Parameter Free Traveling Wave Based Fault Location for Power Transmission Lines

Abstract

A method can be used for fault location in a power transmission line connecting a first terminal with a second terminal. Arrival times of a first peak and a second peak of travelling waves are detected from measurements carried out at the first and second terminals. a rough location of a fault is identified based on a comparison of the arrival times obtained for the travelling waves detected from the measurements carried out at the first terminal, and the arrival times obtained for the travelling waves detected from the measurements carried out at the second terminal. The fault location is estimated based the rough location, the arrival times of the first and second peaks of the travelling waves detected from measurements carried out at the first and second terminals, and a length of the power transmission line.

Claims

1-10. (canceled)

11. A method for fault location in a power transmission line connecting a first terminal with a second terminal, wherein the method is implemented with a processor of a device associated with the power transmission line, the method comprising: obtaining arrival times of a first peak and a second peak of travelling waves detected from measurements carried out at the first and second terminals; identifying a rough location of a fault based on a comparison of the arrival times obtained for the travelling waves detected from the measurements carried out at the first terminal, and the arrival times obtained for the travelling waves detected from the measurements carried out at the second terminal, the rough location being one of a first half, a second half, or a mid-point of the power transmission line; and estimating the fault location based the rough location, the arrival times of the first and second peaks of the travelling waves detected from measurements carried out at the first and second terminals, and a length of the power transmission line.

12. The method of claim 11, wherein identifying the rough location comprises comparing (tn2tm1) with (tm2tn1), wherein tm1 and tm2 are the arrival times of the first and second peaks obtained for the travelling wave detected from the measurements carried out at the first terminal, and tn1 and tn2 are the arrival times of the first and second peaks obtained for the travelling wave detected from the measurements carried out at the second terminal.

13. The method of claim 12, wherein the fault is identified as being in the first half when (tn2tm1) is greater than (tm2tn1) and the fault is identified as being in the second half when (tm2tn1) is greater than (tn2tm1).

14. The method of claim 13, wherein the fault location in the first half of the line is estimated from $(((tm .Math. .Math. 2 - tm .Math. .Math. 1) + (tn .Math. .Math. 2 - tn .Math. .Math. 1)) \frac{L}{4 .Math. (tn .Math. .Math. 2 - tm .Math. .Math. 1)});$ and wherein the fault location in the second half of the line is estimated from $(L - ((tm .Math. .Math. 2 - tm .Math. .Math. 1) + (tn .Math. .Math. 2 - tn .Math. .Math. 1)) \frac{L}{4 .Math. (tm .Math. .Math. 2 - tn .Math. .Math. 1)}),$ wherein L is the length of the power transmission line.

15. The method of claim 13, wherein the mid-point of the power transmission line is identified as having the fault when the difference between (tn2tm1) and (tm2tn1) is less than a threshold value.

16. The method of claim 12, wherein the fault location in the first half of the line is estimated from $(((tm .Math. .Math. 2 - tm .Math. .Math. 1) + (tn .Math. .Math. 2 - tn .Math. .Math. 1)) \frac{L}{4 .Math. (tn .Math. .Math. 2 - tm .Math. .Math. 1)}),$ wherein L is the length of the power transmission line.

17. The method of claim 12, wherein the fault location in the second half of the line is estimated from $(L - ((tm .Math. .Math. 2 - tm .Math. .Math. 1) + (tn .Math. .Math. 2 - tn .Math. .Math. 1)) \frac{L}{4 .Math. (tm .Math. .Math. 2 - tn .Math. .Math. 1)}),$ wherein L is the length of the power transmission line.

18. The method of claim 12, wherein the mid-point of the power transmission line is identified as having the fault when the difference between (tn2tm1) and (tm2tn1) is less than a threshold value.

19. The method of claim 18, wherein the fault location is estimated by taking an average of first and second fault locations, wherein the first fault location is estimated for a fault in the first half of the line and the second fault location is estimated for a fault in the second half of the line.

20. A device for fault location in a power transmission line connecting first and second terminals, the device comprising: a travelling wave detector configured to obtain arrival times of a first peak and a second peak of travelling waves detected from measurements carried out at the first and second terminals; a faulty half identifier for identifying one of a first half, a second half, and a mid-point of the power transmission line as having the fault, based on a comparison of the arrival times obtained for the travelling wave detected from the measurements carried out at the first terminal, and the arrival times obtained for the travelling wave detected from the measurements carried out at the second terminal; and a fault locator for estimating the fault location based on the identification of the first half, the second half or the mid-point as having the fault, the arrival times of the first and second peaks of the travelling waves detected from the measurements carried out at the first and second terminals, and a length of the power transmission line.

21. The device of claim 20, wherein the device is an intelligent electronic device associated with the first terminal.

22. The device of claim 21, wherein the device is configured to receive the measurements carried out at the corresponding terminal from measurement equipment associated with the first terminal, and to receive the measurements carried out at the second terminal over a communication channel from a device associated the second terminal of the power transmission line.

23. The device of claim 20, wherein the device is a server connected with intelligent electronic devices associated with the first and second terminals, respectively.

24. The device of claim 23, wherein the server is configured to receive travelling wave parameters obtained by the intelligent electronic devices from the measurements carried out at the respective terminals.

25. A method for fault location in a power transmission line connecting a first terminal with a second terminal, the method comprising: measuring voltages or currents at the first terminal; measuring voltages or currents at the second terminal; calculating arrival times of a first peak and a second peak of travelling waves at the first terminal based on the measurements of the voltages or currents carried at the first terminal; calculating arrival times of the first peak and the second peak of the travelling waves at the second terminal based on the measurements of the voltages or currents carried at the second terminal; identifying a rough location of a fault based on a comparison of the arrival times calculated based on the measurements at the first terminal and the arrival times calculated based on the measurements at the second terminal, the rough location being one of a first half of the power transmission line, a second half of the power transmission line, or a mid-point of the power transmission line; and estimating the fault location based the rough location, the arrival times calculated based on the measurements at the first terminal, the arrival times calculated based on the measurements at the second terminal, and a length of the power transmission line.

26. The method of claim 25, wherein identifying the rough location comprises comparing (tn2tm1) with (tm2tn1), wherein tm1 and tm2 are the arrival times of the first and second peaks calculated based on the measurements at the first terminal, and tn1 and tn2 are the arrival times of the first and second peaks calculated based on the measurements at the second terminal.

27. The method of claim 26, wherein the fault is identified as being in the first half when (tn2tm1) is greater than (tm2tn1) and the fault is identified as being in the second half when (tm2tn1) is greater than (tn2tm1).

28. The method of claim 26, wherein the fault location in the first half of the line is estimated from $(((tm .Math. .Math. 2 - tm .Math. .Math. 1) + (tn .Math. .Math. 2 - tn .Math. .Math. 1)) \frac{L}{4 .Math. (tn .Math. .Math. 2 - tm .Math. .Math. 1)})),$ wherein L is the length of the power transmission line.

29. The method of claim 26, wherein the fault location in the second half of the line is estimated from $(L - ((tm .Math. .Math. 2 - tm .Math. .Math. 1) + (tn .Math. .Math. 2 - tn .Math. .Math. 1)) \frac{L}{4 .Math. (tm .Math. .Math. 2 - tn .Math. .Math. 1)}),$ wherein L is the length of the power transmission line.

30. The method of claim 26, wherein the mid-point of the power transmission line is identified as having the fault when the difference between (tn2tm1) and (tm2tn1) is less than a threshold value.

31. The method of claim 30, wherein the fault location is estimated by taking an average of first and second fault locations, wherein the first fault location is estimated for a fault in the first half of the line and the second fault location is estimated for a fault in the second half of the line.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0027] The subject matter of the invention will be explained in more detail in the following text with reference to exemplary embodiments which are illustrated in attached drawings in which:

[0028] FIGS. 1(a) and 1(b) show Bewley lattice diagrams for faults in first and second halves of a power transmission line;

[0029] FIG. 2 is a flowchart of a method for fault location in the power transmission line, in accordance with an embodiment of the invention;

[0030] FIG. 3 is a simplified block diagram of a device for fault location, in accordance with an embodiment of the invention; and

[0031] FIG. 4 is a simplified representation of a system for fault location, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

[0032] The present invention proposes a method which is independent of line parameters. In other words, the present invention provides parameter free traveling wave based fault location for power transmission lines. The system and method of the present invention do not require experiments to calibrate the propagation velocity for deployment of a fault location solution.

[0033] FIG. 1(a) shows a Bewley lattice diagram for a case when the fault has occurred in the first half of the line. In this case, at bus M side, for travelling wave generated from the fault point, the first peak as well as the second peak arrived from the fault point (i.e. not as a reflection from N-side). At bus N side, for travelling wave generated from the fault point, the first peak arrived from fault point, and the second peak arrived from far end bus (i.e. from M side) as a result of a reflected wave as shown.

[0034] The fault location can be calculated as follows. From FIG. 1(a) Bewley lattice diagram, we can write:

[00003] $\begin{matrix} \begin{matrix} tm .Math. .Math. 1 = t .Math. .Math. 0 + \frac{d .Math. .Math. 1}{V}; & tm .Math. .Math. 2 = t .Math. .Math. 0 + \frac{3 .Math. d .Math. .Math. 1}{V} \end{matrix} & (1) \\ \begin{matrix} tn .Math. .Math. 1 = t .Math. .Math. 0 + \frac{L - d .Math. .Math. 1}{V}; & tn .Math. .Math. 2 = t .Math. .Math. 0 + \frac{d .Math. .Math. 1 + L}{V} \end{matrix} & (2) \end{matrix}$

where, t0=fault inception or detected time, tm1 and tm2=first and second peak arrival times at bus M; tn1 and tn2=first and second peak arrival times at bus N; and d1=fault location in case of a fault is in a first half of the line.

[0035] Solving the equations (1) and (2), fault location is given by equation (3)

[00004] $\begin{matrix} d .Math. .Math. 1 = ((tm .Math. .Math. 2 - tm .Math. .Math. 1) + (tn .Math. .Math. 2 - tn .Math. .Math. 1)) \frac{L}{4 .Math. (tn .Math. .Math. 2 - tm .Math. .Math. 1)} & (3) \end{matrix}$

[0036] FIG. 1(b) shows a Bewley lattice diagram for a case, when the fault has occurred in the second half of the line. In this case, at bus M side, the first peak arrived from the fault point and the second peak arrived from the far end bus (i.e. from N side), and at bus N side, the first peak as well as the second peak arrived from the fault point. Here, the fault location can be calculated as follows. From FIG. 1(b) Bewley lattice diagram, we can write,

[00005] $\begin{matrix} \begin{matrix} tm .Math. .Math. 1 = t .Math. .Math. 0 + \frac{d .Math. .Math. 2}{V}; & tm .Math. .Math. 2 = t .Math. .Math. 0 + \frac{2 .Math. L - d .Math. .Math. 2}{V} \end{matrix} & (4) \\ \begin{matrix} tn .Math. .Math. 1 = t .Math. .Math. 0 + \frac{L - d .Math. .Math. 2}{V}; & tn .Math. .Math. 2 = t .Math. .Math. 0 + \frac{3 .Math. (L - d .Math. .Math. 2)}{V} \end{matrix} & (5) \end{matrix}$

where, tm1 and tm2=first and second peak arrival times at bus M; tn1 and tn2=first and second peak arrival times at bus N; and d2=fault location if fault is in the second half.

[0037] Solving the equations (4) and (5), fault location is given by equation (6)

[00006] $\begin{matrix} d .Math. .Math. 2 = L - ((tm .Math. .Math. 2 - tm .Math. .Math. 1) + (tn .Math. .Math. 2 - tn .Math. .Math. 1)) \frac{L}{4 .Math. (tm .Math. .Math. 2 - tn .Math. .Math. 1)} & (6) \end{matrix}$

[0038] Hence, we need to select the actual fault location from the two fault location estimates calculated using equation (3) and (6). For this, we need to know if the fault has occurred in the first half or the second half of the line.

[0039] Faulty Half (or Section) Identification:

[0040] The faulty half (i.e. first half from bus M to mid-point, or second half from bus N to mid-point) can be determined from comparison of the arrival times of the peaks detected at bus M and bus N.

[0041] From equation (1) and (2), we have

(tn2tm1)=L(7)

(tm2tn1)=4d1L(8)

[0042] Comparing equation (7) and (8) gives the below relationship (9)

(tn2tm1)>(tm2tn1).fwdarw.L>4d1L(9)

[0043] Here, the fault can be identified in the first half (or section), if the difference of the second arrival time measured at bus N and the first arrival time measured at bus M, is always greater than difference of the second arrival time measured at bus M and the first arrival time measured at bus N for a condition (0<L/4<L/2).

[0044] We can identify the faulty half by using following relationships:

(tn2tm1)(tm2tn1)e.fwdarw.Fault is in middle of the line(10)

(tn2tm1)>(tm2tn1).fwdarw.Fault is in first half of the line(11)

(tn2tm1)<(tm2tn1).fwdarw.Fault is in second half of the line(12)

[0045] In the above, e is small threshold and approximately zero. The threshold value may be determined according to the sampling frequency. For example, for a 1 MHz sampling the threshold can be 1 or 2 micro seconds. The threshold value can be determined beforehand (e.g. set by a personnel).

[0046] Referring now to FIG. 2, which is a flowchart of the method for fault location in the power transmission line, in accordance with an embodiment of the invention.

[0047] At 202, travelling wave parameters are obtained. In case the fault locators shown in FIGS. 1(a) and 1(b), are used for implementing the method, travelling waves can be detected by the fault locators at bus M (first terminal) and bus N (second terminal) respectively. Alternately, a travelling wave detector may be used for detecting the travelling wave and obtaining the parameters (e.g. arrival time, peak width, rise time etc.) thereof. The travelling wave detector may be a standalone device (connected with the measurement equipment such as CT at bus M) or a module implemented with a processor of a power system device (such as 302).

[0048] In accordance with some embodiments (e.g. illustrated with FIGS. 1(a) and 1(b)), the first and second peak arrival times at bus M (tm1 and tm2) and bus N (tn1 and tn2) are obtained.

[0049] The method also comprises identifying the faulty half, or the mid-point as having the fault. The faulty half (or mid-point) of the line is identified with the fault based on a comparison of the arrival times for the first and second peaks at bus M and N respectively. In the embodiment of FIG. 2, at 204, the difference between (tn2tm1) and (tm2tn1) is compared with the threshold value (e.g. e) to identify the faulty half.

[0050] According to the comparison at 204, another comparison of the arrival times can be performed at 206, to identify the faulty half. For example, it can be determined if (tn2tm1) is greater than (tm2tn1). Accordingly, the fault can be determined to be located in the first half, or the second half of the line (refer description above). First half in accordance with the examples shown would refer to the part of the line from bus M to the mid-point, which has length L/2, and similarly second half would refer to the part from bus N to the mid-point, which also has length L/2.

[0051] If the fault is identified in the first half based on comparison at 206, the fault location (d1) can be estimated at 208 using C(3), i.e.:

[00007] $d .Math. .Math. 1 = ((tm .Math. .Math. 2 - tm .Math. .Math. 1) + (tn .Math. .Math. 2 - tn .Math. .Math. 1)) \frac{L}{4 .Math. (tn .Math. .Math. 2 - tm .Math. .Math. 1)} .$

[0052] If the fault in identified in the second half based on comparison at 206, the fault location (d2) can be estimated at 210 using C(6), i.e.:

[00008] $d .Math. .Math. 2 = L - ((tm .Math. .Math. 2 - tm .Math. .Math. 1) + (tn .Math. .Math. 2 - tn .Math. .Math. 1)) \frac{L}{4 .Math. (tm .Math. .Math. 2 - tn .Math. .Math. 1)} .$

[0053] In case the fault location is identified to be at the mid-point (i.e. around mid-point region) at 204, then in accordance with the embodiment, the fault location is estimated by (d1+d2)/2 as shown at 212.

[0054] As described above, the method may be implemented by one or more devices associated with the power transmission line such as IEDs (or fault locators), relays or other such power system devices. In accordance with the embodiments shown in FIGS. 1(a) and 1(b), the method is implemented with the fault locator at bus M, or with the fault locator at bus N. Alternately, both the fault locators may implement the method. Here, the fault locator at bus M gets the travelling wave measurements at bus M, and similarly the fault locator at bus N gets the travelling wave measurements at bus N. In this example, the IED can receive a signal(s) from the measurement equipment (here CT as shown in FIG. 1(a), or 1(b)), and obtain measurements therefrom, or the measurement equipment publishes the measurements over a bus (e.g. process bus), and the IED (e.g. subscribed to receive data from such bus) receives the measurements over the bus. The fault locators communicate with each other through standard communication. Thus, the fault locator at bus M sends the travelling wave related information to the fault locator at bus N (and vice versa).

[0055] The steps of the method may be performed by one or more modules. The modules may be implemented with one or more processors. For instance, in the example where the fault locator performs the method, the modules are implemented with the processor of the fault locator (at bus M, or bus N or in each fault locator). Such an embodiment is illustrated in FIG. 3. Here, the device (300) comprises a travelling wave detector (302), faulty half identifier (304) and a fault locator (306). The travelling wave detector obtains the travelling wave parameters as described hereinabove. This module may additionally detect the travelling waves from the measurements, and obtain the parameters accordingly. The faulty half identifier identifies the faulty half or mid-point (region) as having the fault, and the fault locator locates the fault based on the faulty half identification and travelling wave parameters.

[0056] An example where a server (402) performs the method is shown in FIG. 10. In this embodiment, the modules are implemented with the processor of the server. In case the method is implemented in part by IED, and in part by the server, the modules (depending on the step) will be distributed accordingly in the IED and the server. For example, the travelling wave detector may be provided on different fault locators (such as 404, 406), which obtain and communicate the travelling wave parameters to the server, which has the faulty half identifier and the fault locator. The fault location can be communicated to the fault locators for display.

[0057] Thus, the present invention provides two-ended travelling wave based fault location using only arrival times, and line length. This eliminates the need of using line parameters (propagation velocity or wave speed), thereby improving accuracy of fault location.

Parameter Free Traveling Wave Based Fault Location for Power Transmission Lines

Inventors

Cpc classification

Classification Explorer

G01R31/11

PHYSICS

Classification Explorer

G01R31/085

PHYSICS

Classification Explorer

H02H7/265

ELECTRICITY

Classification Explorer

Y04S10/52

GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

Classification Explorer

G01R31/088

PHYSICS

International classification

Classification Explorer

G01R31/08

PHYSICS

Abstract

Claims

Description