Cable fault detector

• US 6,741,081 B1
• Filed: 03/04/2003
• Issued: 05/25/2004
• Est. Priority Date: 03/04/2003
• Status: Expired due to Fees

• Current Assignee: AT&T Corporation (AT&T, Inc.)
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Huffman, John Sinclair, Eslambolchi, Hossein
• Primary Examiner(s): Pert, Evan
• Assistant Examiner(s): Nguyen, Jimmy
• Application Number:
  US10/379,020
• Time in Patent Office: 448 Days
• Field of Search: 324/541, 324/544, 324/530, 324/509, 324/510, 324/512, 324/539, 324/543, 324/513, 324/127, 324/126
• US Class Current: 324/541
• CPC Class Codes: G01R 31/083 in cables, e.g. underground
• CPC Class Codes: H04B 10/07 Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
• CPC Class Codes: H04B 10/0791 Fault location on the transmission path

Abstract

The present invention is a apparatus and method for accurately finding a location of a fault in a fiber cable where a cable locating current is leaking to ground. The system includes a sensor body, voltage probes mounted in the body to face the cable, a reference voltage input and a voltage comparator that compares the reference voltage to a measured voltage at the probes. Use of the system may include applying a conductive medium such as a conductive gel between the probes and the cable.

Claims

1. An apparatus for locating on an optical fiber cable a fault where a cable locating current is leaking to ground, the apparatus comprising:

a body adapted to be positioned adjacent the cable;

at least one voltage probe mounted in the body and positioned in the body to probe the leaking cable locating current;

a reference voltage input for receiving a reference voltage; and

a voltage comparator electrically connected to the at least one voltage probe and to the reference voltage input, the comparator configured for measuring a test voltage between the reference voltage and the at least one voltage probe.

2. The apparatus of claim 1, wherein the body is further adapted to at least partially surround a transverse section of the cable.

3. The apparatus of claim 2, wherein the at least one voltage probe comprises a plurality of voltage probes angularly spaced around the transverse section of the cable.

4. The apparatus of claim 1, wherein the at least one voltage probe presents a conductive surface facing the cable.

5. The apparatus of claim 1, wherein the reference voltage is ground.

6. The apparatus of claim 1, wherein the reference voltage is a DC voltage applied to the cable.

7. A method for locating on a cable a fault where a cable locating current is leaking to ground, the method comprising the steps of:

positioning a voltage probe adjacent the cable;

applying a conductive medium between the cable and the voltage probe;

displacing the voltage probe along the cable;

measuring a voltage between the voltage probe and a reference voltage; and

based on the voltage, detecting the fault at a position of the voltage probe along the cable.

8. The method of claim 7, wherein the conductive medium is water.

9. The method of claim 7, wherein the conductive medium is a water-based paste.

10. The method of claim 7, wherein the conductive medium is a gel.

11. The method of claim 7, wherein the voltage probe comprises a plurality of conductive surfaces facing the cable.

12. The method of claim 11, wherein the step of positioning a voltage probe adjacent the cable includes at least partially surrounding the cable with the voltage probe.

13. The method of claim 12, wherein the step of displacing the voltage probe along the cable comprises maintaining the probe in a position at least partially surrounding the cable.

14. The method of claim 7, wherein the step of measuring a voltage between the voltage probe and a reference voltage includes measuring a voltage between the voltage probe and ground.

15. The method of claim 7, further comprising the step of applying a reference DC voltage to the cable, and wherein the step of measuring a voltage between the voltage probe and a reference voltage includes measuring a voltage between the voltage probe and the reference DC voltage.

16. The method of claim 7, further comprising the step of sounding an alarm when the fault is detected.

17. The method of claim 7, further comprising the step of initially determining an approximate position of the fault by determining a position along the cable where an above-ground detectability of the cable locating current degrades.

18. The method of claim 7, wherein the step of detecting the fault comprises detecting a drop in the measured voltage.

19. The method of claim 7, wherein the step of detecting the fault comprises detecting an increase in the measured voltage.