Power transmission line tension monitoring system

• US 5,517,864 A
• Filed: 05/31/1994
• Issued: 05/21/1996
• Est. Priority Date: 05/31/1994
• Status: Expired due to Term

• Current Assignee: Nexans Incorporated (Nokia Corporation)
• Original Assignee: Tapani O. Seppa
• Inventors: Seppa, Tapani O.
• Primary Examiner(s): Chilcot, Jr., Richard E.
• Assistant Examiner(s): Dougherty, Elizabeth L.
• Application Number:
  US08/251,242
• Time in Patent Office: 721 Days
• Field of Search: 73/862.391, 73/862.541, 324/105, 324/106, 324/127, 307/62, 340/870.3, 174/40 R, 174/40 TD, 174/45 R, 174/45 TD, 174/149 R, 364/492, 364/508, 364/550, 364/556
• US Class Current: 73/862.391
• CPC Class Codes: G01L 5/103 using sensors fixed at one end of the flexible member

Abstract

A system for determining the sag of an overhead power transmission line to prevent flashover to adjacent objects on earth. Power line tension is measured as well as ambient temperature at two different times. From these measurements the Ruling Span of a power line can be calculated from which a determination can be made of the maximum safe current to avoid unsafe line sag.

Claims

1. The method of determining the Ruling Span of an electrical power line suspension section comprising the steps of:

discontinuing the transmission of electrical current through the power line for a period of time sufficient for the power line to cool to substantially ambient temperature;

measuring the temperature and tension of the power line to ascertain a first conductor temperature and tension;

discontinuing the transmission of electrical current through the power line a second time for a period of time sufficient for the power line to cool to substantially ambient temperature;

measuring the temperature and tension of the power line to ascertain a second conductor temperature and tension; and

calculating the Ruling Span and sag of the power line suspension.

2. The method of determining the Ruling Span of a power line suspension section in which the Ruling Span is defined by the formula:

##EQU3## in which 1₁ . . . 1_n are the individual span lengths in the suspension section comprising the steps of

measuring the tension T₁ and temperature t_a1 of the section conductor with no current passing through the conductor,

measuring the tension T₂ and temperature t_a2 of the section conductor at a different time with no current passing through the conductor;

calculating the Ruling Span by the following formula ##EQU4## in which β

=coefficient of thermal elongation

E=Youngs Modulus of the conductor

A=cross section of the conductor

C=catenary constant

calculating a tension/sag table for the suspension section.

3. A system for determining the sag of an overhead power transmission suspension section comprising:

a power transmission section having two terminal ends;

tension measuring means connected to the transmission section to produce a first electrical signal representative of the power line tension;

temperature measuring means connected to the transmission section to produce a second electrical signal responsive to the temperature of the suspension section;

means whereby said tension measuring means and said temperature measuring means simultaneously measure the tension and temperature of the said transmission section whereby said first and second electrical signals are responsive to the simultaneous measurements; and

means to transmit said first and second electrical signals to a distant location for processing to determine the sag of the suspension section.

4. The system set forth in claim 3 including transceiver means connected to receive the first and second signals and transmit them to the distant location;

and

means at the distant location to transmit control signals to the transceiver means.