Off-line single-phase earth fault location method for overhead lines based on ac signal injection

Abstract

An off-line overhead line single-phase grounding fault positioning method based on AC signal injection, after single-phase grounding fault occurs, the fault line is isolated and an AC voltage signal is simultaneously injected into the three-phase line by using a signal generating device; the fault branch is determined according to the zero sequence admittance angle difference of different branches at the branch point, and then the fault direction is determined by using the zero sequence admittance angle difference of different detection points of the fault branch; the present application is a modification of the fault off-line positioning method based on the signal amplitude difference on both sides of the fault point, and comprehensively utilizes the zero sequence admittance angle information of the fault branch and the non-fault branch, the upstream and downstream of the fault point as a new single-phase grounding fault positioning idea, avoiding the problems of the line capacitance shunt effect of the signal amplitude difference method on both sides of the fault point and the low measurement accuracy of the non-contact signal measurement method. Compared with the existing signal amplitude difference positioning method, it is not affected by the system structure and operation mode, can tolerate higher transition resistance, has wider application range and higher reliability.

Description

Technical Field

[0001] This invention belongs to the field of power grid fault detection and location technology, specifically relating to an offline overhead line single-phase grounding fault location method based on AC signal injection, applicable to the case of permanent single-phase grounding faults in overhead distribution lines. Background Technology

[0002] The power distribution network is a vital public infrastructure for national economic and social development, playing a crucial supporting and safeguarding role in promoting economic and social progress. Distribution lines have complex structures and are subject to diverse natural environments, making them prone to grounding faults, with single-phase grounding faults being the most frequent. When a single-phase grounding fault occurs, the resulting overvoltage on intact lines can easily cause weak points in the insulation to break down, potentially triggering short circuits, expanding the fault area, and even causing power outages. In recent years, with economic development and social progress, users have increasingly higher requirements for power supply quality and reliability, leading to greater economic losses and negative social impacts from power outages. Furthermore, single-phase grounding faults can also cause accidents that threaten personal safety, such as forest fires caused by electric arcing, and electric shocks from tree debris.

[0003] Determining the precise location of a fault is crucial for quickly, accurately, and effectively locating and eliminating the fault and restoring power supply. While fault location techniques are relatively mature, with methods such as zero-sequence current comparison, harmonic component analysis, medium resistance analysis, and matrix analysis widely used in urban power distribution networks, precise fault location still relies on manual line inspection. This requires inspectors to visually search for the fault along the faulty line. This method not only consumes significant manpower and resources but also makes it difficult to detect hidden faults such as insulator breakdown and internal surge arrester faults by visual inspection. Furthermore, if the fault occurs in severe weather or in areas with complex terrain, it undoubtedly poses significant challenges to manual line inspection, thus prolonging the fault location time. Therefore, a practical and effective method for locating single-phase grounding faults is urgently needed to solve this problem. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide an offline method for locating single-phase grounding faults in overhead lines based on AC signal injection, thereby solving the problem of permanent single-phase grounding faults in overhead power distribution lines.

[0005] The present invention adopts the following technical solution.

[0006] An offline single-phase grounding fault location method for overhead lines based on AC signal injection, comprising:

[0007] Step 1: After a single-phase ground fault occurs on the overhead line of the distribution network, the faulty line is isolated and an AC voltage signal with constant frequency f and constant phase θ is simultaneously injected into the three-phase line of the overhead line using a signal generating device.

[0008] Step 2: The controller uses a satellite communication module to use the satellite as a timing source and a non-contact signal measurement device to collect data at the k-th detection point Q on the j-th branch of the overhead line. jk The zero-sequence current signal at the detection point is used to calculate the zero-sequence admittance angle at that point. Where j = 1, 2…m, k = 1, 2…n, m is the number of branches, and n is the number of detection points on the j-th branch;

[0009] Step 3, let k=1, and compare the beginning Q of different branches at each branch point in turn. j1 zero-sequence admittance angle With the set threshold value If the condition is met, it is determined that a permanent single-phase ground fault has occurred in the branch where the detection point is located, and step 4 is executed; otherwise, let j = j + 1 and execute step 3.

[0010] Step 4: Accurately locate the fault point after determining the faulty branch;

[0011] Step 5: If j≤m, then execute step 3; otherwise, it can be determined that no permanent single-phase grounding fault has occurred from the beginning of the line to the end of the line.

[0012] Preferably, step 2 specifically includes:

[0013] Step 2.1: The controller selects a certain moment after the zero-sequence current signal is injected as the zero moment, denoted as t0. The phase of the zero-sequence current signal corresponding to the zero moment t0 is denoted as θ. t0 ;

[0014] Step 2.2: Use a satellite as a timing source, which provides a synchronization signal and a clock for the controller, which is a signal measuring device;

[0015] Step 2.3: The signal measurement device samples the zero-sequence current signal at time t0, and measures multiple zero-sequence current signals corresponding to θ. t0-u Or θ t0-d The moment is denoted as t. in Where n = 1, 2, 3..., the detection point Q is obtained. jk The time difference t between zero-sequence voltage and zero-sequence current jk for:

[0016] t jk =t in -n·360°±Δt

[0017] Where Δt is the synchronization error with the clock of the signal measuring device;

[0018] Step 2.4: Calculate the detection point Q jk zero-sequence admittance angle Its expression is:

[0019]

[0020] In the formula: f is the frequency of the injected signal.

[0021] Preferably, different θ values ​​are distinguished between the rising interval from the voltage trough to the peak and the falling interval from the voltage peak to the trough. t0 And denoted as θ respectively t0-u and θ t0-d .

[0022] Preferably, the criterion in step 3 is...

[0023] Preferably, step 4 specifically includes:

[0024] Step 4.1: Let k = k + 1, and compare the different detection points Q of the faulty branch in turn. jk zero-sequence admittance angle With the set threshold value If the detection point Q jk zero-sequence admittance angle The criterion is met, that is If the fault direction is positive, meaning the detection point is upstream of the fault point, then step 3 is executed; otherwise, if the fault direction is negative, meaning the detection point is downstream of the fault point, then the fault point is considered to be located at detection point Q. jk-1 and Q jk In between, proceed to step 4.2;

[0025] Step 4.2: Compare detection point Q jk-1 and Q jk Distance x between Qjk-1Qjk With the set threshold value x set ,like Let k = k + 1, and continue comparing the detection points Q. jk zero-sequence admittance angle With the set threshold value like If the fault direction is determined to be positive, meaning the detection point is upstream of the fault point, then the fault point is considered to be located at detection point Q. jk-1 and Q jk If the fault direction is negative, then proceed to step 4.2; otherwise, the fault point is considered to be downstream of the fault point. jk-2 and Q jk In between, execute step 4.3, if At detection point Q jk-1 and Q jk Follow the line until the zero-sequence admittance angle is found. Depend on Change to The point, i.e., the precise location of the fault point;

[0026] Step 4.3: Compare detection points Q jk-2 and Q jk Distance between With the set threshold value x set ,like Let k = k + 1, and continue comparing the detection points Q. jk zero-sequence admittance angle With the set threshold value like If the fault direction is determined to be positive, meaning the detection point is upstream of the fault point, then the fault point is considered to be located at detection point Q. jk-1 and Q jk If the fault direction is negative, then proceed to step 4.2; otherwise, the fault point is considered to be downstream of the fault point. jk-2 and Q jk In between, execute step 4.3, if At detection point Q jk-2 and Q jk Follow the line until the zero-sequence admittance angle is found. Depend on Change to The point, that is, the precise location of the fault.

[0027] Preferably, the criterion in step 4.1 is...

[0028] An offline overhead line single-phase grounding fault location device based on AC signal injection, comprising:

[0029] The controller, satellite communication module, and non-contact signal measurement device are all connected to the controller.

[0030] The modules running on the controller include:

[0031] The data acquisition module is used to acquire data from the k-th detection point Q on the j-th branch of the overhead line via a satellite communication module, using a satellite as a timing source, and via a non-contact signal measurement device. jk The zero-sequence current signal at the detection point is used to calculate the zero-sequence admittance angle at that point. Where j = 1, 2…m, k = 1, 2…n, m is the number of branches, and n is the number of detection points on the j-th branch;

[0032] The comparison module, which sets k=1, sequentially compares the beginnings Q of different branches at each branch point. j1 zero-sequence admittance angle With the set threshold value If the condition is met, then it is determined that a permanent single-phase ground fault has occurred in the branch where the detection point is located; otherwise, let j = j + 1.

[0033] The positioning module is used to accurately locate the fault point after the faulty branch has been identified.

[0034] The execution module is used to execute the comparison module if j≤m, otherwise it can be determined that there is no permanent single-phase grounding fault from the beginning to the end of the line.

[0035] Preferably, the acquisition module is further configured to select a certain moment after the zero-sequence current signal is injected as time zero, denoted as t0, and the phase of the zero-sequence current signal corresponding to time zero t0 is denoted as θ. t0 Using a satellite as a timing source, this source provides a synchronization signal and a clock for the controller, which functions as a signal measurement device; zero-sequence current signals are sampled at time t0, and multiple zero-sequence current signals corresponding to θ are measured. t0-u Or θ t0-d The moment is denoted as t. in Where n = 1, 2, 3..., the detection point Q is obtained. jk The time difference t between zero-sequence voltage and zero-sequence current jk for:

[0036] t jk =t in -n·360°±Δt

[0037] Where Δt is the synchronization error with the clock of the signal measuring device; calculate the detection point Q. jk zero-sequence admittance angle Its expression is:

[0038]

[0039] In the formula: f is the frequency of the injected signal.

[0040] Preferably, the criterion in the comparison module is...

[0041] Preferably, the positioning module is further configured to set k = k + 1 and sequentially compare different detection points Q of the faulty branch. jk zero-sequence admittance angle With the set threshold value If the detection point Q jk zero-sequence admittance angle The criterion is met, that is If the fault direction is positive, the detection point is upstream of the fault point; otherwise, if the fault direction is negative, the detection point is downstream of the fault point, and the fault point is considered to be located at detection point Q. jk-1 and Q jk Between; compare detection point Q jk-1 and Q jk Distance between With the set threshold value x set ,like Let k = k + 1, and continue comparing the detection points Q. jk zero-sequence admittance angle With the set threshold value like If the fault direction is determined to be positive, meaning the detection point is upstream of the fault point, then the fault point is considered to be located at detection point Q. jk-1 and Q jk If the fault direction is negative, the detection point is located downstream of the fault point, and in this case, the fault point is considered to be located at detection point Q. jk-2 and Q jk Between, if At detection point Q jk-1 and Q jk Follow the line until the zero-sequence admittance angle is found. Depend on Change to The point, i.e., the precise location of the fault; compare the detection point Q. jk-2 and Q jk Distance between With the set threshold value x set ,like Let k = k + 1, and continue comparing the detection points Q. jk zero-sequence admittance angle With the set threshold value like If the fault direction is determined to be positive, meaning the detection point is upstream of the fault point, then the fault point is considered to be located at detection point Q. jk-1 and Q jk If the fault direction is negative, the detection point is located downstream of the fault point, and in this case, the fault point is considered to be located at detection point Q. jk-2 and Q jk Between, if At detection point Q jk-2 and Q jk Follow the line until the zero-sequence admittance angle is found. Depend on Change to The point, that is, the precise location of the fault.

[0042] Preferably, the criterion in the positioning module is...

[0043] A terminal, comprising a processor and a storage medium;

[0044] The storage medium is used to store instructions;

[0045] The processor is configured to operate according to the instructions to execute the steps of the offline overhead line single-phase grounding fault location method based on AC signal injection.

[0046] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the offline overhead line single-phase grounding fault location method based on AC signal injection.

[0047] The beneficial effects of this invention are that, compared with the prior art, it is an improvement on the offline fault location method based on the signal amplitude difference between the two sides of the fault point for single-phase grounding faults in overhead lines. It comprehensively utilizes the zero-sequence admittance angle information of the faulty and non-faulty branches, as well as the upstream and downstream of the fault point, as a new approach to single-phase grounding fault location. This avoids the problems of line capacitance shunting effect and low measurement accuracy of non-contact signal measurement methods, which are inherent to the signal amplitude difference method between the two sides of the fault point. Compared with existing signal amplitude difference location methods, this invention is not affected by system structure and operating mode, can withstand higher transition resistance, has a wider range of applications, and higher reliability. Attached Figure Description

[0048] Figure 1 This is a flowchart of the offline single-phase grounding fault location method for overhead lines based on AC signal injection, according to the present invention.

[0049] Figure 2 This is a schematic diagram of the module structure of the offline overhead line single-phase grounding fault location device based on AC signal injection of the present invention.

[0050] Figure 3 This is a schematic diagram of a multi-branch line;

[0051] Figure 4 The waveform diagram for the zero-sequence admittance angle measurement principle is shown below.

[0052] Figure 5 This is a schematic diagram of the simulation model structure;

[0053] Figure 6 The waveform of the injected AC voltage;

[0054] Figure 7 The diagram shows the zero-sequence current waveforms at the outlets of the faulty and non-faulty branches.

[0055] Figure 8 The diagram shows the zero-sequence current waveforms at the upstream and downstream detection points of the fault. Detailed Implementation

[0056] This invention isolates the faulty line after a single-phase ground fault occurs and simultaneously injects AC voltage signals with constant frequency and phase into all three phases using a signal generating device. Zero-sequence current signals are collected along the line using satellite and non-contact signal measurement devices to calculate the zero-sequence admittance angle at the detection point. The faulty branch is determined based on the difference in zero-sequence admittance angles between different branches at the branch point. The fault direction is then determined using the difference in zero-sequence admittance angles at different detection points along the faulty branch. The fault direction allows for gradual narrowing down the fault location until the precise location of the fault point is determined. This invention is an improvement on the offline fault location method based on the signal amplitude difference between the two sides of the fault point. It comprehensively utilizes the zero-sequence admittance angle information of the faulty and non-faulty branches, as well as the upstream and downstream of the fault point, as a new approach to single-phase ground fault location. This avoids the problems of line capacitance shunting in the signal amplitude difference method and the low measurement accuracy of non-contact signal measurement methods. Compared to existing signal amplitude difference location methods, this invention is unaffected by system structure and operating mode, can withstand higher transition resistance, has a wider range of applications, and higher reliability.

[0057] The present application will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and should not be construed as limiting the scope of protection of the present application.

[0058] like Figure 1 As shown, the offline single-phase grounding fault location method for overhead lines based on AC signal injection according to the present invention includes:

[0059] After a single-phase ground fault occurs on an overhead line in a power distribution network, the faulty line is isolated and a constant frequency and phase AC voltage signal is simultaneously injected into the three-phase line using a signal generating device. Zero-sequence current signals are collected along the line using satellite and non-contact signal measuring devices to calculate the zero-sequence admittance angle at the detection point. The faulty branch is determined based on the difference in zero-sequence admittance angles of different branches at the branch point. The fault direction is then determined by the difference in zero-sequence admittance angles of different detection points on the faulty branch. The fault direction can be used to gradually narrow down the fault section until the precise location of the fault point is determined.

[0060] The specific judgment steps are as follows:

[0061] Step 1: After a single-phase ground fault occurs on the overhead line of the distribution network, the faulty line is isolated and an AC voltage signal with constant frequency f and constant phase θ is simultaneously injected into the three-phase line of the overhead line using a signal generating device.

[0062] Step 2: The controller uses a satellite communication module to use the satellite as a timing source and a non-contact signal measurement device to collect data at the k-th detection point Q on the j-th branch of the overhead line. jk The zero-sequence current signal at the location, such as Figure 3 As shown, the zero-sequence admittance angle at the detection point is calculated. Where j = 1, 2…m, k = 1, 2…n, m is the number of branches, and n is the number of detection points on the j-th branch;

[0063] In a preferred but non-limiting embodiment of the present invention, step 2 specifically includes:

[0064] Step 2.1: The controller selects a certain moment after the zero-sequence current signal is injected as the zero moment, denoted as t0. The phase of the zero-sequence current signal corresponding to the zero moment t0 is denoted as θ. t0 ;

[0065] In a preferred but non-limiting embodiment of the present invention, (considering that the same phase within a single cycle may correspond to two moments, it is necessary to distinguish between different θ values ​​located in the rising interval from voltage trough to peak and the falling interval from voltage peak to trough) t0 And denoted as θ respectively t0-u and θ t0-d ).

[0066] Step 2.2: Use a satellite as a timing source, which provides a synchronization signal and a clock for the controller, which is a signal measuring device;

[0067] Step 2.3: The signal measurement device samples the zero-sequence current signal at time t0, and measures multiple zero-sequence current signals corresponding to θ. t0-u Or θ t0-d The moment is denoted as t. in Where n = 1, 2, 3..., the detection point Q is obtained. jk The time difference t between zero-sequence voltage and zero-sequence current jk for:

[0068] t jk =t in -n·360°±Δt

[0069] Where Δt is the synchronization error with the clock of the signal measuring device;

[0070] Step 2.4: Calculate the detection point Q jk zero-sequence admittance angle Its expression is:

[0071]

[0072] In the formula: f is the frequency of the injected signal.

[0073] Step 3, let k=1, and compare the beginning Q of different branches at each branch point in turn. j1 zero-sequence admittance angle With the set threshold value If the condition is met, then it is determined that a permanent single-phase ground fault has occurred in the branch where the detection point is located, and step 4 is executed; otherwise, let j = j + 1, and step 3 is executed. Figure 3 China Q 21 The criterion is met, therefore step 4 is executed;

[0074] In a preferred but non-limiting embodiment of the present invention, the criterion in step 3 is...

[0075] Step 4: Accurately locate the fault point after determining the faulty branch;

[0076] In a preferred but non-limiting embodiment of the present invention, step 4 specifically includes:

[0077] Step 4.1: Let k = k + 1, and compare the different detection points Q of the faulty branch in turn. jk zero-sequence admittance angle With the set threshold value If the detection point Q jk zero-sequence admittance angle The criterion is met, that is If the fault direction is positive, meaning the detection point is upstream of the fault point, then step 3 is executed; otherwise, if the fault direction is negative, meaning the detection point is downstream of the fault point, then the fault point is considered to be located at detection point Q. jk-1 and Q jk In between, proceed to step 4.2;

[0078] In a preferred but non-limiting embodiment of the present invention, the criterion in step 4.1 is...

[0079] Step 4.2: Compare detection point Q jk-1 and Q jk Distance between With the set threshold value x set ,like Let k = k + 1, and continue comparing the detection points Q. jk zero-sequence admittance angle With the set threshold value like If the fault direction is determined to be positive, meaning the detection point is upstream of the fault point, then the fault point is considered to be located at detection point Q. jk-1 and Q jk If the fault direction is negative, then proceed to step 4.2; otherwise, the fault point is considered to be downstream of the fault point. jk-2 and Q jk In between, execute step 4.3, if At detection point Q jk-1 and Q jkFollow the line until the zero-sequence admittance angle is found. Depend on Change to The point, i.e., the precise location of the fault point;

[0080] Step 4.3: Compare detection points Q jk-2 and Q jk Distance between With the set threshold value x set ,like Let k = k + 1, and continue comparing the detection points Q. jk zero-sequence admittance angle With the set threshold value like If the fault direction is determined to be positive, meaning the detection point is upstream of the fault point, then the fault point is considered to be located at detection point Q. jk-1 and Q jk If the fault direction is negative, then proceed to step 4.2; otherwise, the fault point is considered to be downstream of the fault point. jk-2 and Q jk In between, execute step 4.3, if At detection point Q jk-2 and Q jk Follow the line until the zero-sequence admittance angle is found. Depend on Change to The point, that is, the precise location of the fault.

[0081] In particular, such as Figure 3 As shown, the fault location is determined using the bisection method, therefore Q j1 and Q j2 Q is set at the beginning and end of the branch road respectively. jk (k = 3, 4, 5…n) is set at the midpoint between two detection points with opposite fault directions, such as… Figure 3 As shown.

[0082] Step 5: If j≤m, then execute step 3; otherwise, it can be determined that no permanent single-phase grounding fault has occurred from the beginning of the line to the end of the line.

[0083] The method of the present invention will be illustrated below through specific embodiments:

[0084] like Figure 4 As shown, the CD section and CH branch of the overhead line of the distribution network are selected for simulation to simulate a single-phase ground fault scenario with branch lines. Figure 5As shown. Both lines are overhead lines. The lengths of sections CD are set to 5km, 15km, 25km, and 40km, and the length of branch CH is 20km. The relevant positive-sequence parameters of the overhead lines are: R1 = 0.1210Ω / km, L1 = 1.019mH / km, C1 = 11.480pF / km; the zero-sequence parameters are: R0 = 0.3460Ω / km, L0 = 4.787mH / km, C0 = 4.035pF / km. A voltage of 500V is injected at point C at the beginning of the line, with a frequency of 120Hz. Figure 6 As shown. Taking a phase A ground fault occurring 10km from point C on line CD as an example, the grounding resistances are set to 10Ω, 100Ω, 1kΩ, and 5kΩ respectively; two terminal detection points Q are set. 31 and Q 41 These points are located on the faulty line CD and the non-faulty branch CH, respectively, both 0.5m from point C. Here, the admittance angle threshold for the faulty branch criterion is taken as 80°. The faulty branch outlet Q... 11 Q at the exit of the non-faulty branch 21 The zero-sequence current exhibits a significant phase difference, such as Figure 7 As shown in Table 1, there are significant differences in the zero-sequence admittance angle at the outlet of the faulty branch and the non-faulty branch under different transition resistances and fault line lengths. Therefore, the method provided in this embodiment can accurately determine the single-phase ground fault branch.

[0085] Table 1

[0086]

[0087]

[0088] Similarly, select Figure 4 The simulation of section CD shown illustrates a scenario where a single-phase ground fault occurs on a branchless line. The line is an overhead line, and section CD is 20km long. Six terminal detection points are set up, including Q... 11 Q 14 Q 15 Located upstream of the fault point, at distances of 0km, 5km, and 7.5km from point C respectively, Q 12 and Q 13 Located downstream of the fault point, 20km and 10km from point C respectively, the fault point is located at detection point Q. 15 and Q 13 Between. Here, the admittance angle threshold value for the fault direction criterion is also 80°. Other conditions are as above. Figure 8 As shown in Table 2, there is a significant difference in phase between the zero-sequence currents upstream and downstream of the fault point. Furthermore, under different transition resistances, there is a significant difference in the zero-sequence admittance angles upstream and downstream of the fault. Therefore, the method provided in this embodiment can locate the fault point.

[0089] Table 2

[0090]

[0091]

[0092] Therefore, this embodiment uses zero-sequence admittance angle information to construct the positioning criterion. Compared with the method that simply uses signal amplitude, this method avoids the problems of line capacitance shunting effect and low measurement accuracy of non-contact signal measurement methods caused by the signal amplitude difference method on both sides of the fault point. It is not affected by system structure and operation mode, can withstand higher transition resistance, has a wider range of applications, and higher reliability.

[0093] like Figure 2 As shown, the present invention provides an offline overhead line single-phase grounding fault location device based on AC signal injection, comprising:

[0094] The system includes a controller, a satellite communication module, and a non-contact signal measurement device, all of which are connected to the controller. The non-contact signal measurement device is a zero-sequence current transformer. The controller can be a microcontroller or a PLC.

[0095] The modules running on the controller include:

[0096] The data acquisition module is used to acquire data from the k-th detection point Q on the j-th branch of the overhead line via a satellite communication module, using a satellite as a timing source, and via a non-contact signal measurement device. jk The zero-sequence current signal at the detection point is used to calculate the zero-sequence admittance angle at that point. Where j = 1, 2…m, k = 1, 2…n, m is the number of branches, and n is the number of detection points on the j-th branch;

[0097] The comparison module, which sets k=1, sequentially compares the beginnings Q of different branches at each branch point. j1 zero-sequence admittance angle With the set threshold value If the condition is met, then it is determined that a permanent single-phase ground fault has occurred in the branch where the detection point is located; otherwise, let j = j + 1.

[0098] The positioning module is used to accurately locate the fault point after the faulty branch has been identified.

[0099] The execution module is used to execute the comparison module if j≤m, otherwise it can be determined that there is no permanent single-phase grounding fault from the beginning to the end of the line.

[0100] In a preferred but non-limiting embodiment of the present invention, the acquisition module is further configured to select a certain moment after the zero-sequence current signal is injected as time zero, denoted as t0, and the phase of the zero-sequence current signal corresponding to time zero t0 is denoted as θ. t0 Using a satellite as a timing source, this source provides a synchronization signal and a clock for the controller, which functions as a signal measurement device; zero-sequence current signals are sampled at time t0, and multiple zero-sequence current signals corresponding to θ are measured. t0-u Or θ t0-d The moment is denoted as t. in Where n = 1, 2, 3..., the detection point Q is obtained. jk The time difference t between zero-sequence voltage and zero-sequence current jk for:

[0101] t jk =t in -n·360°±Δt

[0102] Where Δt is the synchronization error with the clock of the signal measuring device; calculate the detection point Q. jk zero-sequence admittance angle Its expression is:

[0103]

[0104] In the formula: f is the frequency of the injected signal.

[0105] In a preferred but non-limiting embodiment of the present invention, the criterion in the comparison module is...

[0106] In a preferred but non-limiting embodiment of the present invention, the positioning module is further configured to set k = k + 1 and sequentially compare different detection points Q of the faulty branch. jk zero-sequence admittance angle With the set threshold value If the detection point Q jk zero-sequence admittance angle The criterion is met, that is If the fault direction is positive, the detection point is upstream of the fault point; otherwise, if the fault direction is negative, the detection point is downstream of the fault point, and the fault point is considered to be located at detection point Q. jk-1 and Q jk Between; compare detection point Q jk-1 and Q jk Distance between With the set threshold value x set ,like Let k = k + 1, and continue comparing the detection points Q. jk zero-sequence admittance angle With the set threshold value like If the fault direction is determined to be positive, meaning the detection point is upstream of the fault point, then the fault point is considered to be located at detection point Q. jk-1 and Q jk If the fault direction is negative, the detection point is located downstream of the fault point, and in this case, the fault point is considered to be located at detection point Q. jk-2 and Q jk Between, if At detection point Q jk-1 and Q jk Follow the line until the zero-sequence admittance angle is found. Depend on Change to The point, i.e., the precise location of the fault; compare the detection point Q. jk-2 and Q jk Distance between With the set threshold value x set ,like Let k = k + 1, and continue comparing the detection points Q. jk zero-sequence admittance angle With the set threshold value like If the fault direction is determined to be positive, meaning the detection point is upstream of the fault point, then the fault point is considered to be located at detection point Q. jk-1 and Q jk If the fault direction is negative, the detection point is located downstream of the fault point, and in this case, the fault point is considered to be located at detection point Q. jk-2 and Q jk Between, if At detection point Q jk-2 and Q jk Follow the line until the zero-sequence admittance angle is found. Depend on Change to The point, that is, the precise location of the fault.

[0107] In a preferred but non-limiting embodiment of the present invention, the criterion in the positioning module is...

[0108] The terminal described in this invention includes a processor and a storage medium;

[0109] The storage medium is used to store instructions;

[0110] The processor is configured to operate according to the instructions to execute the steps of the offline overhead line single-phase grounding fault location method based on AC signal injection.

[0111] The present invention discloses a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the offline overhead line single-phase grounding fault location method based on AC signal injection.

[0112] The beneficial effects of this invention are that, compared with the prior art, it is an improvement on the offline fault location method based on the signal amplitude difference between the two sides of the fault point for single-phase grounding faults in overhead lines. It comprehensively utilizes the zero-sequence admittance angle information of the faulty and non-faulty branches, as well as the upstream and downstream of the fault point, as a new approach to single-phase grounding fault location. This avoids the problems of line capacitance shunting effect and low measurement accuracy of non-contact signal measurement methods, which are inherent to the signal amplitude difference method between the two sides of the fault point. Compared with existing signal amplitude difference location methods, this invention is not affected by system structure and operating mode, can withstand higher transition resistance, has a wider range of applications, and higher reliability.

[0113] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, apparatus, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0114] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (devices), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0115] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0116] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0117] Specific embodiments have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

[0118] In the description of this specification, the references to terms such as "an embodiment," "a specific embodiment," "some embodiments," "for example," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0119] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An offline method for locating single-phase grounding faults in overhead lines based on AC signal injection, characterized in that, include: Step 1: After a single-phase ground fault occurs on the overhead line of the distribution network, the faulty line is isolated and an AC voltage signal with constant frequency f and constant phase θ is simultaneously injected into the three-phase line of the overhead line using a signal generating device. Step 2: The controller uses a satellite communication module to use the satellite as a timing source and a non-contact signal measurement device to collect data at the k-th detection point Q on the j-th branch of the overhead line. jk The zero-sequence current signal at the detection point is used to calculate the zero-sequence admittance angle at that point. Where j = 1, 2…m, k = 1, 2…n, m is the number of branches, and n is the number of detection points on the j-th branch; Step 3, let k=1, and compare the beginning Q of different branches at each branch point in turn. j1 zero-sequence admittance angle With the set threshold value If the condition is met, it is determined that a permanent single-phase ground fault has occurred in the branch where the detection point is located, and step 4 is executed; otherwise, let j = j + 1 and execute step 3. Step 4: Accurately locate the fault point after determining the faulty branch; Step 5: If j≤m, then execute step 3; otherwise, it can be determined that no permanent single-phase grounding fault has occurred from the beginning of the line to the end of the line. Step 2 specifically includes: Step 2.1: The controller selects a certain moment after the zero-sequence current signal is injected as the zero moment, denoted as t0. The phase of the zero-sequence current signal corresponding to the zero moment t0 is denoted as θ. t0 ; Step 2.2: Use a satellite as a timing source, which provides a synchronization signal and a clock for the controller, which is a signal measurement device; Step 2.3: Distinguish between different θ values ​​located within the rising interval from voltage trough to peak and the falling interval from voltage peak to trough. t0 And denoted as θ respectively t0-u and θ t0-d， The signal measurement device samples the zero-sequence current signal at time t0 and measures multiple zero-sequence current signals corresponding to θ. t0-u Or θ t0-d The moment is denoted as t. in Where n = 1, 2, 3..., the detection point Q is obtained. jk The time difference t between zero-sequence voltage and zero-sequence current jk for: t jk =t in -n·(1 / f)±Δt Where Δt is the synchronization error with the clock of the signal measuring device; Step 2.4: Calculate the detection point Q jk zero-sequence admittance angle Its expression is: In the formula: f is the frequency of the injected signal.

2. The offline overhead line single-phase grounding fault location method based on AC signal injection according to claim 1, characterized in that, The criterion in step 3 is...

3. The offline single-phase grounding fault location method for overhead lines based on AC signal injection according to claim 1, characterized in that, Step 4 specifically includes: Step 4.1: Let k = k + 1, and compare the different detection points Q of the faulty branch in turn. jk zero-sequence admittance angle With the set threshold value If the detection point Q jk zero-sequence admittance angle The criterion is met, that is If the fault direction is positive, meaning the detection point is upstream of the fault point, then step 3 is executed; otherwise, if the fault direction is negative, meaning the detection point is downstream of the fault point, then the fault point is considered to be located at detection point Q. jk-1 and Q jk In between, proceed to step 4.2; Step 4.2: Compare detection point Q jk-1 and Q jk Distance between With the set threshold value x set ,like Let k = k + 1, and continue comparing the detection points Q. jk zero-sequence admittance angle With the set threshold value like If the fault direction is determined to be positive, meaning the detection point is upstream of the fault point, then the fault point is considered to be located at detection point Q. jk-1 and Q jk Between, re-execute the comparison test point Q. jk-1 and Q jk Distance between With the set threshold value x set Otherwise, the fault direction is negative, meaning the detection point is downstream of the fault point, in which case the fault point is considered to be located at detection point Q. jk-2 and Q jk In between, execute step 4.3, if At detection point Q jk-1 and Q jk Follow the line until the zero-sequence admittance angle is found. Depend on Change to The point, i.e., the precise location of the fault point; Step 4.3: Compare detection points Q jk-2 and Q jk Distance between With the set threshold value x set ,like Let k = k + 1, and continue comparing the detection points Q. jk zero-sequence admittance angle With the set threshold value like If the fault direction is determined to be positive, meaning the detection point is upstream of the fault point, then the fault point is considered to be located at detection point Q. jk-1 and Q jk If the fault direction is negative, then proceed to step 4.2; otherwise, the fault point is considered to be downstream of the fault point. jk-2 and Q jk Between, re-execute the comparison test point Q. jk-2 and Q jk Distance between With the set threshold value x set ,like At detection point Q jk-2 and Q jk Follow the line until the zero-sequence admittance angle is found. Depend on Change to The point, that is, the precise location of the fault.

4. An offline overhead line single-phase grounding fault location device based on AC signal injection, characterized in that, include: The controller, satellite communication module, and non-contact signal measurement device are all connected to the controller. The modules running on the controller include: The data acquisition module is used to acquire data from the k-th detection point Q on the j-th branch of the overhead line via a satellite communication module, using a satellite as a timing source, and via a non-contact signal measurement device. jk The zero-sequence current signal at the detection point is used to calculate the zero-sequence admittance angle at that point. Where j = 1, 2…m, k = 1, 2…n, m is the number of branches, and n is the number of detection points on the j-th branch; The comparison module, which sets k=1, sequentially compares the beginnings Q of different branches at each branch point. j1 zero-sequence admittance angle With the set threshold value If the condition is met, it is determined that a permanent single-phase ground fault has occurred in the branch where the detection point is located; otherwise, j = j + 1, and the comparison module is executed again. The positioning module is used to accurately locate the fault point after the faulty branch has been identified. The execution module is used to execute the comparison module if j≤m, otherwise it can be determined that there is no permanent single-phase grounding fault from the beginning of the line to the end of the line. The acquisition module is also used to select a certain moment after the zero-sequence current signal is injected as time zero, denoted as t0, and the phase of the zero-sequence current signal corresponding to time zero t0 is denoted as θ. t0 Using a satellite as a timing source, this source provides a synchronization signal for the controller, which functions as a signal measuring device, to distinguish between different θ values ​​located within the rising range from voltage trough to peak and the falling range from voltage peak to trough. t0 And denoted as θ respectively t0-u and θ t0-d At time t0, the zero-sequence current signal is sampled, and multiple zero-sequence current signals corresponding to θ are measured. t0-u Or θ t0-d The moment is denoted as t. in Where n = 1, 2, 3..., the detection point Q is obtained. jk The time difference t between zero-sequence voltage and zero-sequence current jk for: t jk =t in -n·(1 / f)±Δt Where Δt is the synchronization error with the clock of the signal measuring device; calculate the detection point Q. jk zero-sequence admittance angle Its expression is: In the formula: f is the frequency of the injected signal.

5. The offline overhead line single-phase grounding fault location device based on AC signal injection according to claim 4, characterized in that, The criteria in the comparison module are 6. A terminal, comprising a processor and a storage medium; The storage medium is used to store instructions; Its features are, The processor is configured to operate according to the instructions to perform the steps of the offline overhead line single-phase grounding fault location method based on AC signal injection according to any one of claims 1-3.

7. A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the offline overhead line single-phase grounding fault location method based on AC signal injection according to any one of claims 1-3.

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