Protection relay and disconnection detection method thereof

The present invention relates to a protection relay for detecting disconnection in a circuit to which a converter is connected, the protection relay comprising: a disconnection sensing unit comprising a plurality of nodes connected to both ends of the output of the converter and a reference voltage generating unit for forming a reference voltage, a plurality of resistors forming divider resistors and connecting the plurality of nodes and the reference voltage generation unit; a sensing voltage generation unit that applies a voltage for forming a predetermined voltage difference with respect to the reference voltage to the disconnection sensing unit; and a disconnection determination unit that is connected to a first node of the plurality of nodes, detects whether or not at least one of the converter and a circuit connected to the converter is disconnected on the basis of a voltage signal detected from the first node, and determines whether or not the converter is disconnected by the magnitude of the voltage s