Detector for locating underground cables and faults therein using high-powered electromagnet

• US 5,210,498 A
• Filed: 10/24/1991
• Issued: 05/11/1993
• Est. Priority Date: 04/25/1989
• Status: Expired due to Fees

• Current Assignee: Tipteck Oy
• Original Assignee: Tipteck Oy
• Inventors: Paananen, Esa
• Primary Examiner(s): Harvey, Jack B.
• Assistant Examiner(s): BROWN, GLENN WARNER
• Application Number:
  US07/768,711
• Time in Patent Office: 565 Days
• Field of Search: 324/67, 324/327, 324/512, 324/520, 324/527, 324/528, 324/529, 324/530, 324/539, 455/57.1, 455/67.5, 455/67.7
• US Class Current: 324/529
• CPC Class Codes: G01R 31/083 in cables, e.g. underground

Abstract

A method and an apparatus for locating from above the ground or water the position of or cable fault in a cable buried underground or underwater. An alternating magnetic field generated by high-powered electromagnet or a rotating magnet induces an indicator signal current in the wires of a cable to be examined. At one or both ends of the cable, the indicator signal is monitored by means of a receiver connected to the cable wires. The received and amplified indicator signal is transmitted by a radio phone back to the point of transmission, whereat the indicator signal is listened to for detecting the location of a cable and its possibly faulty section. According to the invention, a sufficient direct voltage is supplied between the wires of the cable. This creates a current whose loop closes through a faulty location and the indicator signal is separated from the current produced by the direct voltage.

Claims

1. A method for locating from above the ground or water a cable fault in a pair of wires in a cable buried underground or underwater, said method comprising transmitting an indicator signal created by a magnetic field, said magnetic field being generated by a magnet located at an indicator signal transmission point which induces a current in the wires of a cable (3) to be examined, and monitoring the indicator signal by a receiver (4) connected to the cable, characterized in that between the wires of the cable (3) is supplied a direct voltage which induces a current which closes a loop through a faulty location (9), and that the indicator signal is monitored separately from the current produced by said direct voltage.

2. A method as set forth in claim 1, characterized in that the indicator signal monitored from the cable (3) by receiver (4) is amplified and transmitted back to the indicator signal transmission point to indicate whether or not an indicator signal is being monitored.

3. A method as set forth in claim 1 or 2, characterized in that the method is applied for locating an underground-buried cable from above the ground.

4. The method of claim 1, wherein the magnet comprises a high powered electromagnet or a rotating magnet.

5. An apparatus for locating from above the ground or water the position of or cable fault in a cable buried underground or underwater, said apparatus comprising means (1, 2) for generating an alternating magnetic field and a receiver (4) connectable to the wires of the cable (3) to be examined, said receiver being adapted to filter and amplify an indicator signal which is induced in cable wires by said alternating magnetic field at a signal transmission point, characterized in that said apparatus includes a direct-voltage source (10) for supplying a direct voltage between the wires of the cable (3) as well as a signal-separating means (M1;

R, C) for separately monitoring the indicator signal from a direct current produced by the voltage source (10).

6. An apparatus as set forth in claim 5, characterized in that said receiver (4) is provided with a transmission means and the indicator signal transmission point is provided with a receiving means, whereby an indicator signal passing along the examined cable (3) to receiver (4), or a signal derived therefrom, is an audio signal.

7. The apparatus of claim 6, wherein the transmission means comprises a radio transmitter and the receiving means comprises a radio receiver.

8. The apparatus of claim 6, wherein the transmission means and the receiving means each comprise a radiophone.