Abstract: A current differential relay apparatus includes a first relay and a second relay. The first relay calculates a first differential current and a first suppression current, using a first current and a second current, and performs a ratio differential relay operation based on the first differential current and the first suppression current. The second relay calculates a maximum of results of add operations of the first current and the second current as a second differential current, calculates an add operation of the maximum of the first current and a maximum of the second current as a second suppression current, and performs a ratio differential relay operation based on the second differential current and the second suppression current. The current differential relay apparatus includes an output controller that outputs an operation signal based on results of operations performed by the first and second relays.

Abstract: A protection relay comprises a digital processing unit including: a first filter to eliminate a DC component in the time-series data, the first filter having a first window length; a second filter to eliminate a DC component in the time-series data, the second filter having a second window length shorter than the first window length; and a coefficient calculation unit to multiply an amplitude value of an output signal of the first filter and an amplitude value of an output signal of the second filter by first and second coefficients respectively, and integrate multiplication results. An operation determination is performed based on an output of the coefficient calculation unit. The first coefficient is decreased and the second coefficient is increased when a failure of the power system is detected, and thereafter, the first coefficient and the second coefficient are changed with a lapse of time.

Abstract: A current differential relay apparatus includes a first relay and a second relay. The first relay calculates a first differential current and a first suppression current, using a first current and a second current, and performs a ratio differential relay operation based on the first differential current and the first suppression current. The second relay calculates a maximum of results of add operations of the first current and the second current as a second differential current, calculates an add operation of the maximum of the first current and a maximum of the second current as a second suppression current, and performs a ratio differential relay operation based on the second differential current and the second suppression current. The current differential relay apparatus includes an output controller that outputs an operation signal based on results of operations performed by the first and second relays.

Abstract: A circuit breaker failure protection relay includes an input circuit to which an opening command from a first circuit breaker is input, and a circuit breaker failure detection element configured to compare a magnitude of a current detection signal in a power system with a setting value to make a determination about an overcurrent. The circuit breaker failure detection element is capable of changing the setting value to a first value and a second value that is larger than the first value according to a switching signal. The circuit breaker failure protection relay is configured to, when the opening command is input and when the circuit breaker failure detection element determines that an overcurrent occurs, output an opening command for the second circuit breaker in a neighborhood of the first circuit breaker.

Abstract: In a fault waveform recording device, a first storage stores data detected in a power system, the data being up-to-date and indicating an electrical quantity during a first period, and halts the updating of the data stored in the first storage after a second period has elapsed since an abnormality detection time at which an abnormality in the power system is detected. The second period is shorter than the first period. First operation unit stores data in a first interval as is into a second storage, among the data of the first period stored in the first storage after the updating of the data stored in the first storage is halted, the first interval including the abnormality detection time, and decimates data in a second interval different from the first interval.

Abstract: In a protective relay device, a current differential relay computation unit determines whether or not a fault has occurred within a protected section based on an operating quantity and a restraint quantity. A disconnection detection unit computes a first amount of difference by subtracting the operating quantity a certain time period ago from the operating quantity at a present point in time, computes a second amount of difference by subtracting the restraint quantity the certain time period ago from the restraint quantity at the present point in time, and determines that a disconnection has occurred at one of first and second current transformers when a first determination condition that an absolute value of a sum of the first amount of difference and the second amount of difference is equal to or smaller than a first set value is satisfied.

Abstract: In an intelligent electronic device, a first receiving circuit receives first time-series data at a first sample rate representing the electrical quantity of an electric power system from a merging unit. An up converter converts the first time-series data into second time-series data having a second sample rate higher than the first sample rate by interpolating the first time-series data. A down converter converts the second time-series data into third time-series data having a third sample rate lower than the first sample rate by periodically extracting a data point at any changeable sample time from the second time-series data. A relay computer performs protective relay computation using third time-series data.

Abstract: A protection relay comprises a digital processing unit including: a first filter to eliminate a DC component in the time-series data, the first filter having a first window length; a second filter to eliminate a DC component in the time-series data, the second filter having a second window length shorter than the first window length; and a coefficient calculation unit to multiply an amplitude value of an output signal of the first filter and an amplitude value of an output signal of the second filter by first and second coefficients respectively, and integrate multiplication results. An operation determination is performed based on an output of the coefficient calculation unit. The first coefficient is decreased and the second coefficient is increased when a failure of the power system is detected, and thereafter, the first coefficient and the second coefficient are changed with a lapse of time.

Abstract: A ground fault overvoltage relay device is configured to: determine whether or not a first condition is satisfied, the first condition being that at least two of line voltages between respective two phases are less than or equal to a first threshold value; determine whether or not a second condition is satisfied, the second condition being that a ratio between a minimum value of the line voltages between the respective two phases and a minimum value of the respective phase voltages is less than or equal to a second threshold value; determine whether or not a third condition is satisfied, the third condition being that the zero-phase voltage is greater than a third threshold value; and lock a ground fault detection output when the first condition is satisfied, or when the second condition is satisfied and the third condition is not satisfied.

Abstract: A process bus-applied protection system includes a process bus, a plurality of MUs (merging units), and a plurality of IEDs (intelligent electric devices). Each of the MUs is configured to sample a current and a voltage of a power system at timing synchronized with a time synchronization signal received through the process bus. Each of the IEDs is configured to be capable of outputting the time synchronization signal to the process bus by serving as a transmission source, and receiving, through the process bus, the time synchronization signal from another IED. The plurality of IEDs have a predetermined priority. Each of the IEDs is configured, when the IED does not receive the time synchronization signal from an IED having a higher priority than that of the IED and serving as a transmission source, to output the time synchronization signal to the process bus by serving as a transmission source.

Abstract: In an intelligent electronic device, a first receiving circuit receives first time-series data at a first sample rate representing the electrical quantity of an electric power system from a merging unit. An up converter converts the first time-series data into second time-series data having a second sample rate higher than the first sample rate by interpolating the first time-series data. A down converter converts the second time-series data into third time-series data having a third sample rate lower than the first sample rate by periodically extracting a data point at any changeable sample time from the second time-series data. A relay computer performs protective relay computation using third time-series data.

Abstract: A testing device tests an intelligent electronic device of a power system. A PC generates failure data by performing: simulation calculation for a CT and a PT with respect to current waveform data of a current transformer and voltage waveform data of a potential transformer based on a characteristic of an instrument transformer; and simulation calculation for an MU with respect to the current waveform data of the current transformer and the voltage waveform data of the potential transformer based on a characteristic of the MU. The testing device acquires device information data indicating a circuit breaker of the power system, in synchronization with the failure data. The testing device transmits the failure data and the device information data to the intelligent electronic device via a process bus in accordance with a setting of outputting data to the process bus and a setting of sampling.

Abstract: A circuit breaker failure protection relay includes an input circuit to which an opening command from a first circuit breaker is input, and a circuit breaker failure detection element configured to compare a magnitude of a current detection signal in a power system with a setting value to make a determination about an overcurrent. The circuit breaker failure detection element is capable of changing the setting value to a first value and a second value that is larger than the first value according to a switching signal. The circuit breaker failure protection relay is configured to, when the opening command is input and when the circuit breaker failure detection element determines that an overcurrent occurs, output an opening command for the second circuit breaker in a neighborhood of the first circuit breaker.

Abstract: In a fault waveform recording device, a first storage stores data detected in a power system, the data being up-to-date and indicating an electrical quantity during a first period, and halts the updating of the data stored in the first storage after a second period has elapsed since an abnormality detection time at which an abnormality in the power system is detected. The second period is shorter than the first period. First operation unit stores data in a first interval as is into a second storage, among the data of the first period stored in the first storage after the updating of the data stored in the first storage is halted, the first interval including the abnormality detection time, and decimates data in a second interval different from the first interval.

Abstract: A ground fault overvoltage relay device is configured to: determine whether or not a first condition is satisfied, the first condition being that at least two of line voltages between respective two phases are less than or equal to a first threshold value; determine whether or not a second condition is satisfied, the second condition being that a ratio between a minimum value of the line voltages between the respective two phases and a minimum value of the respective phase voltages is less than or equal to a second threshold value; determine whether or not a third condition is satisfied, the third condition being that the zero-phase voltage is greater than a third threshold value; and lock a ground fault detection output when the first condition is satisfied, or when the second condition is satisfied and the third condition is not satisfied.

Abstract: In a protective relay device, a current differential relay computation unit determines whether or not a fault has occurred within a protected section based on an operating quantity and a restraint quantity. A disconnection detection unit computes a first amount of difference by subtracting the operating quantity a certain time period ago from the operating quantity at a present point in time, computes a second amount of difference by subtracting the restraint quantity the certain time period ago from the restraint quantity at the present point in time, and determines that a disconnection has occurred at one of first and second current transformers when a first determination condition that an absolute value of a sum of the first amount of difference and the second amount of difference is equal to or smaller than a first set value is satisfied.

Abstract: A protective control system includes an IED (Intelligent Electric Device) and a merging unit. The merging unit receives a current/voltage waveform signal of a power system, and outputs a digitally converted analog data to a process bus via a communication line as a serial signal. The IED is configured to be capable of transmitting a trip instruction to the merging unit using both the process bus and a station bus. The trip instruction is for outputting the trip signal. Preferably, each of the merging unit and the IED includes a switching circuit that makes switching to the station bus when an error is detected in the process bus communication. In the event of the process bus error, communication made by the process bus is switched to communication made by the station bus. Accordingly, reliability of the process bus can be improved.

Abstract: A process bus-applied protection system includes a process bus, a plurality of MUs (merging units), and a plurality of IEDs (intelligent electric devices). Each of the MUs is configured to sample a current and a voltage of a power system at timing synchronized with a time synchronization signal received through the process bus. Each of the IEDs is configured to be capable of outputting the time synchronization signal to the process bus by serving as a transmission source, and receiving, through the process bus, the time synchronization signal from another IED. The plurality of IEDs have a predetermined priority. Each of the IEDs is configured, when the IED does not receive the time synchronization signal from an IED having a higher priority than that of the IED and serving as a transmission source, to output the time synchronization signal to the process bus by serving as a transmission source.

Abstract: MUs and IEDs are included. Each of the IEDs includes a signal control unit that derives the time difference between the sampling timings in the MUs on the basis of digital data from one end of a protection area and digital data from the other end of the protection area, controls the cycle of a sampling-timing control signal to eliminate this time difference, and outputs this controlled sampling-timing control signal to a merging unit corresponding to each computation unit. Each of the MUs includes a control-signal output circuit that generates a sampling signal synchronized with the sampling-timing control signal from the IEDs and outputs this sampling signal as a control signal, and a data output unit that converts an electrical input to digital data and outputs the digital data.

Abstract: A digital protection relay includes: an input conversion unit configured to receive a signal showing a quantity of electricity in an electric power system as an analog signal; and an analog-to-digital conversion unit. The digital protection relay is configured to cause a processing control unit to perform protection calculation based on the digital signal. The processing control unit functions as: a protection calculation unit configured to perform the protection calculation using an offset voltage value; an input data acquisition unit configured to sequentially acquire input data, which is converted into a digital signal, in accordance with sampling timing; and an offset value calculation unit configured to calculate the offset voltage value based on sampling values at a timing at which a change occurs in a polarity of a differential amount among the input data in at least one cycle.