Power-line sag calculation by way of power-system state estimation
View Patent ↗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.
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.