Power-line sag calculation by way of power-system state estimation

• US 7,494,271 B2
• Filed: 02/05/2007
• Issued: 02/24/2009
• Est. Priority Date: 02/05/2007
• Status: Expired due to Fees

• Current Assignee: ABB Power Grids Switzerland AG (Hitachi, Ltd.)
• Original Assignee: ABB Research Ltd. (ABB Limited)
• Inventors: Finney, John D., Scholtz, Ernst, Nuqui, Reynaldo F.
• Primary Examiner(s): Verbitsky; Gail
• Assistant Examiner(s): Jagan; Mirellys
• Application Number:
  US11/671,123
• Publication Number:
  US 20080189062A1
• Time in Patent Office: 750 Days
• Field of Search: 374/45, 374/185
• US Class Current: 374/45
• CPC Class Codes: H02J 3/00 Circuit arrangements for ac mains or ac distribution networks

Abstract

A sag calculator (122) computes sag for a span of a section of a power line based at least in part upon a temperature of conductor lines in the line section. A temperature calculator (120) determines the temperature by computing a resistance ascertained through augmented state estimation techniques performed by a state estimator (118). A Supervisory Control and Data Acquisition (SCADA) system (104) acquires data used by the state estimator (118) to compute the resistance.

Claims

1. A computer-implemented method comprising the following computer-executable acts:

estimating a resistance of a conductor line in a line section by way of estimation of an augmented state;

computing a temperature of the conductor line based at least in part upon the estimated resistance; and

calculating a sag for a span in the line section based at least in part upon the computed temperature.

2. The method of claim 1, wherein estimating the resistance of the conductor line comprises estimating a change in resistance from a nominal value retained in a network model.

3. The method of claim 1, further comprising updating a network model, wherein the resistance is estimated based at least in part upon parameters in the network model.

4. The method of claim 1, wherein estimating the resistance of the conductor line comprises estimating a state of an electrical power transmission and distribution system, and father wherein the augmented state estimation techniques are used to determine a change in resistance of the conductor line.

5. The method of claim 1, wherein calculating the sag for the span comprises computing the sag for the span based at least in part upon a relationship between thermal expansion and tension of the conductor line in the span.

6. The method of claim 1, further comprising computing multiple sags for multiple spans in a power transmission and distribution system based at least in part upon a state estimate of a subset of the power transmission and distribution system.

7. The method of claim 1, wherein the act of estimating the resistance includes estimating the resistance by way of combined state and parameter estimation.

8. The method of claim 1, wherein the act of estimating the resistance includes estimating the resistance by way of state estimation.

9. The method of claim 1, wherein the augmented state estimation techniques are iterative estimation techniques.

10. The method of claim 9, wherein estimating the resistance of the conductor line comprises performing state estimation using Kalman filters.

11. The method of claim 1, wherein calculating the sag for the span comprises computing a zero tension length for the conductor line in the span at a reference temperature as a function of a known length of the conductor line in the span at the reference temperature and a cross sectional area of the power-line conductor.

12. The method of claim 11, wherein calculating the sag for the span comprises computing a first length of the conductor line in the span at the received temperature as a function of the zero tension length for the conductor line in the span at the reference temperature, a coefficient of thermal expansion for a material of the conductor line, and a difference between the reference temperature and the received temperature.

13. The method of claim 12, wherein calculating the sag for the span comprises calculating a first tension of the conductor line in the span at the received temperature based at least in part upon a weight per unit length of the conductor line, a length of the span, and the computed first length of the conductor line in the span.

14. The method of claim 13, wherein calculating the sag for the span comprises computing a second length of the conductor line in the span at the received temperature as a function of the first length, the first tension, and the cross sectional area of the conductor line.

15. The method of claim 14, wherein calculating the sag for the span comprises computing a sag for the span at the received temperature as a function of the second length.

16. The method of claim 15, wherein calculating the sag for the span comprises computing a second tension of the conductor line in the span as a function of the computed sag of the span, the second length, and the weight per unit length of the conductor line.

17. The method of claim 16, wherein calculating the sag for the span comprises updating the first tension of the conductor line in the span at the received temperature as a function of the first tension and the second tension.