Method and device for estimating source impedances across one or more transmission lines

Patent metadata

Field	Value
Publication number	US-11916367-B2
Application number	US-202117475972-A
Country	US
Kind code	B2
Filing date	Sep 15, 2021
Priority date	Sep 15, 2020
Publication date	Feb 27, 2024
Grant date	Feb 27, 2024

Abstract

The present invention relates to estimating source impedances across one or more transmission lines connecting at least two substations. Each substation is associated with an equivalent source having a respective source impedance. Voltage and current measurements and status signals are obtained. The voltage and current measurements provide terminal or bus voltages and line currents at each terminal, and the status signals are associated with switching events at the one or more transmission lines or at the substations. An event associated with a disturbance or current injection is detected from one or more of the obtained measurements and the obtained status signals. The source impedance of each equivalent source is estimated based on the event, using line parameters and the voltage and current measurements associated with the event.

First claim

The invention claimed is:

1. A method for estimating source impedances across one or more transmission lines connecting at least two substations, each substation associated with an equivalent source having a respective source impedance, the method comprising:
obtaining voltage and current measurements and status signals, the voltage and current measurements providing terminal voltages and line currents at each substation, and the status signals being associated with switching events at the one or more transmission lines or at the substations;
detecting an event associated with a disturbance in a transmission line or current injection at one of the substations, the event being detected from one or more of the obtained measurements and the obtained status signals; and
estimating the source impedance of each equivalent source based on the event, using line parameters and the voltage and current measurements associated with the event, the measurements associated with the event comprising the measurements before and after the event.

2. The method of claim 1 , wherein the line parameters comprise one or more of characteristic impedance and propagation constant of a transmission line.

3. The method of claim 2 , wherein the line parameters further comprise line length of the transmission line.

4. The method of claim 1 , wherein the source impedance being further estimated using a fault current or a current injected at a terminal of the substation.

5. The method of claim 1 , wherein the disturbance is a fault on one of the one or more transmission lines, and wherein estimating the source impedance of each equivalent source comprises:
estimating a fault location on the transmission line;
calculating a fault current using the estimated fault location;
calculating two bus impedances, each bus impedance being associated with a respective terminal of the one or more transmission lines, and calculated using a change in the terminal voltages of the corresponding terminal and the calculated fault current;
calculating one or more of line and section impedances using the line parameters and the estimated fault location, wherein the section impedances are impedances of line sections located between the terminals and the estimated fault location; and
estimating the source impedance of each equivalent source using one or more of the calculated line impedance and the calculated section impedances, and the two bus impedances.

6. The method of claim 5 , wherein calculating each bus impedance comprises multiplying the bus impedance with a correction factor, wherein the correction factor is calculated using a ratio of a fault voltage and the calculated fault current, and shunt admittances of the line sections, wherein the fault voltage is calculated using the estimated fault location, and the shunt admittances are calculated using the estimated fault location and the line parameters,
optionally wherein estimating the source impedance comprises removing contribution of shunt admittance, wherein the contribution of shunt admittance is calculated using one or more of the shunt admittance of the at least one transmission line, and the shunt admittances of the line sections calculated using on the fault location and the line parameters.

7. The method of claim 1 , wherein the estimated source impedance is a complex source impedance having both magnitude and angle.

8. The method of claim 1 , wherein the estimated source impedance is used in configuring one of a protection function and a control function in a substation device.

9. A computer program product for estimating source impedances across one or more transmission lines, the computer program product comprising a non-transitory computer readable storage medium comprising instructions that, when executed by a processor, cause the processor to execute the method of claim 1 .

10. A device for estimating source impedances across one or more transmission lines connecting at least two substations, each substation associated with an equivalent source having a respective source impedance, the device comprising:
a data acquisition unit configured to obtain voltage and current measurements and status signals, the voltage and current measurements providing terminal voltages and line currents at each substation, and the status signals being associated with switching events at the one or more transmission lines or at the substations;
a signal processing unit communicatively coupled to the data acquisition unit and configured to:
detect an event associated with a disturbance in one of the one or more transmission lines or current injection at one of the substations, the signal processing unit configured to detect the event from one or more of the obtained measurements and the obtained status signals; and
estimate the source impedance of the equivalent source based on the event, using line parameters and the voltage and current measurements associated with the event, the measurements associated with the event comprising the measurements before and after the event; and
a control unit communicatively coupled to the signal processing unit.

11. The device of claim 10 , wherein the line parameters comprise one or more of characteristic impedance and propagation constant of a transmission line.

12. The device of claim 11 , wherein the line parameters further comprise line length of the transmission line.

13. The device of claim 10 , wherein the source impedance being further estimated using a fault current or a current injected at a terminal of the substation.

14. The device of claim 10 , wherein the disturbance is a fault on one of the one or more transmission lines, and wherein the signal processing unit is configured to:
estimate a fault location on the transmission line;
calculate a fault current using the estimated fault location;
calculate two bus impedances, each bus impedance being associated with a respective terminal of the one or more transmission lines, and calculated using a change in the terminal voltages of the corresponding terminal and the calculated fault current;
calculate one or more of line and section impedances using the line parameters and the estimated fault location, wherein the section impedances are impedances of line sections located between the terminals and the estimated fault location; and
estimate the source impedance of each equivalent source using one or more of the calculated line impedance and the calculated section impedances, and the two bus impedances.

15. The device of claim 14 , wherein the signal processing unit is configured to calculate each bus impedance by multiplying the bus impedance with a correction factor, wherein the correction factor is calculated using a ratio of a fault voltage and the calculated fault current, and shunt admittances of the line sections, wherein the fault voltage is calculated using the estimated fault location, and the shunt admittances are calculated using the estimated fault location and the line parameters,
optionally wherein the signal processing unit is configured to estimate the source impedance by removing contribution of shunt admittance, wherein the contribution of shunt admittance is calculated using one or more of the shunt admittance of the at least one transmission line, and the shunt admittances of the line sections calculated using on the fault location and the line parameters.

16. The device of claim 10 , wherein the device is a substation server,
optionally wherein the substation server is communicatively coupled with one or more measurement equipment and the switching devices; or
wherein

Assignees

• Hitachi Energy Switzerland Ag

Inventors

• Pradhan Vedanta
• Naidu Od

Classifications

• H02H3/006 Primary

  Calibration or setting of parameters · CPC title

• G01R19/2513 Primary

  Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging · CPC title

• G01R31/085

  in power transmission or distribution lines, e.g. overhead · CPC title

• G01R27/08 Primary

  Measuring resistance by measuring both voltage and current · CPC title

• G01R31/08

  Locating faults in cables, transmission lines, or networks · CPC title