Multi-branch power distribution network double-end traveling wave fault positioning method and system

Abstract

The invention relates to a multi-branch power distribution network double-end traveling wave fault positioning method and system, and the method comprises the steps: deploying a plurality of measurement points based on the head and tail ends of a radial power distribution network and branch terminals, collecting topological information, and calculating the linear mode wave velocity; using the three-phase voltage data after the fault to extract traveling wave line mode and zero mode components through modulus decoupling; a line mode component with the strongest global mutation is selected as a reference, and a wave head time sequence table is generated through wavelet decomposition and mutation detection; and correcting the zero-mode wave velocity by combining the topology, the time sequence table and the line-mode wave velocity, and determining a fault interval and outputting a fault position after compensation and correction by using the line-mode and zero-mode wave head time difference. According to the invention, through a wave head time sequence analysis and time difference compensation mechanism based on cooperation of multiple measuring points, positioning errors caused by clock asynchronization and parameter disturbance are effectively overcome, accurate distance measurement which is not influenced by clock errors is realized, and the distance measurement precision is significantly improved; and meanwhile, the point distribution requirement is simplified, accurate judgment and positioning of a fault interval can be realized only by a branch single measuring point, and high economy and deployment flexibility are both achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power distribution network fault location, and particularly relates to a multi-branch power distribution network double-end traveling wave fault location method and system. BACKGROUND

[0002] Traditional double-end traveling wave fault location methods face severe challenges in power distribution networks. Due to the complex topology and numerous branches of power distribution networks, existing technologies usually rely on high-precision clock synchronization of two-end devices. Once there is clock drift or communication delay, it will cause fixed ranging errors, significantly reducing the positioning accuracy. At the same time, line parameter disturbance further amplifies the error, making it difficult to meet the demand for fast and accurate fault location of intelligent power distribution networks.

[0003] Therefore, there is an urgent need to provide a technical solution to solve the above problems. SUMMARY

[0004] To solve the above technical problems, the present application provides a multi-branch power distribution network double-end traveling wave fault location method and system.

[0005] In a first aspect, the present application provides a multi-branch power distribution network double-end traveling wave fault location method, and the technical scheme of the method is as follows: Through the traveling wave detection terminals set at the head end, tail end and terminal of each branch of the radial multi-branch power distribution network, the topology information of the main line and branch line is collected, and the line mode wave speed is calculated based on the line parameters; The three-phase voltage and current data after the fault are collected by each measuring point, and the line mode component and zero mode component of the initial voltage traveling wave of the fault point are extracted by performing modulus decoupling processing on the three-phase voltage data; According to the voltage variation amplitude of the line mode component of each measuring point, the line mode component with the most significant global jump is selected as the unified analysis reference; The selected line mode component is subjected to multi-scale wavelet decomposition and sudden change detection, and the line mode wave head arrival time and zero mode wave head arrival time of each measuring point are extracted to generate a wave head arrival time sequence table; Based on the topology information, the wave head arrival time sequence table, the line mode wave speed and the corrected zero mode wave speed, the fault interval is determined, and during the fault interval determination process and the final positioning, the time difference between the line mode wave head arrival time and the zero mode wave head arrival time is used for compensation and correction, and the fault position is output.

[0006] The beneficial effects of the multi-branch power distribution network double-end traveling wave fault location method of the present application are as follows: The method of the present application effectively overcomes the positioning error caused by clock asynchronization and parameter disturbance through the wave front timing analysis and time difference compensation mechanism of multi-measurement-point cooperation, realizes accurate ranging unaffected by clock error, and significantly improves the ranging accuracy; meanwhile, the distribution point requirement is simplified, and only a single measurement point of a branch can realize accurate fault interval discrimination and positioning, which has high economy and deployment flexibility.

[0007] On the basis of the above-mentioned scheme, the multi-branch power distribution network double-end traveling wave fault location method of the present application can be further improved as follows.

[0008] In an alternative way, the topology information includes the connection relationship and physical distance of the trunk line, the first-level branch and the second-level branch.

[0009] In the above-mentioned alternative way, by explicitly limiting the topology information to include the connection relationship and physical distance of the trunk line and the branch line, the fault interval judgment is supported by structured data, the misjudgment caused by fuzzy topology in the positioning process is avoided, and the positioning reliability under the multi-branch complex network is improved.

[0010] In an alternative way, the step of calculating the line mode wave speed based on the line parameters includes calculating the line mode wave speed through the inductance parameter and the capacitance parameter of the corresponding line.

[0011] In the above-mentioned alternative way, the line mode wave speed is directly calculated through the line inductance and capacitance parameters, the error caused by the traditional method relying on the fixed wave speed value is avoided, the adaptability of the algorithm to the line parameter fluctuation is enhanced, and an accurate wave speed reference is provided for subsequent time difference compensation.

[0012] In an alternative way, the step of modulus decoupling processing includes converting the three-phase voltage signal into line mode components and zero mode components through the Kelvin-Bell transformation.

[0013] In the above-mentioned alternative way, the three-phase voltage signal is quickly decoupled through the standardized Kelvin-Bell transformation, the electromagnetic coupling interference is eliminated, the extracted line mode / zero mode components are ensured to be pure and reliable, and a high-quality signal source is provided for wave head detection.

[0014] In an alternative way, the step of selecting the line mode component with the most significant global jump as the unified analysis reference according to the voltage variation amplitude of each measurement point line mode component includes: calculating the voltage variation amplitude of each line mode component of each measurement point; wherein the voltage variation amplitude is obtained by differential calculation to obtain the maximum differential value; selecting the line mode component with the strongest mutation as the unified analysis reference by globally comparing the maximum differential value results of all measurement points.

[0015] In the optional manner, the maximum difference value of each measuring point line mode component is compared globally to dynamically select the optimal analysis reference, thereby avoiding the misselection caused by weak single measuring point signal or noise interference, and significantly improving the robustness of wave head feature recognition.

[0016] In an optional manner, the selected line mode component is subjected to multi-scale wavelet decomposition and mutation detection, and the line mode wave head arrival time and zero mode wave head arrival time of each measuring point are extracted, including: The selected line mode component is subjected to wavelet decomposition, the high-frequency detail component is extracted, and the high-frequency detail component is subjected to difference processing to generate a mutation rate curve; According to the mutation rate curve, the wave head position is detected in combination with a preset time window and a threshold condition, and the line mode wave head arrival time and the zero mode wave head arrival time are recorded respectively.

[0017] In the optional manner, the mutation rate curve is generated by difference processing of the high-frequency detail component, and the first fault wave head is accurately captured in combination with the time window and the threshold double criteria, and the power frequency jitter is shielded, thereby solving the pain point of the traditional method that is susceptible to noise interference.

[0018] In an optional manner, the step of compensation correction includes: A time difference elimination term is constructed based on the line mode wave head arrival time and the zero mode wave head arrival time to eliminate the clock synchronization error; A function relationship between the fault distance difference and the zero mode time difference is fitted by the least square method, the corrected zero mode wave speed is calculated based on the time difference elimination term, and the line mode wave speed and the corrected zero mode wave speed are used for double-end traveling wave distance measurement to output the fault point distance.

[0019] In an optional manner, the step of calculating the corrected zero mode wave speed includes: The linear function relationship between the fault distance difference and the zero mode time difference is fitted by the least square method, and the function relationship coefficient obtained by fitting is directly used as the corrected zero mode wave speed.

[0020] In the optional manner, the time difference elimination term is constructed by the time difference between the line mode wave head and the zero mode wave head to fundamentally offset the influence of the clock synchronization error on distance measurement; meanwhile, the linear function relationship between the fault distance difference and the zero mode time difference is directly fitted by the least square method, and the fitting coefficient is used as the corrected zero mode wave speed, thereby avoiding the precision loss caused by the attenuation of the zero mode wave speed and greatly simplifying the calculation process of the correction parameter. The scheme can obtain a high-precision corrected wave speed through one linear fitting, avoids the complex multi-end weighted calculation in the traditional method, and significantly improves the distance measurement stability and anti-interference ability in a complex branch power grid.

[0021] In an alternative mode, based on the topology information, the wave front arrival time sequence table, the line mode wave speed and the corrected zero mode wave speed, the step of determining the fault interval comprises: According to the wave front arrival time sequence table, the line mode wave front arrival time and the zero mode wave front arrival time of the head and tail end measuring points are obtained, and the line mode wave speed and the corrected zero mode wave speed are combined to perform double-end traveling wave distance measurement on the head and tail end measuring points of the power distribution network to obtain the fault distance. According to the fault distance, the node physical distance and the trunk line length in the topology information are combined to judge whether the fault is located on the trunk line. If the fault is located on the trunk line, the fault interval is determined as the trunk line. If the fault is not on the trunk line, the wave front arrival time sequence table and the time sequence of each branch end measuring point are combined to locate the first or second branch line where the fault is located, and the fault interval is determined.

[0022] In the above alternative mode, the trunk / branch fault interval is distinguished by combining the head and tail end distance measurement results and the wave front time sequence table, and only a single measuring point is needed to locate the branch fault position, which greatly reduces the complexity of point arrangement and takes into account the economy and positioning efficiency.

[0023] In a second aspect, the application provides a multi-branch power distribution network double-end traveling wave fault positioning system, and the technical scheme of the system is as follows: The multi-branch power distribution network double-end traveling wave fault positioning system comprises a topology collection and wave speed calculation module, a signal processing and feature extraction module, a time difference compensation and wave speed correction module, and a fault interval positioning and output module. The topology collection and wave speed calculation module is used to: deploy traveling wave detection terminals at the head, tail and each level branch terminal of the radial multi-branch power distribution network, collect topology information including the connection relationship and physical distance of the trunk line and branch line, and calculate the line mode wave speed based on the inductance parameters and capacitance parameters of the line.

[0024] The signal processing and feature extraction module is used to: collect three-phase voltage and current data after the fault at each measuring point, perform modulus decoupling on the three-phase voltage signal through the Kailunbei transformation, extract the line mode component and the zero mode component of the initial voltage traveling wave at the fault point, calculate the maximum difference value of the line mode component of each measuring point, select the most significant line mode component with the largest jump through global comparison as the unified analysis reference, perform wavelet decomposition on the line mode component, extract the high-frequency detail component and generate the mutation change rate curve, detect the wave front position combined with the preset time window and threshold condition, record the line mode wave front arrival time and the zero mode wave front arrival time of each measuring point, and generate the wave front arrival time sequence table.

[0025] The time difference compensation and wave velocity correction module is used for: constructing a time difference elimination term based on the line mode and zero mode wave head arrival time, eliminating the two-end clock synchronization error; adopting a least square method to perform linear function relationship fitting on the fault distance difference and the zero mode time difference, and directly taking the function relationship coefficient obtained by fitting as the corrected zero mode wave velocity, and performing double-end traveling wave distance measurement by using the line mode wave velocity and the corrected zero mode wave velocity, and outputting the fault point distance.

[0026] The fault interval positioning and output module is used for: obtaining the line mode wave head arrival time and the zero mode wave head arrival time of the first-end and last-end measuring points according to the wave head arrival time sequence table, and performing double-end traveling wave distance measurement on the first-end and last-end measuring points of the distribution network by combining the line mode wave velocity and the corrected zero mode wave velocity, and obtaining the fault distance; judging whether the fault is located on the main line according to the fault distance, in combination with the node physical distance and the main line length in the topological information; if the fault is located on the main line, determining that the fault interval is the main line; if the fault is not located on the main line, positioning the first-level or second-level branch line where the fault is located in combination with the wave head arrival time sequence table and the time sequence of each branch end measuring point, and determining the fault interval.

[0027] The beneficial effects of the multi-branch distribution network double-end traveling wave fault positioning system of the application are as follows: The system of the application effectively overcomes the positioning error caused by clock asynchronization and parameter disturbance by the wave head time sequence analysis and time difference compensation mechanism of the multi-measuring point cooperation, realizes accurate distance measurement not affected by clock error, and significantly improves the distance measurement accuracy; meanwhile, the point arrangement requirement is simplified, and only a branch single measuring point is needed to realize accurate fault interval discrimination and positioning, and the system has high economy and deployment flexibility.

[0028] The above description is only a summary of the technical scheme of the application, in order to more clearly understand the technical means of the application, the specific embodiments of the application can be implemented according to the content of the specification, and in order to make the above and other purposes, characteristics and advantages of the application more obvious and easy to understand, the following specifically describes the embodiments of the application. BRIEF DESCRIPTION OF DRAWINGS

[0029] The accompanying drawings are only used to show the embodiments and are not considered as limiting the application. Moreover, the same reference signs are used to represent the same components throughout the drawings. In the drawings: Figure 1 It is a flowchart of a multi-branch distribution network double-end traveling wave fault positioning method of the application; Figure 2 It is a detailed flowchart of the overall fault positioning; Figure 3 It is a 35kV distribution network fault simulation topological structure diagram; Figure 4 It is a wave head positioning flowchart; Figure 5A linear error comparison chart for different clock errors; Figure 6 A schematic diagram of the relationship between fault distance difference and zero-mode time difference; Figure 7 A schematic diagram of a D-type traveling wave distance measurement process for correcting time difference; Figure 8 A PSCAD / EMTDC simulation model diagram; Figure 9 A structural schematic diagram of a multi-branch power distribution network double-ended traveling wave fault location system of the present application. DETAILED DESCRIPTION

[0030] Exemplary embodiments of the present application will be described in greater detail below with reference to the accompanying drawings. Although exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein.

[0031] Figure 1 A flowchart of an embodiment of a multi-branch power distribution network double-ended traveling wave fault location method provided by the present application is shown, as shown in Figure 1 includes the following steps: S1, by setting up traveling wave detection terminals at the head end, tail end and terminal of each level of branch of the radial multi-branch power distribution network, collecting the topological information of the main line and branch line, and calculating the line mode wave speed based on the line parameters, in S1: 1) The traveling wave detection terminal refers to a signal acquisition device deployed at the head end, tail end and terminal of each level of branch of the power distribution network, for real-time monitoring of line voltage and current data.

[0032] 2) The topological information contains the physical connection relationship of the main line, the first level branch, the second level branch and the physical distance of each section of line, which provides structural basis for fault interval division.

[0033] Specifically, in the radial multi-branch power distribution network, traveling wave detection terminals are installed at the head end (power supply side), tail end (load side) and all branch terminals; the line topological structure (such as node connection relationship, branch length) is synchronously collected, and the line mode wave speed reflecting the high-frequency traveling wave propagation speed is calculated based on the inductance parameters and capacitance parameters of the line.

[0034] S2, using each measuring point to collect three-phase voltage and current data after the fault, and performing modulus decoupling processing on the three-phase voltage data to extract the line mode component and zero mode component of the initial voltage traveling wave of the fault point, in S2: 1) The modulus decoupling processing refers to converting the three-phase voltage signal coupled electromagnetically into independent modal components, eliminating interphase interference.

[0035] 2) Among the line mode component and the zero mode component, the line mode component represents the inter-phase traveling wave characteristics, and the zero mode component represents the ground fault traveling wave characteristics, which together constitute the basis for fault analysis.

[0036] Specifically, after the fault occurs, each measuring point synchronously collects three-phase voltage and current data; the three-phase voltage signal is decoupled into uncoupled line mode components and zero mode components through the Kelvin-Bell transformation, and the initial voltage traveling wave modal signal generated at the fault point is extracted.

[0037] S3, according to the voltage variation amplitude of the line mode component of each measuring point, the line mode component with the most significant global jump is selected as the unified analysis reference, in S3: 1) The voltage variation amplitude is obtained by differential calculation to obtain the instantaneous jump strength of the line mode component, reflecting the mutation characteristics of the fault traveling wave.

[0038] 2) The most significant global jump refers to the overall jump amplitude of all measuring points, and the line mode component with the largest jump amplitude is selected as the unified analysis object.

[0039] Specifically, the maximum difference value (instantaneous jump peak value) of each measuring point is calculated for each of the three line mode components; the calculation results of all measuring points are summarized, and the line mode component with the strongest global cumulative jump amplitude is selected as the unified signal reference for subsequent wave head detection.

[0040] S4, multi-scale wavelet decomposition and mutation detection are performed on the selected line mode component, the line mode wave head arrival time and the zero mode wave head arrival time of each measuring point are extracted, and a wave head arrival time sequence table is generated, in S4: 1) Multi-scale wavelet decomposition refers to decomposing the signal into components of different frequencies through wavelet transform, focusing on the high-frequency mutation characteristics.

[0041] 2) The mutation change rate curve is obtained by differentiating the high-frequency detail component, generating a curve reflecting the mutation rate of the signal, which is used for accurate positioning of the wave head.

[0042] Specifically, the selected line mode component is decomposed by wavelet, and the first layer high-frequency detail component (d1) is extracted; the mutation change rate curve is generated by differentiating the d1 component, and the wave head is located by combining the preset time window and amplitude threshold; the accurate arrival time of the line mode wave head and the zero mode wave head of each measuring point is recorded, and a wave head arrival time sequence table is generated in time order.

[0043] S5, based on the topological information, the wave head arrival time sequence table, the line mode wave speed and the corrected zero mode wave speed, the fault interval is determined, and in the process of determining the fault interval and finally positioning, the time difference between the line mode wave head arrival time and the zero mode wave head arrival time is used for compensation and correction, and the fault location is output, in S5: 1) The time difference elimination term refers to the combination of the time difference between the line mode and the zero mode wave head to offset the fixed error introduced by the clock of the two end devices.

[0044] 2) The fault interval refers to the line section where the fault point is located, such as the main line, the first branch or the second branch.

[0045] Specifically, when performing double-ended traveling wave distance measurement on the first and last end points, the time difference between the line mode and the zero mode wave head is used to construct the time difference elimination term, and the modified zero mode wave speed is directly used for compensation and correction to output the fault point distance. Then, by comparing the distance with the node distance in the topology information, it is judged whether the fault is located on the main line. If the fault is located on the main line, the modified distance measurement result is directly taken as the final positioning position; if the fault is located on the branch line, the specific branch is positioned according to the wave head time sequence table, and the modified distance measurement method is used to output the accurate position of the fault point in the branch interval.

[0046] Figure 2 The positioning process of the overall fault is shown, which includes six core steps: first, deploy detection terminals at key nodes of the power distribution network and collect topology information; after the fault occurs, perform signal decoupling and modulus analysis; generate a time sequence table through wave head detection; finally, realize accurate positioning in combination with topology and modified distance measurement method.

[0047] The technical scheme of the embodiment effectively overcomes the positioning error caused by clock asynchronization and parameter disturbance through the wave head time sequence analysis and time difference compensation mechanism of multiple measurement point cooperation, realizes accurate distance measurement not affected by clock error, and significantly improves the distance measurement accuracy; at the same time, the point deployment requirement is simplified, and only a single measurement point on the branch can realize accurate fault interval discrimination and positioning, which has high economy and deployment flexibility.

[0048] In an optional manner, the topology information includes the connection relationship and physical distance of the main line, the first branch and the second branch.

[0049] It should be noted that, as shown in Figure 3 The straight line from the first end point ① to the last end point ⑥ is the main line. The branch such as ② and ③ directly branched from the main line is the first branch. The branch such as ④, ⑤, ⑦, ⑧ and ⑨ branched from the first branch is the second branch.

[0050] In an optional manner, the step of calculating the line mode wave speed based on the line parameters comprises calculating the line mode wave speed through the inductance parameter and the capacitance parameter of the corresponding line.

[0051] In the embodiment, by deploying corresponding traveling wave detection terminals at the head and tail of the 35kV power distribution system with typical radial multi-branch power distribution line structure and at the terminal points of each branch, the topological information of the main line and each primary and secondary branch is saved, and the line mode wave speed of the line is obtained through line parameter, and the calculation formula is as follows: (1) wherein, is the traveling wave line mode component wave speed; , are the line zero mode inductance and capacitance respectively.

[0052] In an alternative way, the step of the module decoupling processing comprises: converting the three-phase voltage signal into line mode component and zero mode component through Karenbauer transformation.

[0053] In the embodiment, after the fault occurs, the traveling wave detection terminals deployed at each measuring point of the power distribution network synchronously collect three-phase voltage signals. The three-phase voltage signals are denoted as , , , which respectively represent the voltage instantaneous value of phase A, phase B and phase C.

[0054] Due to the electromagnetic coupling between the three-phase conductors, traveling waves will also be generated on the non-fault phase, and the equations describing the fluctuations are not independent of each other. In order to eliminate the coupling effect and effectively extract the fault characteristics, the collected three-phase voltage signals need to be decoupled and converted into independent mode components.

[0055] Karenbauer transformation is used to convert the phase domain system (i.e. the ABC three-phase system) into a non-coupled mode domain system. The mathematical expression of the transformation is as follows: (2) wherein, , , are the three-phase voltage instantaneous values (unit: volt V) before decoupling respectively; is the zero mode voltage component (unit: volt V) obtained after transformation, which represents the common mode part of the three-phase voltage; is one of the line mode voltage components (unit: volt V) obtained after transformation, which represents the differential mode part flowing between the A-phase conductor and the B-phase conductor; is one of the line mode voltage components (unit: volt V) obtained after transformation, which represents the differential mode part flowing between the A-phase conductor and the C-phase conductor.

[0056] In order to facilitate module analysis and form a complete three-phase loop description, a third line mode component , which represents the differential mode part flowing between the B-phase conductor and the C-phase conductor. Component With , together constitute a complete set of description of the differential mode voltage among the three phases.

[0057] After the above-mentioned Kelanbell transformation, the original three-phase coupled voltage signal , , is successfully decoupled into the zero-mode voltage component and the line-mode voltage component , , and the auxiliary analysis component is introduced.

[0058] In an optional manner, the step of selecting the line-mode component with the most significant global jump as the unified analysis reference according to the voltage variation amplitude of each measurement point line-mode component includes: Calculate the voltage variation amplitude of each line-mode component of each measurement point; wherein the voltage variation amplitude is obtained by differential calculation to obtain the maximum differential value; Select the line-mode component with the strongest jump as the unified analysis reference by globally comparing the maximum differential value results of all measurement points.

[0059] In this embodiment, the line-mode component includes , component obtained by modal decoupling processing (such as the aforementioned Kelanbell transformation), and the component representing the flow between the B-phase conductor and the C-phase conductor introduced according to the integrity of the three-phase loop. Therefore, the line-mode voltage signal available for analysis at each measurement point is , , three.

[0060] For single measurement point voltage variation amplitude calculation, for each line wave detection terminal measurement point, the voltage variation amplitude of its three line-mode voltage components , , is calculated respectively. The voltage variation amplitude is obtained by differential calculation, specifically, the maximum differential value of the line-mode voltage signal sequence is calculated, which is used to identify the most significant jump feature in the signal.

[0061] All measurement points are selected for the same line-mode component (for example, all measurement points ) The maximum difference value results are globally compared. The specific strategy is: the maximum difference value results of all measuring points for a certain line mode component are accumulated (i.e. summed up), to obtain the global total variation amplitude of the line mode component. The global total variation amplitudes of three line mode components (a, b, c) are calculated respectively. , , ) corresponding to the three line mode components (a, b, c) are calculated respectively.

[0062] The global total variation amplitudes of the three line mode components are compared, and the line mode component with the largest total variation amplitude is selected. The selected line mode component will be used as the unified signal input and unified analysis reference for the wave head detection and analysis of all subsequent measuring points. In addition, on the basis of the global comparison strategy, the fault type information can be used as an auxiliary criterion, but the core selection standard is based on the global maximum difference value accumulation.

[0063] In an optional manner, the selected line mode component is subjected to multi-scale wavelet decomposition and mutation detection, and the steps of extracting the line mode wave head arrival time and the zero mode wave head arrival time of each measuring point include: The selected line mode component is subjected to wavelet decomposition, the high-frequency detail component is extracted, and the high-frequency detail component is subjected to difference processing to generate a mutation rate curve; According to the mutation rate curve, the wave head position is detected in combination with a preset time window and a threshold condition, and the line mode wave head arrival time and the zero mode wave head arrival time are recorded respectively.

[0064] In this embodiment, the selected optimal line mode voltage (i.e. the line mode component with the most significant global jump) is used as the unified signal input. The multi-scale wavelet transform method is used to decompose the selected line mode voltage signal of each measuring point. Specifically, Daubechies wavelet db4 is used as the wavelet basis function to decompose the signal for 5 layers, the first layer of the decomposed detail component is extracted, and is denoted as d1 (high-frequency detail component). The d1 component can effectively reflect the mutation characteristics of the signal in the high-frequency part, and is the main carrier of the fault traveling wave wave head.

[0065] The extracted d1 high-frequency detail component of each measuring point is subjected to difference processing. The difference processing calculates the amplitude change between adjacent sampling points to obtain the mutation rate curve of the d1 component. The curve represents the rate of change of the signal amplitude with time, and the wave head position usually corresponds to a significant mutation point on the curve.

[0066] Based on the generated mutation rate curve (i.e. the d1 signal after difference processing, denoted as , where k represents the kth sampling point), in combination with a preset time window and a threshold condition, the wave head position is detected. The specific detection process is shown in Figure 4 . The preset sampling frequency is 10 MHz. In the difference result In the middle, skip a preset initial time window (0.01 ms). This window is used to shield the power steady-state components in the transition section before and after the fault and the weak jitter generated by the initial sampling, to avoid the subtle disturbance in the steady-state area or the sampling moment being misjudged as a wave head, and to improve the detection reliability.

[0067] In the data after skipping the window, search for a point that meets the following conditions as the mutation starting point: ; (3) wherein, represents the signal amplitude of the kth sampling point (from the d1 component after differential processing); is a threshold coefficient, with a value range of 5-10 times. This value is an empirical value determined through multiple simulations and statistical analysis under noise conditions; represents the global average amplitude of the signal (usually excluding data in the shielding area when calculating).

[0068] For candidate wave head position determination, within a time window (0.02 ms) after the found mutation starting point, search for the point with the maximum amplitude as the candidate wave head position (denoted as the kth point).

[0069] For wave head position criterion verification, for the found candidate wave head position k, apply the following two criteria for verification: The first criterion: the wave head is a certain range of maximum value point, that is, the candidate point k needs to be a local peak, satisfying: ; (4) wherein, respectively represent the signal amplitudes of the adjacent sampling points on the left and right of the candidate point k; is the time interval between the two adjacent sampling points (under a sampling rate of 10 MHz, ).

[0070] The second criterion: the mutation rate of the wave head is much larger than the average mutation rate, that is, through the time derivative of the equivalent discrete signal, to measure the change speed of the signal at the nth point, the larger the mutation rate, the more obvious the wave head characteristics. As shown in formula (5), when , then the kth point is determined as the wave head position, wherein is the global average mutation rate. Therefore, the mutation rate of the candidate point k needs to be significantly higher than the global average level, satisfying: ; (5) wherein, represents the mutation rate of the candidate point k (equivalent to the time derivative of the discrete signal); For The global average mutation rate of the signal is calculated as = ; represents the signal amplitude of the nth sampling point; If the candidate point k satisfies both the first criterion and the second criterion, it is determined that the point k is the line-mode voltage wave head position. If it does not satisfy any criterion, the time window is expanded and the candidate wave head position determination and wave head position criterion verification are re-executed, that is, the candidate point with the maximum amplitude in the larger window is re-searched and the criterion verification is performed, until the wave head position that satisfies the condition is found.

[0071] In terms of wave head time recording, for each measuring point: the arrival time corresponding to the finally determined line-mode voltage wave head is recorded. Similarly, for the zero-mode voltage component signal, the wavelet decomposition and high-frequency detail component extraction are repeatedly executed to the wave head position detection, that is, the wavelet decomposition extraction d1, the difference, and the wave head detection are also performed, and the arrival time corresponding to the zero-mode voltage wave head of the measuring point is recorded.

[0072] In the wave head timing table generation, the line-mode wave head arrival times and the zero-mode wave head arrival times recorded for all n measuring points are respectively arranged in order (usually sorted in time from early to late), and a precise wave head arrival timing table is generated. The timing table provides reliable and precise time scale basis for subsequent fault interval judgment and D-type ranging unaffected by time difference.

[0073] In an optional manner, the step of compensation correction comprises: Based on the line-mode wave head arrival time and the zero-mode wave head arrival time, a time difference elimination term is constructed to eliminate the clock synchronization error; The function relationship between the fault distance difference and the zero-mode time difference is fitted by using the least square method, the corrected zero-mode wave speed is calculated based on the time difference elimination term, and the double-end traveling wave ranging is performed by using the line-mode wave speed and the corrected zero-mode wave speed, and the fault point distance is output.

[0074] In an optional manner, the step of calculating the corrected zero-mode wave speed comprises: The linear function relationship fitting of the fault distance difference and the zero-mode time difference is performed by using the least square method, and the function relationship coefficient obtained by fitting is directly taken as the corrected zero-mode wave speed.

[0075] It should be noted that after the wave head time of each measuring point is extracted and sorted, the fixed error caused by the clock of the two end devices is reduced by using the time difference of the line mode and the zero mode wave head, and the traditional D-type ranging formula is improved: by introducing the line-zero mode time difference, the time difference influence is eliminated from the calculation formula, so that in the case of insufficient time accuracy or communication delay, high accuracy can still be maintained. Considering that the zero mode wave speed presents frequency-dependent attenuation characteristics during long distance transmission, in order to further improve the stability of the ranging, based on the characteristics that the zero mode wave speed presents frequency-dependent attenuation with the transmission time difference of the left and right ends, a polynomial fitting based on the least square method is introduced to compensate and correct the zero mode wave speed, so as to improve the stability and accuracy of the ranging. Through simulation analysis of the relationship between fault distance difference and zero mode time difference, the zero mode time difference from the fault point to the two end measuring points is calculated for different fault distance differences, and the equivalent average zero mode wave speed is calculated as the corrected zero mode wave speed. The corrected zero mode wave speed is substituted into the D-type traveling wave ranging which is not affected by the time difference, and the accurate fault positioning is realized.

[0076] The fault point to the left end distance is taken as the calculation reference, and the D-type traveling wave ranging method which is not affected by the time difference is improved as follows: The traditional D-type traveling wave ranging is: ; (6) But due to the clock drift or communication delay, etc., the fixed clock error is introduced, which greatly reduces the accuracy of the ranging. After adding the clock error, it is as follows: ; (7) Wherein, represents the length of the line between the left and right ends; is the line mode wave speed; , are the arrival times of the left and right ends respectively; is the clock error (generally not more than ); is the line length from the fault point to the left and right ends without considering the time difference.

[0077] When the synchronization error of the time synchronization device at both ends is too large, it will cause significant error to the fault ranging accuracy, but the time difference between the line mode and the zero mode wave head can eliminate the influence of the clock synchronization error . Therefore, the line-zero mode time difference can be used to improve the traditional D-type traveling wave ranging to the D-type traveling wave ranging which is not affected by the time difference.

[0078] In this embodiment, the time difference elimination term is constructed to eliminate the clock synchronization error: the time difference elimination term is constructed by using the line mode wave head arrival time and the zero mode wave head arrival time, so as to eliminate the fixed error (clock error ) caused by the clock of the two end devices. Specifically: The core principle of constructing the time difference elimination term is that the clock error term in the line mode time difference and the zero mode time difference can be offset each other as shown in equation (8), thus, the line zero mode time difference is used to improve the traditional D-type traveling wave distance measurement to the D-type traveling wave distance measurement not affected by the time difference as shown in equation (9): ; (8) ; (9) Wherein, , are the time (obtained from the wave head arrival time sequence) of the line mode traveling wave respectively reaching the left measurement endpoint and the right measurement endpoint of the fault interval; , are the time (obtained from the wave head arrival time sequence) of the zero mode traveling wave respectively reaching the left measurement endpoint and the right measurement endpoint of the fault interval.

[0079] Wherein, denotes the distance (to-be-solved quantity) from the fault point to the left measurement endpoint; denotes the total length of the line between the left and right measurement endpoints; is the line mode wave speed (known, calculated from the line parameters); is the zero mode wave speed (basic value, calculated from the line parameters, but needs to be corrected later); is the calculation result of the time difference elimination term, which does not contain the clock error in the result .

[0080] Since the zero mode wave speed will gradually decay with the increase of the fault distance, the error caused by this decay will become more and more obvious with the increase of the distance, and when the distance between the left and right ends of the line is too large, it will also have an adverse effect on the distance measurement result, so equation (9) is rewritten as: ; (10) It should be noted that the basis for rewriting is that since the zero mode wave speed there is a frequency-dependent attenuation effect in long-distance propagation, and direct use of the time difference elimination term will still cause distance measurement deviation. The specific performance is that when the fault point is close to the left measurement endpoint, due to the attenuation effect of the zero mode wave speed, the actual value of the calculated zero mode wave speed will be greater than its true value, and since the attenuation degree of the zero mode at the left and right ends is different, this error is more significant, and vice versa. In the formula, it is specifically embodied as Since uses the excessively large value relative to the actual value, causes , which will cause the error to increase in the actual process. In addition, it should be clear that the main role of equation (10) is theoretical analysis, which reveals how the attenuation effect leads to​ Thus, an error is generated. Formula (10) is not designed for final calculation.

[0081] In view of the good monotonicity between the fault distance difference and the zero-mode time difference at the left and right ends, the least square method can be used to fit the corresponding relationship between the two. Specifically, the relationship between the fault distance difference and the zero-mode time difference is fitted by simulation analysis, and the zero-mode time difference from the fault point to the two end measurement points is obtained for different fault distance differences. The fitting coefficient is calculated as a modified zero-mode wave speed, which has better precision than the original actual zero-mode wave speed without considering the attenuation of the zero-mode wave speed. Thus, a modified zero-mode wave speed with a relatively moderate attenuation degree between the left and right ends is obtained, which does not damage the principle of distance measurement using the line zero time difference. A moderate attenuation zero-mode wave speed is used to replace the original calculation wave speed, so that the clock error is completely eliminated from the formula, thereby improving the accuracy of distance measurement and obtaining a more accurate fault distance. The linear error is defined as the relative error of the linear part of the distance measurement formula after introducing the clock error, which is compared with the traditional method as shown in Figure 5 .

[0082] In this embodiment, after the construction of the D-type traveling wave distance measurement formula (formula 9) not affected by the time difference is completed, in view of the fact that the zero-mode wave speed presents frequency-dependent attenuation characteristics during long-distance propagation, and there is a good monotonicity between the zero-mode wave speed and the transmission time difference at the left and right ends, the zero-mode wave speed needs to be compensated and modified to improve the stability and precision of distance measurement. The steps of compensation and modification include the following three steps: Linear fitting of the relationship between the fault distance difference and the zero-mode time difference: the least square method is used to perform linear fitting on the relationship between the fault distance difference and the zero-mode time difference , to obtain the relationship formula: ; (11) wherein, is the fault distance difference between the left and right ends, , and are the distances from the fault point to the left and right ends, respectively; is the zero-mode wave head arrival time difference at the left and right ends, = ; is the fitting coefficient, that is, the function relationship coefficient (subsequently used as the modified zero-mode wave speed ).

[0083] It should be noted that a model is built by using actual line parameters, sampling points are set at the left and right ends of the line, and fault points are set every 1 km, and zero-mode wave head time data under different fault distances are collected. For example, Figure 6As shown, the experimental verification of the first fitting coefficient is greater than 0.99, which proves the rationality of directly using the fitting coefficient as the corrected zero-mode wave speed, and when ; , the fitting equation does not contain a constant term.

[0084] Determination of the corrected zero-mode wave speed : the fitting coefficient is used as the corrected zero-mode wave speed , which satisfies the relationship: ; (12) The corrected wave speed has the following characteristics: is a fixed value and does not change with the change of clock error ; the clock error is completely eliminated from the ranging formula; and it represents the equivalent wave speed with a moderate attenuation degree between the left and right ends.

[0085] Substitute the corrected zero-mode wave speed into the D-type traveling wave ranging formula (9) that is not affected by the time difference, replacing the original , to calculate the fault point distance , and the final ranging formula is as follows: ; (13) Overall, the corrected ranging process is shown in Figure 7 : first, offline fitting of the linear relationship between fault distance difference and zero-mode time difference; second, direct use of the fitting coefficient as the corrected wave speed; and finally, substitution into the D-type ranging formula to resist the time difference impact and output the positioning result.

[0086] In an alternative way, based on the topology information, the wave head arrival time sequence table, the line mode wave speed and the corrected zero-mode wave speed, the step of determining the fault interval includes: According to the wave head arrival time sequence table, the line mode wave head arrival time and the zero-mode wave head arrival time of the first and last end measuring points are obtained, and the line mode wave speed and the corrected zero-mode wave speed are combined to perform double-end traveling wave ranging on the first and last end measuring points of the distribution network, to obtain the fault distance; According to the fault distance, the node physical distance and the main line length in the topology information are combined to determine whether the fault is located on the main line; If the fault is located on the main line, the fault interval is determined as the main line; If the fault is not on the main line, the wave head arrival time sequence table and the time sequence of each branch end measuring point are combined to locate the first or second branch line where the fault is located, to determine the fault interval.

[0087] It should be noted that, in the fault section judgment based on the obtained line topology, the physical distance of the measuring point and the wave speed information, and the generated wave head arrival time sequence table, due to the existence of line parameter deviation, collector measurement error and other factors in the actual distribution network environment, an error margin needs to be introduced in the fault line selection process (the value is 0.01). The margin setting basis is: the positioning relative error of the current traveling wave distance measurement algorithm under typical working conditions is generally less than 1%, and through multi-working condition simulation and field test verification, this margin can not only avoid the precision decline caused by the expansion of the positioning section (too large margin), but also prevent the missed detection caused by slight jitter of the wave head extraction (too small margin), so as to balance the engineering feasibility and the accuracy range of the mainstream algorithm. Therefore, the scheme combines the D-type double-end traveling wave distance measurement which is not affected by the time difference to locate the fault in two stages: first, the distance measurement is performed on the head and tail end measuring points of the distribution network to determine whether the fault is located on the main line; if it is not a main fault, the wave head time sequence of each branch end measuring point is used to locate the first or second branch section.

[0088] In the embodiment, the line mode wave head arrival time and the zero mode wave head arrival time of the head end measuring point (such as the measuring point 1 of Figure 3 ) and the tail end measuring point (such as the measuring point 6 of Figure 3 ) of the distribution network are obtained according to the wave head arrival time sequence table. The D-type traveling wave distance measurement formula which is not affected by the time difference after compensation correction is used to calculate the fault distance, that is, formula (13). The at this time is the calculated fault distance .

[0089] The main line coefficient is calculated by combining the node physical distance in the topology information and the length of the main line : ; (14) wherein, is the fault distance measured on the main line; is the physical distance of the nearest node to ; is the length of the main line.

[0090] If ≥ , the fault is located on the main line, and the fault section is determined as the main line. At this time, the fault position is located on the specific fault position of the main line .

[0091] If < , the fault is not located on the main line, and the branch positioning process is executed.

[0092] When the fault is not located on the main line, according to the wave head arrival time sequence table, the measuring point with the earliest wave head arrival time (recorded as the minimum measuring point) is located. Taking the minimum measuring point as a benchmark, double-ended traveling wave distance measurement is performed with the remaining n measuring points of the branch, respectively, to obtain fault distances , and branch coefficients are calculated: ; (15) wherein, wherein x is the length of the branch line (obtained from the topology information).

[0093] At this time, the distance measurement result is divided into two cases: If , that is, each branch coefficient is less than the error margin, it is judged that the fault is located on the primary branch line. At this time, traveling wave distance measurement is performed between the minimum measuring point and the nearest measuring point except the primary branch, and the obtained distance is recorded as . Combined with the line topology structure, the length of the primary branch line is subtracted from the measured fault distance, and then the length of the secondary branch where the minimum measuring point is located is added to obtain the specific fault position on the primary branch , which is shown as follows: ; (16) Otherwise, when is not satisfied: If , it is judged that the fault occurs on the secondary branch where the minimum measuring point is located, and traveling wave distance measurement is performed between the minimum measuring point and the measuring point with the second smallest outgoing time. At this time, the fault position is located in front of the minimum measuring point at a distance of (km): ; (17) If only one set of distance measurement results is abnormal, it is recorded as an abnormal measuring point , that is, , and the remaining results all satisfy , it is judged that the branch where the abnormal measuring point is located is the fault branch, and traveling wave distance measurement is performed between the minimum measuring point and the abnormal measuring point to obtain . At this time, the fault position is located in front of the abnormal measuring point at a distance of (km): ; (18) wherein, is the length of the fault branch measuring point.

[0094] To further illustrate the effect, experimental verification is performed, and further, the method is used as Figure 8 ​​​The PSCAD-MATLAB software was used to co-simulate a 35kV radial multi-branch distribution line. Detection devices were installed at the beginning and end points of the distribution network and at the end nodes of each secondary branch line. For ease of verification, all lines were set to the same parameters, and each detection device simultaneously acquired fault traveling wave signals. A phase-A ground fault was set at a location 10km from the branch start point on the primary branch connected to node 4, 10km from the end of the line. The sampling frequency was 10MHz, the fault occurrence time was 0.02s, the fault duration was 0.04s, the transition resistance was 50Ω, and the initial phase angle of the fault was... Table 1 shows the wavefront time sequence at each measuring point: Table 1 (Wavefront Time Sequence at Each Measurement Point): Table 1 provides the wavefront times at the beginning and end measuring points of the distribution network. Distance measurement determines the location of the fault on the main line. The main line criterion is then applied between the fault and the nearest node 4, satisfying the condition. Therefore, it can be determined that the fault is located on the first-level or second-level branch of node 4. Branch criteria are then used for further analysis. Three measuring points (numbered 7, 8, and 9) were set up on this branch road. The measuring point with the earliest wavefront (point 8) was used as the reference, and two sets of distance measurements were performed sequentially to meet the requirements. Therefore, it can be determined that the fault is located on the first-level branch of node 4.

[0095] According to Table 1, the distance is measured using the smallest measuring point (8) and the nearest measuring point (5) excluding this first-level branch. The line distance between measuring points 8 and 5 is obtained from the line topology. km. The relationship between zero-mode travel time and fault distance difference is analyzed through simulation in PSCAD. In MATLAB, the scatter plot obtained from the simulation is fitted using a first-order polynomial with the least squares method, thereby obtaining the relationship between zero-mode travel time and fault distance difference, and thus the corrected zero-mode wave velocity. Substitution (10): ; The distance measurement results show that the distance to the fault is 0.13 km different from the simulated fault distance, with a relative error of only 0.65%. The simulation results indicate that the measured fault location is very close to the set actual fault location, and the relative error is less than 1%.

[0096] Figure 9 A schematic diagram of an embodiment of a dual-end traveling wave fault location system 200 for a multi-control power grid provided by the present invention is shown. Figure 9 As shown, the system 200 includes: a topology acquisition and wave velocity calculation module 210, a signal processing and feature extraction module 220, a time difference compensation and wave velocity correction module 230, and a fault zone location and output module 240. The topology collection and wave velocity calculation module 210 is configured to: deploy a traveling wave detection terminal at a head end, a tail end and terminal ends of each level of branch of the radial multi-branch power distribution network, collect topology information including connection relationship and physical distance of main lines and branch lines, and calculate a line mode wave velocity based on inductance parameters and capacitance parameters of the lines.

[0097] The signal processing and feature extraction module 220 is configured to: collect three-phase voltage and current data after a fault at each measuring point, decouple the three-phase voltage signals by Kailenbel transformation, extract line mode components and zero mode components of initial voltage traveling waves at the fault point, calculate maximum difference values of the line mode components at each measuring point, select a line mode component with the most significant jump by global comparison as a unified analysis reference, perform wavelet decomposition on the line mode component, extract high-frequency detail components and generate a sudden change rate curve, detect wave head positions by combining a preset time window and a threshold condition, record line mode wave head arrival times and zero mode wave head arrival times at each measuring point, and generate a wave head arrival time sequence table.

[0098] The time difference compensation and wave velocity correction module 230 is configured to: construct a time difference elimination term based on the line mode and zero mode wave head arrival times, eliminate two-end clock synchronization errors, perform linear function relationship fitting on a fault distance difference and a zero mode time difference by using a least square method, directly use a function relationship coefficient obtained by the fitting as a corrected zero mode wave velocity, perform double-end traveling wave distance measurement by using the line mode wave velocity and the corrected zero mode wave velocity, and output a fault point distance.

[0099] The fault interval positioning and output module 240 is configured to: obtain line mode wave head arrival times and zero mode wave head arrival times of measuring points at the head end and the tail end according to the wave head arrival time sequence table, perform double-end traveling wave distance measurement on the measuring points at the head end and the tail end of the distribution network by combining the line mode wave velocity and the corrected zero mode wave velocity, and obtain a fault distance; determine whether the fault is located on a main line by combining node physical distances and main line lengths in the topology information according to the fault distance; if the fault is located on the main line, determine that a fault interval is the main line; if the fault is not located on the main line, locate a first-level or second-level branch line where the fault is located by combining the wave head arrival time sequence table and time sequences of measuring points at ends of branch lines, and determine the fault interval.

[0100] The technical scheme of the embodiment effectively overcomes positioning errors caused by clock asynchronization and parameter disturbance by a wave head time sequence analysis and time difference compensation mechanism of multiple measuring points, realizes accurate distance measurement not affected by clock errors, and significantly improves distance measurement accuracy; meanwhile, the technical scheme simplifies point deployment requirements, and only needs a single measuring point at a branch to realize accurate fault interval discrimination and positioning, and has high economy and deployment flexibility.

[0101] The steps of implementing the functions of the parameters and the modules in the multi-branch power distribution network double-end traveling wave fault location system 200 of the embodiment can refer to the parameters and steps in the embodiments of the multi-branch power distribution network double-end traveling wave fault location method, which will not be repeated here.

[0102] Although the embodiments of the present application have been shown and described above, it should be understood by those skilled in the art that the above embodiments are exemplary and cannot be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A multi-branch power distribution network double-ended traveling wave fault location method, characterized in that, The application relates to a method for determining a fault position in a radial multi-branch power distribution network. The method comprises the following steps: collecting topological information of main lines and branch lines by setting up travelling wave detection terminals at the head, tail and terminal ends of the radial multi-branch power distribution network, and calculating line mode wave velocity based on line parameters; Collecting three-phase voltage and current data after a fault at each measuring point, and performing modulus decoupling processing on the three-phase voltage data to extract line mode components and zero mode components of initial voltage travelling waves at the fault point; Selecting a line mode component with the most significant global jump as a unified analysis reference according to voltage variation amplitudes of line mode components at each measuring point; Performing multi-scale wavelet decomposition and mutation detection on the selected line mode component to extract line mode wave head arrival times and zero mode wave head arrival times at each measuring point, and generating a wave head arrival time sequence table; Determining a fault interval based on the topological information, the wave head arrival time sequence table, the line mode wave velocity and the corrected zero mode wave velocity, and compensating and correcting a time difference between the line mode wave head arrival time and the zero mode wave head arrival time during the fault interval determination process and the final positioning process, and outputting the fault position.

2. The multi-branch power network double-ended traveling wave fault location method according to claim 1, characterized in that, The topological information comprises connection relationships and physical distances of main lines, first-level branch lines and second-level branch lines.

3. The multi-branch power network double-ended traveling wave fault location method according to claim 1, characterized in that, The step of calculating the line mode wave velocity based on the line parameters comprises calculating the line mode wave velocity by using inductance parameters and capacitance parameters of corresponding lines.

4. The multi-branch power network double-ended traveling wave fault location method according to claim 1, characterized in that, The step of performing modulus decoupling processing comprises converting three-phase voltage signals into line mode components and zero mode components by using a Kelvin-Bell transformation.

5. The multi-branch power network double-ended traveling wave fault location method according to claim 1, characterized in that, The step of selecting a line mode component with the most significant global jump as a unified analysis reference according to voltage variation amplitudes of line mode components at each measuring point comprises the following steps: Calculating voltage variation amplitudes of each line mode component at each measuring point, wherein the voltage variation amplitudes are obtained by calculating maximum difference values through difference calculation; Selecting a line mode component with the strongest mutation as a unified analysis reference by globally comparing maximum difference value results of all measuring points.

6. The multi-branch power network double-ended traveling wave fault location method according to claim 1, characterized in that, The step of performing multi-scale wavelet decomposition and mutation detection on the selected line mode component to extract line mode wave head arrival times and zero mode wave head arrival times at each measuring point comprises the following steps: Performing wavelet decomposition on the selected line mode component to extract high-frequency detail components, and performing difference processing on the high-frequency detail components to generate a mutation change rate curve; Detecting wave head positions according to the mutation change rate curve, combining a preset time window and a threshold condition, and recording line mode wave head arrival times and zero mode wave head arrival times respectively.

7. The multi-branch power network double-ended traveling wave fault location method according to claim 6, characterized in that, The step of performing compensation and correction comprises the following steps: Constructing a time difference elimination term based on the line mode wave head arrival time and the zero mode wave head arrival time to eliminate clock synchronization errors; Fitting a functional relationship between a fault distance difference and a zero mode time difference by using a least square method, calculating a corrected zero mode wave velocity based on the time difference elimination term, and performing double-end travelling wave distance measurement by using the line mode wave velocity and the corrected zero mode wave velocity to output a fault point distance.

8. The multi-branch power network double-ended traveling wave fault location method according to claim 7, characterized in that, The step of calculating the corrected zero mode wave velocity comprises the following steps: Fitting a linear function relationship between the fault distance difference and the zero mode time difference by using a least square method, and directly taking a function relationship coefficient obtained through the fitting as the corrected zero mode wave velocity.

9. The multi-branch power network double-ended traveling wave fault location method according to claim 8, characterized in that, The step of determining the fault interval based on the topological information, the wave head arrival time sequence table, the line mode wave velocity and the corrected zero mode wave velocity comprises the following steps: According to the wave head arrival time sequence table, the line mode wave head arrival time and the zero mode wave head arrival time of the head and tail end measuring points are obtained, and the double-end traveling wave distance measurement is performed on the head and tail end measuring points of the power distribution network in combination with the line mode wave speed and the corrected zero mode wave speed, so as to obtain the fault distance; According to the fault distance, in combination with the node physical distance and the main line length in the topological information, it is judged whether the fault is located on the main line; If the fault is located on the main line, the fault interval is determined as the main line; If the fault is not located on the main line, in combination with the wave head arrival time sequence table and the time sequence of each branch end measuring point, the first or second branch line where the fault is located is positioned, and the fault interval is determined.

10. A double-ended traveling wave fault location system for a multi-branch power distribution network, characterized in that, The multi-branch power distribution network double-end traveling wave fault positioning method is adopted.

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