The utility model provides a distribution lines fault detection device, includes base, straight -through current transformer, end cover and sealed cowling, and the sealed cowling is fixed and is inlayed the device at the up end of base and with the end cover in its inner chamber, and corresponding location portion is established, the mutual -inductor holds the chamber in corresponding threading groove on base, end cover and sealed cowling on base, the end cover, straight -through current transformer divide into, lower each semi -ring, the semi -ring is fixed on the base down, go up the semi -ring through clamping the slide assembly on the end cover, it can follow the vertical direction removal to clamp the slide, establish the screw hole that the assembly compressed tightly the double -screw bolt on the end cover, it establishes the clamp plate to clamp the slide top, it establishes the spring to compress tightly between double -screw bolt and clamp plate, its couple current transformer's design makes the current transformer who gets the electricity and detect by the difference accomplish, the contradiction between induction electricity -taking and the detection has effectively been solved, the embedded assembly of current induction ware and the outside seal effect of sealed cowling, can guarantee the precision of mutual -inductor and the stability of long -time running, the reliability.