GB657313A - Manufacture of multiconductor electric cables and apparatus for use therein - Google Patents

Abstract

657,313. Detecting faults. WESTERN ELECTRIC CO., Inc. June 10, 1948, No. 15693. Convention date, June 11, 1947. [Class 37] To detect breaks or short-circuits in a pair of twisted insulated wires 11, 12, Fig. 1, the insulation 10 containing moisture, a direct current from G is applied between the two wires for a time sufficient to produce electrolytic polarisation of the insulating material, and after being disconnected the residual polarisation is measured by connecting a voltmeter V. An ammeter A indicates if the wires 11, 12 are in connection, while a reading of e.g. 1¢ volts on V indicates that the wires are intact and that the insulation will be satisfactory when dry ; a lower voltage reading on V will indicate either a break or a short-circuit. If any appreciable current flows from the generator G, a relay opens contacts 21. In a modification, the voltmeter V is replaced by two voltmeters V, Fig. 2, which can be connected across each wire, the switch 16 is adapted to connect the two wires together. In operation, switch 14 is closed, a large deflection on voltmeter 18 indicating a short-circuit; if there is no shortcircuit, switch 14 is opened after e.g. 30 minutes and switches 19, 20 closed; a break in one wire is stated to produce a higher reading in the voltmeter 117 or 217 connected across it; if both voltmeters read high, e.g. 0.5 volts, both wires are stated to be broken; if both voltmeters read low, e.g. 0.2 volts, switch 16 is closed, and no detectable change in readings stated to indicate a short circuit.