System for and Method of Detecting a Buried Conductor

• US 20100001713A1
• Filed: 03/02/2009
• Published: 01/07/2010
• Est. Priority Date: 02/29/2008
• Status: Active Grant

• Current Assignee: Radiodetection Limited
• Original Assignee: Radiodetection Limited
• Inventors: Royle, John Mark
• Granted Patent: US 7,969,137 B2
• Time in Patent Office: Days
• US Class Current: 324/67
• CPC Class Codes: G01V 3/081 the magnetic field is produced by the objects or geological structures characterised by the method of magnetic field measurement G01R33/00

Abstract

A system for detecting a buried conductor comprises a transmitter for producing an alternating test current in the buried conductor and a receiver for detecting an electromagnetic field produced by the test current in the buried conductor. A communication link is provided between the receiver and the transmitter. The test current comprises first and second components of different frequency. The receiver monitors the phase creepage of the first and second components and controls the transmitter to reset the phase difference between the first and second components as phase creepage increases.

Claims

1. A system for detecting a buried conductor, the system comprising:

means for producing an alternating test current in said buried conductor, the test current comprising a first component and a second component having a frequency different to a frequency of the first component;

means for detecting an electromagnetic field produced by the test current in said buried conductor and for measuring a phase difference between the first component and the second component; and

means for providing a communication link between the means for detecting an electromagnetic field and the means for producing an alternating test current;

wherein the means for producing an alternating test current and means for detecting an electromagnetic field are configured for the means for detecting an electromagnetic field to alter, via the communication link, the phase difference between the first component and the second component.

2. A system as claimed in claim 1, wherein the means for producing an alternating test current and the means for detecting an electromagnetic field are configured for the means for detecting an electromagnetic field to alter the phase difference between the first component and the second component by:

the means for detecting an electromagnetic field being configured to compare the phase difference at the means for detecting an electromagnetic field between the first component and the second component to a reference phase difference and to calculate a phase creepage;

the means for detecting an electromagnetic field being configured to transmit a command to the means for producing an alternating test current to alter the phase difference between the first component and second component when the phase creepage is above a lower threshold and below an upper threshold; and

the means for producing an alternating test current being configured to receive the command transmitted from the means for detecting an electromagnetic field and to alter the phase difference between the first component and the second component.

3. A system as claimed in claim 2, wherein the means for detecting an electromagnetic field comprises a user interface and the means for detecting an electromagnetic field is configured to convey a warning when the phase creepage is above the upper threshold.

4. A system as claimed in claim 3, wherein the warning comprises a warning that the phase of one of the first component and the second component is reversed.

5. A system as claimed in claim 3, wherein the warning comprises a warning that the electromagnetic field detected by the means for detecting an electromagnetic field is not produced by the test current in said buried conductor.

6. A system as claimed in claim 2, wherein the lower threshold is 2 degrees.

7. A system as claimed in claim 2, wherein the upper threshold is 88 degrees.

8. A system as claimed in claim 2, wherein the reference phase difference is measured at a location along said buried conductor.

9. A system as claimed in claim 1, wherein the communication link between the means for detecting an electromagnetic field and means for producing an alternating test current is provided by a transceiver at each of the means for producing an alternating test current and means for detecting an electromagnetic field.

10. A system as claimed in claim 1, wherein the communication link between the means for detecting an electromagnetic field and the means for producing an alternating test current is a duplex or half-duplex communication link.

11. A system as claimed in claim 1, wherein the communication link between the means for producing an alternating test current and the means for detecting an electromagnetic field is a wireless communication link.

12. A system as claimed in claim 1, wherein the means for detecting an electromagnetic field is configured to alter the phase difference between the first component and the second component without intervention from an operator of the system.

13. A system as claimed in claim 1, wherein the test current in said buried conductor is produced by the means for producing an alternating test current by means of an output module, the output module either radiating an electromagnetic field to induce the test current in said buried conductor, being directly connected to a part of said buried conductor or clamping the output module around said buried conductor.

14. A system as claimed in claim 1, further comprising:

analogue to digital converters to convert the field strength signals into digital signals; and

a digital signal processor arranged to process the digital signals and to isolate signals of predetermined frequency bands,

wherein the means for detecting an electromagnetic field includes a plurality of antennas for detecting the electromagnetic field produced by the test current in said buried conductor, and

wherein each antenna outputs a field strength signal representative of the electromagnetic field at the antenna.

15. A method of detecting a buried conductor, the method comprising:

providing a transmitter for producing an alternating test current in said buried conductor, the test current comprising a first component and a second component having a frequency different to a frequency of the first component;

providing a receiver for detecting an electromagnetic field produced by the test current in said buried conductor and for measuring a phase difference at the receiver between the first component and the second component;

providing a communication link between the receiver and the transmitter; and

the receiver altering, via the communication link between the receiver and the transmitter, the phase difference between the first component and the second component.

16. A method as claimed in claim 15, wherein the receiver alters the phase difference between the first component and the second component by:

comparing the phase difference at the receiver between the first component and the second component to a reference phase difference to calculate a phase creepage;

comparing the phase creepage to a lower threshold and an upper threshold;

transmitting a command from the receiver to the transmitter to alter the phase difference between the first component and second component when the phase creepage is above the lower threshold and below the upper threshold; and

altering the phase difference at the transmitter between the first component and the second component.

17. A method as claimed in claim 16, wherein the lower threshold is 5 degrees.

18. A method as claimed in claim 16, wherein the upper threshold is 60 degrees.

19. A method as claimed in claim 15, wherein the communication link between the receiver and transmitter is a duplex or half-duplex communication link and the communication link between the transmitter and receiver is a wireless communication link.

20. A method as claimed in claim 15, wherein the receiver is configured to alter the phase difference between the first component and the second component without intervention from an operator of the system.

21. A method as claimed in claim 15, wherein the test current in said buried conductor is produced by the transmitter by means of an output module, the output module either radiating an electromagnetic field to induce the test current in said buried conductor, being directly connected to a part of said buried conductor or clamping the output module around said buried conductor.

22. A method as claimed in claim 15, further comprising:

analogue to digital converters to convert the field strength signals into digital signals; and

a digital signal processor arranged to process the digital signals and to isolate signals of predetermined frequency bands.

wherein the receiver includes a plurality of antennas for detecting the electromagnetic field produced by the test current in said buried conductor, and

wherein each antenna outputs a field strength signal representative of the electromagnetic field at the antenna.

23. A system for detecting a buried conductor, the system comprising:

a transmitter for producing an alternating test current in said buried conductor, the test current comprising a first component and a second component having a frequency different to a frequency of the first component;

a receiver for detecting an electromagnetic field produced by the test current in said buried conductor and for measuring a phase difference at the receiver between the first component and the second component; and

means for providing a communication link between the receiver and the transmitter;

wherein the transmitter and receiver are configured for the receiver to alter, via the communication link between the receiver and the transmitter, the phase difference between the first component and the second component.