DIGITAL PROTECTIVE RELAY

PROBLEM TO BE SOLVED: To provide a digital protective relay that can avoid false fault detection of the protective relay and refrains from unnecessarily locking fault detection of the protective relay.SOLUTION: The digital protective relay includes: analog input circuits 20-1 to 20-n each for superposing a DC offset component A on a quantity of system electricity to be output; an A/D converter 13 for sampling each output from the analog input circuits 20-1 to 20-n at predetermined timings to output as digital data; and an operational circuit 14 for performing a relay operation. The operational circuit 14 has a fault detection section 19 for extracting the DC offset component A from the digital data of each output from the analog input circuits 20-1 to 20-n to produce a plurality of DC offset extracts, and computing a difference of the DC offset extract about each output from the analog input circuits 20-1 to 20-n from the DC offset component A to detect faults in the analog input circuits 20-1 to 20-n.