The present design is a current transformer: relates to (CT Current Transformer), a current transducer protection circuit for a secondary side of the overload blocking current converter is disclosed. The devised to achieve this, but detecting no-load condition of the second converter, and on the basis of the no-load detection result provided with a protection element to short-circuit the output terminals of the second converter, the output terminal of the protection element is a secondary converter maintaining the secondary side load of the hameuroseo composed of a parallel connection of TNR, the current transformer in a no-load condition, as provided with a protective circuit so that the opposite ends of the secondary converter short circuit so that the electromotive force which acts as a core from the primary converter decreases, a current transformer when the check not only alleviates the need to have each short-circuit the circuit connected to the second converter, to obtain the effect of protecting the current transformer.