JPS57133366A - Detecting method for point of accident in power cable system - Google Patents

Abstract

PURPOSE:To locate a point of accident based on the amplitude of a current flowing through detection lines connected to a contact point, by making the contact point closed by a voltage caused in the secondary winding of a saturable reactor connected between two terminals of an insulation joint box at a time when a dielectric breakdown accident takes place. CONSTITUTION:Supposing that a grounding accident occurs at a point X in a section of the insulation joint box 3B1 in a phase B, a grounding current flows from a sheath to the earth through the saturable reactor 4B1 and a joint box 2B, while flowing also to the side of power source through a sheath in the phase B. Since the grounding current is always larger by far than a sheath current at the time of operation, a voltage caused in the secondary winding 5B1 increases sharply and thereby the contact point 6B1 is closed by means of a bimetal and the like. Accordingly, with a prescribed DC voltage impressed on the detection lines 7a and 7b, a current flows corresponding to the resistance values of the detection lines, which are proportional to a distance from a prescribed position to the insulation joint box 3B1. The occurence of the dielectric breakdown accident within the section of the insulation joint box 3B1 can be known with ease from the value of the current and thereby a time required for restoration can be shortened.