T-type power transmission line fault positioning method based on active detection traveling waves

Abstract

The invention relates to a T-type power transmission line fault positioning method based on active detection traveling waves. The method comprises the steps of injection of the active detection traveling waves, judgment of fault branches and calculation of fault positions. According to the calculation method, on the basis of injection of active detection traveling waves, the waveform amplitude of the traveling waves is stable and controllable and can be accurately detected, the fault positioning precision and reliability are effectively improved, and the problem that a traditional fault traveling wave positioning method is difficult to apply when the fault initial phase angle is small and the fault resistance is too large is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fault location in power systems, and particularly relates to a fault location method for a T-shaped transmission line based on actively detected traveling waves. Background Art

[0002] With the economic development of our country, the demand for electricity shows an increasing trend. In order to save the cost of equipment and improve the utilization efficiency of lines, high-voltage heavy-load three-terminal (T-shaped) or multi-terminal transmission lines with three or more terminals often appear. These lines are often connected to large power plants and large systems, and it is required to quickly remove faults on the lines. The fault calculation of T-shaped transmission lines has also attracted more and more attention. Existing fault calculation methods for T-connected transmission lines usually only consider the calculation of fault steady-state quantities and do not involve the calculation of fault traveling waves. Existing fault traveling wave calculation methods usually adopt the grid method, but the fault traveling wave propagation process of T-connected transmission lines is extremely complex, and it is difficult for the grid method to calculate multiple wavefronts of subsequent fault traveling waves. To solve this problem, a precise calculation method for fault traveling waves of T-connected transmission lines has been invented. Summary of the Invention

[0003] The purpose of the present invention is to provide a fault location method for a T-shaped transmission line based on actively detected traveling waves, which solves the problem that it is difficult for the grid method in the prior art to calculate multiple wavefronts of subsequent fault traveling waves.

[0004] The technical solution adopted by the present invention to solve the above problems is to provide a fault location method for a T-shaped transmission line based on actively detected traveling waves, including the following steps:

[0005] Step 1: Set an active detection device, which is composed of a thyristor and a resistor in series, and the whole of the active detection device in parallel with the circuit breaker at the head end of the T-shaped transmission line is in series with the head-end AC power supply; input the parameters of the transmission line and the parameters of the active detection device, and the three terminals of the T-shaped transmission line are respectively defined as the M terminal, the N terminal, and the P terminal;

[0006] Step 2: Inject actively detected traveling waves into the M terminal, the N terminal, and the P terminal at intervals.

[0007] Step 3: Perform phase-mode transformation on the measured voltages at the M terminal, the N terminal, and the P terminal after injecting the detected traveling waves.

[0008] Step 4: Perform wavelet transformation on the modulus voltage traveling waves obtained after phase-mode transformation at the M terminal, the N terminal, and the P terminal, and record the times when the opposite-polarity mode maxima first appear at the M terminal, the N terminal, and the P terminal as t M1 , t N1 , t P1 , and calculate the times when the detected traveling waves at the M terminal, the N terminal, and the P terminal first return to the measurement point as Δt M1, Δt N1 , Δt P1 ;

[0009] Step Five: Divide the lengths of the transmission lines where the M end, N end, and P end are located by the time when the first reflected wave of the detection traveling wave returns to the measurement point at each end, and determine the branch of the transmission line where the fault is located according to the calculation results;

[0010] Step Six: Calculate the propagation speed v of the detection traveling wave according to the ratio of the length of the non-faulty transmission line branch to the time when the first reflected wave of its detection traveling wave returns to the measurement point;

[0011] Step Seven: Calculate the specific location x where the transmission line fault occurs.

[0012] In the first step, the length of the line from the M end of the T-shaped transmission line to the T-junction is denoted as l MT , the length of the line from the N end of the T-shaped transmission line to the T-junction is denoted as l NT , the length of the line from the P end of the T-shaped transmission line to the T-junction is denoted as l PT , the injection time of the detection traveling wave at the M end of the T-shaped transmission line is denoted as t M0 , the injection time of the detection traveling wave at the N end of the T-shaped transmission line is denoted as t N0 , the injection time of the detection traveling wave at the P end of the T-shaped transmission line is denoted as t P0 , the current-limiting resistor configured at the M end of the T-shaped transmission line is denoted as R m , the current-limiting resistor configured at the N end of the T-shaped transmission line is denoted as R n , the current-limiting resistor configured at the P end of the T-shaped transmission line is denoted as R p .

[0013] The method of injecting active detection traveling waves into the M end, N end, and P end is to provide a conduction pulse to one thyristor, and the AC power supply injects active detection traveling waves into the T-shaped transmission line through the active detection device. After an interval of Δt, active detection traveling waves are injected into the next thyristor.

[0014] Perform phase-mode transformation on the measured voltages at the M end, N end, and P end after injecting the detection traveling waves:

[0015]

[0016] where u ax , u bx , u cx is the measured voltage at the x port, and u 1x , u 2x , u 0x are the 1-mode, 2-mode, and 0-mode components of the x port voltage, and x represents M, N, P.

[0017] The wavelet transform is a digital signal processing method, and its calculation formula is as follows:

[0018]

[0019] In the formula: f() is the function to be wavelet-transformed, a is the scale factor; b is the translation factor, a, b ∈ R, a ≠ 0; the function ψ() is the wavelet mother function, usually dbx, symx, fkx, coifx, where x is a natural number from 1 to 10; according to the wavelet transform, the voltage instantaneous amplitude-time curve is obtained, and the moment corresponding to the first reverse maximum mutation point in the instantaneous amplitude-time curve is calibrated. This moment is the moment when the 1-mode component wave head of the active detection traveling wave first reflects back to the measurement point. The moments when the active detection traveling waves at the M terminal, N terminal, and P terminal first reflect back to the measurement point are respectively recorded as t M1 , t N1 , t P1 , and the times when the active detection traveling waves at the M terminal, N terminal, and P terminal first reflect back to the measurement point are respectively: Δt M1 = t M1 - t M0 ; Δ tN1 = t N1 - t N0 ; Δt P1 = t P1 - t P0 .

[0020] The basis for judging the transmission line branch where the fault occurs is as follows:

[0021] If then it can be judged that the fault occurs on the branch MT;

[0022] If then it can be judged that the fault occurs on the branch NT;

[0023] If then it can be judged that the fault occurs on the branch PT.

[0024] The traveling wave propagation speed v is the average value of the speeds calculated by the non-faulty branch line length and time:

[0025] If the fault occurs on the MT branch, then

[0026] If the fault occurs on the NT branch, then

[0027] If the fault occurs on the PT branch, then

[0028] The calculation formula for the specific location x where the fault occurs is:

[0029] If a fault occurs on the MT branch, then

[0030] If a fault occurs on the NT branch, then

[0031] If a fault occurs on the PT branch, then

[0032] Since the actively detected traveling wave in the traveling wave fault location method proposed by the present invention has controllability, it fundamentally solves the defect that the traditional traveling wave method is unavailable due to a low fault initial phase angle, and there is no need for multi-terminal data synchronization and a known traveling wave velocity. Brief Description of the Drawings

[0033] Figure 1 are the voltage signal at the M terminal and the wavelet transform result in the first embodiment of the present invention.

[0034] Figure 2 are the voltage signal at the N terminal and the wavelet transform result in the first embodiment of the present invention.

[0035] Figure 3 are the voltage signal at the P terminal and the wavelet transform result in the first embodiment of the present invention.

[0036] Figure 4 are the voltage signal at the M terminal and the wavelet transform result in the second embodiment of the present invention.

[0037] Figure 5 are the voltage signal at the N terminal and the wavelet transform result in the second embodiment of the present invention.

[0038] Figure 6 are the voltage signal at the P terminal and the wavelet transform result in the second embodiment of the present invention.

[0039] Figure 7 is the structural schematic diagram of the active detection device of the present invention.

[0040] Figure 8 is the schematic diagram of the T-shaped transmission line of the present invention.

[0041] Figure 9 is the structural diagram of the pole tower of the overhead line of the present invention. Detailed Embodiments

[0042] To make the objectives, technical solutions and beneficial effects of the present invention clearer, the following further describes in detail the embodiments of the present invention with reference to the drawings.

[0043] As Figures 7 - 9 shown, the present invention provides a T-shaped transmission line fault location method based on actively detected traveling waves, including the following steps:

[0044] Step 1: Set up an active detection device, which consists of a thyristor and a resistor in series. The whole of the active detection device in parallel with the circuit breaker at the head end of the T-shaped transmission line is in series with the head-end AC power supply; input the parameters of the transmission line and the parameters of the active detection device. The three ends of the T-shaped transmission line are defined as the M end, the N end, and the P end respectively;

[0045] Step 2: Inject active detection traveling waves into the M end, the N end, and the P end at intervals;

[0046] Step 3: Perform phase-mode transformation on the measured voltages at the M end, the N end, and the P end after injecting the detection traveling waves;

[0047] Step 4: Perform wavelet transformation on the modulus voltage traveling waves obtained after phase-mode transformation at the M end, the N end, and the P end. Denote the times when the opposite-polarity mode maxima first appear at the M end, the N end, and the P end as t M1 、t N1 、t P1 , and denote the times when the detection traveling waves at the M end, the N end, and the P end first return to the measurement point as Δt M1 、Δt N1 、Δt P1 respectively;

[0048] Step 5: Divide the lengths of the transmission lines where the M end, the N end, and the P end are located by the times when the detection traveling waves at each end first reflect back to the measurement point respectively, and judge the transmission line branch where the fault is located according to the calculation results;

[0049] Step 6: Calculate the propagation speed v of the detection traveling wave according to the ratio of the length of the non-faulty transmission line branch to the time when its detection traveling wave first reflects back to the measurement point;

[0050] Step 7: Calculate the specific location x where the transmission line fault occurs.

[0051] In Step 1, denote the line length from the M end of the T-shaped transmission line to the T connection point as l MT , denote the line length from the N end of the T-shaped transmission line to the T connection point as l NT , denote the line length from the P end of the T-shaped transmission line to the T connection point as l PT , define the injection time of the detection traveling wave at the M end of the T-shaped transmission line as t M0 , define the injection time of the detection traveling wave at the N end of the T-shaped transmission line as t N0 , define the injection time of the detection traveling wave at the P end of the T-shaped transmission line as t P0 , denote the current-limiting resistor configured at the M end of the T-shaped transmission line as R m , denote the current-limiting resistor configured at the N end of the T-shaped transmission line as R n , denote the current-limiting resistor configured at the P end of the T-shaped transmission line as R p .

[0052] The method of injecting active detection traveling waves into the M terminal, N terminal, and P terminal is to provide a conduction pulse to one thyristor. The AC power supply injects active detection traveling waves into the T-shaped transmission line through the active detection device, and then injects active detection traveling waves into the next thyristor after an interval of Δt.

[0053] Perform phase-mode transformation on the measured voltages at the M terminal, N terminal, and P terminal after injecting the detection traveling waves:

[0054]

[0055] where u ax , u bx , u cx is the measured voltage at the x port, and u 1x , u 2x , u 0x are the 1-mode, 2-mode, and 0-mode components of the x-port voltage, and x represents M, N, P.

[0056] The wavelet transform is a digital signal processing method, and its calculation formula is:

[0057]

[0058] where: f() is the function to be wavelet-transformed, a is the scale factor; b is the translation factor, a, b ∈ R, a ≠ 0; the function ψ() is the wavelet mother function, usually dbx, symx, fkx, coifx, where x is a natural number from 1 to 10; according to the wavelet transform, obtain the voltage instantaneous amplitude-time curve, and calibrate the moment corresponding to the first reverse maximum mutation point in the instantaneous amplitude-time curve. This moment is the moment when the 1-mode component wave head of the active detection traveling wave first reflects back to the measurement point. Record the moments t M1 , t N1 , t P1 when the active detection traveling waves at the M terminal, N terminal, and P terminal first reflect back to the measurement point respectively. The times when the active detection traveling waves at the M terminal, N terminal, and P terminal first reflect back to the measurement point are: Δt M1 = t M1 - t M0 ; Δt N1 = t N1 - t N0 ; Δt P1 = t P1 - t P0 .

[0059] The basis for judging the transmission line branch where the fault is located is as follows:

[0060] If then it can be judged that the fault occurs on the branch MT;

[0061] If it can be determined that the fault occurs on branch NT;

[0062] If it can be determined that the fault occurs on branch PT.

[0063] The traveling wave propagation speed v is the average value of the speeds calculated using the line lengths and times of the non-faulty branches:

[0064] If the fault occurs on branch MT, then

[0065] If the fault occurs on branch NT, then

[0066] If the fault occurs on branch PT, then

[0067] The formula for calculating the specific location x where the fault occurs is:

[0068] If the fault occurs on branch MT, then

[0069] If the fault occurs on branch NT, then

[0070] If the fault occurs on branch PT, then

[0071] Example 1:

[0072] In the embodiment of the present invention, the length l of branch MT in the T-shaped transmission line MT is 210 km, the length l of branch NT NT is 120 km, and the length l of branch PT PT is 300 km; the injection time t of the detected traveling wave at the M end M0 is 1.005 s, the injection time t of the detected traveling wave at the N end N0 is 1.045 s, the injection time t of the detected traveling wave at the P end P0 is 1.085 s, and the time interval Δt = 0.04 s; the values of the current-limiting resistance R configured at the M end, N end, and P end m , R n , R p are all 80 Ω.

[0073] The fault location algorithm of the present invention is implemented with the aid of MATLAB. When a metallic fault occurs at 150 km from the head end of the M-end branch, the waveforms of the 1-mode voltage and the results of wavelet transform at the protection installation locations of the M end, N end, and P end are as Figures 1 - 3 shown.

[0074] Figure 1 The corresponding time of the first reverse mode maximum value in [text] is 1.006 s, and the time Δt for the first reflection of the active detection traveling wave at the M end back to the M end can be calculated M1 = t M1 - t M0 = 1.006 s - 1.005 s = 0.001 s; Figure 2 The corresponding time of the first reverse mode maximum value in [text] is 1.0458 s, and the time Δt for the first reflection of the active detection traveling wave at the N end back to the N end can be calculated N1 = t N1 - t N0 = 1.0458 s - 1.045 s = 0.0008 s; Figure 3 The corresponding time of the first reverse mode maximum value in [text] is 1.087 s, so the time Δt for the first reflection of the active detection traveling wave at the P end back to the P end can be calculated P1 = t P1 - t P0 = 1.087 s - 1.085 s = 0.002 s.

[0075] Calculated It can be judged that the fault occurs on the MT branch. Therefore, the formula and can be used to obtain the fault location as 150 km.

[0076] Example 2:

[0077] When a short - circuit fault with a transition resistance of 150 Ω occurs at 70 km from the head of the N - end branch, the parameters of the transmission line and the structure and parameters of the active detection device remain unchanged. Only the wavelet transform of the mode - 1 voltage at the protection installation points of the M end, N end, and P end needs to be redone, as Figures 4 - 6 shown.

[0078] Figure 4 The corresponding time of the first reverse mode maximum value in [text] is 1.00641 s, and the time Δt for the first reflection of the active detection traveling wave at the M end back to the M end can be calculated M1 = t M1 - t M0 = 1.00641 s - 1.005 s = 0.00141 s; Figure 5 The corresponding time of the first reverse mode maximum value in [text] is 1.04547 s, and the time Δt for the first reflection of the active detection traveling wave at the N end back to the N end can be calculated N1 = t N1 - t N0 = 1.04547 s - 1.045 s = 0.00047 s; Figure 6The corresponding time of the first reverse mode maximum value in [text] is 1.08702 s. Therefore, the time Δt for the first reflection of the traveling wave actively detected at the P end back to the P end can be calculated P1 = t P1 - t P0 = 1.08702 s - 1.085 s = 0.00202 s; Since it is calculated that it can be judged that the fault occurs on the branch NT. Therefore, the formula and can be used to obtain the fault location as 69.901 km.

[0079] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements fall within the scope of the claimed invention.

Claims

1. A fault location method for T-type transmission lines based on actively detecting traveling waves, characterized in that: It includes the following steps: Step 1: Set up an active detection device, which is composed of a thyristor and a resistor in series, and the whole of the active detection device in parallel with the circuit breaker at the head end of the T-shaped transmission line is connected in series with the head-end AC power supply; input the transmission line parameters and the parameters of the active detection device. The three terminals of the T-shaped transmission line are respectively defined as the M terminal, the N terminal, and the P terminal; Step 2: Inject active detection traveling waves into the M terminal, the N terminal, and the P terminal at intervals; Step 3: Perform phase-mode transformation on the measured voltages at the M terminal, the N terminal, and the P terminal after injecting the detection traveling waves; Step 4: Perform wavelet transform on the modulus voltage traveling waves obtained after the mode transformation of the M terminal, N terminal, and P terminal, and record the times when the opposite-polarity mode maxima first appear at the M terminal, N terminal, and P terminal as t M1 , t N1 , t P1 , respectively calculate the times when the detection traveling waves at the M terminal, N terminal, and P terminal first return to the measurement point and record them as Δt M1 , Δt N1 , Δt P1 ; Step 5: Divide the lengths of the transmission lines where the M terminal, the N terminal, and the P terminal are located by the time when the first reflection of the detection traveling wave corresponding to each terminal returns to the measurement point respectively, and judge the transmission line branch where the fault is located according to the calculation results; Step 6: Calculate the propagation speed v of the detection traveling wave according to the ratio of the length of the non-fault transmission line branch to the time when its detection traveling wave first reflects back to the measurement point; Step 7: Calculate the specific location x where the transmission line fault occurs.

2. The T-type transmission line fault location method based on actively detecting traveling waves according to claim 1, characterized in that: In the first step, the line length from the M end of the T-shaped transmission line to the T-joint is denoted as l MT , the line length from the N end of the T-shaped transmission line to the T-joint is denoted as l NT , the line length from the P end of the T-shaped transmission line to the T-joint is denoted as l PT , the injection time of the detection traveling wave at the M end of the T-shaped transmission line is denoted as t M0 , the injection time of the detection traveling wave at the N end of the T-shaped transmission line is denoted as t N0 , the injection time of the detection traveling wave at the P end of the T-shaped transmission line is denoted as t P0 , the current-limiting resistor configured at the M end of the T-shaped transmission line is denoted as R m , the current-limiting resistor configured at the N end of the T-shaped transmission line is denoted as R n , the current-limiting resistor configured at the P end of the T-shaped transmission line is denoted as R p .

3. A T-type transmission line fault location method based on active detection traveling wave according to claim 1, characterized in that: The method of injecting active detection traveling waves into the M terminal, the N terminal, and the P terminal is to provide a conduction pulse to the thyristor at one end, and the AC power supply injects active detection traveling waves into the T-shaped transmission line through the active detection device. After an interval time Δt, inject active detection traveling waves into the thyristor at the next end.

4. A T-type transmission line fault location method based on actively detecting traveling waves according to claim 1, characterized in that: Perform phase-mode transformation on the measured voltages at the M terminal, the N terminal, and the P terminal after injecting the detection traveling waves: where u ax , u bx , u cx is the measured voltage at the x port, and u 1x , u 2x , u 0x are the 1-mode, 2-mode, and 0-mode components of the x-port voltage, and x represents M, N, P.

5. A T-type transmission line fault location method based on active detection of traveling waves according to claim 1, characterized in that: The wavelet transform is a digital signal processing method, and its calculation formula is: where: f() is the function to be wavelet-transformed, a is the scaling factor; b is the translation factor, a, b ∈ R, a ≠ 0; the function ψ() is the mother wavelet function, usually dbx, symx, fkx, coifx, where x is a natural number from 1 to 10; according to the wavelet transform, the voltage instantaneous amplitude-time curve is obtained, and the time corresponding to the occurrence of the first reverse maximum mutation point in the instantaneous amplitude-time curve is calibrated. This time is the time when the wavefront of the 1-mode component of the active detection traveling wave first reflects back to the measurement point. The times when the active detection traveling waves at the M terminal, N terminal, and P terminal first reflect back to the measurement point are respectively recorded as t M1 , t N1 , t P1 , and the times when the active detection traveling waves at the M terminal, N terminal, and P terminal first reflect back to the measurement point are respectively: Δt M1 = t M1 - t M0 ; Δt N1 = t N1 - t N0 ; Δt P1 = t P1 - t P0 .

6. The method for fault location of a T-shaped transmission line based on actively detecting traveling waves according to claim 1, wherein: The basis for judging the transmission line branch where the fault is located is as follows: If it can be determined that the fault occurs on branch MT; If it can be determined that the fault occurs on branch NT; If it can be determined that the fault occurs on the branch PT.

7. A fault location method for a T-shaped transmission line based on actively detecting traveling waves according to claim 1, characterized in that: The traveling wave propagation speed v is the average value of the speeds calculated by the length and time of the non-fault branch line: If a fault occurs on the MT branch, then If a fault occurs on the NT branch, then If a fault occurs on the PT branch, then 8. A fault location method for a T-shaped transmission line based on actively detecting traveling waves according to claim 1, characterized in that: The calculation formula for the specific location x where the fault occurs is: If a fault occurs on the MT branch, then If a fault occurs on the NT branch, then If a fault occurs on the PT branch, then

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