DC COMPONENT DETECTING APPARATUS

PURPOSE:To make it possible to detect a minute DC component in comparison with AC component by providing two current transformers having the different exciting characteristics in an AC current path. CONSTITUTION:Current transformers 1 and 2 are provided at a conductor 3 of an AC electric circuit. Secondary currents I12 and I22 are inputted into a secondary-current comparing circuit 4, and a differential current I2 is outputted. When the exciting characteristics of the current transformers 1 and 2 are different at this time, distortion is generated in the secondary current from one current transformer. The difference occurs between the wave crest values of the currents I12 and I22. Therefore, the differential current I2 has the ansymmetrical waveform in the positive and negative directions. When the nonlinear rate is made high, the wave crest value of the differential current which is higher than the DC component is obtained. When the load of the current transformer 1 is made larger than the load of the current transformer 2 and the amplitude of the exciting current is made large, sensitivity can be further increased, and the DC component can be detected.