PURPOSE: To reduce the cost of a protective device by installing a primary winding surrounding each leg of a plurality of closed magnetic circuit cores in common and secondary windings separately wound on a plurality of other legs and mounting short circuits, in which fuses and selective switches are connected in series, to respective secondary winding.

CONSTITUTION: A plurality of two leg cores 1, 2, 3, 4 are arranged radially onto a base 5. A primary winding 6 is wound while surrounding the inner legs of each core in common, and connected to the load of a power system, etc. through outgoing lines 7. Secondary windings 10, 20, 30, 40 are wound separately on the outer legs of each core, and short circuits 11-42 in which fuses F and selective switches A are connected in series are set up respectively to the secondary windings. When an accident is generated in the primary winding 7, the fuse F is fusion-cut, and a secondary circuit is opened, thus increasing reactance, then limiting primary currents.