High-voltage transmission line fault traveling wave fault location method

Abstract

The invention relates to a high-voltage power transmission line fault traveling wave distance measurement method, which comprises the following steps of: arranging a plurality of data acquisition units on a power transmission line, and acquiring and processing fault voltage and fault current signals of each detection point of the power transmission line; analyzing the transmission process of the fault transient traveling wave in the high-voltage transmission line, and establishing a mathematical model of the voltage traveling wave and the current traveling wave; carrying out distance measurement on a high-voltage transmission line fault by using a double-end traveling wave distance measurement algorithm, and constructing a traveling wave distance measurement model; and improving a double-end traveling wave distance measurement algorithm by using wavelet transform, and determining the fault position of the high-voltage transmission line. When the power transmission line breaks down, the detection system can quickly and accurately detect and respond to a fault section, the parallel operation capability of the whole power grid and the stability of local power supply are prevented from being influenced, important technical guarantee is provided for safe and stable operation of the power grid, the adaptability of an operation strategy is improved, and the system operation efficiency is improved. The economic benefit is obvious.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-voltage transmission line fault detection, and particularly relates to a method for fault traveling wave ranging of high-voltage transmission lines. Background Art

[0002] Since people's daily life and production increasingly rely on electricity, the scale and complexity of the power system have gradually increased, which has imposed higher requirements on the operation quality of the power supply system. To ensure the safe and stable operation of the power system, transmission line fault diagnosis technology has become increasingly important. At present, to ensure the normal operation of transmission lines, workers need to repeatedly inspect the working conditions of high-voltage transmission lines in various regions throughout the day, which will cost a large amount of manpower and material resources. At the same time, once a fault occurs in the high-voltage transmission line, it will affect enterprise production and cause great economic losses. To save costs and reduce the harm caused by faults, many protection measures must be taken for high-voltage transmission lines.

[0003] At present, the research content of high-voltage transmission line fault diagnosis mainly includes fault classification analysis and power grid load prediction analysis. Among them, the degree of intelligence in the process of fault classification analysis is not high enough, the automation level of troubleshooting and handling of high-voltage transmission line faults is low. At the moment of fault occurrence, the monitoring system cannot accurately analyze the fault type and locate the problem. It is necessary to conduct fault troubleshooting and maintenance in sequence. This method can no longer meet the daily maintenance needs in the information society. With the improvement of the intelligence level of the power system, higher requirements are also placed on its safety. Automatically locating the fault type has become the current development trend. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art, and provide a method for fault traveling wave ranging of high-voltage transmission lines, which can effectively reduce the burden on maintenance personnel by improving the intelligence and automation level of the power system, and improve the reliability and economic benefits of the entire power system.

[0005] The technical solution adopted by the present invention is as follows: A method for fault traveling wave ranging of high-voltage transmission lines includes the following steps:

[0006] S1: Set several data acquisition units on the transmission line to collect and process the fault voltage and fault current signals at each detection point of the power line;

[0007] S2: Analyze the transmission process of the fault transient traveling wave on the high-voltage transmission line, and establish a mathematical model of voltage traveling wave and current traveling wave;

[0008] S3: Use the double-end traveling wave ranging algorithm to measure the distance of the high-voltage transmission line fault, and construct a traveling wave ranging model;

[0009] S4: Improve the double - ended traveling - wave ranging algorithm using wavelet transform to determine the fault location of high - voltage transmission lines.

[0010] Specifically, in step S2, assume that the voltage and current at a certain point on line MN are u and i respectively. After passing through a section of dx, the voltage and current become u + du and i + di respectively. Among them, the voltage increment du is generated by the distributed inductance Ldu, and the current increment di is generated by the distributed capacitance Cdx. According to Kirchhoff's law, it is easy to obtain the relationship between the traveling - wave voltage, current and wire parameters:

[0011]

[0012] In the formula, L represents the inductance per unit length of the line; C represents the capacitance per unit length of the line; u represents the voltage at a distance x from the fault point; i represents the current at a distance x from the fault point.

[0013] The formula is further transformed into:

[0014]

[0015] When a metallic fault occurs at point F on line MN, the particular solution of the above equation can be obtained, and the voltage traveling - wave and current traveling - wave at both ends of MN can be expressed as follows:

[0016] u M (t)= - e(t - t M ) - f M e(t - t M )+f M e(t - 3t M )+f M 2 e(t - 3t M )+…

[0017]

[0018] u N (t)= - e(t - t N ) - f N e(t - t N )+f N e(t - 3t N )+f N 2 e(t - 3t N )+…

[0019]

[0020] In the formula: is the wave impedance; the subscripts M and N represent the M - end and N - end of the line respectively; t M 、t Nis the time taken for the traveling wave to travel from the fault point to the busbars at the M - end and N - end; f M and f N are the reflection coefficients of the traveling wave at the busbars of the M - end and N - end (usually negative real numbers); -e(t) is the voltage of the additional voltage source in the fault network.

[0021] Specifically, in step S3, the double - ended traveling - wave ranging algorithm calculates the distance from the fault point to the busbar measurement end by using the arrival times of the fault transient traveling wave at the measurement ends M and N of the busbar and combining the traveling - wave velocity. By measuring the arrival times of the initial fault traveling wave and the reflected wave from the fault point at the measurement busbars M and N (i.e., t M and t N and t F ) and combining the propagation velocity of the fault transient traveling wave in the transmission line to achieve fault ranging; L is the length of the transmission line. Assuming that the direction of the fault transient traveling wave from the fault point to the measurement busbar N is square, the fault - ranging equation set for the transmission line is:

[0022]

[0023] Solving the equations gives:

[0024]

[0025] When using the double - ended traveling - wave ranging algorithm to achieve fault ranging, there is no need to consider the reflection and refraction phenomena of the fault transient traveling wave. Just by detecting the arrival time of the initial wavefront of the fault transient traveling wave at the busbar measurement end and the traveling - wave velocity, the line fault ranging can be achieved.

[0026] Specifically, in step S4, the wavelet transform of the signal represents the signal using the basic wavelet function. Let f(t) be the fault transient traveling wave of the transmission line, a be the scale factor, and b be the displacement factor. If the function satisfies the admissibility condition:

[0027]

[0028] Then the wavelet transform of f(t) can be defined as:

[0029]

[0030] The kernel function of the transform is:

[0031]

[0032] In the formula, a > 0, b ∈ R, then is called the basic wavelet or mother wavelet, and the mean value of the basic wavelet is zero, that is, as shown in the following formula:

[0033]

[0034] Advantages of the present invention: The implementation of the present invention can detect high-voltage transmission line faults at different locations and with different durations. When a fault occurs in a power transmission line, the detection system can respond quickly and accurately to the fault section, preventing the impact on the ability of the entire power grid to operate in parallel and the stability of local power supply, providing an important technical guarantee for the safe and stable operation of the power grid, improving the adaptability of operation strategies, enhancing the system operation efficiency, and having significant economic benefits. Brief Description of the Drawings

[0035] Figure 1 It is the equivalent power diagram of the faulty power system of the present invention;

[0036] Figure 2 It is the distributed parameter equivalent circuit diagram of the fault traveling wave propagation in a single-phase wire of the present invention;

[0037] Figure 3 It is the schematic diagram of the double-ended traveling wave ranging principle of the present invention;

[0038] Figure 4 It is the schematic diagram of the transient traveling waves detected at the measuring buses M and N at both ends of the present invention;

[0039] Figure 5 It is the curve diagram of the wavelet transform coefficients of the signal estimated by the semi-soft threshold method of the present invention;

[0040] Figure 6 It is the curve diagram of the wavelet transform coefficients of the signal estimated by the improved semi-soft threshold method of the present invention;

[0041] Figure 7 It is the flow chart of the double-ended traveling wave ranging system of the present invention. Detailed Embodiment

[0042] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. The following will be specifically described in conjunction with the embodiments.

[0043] As Figure 1-7 shown, the present invention includes the following steps:

[0044] S1: Set a number of data acquisition units on the transmission line to collect and process the fault voltage and fault current signals at each detection point of the power line.

[0045] The specific process is as follows: In step S1, the fault voltage and current signals at each detection point are collected through a number of fault detection devices installed on the transmission line to obtain the fault transient voltage and current signals.

[0046] S2: Analyze the transmission process of the fault transient traveling wave on the high-voltage transmission line, and establish the mathematical models of the voltage traveling wave and the current traveling wave. The specific process is as follows: In the said step S2,

[0047] As Figure 1 shown, if the fault occurs at point F on the line segment MN, according to the superposition principle, the power system after the fault can be equivalent to the superposition of the normal operation network and the fault network. In the fault network, the additional power source is a voltage source, and its value is equal to the voltage at the fault point F before the fault. Under the action of the additional voltage source at the fault point, the additional power source will transfer its voltage to other non-fault nodes. Since there are energy storage elements such as inductance and capacitance in the line distributed parameters, the inductance current and the capacitance voltage cannot change suddenly, and they require a charging process, which is the process of the formation and propagation of the fault traveling wave.

[0048] Figure 1 (a) is the power system with a fault, Figure 1 (b) is Figure 1 the equivalent circuit of (a), and Figure 1 (b) can be expressed as the superposition of the normal operation network ( Figure 1 (as shown in (c)) and the fault network ( Figure 1 (as shown in (d)). Figure 1 where e f is the voltage of the additional power source at the fault point.

[0049] The high-voltage power transmission and distribution line has the characteristics of distributed parameters. When the voltage level of the line is not high and the distance is not long, the fault traveling wave has a fixed propagation speed close to the speed of light on the line. When the frequency is not high, its wavelength will be much larger than the line length. At this time, the distributed parameter circuit can be replaced by a lumped parameter equivalent circuit, thus greatly simplifying the analysis and calculation of the transmission line. When the line distributed resistance and distributed conductance are ignored, the distributed parameter equivalent circuit during the propagation process of the fault traveling wave in a single-phase wire is as Figure 2 shown.

[0050] Assume that the voltage and current at a certain point on the line MN are u and i respectively. After passing through the dx segment, the voltage and current are u + du and i + di respectively. Among them, the voltage increment du is generated by the distributed inductance Ldu, and the current increment di is generated by the distributed capacitance Cdx. According to Kirchhoff's law, the relationship between the traveling wave voltage, current and the wire parameters can be easily obtained:

[0051]

[0052] In the formula, L represents the inductance per unit length of the line; C represents the capacitance per unit length of the line; u represents the voltage at a distance x from the fault point; i represents the current at a distance x from the fault point;

[0053] The formula is further transformed into:

[0054]

[0055] When a metallic fault occurs at point F on line MN, the particular solution of the above equation can be obtained, and the voltage traveling wave and current traveling wave at both ends of MN can be expressed as follows:

[0056] u M (t) = -e(t - t M ) - f M e(t - t M ) + f M e(t - 3t M ) + f M 2 e(t - 3t M ) + … (3)

[0057]

[0058] u N (t) = -e(t - t N ) - f N e(t - t N ) + f N e(t - 3t N ) + f N 2 e(t - 3t N ) + … (5)

[0059]

[0060] In the formula: is the wave impedance; the subscripts M and N respectively represent the M end and N end of the line; t M , t N are the times taken for the traveling wave to travel from the fault point to the busbars at the M end and N end; f M , f N are the reflection coefficients of the traveling wave at the busbars at the M end and N end (generally negative real numbers); -e(t) is the voltage of the additional voltage source in the fault network.

[0061] The first two terms in formulas (4) and (6) represent the first wavefront component of the current traveling wave moving towards the busbars generated by the fault point. The third and fourth terms represent that the initial traveling wave is reflected at the busbar and then returns to the fault point, and after total reflection at the fault point, it moves to the busbar again as the second wavefront component, with a time interval of 2t M , 2t N .

[0062] It can also be seen from equations (3) to (6) that when the first traveling wave head after a fault arrives at the bus, the current traveling wave and the voltage traveling wave behave differently. Due to the reflection coefficient f M (f N ) being a negative real number, at t = t M (t = t N ), the forward and backward traveling waves of the current traveling wave reinforce each other, while the voltage traveling wave weakens. Therefore, using the current traveling wave to implement two-terminal traveling wave ranging is more sensitive than using the voltage traveling wave.

[0063] S3: Use the two-terminal traveling wave ranging algorithm to measure the fault of the high-voltage transmission line and construct a traveling wave ranging model. The specific process is as follows: In the step S3,

[0064] When a fault occurs in the high-voltage transmission line, the fault usually shows a sudden change in the traveling wave signal. Therefore, analyzing the singularity of the fault transient traveling wave signal is beneficial to determining the mutation point of the traveling wave signal, and thus determining the sampling sequence corresponding to the mutation point. Since wavelet transform has the characteristic of locally depicting signal mutations and can very effectively analyze the singularity of the fault transient traveling wave signal and accurately determine the position of the signal mutation point, it is relatively effective to use the local modulus maximum value after wavelet transform of the signal to analyze the singularity of the fault transient traveling wave signal.

[0065] The Lipschitz exponent α is used to describe the singularity of the fault transient traveling wave signal. Let n be a non-negative integer and satisfy n < α ≤ n + 1. If there are two constants A and h0 > 0, and there exists an nth-degree polynomial P n (h), such that for any h ≤ h0, the following is satisfied:

[0066] |f(x0 + h) - P n (h)| ≤ A|h| α (7)

[0067] Then f(x) is said to be Lipschitz α at the point x0. If the Lipschitz α exponent increases continuously, the fault transient traveling wave signal becomes smoother; if the Lipschitz α exponent decreases continuously, the singularity of the fault transient traveling wave signal becomes greater.

[0068] The fault transient traveling wave signal has singularity at its mutation point, and the local modulus maximum points after its wavelet transform correspond one-to-one with the mutation points of the traveling wave signal. Therefore, the position of the mutation point of the traveling wave signal can be determined using the local modulus maximum value of the fault transient traveling wave. Let the wavelet function be continuous and differentiable, and have nth-order vanishing moments (n ∈ Z + ), f(x) ∈ L 2(R), the function f(x) (fault transient traveling wave signal) has a Lipschitz exponent α at x0. If and only if there exists a constant K such that (where Bx0 is any open neighborhood of x0), the wavelet transform of the function f(x) must satisfy the following equation:

[0069] |Wf(s,x)| ≤ Ks α (8)

[0070] If x0 is a local mutation point of the function f(x), then x0 is called a local extreme point of the wavelet transform of the function f(x) at scale s. It can be seen from formula (8) that: if α > 0 and gradually decreases as the scale s decreases, the modulus maximum value of the signal function f(x) after wavelet transform continuously decreases; if α < 0 and gradually increases as the scale s increases, the modulus maximum value of the signal function f(x) after wavelet transform continuously increases.

[0071] As Figure 3 shown, the double - ended traveling wave ranging algorithm uses the arrival times of the fault transient traveling wave at the bus measurement ends M and N and combines the traveling wave velocity to calculate the distance from the fault point to the bus measurement end. By measuring the arrival times of the initial fault traveling wave and the reflected wave from the fault point at the measurement buses M and N respectively (i.e., t M 、t N 、t F ) and combining the propagation wave velocity of the fault transient traveling wave in the transmission line to achieve fault ranging; L is the length of the transmission line. Assuming that the direction of the fault transient traveling wave from the fault point to the measurement bus N is square, the fault transient traveling wave signals measured at both ends of the line are as Figure 4 shown:

[0072] The fault ranging equation set for the transmission line is obtained as:

[0073]

[0074] Solving the equation set gives:

[0075]

[0076] When using the double - ended traveling wave ranging algorithm to achieve fault ranging, it is not necessary to consider the reflection and refraction phenomena of the fault transient traveling wave. Just detecting the arrival time of the initial wavefront of the fault transient traveling wave at the bus measurement end and the traveling wave velocity can achieve line fault ranging.

[0077] S4: Improve the double - ended traveling wave ranging algorithm using wavelet transform to determine the fault location of the high - voltage transmission line. The specific process is as follows: In the step S4,

[0078] The wavelet transform of a signal is to represent the signal using a basis wavelet function. Let f(t) be the fault transient traveling wave on a transmission line, a be the scale factor, and b be the displacement factor. If the function satisfies the admissibility condition:

[0079]

[0080] Then the wavelet transform of f(t) can be defined as:

[0081]

[0082] The kernel function of the transform is:

[0083]

[0084] In the formula, a > 0, b ∈ R, then is called the basic wavelet or mother wavelet, and the mean value of the basic wavelet is zero, that is, as shown in the following formula:

[0085]

[0086] Since the span of high-voltage transmission lines is relatively large and the environment through which they pass is complex and changeable, high-voltage transmission lines are vulnerable to natural factors during actual operation. When the fault transient traveling wave propagates on an extra-high voltage transmission line, it is easily affected by various noises. Therefore, the fault transient traveling wave signal detected at the bus measurement end contains a lot of noise and is difficult to be used for analysis and fault location. In order to reduce the influence of noise on the accuracy of transmission line fault location, it is necessary to perform noise reduction processing on the detected fault transient traveling wave signal.

[0087] A noise reduction method based on semi-soft threshold is proposed. When using this method to estimate the threshold of the wavelet transform coefficients of a signal, its definition is:

[0088]

[0089] In the formula, T1 is the selected lower threshold and T2 is the selected upper threshold.

[0090] From formula 15, the curve of the wavelet transform coefficients of the signal f(t) estimated by the semi-soft threshold method can be drawn, as Figure 5 shown.

[0091] When using the semi-soft threshold method to estimate the wavelet transform coefficients of the signal f(t), two different thresholds (T1, T2) must be selected, and the computational amount is relatively large, making it difficult to promote and apply.

[0092] Aiming at the deficiencies of the semi-soft threshold noise reduction method, by analyzing its estimation principle, a new improved scheme is adopted, and the improved noise reduction method is used for the noise reduction of the fault transient traveling wave signal, achieving good noise reduction effects.

[0093] If a scale parameter a (0 ≤ a ≤ 1) is introduced into Equation (15), then Equation (15) can be rewritten in the following form:

[0094]

[0095] If W j,k > 0, then the above Equation (16) can be arranged as:

[0096]

[0097] If is regarded as a whole and squared, then the above Equation (15) can be transformed into the following form:

[0098]

[0099] It can be obtained from Equation (18) that: after the wavelet transform coefficients of the signal f(t) are estimated by the improved semi-soft threshold method, its curve graph is as Figure 6 shown.

[0100] From Figure 6 it can be seen that: when using the improved semi-soft threshold method to estimate the wavelet transform coefficients of the signal f(t), only one threshold is needed, which is beneficial to signal denoising and overcomes the deficiencies of the above semi-soft threshold denoising method.

[0101] From the above analysis and combining Equation (18) and Figure 6 it can be obtained that the steps of this denoising method are as follows: ①Perform wavelet transform on the measured signal f(t) to obtain its wavelet transform coefficients; ②Select a threshold T such that it is just greater than the maximum value of the wavelet transform coefficients corresponding to the noise, and use the improved semi-soft threshold denoising method to perform denoising processing on the measured signal f(t); ③Perform wavelet inverse transform operation on the denoised signal to reconstruct the denoised signal.

[0102] When using wavelet transform to improve the double-terminal traveling wave ranging algorithm, it can be seen from the traditional double-terminal traveling wave ranging formula (10) that: the traditional double-terminal traveling wave ranging accuracy is related to both the moment when the initial wave head of the fault transient reaches the bus measurement end and the traveling wave velocity. Since using the double-terminal traveling wave ranging algorithm for line fault ranging is more accurate than using the single-terminal traveling wave ranging algorithm to achieve fault ranging and meets the requirements of modern power systems for fault ranging accuracy, the double-terminal traveling wave ranging algorithm is used to achieve high-voltage transmission line fault ranging. In order to eliminate the influence of the traveling wave velocity on the accuracy of transmission line fault ranging, the traditional double-terminal traveling wave ranging algorithm is improved to improve the fault ranging accuracy. When a fault occurs in the transmission line, assuming its absolute time is t0, then according to Figure 3 the following ranging equations can be listed:

[0103]

[0104] The solution of the system of equations is:

[0105]

[0106] It can be seen from formula (20) that the improved double - ended traveling - wave ranging algorithm is independent of the propagation wave velocity of the fault transient traveling wave, eliminates the influence of the traveling - wave velocity on the accuracy of line fault ranging, and is conducive to improving the accuracy of transmission - line fault ranging. Since the accuracy of the improved double - ended traveling - wave ranging only relates to the arrival time of the fault transient traveling - wave signal at the bus measurement end, it is of great significance to accurately determine the arrival time of the fault transient traveling - wave signal at the bus measurement end.

[0107] From the above analysis, the flowchart of the double - ended traveling - wave ranging system can be designed, as Figure 7 shown.

[0108] In order to accurately determine the arrival time of the fault transient traveling - wave signal at the bus measurement end, the wavelet analysis method is introduced to perform singularity analysis and modulus maximum analysis on the fault transient traveling - wave signal, and the corresponding time at the mutation point of the fault transient traveling - wave signal is calculated according to the sampling sequence corresponding to the modulus maximum, so as to substitute it into the ranging formula (18) to obtain the distance from the fault point to the bus measurement end.

[0109] The present invention first, according to the superposition principle, details the transient process when a fault occurs in an extra - high - voltage transmission line, and respectively establishes mathematical models of fault transient voltage traveling waves and current traveling waves based on Kirchhoff's voltage law and current law, as well as in combination with the equivalent - circuit model of the extra - high - voltage transmission line. According to the modulus - maximum theory of wavelet transform, singularity analysis is performed on the fault transient traveling - wave signals extracted at the bus measurement ends M and N. Through mathematical theoretical derivation, the ranging formula of the double - ended traveling - wave ranging algorithm is obtained, and a traveling - wave ranging mathematical model is established. By studying the principle of threshold denoising and in combination with the characteristics of the wavelet - transform coefficient curve of the signal, a new improved scheme is adopted, and through mathematical theoretical derivation, the mathematical expression of the improved semi - soft - threshold denoising method is obtained. The improved denoising method is used to denoise the signal, and the denoising result is very obvious and effective, and at the same time, it provides favorable conditions for realizing fault ranging of extra - high - voltage transmission lines. Finally, on the basis of wavelet denoising, the wavelet analysis method is introduced into fault ranging. By improving the traditional traveling - wave ranging algorithm, the corresponding time is calculated using the modulus - maximum sampling sequence of the fault transient traveling - wave signal at the mutation point, and then, according to the fault - ranging algorithm, the distance from the fault point to the bus measurement end is calculated.

[0110] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims concerned.

Claims

1. A traveling wave fault location method for high-voltage transmission lines, characterized in that, It includes the following steps: S1: Set several data acquisition units on the transmission line to collect and process the fault voltage and fault current signals at each detection point of the power line; S2: Analyze the transmission process of the fault transient traveling wave on the high-voltage transmission line and establish the mathematical models of the voltage traveling wave and the current traveling wave; S3: Use the double-ended traveling wave ranging algorithm to measure the distance of the fault on the high-voltage transmission line and construct a traveling wave ranging model; S4: Use wavelet transform to improve the double-ended traveling wave ranging algorithm and determine the fault location of the high-voltage transmission line.

2. A method for fault traveling wave ranging of a high-voltage transmission line according to claim 1, characterized in that: In step S2, assume that the voltage and current at a certain point on line MN are u and i respectively. After passing through section dx, the voltage and current are u + du and i + di respectively. Among them, the voltage increment du is generated by the distributed inductance Ldu, and the current increment di is generated by the distributed capacitance Cdx. According to Kirchhoff's law, the relationship between the traveling wave voltage, current and wire parameters can be easily obtained: Where, L represents the inductance per unit length of the line; C represents the capacitance per unit length of the line; u represents the voltage at a distance x from the fault point; i represents the current at a distance x from the fault point; The formula is further transformed into: When a metallic fault occurs at point F on line MN, the particular solution of the above equation can be obtained, and the voltage traveling wave and current traveling wave at both ends of MN can be expressed as follows: Wherein: is the wave impedance; the subscripts M and N respectively represent the M end and the N end of the line; t M , t N are the times taken for the traveling wave to travel from the fault point to the busbars at the M end and the N end; f M , f N are the reflection coefficients of the traveling wave at the busbars at the M end and the N end; -e(t) is the voltage of the additional voltage source in the fault network.

3. A method for traveling wave fault location of high-voltage transmission lines according to claim 1, characterized in that: In the step S3, the double-ended traveling wave ranging algorithm calculates the distance from the fault point to the bus measurement end by using the moments when the fault transient traveling wave reaches the bus measurement ends M and N and combining the traveling wave velocity. By measuring the moments when the initial fault traveling wave and the reflected wave from the fault point reach the measurement buses M and N respectively (i.e., t M , t N , t F ) and combining the propagation wave velocity of the fault transient traveling wave in the transmission line to achieve fault ranging; L is the length of the transmission line. Assuming that the direction of the fault transient traveling wave from the fault point to the measurement bus N is square, the fault ranging equation set of the transmission line is obtained as follows: Solve the equations to get: When using the double-ended traveling wave ranging algorithm to achieve fault ranging, it is not necessary to consider the reflection and refraction phenomena of the fault transient traveling wave. Just detect the moment when the initial wavefront of the fault transient traveling wave arrives at the bus measurement end and the traveling wave velocity, and the line fault ranging can be achieved.

4. A method for fault traveling wave ranging of a high-voltage transmission line according to claim 1, characterized in that In the step S4, the wavelet transform of the signal is to represent the signal by using the basic wavelet function. Let f(t) be the fault transient traveling wave of the transmission line, a be the scale factor, and b be the displacement factor. If the function satisfies the admissibility condition: Then the wavelet transform of f(t) can be defined as: The kernel function of the transform is: where \(a\gt0\), \(b\in R\), then is called the basic wavelet or mother wavelet, and the mean value of the basic wavelet is zero, as shown in the following formula:

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