Fault Location Method and System for Multi-Branch Lines in Distribution Networks Based on Time Domain Difference

Abstract

The present invention relates to the technical field of distribution network fault location, and provides a distribution network multi-branch line fault location method and system based on time-domain difference. The distribution network multi-branch line fault location method based on time-domain difference includes obtaining the fault traveling wave line-mode component based on the fault traveling wave data and discretizing it; performing time-domain difference operation on the discretized fault voltage traveling wave line-mode component to eliminate the sine component and obtain the fault traveling wave line-mode component signal; constructing an objective function to optimize the fault traveling wave line-mode component signal and determine the time-domain position of the fault traveling wave wavefront to calibrate the arrival time of the fault traveling wave wavefront; if it is a main line fault, based on the basic parameters and fault sections of the fault line, combined with the arrival time of the fault traveling wave wavefront, establish the first fault point reflection wave timing constraint to determine the arrival time of the fault point reflection wavefront and thus determine the fault point location. It improves the calculation speed and reliability of fault location and reduces the cost.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution network fault location, and in particular to a distribution network multi-branch line fault location method and system based on time domain difference. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Distribution network fault location technology is a key technology to improve the reliability of distribution network power supply, reduce operation and maintenance costs, and support the intelligent and digital transformation of power grids. The distribution network has the characteristics of many points and wide areas, and many branch lines. After a fault occurs, the fault propagation law is relatively complex, which makes it difficult to locate. The traditional wave head calibration method has high calculation complexity and poor adaptability. At the same time, the existing fault location method often requires the configuration of multiple positioning terminals, which has high economic costs and is difficult to implement, making it inconvenient for large-scale promotion and application.

[0004] Currently, there are several ways to locate faults:

[0005] (1) By performing multi-resolution wavelet decomposition on the zero-sequence voltage signal, extracting the fundamental band characteristics and calculating the signal transformation before and after the fault, high-resistance fault detection is achieved. This method has a certain ability to resist noise and harmonic interference, but it cannot accurately locate the fault location.

[0006] (2) By performing static wavelet transform on the line mode current signal, unlike the traditional discrete wavelet transform, the static wavelet transform achieves time invariance through redundant filtering. This method avoids the influence of signal time shift on the transformation result and is more suitable for the accurate calibration of the traveling wave head, but the positioning effect still depends on the selection of the wavelet basis function.

[0007] (3) Use complementary set empirical mode decomposition to reduce modal aliasing, and use the improved Teager energy operator to enhance the mutation characteristics of the traveling wave signal, or filter out low-frequency interference through extreme symmetric mode decomposition, and use TEO to highlight the mutation characteristics of the traveling wave head. These improved methods significantly enhance the ability to identify the mutation characteristics of the traveling wave head and improve the positioning accuracy, but there are still problems such as strong parameter sensitivity and the need to improve computational efficiency.

[0008] (4) By establishing a fault traveling wave propagation path matrix, the fault location is realized based on the time difference of traveling wave transmission at multiple endpoints. In practical applications, the positioning process of this method often requires multiple complex steps, which makes the calculation amount extremely large and the equipment cost is high.

[0009] (5) By analyzing the matrix differences before and after the fault, a fault branch determination matrix is constructed, and the zero-mode and line-mode components are used to optimize the device configuration, reducing the engineering cost. However, this method has limitations: the zero-mode component is only applicable to ground faults and attenuates rapidly, affecting the positioning reliability.

[0010] (6) A single-ended positioning method based on panoramic extraction of fault waveform features using deep learning is adopted. This method breaks through the limitations of traditional multi-terminal detection. However, the performance of the deep learning model is limited by the quality and scale of the training samples, and its engineering practicability still needs to be further verified. Summary of the Invention

[0011] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a method and system for fault location of multi-branch lines in a distribution network based on time-domain difference. The present invention represents the fault traveling wave as an exponentially decaying component superimposed on a sine wave within a time window. By performing time-domain difference operation on the line-mode component of the fault voltage traveling wave, the sine component is eliminated, and the fault traveling wave is represented in the form of a pulse to calibrate the arrival time of the fault traveling wave head. After determining the arrival time of the initial fault traveling wave head, the arrival time sequence relationship of the fault reflected traveling wave head is established, and the arrival time of the fault traveling wave reflected wave is identified, realizing the fault location of multi-branch lines in the distribution network with only traveling wave acquisition devices equipped on the main line, improving the calculation speed and reliability of fault location. Therefore, the present invention realizes improving the accuracy of fault location of multi-branch lines in the distribution network while reducing the measurement devices, having significant economic value and social benefits.

[0012] In order to achieve the above object, the present invention adopts the following technical solutions:

[0013] The first aspect of the present invention provides a method for fault location of multi-branch lines in a distribution network based on time-domain difference.

[0014] A method for fault location of multi-branch lines in a distribution network based on time-domain difference includes:

[0015] Obtain the basic parameters of the fault line, the fault section, and the fault traveling wave data at both ends of the line; the basic parameters include wave impedance, inductance per unit length, and capacitance;

[0016] Based on the fault traveling wave data at both ends of the line, obtain the line-mode component of the fault traveling wave and perform discretization; the line-mode component of the fault traveling wave includes a sine component and an exponentially decaying component; perform time-domain difference operation on the discretized line-mode component of the fault voltage traveling wave to eliminate the sine component and obtain the line-mode component signal of the fault traveling wave;

[0017] Construct an objective function, optimize the line-mode component signal of the fault traveling wave, and determine the time-domain positions of the fault traveling wave heads at both ends of the line to calibrate the arrival times of the fault traveling wave heads at both ends of the line;

[0018] If it is a main line fault, based on the basic parameters of the faulty line and the fault section, and combining the arrival times of the fault traveling wave heads at both ends of the line, a first time sequence constraint for the reflected wave at the fault point is established to determine the arrival times of the reflected wave heads at both ends of the line at the fault point; based on the arrival times of the reflected wave heads at both ends of the line at the fault point, the fault point location is determined.

[0019] If it is a branch line fault, determine the arrival times of the initial fault traveling wave, the reflected wave at the fault point, and the reflected wave at the opposite busbar at both ends of the line respectively; within the sampling time window, according to the second time sequence constraint for the reflected wave at the fault point, and combining the polarity differences between the reflected wave at the fault point and the reflected wave at the opposite busbar, determine the first arrival times of the reflected wave at the fault point and the reflected wave at the opposite busbar at both ends of the line to determine the fault point location.

[0020] Furthermore, the objective function is expressed by the following formula:

[0021]

[0022] In the formula, and are respectively and discrete sampling values, , represent the line mode component signals of the fault traveling wave, k is the discrete sampling point index, and λ represents the best fitting parameter.

[0023] Furthermore, the first time sequence constraint for the reflected wave at the fault point is expressed by the following formula:

[0024]

[0025]

[0026] In the formula, represents the arrival time of the reflected wave at the fault point at the M end, represents the arrival time of the initial fault traveling wave at the M end, L represents the total length of the line, v represents the transmission speed of the fault traveling wave, represents the first wave head calibration error, represents the arrival time of the reflected wave at the fault point at the N end, represents the arrival time of the initial fault traveling wave at the N end.

[0027] Furthermore, the process of determining the sampling time window includes: defining a time constant, and constructing a sampling time window with the arrival time of the initial fault traveling wave head as the reference point.

[0028] Further, the timing constraint of the reflected wave at the second fault point is expressed by the following formula:

[0029]

[0030]

[0031] In the formula, represents the time when the reflected wave at the fault point reaches terminal M, represents the time when the reflected wave from the opposite bus reaches terminal M, represents the time when the initial fault traveling wave reaches terminal M, is the length of the branch line, v represents the transmission speed of the fault traveling wave, represents the calibration error of the second wavefront, represents the time when the reflected wave at the fault point reaches terminal N, represents the time when the reflected wave from the opposite bus reaches terminal N, represents the time when the initial fault traveling wave reaches terminal N.

[0032] Further, the process of judging the polarity difference between the reflected wave at the fault point and the reflected wave from the opposite bus includes:

[0033] The polarities of the reflected wave at the fault point and the reflected wave from the opposite bus are only related to the positive and negative of the reflection and refraction coefficients. The traveling wave refraction coefficient at the branch node P1 and the traveling wave refraction coefficient at point F are both positive. The reflection coefficient of the traveling wave at the branch node P1 and the reflection coefficient of the traveling wave at the branch node F are both negative. The reflection coefficient Q at the end node of the branch is positive; The polarity of is where

[0034] When n = 1, ; The polarity of is n When = 1, ; In the first reflection, the wavefront polarities of the two reflected waves are consistent with the polarity of represents the reflected wave from the opposite bus;

[0035] When n = 2, and , at this time, the coefficients of the two types of traveling waves are opposite, indicating is still the same as the polarity, while is opposite to the polarity; represents the initial fault traveling wave;

[0036] The primary wave heads of the fault point reflection wave and the primary wave head of the reflection wave from the opposite busbar are clearly distinguished through polarity analysis and the time when they reach both ends of the line. The time when they reach both ends of the line.

[0037] The second aspect of the present invention provides a fault location system for multi-branch distribution lines based on time-domain difference.

[0038] A fault location system for multi-branch distribution lines based on time-domain difference, comprising:

[0039] A data acquisition module configured to: acquire the basic parameters of the faulty line, the faulty section, and the fault traveling wave data at both ends of the line; the basic parameters include wave impedance, inductance per unit length, and capacitance;

[0040] A time-domain difference module configured to: obtain the line-mode components of the fault traveling wave based on the fault traveling wave data at both ends of the line, and perform discretization; the line-mode components of the fault traveling wave include sine components and exponentially decaying components; perform time-domain difference operation on the discretized line-mode components of the fault voltage traveling wave to eliminate the sine components and obtain the line-mode component signal of the fault traveling wave;

[0041] A wave head calibration module configured to: construct an objective function, optimize the line-mode component signal of the fault traveling wave, and determine the time-domain positions of the fault traveling wave heads at both ends of the line to calibrate the time when the fault traveling wave heads reach both ends of the line;

[0042] A fault location module configured to: if it is a main line fault, based on the basic parameters of the faulty line and the faulty section, combined with the time when the fault traveling wave heads reach both ends of the line, establish the first timing constraint for the fault point reflection wave, and determine the time when the fault point reflection wave heads reach both ends of the line; based on the time when the fault point reflection wave heads reach both ends of the line, determine the fault point position; if it is a branch line fault, determine the time when the initial fault traveling wave, the fault point reflection wave, and the reflection wave from the opposite busbar reach both ends of the line respectively; within the sampling time window, according to the second timing constraint for the fault point reflection wave, combined with the polarity difference between the fault point reflection wave and the reflection wave from the opposite busbar, determine the time when the fault point reflection wave and the reflection wave from the opposite busbar first reach both ends of the line to determine the fault point position.

[0043] The third aspect of the present invention provides a computer device, which includes:

[0044] A processor suitable for executing a computer program;

[0045] A computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the steps in the fault location method for multi-branch lines of a distribution network based on time-domain difference as described in the first aspect above are implemented.

[0046] The fourth aspect of the present invention provides a computer-readable storage medium that stores a computer program. The computer program is adapted to be loaded and executed by a processor to perform the steps in the fault location method for multi-branch lines of a distribution network based on time-domain difference as described in the first aspect above.

[0047] The fifth aspect of the present invention provides a computer program product or a computer program.

[0048] The present invention provides a computer program product or a computer program. The computer program product or the computer program includes computer instructions that are stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions to cause the computer device to perform the steps in the fault location method for multi-branch lines of a distribution network based on time-domain difference as described in the first aspect above.

[0049] Compared with the prior art, the beneficial effects of the present invention are:

[0050] The present invention proposes a fault location method for multi-branch lines of a distribution network based on time-domain difference. Starting from the perspective of time-domain difference operation, the fault traveling wave is represented in the form of a pulse signal for wavefront calibration; at the same time, the relationship between the subsequent fault traveling wavefront and the fault line length is explored. Based on the effective information of the fault traveling wavefront, the fault location of the multi-branch lines of the distribution network is realized under the condition that measuring devices are only equipped at the head and end of the main line.

[0051] The present invention proposes a method for calibrating the wavefront of traveling waves based on time-domain difference. This method represents the fault traveling wave as an exponentially decaying component superimposed on a sine wave within a sliding time window, and at the same time performs continuous differentiation on the line-mode component of the fault traveling wave to eliminate the sine component, thereby representing the fault traveling wave in the form of a pulse. Since the arrival time of the calibrated wavefront of the traveling wave is completed through basic time-domain difference operations, there is no need to consider setting calculation parameters, and it has strong adaptability and simple calculation.

[0052] The present invention proposes a fault location method based on the timing constraint of fault reflected waves. By analyzing the transmission mechanism of fault traveling waves in a multi-branch line topology, establishing the timing constraint of the fault reflected wave front, and determining the arrival time of the fault reflected wave front. Only the traveling wave detection devices equipped at both ends of the main line can accurately locate the faults of the multi-branch lines in the distribution network according to the arrival times of multiple subsequent wave fronts in the data at both ends. Compared with the traditional method, this scheme greatly reduces the number of deployed detection devices and improves the economy of fault location. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The attached drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0054] Figure 1 is a flowchart of a fault location method for multi-branch lines in a distribution network based on time domain difference shown in an embodiment of the present invention;

[0055] Figure 2 is a fault traveling wave grid diagram shown in an embodiment of the present invention;

[0056] Figure 3 Schematic diagram of the line mode component of the fault voltage traveling wave shown in an embodiment of the present invention;

[0057] Figure 4 Schematic diagram of the fault traveling wave propagation path shown in an embodiment of the present invention;

[0058] Figure 5 Fault traveling wave grid diagram of multi-branch lines shown in an embodiment of the present invention;

[0059] Figure 6 Schematic diagram of the voltage line mode component under the selected time window shown in an embodiment of the present invention;

[0060] Figure 7 Schematic diagram of the wave front calibration result shown in an embodiment of the present invention;

[0061] Figure 8 Schematic diagrams of the algorithm performance under different noises shown in an embodiment of the present invention; among them, (a) is the voltage traveling wave curve under 50 dB noise; (b) is the voltage traveling wave curve under 40 dB noise; (c) is the voltage traveling wave curve under 30 dB noise; (d) is the voltage denoising curve under 50 dB noise; (e) is the voltage denoising curve under 40 dB noise; (f) is the voltage denoising curve under 30 dB noise; (g) is the voltage traveling wave front calibration diagram under 50 dB noise; (h) is the voltage traveling wave front calibration diagram under 40 dB noise; (i) is the voltage traveling wave front calibration diagram under 30 dB noise;

[0062] Figure 9 The structural diagram of a multi-branch distribution line shown in an embodiment of the present invention;

[0063] Figure 10 is the structural diagram of a multi-branch line fault location system for a distribution network based on time domain difference shown in an embodiment of the present invention;

[0064] Figure 11 is the structural diagram of a computer device shown in an embodiment of the present invention. Detailed implementation manners

[0065] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0066] It should be noted that the following detailed descriptions are all exemplary and are intended to provide further descriptions of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0067] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0068] As Figure 1 shown, this embodiment provides a method for fault location of multi-branch lines in a distribution network based on time domain difference, including:

[0069] Obtain the basic parameters of the faulty line, the faulty section, and the fault traveling wave data at both ends of the line; wherein, the basic parameters include: wave impedance, inductance per unit length, and capacitance parameters, as shown in Table 1;

[0070] Table 1 - Basic parameters of the line

[0071]

[0072] 1. Traveling wave head calibration method based on time domain difference operation

[0073] In some embodiments, based on the fault traveling wave data at both ends of the line, obtain the fault traveling wave line mode component and discretize it; the fault traveling wave line mode component includes a sine component and an exponentially decaying component; perform time domain difference operation on the discretized fault voltage traveling wave line mode component to eliminate the sine component and obtain the fault traveling wave line mode component signal; the specific implementation process includes:

[0074] (1) Analysis of fault traveling wave characteristics

[0075] The traveling wave detection algorithm quickly locates the fault point by extracting the key features of the traveling wave signal. Therefore, it is crucial to analyze the transmission path and characteristics of the fault traveling wave signal.

[0076] According to the traveling wave theory, when a fault occurs in a distribution line, the fault point will excite a transient traveling wave, which travels along the line to both sides at a specific propagation speed. When it encounters a point of wave impedance change, reflection and refraction phenomena will occur. This physical process will continue until the traveling wave energy is completely dissipated, as Figure 2 shown.

[0077] By installing a traveling wave acquisition device on the line, the three-phase voltage traveling wave signal can be extracted and decoupled using the Karenbauer transform to obtain the fault traveling wave line-mode component, as Figure 3 shown. The fault traveling wave line-mode component can be divided into two parts: one is the sine component, and the other is the exponentially decaying component that reflects the fault characteristics. When the observation time window is short enough, the sine component can be approximated as a linear trend component.

[0078] The time-domain model of the fault traveling wave line-mode component can be expressed as:

[0079] (1)

[0080] Where: represents the total response of the fault signal; A represents the signal amplitude coefficient; t represents the time variable, used to describe the variation of the traveling wave signal with time; τ represents the signal decay time constant; is the unit step function; is the arrival time of the traveling wave within the time window; B and C are the slope and constant offset of the linear trend, respectively.

[0081] After discretizing the signal, the discrete-domain expression form of the fault traveling wave line-mode component is:

[0082] (2)

[0083] Where: ; is the unit step function; k is the discrete sampling point index, represents k the fault signal response at the sampling point.

[0084] In some embodiments, an objective function is constructed to optimize the fault traveling wave line-mode component signal, and the time-domain positions of the fault traveling wave wavefronts at both ends of the line are determined to calibrate the times when the fault traveling wave wavefronts reach both ends of the line; the specific implementation process includes:

[0085] 1.2 Wave head calibration based on time domain differential operation

[0086] The wave head calibration method based on time domain differential operation eliminates the linear trend component by performing differential calculation on the line mode component of the fault traveling wave, enhances the transient characteristics of the signal, and accurately calibrates the arrival time of the wave head of the traveling wave.

[0087] First, perform differential operation on the discrete signal of the line mode component of the fault traveling wave to obtain the first-order differential signal , and the expression is:[[]]

[0088] (3)[[]]

[0089] Substitute the discrete domain expression (2) of the line mode component of the fault traveling wave into equation (3), and we can get:[[]]

[0090] (4)[[]]

[0091] In the formula:[[]] represents the amplitude of the pulse delay term; , is the unit impulse function; it can be seen that equation (4) effectively eliminates the linear trend component in the signal.

[0092] Using the property of the discrete function of the function , where is the value of the discrete function at k = 0, equation (4) can be simplified to:[[]]

[0093] (5)[[]]

[0094] Furthermore, perform differential calculation on the signal to obtain the high-order differential form:[[]]

[0095] (6)[[]]

[0096] In the formula, represents the high-order differential signal.

[0097] At this time, substitute equation (5) into equation (6) to further eliminate the parameter B. After performing two differential calculations on the line mode component signal of the fault traveling wave, we get:[[]]

[0098] (7)[[]]

[0099] In the formula:[[]] A w1 and A w2The parameter determined by the exponential decay characteristic is specifically: , .

[0100] Through two - time difference operations, the linear trend and noise interference in the signal are removed, so that the instantaneous characteristic signal in the form of a pulse can be effectively extracted.

[0101] To further calibrate the arrival time of the fault traveling - wave head, the difference signal is optimized by the least - squares fitting method to ensure the optimal fitting parameter λ of the pulse function.

[0102] Assume and are the difference results at two consecutive moments. The optimal parameter λ is determined by minimizing the following objective function:

[0103] (8)

[0104] In the formula: and are respectively and discrete sampling values. Through the optimization calculation, the expression of the parameter λ is:

[0105] (9)

[0106] The parameter λ reflects the characteristics of the pulse signal without relying on the linear or exponential coefficients in the original signal. Finally, by formula (10) and choosing an appropriate value of λ, the fault traveling - wave can be expressed as a function of a sequence of Dirac pulses , as shown in formula (11):

[0107] (10)

[0108] (11)

[0109] In the formula: , and are the constant coefficients of the pulse function.

[0110] Formula (11) represents the fault traveling - wave with a pulse function, which can show the time - domain position characterizing the fault traveling - wave head, so as to accurately calibrate the arrival time of the traveling - wave head.

[0111] Through the above steps, the process of calibrating the fault traveling - wave head is more concise and does not rely on the selection of wavelet basis functions or other complex parameters.

[0112] In some embodiments, if it is a backbone line fault, based on the basic parameters and fault section of the fault line, combined with the time when the fault traveling wave head arrives at both ends of the line, a first fault point reflection wave timing constraint is established to determine the time when the fault point reflection wave head arrives at both ends of the line; based on the time when the fault point reflection wave head arrives at both ends of the line, the fault point location is determined; the specific implementation process includes:

[0113] 2. Double - ended traveling wave location of backbone line based on fault point reflection wave identification

[0114] 2.1 Identification of fault point reflection wave of backbone line

[0115] When a fault occurs at a certain point on the backbone line, the fault traveling wave undergoes multiple reflections and refractions at the fault point and both ends of the line. Figure 1 Shows the transmission path of the fault traveling wave at the fault point f The moments when the initial fault traveling waves are received at both ends of the line are respectively denoted as and , and the times when the first - reflected waves arrive at both ends are denoted as and . The timing relationship between the fault point reflection wave arriving at both ends of the line is closely related to the fault point location. Since multiple waveforms are generated due to the reflection and refraction of the traveling wave during transmission, it is usually difficult to accurately judge the signal source solely by detecting the arrival time sequence of the traveling wave signal. Therefore, it is necessary to establish the timing constraint of the fault point reflection wave to screen and .

[0116] Define L as the total length of the line, v as the transmission speed of the fault traveling wave. In this section, by analyzing the fixed relationship between , , L and v , a fault point reflection wave timing constraint is proposed to determine the arrival time of the fault point reflection wave head.

[0117] Specifically, first, combining with the traditional double - ended traveling wave method location formula, the fault distance from the fault point Figure 2 in f to the left end M of the line is expressed as:

[0118] (12)

[0119] In the formula, represents the fault distance.

[0120] Furthermore, using the transmission path relationship of the reflected wave head, the time when the fault point reflection wave arrives at the M - end is:

[0121] (13)

[0122] Substituting Equation (13) into Equation (12) and arranging, we get:

[0123] (14)

[0124] Considering that there may be a clock synchronization error between the two end acquisition devices, in order to further improve the positioning accuracy, the first wavefront calibration error is introduced, and the criterion for the time sequence constraint of the reflected wave at the fault point is:

[0125] (15)

[0126] When the arrival time of the traveling wave collected at the M end satisfies the constraint of Equation (15), then this moment can be determined as the moment when the reflected wave at the fault point first arrives at the M end.

[0127] Similarly, when the arrival time of the traveling wave collected at the N end satisfies the constraint of Equation (16), then this moment can be determined as the moment when the reflected wave at the fault point first arrives at the N end.

[0128] (16)

[0129] 2.2 Double - end traveling wave method based on fault point reflected wave identification

[0130] To solve the problem that the positioning result accuracy of the traditional double - end traveling wave method may be affected by the clock synchronization error, this embodiment proposes a double - end traveling wave method based on fault point reflected wave identification. This method analyzes the traveling wave signals at both ends of the main line, identifies the arrival time of the fault point reflected wave through time sequence constraints, and further combines the equivalent relationship of the single - end traveling wave positioning formula to deduce the double - end fault positioning formula based on the fault point reflected wave, so as to obtain the fault point distance.

[0131] Specifically, when the fault point is located on the line MN, first, the arrival time of the fault point reflected wave is screened out according to Equation (15) and Equation (16). Further, by using the fault traveling wave signals detected at both ends of the main line, the fault point positions measured at both ends are calculated respectively by using the single - end positioning algorithm:

[0132] (17)

[0133] (18)

[0134] In the formula, represents the distance from the fault point to the M end of the line; represents the distance from the fault point to the M end of the line.

[0135] Further, by combining the equal relationship of the measured fault point positions at both ends of equations (17) and (18), the distance from the fault point to the M end of the main line is derived:

[0136] (19)

[0137] Where: is the distance from the fault point f to the M end of the main line.

[0138] Similarly, the distance from the fault point to the N end of the main line can also be obtained :

[0139] (20)

[0140] Where: is the distance from the fault point f to the N end of the main line.

[0141] The main line positioning formulas (19) and (20) proposed by the present invention can further improve the double - end fault location formula by identifying the fault point reflected wave, and can solve the influence of the synchronous clock error.

[0142] 2.3 Double - end traveling wave location steps based on fault point reflected wave identification

[0143] The specific steps of the improved double - end traveling wave location method based on fault point reflected wave identification are as follows:

[0144] 1) Initial traveling wave head calibration. Using the time - domain differential algorithm proposed in this embodiment, calibrate the arrival times t M1 and t N1 of the initial traveling wave head of the fault at both the M and N ends.

[0145] 2) Fault point reflected wave identification. Based on the fixed relationship between , , L and v , construct equations (15) and (16) to screen and .

[0146] 3) Double - end traveling wave method based on fault point reflected wave identification. Through the fault traveling wave signals recorded by the traveling wave measuring devices at both ends of the main line, based on the and determined in step 2), use the location formulas shown in equations (19) and (20) to complete the fault location.

[0147] In some embodiments, in the case of a branch line fault, determine the times when the initial fault traveling wave, the reflected wave at the fault point, and the reflected wave at the opposite bus reach both ends of the line respectively; within the sampling time window, according to the second time sequence constraint of the reflected wave at the fault point, combined with the polarity difference between the reflected wave at the fault point and the reflected wave at the opposite bus, determine the times when the reflected wave at the fault point and the reflected wave at the opposite bus first reach both ends of the line, obtain two groups of fault location results, and calculate the average value to determine the fault point location; the specific implementation process includes:

[0148] 3. Fault Location of Branch Lines Based on the Time Sequence Constraint and Polarity Discrimination of Reflected Traveling Waves

[0149] 3.1 Traveling Wave Propagation Path of Branch Line Faults

[0150] When a fault occurs on a branch line, by analyzing the time domain constraint and polarity between the initial traveling wave and the subsequent reflected traveling waves, distinguish the traveling wave characteristics of the faulty line and the healthy line, and select the reflected wave at the fault point and the reflected wave at the opposite bus of the faulty section from numerous reflected and refracted traveling waves for branch line fault location. As Figure 4 shown. Taking the M end of the main line as the observation point, the arrival times and polarity characteristics of different traveling waves in the section P1Q1 can represent the fault information.

[0151] 3.2 Analysis of Traveling Wave Characteristics of Faulty Sections of Branch Lines

[0152] Taking a short - circuit fault occurring on the branch line P1Q1 as an example, analyze the initial traveling wave at the measurement end M and the reflected traveling wave of the faulty section. The transmission path is as Figure 5 shown.

[0153] The first traveling wave reaching the main line M is the initial fault traveling wave :

[0154] (21)

[0155] In the formula: is the step voltage applied at the fault point; is the distance from the fault point F to the bus M; represents the step function of the triggering time and propagation characteristics of the initial fault traveling wave, ; is the traveling wave reflection coefficient at the bus M; is the traveling wave refraction coefficient at the branch node P1; is the line propagation coefficient.

[0156] When a fault occurs on the faulty line P1Q1, among the subsequent traveling waves reaching point M after reflection and refraction, there are two types of groups of fault - reflected traveling waves containing fault distance information that can be used for single - end traveling wave location:

[0157] 1) The first type is the fault point reflected wave group, which is the traveling wave group transmitted through the branch node after refraction and reflection at point F. , which can be expressed as:

[0158] (22)

[0159] Where: n is the reflection times of the fault traveling wave at the fault point; represents the step function of the triggering time and propagation characteristics of the fault point reflected wave group; is the distance from point F to branch node P1; and respectively represent the reflection coefficients of the traveling wave at branch node P1 and point F.

[0160] 2) The second type is the far - end bus reflected wave group, which is the traveling wave group transmitted through point F and branch node P1 after reflection at the far - end bus Q1 point. , which can be expressed as:

[0161] (23)

[0162] Where: represents the step function of the triggering time and propagation characteristics of the far - end bus reflected wave group; is the reflection coefficient of the traveling wave at the far - end node Q1 of the branch; is the refraction coefficient of the traveling wave at point F; is the distance from point F to the far - end node Q1 of the branch.

[0163] 3.3 Analysis of the timing sequence and polarity of the reflected traveling wave for branch line faults

[0164] Taking Figure 4 a short - circuit fault occurring on branch line P1Q1 as an example, assume that the measuring point M detects the initial traveling wave of the fault arriving at time , the moment when the fault point reflected wave first arrives at point M is denoted as , and the moment when the far - end bus reflected wave first arrives at point M is denoted as . According to the single - end traveling wave method, we have:

[0165] (24)

[0166] Where: is the fault distance; is the length of the branch line.

[0167] Introduce the wavefront calibration error , and construct the first arrival times of the wavefronts of the two reflected traveling waves , and the arrival time of the initial traveling-wave head The time-domain constraint criterion between them is as follows:

[0168] (25)

[0169] Since the calibration of the initial traveling-wave head of the fault has high reliability, after determining the arrival time of the initial traveling-wave head of the fault, the time-domain constraint criterion in formula (25) can be used to screen the reflected wave of the fault point and the reflected wave of the opposite bus, and eliminate the interference of the refracted and reflected waves caused by the complex propagation path subsequently.

[0170] After screening out the reflected wave of the fault point and the reflected wave of the opposite bus, further explore their polarities. The polarities of the two fault reflected traveling waves are only related to the positive and negative of the refraction and reflection coefficients. 、 is a positive number, and is a negative number, is a positive number. The polarity of is which represents the polarity of and respectively represent the reflection coefficients of the traveling wave at the branch node P1 and the point F. Among them, when n = 1, ; The polarity of is n = 1, similarly, when ; In the first reflection, the wave head polarities of the two reflected waves are consistent with the polarity of . When n = 2, and , at this time, the coefficients of the two types of traveling waves are opposite, indicating that and still have the same polarity, while and have opposite polarities.

[0171] Based on the above analysis, the arrival sequence of and arriving at point M can be clearly distinguished through the polarity difference of the secondary wave heads, and the fault location of the branch line of the distribution network can be realized.

[0172] Based on the line topology structure of the multi-branch distribution network, the present invention analyzes the refraction and reflection coefficients of the traveling wave on the line to determine the polarity of the traveling wave, and does not require online estimation of the opposite-end impedance.

[0173] 3.4 Branch line fault location method based on reflected traveling waves

[0174] When the fault point is located on the branch line, two kinds of reflected waves are screened according to Equation (25), distinguished by combining the polarity characteristics, and single-ended location is carried out using the measurement information at the M end. The fault distance is calculated using the time difference between the two kinds of reflected waves respectively:

[0175] (26)

[0176] In the formula: represents the length of the line at the M end from node P1; is the fault distance obtained from the time difference between the wavefronts of and ; is and the fault distance obtained from the time difference between the wavefronts.

[0177] The two groups of fault location results can be mutually verified. When and are both within the error range, calculate the average value of the two, which can further improve the fault tolerance of the fault location.

[0178] (27)

[0179] Similarly, using the measurement device information at the N end to achieve single-ended location, we can get:

[0180] (28)

[0181] In the formula: is the fault distance obtained from the time difference between the wavefront of the initial fault traveling wave reaching the N end and the wavefront of the fault point reflection; is the fault distance obtained from the time difference between the wavefront of the initial fault traveling wave reaching the N end and the wavefront of the reflection from the opposite bus; represents calculating the average value of the two.

[0182] Using the fault traveling wave information obtained from the measurement devices at the M end and the N end respectively, single-ended traveling wave method location is carried out for a certain branch line, and the two groups of fault location results obtained can also be mutually verified. At the same time, when a measurement point fails to locate the fault due to a long distance, the other measurement point can provide necessary data support to ensure the effectiveness of the fault location.

[0183] 3.5 Steps of the fault location method for branch lines based on reflected traveling waves

[0184] The specific steps of the proposed method are as follows:

[0185] 1) Extract fault information. Extract and organize the relevant information of the fault line, including the basic parameters of the fault line, the fault section, and the fault traveling wave data collected from both ends of the line.

[0186] 2) Denoising preprocessing. Based on the improved Kalman filtering technology, noise suppression preprocessing is performed on the fault traveling wave signal to reduce the influence of noise on subsequent algorithms.

[0187] 3) Initial traveling wave head calibration. Based on the time-domain difference algorithm proposed in this paper, the specific times when the fault initial traveling wave arrives at the measurement endpoints M and N can be accurately measured, denoted as and .

[0188] 4) Determine the sampling time window. Combining the length of the fault branch line l Define the time constant τ = l / v . Taking the arrival time of the fault initial traveling wave head as the reference point, a sampling time window range is constructed, which covers 10 sampling points before the arrival of the initial traveling wave and all sampling points within 4τ after the arrival.

[0189] 5) Reflection traveling wave timing constraint and polarity discrimination. Within the sampling time window, the first wave heads of the reflected waves at the fault point and the reflected waves at the opposite bus are screened according to the time-domain constraint criterion, and distinguished by combining the polarity characteristics.

[0190] 6) Fault location. Using the measurement information at both ends respectively, based on the arrival times of the reflected waves at the fault point and the reflected waves at the opposite bus, the fault distance is calculated according to Equations (26)-(28).

[0191] 4. Simulation analysis

[0192] 4.1 Fault traveling wave head calibration

[0193] To evaluate the performance of the fault traveling wave head calibration method proposed in this embodiment, a simulation model as shown in Figure 2 is constructed based on the MATLAB / Simulink simulation platform. The line adopts a distributed parameter model, and the total line length is set to L = 5 km. Fault traveling wave acquisition devices are configured at both the M end and the N end of the line, with a sampling rate of 10 MHz. A phase A ground fault scenario is simulated at a distance of 1.5 km from the M end.

[0194] Based on , and τ , the sampling time window length is set to 695 sampling points, and the waveform of the line-mode component of the fault voltage within this time period is intercepted as shown in Figure 6 , and the corresponding wave head calibration is shown in Figure 7 .

[0195] According to Figure 6The recognition result shows that the arrival time of the initial traveling wave head of the fault is the 11.01st sampling point. Based on the time-domain constraint criterion in Equation (25), the arrival time of the reflected wave at the fault point is screened for the sampling point of 113.16, and the arrival time of the reflected wave at the opposite bus is screened for the sampling point of 251.36. Based on this, the calculated fault distance is 1490.55 m, and the error is only 0.63%. This shows that the wave head calibration method proposed in this embodiment can effectively calibrate the arrival time of the fault traveling wave head only through time-domain differential operation. According to the time-domain constraint criterion of the reflected traveling wave, the reflected traveling wave containing effective fault information is screened, and the fault location can be accurately located.

[0196] 4.1.1 Influence of Noise on Traveling Wave Head Calibration

[0197] To verify the influence of noise on traveling wave head calibration, Gaussian white noise with different intensities of 50, 40, and 30 dB is added to the voltage traveling wave detected at the M end, as shown in (a)-(c) of Figure 8 ; the line-mode component of the voltage traveling wave after denoising by improved Kalman filtering, as shown in (d)-(f) of Figure 8 ; the traveling wave head calibration results proposed in this embodiment, as shown in (g)-(i) of Figure 8 .

[0198] Table 2 Traveling Wave Head Calibration Results under Different Noise Conditions

[0199]

[0200] As can be seen from Figure 8 and Table 2, under all test conditions, the arrival time of the initial traveling wave head is 1.101 μs, and noise has no influence on the arrival time of the initial traveling wave head; under the 40 dB noise condition, the error of the arrival time of the reflected wave at the fault point is the largest, which is 0.0885%; under the 50 dB noise condition, the error of the arrival time of the reflected wave at the opposite bus is the largest, which is 0.0954%. It can be seen that the denoising algorithm based on improved Kalman filtering effectively eliminates the interference of noise on the characteristics of fault traveling waves. Under different noise conditions, the calibration of the reflected wave at the fault point and the reflected wave at the opposite bus is hardly affected, and the calibration deviation can be ignored.

[0201] 4.1.2 Influence of Fault Conditions on Traveling Wave Head Calibration

[0202] To further verify the applicability and accuracy of the method described in this embodiment, it is compared and analyzed with the wavelet transform and HHT methods. In a Gaussian white noise environment with a signal-to-noise ratio of 50 dB, various fault types at different positions of the line are simulated, and the influence of different fault conditions on wave head calibration is evaluated. The fault location results of the three methods are summarized in Table 3.

[0203] Table 3 Fault Location Results of Three Methods under Different Conditions

[0204]

[0205] As can be seen from the comparison results in Table 3, under all test conditions, the average errors of the db6 wavelet transform and HHT are 20.79 m and 12.33 m respectively, while the average error of the method described in this embodiment is the smallest, which is 5.92 m. This is because the method described in this embodiment calibrates the fault traveling wave head in the form of a pulse signal through basic time-domain differential operations, is not affected by the selection of calculation parameters compared with the db6 wavelet transform method, and there is no mode mixing phenomenon and end effect compared with the HHT method.

[0206] 4.1.3 Comparison of algorithm location speeds

[0207] To study the location speeds of different wave head calibration methods, a computer equipped with an AMD Ryzen 7 7840H processor and 16 GB of RAM was used to compare the average calculation times of three algorithms under the same fault conditions. The results are shown in Table 4.

[0208] Table 4 Calculation times of three algorithms under the same conditions

[0209]

[0210] It can be obtained from Table 4 that the method of the present invention abandons frequency-domain transformation or mode decomposition, constructs a pure time-domain processing chain from wave head calibration to fault location, avoids problems such as wavelet basis selection and mode mixing, and while the algorithm is simple and easy to implement, compared with the wavelet transform and HHT, the calculation time is reduced by 50.8% and 82.7% respectively, effectively improving the location speed.

[0211] 4.2 Fault location results for multi-branch lines

[0212] To evaluate the accuracy of the method proposed in this embodiment, in this study, based on the MATLAB / Simulink simulation platform, a model as shown in Figure 9 was constructed, with section MP1 = 7 km, section P1P2 = 4.5 km, section P2P3 = 6 km, section P3N = 5 km, branch P1Q1 = 3 km, branch P2Q2 = 2.5 km, and branch P3Q3 = 4 km. Fault traveling wave acquisition devices were installed at both ends of the main line, and the sampling rate was 10 MHz.

[0213] 4.2.1 Analysis of fault location results for the main line

[0214] Under various fault conditions were simulated on the main line MN, and the obtained fault location data are listed in Table 5.

[0215] Table 5 Location data for the main line

[0216]

[0217] According to the results in Table 5, when the fault distance from the M end is 1500 m and 22000 m, the errors are 26.22 m and 19.92 m respectively. It can be seen that as the fault distance increases, the positioning error generally remains small. When the fault distance is 11000 m, the fault type is ABg, the transition resistance is 300 Ω, and the fault angle is 20°, the positioning error is only 1.58 m; while when the fault distance is 22000 m, the transition resistance is 100 Ω, and the fault angle is 90°, the error is 19.92 m. It can be seen that for different fault conditions, the positioning results are all stable, and the influence of fault conditions on the positioning accuracy is small.

[0218] Under different fault conditions, the method proposed in the present invention shows high accuracy and stability. The error range is mostly kept within 30 m. This is because the criterion of the time sequence constraint of the fault point reflection wave proposed in this embodiment can eliminate the interference of complex reflected and refracted waves, accurately identify the fault point reflection wave, and use the double-terminal traveling wave method based on the identification of the fault point reflection wave for fault location, eliminating the influence of clock synchronization error, thereby verifying the applicability of the method described in this embodiment for fault location on the main line in the multi-branch line model of the distribution network.

[0219] 4.2.2 Fault Location of Branch Lines

[0220] To verify the accuracy of the method proposed in this embodiment for fault location of branch lines, fault conditions under different branch lines are simulated. The fault information collected at both the M and N ends is comprehensively utilized. Among them, the fault voltage traveling wave information collected by the measuring device at the M end is used to calculate the distance between the fault point and the branch node through Equation (27), which is expressed as positioning result 1; the fault voltage traveling wave information collected by the measuring device at the N end is used to calculate the distance between the fault point and the branch node through Equation (28), which is expressed as positioning result 2. The fault location results are shown in Table 6. At the same time, measuring devices are equipped at the ends of each branch line, and the distance between the fault point and the branch node is calculated through Equation (12), which is expressed as positioning result 3, and compared with positioning result 1 and positioning result 2.

[0221] Table 6 Branch Line Location Data

[0222]

[0223] According to the results in Table 6, it can be seen that the proposed location method shows high accuracy under different fault branch conditions. Among them, when a fault occurs on the P1Q1 branch, the average errors of the two location schemes are 11.46 m and 6.75 m respectively; for the P2Q2 branch fault scenario, the corresponding average errors are 4.69 m and 8.69 m; and in the case of a fault on the P3Q3 branch, the average errors are further reduced to 4.29 m and 5.12 m. It can be seen that this location method has good branch adaptability and can achieve accurate fault distance measurement under different branch fault conditions. When the fault is located on the branch P1Q1 and the fault distances from the node Q1 are 600 m, 1200 m, 1800 m, and 3200 m, the location errors are 14.95 m, 0.15 m, 14.79 m, and 4.79 m respectively. It can be seen that the location error basically remains stable as the fault distance from the node Q1 increases. When the fault is located on the branch P1Q1 and the fault is 1200 m away from the branch node, when the fault type is Bg, the fault angle is 30°, and the transition resistance is 1000 Ω, the location error is 7.7 m; when the fault type is ABg, the fault angle is 50°, and the transition resistance is 200 Ω, the location error is 0.15 m. It can be seen that under different fault conditions, the location error remains within a small range, and the method described in this embodiment has good adaptability to different fault conditions. The average errors of Location Result 1, Location Result 2, and Location Result 3 are 8.997 m, 6.388 m, and 16.159 m respectively. It can be seen that the fault location method proposed in this embodiment has fewer measurement devices while improving the fault location accuracy. This is because the fault reflection traveling wave timing constraint and polarity criterion proposed in this embodiment can effectively screen out the fault point reflection wave and the opposite bus reflection wave for branch line fault location, and only need to use the fault voltage traveling wave information recorded by the traveling wave measurement devices equipped at both ends of the main line to complete the fault location. When faults occur on different branch lines, Location Result 1 and Location Result 2 can be mutually verified, and the reliability can be further improved when both location results are accurate.

[0224] Aiming at the problems of difficult wavefront calibration and high fault location cost in the traveling wave fault location method for multi-branch lines in the distribution network, this embodiment proposes a fault location method for multi-branch lines in the distribution network based on the time-domain difference algorithm. The effectiveness of this method is verified through theoretical analysis and simulation. The main conclusions are as follows:

[0225] (1) Based on the wavefront calibration method of the time-domain difference algorithm, by analyzing the fault traveling waves within a reasonable time window, the wavefronts of the fault traveling waves can be accurately calibrated, and it is less affected by noise. Compared with the wavelet transform and HHT methods, the wavefront calibration method proposed in this embodiment does not require complicated parameter settings and has higher wavefront calibration accuracy for traveling waves.

[0226] (2) Fault location method for multi-branch lines in a distribution network. By using the time-domain constraint and polarity relationship of fault traveling waves to determine the arrival time of the reflected wavefront, fault location for the multi-branch model can be achieved only by configuring measurement terminals on the main line. Under different fault conditions, the error range is mostly within 30m, showing high accuracy and stability. The proposed method is less affected by factors such as fault location, fault type, transition resistance, and fault angle, and can achieve accurate fault location with high positioning accuracy.

[0227] For the increasingly complex scenarios of distributed power source access and the variability of the distribution system structure, the method proposed in this paper requires further research and development in terms of adaptability and algorithm optimization to meet the requirements of modern distribution systems for improving reliability and economy.

[0228] The above combination Figure 1 has introduced in detail the fault location method for multi-branch lines in a distribution network based on time-domain difference provided by the embodiments of the present invention. Next, the fault location system for multi-branch lines in a distribution network based on time-domain difference provided by the embodiments of the present invention will be introduced with reference to the accompanying drawings.

[0229] Figure 10 is a schematic structural diagram of the fault location system for multi-branch lines in a distribution network based on time-domain difference shown in the embodiments of the present invention. Referring to Figure 10 , the system of the present invention includes:

[0230] A data acquisition module, which is configured to: acquire the basic parameters of the faulty line, the faulty section, and the fault traveling wave data at both ends of the line;

[0231] A time-domain difference module, which is configured to: obtain the line-mode component of the fault traveling wave based on the fault traveling wave data at both ends of the line and perform discretization; the line-mode component of the fault traveling wave includes a sine component and an exponentially decaying component; perform time-domain difference operation on the discretized line-mode component of the fault voltage traveling wave to eliminate the sine component and obtain the line-mode component signal of the fault traveling wave;

[0232] A wavefront calibration module, which is configured to: construct an objective function, optimize the line-mode component signal of the fault traveling wave, and determine the time-domain positions of the fault traveling wavefronts at both ends of the line to calibrate the arrival times of the fault traveling wavefronts at both ends of the line;

[0233] A fault location module, which is configured to: if it is a main line fault, based on the basic parameters and fault section of the fault line, and in combination with the time when the fault traveling wave head reaches both ends of the line, establish the first timing constraint of the fault point reflection wave, and determine the time when the fault point reflection wave head reaches both ends of the line; based on the time when the fault point reflection wave head reaches both ends of the line, determine the fault point location; if it is a branch line fault, determine the time when the fault initial traveling wave, the fault point reflection wave, and the reflection wave of the opposite end bus reach both ends of the line respectively; within the sampling time window, according to the second timing constraint of the fault point reflection wave, and in combination with the polarity difference between the fault point reflection wave and the reflection wave of the opposite end bus, determine the time when the fault point reflection wave and the reflection wave of the opposite end bus first reach both ends of the line, so as to determine the fault point location

[0234] The distribution network multi-branch line fault location system based on time domain difference according to the embodiment of the present invention can correspond to execute the method described in the embodiment of the present invention, and the above and other operations and / or functions of each module of the distribution network multi-branch line fault location system based on time domain difference are respectively for realizing Figure 1 the corresponding processes of each method in, for the sake of brevity, will not be described in detail here.

[0235] Refer to Figure 11 the structure diagram of the computer device shown in. The computer device includes a processor, a communication interface, and a computer-readable storage medium. Among them, the processor, the communication interface, and the computer-readable storage medium can be connected through a bus or other means. Among them, the communication interface is used to receive and send data. The computer-readable storage medium can be stored in the memory of the computer device. The computer-readable storage medium is used to store a computer program. The computer program includes program instructions. The processor is used to execute the program instructions stored in the computer-readable storage medium. The processor (or CPU (Central Processing Unit, central processor)) is the computing core and control core of the computer device, and is adapted to implement one or more instructions, and is specifically adapted to load and execute one or more instructions to implement the corresponding steps in the embodiment of the distribution network multi-branch line fault location method based on time domain difference.

[0236] This embodiment provides a computer-readable storage medium (Memory). The computer-readable storage medium is a memory device in the computer device and is used to store programs and data. It can be understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and, of course, the extended storage medium supported by the computer device. The computer-readable storage medium provides a storage space, and this storage space stores the processing system of the computer device.

[0237] Also, one or more instructions suitable for being loaded and executed by a processor are stored in this storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory; optionally, it can also be at least one computer-readable storage medium located far from the aforementioned processor.

[0238] In one embodiment, one or more instructions are stored in the computer-readable storage medium; the one or more instructions stored in the computer-readable storage medium are loaded and executed by the processor to implement the corresponding steps in the above embodiments of the method for fault location of multiple branch lines in a distribution network based on time-domain difference.

[0239] This embodiment provides a computer program product or a computer program. The computer program product or the computer program includes computer instructions, and the computer instructions are stored in a computer-readable storage medium. The processor of the computer device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, so that the computer device executes the corresponding steps in the above embodiments of the method for fault location of multiple branch lines in a distribution network based on time-domain difference.

[0240] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of an embodiment implemented in hardware, a software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memories and optical memories, etc.) containing computer-usable program codes.

[0241] The present invention is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram can be implemented by computer program instructions, and the combination of the flows and / or blocks in the flowchart and / or block diagram can also be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the functions specified in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0242] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a particular manner, such that the instructions stored in the computer-readable memory produce a manufacture including an instruction device that implements the functions specified in one or more processes and / or blocks Figure 1 in one or more processes and / or blocks Figure 1 specified in the function.

[0243] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operational steps are performed on the computer or other programmable device to produce a computer-implemented process, thereby providing steps for implementing the functions specified in one or more processes and / or blocks Figure 1 in one or more processes and / or blocks Figure 1 specified in the function.

[0244] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above methods. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM), etc.

[0245] The foregoing is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A fault location method for multi-branch lines in a distribution network based on time-domain difference, characterized in that Including: Obtain the basic parameters of the faulty line, the faulty section, and the fault traveling wave data at both ends of the line; The basic parameters include wave impedance, inductance per unit length, and capacitance; Based on the fault traveling wave data at both ends of the line, obtain the fault traveling wave line mode component and discretize it; the fault traveling wave line mode component includes a sine component and an exponentially decaying component; perform a time-domain difference operation on the discretized fault voltage traveling wave line mode component to eliminate the sine component and obtain the fault traveling wave line mode component signal; Install a traveling wave acquisition device on the line, extract the three-phase voltage traveling wave signal, and use the Karenbauer transform for decoupling to obtain the fault traveling wave line mode component; The line-mode component of the fault traveling wave is divided into two parts: one part is the sine component, and the other part is the exponentially decaying component reflecting the fault characteristics. When the observation time window is short enough, the sine component is approximately a linear trend component; the time-domain model of the line-mode component of the fault traveling wave is expressed as: ; In the formula: represents the total response of the fault signal; A represents the signal amplitude coefficient; t represents the time variable, which is used to describe the change of the traveling wave signal with time; τ represents the signal attenuation time constant; is the unit step function; is the arrival time of the traveling wave within the time window; B and C are the slope and the constant offset of the linear trend respectively; After discretizing the signal, the discrete-domain expression form of the fault traveling wave line-mode component is as follows: ; In the formula: ; is the unit step function; k is the discrete sampling point index, represents k the fault signal response of the sampling point; First, perform a difference operation on the discrete signal of the line-mode component of the fault traveling wave to obtain the first-order difference signal , where: A represents the signal amplitude coefficient; is the unit impulse function, represents the amplitude of the pulse delay term; ; Differentiate the signal to eliminate parameter B and obtain the high-order differential form: where: A w1 and A w2 are parameters determined by the exponential decay characteristics, specifically: , ; Construct an objective function, optimize the fault traveling wave line mode component signal, determine the time-domain positions of the fault traveling wave wavefronts at both ends of the line, and calibrate the times when the fault traveling wave wavefronts reach both ends of the line; The objective function is expressed by the following formula: ; where and are respectively and discrete sampling values of , represent the line-mode component signals of the fault traveling wave, and λ represents the optimal fitting parameter; If it is a main line fault, based on the basic parameters and the faulty section of the faulty line, combined with the times when the fault traveling wave wavefronts reach both ends of the line, establish the first fault point reflection wave timing constraint to determine the times when the fault point reflection wave wavefronts reach both ends of the line; Based on the times when the fault point reflection wave wavefronts reach both ends of the line, determine the fault point location; If it is a branch line fault, determine the times when the fault initial traveling wave, the fault point reflection wave, and the far-end bus reflection wave reach both ends of the line respectively; Within the sampling time window, according to the second fault point reflection wave timing constraint, combined with the polarity differences between the fault point reflection wave and the far-end bus reflection wave, determine the times when the fault point reflection wave and the far-end bus reflection wave first reach both ends of the line to determine the fault point location.

2. The method for fault location of multi-branch lines in a distribution network based on time-domain difference according to claim 1, characterized in that The first fault point reflection wave timing constraint is expressed by the following formula: Wherein, represents the time when the reflected wave from the fault point arrives at the M terminal, represents the time when the initial fault traveling wave arrives at the M terminal, L represents the total length of the line, v represents the transmission speed of the fault traveling wave, represents the calibration error of the first wavefront, represents the time when the reflected wave from the fault point arrives at the N terminal, represents the time when the initial fault traveling wave arrives at the N terminal.

3. The method for fault location of multi-branch lines in a distribution network based on time domain difference according to claim 1, wherein The process of determining the sampling time window includes: defining a time constant, and constructing a sampling time window with the arrival time of the fault initial traveling wave wavefront as the reference point.

4. The method for fault location of multi-branch lines in a distribution network based on time-domain difference according to claim 1, wherein, The second fault point reflection wave timing constraint is expressed by the following formula: In the formula, represents the time when the reflected wave from the fault point arrives at terminal M, represents the time when the reflected wave from the opposite bus arrives at terminal M, represents the time when the initial fault traveling wave arrives at terminal M, is the length of the branch line, v represents the transmission speed of the fault traveling wave, represents the calibration error of the second wavefront, represents the time when the reflected wave from the fault point arrives at terminal N, represents the time when the reflected wave from the opposite bus arrives at terminal N, represents the time when the initial fault traveling wave arrives at terminal N.

5. The fault location method for multi-branch lines of a distribution network based on time-domain difference according to claim 1, characterized in that The judgment process of the polarity differences between the fault point reflection wave and the far-end bus reflection wave includes: The polarities of the reflected waves at the fault point and the reflected waves at the opposite bus are only related to the positive and negative of the reflection and refraction coefficients. The traveling wave refraction coefficient at the branch node P1 and the traveling wave refraction coefficient at point F are both positive numbers. The reflection coefficient of the traveling wave at the branch node P1 and the reflection coefficient of the traveling wave at the branch node F are both negative numbers. The reflection coefficient of the traveling wave at the end node of the branch Q 1 is a positive number; The polarity of is where represents the reflected wave at the fault point. Among them, when n = 1, ; The polarity of is n = 1, ; In the first reflection, the wavefront polarities of the two reflected waves are consistent with the polarity of ; represents the reflected wave of the opposite busbar; When n = 2, and At this time, the coefficients of the two types of traveling waves are opposite, indicating that and still have the same polarity, while and have opposite polarities; represents the initial traveling wave of the fault; Distinguish the primary wavehead of the fault point reflection wave and the primary wavehead of the reflection wave of the opposite bus clearly through polarity analysis and the arrival time of the primary wavehead of the reflection wave of the opposite bus at both ends of the line.

6. A multi-branch line fault location system for a distribution network based on time domain difference, characterized in that, Including: A data acquisition module configured to: obtain the basic parameters of the faulty line, the faulty section, and the fault traveling wave data at both ends of the line; The basic parameters include wave impedance, inductance per unit length, and capacitance; A time-domain difference module configured to: based on the fault traveling wave data at both ends of the line, obtain the fault traveling wave line mode component and discretize it; the fault traveling wave line mode component includes a sine component and an exponentially decaying component; perform a time-domain difference operation on the discretized fault voltage traveling wave line mode component to eliminate the sine component and obtain the fault traveling wave line mode component signal; install a traveling wave acquisition device on the line, extract the three-phase voltage traveling wave signal, and use the Karenbauer transform for decoupling to obtain the fault traveling wave line mode component; The line-mode component of the fault traveling wave is divided into two parts: one part is the sine component, and the other part is the exponentially decaying component reflecting the fault characteristics. When the observation time window is short enough, the sine component is approximately a linear trend component. The time-domain model of the line-mode component of the fault traveling wave is expressed as: ; In the formula: represents the total response of the fault signal; A represents the signal amplitude coefficient; t represents the time variable, used to describe the variation of the traveling wave signal with time; τ represents the signal attenuation time constant; is the unit step function; is the arrival time of the traveling wave within the time window; B and C are the slope and constant offset of the linear trend respectively; After discretizing the signal, the discrete-domain expression form of the fault traveling-wave line-mode component is as follows: ; In the formula: ; is the unit step function; k is the discrete sampling point index, represents k the fault signal response of the sampling point; First, perform a difference operation on the discrete signal of the fault traveling wave line mode component to obtain the first-order difference signal , where: is the unit impulse function, represents the amplitude of the pulse delay term; ; Differentiate the signal to eliminate parameter B and obtain a high-order difference form: ; where: A w1 and A w2 are parameters determined by the exponential decay characteristics, specifically: , ; A wavefront calibration module configured to: construct an objective function, optimize the fault traveling wave line mode component signal, determine the time-domain positions of the fault traveling wave wavefronts at both ends of the line, and calibrate the times when the fault traveling wave wavefronts reach both ends of the line; The objective function is expressed by the following formula: ; where and are respectively and discrete sampling values of and represent the fault traveling wave line-mode component signals, and λ represents the optimal fitting parameter; A fault location module, which is configured to: if it is a main line fault, based on the basic parameters and fault section of the faulty line, and in combination with the time when the fault traveling wave head reaches both ends of the line, establish a timing constraint for the reflected wave at the fault point, and determine the time when the reflected wave head of the fault point reaches both ends of the line; Based on the time when the reflected wave head of the fault point reaches both ends of the line, determine the fault point location; if it is a branch line fault, determine the time when the initial fault traveling wave, the reflected wave at the fault point, and the reflected wave at the opposite bus reach both ends of the line; within the sampling time window, according to the second timing constraint for the reflected wave at the fault point, and in combination with the polarity difference between the reflected wave at the fault point and the reflected wave at the opposite bus, determine the time when the reflected wave at the fault point and the reflected wave at the opposite bus first reach both ends of the line, so as to determine the fault point location.

7. A computer device, characterized in that a processor, adapted to execute a computer program; a computer-readable storage medium, in which a computer program is stored, and when the computer program is executed by the processor, it implements the steps in the method for fault location of multi-branch distribution network based on time domain difference according to any one of claims 1-5.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, and the computer program is adapted to be loaded and executed by the processor to implement the steps in the method for fault location of multi-branch distribution network based on time domain difference according to any one of claims 1-5.

9. A computer program product, characterized in that, The computer program product includes a computer program, and when the computer program is executed by the processor, it implements the steps in the method for fault location of multi-branch distribution network based on time domain difference according to any one of claims 1-5.

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