<p>An apparatus for judging whether a signal of insulating deterioration generated due to deterioration in insulation of an object of measurement is superimposed on the current flowing through this object.</p><p>An apparatus equipped with a first coil composed of two primary windings wound with the same number of turns and in the same direction and a secondary winding, the primary and secondary windings being wound on a core whose magnetomotive force and magnetic flux density are roughly proportional to each other; a second coil composed of a primary winding and a secondary winding both wound as a core whose magnetomotive force and magnetic flux density are roughly proportional to each other, and an impedance circuit.</p>
