Shunt fault tester for multiconductor cable

• US 4,400,663 A
• Filed: 10/28/1981
• Issued: 08/23/1983
• Est. Priority Date: 10/28/1981
• Status: Expired due to Term

• Current Assignee: Bell Telephone Laboratories, Inc. (Nokia Corporation)
• Original Assignee: Bell Telephone Laboratories, Inc. (Nokia Corporation)
• Inventors: May, Paul H.
• Primary Examiner(s): Krawczewicz, Stanley T.
• Assistant Examiner(s): Solis, Jose M.
• Application Number:
  US06/315,665
• Time in Patent Office: 664 Days
• Field of Search: 324/51, 324/52, 179/175.3 R, 179/175.3 F
• US Class Current: 324/525
• CPC Class Codes: G01R 31/083 in cables, e.g. underground
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: G01R 31/58 Testing of lines, cables or conductors testing of electric windings G01R31/72

Abstract

Apparatus, and associated methodology, for locating a resistive shunt fault between wires of a cable utilizes the virtual interconnection property of operational amplifier means (112) to cause the coalescing of geographically separated nodes within the cable system. The various embodiments employ the amplifier means in conjunction with an ohmmeter (111) or current source (114)--voltmeter (113) combination and, when necessary, a good conductor (GOOD) which parallels the wires under test, to produce an estimate of the resistance (R₁) of one wire between the fault point and a measurement position.

Claims

1. Apparatus (FIG. 2) to test a wire pair (TIP, RING) from a multiconductor cable having a shield (SHIELD) for a resistive shunt fault (R_F) located between first (A) and second (B) test positions and for determining the resistance (R₁) of one wire (RING) between said fault and said first test position, said apparatus

CHARACTERIZED BY:

means at said first position comprising an ohmmeter (111) connected between said one wire (103) and said shield (105), and

means at said second position comprising operational amplifier means (112) having its noninverting (+) input connected to said shield (106), its inverting (-) input connected to said one wire (104), its output connected to the other wire (102) from said pair and its common (176) connected to said shield (106),

wherein the output of said ohmmeter is indicative of said resistance.

6. Apparatus as recited in claims 1, 3 or 5 wherein said ohmmeter operates at a single, low frequency and is frequency selective.

2. Apparatus (FIG. 6) to test a wire pair (TIP,RING) from a multiconductor cable having a shield (SHIELD) for a resistive shunt fault (R_F) located between first (A) and second (B) test positions and for determining the resistance (R₁) of one wire (RING) between said fault and said first test position, said apparatus

CHARACTERIZED BY:

means at said first position comprising

a voltmeter (113) connected between said one wire (103) and said shield (105), and

operational amplifier means (112) having its noninverting (+) input connected to said shield (105), its inverting (-) input connected to the mate of said one wire (101), its output connected to said one wire (103) and its common (176) connected to said shield (105), and

means at said second position comprising a current source (114) connected between said one wire (104) and said shield (106),

wherein the output of said voltmeter is indicative of said resistance.

7. Apparatus as recited in claims 2 or 4 wherein said current source operates at a single, low frequency and said voltmeter is frequency selective.

3. Apparatus (FIG. 3) to test a wire pair (TIP, RING) from a multiconductor cable having a shield (SHIELD) and at least one other conductor (GOOD) paralleling said pair for a resistive shunt fault (R_F) located between first (A) and second (B) test positions and for determining the resistance (R₁) of one wire (RING) between said fault and said first test position, said apparatus

CHARACTERIZED BY:

means at said first position comprising an ohmmeter (111) connected between said one wire (103) and the said shield (105) and means (177) for shorting said other conductor (109) to said shield (105), and

means at said second position comprising operational amplifier means (112) having its noninverting (+) input connected to said conductor (110), its inverting (-) input connected to said one wire (104), its output connected to the other wire (102) from said pair, and its common (176) connected to said shield (106),

wherein the output of said ohmmeter is indicative of said resistance.

4. Apparatus (FIG. 4) to test a wire pair (TIP, RING) from a multiconductor cable having a shield (SHIELD) and at least one other conductor (GOOD) paralleling said pair for a resistive shunt fault (R_F) located between first (A) and second (B) test positions and for determining the resistance (R₁) of one wire (RING) between said fault and said first test position, said apparatus

CHARACTERIZED BY:

means at said first position comprising;

a voltmeter (113) connected between said one wire (103) and said other conductor (109), and

a current source (114) connected between said one wire (103) and said shield (105), and

means at said second position comprising

means (177) for shorting said other conductor (110) to said shield (106), and

operational amplifier means (112) having its noninverting (+) input connected to said conductor (110), its inverting (-) input connected to said one wire (104), its output connected to the other wire (102) from said pair, and its common (176) connected to said shield (106),

wherein the output of said voltmeter is indicative of said resistance.

5. Apparatus (FIG. 5) to test a wire pair (TIP, RING) from a multiconductor cable having a shield (SHIELD) and at least one other conductor (GOOD) paralleling said pair for a resistive shunt fault (R_F) located between first (A) and second (B) test positions and for determining the resistance (R₁) of one wire (RING) between said fault and said first test position, said apparatus

CHARACTERIZED BY:

means at said first position comprising;

operational amplifier means (112) having its noninverting (+) input connected to its common (176), its inverting (-) input connected to said other conductor (109), and its output connected to the other wire (101) of said pair, and

an ohmmeter (111) connected between said one wire (103) and said common, and

means at said second position for shorting said one wire (104) to said conductor (110),

wherein the reading of said ohmmeter is indicative of said resistance.

8. Apparatus (FIG. 6) to estimate the location of a shunt fault (R_F) along a pair of conductors (TIP, RING) spanning two test positions (A and B), each of said conductors having a terminal node (101,102 and 103,104) accessible at each of said test positions and a corresponding fault node (107 and 108) associated with said fault, said test positions being interconnected with an electrical path (SHIELD) having an end node (105 and 106) accessible at each of said test positions, said apparatus

CHARACTERIZED BY:

first means (114), located at the first of said test positions (B) and connected to one said terminal node (104) and said end node (106), for supplying constant current between said one said terminal node (104) and said end node (106),

second means (112), located at the second of said test positions (A) and connected to each said terminal node (101 and

     103) and said end node (105), for virtually interconnecting each said fault node (107 and

     108) with one said terminal node (101) and said end node (105), and for providing a current path between the other said terminal node (103) and said end node (105), and

third means (113), located at said second of said test positions, for measuring the voltage generated between said end node (105) and said other said node (103) due to said constant current,

wherein said voltage is indicative of the resistance of one of said conductors between said second of said test positions and said fault.

9. Apparatus (FIG. 2) to estimate the location of a shunt fault (R_F) along a pair of conductors (TIP,RING), spanning two test positions (A and B), each of said conductors having a terminal node (101,102 and 103,104) accessible at each of said test positions and a corresponding fault node (107 and 108) associated with said fault, said test positions being interconnected with an electrical path (SHIELD) having an end node (105 and 106) accessible at each of said test positions, said apparatus

CHARACTERIZED BY:

first means (111), located at the first of said test positions (A) and connected to one said terminal node (103) and said end node (105), for measuring the resistance between said one said terminal node (103) and said end node (105), and

second means (112), located at the other of said test positions (B) and connected to each said terminal node (102 and

     104) and said end node (106), for virtually interconnecting one said fault node (108) with one said terminal node (104) and said end node (106) and for providing an electrical path between the other said terminal node (102) and said end node (106),

wherein said resistance comprises the resistance of one of said conductors between said first of said test positions and said fault.