Apparatus and method for determining the status of an electric power cable

• US 20040160227A1
• Filed: 02/11/2004
• Published: 08/19/2004
• Est. Priority Date: 02/18/2003
• Status: Abandoned Application

• Current Assignee: Gregory H. Piesinger
• Original Assignee: Gregory H. Piesinger
• Inventors: Piesinger, Gregory H.
• Application Number:
  US10/778,288
• Publication Number:
  US 20040160227A1
• Time in Patent Office: Days
• US Class Current: 324/539
• CPC Class Codes: G01R 19/145 Indicating the presence of current or voltage
• CPC Class Codes: G01R 31/086 in power transmission or distribution networks, i.e. with interconnected conductors
• 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

An apparatus (100) and method (300) for determining the status of a electric cable (20) is provided. The apparatus (100) rigidly includes a probe (104) having coaxial contacts (150, 152) and including a melt unit (102) configured to melt an insulating jacket (32) of the cable (20), an instrumentation unit (106) coupled to the probe (104) and housing a cable analysis circuit (186), a status display unit (188) coupled to the instrumentation unit (106), an insulated shank (108) coupled to the instrumentation unit (106), and a hotstick adapter (110) coupled to the insulated shank (108). The cable analysis circuit (186) includes a connection determination circuit (200) configured to determine if an electrical connection between the probe (104) and the cable (20) is a valid connection, and a status determination circuit (222) configured to determine the status of the cable (20) while the electrical connection is a valid connection. The status display unit (188) includes a plurality of visual indicators (236) configured to impart connection condition and cable status to the user.

Claims

1. An apparatus for determining the status of an underground residential distribution (URD) cable in an electric power network operating at a line frequency, said apparatus comprising:

a rigid probe comprising;

a common contact configured to contact a neutral conductor of said URD cable; and

an input contact insulated from said common contact and configured to contact an outer semiconductor sheath of said URD cable;

an instrumentation unit rigidly coupled to said probe;

a cable analysis circuit housed within said instrumentation unit and electrically coupled to said common and input contacts; and

a status display unit electrically coupled to said cable analysis circuit.

2. An apparatus as claimed in claim 1 wherein said input contact is substantially coaxial with said common contact.

3. An apparatus as claimed in claim 1 wherein said cable analysis circuit comprises:

a connection determination circuit configured to determine if an electrical connection between said probe and said URD cable is a valid connection; and

a status determination circuit configured to determine said status of said URD cable while said connection determination circuit simultaneously determines if said electrical connection is said valid connection.

4. An apparatus as claimed in claim 1 wherein said probe additionally comprises a melt unit configured to melt an insulating jacket of said URD cable when said URD cable is a jacketed URD cable.

5. An apparatus as claimed in claim 1 wherein:

said rigid probe has an active end and an instrumentation end in opposition to said active end, wherein said input contact and common contacts are proximate said active end;

said instrumentation unit has a probe side and a display side in opposition to said probe side, wherein said probe side is coupled to said probe proximate said instrumentation end; and

said status display unit is coupled to said display side.

6. An apparatus as claimed in claim 1 wherein said status display unit comprises:

a first indicator configured to indicate a condition of an electrical connection between said probe and said URD cable; and

a second indicator configured to indicate said status of said URD cable.

7. An apparatus as claimed in claim 1 wherein said common and input contacts are separated by a inter-contact distance of less than or equal to 3 cm.

8. An apparatus as claimed in claim 1 wherein said probe has a probe body having a probe body length of less than or equal to 32 cm.

9. An apparatus as claimed in claim 1 wherein said cable analysis circuit comprises a power supply comprising:

a battery;

a contact detector coupled to said probe and configured to detect when said probe has effected an electrical connection with said URD cable; and

a gated regulator coupled to said battery and said contact detector and configured to automatically provide power to a remaining portion of said cable analysis circuit in response to said contact detector.

10. An apparatus as claimed in claim 1 wherein said cable analysis circuit comprises:

a connection determination circuit configured to determine if an electrical connection between said probe and said URD cable is a valid connection; and

a status determination circuit configured to determine said status of said URD cable.

11. An apparatus as claimed in claim 10 wherein said connection determination circuit determines if a resistance between said input contact and said common contact is greater than a lower resistance threshold and less than a higher resistance threshold.

12. An apparatus as claimed in claim 11 wherein:

said lower resistance threshold is greater than 75 Ω

; and

said higher resistance threshold is less than 50 kΩ

.

13. An apparatus as claimed in claim 10 wherein said status determination circuit determines if a line signal derived from said URD cable has a line-signal amplitude of either less than a lower signal threshold or greater than a higher signal threshold.

14. An apparatus as claimed in claim 13 wherein said status display unit comprises:

a first indicator configured to indicate when said status determination circuit determines said line-signal amplitude is less than said lower signal threshold; and

a second indicator configured to indicate when said status determination circuit determines said line-signal amplitude is greater than said higher signal threshold.

15. An apparatus as claimed in claim 1 additionally comprising:

an insulated shank coupled to one of said probe and said instrumentation unit; and

a hotstick adapter coupled to said insulated shank.

16. An apparatus for determining the status of an underground residential distribution (URD) cable in an electric power network, said apparatus comprising:

a probe configured to establish an electrical connection with said URD cable, wherein said electrical connection comprises;

a common contact of said probe in contact with a neutral conductor of said URD cable; and

an input contact of said probe in contact with an outer semiconductor sheath of said URD cable;

a cable analysis circuit coupled to said probe, configured to simultaneously determine if said electrical connection is a valid connection and said status of said URD cable when said electrical connection is said valid connection; and

a status display unit coupled to said cable analysis circuit and configured to indicate said status of said URD cable when said electrical connection is said valid connection.

17. An apparatus as claimed in claim 16 wherein said probe is a rigid coaxial probe comprising:

a conductive shell of which said common contact is a portion; and

an input conductor within said conductive shell and of which said input contact is a portion.

18. An apparatus as claimed in claim 16 wherein said probe is a rigid probe comprising:

a probe body having an active end and an instrumentation end in opposition to said active end; and

a melt unit coupled to said active end and configured to melt an insulating jacket of said URD cable when said URD cable is a jacketed URD cable.

19. An apparatus as claimed in claim 16 wherein said status display unit comprises:

a first indicator configured to indicate when said electrical connection is said valid connection; and

a second indicator configured to indicate said status of said URD cable.

20. An apparatus as claimed in claim 16 wherein said cable analysis circuit comprises:

a connection determination circuit configured to determine when said electrical connection is said valid connection; and

a status determination circuit configured to determine said status of said URD cable when said electrical connection is said valid connection.

21. An apparatus as claimed in claim 20 wherein said connection determination circuit determines if a resistance between said input contact and said common contact is one of less than a lower resistance threshold and greater than a higher resistance threshold.

22. An apparatus as claimed in claim 21 wherein:

said lower resistance threshold is greater than 75 Ω

; and

said higher resistance threshold is less than 50 kΩ

.

23. An apparatus as claimed in claim 20 wherein said connection determination circuit comprises:

a signal injector coupled to said input contact, configured to generate a trace signal, and configured to inject said trace signal into said input contact such that a trace-signal amplitude of said trace signal is a proportionate to said resistance;

a lower-threshold detector coupled to said input contact and configured to detect when said trace-signal amplitude is less than a lower trace threshold; and

a higher-threshold detector coupled to said input contact and configured to detect when said trace-signal amplitude is greater than a higher trace threshold.

24. An apparatus as claimed in claim 23 wherein:

said line signal has a line frequency; and

said trace signal has a trace frequency different from said line frequency.

25. An apparatus as claimed in claim 20 wherein said status determination circuit determines if a line signal derived from said URD cable has a line-signal amplitude of either less than a lower signal threshold or greater than a higher signal threshold.

26. An apparatus as claimed in claim 25 wherein said status display unit comprises:

a first indicator coupled to said status determination circuit and configured to indicate when said line-signal amplitude is less than said lower signal threshold; and

a second indicator coupled to said status determination circuit and configured to indicate when said line-signal amplitude is greater than said higher signal threshold.

27. An apparatus as claimed in claim 26 wherein said status display unit comprises a third indicator coupled to said status determination circuit and configured to indicate when said line-signal amplitude is greater than said lower signal threshold and less than said higher signal threshold.

28. An apparatus as claimed in claim 26 wherein said status determination circuit is configured to inhibit indication by said first and second indicators when said line-signal amplitude is greater than said lower signal threshold and less than said higher signal threshold.

29. An apparatus for determining the status of a jacketed underground residential distribution (URD) cable in an electric power network, said apparatus comprising:

a probe comprising a melt unit configured to melt through an insulating jacket of said jacketed URD cable, said melt unit comprising;

a common contact configured to contact a neutral conductor of said jacketed URD cable when said melt unit has melted through said insulating jacket; and

an input contact insulated from said common contact and configured to contact an outer semiconductor sheath of said jacketed URD cable when said melt unit has melted through said insulating jacket;

an instrumentation unit coupled to said probe; and

a status display unit coupled to said instrumentation unit.

30. An apparatus as claimed in claim 29 wherein:

said probe is a rigid probe having an active end and an instrumentation end in opposition to said active end;

said instrumentation unit has a probe side and a display side in opposition to said probe side, wherein said probe side is coupled to said probe proximate said instrumentation end; and

said status display unit is coupled to said display side.

31. An apparatus as claimed in claim 29 wherein said melt unit comprises:

a substantially cylindrical outer shell of which said common contact is a portion; and

a substantially coaxial input conductor within said outer shell and of which said input contact is a portion.

32. An apparatus as claimed in claim 29 wherein:

said common contact is a first melt-unit common contact;

said input contact is a first melt-unit input contact;

said probe additionally comprises a probe body comprising;

a second probe-body common contact configured to be electrically coupled to said first common contact; and

a second probe-body input contact insulated from said second common contact and configured to be electrically coupled to said first input contact; and

said melt unit is detachably coupled to said probe body.

33. An apparatus as claimed in claim 32 wherein said first input contact is sharper than said second input contact.

34. An apparatus as claimed in claim 29 wherein said melt unit is configured to be heated by an application of heat from an external heat source.

35. An apparatus as claimed in claim 29 wherein:

said probe additionally comprises a probe body coupled to said melt unit; and

said melt unit comprises;

a thermal reservoir; and

a thermal insulator coupled between said thermal reservoir and said probe body.

36. An apparatus as claimed in claim 35 wherein said thermal reservoir comprises a thermometer connector configured to accept a thermometer.

37. An apparatus as claimed in claim 35 wherein said thermal reservoir is configured to retain sufficient heat to melt through said insulating jacket a plurality of times.

38. An apparatus as claimed in claim 35 wherein:

said common contact is a first common contact;

said input contact is a first input contact; and

said probe body comprises;

a second common contact configured to be electrically coupled to said first common contact through said thermal reservoir; and

a second input contact insulated from said second common contact and configured to be electrically coupled to said first input contact through said thermal reservoir.

39. An apparatus as claimed in claim 35 wherein said thermal reservoir comprises:

a thermally massive outer shell, wherein said common contact is a portion of said outer shell;

a thermally conductive electrical insulator within said outer shell; and

a thermally conductive input conductor within said thermally conductive electrical insulator, wherein said input contact is a portion of said input conductor.

40. An apparatus as claimed in claim 35 wherein:

said common contact is thermally coupled to said thermal reservoir and is configured to melt through said insulating jacket to effect contact with said neutral conductor; and

said input contact is thermally coupled to said thermal reservoir and is configured to melt through said insulating jacket to effect contact with said outer semiconductor sheath.

41. An apparatus as claimed in claim 29 wherein:

said input contact extends a first predetermined distance beyond said common contact; and

said input contact is detachably coupled to said melt unit so that said input contact can be replaced by another input contact that projects a second predetermined distance beyond said common contact.

42. An apparatus for determining the status of an underground residential distribution (URD) cable in an electric power network, said apparatus comprising:

a rigid probe having an active end and an instrumentation end in opposition to said active end, wherein said active end is configured to effect an electrical connection with said URD cable;

an instrumentation unit having a probe side and a display side in opposition to said probe side, wherein said probe side is rigidly coupled to said probe proximate said instrumentation end;

a status display unit coupled to said instrumentation unit upon said display side.

43. An apparatus as claimed in claim 42 wherein:

said apparatus additionally comprises a power supply configured to automatically provide power to said apparatus when said probe effects said electrical connection; and

said status display unit comprises an indicator configured to indicate when said power supply is providing said power.

44. An apparatus as claimed in claim 42 wherein said status display unit comprises a plurality of visual indicators.

45. An apparatus as claimed in claim 44 wherein said visual indicators are light-emitting diodes.

46. An apparatus as claimed in claim 42 wherein said status display unit comprises an indicator configured to indicate when a resistance across said probe is greater than a lower resistance threshold and less than a higher resistance threshold.

47. An apparatus as claimed in claim 42 wherein said status display unit comprises:

a first indicator configured to indicate when a resistance across said probe and through said URD cable is less than a lower resistance threshold; and

a second indicator configured to indicate when said resistance is greater than a higher resistance threshold.

48. An apparatus as claimed in claim 47 wherein said status display unit comprises a third indicator configured to indicate when said apparatus is energized.

49. An apparatus as claimed in claim 42 wherein said status display unit comprises a first indicator configured to indicate when a line-signal amplitude of a line signal derived from said URD cable is less than a lower signal threshold.

50. An apparatus as claimed in claim 49 wherein said status display unit additionally comprises a second indicator configured to indicate when said line-signal amplitude is greater than a higher signal threshold.

51. An apparatus as claimed in claim 50 wherein:

said first indicator is of a first color; and

said second indicator is of a second color different from said first color.

52. An apparatus as claimed in claim 50 wherein said status display unit additionally comprises a third indicator configured to indicate when said line-signal amplitude is greater than said lower signal threshold and less than said higher signal threshold.

53. An apparatus as claimed in claim 42 wherein said status display unit comprises an indicator configured to indicate when a line-signal amplitude of a line signal derived from said URD cable is less than a lower signal threshold while simultaneously verifying a resistance across said probe and through said URD cable is greater than a lower resistance threshold and less than a higher resistance threshold.

54. A method for determining the status of an underground residential distribution (URD) cable in an electric power network, said method comprising:

connecting a probe to said URD cable so as to establish an electrical connection;

verifying that said electrical connection established in said connecting activity is a valid connection; and

establishing said status of said URD cable when said verifying activity simultaneously verifies said electrical connection is a valid connection.

55. A method as claimed in claim 54 wherein said connecting activity comprises:

contacting one of an outer semiconductor sheath and a neutral conductor of said URD cable with an input contact of said probe; and

contacting said neutral conductor of said URD cable with a common contact of said probe.

56. A method as claimed in claim 54 wherein said verifying activity comprises determining said electrical connection is said valid connection when a resistance between said input contact and said common contact is greater than a lower resistance threshold and less than a higher resistance threshold.

57. A method as claimed in claim 56 additionally comprising repeating said connecting and verifying activities at a different contact location on said URD cable when said verifying activity fails to verify said electrical connection is a valid connection.

58. A method as claimed in claim 54 additionally comprising indicating when a resistance between said input contact and said common contact is greater than a lower resistance threshold and less than a higher resistance threshold.

59. A method as claimed in claim 54 additionally comprising indicating when a resistance between said input contact and said common contact is one of less than a lower resistance threshold and greater than a higher resistance threshold.

60. A method as claimed in claim 54 wherein said establishing activity comprises determining said status is a de-energized status when a line signal derived from said URD cable has a line-signal amplitude less than a lower signal threshold.

61. A method as claimed in claim 60 wherein said establishing activity additionally comprises determining said status is an energized status when said line-signal amplitude is greater than a higher signal threshold.

62. A method as claimed in claim 54 wherein said establishing activity comprises determining said status is an indeterminate status when a line signal derived from said URD cable has a line-signal amplitude greater than a lower signal threshold and less than a higher signal threshold.

63. A method as claimed in claim 62 additionally comprising repeating said connecting, verifying, and establishing activities at a different location on said URD cable when said establishing activity establishes said status is said indeterminate status.

64. A method as claimed in claim 54 additionally comprising:

executing said connecting, verifying, and establishing activities a plurality of times wherein, for each of said executing activities, said connecting activity is executed at a different contact location on said URD cable; and

adjudicating said status of said URD cable in response to a plurality of said establishing activities.

65. A method as claimed in claim 54 wherein said URD cable is a jacketed URD cable, and wherein said method additionally comprises:

heating a melt unit of said probe; and

melting an insulating jacket of said jacketed URD cable with said melt unit to effect said connecting activity.

66. A method as claimed in claim 65 additionally comprising attaching said melt unit to a body of said probe prior to said heating activity when said melt unit is configured to be detachably coupled to said body.

67. A method as claimed in claim 54 wherein:

said URD cable is an unjacketed cable that comprises a plurality of neutral conductors surrounding a semiconductor sheath; and

said method additionally comprises, when said establishing activity fails to establish a “

dead”

status for said URD cable, clamping said neutral conductors to said semiconductor sheath proximate a position where said probe is connected to said URD cable.

68. A method as claimed in claim 67 wherein said clamping activity clamps first and second clamps on opposing sides of said position.

69. A method for determining the status of a jacketed underground residential distribution (URD) cable in an electric power network, said method comprising:

heating a melt unit of a probe with heat from an external heat source;

melting an insulating jacket of said URD cable with said melt unit;

connecting said probe to said URD cable so as to establish an electrical connection through said melting activity;

verifying that said electrical connection established in said connecting activity is a valid connection; and

establishing said status of said URD cable when said verifying activity verifies that said electrical connection is a valid connection.

70. A method as claimed in claim 69 additionally comprising attaching said melt unit to a body of said probe prior to said heating activity when said melt unit is configured to be detachably coupled to said body.

71. A method as claimed in claim 69 additionally comprising configuring said melt unit to have a substantially cylindrical and conductive thermal reservoir, to have a thermally conductive insulator within said thermal reservoir, and to have an inner conductor within said thermally conductive insulator.

72. A method as claimed in claim 71 wherein said conductive thermal reservoir, said thermally conductive insulator, and said inner conductor are mutually coaxial.

73. A method as claimed in claim 69 wherein said establishing activity establishes said status while said verifying activity simultaneously verifies said electrical connection.