Method and apparatus for detecting faults in buried insulated conductors

Claim 1

In a system for locating conductor-to-earth leakage paths through the insulation of buried conductors wherein said system comprises first means for producing a signal for application between a conductor of a buried insulated conductor and the medium in which it is buried, and second means for sensing said signal at discrete locations along the path of said conductor, for deriving a reference signal from said sensed signal and for phase comparing at least a portion of said sensed signal with said reference signal, an improvement in said system characterized in that, said signal produced by said first means comprises an alternating wave which is started at substantially the same phase angle at least once each time said second means is sensing said signal, and said second means comprises means for full-wave rectifying at least a portion of said sensed signal, means for dividing said rectified sensed signal by two with said dividing starting anew each time said sensed signal is started to thereby produce a reference signal and means for phase comparing said reference signal and at least a portion of said sensed signal.

Claim 6

A system for locating conductor-to-earth leakage paths through the insulation of buried conductors, said system comprising first means for applying a test signal between a conductor of a buried insulated conductor and the medium in which it is buried, second means for sensing said test signal at discrete locations along the path of said conductor, said test signal produced by said first means comprising an alternating signal which starts at substantially the same phase angle at least once each time said second means is in position for sensing said test signal, and third means for full-wave rectifying at least a portion of said sensed signal, fourth means for dividing said rectified sensed signal by two with said dividing starting anew each time said sensed signal is started to thereby produce a reference signal, and fifth means for phase comparing said reference signal with at least a portion of said sensed signal.

Claim 7

A system for locating conductor-to-earth leakage paths through the insulation of buried conductors, said system comprising first means for applying a test signal between a conductor of a buried insulated conductor and the medium in which it is buried, second means for sensing said test signal at discrete locations along the path of said conductor, said test signal produced by said first means comprising an alternating signal which starts at substantially the same phase angle at least once each time said second means is in position for sensing said test signal, and third means for full-wave rectifying at least a portion of said sensed signal, fourth means for dividing said rectified sensed signal by two with said dividing starting anew each time said sensed signal is started to thereby produce a reference signal, and fifth means for phase comparing said reference signal with at least a portion of said sensed signal.

Claim 11

A system for locating conductor-to-earth leakage paths through the insulation of buried conductors, said system comprising first means for applying between a conductor of a buried insulated conductor and the medium in which it is buried an alternating test signal which is interrupted at least once and restarted each time at substantially the same phase angle, second means for sensing said test signal at discrete locations along the path of said conductor, and third means for full-wave rectifying at least a portion of said sensed signal, fourth means for dividing said rectified sensed signal by two with said dividing starting anew each time said sensed signal is restarted to thereby produce a reference signal, and fifth means for phase comparing said reference signal with at least a portion of said sensed signal.

Claim 12

A system for locating conductor-to-earth leakage paths through the insulation of buried conductors, said system comprising first means for applying between a conductor of a buried insulated conductor and the medium in which it is buried an alternating test signal which is interrupted at least once and restarted each time at substantially the same phase angle, second means for sensing said test signal at discrete locations along the path of said conductor, and third means for full-wave rectifying at least a portion of said sensed signal, fourth means for dividing said rectified sensed signal by two with said dividing starting anew each time said sensed signal is restarted to thereby produce a reference signal, and fifth means for phase comparing said reference signal with at least a portion of said sensed signal.

Claim 16

A method for locating an electrical leakage path through insulating material surrounding an elongated conductor buried in a conducting medium, said method comprising the steps of: applying an alternating test signal between said conductor and said medium; sensing said test signal at discrete locations along the path of said conductor; controlling said test signal so that it starts at least once each time it is being sensed, full-wave rectifying at least a portion of said sensed signal, dividing by two said rectified sensed signal, with said dividing beginning anew with each starting of said sensed signal, to produce a reference signal, determining whether said sensed test signal and said reference signal are in an in-phase relationship or an out-of-phase relationship; and selecting said discrete locations until two adjacent locations are found where said relationships change from one to the other, whereby said leakage path is located as between said two adjacent locations.

Claim 17

A method for locating an electrical leakage path through insulating material surrounding an elongated conductor buried in a conducting medium, said method comprising the steps of: applying an alternating test signal between said conductor and said medium; sensing said test signal at discrete locations along the path of said conductor; controlling said test signal so that it starts at least once each time it is being sensed, full-wave rectifying at least a portion of said sensed signal, dividing by two said rectified sensed signal, with said dividing beginning anew with each starting of said sensed signal, to produce a reference signal, determining whether said sensed test signal and said reference signal are in an in-phase relationship or an out-of-phase relationship; and selecting said discrete locations until two adjacent locations are found where said relationships change from one to the other, whereby said leakage path is located as between said two adjacent locations.