Patent ID: 8218278

Claim:
A current differential relay device that is installed at one end of a power transmission line and connected to another current differential relay device installed at another end of the power transmission line via two transmission paths, comprising: a sampling pulse signal generation part for generating a sampling pulse signal that indicates sampling timing of quantity data of electricity of each terminal; two timing difference measurement parts independent to each other and measuring a sampling pulse signal timing difference between the one end and the other end of the power transmission line independently for each of the transmission paths; a changeover part which detects a transmission defect of two timing difference measurement results of the two timing difference measurement parts and selects one timing difference measurement result having no transmission defect; a correction part for correcting the sampling timing on the basis of the selected timing difference measurement result transferred from the changeover part; an analog/digital conversion part for sampling quantity data of electricity of each of the terminals at the sampling timing and performing analog/digital conversion on the sampled quantity data of electricity; two transmission parts provided in parallel and communicating with the other end of the power transmission line through the two transmission paths and transmitting and receiving the quantity data of electricity of each of the terminals to and from the other end in the form of the digital data obtained through the analog/digital conversion; two current differential operation parts connected to each of the two transmission parts and performing 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; and a signal generation part for generating a trip signal from the current differential operation result of the two current differential operation parts, wherein the signal generation part is configured so that it generates a trip signal by using the logical conjunction of the two current differential operation results.