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 merging unit includes a processing unit which processes an analog signal from a power system and outputs digital data indicating a state of the power system, and a communication unit which communicates with an external device via a communication line. The processing unit includes a first conversion unit which converts an analog signal of current or voltage of the power system to digital data with a first sample rate, and a second conversion unit which converts the analog signal to digital data with a second sample rate lower than the first sample rate. The processing unit is configured to store the digital data with the first sample rate, over a prescribed period which is based on timing at which the processing unit receives a prescribed signal via the communication unit, and to transmit the digital data with the second sample rate, via the communication unit.

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: 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 protection control apparatus includes a control-signal output circuit configured to generate a sampling signal in synchronization with a 1PPS signal and output, as a control signal, data numbers cyclically counted up every time the sampling signal is generated and the sampling signal and a data output unit configured to convert a system electrical quantity into digital data based on the control signal and output the digital data. The control-signal output circuit includes a number-of-clocks calculating circuit configured to calculate a second number of clocks and a third number of clocks and a synchronization control unit configured to calculate a difference between a first number of clocks and a second number of clocks, control a cycle of the sampling signal based on the difference and the third number of clocks, and synchronize generation timing of the sampling signal with the 1PPS signal.

Abstract: A protection control apparatus includes a control-signal output circuit configured to generate a sampling signal in synchronization with a 1PPS signal and output, as a control signal, data numbers cyclically counted up every time the sampling signal is generated and the sampling signal and a data output unit configured to convert a system electrical quantity into digital data based on the control signal and output the digital data. The control-signal output circuit includes a number-of-clocks calculating circuit configured to calculate a second number of clocks and a third number of clocks and a synchronization control unit configured to calculate a difference between a first number of clocks and a second number of clocks, control a cycle of the sampling signal based on the difference and the third number of clocks, and synchronize generation timing of the sampling signal with the 1PPS signal.

Abstract: A sampling frequency control method includes a difference calculating step ST1 of calculating the difference between sampled values obtained through sampling of an AC quantity of electricity of a power system at time points that are separated by a prescribed time period of the AC quantity of electricity; an effective value calculating step ST2 of calculating an effective value of the AC quantity of electricity and an effective value of the difference; a ratio calculating step ST3 of calculating the ratio K of the effective value of the difference to the effective value of the AC quantity of electricity; and a control step of controlling the sampling frequency by controlling the sampling period on the basis of the calculated ratio K so that it follows the frequency of the AC quantity of electricity.

Abstract: A PCM current differential relay is provided with a sampling synchronizing circuit unit which, on the basis of a deviation in sampling timing between digital current data of a local end and digital current data of a remote end inputted from the remote end, synchronizes the digital current data of the local end and the digital current data of the remote end. In accordance with the digital current data of the local end and the digital current data of the remote end synchronized by the sampling synchronizing circuit unit, relay operation of the PCM current differential relay is carried out by a relay operation unit of the PCM current differential relay.

Abstract: A sampling frequency control method includes a difference calculating step ST1 of calculating the difference between sampled values obtained through sampling of an AC quantity of electricity of a power system at time points that are separated by a prescribed time period of the AC quantity of electricity; an effective value calculating step ST2 of calculating an effective value of the AC quantity of electricity and an effective value of the difference; a ratio calculating step ST3 of calculating the ratio K of the effective value of the difference to the effective value of the AC quantity of electricity; and a control step of controlling the sampling frequency by controlling the sampling period on the basis of the calculated ratio K so that it follows the frequency of the AC quantity of electricity.