Method and system for locating and analyzing a ground fault of a power transmission line

Abstract

The application provides a power transmission line grounding fault positioning and analysis processing method and system, relates to the technical field of power system fault processing, and comprises the following steps: acquiring zero sequence component data and topological relations of monitoring points; extracting a fault feature vector reflecting impedance characteristics of a grounding path; determining a candidate fault section according to the direction distribution and amplitude attenuation law of the feature vector in the topology; constructing a zero sequence voltage propagation distribution function in the section, and solving the position of the zero sequence voltage gradient extreme point; identifying a fault type and a transition resistance state, and executing fault isolation. The application can accurately position a fault position and improve fault processing efficiency.

Description

Technical Field

[0001] This invention relates to the field of power system fault handling technology, and in particular to a method and system for locating and analyzing grounding faults in transmission lines. Background Technology

[0002] Transmission lines are a crucial component of the power system, playing a vital role in power transmission. However, due to their exposure to the natural environment, transmission lines are constantly affected by various external factors, such as lightning strikes, snowstorms, and tree strikes, making them prone to various faults, among which grounding faults are the most common. Grounding faults not only reduce system stability but can also trigger widespread power outages, severely impacting social production and daily life. Therefore, quickly and accurately locating grounding faults in transmission lines and effectively analyzing and addressing them is of great significance for improving the reliability and power quality of the power system. Summary of the Invention

[0003] The present invention provides a method and system for locating and analyzing grounding faults in transmission lines, which can solve the problems in the prior art.

[0004] A first aspect of the present invention provides a method for locating and analyzing grounding faults in transmission lines, comprising:

[0005] Acquire zero-sequence component data and topological connectivity relationships from multiple monitoring points in a transmission line;

[0006] Based on the zero-sequence component data, the transient waveforms of zero-sequence current and zero-sequence voltage are extracted, the zero-sequence component of the ground fault is calculated and time-frequency joint is performed to obtain the fault feature vector reflecting the impedance characteristics of the grounding path.

[0007] Based on the fault feature vector in the topological connection relationship, the directional distribution and amplitude attenuation law between each monitoring point are used to calculate the boundary node where the ground fault occurs and obtain the candidate fault section.

[0008] Based on the line distribution parameters in the topological connection relationship, a distribution function of zero-sequence voltage propagating along the line in the candidate fault section is constructed, and the spatial location of the point in the distribution function that causes the zero-sequence voltage gradient to have an extreme value is solved to obtain the fault location information.

[0009] Based on the fault feature vector corresponding to the fault location information, the grounding fault type and grounding transition resistance state are identified, a fault handling instruction is generated and transmitted to the section isolation device corresponding to the fault location information to perform fault isolation operation.

[0010] Based on the zero-sequence component data, the transient waveforms of zero-sequence current and zero-sequence voltage are extracted, the zero-sequence component of the ground fault is calculated, and time-frequency joint analysis is performed to obtain a fault feature vector reflecting the impedance characteristics of the grounding path, including:

[0011] The zero-sequence current and zero-sequence voltage in the zero-sequence component data are sampled synchronously. The transient waveforms of the zero-sequence current and zero-sequence voltage at each monitoring point before and after the fault triggering time are extracted, and the difference sequence between them and the steady-state waveform is calculated to obtain the zero-sequence component of the ground fault.

[0012] A time-frequency joint analysis is performed on the zero-sequence component of the ground fault. The amplitude and phase of the zero-sequence current and zero-sequence voltage are extracted in the time domain, and the decay time constant is calculated. The amplitude distribution and phase distribution of its characteristic harmonic components are extracted in the frequency domain. The feature parameters extracted in the time domain and the feature parameters extracted in the frequency domain are correlated and mapped in time and frequency to obtain a time-frequency fusion feature set.

[0013] Based on the transient waveforms of the zero-sequence current and the zero-sequence voltage during the fault duration, the instantaneous impedance value of the grounding path is calculated according to the time series. The distribution trajectory of the instantaneous impedance value on the complex plane is extracted to obtain impedance trajectory characteristic parameters that reflect the dynamic characteristics of the grounding transition resistance and the grounding arc.

[0014] The time-frequency fusion feature set and the impedance trajectory feature parameters are concatenated to obtain the fault feature vector.

[0015] Based on the fault feature vector and the topological connectivity, the directional distribution and amplitude attenuation patterns among the monitoring points are extracted, the boundary nodes where grounding faults occur are calculated, and candidate fault sections are obtained, including:

[0016] From the fault feature vector, the zero-sequence current amplitude information and zero-sequence voltage phase information of each monitoring point are extracted. Based on the connection path between each monitoring point in the topological connection relationship, the flow direction of the zero-sequence current between adjacent monitoring points is calculated, and the phase relationship of the zero-sequence voltage at adjacent monitoring points is compared to determine the transmission direction of the zero-sequence power on the connection path, thereby obtaining the directional distribution between each monitoring point.

[0017] Based on the zero-sequence current amplitude information of each monitoring point, the spatial gradient of the zero-sequence current amplitude is calculated along the connection path, the attenuation rate of the zero-sequence current amplitude along the connection path is extracted, and the attenuation rate is correlated and mapped with the line length of the connection path to obtain the amplitude attenuation law.

[0018] Based on the directional distribution among the monitoring points and the amplitude attenuation law, a pair of monitoring points is identified where the zero-sequence current converges from multiple paths and the amplitude attenuation rate changes abruptly, and the monitoring point pair is determined as a boundary node.

[0019] Based on the connection path, the line segments between the boundary nodes are extracted as candidate fault segments.

[0020] Based on the zero-sequence current amplitude information at each monitoring point, the spatial gradient of the zero-sequence current amplitude is calculated along the connection path. The attenuation rate of the zero-sequence current amplitude along the connection path is extracted, and the attenuation rate is correlated and mapped with the line length of the connection path to obtain the amplitude attenuation law, including:

[0021] The monitoring points are arranged along the connection path, the spatial coordinates of each monitoring point on the connection path are recorded, the spatial interval distance between adjacent monitoring points is calculated, and the amplitude difference of the zero-sequence current amplitude between adjacent monitoring points is calculated based on the zero-sequence current amplitude information of each monitoring point and divided by the corresponding spatial interval distance to obtain the spatial gradient sequence.

[0022] Curve fitting is performed on the spatial gradient sequence to obtain the gradient function, and integral operation is performed on it along the spatial coordinates to obtain the cumulative attenuation distribution function, and the attenuation rate of the zero-sequence current amplitude is calculated.

[0023] Extract the line length of the connection path and calculate the total attenuation over the entire length of the connection path. Establish the correlation mapping relationship between the attenuation rate, the line length and the total attenuation to form an amplitude attenuation law.

[0024] Based on the line distribution parameters in the topological connection relationship, a distribution function of the zero-sequence voltage propagating along the line in the candidate fault section is constructed. The spatial location of the point in the distribution function that causes the zero-sequence voltage gradient to have an extreme value is solved to obtain the fault location information, including:

[0025] From the topological connection relationship, the line distribution parameters corresponding to the candidate fault section are extracted. The line distribution parameters include the line resistance parameter per unit length, the line inductance parameter, and the line-to-ground capacitance parameter.

[0026] Obtain the zero-sequence voltage and zero-sequence current measurements at the boundary nodes at both ends of the candidate fault section, and use them as boundary constraints for solving the distribution function;

[0027] Based on the line distribution parameters, a propagation differential relationship of zero-sequence voltage along the spatial coordinates of the candidate fault section is established. The boundary constraint conditions are substituted into the propagation differential relationship for integration to obtain a distribution function describing the value of zero-sequence voltage at any spatial location within the candidate fault section.

[0028] The distribution function is spatially differentiated to obtain a zero-sequence voltage gradient sequence and its first-order spatial derivative field is constructed. The positions of the extreme points with zero curvature in the first-order spatial derivative field are extracted, and the voltage jump amplitude of the distribution function at the corresponding positions is calculated. The extreme point positions where the voltage jump amplitude exceeds the jump threshold are used as fault location information.

[0029] Based on the line distribution parameters, a propagation differential relationship of zero-sequence voltage along the spatial coordinates of the candidate fault section is established. The boundary constraints are substituted into the propagation differential relationship for integration to obtain a distribution function describing the value of zero-sequence voltage at any spatial location within the candidate fault section, including:

[0030] Based on the line-to-ground capacitance parameter in the line distribution parameters, the candidate fault section is divided into multiple sub-segments, and the corresponding line distribution parameters are substituted into the physical law of zero-sequence voltage propagation to establish a differential correlation expression between the first and second derivatives of zero-sequence voltage with respect to spatial coordinates, thereby obtaining the propagation differential relationship of each sub-segment.

[0031] Starting from the beginning position of the first sub-segment, the boundary constraints are substituted into the propagation differential relation of the first sub-segment, and integration is performed along the positive direction of spatial coordinates to obtain the forward propagation function of each sub-segment. Starting from the end position of the last sub-segment, the boundary constraints are substituted into the propagation differential relation of the last sub-segment, and integration is performed along the negative direction of spatial coordinates to obtain the backward propagation function of each sub-segment. The integral difference between the forward propagation function at the beginning position of each sub-segment and the backward propagation function is calculated.

[0032] Select the sub-segment with the smallest integral difference as the target sub-segment, adjust the boundary constraints according to its corresponding integral difference, and repeat the forward integration operation and the backward integration operation until the integral difference of the target sub-segment converges to the convergence threshold.

[0033] After the numerical difference converges, the forward propagation function and the backward propagation function are smoothly connected at the beginning of the target sub-segment to obtain the distribution function of the entire candidate fault segment.

[0034] Based on the fault feature vector corresponding to the fault location information, the ground fault type and ground transition resistance state are identified, a fault handling command is generated and transmitted to the section isolation device corresponding to the fault location information, and a fault isolation operation is performed, including:

[0035] Based on the fault feature vector corresponding to the fault location information, calculate the phase difference between the zero-sequence current and the zero-sequence voltage, and preliminarily determine the ground fault type based on the phase difference.

[0036] From the impedance trajectory characteristic parameters of the fault feature vector, the real and imaginary components of the zero-sequence impedance are extracted. Based on the ratio of the real and imaginary components, the resistance estimation result of the transition resistance in the grounding loop is calculated. The resistance estimation result is compared with the preset metallic grounding resistance benchmark to identify the grounding transition resistance status.

[0037] Based on the fault feature vector, the amplitude of the fundamental component and the amplitude of the higher harmonic components are extracted, and their amplitude ratio is calculated. According to the amplitude ratio, it is determined whether the ground fault is accompanied by an arc discharge phenomenon. If so, the ground fault type is corrected to arc grounding, and the corrected ground fault type is obtained.

[0038] Based on the corrected ground fault type and the ground transition resistance state, the execution priority of the fault isolation operation is determined, and a fault handling instruction is generated. The fault handling instruction is combined with the fault location information to form an isolation control message.

[0039] The isolation control message is transmitted to the section isolation device corresponding to the fault location information through the communication network. After receiving the isolation control message, the section isolation device parses the fault handling instruction and performs the fault isolation operation.

[0040] A second aspect of the present invention provides a system for locating and analyzing grounding faults in transmission lines, comprising:

[0041] The first unit is used to acquire zero-sequence component data and topological connection relationships of multiple monitoring points in the transmission line;

[0042] The second unit is used to extract the transient waveforms of zero-sequence current and zero-sequence voltage based on the zero-sequence component data, calculate the zero-sequence component of the ground fault and perform time-frequency joint analysis to obtain a fault feature vector that reflects the impedance characteristics of the grounding path.

[0043] The third unit is used to calculate the boundary node where the ground fault occurs and obtain the candidate fault section based on the directional distribution and amplitude attenuation law between each monitoring point in the topological connection relationship of the fault feature vector.

[0044] The fourth unit is used to construct a distribution function of the zero-sequence voltage propagating along the line in the candidate fault section based on the line distribution parameters in the topological connection relationship, solve the spatial location of the point in the distribution function that causes the zero-sequence voltage gradient to have an extreme value, and obtain the fault location information.

[0045] The fifth unit is used to identify the grounding fault type and grounding transition resistance state based on the fault feature vector corresponding to the fault location information, generate a fault handling command and transmit it to the section isolation device corresponding to the fault location information to perform fault isolation operation.

[0046] A third aspect of the embodiments of the present invention,

[0047] An electronic device is provided, comprising:

[0048] processor;

[0049] Memory used to store processor-executable instructions;

[0050] The processor is configured to invoke instructions stored in the memory to execute the aforementioned method.

[0051] Fourth aspect of the present invention,

[0052] A computer-readable storage medium is provided, having stored thereon computer program instructions that, when executed by a processor, implement the aforementioned method.

[0053] The beneficial effects of this application are as follows:

[0054] This invention obtains zero-sequence component data and topological connection relationships from multiple monitoring points of transmission lines, and extracts fault feature vectors that reflect the impedance characteristics of grounding paths, making fault location more accurate. The location results are less susceptible to interference from external environmental factors, and the reliability and stability are significantly improved.

[0055] This invention calculates candidate fault sections based on the directional distribution and amplitude attenuation law of fault feature vectors in topological connections, and locates the fault location by using the extreme point of the zero-sequence voltage gradient, thereby achieving rapid and accurate fault location, significantly improving fault handling efficiency, and reducing power outage time and maintenance costs.

[0056] This invention can identify the type of ground fault and the state of ground transition resistance, automatically generate fault handling instructions and execute isolation operations, effectively improve the automation level of the power grid, reduce human intervention, enhance the safe operation capability and anti-interference capability of the transmission line system, and ensure the reliability of power supply. Attached Figure Description

[0057] Figure 1 This is a flowchart illustrating the method for locating and analyzing grounding faults in transmission lines according to an embodiment of the present invention.

[0058] Figure 2 This is a schematic diagram of the technical architecture for locating ground fault sections in a distribution network based on monitoring data. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0060] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0061] Figure 1 This is a flowchart illustrating the method for locating and analyzing grounding faults in transmission lines according to an embodiment of the present invention. Figure 1 As shown, the method includes:

[0062] Acquire zero-sequence component data and topological connectivity relationships from multiple monitoring points in a transmission line;

[0063] Based on the zero-sequence component data, the transient waveforms of zero-sequence current and zero-sequence voltage are extracted, the zero-sequence component of the ground fault is calculated and time-frequency joint is performed to obtain the fault feature vector reflecting the impedance characteristics of the grounding path.

[0064] Based on the fault feature vector in the topological connection relationship, the directional distribution and amplitude attenuation law between each monitoring point are used to calculate the boundary node where the ground fault occurs and obtain the candidate fault section.

[0065] Based on the line distribution parameters in the topological connection relationship, a distribution function of zero-sequence voltage propagating along the line in the candidate fault section is constructed, and the spatial location of the point in the distribution function that causes the zero-sequence voltage gradient to have an extreme value is solved to obtain the fault location information.

[0066] Based on the fault feature vector corresponding to the fault location information, the grounding fault type and grounding transition resistance state are identified, a fault handling instruction is generated and transmitted to the section isolation device corresponding to the fault location information to perform fault isolation operation.

[0067] In one optional implementation, based on the zero-sequence component data, the transient waveforms of zero-sequence current and zero-sequence voltage are extracted, the zero-sequence component of the ground fault is calculated and time-frequency coupled to obtain a fault feature vector reflecting the impedance characteristics of the grounding path, including:

[0068] The zero-sequence current and zero-sequence voltage in the zero-sequence component data are sampled synchronously. The transient waveforms of the zero-sequence current and zero-sequence voltage at each monitoring point before and after the fault triggering time are extracted, and the difference sequence between them and the steady-state waveform is calculated to obtain the zero-sequence component of the ground fault.

[0069] A time-frequency joint analysis is performed on the zero-sequence component of the ground fault. The amplitude and phase of the zero-sequence current and zero-sequence voltage are extracted in the time domain, and the decay time constant is calculated. The amplitude distribution and phase distribution of its characteristic harmonic components are extracted in the frequency domain. The feature parameters extracted in the time domain and the feature parameters extracted in the frequency domain are correlated and mapped in time and frequency to obtain a time-frequency fusion feature set.

[0070] Based on the transient waveforms of the zero-sequence current and the zero-sequence voltage during the fault duration, the instantaneous impedance value of the grounding path is calculated according to the time series. The distribution trajectory of the instantaneous impedance value on the complex plane is extracted to obtain impedance trajectory characteristic parameters that reflect the dynamic characteristics of the grounding transition resistance and the grounding arc.

[0071] The time-frequency fusion feature set and the impedance trajectory feature parameters are concatenated to obtain the fault feature vector.

[0072] In this specific implementation, zero-sequence component data needs to be obtained from the power distribution network monitoring system. This data includes zero-sequence current and zero-sequence voltage information at each monitoring point. The data acquisition process is initiated when a ground fault is detected.

[0073] The acquired zero-sequence component data is processed, and the transient waveforms of zero-sequence current and zero-sequence voltage are extracted using synchronous sampling technology. The sampling frequency is set to 10kHz to ensure that high-frequency transient processes are captured. A data window of 200ms is taken before and after the fault occurrence time to form a complete record of the transient process. In specific implementation, 100ms is traced back from the fault trigger point t0 and 300ms is extended forward, for a total of 400ms of data window is acquired. For example, in a single-phase ground fault, the fault triggering condition is detected to be met at t0=12:45:36.782, and the zero-sequence current and zero-sequence voltage data in the time period from 12:45:36.682 to 12:45:37.082 are then captured.

[0074] The collected waveform during the fault period is differentially calculated with the steady-state waveform before the fault to extract the pure fault component. The steady-state waveform is obtained by averaging the data of the five cycles before the fault. Taking a real case as an example, a 10kV distribution line experiences a phase A ground fault. The steady-state value of the zero-sequence current before the fault is about 0.5A. After the fault is triggered, the instantaneous peak value reaches 120A. The peak value of the zero-sequence component of the fault obtained by differential calculation is about 119.5A, and it decays according to the damped oscillation mode.

[0075] The extracted zero-sequence components of the ground fault are subjected to time-frequency joint analysis. In the time domain, the amplitude envelopes and phase change curves of the zero-sequence current and zero-sequence voltage are calculated. For the amplitude envelope, the peak point of the waveform is extracted using the sliding window method. The window width is half a power frequency cycle, i.e., 10ms. The phase is calculated by the time difference between the zero-sequence current and zero-sequence voltage crossing the zero point simultaneously. Taking a certain metallic ground fault as an example, the initial phase of the zero-sequence current is -85° and the initial phase of the zero-sequence voltage is 95°. The phase difference between the two is about 180°, which is consistent with the electrical characteristics of a metallic ground fault.

[0076] Simultaneously, the decay time constant of the transient process is calculated, and the amplitude envelope is fitted using the exponential fitting method to obtain the decay characteristic parameters. In the above case, the decay time constant of the zero-sequence current is about 75ms, indicating that the transient process of the line has a short duration and the grounding point impedance is small.

[0077] In terms of frequency domain analysis, Fast Fourier Transform is applied to the zero-sequence component of the fault to extract the amplitude and phase distribution of its harmonic components. The focus is on the characteristics of the fundamental (50Hz), the third harmonic (150Hz), the fifth harmonic (250Hz), and the high-frequency oscillation components (usually between 300Hz and 2kHz). For example, in the aforementioned case, the spectrum analysis of the zero-sequence current shows that the fundamental component is dominant (about 85%), the third harmonic accounts for about 10%, the fifth harmonic accounts for about 3%, and the remaining high-frequency components account for about 2%.

[0078] By mapping and fusing time-domain features with frequency-domain features, a time-frequency fusion feature set is constructed. The feature set includes: peak amplitude in the time domain, decay time constant, initial phase angle, and amplitude ratio and phase difference of each harmonic in the frequency domain. For example, the initial amplitude of zero-sequence current of 120A, decay time constant of 75ms, initial phase of -85°, and parameters such as the proportion of fundamental wave in the frequency domain of 85% and the proportion of third harmonic wave of 10% are combined into a 16-dimensional feature vector.

[0079] During the fault duration, the instantaneous impedance of the grounding path is calculated based on the instantaneous values ​​of the sampled zero-sequence current and zero-sequence voltage. The calculation formula is the instantaneous value of the zero-sequence voltage divided by the instantaneous value of the zero-sequence current. The calculated impedance value is then plotted on the complex plane according to its real and imaginary parts. For metallic grounding faults, the impedance trajectory presents a small circular area with a radius typically less than 5 ohms; while for high-resistance faults, the trajectory presents a larger elliptical or irregular shape with a radius reaching tens to hundreds of ohms.

[0080] The impedance trajectory is subjected to morphological feature extraction, and the geometric feature parameters of the trajectory are calculated, including the area, perimeter, circularity, principal axis direction and major-minor axis ratio, etc. For example, in a certain arc grounding fault, the impedance trajectory presents a typical figure-eight shape, with an area of ​​about 500 square ohms, a major-minor axis ratio of 3:1, and a principal axis direction of about 30°. These features are clearly different from metallic grounding or high-resistance grounding faults.

[0081] The time-frequency fusion feature set and the impedance trajectory feature parameters are spliced ​​together to form a complete fault feature vector. In this embodiment, the feature vector contains 24 parameters, of which the time-frequency fusion feature is 16-dimensional and the impedance trajectory feature is 8-dimensional. This feature vector can effectively distinguish different types of grounding faults, including metallic grounding, high-resistance grounding, arc grounding and intermittent grounding.

[0082] By analyzing the eigenvectors, we can accurately determine the type, severity, and development trend of grounding faults, providing decision support for power distribution network operation and maintenance personnel.

[0083] Figure 2 This is a schematic diagram of a distribution network grounding fault location technology architecture based on monitoring data. In one optional implementation, based on the fault feature vector and the topological connection relationship, the directional distribution and amplitude attenuation law between each monitoring point are extracted, the boundary nodes where the grounding fault occurs are calculated, and candidate fault sections are obtained, including:

[0084] From the fault feature vector, the zero-sequence current amplitude information and zero-sequence voltage phase information of each monitoring point are extracted. Based on the connection path between each monitoring point in the topological connection relationship, the flow direction of the zero-sequence current between adjacent monitoring points is calculated, and the phase relationship of the zero-sequence voltage at adjacent monitoring points is compared to determine the transmission direction of the zero-sequence power on the connection path, thereby obtaining the directional distribution between each monitoring point.

[0085] Based on the zero-sequence current amplitude information of each monitoring point, the spatial gradient of the zero-sequence current amplitude is calculated along the connection path, the attenuation rate of the zero-sequence current amplitude along the connection path is extracted, and the attenuation rate is correlated and mapped with the line length of the connection path to obtain the amplitude attenuation law.

[0086] Based on the directional distribution among the monitoring points and the amplitude attenuation law, a pair of monitoring points is identified where the zero-sequence current converges from multiple paths and the amplitude attenuation rate changes abruptly, and the monitoring point pair is determined as a boundary node.

[0087] Based on the connection path, the line segments between the boundary nodes are extracted as candidate fault segments.

[0088] In practical applications, multiple monitoring devices are deployed in the power distribution network. Each monitoring device can collect the three-phase current and three-phase voltage signals of the node it is located at. When a single-phase ground fault occurs in the network, the measurement data of all monitoring points are collected, and the zero-sequence current amplitude and zero-sequence voltage phase are obtained through symmetrical component transformation. At the same time, the topological connection relationship of the power distribution network is obtained, including the connection path and line parameters between each monitoring point.

[0089] To extract the directional distribution between monitoring points, it is necessary to analyze the direction of zero-sequence current between adjacent monitoring points. For example, for monitoring points A and B, if the zero-sequence current at point A is 2.5 amperes and flows towards point B, while the zero-sequence current at point B is 2.2 amperes and flows away from point A, then it is determined that the direction of the zero-sequence current on the connection path from A to B is from A to B. In addition, by comparing the phase relationship of the zero-sequence voltage at points A and B, if the phase of the zero-sequence voltage at point A is 25 degrees and at point B is 28 degrees, with a phase difference of 3 degrees, it indicates that the zero-sequence voltage is transmitted from point B to point A. Combining the direction of the zero-sequence current and the phase relationship of the zero-sequence voltage, if the zero-sequence current is from A to B and the phase of the zero-sequence voltage is transmitted from B to A, then the direction of the transmission of zero-sequence power on this connection path is from A to B. By performing similar analysis on all adjacent monitoring points, the directional distribution map between monitoring points in the entire network is obtained.

[0090] Regarding the extraction of amplitude attenuation law, the spatial gradient of zero-sequence current amplitude is calculated along the connection path. For example, for monitoring points C and D 500 meters apart, if the zero-sequence current amplitude at point C is 3.0 amperes and at point D is 2.7 amperes, then the attenuation of the zero-sequence current along the path from C to D is 0.3 amperes, corresponding to an attenuation rate of 0.6 amperes per kilometer. Similar calculations are performed on all connection paths in the network to establish a mapping table between the zero-sequence current amplitude attenuation rate and the line length. Under normal circumstances, the zero-sequence current attenuation rate of a specific type of line is relatively stable. For example, the typical attenuation rate of a certain type of overhead line is 0.5-0.7 amperes per kilometer, while that of a cable line is 0.8-1.2 amperes per kilometer.

[0091] During the boundary node identification process, a comprehensive analysis is conducted based on the aforementioned directional distribution and amplitude attenuation patterns to search for monitoring point pairs that meet the following conditions: First, there are nodes where zero-sequence current converges from multiple paths; second, on the lines between these node pairs, the zero-sequence current amplitude attenuation rate undergoes a significant jump. For example, if monitoring point E has zero-sequence current converging from three different directions, and the zero-sequence current attenuation rate on the line between E and the adjacent monitoring point F is 1.5 amperes per kilometer, which is much higher than the typical value of 0.6 amperes per kilometer in other areas of the network, then EF will be identified as a boundary node pair.

[0092] In a specific case, monitoring points G, H, I, and J in a distribution network are connected in a ring network structure. When a single-phase ground fault occurs, the following zero-sequence currents are detected: 4.2 amps at point G pointing towards H; 3.8 amps at point H pointing towards I; 3.5 amps at point I pointing towards J; and 2.2 amps of zero-sequence current pointing towards G and 1.0 amps of zero-sequence current pointing towards I at point J. The line length of segment GH is 600 meters, and the calculated zero-sequence current attenuation rate is 0.67 amps per kilometer; segment HI is 800 meters, and the attenuation rate is 0.38 amps per kilometer; segment IJ is 500 meters, and the attenuation rate is 0.6 amps per kilometer; while segment JG is 700 meters, and the attenuation rate is 2.86 amps per kilometer, significantly higher than other segments. Furthermore, point J is the node where zero-sequence currents converge from two directions. Therefore, JG is identified as a boundary node pair.

[0093] Based on the connection path, the line segments between boundary nodes are extracted as candidate fault segments. In the above case, the JG line segment is identified as a candidate fault segment. If multiple boundary node pairs are identified, multiple corresponding line segments are listed as candidate fault segments. These candidate segments can be further sorted and confirmed by combining other fault information.

[0094] Using the above method, the present invention can effectively utilize distributed monitoring data and combine it with topological relationships to accurately locate single-phase grounding fault sections in the distribution network, improve fault handling efficiency, and reduce power outage time and scope.

[0095] In one optional implementation, based on the zero-sequence current amplitude information of each monitoring point, the spatial gradient of the zero-sequence current amplitude is calculated along the connection path, the attenuation rate of the zero-sequence current amplitude along the connection path is extracted, and the attenuation rate is correlated and mapped with the line length of the connection path to obtain the amplitude attenuation law, including:

[0096] The monitoring points are arranged along the connection path, the spatial coordinates of each monitoring point on the connection path are recorded, the spatial interval distance between adjacent monitoring points is calculated, and the amplitude difference of the zero-sequence current amplitude between adjacent monitoring points is calculated based on the zero-sequence current amplitude information of each monitoring point and divided by the corresponding spatial interval distance to obtain the spatial gradient sequence.

[0097] Curve fitting is performed on the spatial gradient sequence to obtain the gradient function, and integral operation is performed on it along the spatial coordinates to obtain the cumulative attenuation distribution function, and the attenuation rate of the zero-sequence current amplitude is calculated.

[0098] Extract the line length of the connection path and calculate the total attenuation over the entire length of the connection path. Establish the correlation mapping relationship between the attenuation rate, the line length and the total attenuation to form an amplitude attenuation law.

[0099] In this specific embodiment, it is necessary to obtain the zero-sequence current amplitude information and its connection path of each monitoring point in the power distribution network. For example, on a certain 10kV power distribution line, five zero-sequence current monitoring devices are installed, located at the substation outgoing line, branch box No. 2, ring network cabinet No. 3, ring network cabinet No. 4 and branch box No. 5 respectively. These points constitute a connection path.

[0100] The monitoring points are arranged in an orderly manner along the connection path, and the spatial coordinates of each point are recorded. In practical applications, the spatial coordinates can be represented by the cumulative distance along the line from the starting point of the distribution network (such as the outgoing line of the substation). For example, the spatial coordinates of the above 5 monitoring points are 0 meters, 500 meters, 1200 meters, 2000 meters and 2800 meters respectively.

[0101] Calculate the spatial distance between adjacent monitoring points. Based on the coordinates above, the distance between point 1 and point 2 is 500 meters, the distance between point 2 and point 3 is 700 meters, the distance between point 3 and point 4 is 800 meters, and the distance between point 4 and point 5 is 800 meters.

[0102] Based on the zero-sequence current amplitude information at each monitoring point, the difference in zero-sequence current amplitude between adjacent monitoring points is calculated. Assuming the zero-sequence current amplitudes measured at the five monitoring points are 50 amps, 42 amps, 32 amps, 22 amps, and 15 amps, the amplitude differences between adjacent points are 8 amps, 10 amps, 10 amps, and 7 amps, respectively.

[0103] Dividing the amplitude difference by the corresponding spatial interval distance yields the spatial gradient sequence of the zero-sequence current amplitude. Based on the above data, the spatial gradient sequences are 0.016 A / m (8 A / m ÷ 500 m), 0.0143 A / m (10 A / m ÷ 700 m), 0.0125 A / m (10 A / m ÷ 800 m), and 0.00875 A / m (7 A / m ÷ 800 m).

[0104] Curve fitting is performed on the spatial gradient sequence to obtain the gradient function. In this embodiment, a polynomial fitting method is used. The obtained gradient function can be expressed as a function of spatial coordinate x. The fitting results show that as the distance increases, the spatial gradient of the zero-sequence current amplitude gradually decreases, which is consistent with the attenuation characteristics of current transmission in the line.

[0105] Integrating the gradient function along spatial coordinates yields the cumulative attenuation distribution function, which describes the cumulative attenuation of the zero-sequence current amplitude from the starting point (the substation outgoing line) to any location x. For example, the cumulative attenuation is 8 amperes at 500 meters from the starting point, 18 amperes at 1200 meters from the starting point, and so on.

[0106] The attenuation rate of the zero-sequence current amplitude is calculated. The attenuation rate can be expressed as the relative decrease in the zero-sequence current amplitude per unit distance. According to the cumulative attenuation distribution function, the average attenuation rate is calculated to be 0.032 in the 0-500 meter range (i.e., 3.2% of the original value per meter), 0.034 in the 500-1200 meter range, 0.039 in the 1200-2000 meter range, and 0.040 in the 2000-2800 meter range.

[0107] The length of the connection path is extracted; in this embodiment, the total length of the connection path is 2800 meters. The total attenuation over the entire length of the connection path is calculated, i.e., the change in zero-sequence current amplitude from the starting point to the ending point. Based on the aforementioned data, the total attenuation is 35 amperes (50 amperes - 15 amperes).

[0108] A correlation mapping relationship was established between attenuation rate, line length and total attenuation to form an amplitude attenuation law. Through analysis, it was found that in this distribution line, the total attenuation of zero-sequence current amplitude is positively correlated with the line length, with an average attenuation of about 12.5 amperes of zero-sequence current per kilometer of line. In addition, the attenuation rate increases slightly with the increase of distance, indicating that the attenuation of zero-sequence current is more obvious in areas far away from the fault source.

[0109] This amplitude attenuation law can be applied to fault location. For example, when a single-phase ground fault is detected in a power distribution line, the location of the fault point can be estimated by analyzing the zero-sequence current amplitude at each monitoring point and combining it with the established amplitude attenuation law. If the zero-sequence current attenuation between two monitoring points is significantly greater than the value expected according to the attenuation law, then the fault point is located between these two monitoring points.

[0110] This method enables precise analysis of the propagation characteristics of zero-sequence current in power distribution networks, improving the accuracy of single-phase grounding fault location, reducing outage time, and enhancing the reliability and operational efficiency of power distribution networks.

[0111] In one optional implementation, based on the line distribution parameters in the topological connection relationship, a distribution function of the zero-sequence voltage propagating along the line within the candidate fault section is constructed. The spatial locations of the extreme points of the zero-sequence voltage gradient in the distribution function are then solved to obtain fault location information, including:

[0112] From the topological connection relationship, the line distribution parameters corresponding to the candidate fault section are extracted. The line distribution parameters include the line resistance parameter per unit length, the line inductance parameter, and the line-to-ground capacitance parameter.

[0113] Obtain the zero-sequence voltage and zero-sequence current measurements at the boundary nodes at both ends of the candidate fault section, and use them as boundary constraints for solving the distribution function;

[0114] Based on the line distribution parameters, a propagation differential relationship of zero-sequence voltage along the spatial coordinates of the candidate fault section is established. The boundary constraint conditions are substituted into the propagation differential relationship for integration to obtain a distribution function describing the value of zero-sequence voltage at any spatial location within the candidate fault section.

[0115] The distribution function is spatially differentiated to obtain a zero-sequence voltage gradient sequence and its first-order spatial derivative field is constructed. The positions of the extreme points with zero curvature in the first-order spatial derivative field are extracted, and the voltage jump amplitude of the distribution function at the corresponding positions is calculated. The extreme point positions where the voltage jump amplitude exceeds the jump threshold are used as fault location information.

[0116] In practical implementation, it is necessary to clarify the topological connection relationship of the power distribution network. This topological relationship includes the spatial distribution information of the line segments and the connection method between each node. In the topological structure, the line is usually divided into multiple segments, and each segment is connected by two adjacent nodes. For example, a 10kV power distribution line contains 5 segments, which are interconnected by 6 nodes. Node 1 is the substation outgoing line point, and nodes 2 to 6 are the key connection points on the line.

[0117] When a line fault occurs, the candidate fault section will be initially determined by the operation of the fault indicator and protection device. To illustrate with a specific case, suppose a single-phase ground fault is detected in the line section between node 3 and node 4. The length of this candidate fault section is 2000 meters. Now it is necessary to determine the specific location of the fault.

[0118] Extracting the line distribution parameters of candidate fault sections from the topological connection relationship is the basis for localization. For the line section from node 3 to node 4, its zero-sequence resistance per unit length is 0.58 ohms / km, zero-sequence inductance is 3.92 millihenries / km, and capacitance to ground is 0.0062 microfarads / km. These parameters reflect the physical characteristics of the line and are key elements for constructing the voltage propagation function.

[0119] The zero-sequence voltage and zero-sequence current measurements at the boundary nodes at both ends of the candidate fault section are obtained. At node 3, the measured zero-sequence voltage amplitude is 4.5 kV with a phase angle of -15 degrees; the zero-sequence current amplitude is 35 A and the phase angle is 165 degrees. At node 4, the zero-sequence voltage amplitude is 2.8 kV with a phase angle of -25 degrees; the zero-sequence current amplitude is 28 A and the phase angle is 155 degrees. These measurements are used as boundary constraints for subsequent distribution function solving.

[0120] Based on the line distribution parameters, establishing the propagation differential relationship of zero-sequence voltage along the spatial coordinates of candidate fault sections is a key step. This relationship describes how the zero-sequence voltage changes with spatial location under healthy conditions. The propagation differential relationship considers the influence of resistance, inductance, and capacitance on the propagation of zero-sequence voltage, and is embodied in the second-order differential equation of zero-sequence voltage with respect to spatial location. For the line section from node 3 to node 4, the origin of the spatial coordinates is set to node 3, the positive direction of the coordinates points to node 4, and the coordinate range is 0 to 2000 meters.

[0121] Substituting the boundary constraints into the propagation differential relation and performing integration, we obtain the distribution function describing the zero-sequence voltage at any spatial location within the candidate fault section. This integration process is essentially solving a second-order differential equation. The specific form of the solution is determined by the boundary conditions. In this case, a numerical integration method is used, with a step size of 10 meters, to calculate the zero-sequence voltage value at each point within the line section. For example, the zero-sequence voltage amplitude at 600 meters from the starting point of node 3 is 4.2 kV with a phase angle of -16 degrees; the zero-sequence voltage amplitude at 1200 meters is 3.7 kV with a phase angle of -18 degrees.

[0122] By spatially differentiating the distribution function, the zero-sequence voltage gradient sequence is obtained, and its first-order spatial derivative field is constructed. Continuing with a step size of 10 meters, the spatial derivative values ​​of the zero-sequence voltage at each point on the line are calculated. Under normal circumstances, the zero-sequence voltage gradient should change smoothly along the line, but obvious abnormal changes will occur near the fault point. In this case, from the starting point to 1500 meters, the zero-sequence voltage gradient changes smoothly, with values ​​between -0.9 V / m and -1.2 V / m; however, in the interval between 1520 meters and 1540 meters, the gradient value suddenly becomes -5.8 V / m, and then returns to around -1.1 V / m.

[0123] To extract the location of the extremum point with zero curvature in the first-order spatial derivative field, it is necessary to calculate the rate of change of the zero-sequence voltage gradient. In this example, at a distance of 1530 meters from the starting point, the rate of change of the zero-sequence voltage gradient changes from negative to zero and then to positive, forming an extremum point. At this location, the jump amplitude of the zero-sequence voltage reaches 680 volts, far exceeding the set jump threshold of 400 volts.

[0124] Therefore, the location 1530 meters from the starting point of node 3 (i.e., 470 meters from the ending point of node 4) was determined as the fault location, and this information was output to the maintenance personnel to guide the on-site repair work. The actual repair results confirmed that there was indeed a single-phase ground fault caused by a tree branch touching the line at this location, which verified the accuracy of this method.

[0125] Compared with the traditional impedance ranging method, this method can effectively overcome the influence of distributed capacitance and improve the positioning accuracy. It is especially suitable for fault location of mixed cable and overhead lines. In practical applications, this method can be integrated into the power distribution automation system to achieve rapid and accurate fault location, significantly shorten fault outage time, and improve power supply reliability.

[0126] In one optional implementation, based on the line distribution parameters, a propagation differential relationship of the zero-sequence voltage along the spatial coordinates of the candidate fault section is established. The boundary constraints are substituted into the propagation differential relationship for integration to obtain a distribution function describing the value of the zero-sequence voltage at any spatial location within the candidate fault section, including:

[0127] Based on the line-to-ground capacitance parameter in the line distribution parameters, the candidate fault section is divided into multiple sub-segments, and the corresponding line distribution parameters are substituted into the physical law of zero-sequence voltage propagation to establish a differential correlation expression between the first and second derivatives of zero-sequence voltage with respect to spatial coordinates, thereby obtaining the propagation differential relationship of each sub-segment.

[0128] Starting from the beginning position of the first sub-segment, the boundary constraints are substituted into the propagation differential relation of the first sub-segment, and integration is performed along the positive direction of spatial coordinates to obtain the forward propagation function of each sub-segment. Starting from the end position of the last sub-segment, the boundary constraints are substituted into the propagation differential relation of the last sub-segment, and integration is performed along the negative direction of spatial coordinates to obtain the backward propagation function of each sub-segment. The integral difference between the forward propagation function at the beginning position of each sub-segment and the backward propagation function is calculated.

[0129] Select the sub-segment with the smallest integral difference as the target sub-segment, adjust the boundary constraints according to its corresponding integral difference, and repeat the forward integration operation and the backward integration operation until the integral difference of the target sub-segment converges to the convergence threshold.

[0130] After the numerical difference converges, the forward propagation function and the backward propagation function are smoothly connected at the beginning of the target sub-segment to obtain the distribution function of the entire candidate fault segment.

[0131] In practical applications of distribution network fault location, the distributed parameters of the line can be obtained, including the line-to-ground capacitance, line resistance, and line inductance. Taking a 10kV distribution line as an example, the line is 15km long, with a line-to-ground capacitance of 0.25μF / km, a line resistance of 0.27Ω / km, and a line inductance of 1.2mH / km. Based on these parameters, the differential relationship of zero-sequence voltage propagation can be established.

[0132] Based on the distribution characteristics of the line-to-ground capacitance parameters, the candidate fault section is divided into multiple sub-segments. In this example, the 15km line is divided into 5 sub-segments, each 3km long. For each sub-segment, based on its corresponding line distribution parameters, the differential relationship expression between the first and second derivatives of the zero-sequence voltage with respect to spatial coordinates is established using the physical law of zero-sequence voltage propagation. For example, for the first sub-segment (0-3km), there is a relationship between the second and first derivatives of its zero-sequence voltage U(x) with respect to spatial coordinate x. This relationship is determined by the line-to-ground capacitance, line resistance, and line inductance of the sub-segment, thus obtaining the propagation differential relationship of the first sub-segment. Similarly, the propagation differential relationships of the other four sub-segments can be obtained.

[0133] The boundary constraints include the zero-sequence voltage and zero-sequence current values ​​at both ends of the candidate fault section. It is assumed that the zero-sequence voltage is 100V and the zero-sequence current is 5A at the beginning of the line (x=0); and the zero-sequence voltage is 20V and the zero-sequence current is 1A at the end of the line (x=15km). These boundary constraints will be used for integration calculations.

[0134] Starting from the initial position of the first sub-segment (x=0), the boundary constraints (zero-sequence voltage of 100V and zero-sequence current of 5A) are substituted into the propagation differential relation of the first sub-segment. Integration is performed along the positive direction of the spatial coordinates using the Runge-Kutta method with a step size of 0.1km. Through iterative calculation, the zero-sequence voltage values ​​at all spatial locations within the first sub-segment are obtained, forming the forward propagation function of the first sub-segment. When the calculation reaches the end point of the first sub-segment (x=3km), the obtained zero-sequence voltage and zero-sequence current values ​​will be used as the boundary conditions for the starting point of the second sub-segment. The forward integration is then performed, and so on, until the forward propagation functions of all five sub-segments are obtained.

[0135] Starting from the end position of the last sub-segment (x=15km), the boundary constraints (zero-sequence voltage of 20V and zero-sequence current of 1A) are substituted into the propagation differential relation of the last sub-segment (the fifth sub-segment). Integration is performed in reverse along the spatial coordinates, using the Runge-Kutta method with a step size of 0.1km. Through iterative calculation, the zero-sequence voltage values ​​at all spatial locations within the fifth sub-segment are obtained, forming the backpropagation function of the fifth sub-segment. When the calculation reaches the starting point of the fifth sub-segment (x=12km), the obtained zero-sequence voltage and zero-sequence current values ​​are used as the boundary conditions for the end point of the fourth sub-segment, and the reverse integration is continued. This process is repeated until the backpropagation functions of all five sub-segments are obtained.

[0136] Calculate the integral difference between the forward propagation function and the backward propagation function at the starting position of each sub-segment. For example, at the starting position of the first sub-segment (x=0), the zero-sequence voltage value given by the forward propagation function is 100V, and the zero-sequence voltage value given by the backward propagation function is 105V, with an integral difference of 5V. At the starting position of the second sub-segment (x=3km), the integral difference is 3V. At the starting position of the third sub-segment (x=6km), the integral difference is 0.5V. At the starting position of the fourth sub-segment (x=9km), the integral difference is 2V. At the starting position of the fifth sub-segment (x=12km), the integral difference is 4V.

[0137] The sub-segment with the smallest integral difference is selected as the target sub-segment, which in this example is the third sub-segment (6-9km), with an integral difference of 0.5V. The boundary constraints are adjusted based on this difference. For example, the zero-sequence voltage at the beginning of the line is adjusted to 102V and the zero-sequence current is adjusted to 5.2A; the zero-sequence voltage at the end of the line is adjusted to 19V and the zero-sequence current is adjusted to 0.9A. The forward integration and reverse integration operations are repeated, and the integral difference at the beginning position of each sub-segment is calculated again.

[0138] After adjustment, the integral difference at the beginning of the third sub-segment decreases to 0.2V. The above adjustment process continues until the integral difference of the third sub-segment converges to the preset convergence threshold (e.g., 0.05V). In this example, after 5 iterations, the integral difference of the third sub-segment drops to 0.04V, meeting the convergence requirement.

[0139] After the numerical difference converges, the forward propagation function and the backward propagation function are smoothly connected at the starting position (x=6km) of the target sub-segment (third sub-segment). Specifically, at x=6km, a weighted average method is used to make the connection between the two functions smooth and avoid jumps. The connected function is the zero-sequence voltage distribution function of the entire candidate fault segment (0-15km).

[0140] This distribution function can be used to calculate the zero-sequence voltage value at any spatial location within the candidate fault section. For example, at x=7.5km (the middle of the third sub-section), the calculated zero-sequence voltage value is 65V. This distribution function provides an important basis for subsequent fault location analysis.

[0141] In one optional implementation, based on the fault feature vector corresponding to the fault location information, the ground fault type and ground transition resistance state are identified, a fault handling command is generated and transmitted to the section isolation device corresponding to the fault location information, and a fault isolation operation is performed, including:

[0142] Based on the fault feature vector corresponding to the fault location information, calculate the phase difference between the zero-sequence current and the zero-sequence voltage, and preliminarily determine the ground fault type based on the phase difference.

[0143] From the impedance trajectory characteristic parameters of the fault feature vector, the real and imaginary components of the zero-sequence impedance are extracted. Based on the ratio of the real and imaginary components, the resistance estimation result of the transition resistance in the grounding loop is calculated. The resistance estimation result is compared with the preset metallic grounding resistance benchmark to identify the grounding transition resistance status.

[0144] Based on the fault feature vector, the amplitude of the fundamental component and the amplitude of the higher harmonic components are extracted, and their amplitude ratio is calculated. According to the amplitude ratio, it is determined whether the ground fault is accompanied by an arc discharge phenomenon. If so, the ground fault type is corrected to arc grounding, and the corrected ground fault type is obtained.

[0145] Based on the corrected ground fault type and the ground transition resistance state, the execution priority of the fault isolation operation is determined, and a fault handling instruction is generated. The fault handling instruction is combined with the fault location information to form an isolation control message.

[0146] The isolation control message is transmitted to the section isolation device corresponding to the fault location information through the communication network. After receiving the isolation control message, the section isolation device parses the fault handling instruction and performs the fault isolation operation.

[0147] In this specific embodiment, by acquiring fault location information and corresponding fault feature vectors in the power distribution network, accurate ground fault type identification and processing are performed. The phase difference between zero-sequence current and zero-sequence voltage is calculated to initially determine the ground fault type. In practical applications, the phasor values ​​of zero-sequence current I0 and zero-sequence voltage U0 are acquired, and the phase angle difference φ between them is calculated. For example, when φ is close to 0° (e.g., φ≤5°), it is determined to be metallic direct grounding; when φ is close to 90° (e.g., 85°≤φ≤95°), it is capacitive grounding; when φ is close to -90° (e.g., -95°≤φ≤-85°), it is determined to be inductive grounding; when φ falls in other ranges, such as 30°≤φ≤60° or -60°≤φ≤-30°, it is determined to be resistive grounding.

[0148] Further, zero-sequence impedance parameters, including the real part R0 and the imaginary part X0 of the zero-sequence impedance, are extracted from the fault feature vector. By calculating the ratio γ=R0 / |X0| of R0, the transition resistance value R in the grounding loop can be estimated. fFor example, when γ is less than a preset threshold (e.g., γ < 0.1), it indicates that the transition resistance is small and close to metallic grounding; when 0.1 ≤ γ < 0.5, it indicates that there is a moderate degree of transition resistance; when γ ≥ 0.5, it indicates that the transition resistance value is large. This estimated result is compared with the preset metallic grounding resistance value benchmark (e.g., 0.5Ω). When the estimated transition resistance value is less than the benchmark, it is identified as a metallic grounding state; otherwise, it is identified as a transition resistance grounding state.

[0149] To further improve identification accuracy, based on the fault feature vector, the amplitudes of the fundamental component I1 and higher harmonic components (such as the 3rd harmonic I3, the 5th harmonic I5, etc.) of the current signal are extracted, and the amplitude ratio of the higher harmonics to the fundamental is calculated, such as η3=I3 / I1 and η5=I5 / I1. When these ratios exceed preset thresholds (such as η3>0.08 or η5>0.05), it is determined that the ground fault is accompanied by arc discharge phenomenon, and the initially determined ground fault type is corrected to arc grounding. For example, if it is initially determined to be metallic direct grounding, but significant harmonic characteristics are detected (η3=0.12), it is corrected to arc metallic grounding.

[0150] After determining the fault type and transition resistance status, the execution order of fault isolation operations is determined according to preset priority rules. For example, direct metallic grounding has the highest priority (priority 1), followed by arcing metallic grounding (priority 2), then resistive grounding (priority 3), and capacitive and inductive grounding have lower priorities (priority 4 and 5). Based on this, fault handling instructions are generated, including operation type (such as "isolation disconnection", "reclosing", etc.), execution time requirements (such as "execute immediately", "execute after 5 seconds delay"), and operation parameters.

[0151] The fault handling command is combined with the fault location information (such as "line identifier: L305", "tower number: T0142", "GPS coordinates: 30.5423°N, 114.3682°E") to form an isolation control message. A typical isolation control message includes a message header (containing a timestamp and priority identifier), a fault type code (such as "01" for metallic direct grounding, "02" for arcing metallic grounding), a location information field, an operation command code, and a checksum. For example, for a fault in... An arcing metallic grounding fault was detected at tower T0142 of line L305, generating the following isolation control message: "HD:20230615123045-P2;FT:02;LOC:L305-T0142;CMD:ISO-IMM;CRC:A5F3", where HD indicates that the message header contains a timestamp and priority 2, FT indicates that the fault type is arcing metallic grounding, LOC indicates location information, CMD indicates the command for immediate isolation, and CRC is the checksum.

[0152] The isolation control message is transmitted to the corresponding section isolation device through a communication network (such as a fiber optic network, wireless communication network, or power line carrier communication network). The isolation device can be a smart circuit breaker, load switch, or automatic reclosing device. After receiving the isolation control message, the device needs to verify the integrity and validity of the message, parse the fault handling instructions, and execute the corresponding fault isolation operation. For example, for an arcing metallic grounding fault, the device executes the operation sequence of "first disconnect the fault section, delay for 5 seconds and then try to reclose once, if the fault continues, then permanently isolate". After the operation is completed, the isolation device will generate operation feedback information and send it back to the system so that the system can update the fault handling status and records.

[0153] Through this precise fault type identification and intelligent fault isolation operation, the system can minimize the impact of faults while ensuring power supply reliability, thereby improving the self-healing capability and operational efficiency of the power distribution network.

[0154] The transmission line grounding fault location and analysis system of this invention includes:

[0155] The first unit is used to acquire zero-sequence component data and topological connection relationships of multiple monitoring points in the transmission line;

[0156] The second unit is used to extract the transient waveforms of zero-sequence current and zero-sequence voltage based on the zero-sequence component data, calculate the zero-sequence component of the ground fault and perform time-frequency joint analysis to obtain a fault feature vector that reflects the impedance characteristics of the grounding path.

[0157] The third unit is used to calculate the boundary node where the ground fault occurs and obtain the candidate fault section based on the directional distribution and amplitude attenuation law between each monitoring point in the topological connection relationship of the fault feature vector.

[0158] The fourth unit is used to construct a distribution function of the zero-sequence voltage propagating along the line in the candidate fault section based on the line distribution parameters in the topological connection relationship, solve the spatial location of the point in the distribution function that causes the zero-sequence voltage gradient to have an extreme value, and obtain the fault location information.

[0159] The fifth unit is used to identify the grounding fault type and grounding transition resistance state based on the fault feature vector corresponding to the fault location information, generate a fault handling command and transmit it to the section isolation device corresponding to the fault location information to perform fault isolation operation.

[0160] A third aspect of the present invention provides an electronic device, comprising:

[0161] processor;

[0162] Memory used to store processor-executable instructions;

[0163] The processor is configured to invoke instructions stored in the memory to execute the aforementioned method.

[0164] A fourth aspect of the present invention provides a computer-readable storage medium having stored thereon computer program instructions that, when executed by a processor, implement the aforementioned method.

[0165] This invention can be a method, apparatus, system, and / or computer program product. The computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for performing various aspects of the invention.

[0166] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for locating and analyzing grounding faults in transmission lines, characterized in that, include: Acquire zero-sequence component data and topological connectivity relationships from multiple monitoring points in a transmission line; Based on the zero-sequence component data, the transient waveforms of zero-sequence current and zero-sequence voltage are extracted, the zero-sequence component of the ground fault is calculated, and time-frequency joint analysis is performed to obtain a fault feature vector reflecting the impedance characteristics of the grounding path, including: The zero-sequence current and zero-sequence voltage in the zero-sequence component data are sampled synchronously. The transient waveforms of the zero-sequence current and zero-sequence voltage at each monitoring point before and after the fault triggering time are extracted, and the difference sequence between them and the steady-state waveform is calculated to obtain the zero-sequence component of the ground fault. A time-frequency joint analysis is performed on the zero-sequence component of the ground fault. The amplitude and phase of the zero-sequence current and zero-sequence voltage are extracted in the time domain, and the decay time constant is calculated. The amplitude distribution and phase distribution of its characteristic harmonic components are extracted in the frequency domain. The feature parameters extracted in the time domain and the feature parameters extracted in the frequency domain are correlated and mapped in time and frequency to obtain a time-frequency fusion feature set. Based on the transient waveforms of the zero-sequence current and the zero-sequence voltage during the fault duration, the instantaneous impedance value of the grounding path is calculated according to the time series. The distribution trajectory of the instantaneous impedance value on the complex plane is extracted to obtain impedance trajectory characteristic parameters that reflect the dynamic characteristics of the grounding transition resistance and the grounding arc. The time-frequency fusion feature set and the impedance trajectory feature parameters are concatenated to obtain the fault feature vector; Based on the fault feature vector and the topological connectivity, the directional distribution and amplitude attenuation patterns among the monitoring points are extracted, the boundary nodes where grounding faults occur are calculated, and candidate fault sections are obtained, including: From the fault feature vector, the zero-sequence current amplitude information and zero-sequence voltage phase information of each monitoring point are extracted. Based on the connection path between each monitoring point in the topological connection relationship, the flow direction of the zero-sequence current between adjacent monitoring points is calculated, and the phase relationship of the zero-sequence voltage at adjacent monitoring points is compared to determine the transmission direction of the zero-sequence power on the connection path, thereby obtaining the directional distribution between each monitoring point. Based on the zero-sequence current amplitude information of each monitoring point, the spatial gradient of the zero-sequence current amplitude is calculated along the connection path, the attenuation rate of the zero-sequence current amplitude along the connection path is extracted, and the attenuation rate is correlated and mapped with the line length of the connection path to obtain the amplitude attenuation law. Based on the directional distribution among the monitoring points and the amplitude attenuation law, a pair of monitoring points is identified where the zero-sequence current converges from multiple paths and the amplitude attenuation rate changes abruptly, and the monitoring point pair is determined as a boundary node. Based on the connection path, extract the line segments between the boundary nodes as candidate fault segments; Based on the line distribution parameters in the topological connection relationship, a distribution function of zero-sequence voltage propagating along the line in the candidate fault section is constructed, and the spatial location of the point in the distribution function that causes the zero-sequence voltage gradient to have an extreme value is solved to obtain the fault location information. Based on the fault feature vector corresponding to the fault location information, the grounding fault type and grounding transition resistance state are identified, a fault handling instruction is generated and transmitted to the section isolation device corresponding to the fault location information to perform fault isolation operation.

2. The method according to claim 1, characterized in that, Based on the zero-sequence current amplitude information at each monitoring point, the spatial gradient of the zero-sequence current amplitude is calculated along the connection path. The attenuation rate of the zero-sequence current amplitude along the connection path is extracted, and the attenuation rate is correlated and mapped with the line length of the connection path to obtain the amplitude attenuation law, including: The monitoring points are arranged along the connection path, the spatial coordinates of each monitoring point on the connection path are recorded, the spatial interval distance between adjacent monitoring points is calculated, and the amplitude difference of the zero-sequence current amplitude between adjacent monitoring points is calculated based on the zero-sequence current amplitude information of each monitoring point and divided by the corresponding spatial interval distance to obtain the spatial gradient sequence. Curve fitting is performed on the spatial gradient sequence to obtain the gradient function, and integral operation is performed on it along the spatial coordinates to obtain the cumulative attenuation distribution function, and the attenuation rate of the zero-sequence current amplitude is calculated. Extract the line length of the connection path and calculate the total attenuation over the entire length of the connection path. Establish the correlation mapping relationship between the attenuation rate, the line length and the total attenuation to form an amplitude attenuation law.

3. The method according to claim 1, characterized in that, Based on the line distribution parameters in the topological connection relationship, a distribution function of the zero-sequence voltage propagating along the line in the candidate fault section is constructed. The spatial location of the point in the distribution function that causes the zero-sequence voltage gradient to have an extreme value is solved to obtain the fault location information, including: From the topological connection relationship, the line distribution parameters corresponding to the candidate fault section are extracted. The line distribution parameters include the line resistance parameter per unit length, the line inductance parameter, and the line-to-ground capacitance parameter. Obtain the zero-sequence voltage and zero-sequence current measurements at the boundary nodes at both ends of the candidate fault section, and use them as boundary constraints for solving the distribution function; Based on the line distribution parameters, a propagation differential relationship of zero-sequence voltage along the spatial coordinates of the candidate fault section is established. The boundary constraint conditions are substituted into the propagation differential relationship for integration to obtain a distribution function describing the value of zero-sequence voltage at any spatial location within the candidate fault section. The distribution function is spatially differentiated to obtain a zero-sequence voltage gradient sequence and its first-order spatial derivative field is constructed. The positions of the extreme points with zero curvature in the first-order spatial derivative field are extracted, and the voltage jump amplitude of the distribution function at the corresponding positions is calculated. The extreme point positions where the voltage jump amplitude exceeds the jump threshold are used as fault location information.

4. The method according to claim 3, characterized in that, Based on the line distribution parameters, a propagation differential relationship of zero-sequence voltage along the spatial coordinates of the candidate fault section is established. The boundary constraints are substituted into the propagation differential relationship for integration to obtain a distribution function describing the value of zero-sequence voltage at any spatial location within the candidate fault section, including: Based on the line-to-ground capacitance parameter in the line distribution parameters, the candidate fault section is divided into multiple sub-segments, and the corresponding line distribution parameters are substituted into the physical law of zero-sequence voltage propagation to establish a differential correlation expression between the first and second derivatives of zero-sequence voltage with respect to spatial coordinates, thereby obtaining the propagation differential relationship of each sub-segment. Starting from the beginning position of the first sub-segment, the boundary constraints are substituted into the propagation differential relation of the first sub-segment, and integration is performed along the positive direction of spatial coordinates to obtain the forward propagation function of each sub-segment. Starting from the end position of the last sub-segment, the boundary constraints are substituted into the propagation differential relation of the last sub-segment, and integration is performed along the negative direction of spatial coordinates to obtain the backward propagation function of each sub-segment. The integral difference between the forward propagation function at the beginning position of each sub-segment and the backward propagation function is calculated. Select the sub-segment with the smallest integral difference as the target sub-segment, adjust the boundary constraints according to its corresponding integral difference, and repeat the forward integration operation and the backward integration operation until the integral difference of the target sub-segment converges to the convergence threshold. After the numerical difference converges, the forward propagation function and the backward propagation function are smoothly connected at the beginning of the target sub-segment to obtain the distribution function of the entire candidate fault segment.

5. The method according to claim 1, characterized in that, Based on the fault feature vector corresponding to the fault location information, the ground fault type and ground transition resistance state are identified, a fault handling command is generated and transmitted to the section isolation device corresponding to the fault location information, and a fault isolation operation is performed, including: Based on the fault feature vector corresponding to the fault location information, calculate the phase difference between the zero-sequence current and the zero-sequence voltage, and preliminarily determine the ground fault type based on the phase difference. From the impedance trajectory characteristic parameters of the fault feature vector, the real and imaginary components of the zero-sequence impedance are extracted. Based on the ratio of the real and imaginary components, the resistance estimation result of the transition resistance in the grounding loop is calculated. The resistance estimation result is compared with the preset metallic grounding resistance benchmark to identify the grounding transition resistance status. Based on the fault feature vector, the amplitude of the fundamental component and the amplitude of the higher harmonic components are extracted, and their amplitude ratio is calculated. According to the amplitude ratio, it is determined whether the ground fault is accompanied by an arc discharge phenomenon. If so, the ground fault type is corrected to arc grounding, and the corrected ground fault type is obtained. Based on the corrected ground fault type and the ground transition resistance state, the execution priority of the fault isolation operation is determined, and a fault handling instruction is generated. The fault handling instruction is combined with the fault location information to form an isolation control message. The isolation control message is transmitted to the section isolation device corresponding to the fault location information through the communication network. After receiving the isolation control message, the section isolation device parses the fault handling instruction and performs the fault isolation operation.

6. A system for locating and analyzing grounding faults in transmission lines, used to implement the method as described in any one of claims 1-5, characterized in that, include: The first unit is used to acquire zero-sequence component data and topological connection relationships of multiple monitoring points in the transmission line; The second unit is used to extract the transient waveforms of zero-sequence current and zero-sequence voltage based on the zero-sequence component data, calculate the zero-sequence component of the ground fault and perform time-frequency joint analysis to obtain a fault feature vector that reflects the impedance characteristics of the grounding path. The third unit is used to calculate the boundary node where the ground fault occurs and obtain the candidate fault section based on the directional distribution and amplitude attenuation law between each monitoring point in the topological connection relationship of the fault feature vector. The fourth unit is used to construct a distribution function of the zero-sequence voltage propagating along the line in the candidate fault section based on the line distribution parameters in the topological connection relationship, solve the spatial location of the point in the distribution function that causes the zero-sequence voltage gradient to have an extreme value, and obtain the fault location information. The fifth unit is used to identify the grounding fault type and grounding transition resistance state based on the fault feature vector corresponding to the fault location information, generate a fault handling command and transmit it to the section isolation device corresponding to the fault location information to perform fault isolation operation.

7. An electronic device, characterized in that, include: processor; Memory used to store processor-executable instructions; The processor is configured to invoke instructions stored in the memory to execute the method according to any one of claims 1 to 5.

8. A computer-readable storage medium having computer program instructions stored thereon, characterized in that, When the computer program instructions are executed by the processor, they implement the method described in any one of claims 1 to 5.

Images