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Locating sheath faults in underground power supply cables

  • US 4,370,610 A
  • Filed: 08/27/1979
  • Issued: 01/25/1983
  • Est. Priority Date: 08/30/1978
  • Status: Expired due to Term
First Claim
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1. A method of locating an earth fault on a sheath of an underground cable comprising the steps of applying pulses of direct current to said sheath at one location on the cable;

  • searching at spaced locations along the route of the cable for the magnetic field due to a fault current to earth flowing in said sheath which is produced by said applied d.c. pulses using a portable magnetometer, with a visual indicator; and

    at each of said spaced locations, comparing the visual indications on the magnetometer with the periods of application of the pulses to the sheath by transmitting signals indicative of the periods of current application and using, with the portable magnetometer, a portable receiver arranged to receive the transmitted signals so that the magnetometer indications can be compared with the received signals until said visual indications on the magnetometer and said periods of application of the pulses substantially correspond, thereby identifying the approximate position of the earth fault along the cable.

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