A sensor for measuring current of the Rogowski-torus type including a carrier made of a magnetic materials and a secondary winding wound on the carrier in order to deliver an electrical signal representative of a current flowing in a conductor passing through the interior of the torus. The carrier is made essentially of a moulded rigid plastic material and includes at least one exterior recess distributed over the length of the body of the carrier. The recess includes at least two grooves that are separated by a partition. The protecting and measuring device and the electric circuit breaker include such a current sensor.