting a phasor of each of the signal samples based on a time difference between a corresponding selected acquisition time value and a predetermined time referenced to an absolute time standard to form the plurality of synchronized phasors.

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: An apparatus, system and method in an electrical system using power system information or data associated therewith having a time component associated therewith sampled or obtained from the electrical system at a local and a remote location, wherein the local and remote data are time aligned and used to provide control, monitoring, metering, and/or automation to the electrical system. The local IED may be adapted to receive power system data from the remote IED, time align the local and remote synchronized power system data, and perform math operations on the local and remote power system data.

Abstract: An apparatus and method estimates a plurality of synchronized phasors at predetermined times referenced to an absolute time standard in an electrical power system. The method includes acquiring and determining a frequency of a power system signal, sampling the power system signal at a sampling interval rate based on a frequency of the power system signal to form signal samples, and generating a plurality of acquisition time values based on an occurrence of each of the signal samples at a corresponding plurality of different times referenced to the absolute time standard. The method further includes adjusting a phasor of each of the signal samples based on a time difference between a corresponding selected acquisition time value and a predetermined time referenced to an absolute time standard to form the plurality of synchronized phasors.

Abstract: Disclosed is an apparatus and method for detecting a loss of a current transformer connection coupling a protective relay to a power system element of a three-phase power system and providing a plurality of secondary current waveforms of the three-phase power system to the protective relay. The apparatus includes a first logic circuit and a second logic configured to provide corresponding first and second binary signals in response to respective comparisons of calculated current value(s) of a plurality of like-phase digitized current sample streams to respective threshold values. The apparatus also includes a set reset flip-flop having a set input adapted to receive the first and second binary signals to provide a third binary signal. The third binary signal indicates loss of a current transformer connection when the set input is asserted and indicates no loss of a current transformer connection when the reset input is asserted.

Abstract: A dynamically configurable relay element configured to protect an electrical system, including a dynamically calculated relay operating quantity, a dynamically calculated relay pickup setting, a dynamically calculated time dial, a plurality of dynamically calculated variables that define a characteristic of the dynamically configurable relay element, and a dynamically calculated operating time, the dynamically calculated operating time based on the dynamically calculated relay operating quantity, the dynamically calculated relay pickup setting, the dynamically calculated time dial and the plurality of dynamically calculated variables. The relay element may be an inverse-time overcurrent element, an instantaneous overcurrent element, an adaptive pickup overcurrent element, and inverse-time overvoltage element, a voltage restrained overcurrent element, and an inverse-time undervoltage element.

Abstract: Provided is a system for transmitting synchronized phasors over a wide area network. The system generally includes a plurality of phasor measurement units (PMUs). Each of the PMUs are associated with a secured portion of a power system and measure power system data from the secured portion of the power system associated therewith. The power system data is associated with a time-element. A power system data concentrator is further provided in communication with the phasor measurement units such that it aggregates and time-correlates the power system data. A server is further provided in communication with the power system data concentrator. The server includes a program for transferring the aggregated time-correlated power system data from the secured portion of the power system to a non-secure network.