Net radiation sensor

• US 5,559,430 A
• Filed: 07/27/1994
• Issued: 09/24/1996
• Est. Priority Date: 07/27/1994
• Status: Expired due to Term

• Current Assignee: Nexans Incorporated (Nokia Corporation)
• Original Assignee: Tapani O. Seppa
• Inventors: Seppa, Tapani O.
• Primary Examiner(s): Karlsen, Ernest F.
• Assistant Examiner(s): KOBERT, RUSSELL MARC
• Application Number:
  US08/280,995
• Time in Patent Office: 790 Days
• Field of Search: 73/862.391, 324/106, 324/127, 324/126, 324/158.1, 374/45, 340/870.17, 364/578, 395/500
• US Class Current: 324/105
• CPC Class Codes: G01K 1/024 for remote indication
• CPC Class Codes: G01K 2007/422 Dummy objects used for estimating temperature of real objects

Abstract

A system for determining the sag of an overhead power transmission line to prevent flashover to adjacent objects on earth. A small replica of the transmission line conductor is provided and located in proximity to the transmission line. The temperature of the replica is measured along with the ambient temperature. By appropriate calculations, the ampacity determination is made to determine the maximum permitted current through the transmission line under the particular weather conditions.

Claims

1. The method of determining the maximum designed current carrying capacity of an electrical power line conductor mounted between transmission towers providing a predetermined location and directional orientation under particular solar heating conditions in which ##EQU3## q_c is the convective heat loss q_r is the radiation heat loss

q_s is the heat from solar radiation

comprising:

the steps of providing a conductor section having substantially the same cross sectional area, heat capacity, and heat emissivity/absorptivity of the power line conductor;

locating the said conductor section in close proximity to the power line conductor;

orienting the said conductor section in a direction corresponding to the directional orientation of the power line conductor;

measuring the ambient temperature at the location of the conductor section;

measuring the temperature of the conductor section; and

calculating the maximum current using the said ambient temperature and conductor temperature measurements.

2. The method set forth in claim 1 in which the conductor section is made of the same material as the power line conductor.

3. The method of determining the maximum designed current carrying capacity of an electric power line conductor under particular solar heating conditions comprising;

providing a sectional replica of the power line conductor having the same heating characteristics thereof;

locating the replica in the proximity of the power line conductor whereby the solar heating conditions of the replica and the power line conductor are substantially the same;

measuring the solar heating effect on the replica; and

calculating the maximum design current carrying capacity of the power line conductor under the said particular solar heating conditions.

4. The method of claim 3 in which the step of measuring the solar heating effect on the replica comprises measuring the temperature of the replica and the ambient temperature of the replica.

5. The method of claim 4 in which the calculation of the designed current is made according to the formula:

##EQU4## in which q_c is the convective heat loss

q_r is the radiation heat loss

q_s is the heat from solar radiation.

6. A portable device for monitoring the current carrying capacity of an electrical power line conductor comprising;

an enclosure;

a section of an overhead power line conductor;

said section being of the same material as the electrical power line being monitored;

mounting means to secure one end of said section to the enclosure;

said mounting means including swivel means to permit said section to be pivoted in three-dimensional space;

temperature measuring means connected to said section to measure the temperature thereof;

ambient temperature measuring means to measure the surrounding ambient temperature; and

visually indicating means to display the temperature and ambient temperature.

7. The device set forth in claim 6 including means to transmit said temperature measurements and ambient temperature measurements to a location distant from said device.