System for rating electric power transmission lines and equipment

• US 4,806,855 A
• Filed: 06/12/1987
• Issued: 02/21/1989
• Est. Priority Date: 06/22/1984
• Status: Expired due to Term

• Current Assignee: Murray W. Davis
• Original Assignee: Murray W. Davis
• Inventors: Davis, Murray W.
• Primary Examiner(s): Karlsen, Ernest F.
• Application Number:
  US07/061,342
• Time in Patent Office: 620 Days
• Field of Search: 324/127, 340/870.17, 340/538, 340/657, 364/483, 364/492
• US Class Current: 324/127
• CPC Class Codes: G01R 1/22 Tong testers acting as secondary windings of current transformers
• CPC Class Codes: G01R 15/14 Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
• CPC Class Codes: G01R 19/15 Indicating the presence of current
• CPC Class Codes: H02J 13/00002 characterised by monitoring
• CPC Class Codes: H02J 13/00009 using pulsed signals
• CPC Class Codes: H02J 13/00022 using wireless data transmission
• CPC Class Codes: H02J 13/00034 the elements or equipment being or involving an electric power substation
• CPC Class Codes: H02J 2213/10 using simultaneously two or more different transmission means
• CPC Class Codes: Y02E 60/00 Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
• CPC Class Codes: Y04S 10/00 Systems supporting electrical power generation, transmission or distribution
• CPC Class Codes: Y04S 10/30 State monitoring, e.g. fault, temperature monitoring, insulator monitoring, corona discharge
• CPC Class Codes: Y04S 40/121 using the power network as support for the transmission
• CPC Class Codes: Y04S 40/126 using wireless data transmission

Abstract

A system for determining the current carrying capability of one or more overhead power transmission lines monitors one or more spans of each line on real-time basis and identifies the span having the lowest current carrying capacity which in turn establishes the maximum capacity of the entire line. The thermal state of each monitored line span is determined by measuring the conductor temperature, line current, solar radiation, ambient temperature, and in some cases wind speed and wind direction. These parameters are monitored by a sensor-transmitter unit that may be removably clamped on the line conductor which may range in size from one to several inches in diameter, and includes a radio transmitter for transmitting sensed data to a receiving substation. The data from the sensor-transmitter is multiplexed and transmitted by a telecommunications link to a computer which automatically determines line capacity using the real-time data and also calculates the time required for the "critical span" having the lowest current capacity to reach its maximum safe temperature based on any of a number of step changes in load demands. Each sensor-transmitter may include sensors for monitoring the current level, conductor temperature, solar radiation impinging on the conductor, ambient temperature, wind direction and velocity and conductor sag. These sensors and the transmitter are enclosed in a corona-free housing and are powered by a power supply that includes a transformer core which surrounds and is inductively coupled with the monitored conductor. The core is formed in an upper and lower portion which are shiftable relative to each other upon opening and closing a pair of conductor clamping jaws in order to permit the conductor to be introduced into and withdrawn from the core and to allow the clamping jaws to fit a range of conductor diameters while maintaining constant air gaps between the upper and lower core portions.

Claims

1. A sensing device adapted to be clamped to an electrically energized overhead electric power line, said sensing device comprising:

a housing;

first and second jaws carried by said housing, said jaws being shiftable relative to each other from a closed position clamping said overhead electric power line therebetween and an open position releasing said overhead electric power line from said jaws;

sensing means associated with said housing for directly sensing at said device at least one of the following parameters;

current in said overhead electric power line, temperature of said power line, ambient temperature, and solar radiation impinging on said power line;

power supply means carried by said housing for supplying electrical power to said sensing means, said power supply means including an electrical transformer for supplying electrical power to said sensing means, said transformer including a magnetic core for magnetically coupling said overhead electric power line with said transformer when said jaws are in said closed position;

second means for sensing the other parameters from said parameters and means for determining from said at least one directly sensed parameter and said other sensed parameters a final parameter defining the maximum current carrying capacity of said power line.

2. The sensing device of claim 1, wherein said sensing means includes means for transmitting at least one of said parameters to a remote location.

3. The sensing device of claim 1, wherein said core is formed of a magnetic material and includes first and second core portions shiftable relative to each other.

4. The sensing device of claim 3, wherein said first jaw is shiftable relative to said housing, and said first core portion is connected to said first jaw, said first jaw being shiftable relative to said housing.

5. The sensing device of claim 3, wherein each of said first and second core portions is generally J-shaped, and the extremities of said first and second core portions overlap each other when said jaws are in the closed position.

6. The sensing device of claim 3, wherein said core includes a plurality of stacked laminations.

7. The sensing device of claim 3, wherein said core includes a plurality of turns of an electrical conductor formed by winding a conductor around a mandrel.

8. The sensing device of claim 3, wherein one or more of said jaws and core portions are mounted for relative reciprocable movement.

9. The sensing device of claim 3, wherein at least one core portion is mounted for reciprocable movement relative to at least one jaw.

10. The sensing device of claim 3, wherein said first core portion is biased to shift in one direction relative to said first jaw.

11. The sensing device of claim 3, wherein said first and second core portions are biased to shift in one direction relative to said first and second jaws.

12. The sensing device of claim 11, wherein said core portions are biased by at least one spring.

13. The sensing device of claim 10, wherein said core includes a plurality of laminations formed by winding magnetic core material about a mandrel.

14. The sensing device of claim 10, wherein said first core portion is biased by at least one spring.

15. The sensing device of claim 3, wherein said power supply means includes a coil wound on said core, said core and said coil being spaced from said conductor, whereby the heat generated by said power supply means does not substantially affect the temperature of said overhead electric power line.

16. The sensing device of claim 15, wherein said housing includes a portion defining a heat sink for conducting heat generated by said core into the ambient environment, and said core portion is disposed within said housing portion.

17. The sensing device of claim 1, wherein said core and a portion of said housing circumscribe said overhead electric power line and said housing is defined by first and second halves, said first and second halves being substantially electrically isolated from each other at said housing portion to prevent said housing portion from creating a shorted coil-turn around said core.

18. The sensing device of claim 17, wherein said first and second housing halves are isolated from each other by a slot in the housing portions circumscribing the overhead electric power line conductor.

19. The sensing device of claim 1, wherein said first jaw is shiftably mounted on said housing by a mounting means having a co-efficient of thermal expansion different from that of said housing, said sensing device compensating for the effects of the difference in the co-efficients of thermal expansion of said mounting means and said housing.

20. The sensing device of claim 19, wherein the center of gravity of said housing is below the electric power line for reducing rotation of the housing around the axis of the power line and thus preventing the initiation of conductor galloping.

21. The sensing device of claim 19, wherein said mounting means includes a rotatable shaft mounted on said housing, and the differences in thermal expansion of the housing is compensated for by a third jaw spaced from said second jaw and opposing said first jaw, said first, second and third jaws being positioned to bend said overhead electric power line in a manner to impose a biasing pressure on said shaft and said housing.

22. The sensing device of claim 21, wherein the spaced apart first, second and third jaws create a moment on the power line for preventing the sensing device from sliding on the power line and for preventing the sensing device from rotating about an axis perpendicular to the axis of the power line.

23. The sensing device of claim 21, wherein said second and third jaws are spaced apart from each other and said first jaw is disposed between said second and third jaws, to create a moment on said ovehead electric power line and a spring-like action between said overhead electric power line and said jaws which compensates for the differences in thermal expansion between said housing and said mounting means.

24. The sensing device of claim 1, wherein said housing reduces arcing between said housing and said overhead electric power line when said device is installed on said overhead electric power line.

25. The sensing device of claim 24, wherein said arcing is reduced by providing an inclined surface against which said overhead electric power line may be abruptly contacted during installation of said device on said overhead electric power line.

26. The sensing device of claim 24, wherein said arcing is reduced by providing a protective insulated cover on at least part of said housing for contacting said power line in the event of improper installation of said device on said power line.

27. The sensing device of claim 3, wherein said housing includes a passageway therein into which said overhead electric power line may be received, and an opening in the periphery of said housing communicating with said passageway and allowing said overhead electric power line to be inserted into said passageway, said jaws being respectively disposed on opposite sides of said passageway, and said first jaw moves between first and second positions alternately extending across said opening and away from said opening.

28. The sensing device of claim 27, wherein said first and second core portions are enclosed for shielding said core sections from becoming sources of corona.

29. The sensing device of claim 1, wherein said housing is generally C-chaped so that said overhead electric power line may be inserted between the legs of the C-shaped housing, and said transformer includes a coil, said magnetic core of the transformer encircling said overhead electric power line when said jaws are closed, said core including a portion shiftable between a closed position defining a closed magnetic flux path and an open position in which said magnetic flux is interrupted.

30. The sensing device of claim 29, wherein when the first jaw is in the closed position thus, closing the flux path, the magnetic reluctance of the air gaps are constant and indpendent of the position of the first and second core portions, relative to each other.

31. The sensing device of claim 1, wherein said jaws include surfaces contoured to engage a plurality of different diameter overhead electric power lines.

32. The sensing device of claim 1, wherein said sensing means includes at least one temperature sensor, and said housing includes first and second chambers therein, adjacent said overhead electric power line and adjacent each other, said coil being mounted in said first chamber, said temperature sensor being mounted in said second chamber.

33. The sensing device of claim 1, wherein said sensing means includes a sensor mounted in one of said jaws for sensing the temperature of said overhead electric power line.

34. The sensing device of claim 33, wherein said sensor is positioned to avoid temperature gradients created by the presence of the housing.

35. The sensing device of claim 33, wherein said jaw in which the sensor is mounted is formed of a thermally insulating material.

36. The sensing device of claim 33, wherein said sensing means also includes a sensor for sensing ambient temperature adjacent said overhead electric power line.

37. The sensing device of claim 36, wherein said sensor for sensing ambient temperature is mounted in other of said jaws.

38. The sensing device of claim 36, wherein both said sensors are mounted in the same jaw.

39. The sensing device of claim 37, wherein both jaws are formed of thermally inslulating material.

40. The sensing device of claim 1, wherein the housing includes a third jaw for clamping said overhead electric power line, and wherein said sensing means includes first, second and third temperature sensors respectively mounted in said first, second and third jaws for sensing the ambient temperature adjacent said overhead electric power line and the temperature of said overhead electric power line.

41. The sensing device of claim 1, wherein said sensing means includes a temperature sensor for engaging and sensing the temperature of said overhead electric power line.

42. The sensing device of claim 41, wherein said temperature sensor includes a sensor probe for engaging said overhead electric power line and means for limiting the magnitude of heat conducted through said probe.

43. The sensing device of claim 42, wherein said sensor probe includes a construction in said probe defined by a reduced cross-sectional area.

44. The sensing device of claim 41, wherein said sensing means includes a sensing probe mounted for movement into engagement with said overhead electric power line.

45. The sensing device of claim 44, wherein said sensing means includes means for biasing said sensing probe into engagement with said overhead electric power line.

46. The sensing device of claim 41, wherein said means includes an elongated sensing probe and low mass means on one end of said probe for conformally contacting the surface of said overhead electric power line.

47. The sensing device of claim 1, wherein said sensing means is for sensing said directly sensed parameter when said housing is clamped on said line by said jaws;

and said sensing means is shiftably mounted on said housing, and biased into contact with said overhead electric power line.

48. The sensing device of claim 42, wherein said probe includes means for limiting the magnitude of heat conducted through said probe.

49. The sensing device of claim 48, wherein said means for limiting the heat conducted through the probe includes a constriction in said probe.

50. The sensing device of claim 47, wherein said sensing means is mounted in one jaw.

51. The sensing device of claim 47, wherein said sensing means conforms to the shape of and engages the overhead electric power line.

52. The sensing device of claim 1, wherein said sensing means includes means for sensing the magnitude of solar radiation impinging on said overhead electric power line and for transmitting the second magnitude of solar radiation to a receiving station.

53. The sensing device of claim 52, wherein said housing includes means for protecting said sensing means from corona current.

54. The sensing device of claim 53, wherein said housing includes a layer of transparent conductive material for protecting the sensing means from corona current.

55. The sensing device of claim 53, wherein said housing includes a conductive mesh for protecting the sensing means from corona current.

56. The sensing device of claim 52, wherein said sensing means includes an array of solar cells.

57. The sensing device of claim 56, wherein said solar cells are connected in parallel with each other.

58. The sensing device of claim 56, wherein said solar cells are connected in series with each other.

59. The sensing device of claim 1, wherein said sensing means includes means for sensing the velocity of wind flowing over said overhead electric power line and for transmitting the sensed wind velocity to a receiving station.

60. The sensing device of claim 59, wherein said sensing means also senses the direction of said wind and transmits the sensed wind direction to said receiving station.

61. The sensing device of claim 59, wherein said means for sensing wind velocity includes an electrically heated element, electrical current being supplied to said element to maintain the temperature of said element essentially constant, and means for sensing the magnitude of the electrical current supplied to said element, the sensed magnitude of electrical current being proportional to said wind velocity.

62. The sensing device of claim 59, wherein said means for sensing wind velocity includes a plurality of electrically heated elements each oriented to sense the velocity of said wind from a different direction, the velocity of said wind being proportional to the energy required to maintain said heated elements at a preselected temperature.

63. The sensing device of claim 62, wherein at least two of said elements are oriented at a predetermined angle relative to each other.

64. The sensing device of claim 59, wherein said means for sensing and transmitting wind direction and velocity includes a radio frequency transmitter provided with an elongated antenna, said heated elements being mounted on said antenna.

65. The sensing device of claim 62, wherein the heated elements are shielded from corona.

66. The device of claim 1, wherein the sensing means is for sensing the velocity of wind blowing over the overhead electric power line.

67. The device of claim 66, wherein said sensing means includes a plurality of sensing elements each positioned to sense the velocity of wind from a different direction.

68. The device of claim 66, wherein said sensing means further includes means for sensing the direction of said wind.

69. The device of claim 66, wherein said sensing means includes a sensing element mounted on top of said housing.

70. The sensing device of claim 1, wherein said transformer includes a secondary circuit and means for periodically shorting the secondary circuit of said transformer.

71. The sensing device of claim 70, wherein the sensing means includes means for sensing the magnitude of the voltage on the secondary of the transformer for transmitting data when sufficient power is stored in the power supply and/or for shorting the secondary so that the current in the overhead power line is sensed measured accurately without saturation of said magnetic core.

72. The sensing device of claim 1, wherein said housing includes first and second chambers, first and second electrical circuits respectively disposed in said first and second chambers and connected with said sensing means for controlling the operation of said device.

73. The sensing device of claim 72, wherein said first and second circuits are shielded by ferrous plates from magnetic fields produced by electrical current flowing through said overhead electrical power line.

74. The sensing device of claim 73, wherein said jaw is mounted on at least one track and said first circuit and said track is respectively mounted on opposite sides of one of said ferrous plates, and said second circuit and at least one other track being respectively mounted on opposite sides of the other of said ferrous plates.

75. The sensing device of claim 72, wherein said housing includes a pluarlity of holes therein communicating with each of said chambers and allowing air to flow through said chambers.

76. The sensing device of claim 1, wherein said sensing means includes means for sensing the inclination of said overhead electric power line and for transmitting the sensed inclination to a receiving statin for the purpose of measuring line sag.

77. The sensing device of claim 1, wherein said sensing means is for sensing the magnitude of the sag of said overhead electric power line.

78. The sensing device of claim 77, wherein said sensing means includes means for sensing the inclination of said housing.

79. The sensing device of claim 77, wherein the power supply means powers a transmitter for transmitting data relative to the magnitude of the sag.

80. The device of any of claim 59-65, wherein said transmitting means includes a radio transmitter provided with a transmitting antenna extending outwardly from said housing, and said sensing means are mounted on said antenna.

81. The device of claim 80, wherein said sensing means are symmetric about an axis through said power line.

82. The device of claim 80, wherein said housing includes means for shielding said sensing elements from corona.