PURPOSE: To obtain a protective relay functionable stably with current level in saturable range of a CT, by providing a compensating functional section for compensating the current level fed from a detecting section based on the saturation characteristic of the current transformer(CT) and feeding the compensated current level to a comparing section between the detecting section and the comparing section.

CONSTITUTION: Current flowing through a main circuit 3 is transformed through a CT2 to produce corresponding current in the secondary circuit 4 of the CT2, then the produced current is detected through the detecting section 5 of a protective relay 1. The detected current is fed to a compensative functional section 10 where it is converted into a current level corresponding to an ideal characteristic. When a value IB for compensating the ideal characteristic is set previously, as a function of a secondary current IBO, in the compensative functional section 10, IB corresponding to the secondary current IBO is added to the detected secondary current IBO in the compensative functional section 10 even if the primary current enters into saturable range, to produce IBI having ideal characteristic proportional to the primary current IB, and IB is fed to a comparing section 6.