Abstract: A current differential relay comprises: an interface section; a quantization section; a communication section; and a difference calculation section. The quantization section quantizes current received by the interface section and converts it to first current data. The communication section, in the case where this relay is a representative current differential relay of a first group, transmits second current data from another current differential relay belonging to the first group and the first current data jointly to a representative current differential relay belonging to the second group, receives third current data from the representative current differential relay, and transmits the third current data to the other current differential relays. A difference calculation section executes a current difference calculation based on the first to third current data.

Abstract: A current differential relay comprises: an interface section; a quantization section; a communication section; and a difference calculation section. The quantization section quantizes current received by the interface section and converts it to first current data. The communication section, in the case where this relay is a representative current differential relay of a first group, transmits second current data from another current differential relay belonging to the first group and the first current data jointly to a representative current differential relay belonging to the second group, receives third current data from the representative current differential relay, and transmits the third current data to the other current differential relays. A difference calculation section executes a current difference calculation based on the first to third current data.

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: A current differential relay device is described. The device has two transmission parts provided in parallel and communicating with an other end of a power transmission line through two transmission paths and transmitting and receiving a quantity data of electricity of each of the terminals to and from an other end in the form of the digital data obtained through analog/digital conversion. Two current differential operation parts are connected to each of the two transmission parts and perform a current differential operation independently for each of the transmission paths by using the digital data of the quantity data of electricity of the one end of the power transmission line and of the other end of the power transmission line. A signal generation part generates a trip signal from the current differential operation result of the two current differential operation parts.

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: Two current differential relay devices 1 are installed at each terminal 3 of a two-terminal power transmission line 2, and connected to each other via two transmission paths 5 and 6, and perform current differential operations by transmitting and receiving the quantity data of electricity to each other. In the current differential relay device 1, two transmission means 14 normally each perform communications with the current differential relay device 1 of the other end of the power transmission line in parallel through the two transmission paths 5 and 6. Two current differential operation means 14 are connected to the two transmission means 14 respectively and perform independently two-series of current differential operations independently for each series associated with each of the transmission paths 5 and 6.

Abstract: A digital protective relay comprises a protective relay arithmetic processing unit for judging, based on a relay judgement quantity obtained by converting a system electric quantity into a digital value, whether in an operating state or in a non-operating state, and a time synchronizing unit for inputting a time reference signal from outside and synchronizing an internal timer of the digital protective relay with an external reference time. The time synchronizing unit includes an A/D converting unit for A/D converting the time reference signal inputted from outside with a resolution of at least 2 bits, and a decoding unit for decoding a time code signal by making a judgement as to a magnitude of the time reference signal with respect to a digital value obtained by the A/D converting unit.

Abstract: A digital protective relay system is capable of making sampling timing the same among plural protective relay device which operate independent from each other by using a signal from a GPS satellite. The sampling timing is made the same regardless of the time lag from which it is sent downstream with the concomitant transmission delay time in the case of data communications, or regardless of the time lag from which it is sent upstream.

Abstract: A digital protective relay system is capable of making sampling timing the same among plural protective relay device which operate independent from each other by using a signal from a GPS satellite. The sampling timing is made the same regardless of the time lag from which it is sent downstream with the concomitant transmission delay time in the case of data communications, or regardless of the time lag from which it is sent upstream.