Pipe current detector with plural magnetic flux detectors

• US 4,134,061 A
• Filed: 02/02/1977
• Issued: 01/09/1979
• Est. Priority Date: 02/02/1977
• Status: Expired due to Term

• Current Assignee: Howard S. Gudgel
• Original Assignee: Howard S. Gudgel
• Inventors: Gudgel, Howard S.
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US05/764,727
• Time in Patent Office: 706 Days
• Field of Search: 324/54, 324/67, 324/3, 324/52, 324/71 R, 324/37, 324/40, 324/241, 324/242, 324/243
• US Class Current: 324/559
• CPC Class Codes: G01R 31/08 Locating faults in cables, transmission lines, or networks
• CPC Class Codes: G01V 3/02 operating with propagation of electric current

Abstract

Apparatus for measurement, above the surface of the ground, of an electrical current flowing in a buried pipeline, comprises a pair of magnetic flux detectors oriented with their axes vertical, and spaced apart, in a frame, which is moved along the earth at a substantially constant elevation above the surface, with the plane through the two vertical detectors substantially perpendicular to the direction of the pipe. Means are provided, including a vertical core and coil centered on the frame, for indicating the position of the frame laterally with respect to the buried pipe. There is also a second core and coil displaced laterally from the first core and coil, for determining the depth of the pipe below the frame. When the frame is centered over the pipe and there is current in the pipe, flux will pass upwardly through a first flux detector core and downwardly through the second flux detector core. One or a plurality of coils and suitable measuring instruments can determine the magnitude of the flux through the core and therefore, the magnitude and direction of the current flowing in the pipe.

Claims

1. Apparatus for detecting and determining the amplitude and direction of any electric current that may be flowing axially in a buried pipeline in the earth, at a selected point along said pipeline, comprising:

(a) first and second magnetic flux detectors spaced apart horizontally a selected distance;

(b) said detectors mounted with axes vertical, on a non-magnetic frame, the plane of which is substantially perpendicular to the direction of the pipeline, at a selected distance above the pipeline;

(c) means to position said frame and flux detectors along said pipeline at said selected point with said detectors positioned symmetrically, one on each side of the vertical plane through the pipeline, whereby the vertical component of the earth'"'"'s magnetic field will be equal, and the same direction, while the magnetic flux due to an axial current in said pipeline will be in opposite directions in each of said two detectors;

(d) means for making a single point measurement by differentially connecting said first and second flux detectors so as to determine the flux through said detectors due to an axial current in said pipeline at said selected point; and

including;

(e) vertical third magnetic flux detector means, positioned with its axis midway between said first and second magnetic flux detectors;

(f) fourth magnetic flux detector positioned at a known selected distance horizontally from said third magnetic flux detector, said fourth magnetic flux detector pivoted for rotation about a horizontal axis in said vertical plane perpendicular to said pipeline;

(g) means to rotate said fourth magnetic flux detector means until a minimum flux passes through it; and

(h) means for determining the angle between the horizontal and the axis of said fourth detector;

whereby the vertical distance between said first and second magnetic flux detectors and the axis of said pipeline can be determined.

2. The apparatus as in claim 1 including means to position said frame in a vertical plane perpendicular to said pipeline and symmetrical about the vertical plane through said pipeline.

3. The apparatus as in claim 1 including means to determine the vertical distance between said frame and said pipeline.

4. The apparatus as in claim 1 wherein said flux detectors are identical and each has an elongated core of magnetic material and at least one coil wound around each of said cores.

5. The apparatus as in claim 4 in which there is a single coil per core of said flux detectors.

6. The apparatus as in claim 4 in which each of said flux detectors has a primary coil, a secondary coil and a magnetic flux biasing coil.

7. The apparatus as in claim 1 in which said frame is supported pendulously from a vehicle whereby said flux detectors are held with their axes vertical.

8. The apparatus as in claim 7 including damping means between said frame and said vehicle.

9. In an apparatus for detecting and determining the amplitude and direction of any electric current that may be flowing in a buried pipeline in the earth, at a selected point along said pipeline, comprising;

(a) first and second horizontally spaced apart vertical magnetic flux detectors on a vertical plane;

(b) a third vertical magnetic flux detector on said vertical plane with its axis midway between said first and second detectors;

the method of operation of said apparatus comprising;

(c) positioning said first, second and third flux detectors in said vertical plane along said pipeline at said selected point with said vertical plane perpendicular to the axis of said pipeline with said third detector vertically above said pipeline and said first and second detectors positioned symmetrically, one on each side of the vertical plane through the pipeline;

(d) laterally adjusting the positions of said three detectors until a minimum flux passes through said third detector;

whereby said third detector will be vertically above the axis of said pipeline;

(e) making a differential measurement of the flux passing through said first and second detector;

whereby a function of the magnitude of said current in said pipeline can be determined;

(f) a fourth magnetic flux detector on said vertical plane adapted for rotation about a horizontal axis perpendicular to said plane, and spaced horizontally a selected distance from said third detector;

and including the additional step of;

(g) rotating said fourth detector until a minimum flux passes through it; and

(h) determining the angle between the horizontal and the axis of said fourth detector;

whereby the magnitude of said current can be determined.