| 摘要 |
PURPOSE:To detect a ground fault point from a change in the magnetization of a magnetic material by magnetizing the magnetic material which is beforehand provided along a cable by means of the ground-fault current flowing through the conductor and metallic sheath of the cable. CONSTITUTION:A cable is so constructed that a conductor 5 is enclosed by an insulating layer 6 and is further enclosed by a metallic sheath 7. When a ground- fault arises, the conductor 5 short circuits with the sheath 7 and the ground- fault current flows through the conductor 5 and the sheath 7. If a magnetic material 8 such as magnetic tape which is beforehand magnetized constant is provided along the cable in the case of laying the cable, current I flows to the conductor 5 and the sheath 7 and is interrupted in about several cycles in the event of short circuiting of the cable but since the current value is large, the generated magnetic field is fairly large. At the ground-fault point of the cable, the current flows radially and generates a magnetic field on the outside part of the cable, then the material 8 changes its magnetization state. If the change thereof is investigated, the ground-fault point is detected easily. |
