Dynamic line rating system with real-time tracking of conductor creep to establish the maximum allowable conductor loading as limited by clearance

• US 7,504,819 B2
• Filed: 01/17/2007
• Issued: 03/17/2009
• Est. Priority Date: 07/21/2004
• Status: Active Grant

• Current Assignee: Atecnum Corporation
• Original Assignee: Underground Systems, Inc.
• Inventors: Engelhardt, John
• Primary Examiner(s): Nguyen; Ha Tran T
• Assistant Examiner(s): Chan; Emily Y
• Application Number:
  US11/654,232
• Publication Number:
  US 20070200556A1
• Time in Patent Office: 790 Days
• Field of Search: 324/104, 324/106, 324/142, 702/65
• US Class Current: 324/106
• CPC Class Codes: G01K 1/143 for measuring surface temperatures
• CPC Class Codes: G01L 5/102 using sensors located at a non-interrupted part of the flexible member
• CPC Class Codes: H02G 7/00 Overhead installations of electric lines or cables installations of bus-bars H02G5/00
• CPC Class Codes: H02J 1/102 being switching converters H02J1/108, H02J1/12 take precedence
• CPC Class Codes: H02J 13/00006 characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment
• CPC Class Codes: H02J 13/00024 by means of mobile telephony
• CPC Class Codes: H02J 13/00034 the elements or equipment being or involving an electric power substation

Abstract

Maximum transmission line or conductor loading of an overhead transmission line or conductor spanning two transmission line towers is determined by using a sensing device clamped to the overhead transmission line. The sensing device acquires real-time information that is used in an iterative process to determine sag, limiting temperature, maximum current load and minimum clearance of the transmission line or conductor.

Claims

1. An apparatus for determining the maximum conductor current loading of an overhead transmission line or conductor that comprises a spanning transmission line catenary spanning two transmission line towers, comprising:

a sensing device adapted to be clamped to said overhead transmission line or conductor near one of the two said transmission line towers to acquire real-time information and including a transmitter for transmitting said acquired real-time information to a remote information processing center, said acquired real-time information including at least parameters of an angle of inclination from a horizontal line of said transmission line or conductor and a surface temperature of said transmission line or conductor; and

means for performing a two step iterative process using said angle of inclination to determine the present sag of said transmission line or conductor;

wherein said performing means performs a first step that operates in accordance with the algorithm wherein a value for said conductor'"'"'s unit weight w and a value for horizontal tension in the conductor F_h is assumed and a horizontal distance X₁ from the lowest point of said spanning transmission line catenary to said transmission line tower closest to said sensor is first assumed to be equal to a horizontal distance X₂ from said lowest point to the other said transmission line tower, wherein X₁+X₂=X₀, the horizontal distance between said two transmission line towers, and Y₁ and Y₂ are sags relative to said respective transmission line towers determined in accordance with the following Equation (1);

$\begin{array}{cc}\mathrm{Sag}=Y=\frac{F_h}{w}<br><br>\left[\mathrm{Cosh}<br><br>\left(\frac{w}{F_h}<br><br>X\right)-1\right]& \left(1\right)\end{array}$

and X₁ is reduced by an incremental amount and X₂ is increased by said incremental amount if Y₂−

Y₁<

H, where H is the difference in height between said transmission line towers and said Equation (1) is repeated successively until Y₂−

Y₁≧

H, at which time X₁ is increased by said incremental amount and X₂ is reduced by said incremental amount, said incremental amount is decreased by dividing it by a fixed factor, said decreased incremental amount is subtracted from X₁ and added to X₂ and said sags Y₁ and Y₂ are computed in accordance with Equation (1), said difference Y₂−

Y₁ is compared to said H, and said iterative process is repeated successively until Y₂−

Y₁ is substantially equal to said H, thereby determining the position of said lowest point of said catenary consistent with said assumed horizontal tension F_h.

2. The apparatus according to claim 1 wherein said performing means performs a second step that operates in accordance with the algorithm wherein a value for an angle θ

from a horizontal line to a line tangent to said catenary at the end closest to said sensor is calculated using said assumed value for said horizontal tension F_h and said determined position of said lowest point of said catenary defined by X₁ and X₂, said angle θ

being calculated by computing the length of the arc S₁ between said end point of said catenary closest to said sensor and said lowest point of said catenary in accordance with Equation (2);

$\begin{array}{cc}\mathrm{Arc}=S_1=\frac{F_h}{w}<br><br>\mathrm{Sinh}<br><br>\left(\frac{w}{F_h}<br><br>X_1\right)& \left(2\right)\end{array}$

and said arc S₁ has a weight W₁, wherein W₁=w S₁ and said angle θ

is computed with Equation (3);

θ

=Tan<sup>−

1</sup>(W₁/F_h) 

 

(3)

wherein said angle θ

is compared to said acquired angle and if said angle is greater than said acquired angle, said assumed value for the horizontal tension, F_h, is incrementally increased whereafter said first step is repeated with said increased value of F_h to establish the location of a new lowest point of said catenary, and said second step is repeated to determine a new angle θ

that is compared to said acquired angle, thereby the value of said F_h is increased until the angle θ

is no longer greater than said acquired angle, whereupon said F_h is decreased by said increment, said increment is decreased by dividing it by a factor, said decreased increment is added to F_h, and said first and second steps are repeated until said computed angle θ and

said acquired angle are substantially equal, whereupon said horizontal tension F_h and said location of the lowest point of the catenary are established for the conditions in effect at the time said angle of inclination is acquired.

3. The apparatus according to claim 1, wherein said performing means includes means using said acquired conductor surface temperature to correct the conductor reference weight for thermal expansion effects.

4. The apparatus according to claim 1 wherein said performing means performs a second step that operates in accordance with the algorithm wherein a sag calculated with said Equation (1) is compared to a pre-defined allowable maximum sag at the lowest point of the catenary, and if said calculated sag is greater than said pre-defined allowable maximum sag, the assumed horizontal tension F_h is incrementally increased whereafter said first step is repeated with said increased value of F_h to establish the location of a new lowest point of the catenary, and said second step is repeated to determine a new sag that is compared to said pre-defined allowable maximum sag, thereby the value of said F_h is increased until said calculated sag is no longer greater than said pre-defined allowable maximum sag, whereupon said F_h is decreased by said increment, said increment is decreased by dividing it by a factor, said decreased increment is added to F_h, and said first and second steps are repeated until said calculated sag and said pre-defined allowable maximum sag are substantially equal, whereupon said horizontal tension F_h and said location of the lowest point of the catenary are established for the conditions in effect at the time that the sag of the catenary equals said pre-defined allowable maximum sag.

5. The apparatus according to claim 4, wherein said performing means determines a limiting maximum temperature of said transmission line or conductor based on said maximum sag or said minimum clearance.

6. The apparatus according to claim 1 wherein said performing means performs a second step that operates in accordance with the algorithm wherein a clearance between elevations of a point on the catenary and a specific point below the catenary is calculated with said Equation (1) wherein the X parameter is set equal to X₁ or X₂, whichever contains said point on the catenary, minus the distance from the respective tower to said point on the catenary, and the clearance, computed as the difference between the elevation of said respective tower minus said sag Y₁ or Y₂ associated with X₁ or X₂, plus said sag computed with said X parameter, minus said elevation of said specific point, is compared to a pre-defined allowable minimum clearance, and if said clearance is less than said pre-defined allowable minimum clearance, the assumed horizontal tension F_h is incrementally increased whereafter said first step is repeated with said increased value of F_h to establish the location of a new lowest point of the catenary, and said second step is repeated to determine a new clearance that is compared to said pre-defined allowable minimum clearance, thereby the value of said assumed F_h is increased until said calculated clearance is no longer greater than said pre-defined allowable minimum clearance, whereupon said F_h is decreased by said increment, said increment is decreased by dividing it by a factor, said decreased increment is added to F_h, and said first and second steps are repeated until said calculated clearance and said pre-defined allowable minimum clearance are substantially equal, whereupon said horizontal tension F_h and said location of the lowest point of the catenary are established for the conditions in effect at the time that the clearance of the catenary equals said pre-defined allowable minimum clearance.

7. The apparatus according to claim 6, wherein said performing means determines a limiting maximum temperature of said transmission line or conductor based on said maximum sag or said minimum clearance.

8. The apparatus according to claim 1, wherein said performing means includes means for obtaining a measure of the present load current on said transmission line or conductor to determine present weather conditions controlling present heat dissipation parameters of said transmission line or conductor.

9. The apparatus according to claim 8, wherein said performing means includes means for computing maximum allowable load current with said present weather conditions that limits the temperature of said transmission line or conductor to said maximum allowed temperature.