Calculation method for trip-out rate of power transmission line under multiple lightning stroke conditions

Abstract

The invention discloses a method for calculating a trip-out rate of a power transmission line under multiple lightning stroke conditions. The method comprises the following steps: S1, constructing a lightning resistance level overall simulation model of the power transmission line; s2, simulating a multiple lightning current model; s3, analyzing the lightning resistance level of the n lightning strokes: separately performing simulation analysis on each frequency of lightning strokes to obtain the lightning resistance level of each frequency of lightning strokes, and then deducing a first lightning stroke amplitude I1 through a lightning current amplitude proportion, so as to perform comparison and determine the lightning resistance level of the power transmission line under the n lightning strokes; and S4, calculating the lightning stroke trip-out rate of the power transmission line under n lightning strokes: dividing the trip-out rate into a back striking trip-out rate and a shielding failure trip-out rate, respectively calculating the two parts through a related formula, and adding the two parts to obtain the lightning stroke trip-out rate of the power transmission line under n lightning strokes.

Description

Technical Field

[0001] The invention relates to the technical field of power systems, and in particular to a method for calculating a trip rate of a power transmission line under multiple lightning strike conditions. Background Art

[0002] With the rapid expansion of the scale of new energy development, the problem of high-level consumption has brought new challenges to the power system. In order to solve the problem of power transmission, it is necessary to rely on long-distance transmission, which puts higher requirements on the stability and reliability of transmission lines. Under complex geographical and meteorological conditions, the probability of transmission lines being struck by lightning is relatively high, so it is crucial to improve the lightning protection level of transmission lines. According to statistics, the proportion of tripping accidents caused by lightning strikes is relatively high in the operation of transmission lines, especially in areas with many thunders, high soil resistivity and complex terrain. The tripping rate caused by lightning strikes is higher. Moreover, most lightning presents multiple characteristics. Statistics show that the proportion of multiple lightning strikes in lightning is as high as 80%, which seriously threatens the safe operation of the power grid. Generally speaking, the peak current of subsequent lightning strikes is generally smaller than that of the first lightning strike, but because of its high steepness, whether it is the overvoltage generated on the insulator or the electromagnetic interference induced on the electrical equipment, subsequent lightning strikes may cause more serious consequences than the first lightning strike.

[0003] However, most existing studies focus on the impact of a single lightning strike or lightning intrusion waves on transmission lines under idealized conditions, while there are few studies on multiple lightning strikes. At present, there is no clear understanding of the impulse voltage amplitude suffered by the transmission line under multiple lightning strikes and the operating status of the transmission line at this time, and there is no systematic calculation and analysis method for the lightning withstand level and tripping rate of the transmission line under multiple lightning strikes. Summary of the invention

[0004] In view of this, the present invention provides a method for calculating the trip rate of a power transmission line under multiple lightning strike conditions, so as to at least solve the problem in the prior art that there is no influence of multiple lightning strikes on the power transmission line.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: A method for calculating the trip rate of a transmission line under multiple lightning strike conditions comprises the following steps: S1. Constructing an overall simulation model of the lightning resistance level of a transmission line: obtaining relevant parameters of the transmission line, and constructing an overall simulation model of the lightning resistance level of the transmission line according to the relevant parameters of the transmission line; S2. Simulate multiple lightning current model: obtain lightning parameters under multiple lightning strikes in the study area within any period of time, analyze the proportional relationship of lightning current amplitude of each frequency of lightning strikes based on lightning parameters, and simulate the lightning current waveform of each frequency of lightning strikes based on lightning current related parameters; S3. Analysis Lightning resistance level of heavy lightning strikes: The lightning current waveform of each lightning strike frequency simulated by S2 is simulated and analyzed separately to obtain the lightning resistance level of each lightning strike frequency. The lightning current amplitude of the first lightning strike is derived from the proportional relationship of the lightning current amplitude of each lightning strike frequency. , so as to compare and determine Lightning Withstand Level of Transmission Lines Under Heavy Lightning Strike ; S4. Calculation Lightning trip rate of transmission lines under heavy lightning strikes: according to the lightning resistance level Get the counter-attack trip rate and the shielding failure trip rate, and calculate according to the counter-attack trip rate and the shielding failure trip rate Lightning tripping rate of transmission lines under heavy lightning strikes.

[0006] Preferably, the overall simulation model of the lightning resistance level of the transmission line in S1 includes: a transmission line model, a tower model, an insulator string model and a lightning arrester model; Transmission line model: The JMarti frequency characteristic overhead line model is used to simulate transmission lines and lightning arresters; Tower model: The tower is simulated using a multi-wave impedance model. The tower is divided into three parts: the main body, the bracket and the cross arm. The wave impedance of each part is calculated separately. The main body includes the vertical body and the bottom body. The cross arms are horizontally arranged on both sides of the vertical body. The vertical body is divided into part; Insulator string model: A voltage-controlled switch is used to simulate the insulator string flashover model. When the voltage at both ends of the insulator string reaches 50% of the impulse discharge voltage U 50% , the voltage-controlled switch is actuated to close the switch and short-circuit, simulating the flashover of the insulator; Arrester model: Draw the arrester's volt-ampere characteristic curve by simulating the arrester's volt-ampere characteristic curve parameters.

[0007] Preferably, in the tower model, Wave impedance of a vertical body The calculation method is: , in, For the The height of a cross arm refers to the height difference between the cross arm part of the tower and the ground; , In the formula, For the The radius of the vertical body of the segment; is the horizontal distance between the two vertical bodies; is the bottom body radius; is the horizontal distance between the two bottom bodies; is the equivalent calculation radius of the tower body; Wave impedance of cross arm The calculation formula is: , In the formula, For the The equivalent calculation radius of each cross arm is one quarter of the length of a single cross arm; No. The cross arm and The wave impedance of the bracket between the cross arms The calculation method is: .

[0008] Preferably, in S2, the median of the lightning current amplitude of each lightning strike frequency is used as the lightning parameter, and the lightning current related parameters include: lightning current amplitude, time interval, lightning strike frequency and subsequent lightning strike waveform; The specific contents of S2 include: A separate lightning strike channel is added for each lightning strike, and an independent simulation analysis is performed. Based on the statistically obtained median data of lightning currents of each frequency for multiple lightning strikes of negative polarity, the amplitude ratio of lightning currents of each frequency is calculated.

[0009] Preferably, the specific content of S3 includes: Enter the Lightning current waveform, lightning current amplitude and Lightning resistance level of lines under heavy lightning strikes , gradually changing the lightning current amplitude, by observing the voltage waveforms at both ends of the three-phase insulators of the lightning-struck tower, testing the critical lightning current amplitude that causes the insulator to flash over, and thus determining the first The lightning resistance level of the tower under the lightning strike; The proportional relationship of the lightning current amplitude of each frequency lightning strike calculated in S2 is based on the The lightning current amplitude of the first lightning strike can be inferred from the lightning resistance level of the tower under the second lightning strike , and and Lightning resistance level of lines under heavy lightning strikes By comparison, we get Lightning resistance level for heavy lightning strikes The value of: If Greater than or equal to Lightning resistance level of lines under heavy lightning strikes ,but Lightning resistance level for heavy lightning strikes The value of ;if Less than Lightning resistance level of lines under heavy lightning strikes ,but Lightning resistance level for heavy lightning strikes The value of ; The lightning resistance level is the counter-strike lightning resistance level. Or lightning protection level .

[0010] Preferably, the specific content of S4 includes: Total line tripping rate under heavy lightning strike Including back-tripping rate and shielding trip rate : , In the formula, The number of lightning strikes on the tower per 100 km line in D lightning days; is the pole striking rate, which is the ratio of the number of lightning strikes on the pole tower to the total number of lightning strikes on the lines; is the arc building rate, which refers to the probability of an impulse flashover being converted into a stable power frequency arc; The lightning current amplitude exceeds the tower's lightning strike resistance level. probability; is the bypass rate; The lightning current amplitude exceeds the shielding lightning withstand level probability.

[0011] Preferably, The calculation method is: , In the formula, is the ground lightning density; is the number of days with thunder and lightning; is the average height of the upper conductor; The distance between lightning conductors; and The calculation method is: , In the formula, for or ; for or ; The calculation method is: , In the formula, is the average operating voltage gradient of the insulator string: , In the formula, is the system rated voltage, is the insulator string length, is the phase-to-phase distance of the tower crossarms. For iron crossarms and reinforced concrete crossarms, .

[0012] Preferably, the method further includes: S5. constructing a probability distribution model of multiple lightning strike severity using the lightGBM algorithm to obtain a weighted trip rate of a transmission line with different lightning strike severity, wherein the specific method is: (1) Data collection: Obtain lightning strike data of historical lightning events and their corresponding meteorological data as a data set; (2) Data preprocessing: After interpolating and cleaning the data set using the K-nearest neighbor interpolation method, both the lightning strike data and the meteorological data were normalized; (3) Model training: The preprocessed data set is divided into training set, test set and validation set. The LightGBM model is optimized through training parameter adjustment and cross-validation. The optimized LightGBM model is tested and evaluated through the sample set to obtain the final LightGBM model. (4) Prediction of lightning strike severity probability distribution: Using the final LightGBM model, input lightning strike data and meteorological data within any historical period, and output the probability distribution of lightning strike severity: , in, for Probability distribution of heavy lightning strikes; (5) The tripping rate for high-severity lightning strikes, i.e. When the probability is greater than or equal to 3, a probability correction module based on the attention mechanism is introduced, and the corrected probability is: , in, is an empirical parameter; Replace the corrected probability middle The probability is greater than or equal to 3, and the probability distribution after replacement is obtained ; (6) Dynamic update mechanism: When new lightning strike data is added, the model parameters are updated through incremental training to maintain the real-time prediction. Combined with real-time meteorological warning data, the model parameters are dynamically adjusted through online learning to ensure that the probability distribution of lightning strike severity changes dynamically with the weather and that the calculation results are more in line with the actual situation. The model is retrained every preset time period to avoid concept drift. (7) Weighted trip rate calculation framework: Replace the probability distribution As a weight, Total line tripping rate under heavy lightning strike Perform weighted summation to obtain the weighted trip rate of the transmission line: .

[0013] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a method for calculating the trip rate of a transmission line under multiple lightning strike conditions, which has the following beneficial effects: (1) The present invention proposes a systematic calculation method for the tripping rate under multiple lightning strikes. By constructing an accurate lightning strike simulation model, the tripping rate of a transmission line under n lightning strikes can be calculated. The method is suitable for calculating the tripping rate under multiple lightning strikes with different lightning strike frequencies.

[0014] (2) When calculating the tripping rate, the present invention takes into account the counter-tripping rate caused by multiple lightning strikes on pole towers and lightning conductors and the direct tripping rate caused by lightning strikes on conductors, and proposes a comprehensive calculation method for all situations that affect the lightning tripping rate of distribution lines, which is comprehensive and universally applicable.

[0015] (3) The present invention can customize multiple lightning current parameters, transmission line parameters, tower parameters, grounding resistance parameters, lightning arrester parameters, etc., with strong flexibility and pertinence, and can perform on-the-fly calculations on the tripping rates of transmission lines under different tower shapes and circuits.

[0016] (4) The present invention can be used to guide the optimization design of lightning protection for power transmission lines and has practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 A schematic diagram of a tower model provided by an embodiment of the present invention; Figure 2 A schematic diagram of a multi-wave impedance model provided by an embodiment of the present invention; Figure 3 A simulation diagram of the volt-ampere characteristic curve of a lightning arrester provided in an embodiment of the present invention Figure 4 Lightning current waveform diagram provided by an embodiment of the present invention; (a) first lightning strike; (b) second lightning strike; (c) third lightning strike; (d) fourth lightning strike; (e) fifth lightning strike; Figure 5 A structural diagram of the overall simulation model of a power transmission line provided by an embodiment of the present invention; Figure 6 A flow chart for calculating the line trip rate under n-weight lightning strikes provided by an embodiment of the present invention; Figure 7 A flowchart for constructing the final LightGBM model provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] The present invention provides a method for calculating the trip rate of a power transmission line under multiple lightning strike conditions, comprising the following steps: S1. Constructing an overall simulation model of the lightning resistance level of a transmission line: obtaining relevant parameters of the transmission line, and constructing an overall simulation model of the lightning resistance level of the transmission line according to the relevant parameters of the transmission line; S2. Simulate multiple lightning current model: obtain lightning parameters under multiple lightning strikes in the study area within any period of time, analyze the proportional relationship of lightning current amplitude of each frequency of lightning strikes based on lightning parameters, and simulate the lightning current waveform of each frequency of lightning strikes based on lightning current related parameters; S3. Analysis Lightning resistance level of heavy lightning strikes: The lightning current waveform of each lightning strike frequency simulated by S2 is simulated and analyzed separately to obtain the lightning resistance level of each lightning strike frequency. The lightning current amplitude of the first lightning strike is derived from the proportional relationship of the lightning current amplitude of each lightning strike frequency. , so as to compare and determine Lightning resistance level of transmission lines under heavy lightning strikes ; S4. Calculation Lightning trip rate of transmission lines under heavy lightning strikes: according to the lightning resistance level Get the counter-attack trip rate and the shielding failure trip rate, and calculate according to the counter-attack trip rate and the shielding failure trip rate Lightning tripping rate of transmission lines under heavy lightning strikes.

[0021] It should be noted that: Transmission line related parameters include transmission line, tower, insulator string, lightning arrester and other related parameters.

[0022] Lightning current related parameters include the amplitude of lightning current, the wave head of lightning current, the wavelength, and the steepness of lightning current.

[0023] In order to further implement the above technical solutions, the overall simulation model of the lightning resistance level of the transmission line in S1 includes: transmission line model, tower model, insulator string model and arrester model; Transmission line model: The JMarti frequency characteristic overhead line model is used to simulate transmission lines and lightning arresters; Tower model: The tower is simulated using a multi-wave impedance model. The tower is divided into three parts: the main body, the bracket and the cross arm. The wave impedance of each part is calculated separately. The main body includes the vertical body and the bottom body. The cross arms are horizontally arranged on both sides of the vertical body. The vertical body is divided into part; Insulator string model: A voltage-controlled switch is used to simulate the insulator string flashover model. When the voltage at both ends of the insulator string reaches 50% of the impulse discharge voltage U 50% , the voltage-controlled switch is actuated to close the switch and short-circuit, simulating the flashover of the insulator; Arrester model: Draw the arrester's volt-ampere characteristic curve by simulating the arrester's volt-ampere characteristic curve parameters.

[0024] It should be noted that: Investigate and count the relevant parameters of transmission lines, towers, insulator strings, lightning arresters, etc., and build models of transmission lines, towers, insulator strings, grounding resistance and lightning arresters in ATP-EMTP software based on these parameters to form an overall simulation model of the lightning resistance level of transmission lines, which is used for simulation analysis of the lightning resistance level.

[0025] Transmission line model: In the current lightning protection design of transmission lines, two lightning conductors are generally installed, forming a three-phase five-wire (three transmission lines) form. When performing simulation, the JMarti frequency characteristic overhead line model is generally used. This model takes into account the variation of parameters with frequency and the coupling coefficient between the ground wire and the conductor. The simulation results are close to the actual situation. In this embodiment, the JMarti model is used to simulate the transmission line and lightning conductor, and the LCC module in the ATP-EMTP software is used for fitting; Tower model: The present invention uses a multi-wave impedance model to simulate the tower. The model is established based on the different wave impedances at different heights of the vertical conductor. Taking into account the propagation process of the wave in the tower, it has obvious advantages in lightning strike calculations, and the calculation results are more accurate. The simulation structure is as follows: Figure 1~2 As shown, Figure 1 This is a schematic diagram of the tower. Figure 2 This is the corresponding multi-wave impedance model diagram.

[0026] Insulator string model: In the current industry standards and projects, the judgment of whether the insulator flashes is mainly based on comparing the overvoltage at both ends of the insulator string with the 50% impulse discharge voltage U of the insulator string. 50% If the overvoltage exceeds U 50% , that is, it is judged as flashover. This embodiment uses this method to judge insulator flashover and uses a voltage-controlled switch to simulate an insulator string flashover model.

[0027] Arrester model: In the ATP-EMTP software, a 92-type nonlinear resistor element is used to simulate the arrester. By inputting the arrester's volt-ampere characteristic curve parameters, its volt-ampere characteristic curve can be simulated and drawn, such as Figure 3 shown.

[0028] In order to further implement the above technical solution, in the tower model, k Wave impedance of a vertical body The calculation method is: , in, For the The height of a cross arm refers to the height difference between the cross arm part of the tower and the ground; , In the formula, For the The radius of the vertical body of the segment; is the horizontal distance between the two vertical bodies; is the bottom body radius; is the horizontal distance between the two bottom bodies; is the equivalent calculation radius of the tower body; Wave impedance of cross arm The calculation formula is: , In the formula, For the The equivalent calculation radius of each cross arm is one quarter of the length of a single cross arm; No. The cross arm and The wave impedance of the bracket between the cross arms The calculation method is: .

[0029] It should be noted that: From operational experience, we know that if the tower has a support, its wave impedance is 0.9 times that of the tower without a support. Therefore, we can get the equivalent wave impedance of the tower support part. .

[0030] In order to further implement the above technical solution, in S2, the median of the lightning current amplitude of each lightning strike frequency is used as the lightning parameter, and the lightning current related parameters include: lightning current amplitude, time interval, lightning strike frequency and subsequent lightning strike waveform; The specific contents of S2 include: A separate lightning strike channel is added for each lightning strike, and an independent simulation analysis is performed. Based on the statistically obtained median data of lightning currents of each frequency for multiple lightning strikes of negative polarity, the amplitude ratio of lightning currents of each frequency is calculated.

[0031] It should be noted that: In this embodiment, lightning parameters such as lightning current amplitude, time interval, return stroke frequency and subsequent return stroke waveform of multiple lightning strikes in the studied area in the past five years are statistically analyzed, the proportional relationship of the amplitude of each lightning strike is analyzed based on the statistical data, and the lightning current waveform of each lightning strike is simulated according to the relevant parameters.

[0032] The subsequent lightning waveform refers to the lightning waveform after the first lightning strike; Multiple lightning current simulation scheme: When a transmission line is struck by lightning, the lightning overvoltage generated on the line will decay rapidly and tend to a steady state after about 1ms. According to statistical data, the average interval time of multiple lightning strikes is about 140.5ms, which is significantly longer than the decay time of lightning overvoltage. Therefore, without considering energy accumulation, a separate lightning strike channel can be added for each lightning strike for independent simulation analysis. Based on the statistically obtained median data of lightning currents of each frequency of multiple lightning strikes with negative polarity, the amplitude ratio of lightning currents of each frequency is calculated for subsequent analysis of the lightning resistance level of transmission lines under multiple lightning strikes.

[0033] In the ATP-EMTP software, the built-in lightning current model can be connected in parallel with the wave impedance to create an equivalent lightning channel. When the line is struck back, the wave impedance of the lightning channel is set to 300Ω; when the line is struck by a shielding failure, the wave impedance of the lightning channel is set to 800Ω. The waveforms of each lightning strike fitted in the software are as follows: Figure 4 shown.

[0034] The lightning current waveform is simulated by inputting lightning current amplitude, wave head, wavelength and steepness data into the Heidler model.

[0035] In order to further implement the above technical solutions, the specific contents of S3 include: Enter the Lightning current waveform, lightning current amplitude and Lightning resistance level of lines under heavy lightning strikes , gradually changing the lightning current amplitude, by observing the voltage waveforms at both ends of the three-phase insulators of the lightning-struck tower, testing the critical lightning current amplitude that causes the insulator to flash over, and thus determining the first The lightning resistance level of the tower under the lightning strike; The proportional relationship of the lightning current amplitude of each frequency lightning strike calculated in S2 is based on the The lightning current amplitude of the first lightning strike can be inferred from the lightning resistance level of the tower under the second lightning strike , and and Lightning resistance level of lines under heavy lightning strikes By comparison, we get Lightning resistance level for heavy lightning strikes The value of: If Greater than or equal to Lightning resistance level of lines under heavy lightning strikes ,but Lightning resistance level for heavy lightning strikes The value of ;if Less than Lightning resistance level of lines under heavy lightning strikes ,but Lightning resistance level for heavy lightning strikes The value of ; The lightning resistance level is the counter-strike lightning resistance level. Or lightning protection level .

[0036] It should be noted that: Finally, the overall lightning resistance level simulation model of the transmission line is constructed as follows: Figure 5 shown.

[0037] In order to further implement the above technical solution, the specific contents of S4 include: Total line tripping rate under heavy lightning strike Including back-tripping rate and shielding trip rate : , In the formula, The number of lightning strikes on the tower per 100 km line in D lightning days; is the pole striking rate, which is the ratio of the number of lightning strikes on the pole tower to the total number of lightning strikes on the lines; is the arc building rate, which refers to the probability of an impulse flashover being converted into a stable power frequency arc; The lightning current amplitude exceeds the tower's lightning strike resistance level. The probability of is the bypass rate; The lightning current amplitude exceeds the shielding lightning withstand level probability.

[0038] It should be noted that: In this embodiment, D is 40, where the lightning trip rate refers to the number of trips caused by lightning strikes per 100 kilometers of line and 40 lightning days. It is a comprehensive indicator to measure the lightning protection performance of the line. The present invention proposes a method for calculating the trip rate of a transmission line under n-fold lightning strikes. The specific flow chart is as follows: Figure 6 As shown, the lightning current amplitude is changed successively and is set to increase by 1 each time based on the original lightning current amplitude.

[0039] From the perspective of the lightning strike location, the counterattack includes two parts: one is the lightning strike on the tower top and the lightning conductor near the tower, and the other is the lightning strike in the center of the lightning conductor span. As long as the air gap meets the requirements of the regulations, the lightning strike in the center of the lightning conductor span generally will not cause flashover, so it can be considered that the counterattack trip rate is mainly determined by the first situation.

[0040] The pole striking rate of different numbers of lightning protection wires and line corridor terrain For specific values, please refer to Table 1.

[0041] Table 1 The hit rate of different lines .

[0042] In order to further implement the above technical solution, The calculation method is: , In the formula, is the ground lightning density; is the number of days with thunder and lightning; is the average height of the upper conductor; The distance between lightning conductors; and The calculation method is: , In the formula, for or ; for or ; The calculation method is: , In the formula, is the average operating voltage gradient of the insulator string: , In the formula, is the system rated voltage, is the insulator string length, is the phase-to-phase distance of the tower crossarms. For iron crossarms and reinforced concrete crossarms, .

[0043] In order to further implement the above scheme, it also includes: S5. Using the lightGBM algorithm to construct a probability distribution model of multiple lightning strike severity, and obtain the weighted tripping rate of the transmission line including different lightning strike severity, the specific method is: (1) Data collection: Obtain lightning strike data of historical lightning events and their corresponding meteorological data as a data set; (2) Data preprocessing: After interpolating and cleaning the data set using the K-nearest neighbor interpolation method, both the lightning strike data and the meteorological data were normalized; (3) Model training: The preprocessed data set is divided into training set, test set and validation set. The LightGBM model is optimized through training parameter adjustment and cross-validation. The optimized LightGBM model is tested and evaluated through the sample set to obtain the final LightGBM model. (4) Prediction of lightning strike severity probability distribution: Using the final LightGBM model, input lightning strike data and meteorological data within any historical period, and output the probability distribution of lightning strike severity: , in, for Probability distribution of heavy lightning strikes; (5) The tripping rate for high-severity lightning strikes, i.e. When the probability is greater than or equal to 3, a probability correction module based on the attention mechanism is introduced, and the corrected probability is: , in, is an empirical parameter; Replace the corrected probability middle The probability is greater than or equal to 3, and the probability distribution after replacement is obtained ; (6) Dynamic update mechanism: When new lightning strike data is added, the model parameters are updated through incremental training to maintain the real-time prediction. Combined with real-time meteorological warning data, the model parameters are dynamically adjusted through online learning to ensure that the probability distribution of lightning strike severity changes dynamically with the weather and that the calculation results are more in line with the actual situation. The model is retrained every preset time period to avoid concept drift. (7) Weighted trip rate calculation framework: Replace the probability distribution As a weight, Total line tripping rate under heavy lightning strike Perform weighted summation to obtain the weighted trip rate of the transmission line: .

[0044] It should be noted that: The flowchart for building the final LightGBM model is as follows Figure 7 As shown; In this embodiment, lightning strike data (lightning strike severity, lightning strike intensity, lightning strike location, etc.) and meteorological data (temperature and humidity, wind speed, air pressure, etc.) of historical lightning events are obtained from lightning location networks, meteorological satellites, etc.

[0045] After the K-nearest neighbor interpolation method was used to interpolate and clean the data set, both the lightning strike data and meteorological characteristic variables were normalized to eliminate the messy data and improve the data accuracy.

[0046] During the model training process, the dataset is divided into training set, test set, and validation set in a ratio of 7:2:1.

[0047] In the process of predicting the probability distribution of lightning strike severity and in the process of dynamically updating the mechanism, any historical time period and preset time period can be selected with a specific duration according to actual conditions, such as one month.

[0048] Aiming at the tripping rate of high-multiple lightning strikes (such as more than 3 times), a probability correction module based on the attention mechanism is introduced, and its weight is amplified by an exponential function to reflect the effect of multiple lightning strikes on the cumulative damage of insulators.

[0049] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A method for calculating the trip rate of a transmission line under multiple lightning strikes, characterized in that: The following steps are involved: S1. Constructing an overall simulation model of the lightning resistance level of a transmission line: obtaining relevant parameters of the transmission line, and constructing an overall simulation model of the lightning resistance level of the transmission line according to the relevant parameters of the transmission line; S2. Simulate multiple lightning current model: obtain lightning parameters under multiple lightning strikes in the study area within any period of time, analyze the proportional relationship of lightning current amplitude of each frequency of lightning strikes based on lightning parameters, and simulate the lightning current waveform of each frequency of lightning strikes based on lightning current related parameters; S3. Analysis Lightning resistance level of heavy lightning strikes: The lightning current waveform of each lightning strike frequency simulated by S2 is simulated and analyzed separately to obtain the lightning resistance level of each lightning strike frequency. The lightning current amplitude of the first lightning strike is derived from the proportional relationship of the lightning current amplitude of each lightning strike frequency. , so as to compare and determine Lightning Withstand Level of Transmission Lines Under Heavy Lightning Strike ; The specific contents of S3 include: Enter the Lightning current waveform, lightning current amplitude and Lightning resistance level of lines under heavy lightning strikes , gradually changing the lightning current amplitude, by observing the voltage waveforms at both ends of the three-phase insulators of the lightning-struck tower, testing the critical lightning current amplitude that causes the insulator to flash over, and thus determining the first The lightning resistance level of the tower under the lightning strike; The proportional relationship of the lightning current amplitude of each frequency lightning strike calculated in S2 is based on the The lightning current amplitude of the first lightning strike can be inferred from the lightning resistance level of the tower under the second lightning strike , and and Lightning resistance level of lines under heavy lightning strikes By comparison, we get Lightning resistance level for heavy lightning strikes The value of: If Greater than or equal to Lightning resistance level of lines under heavy lightning strikes ,but Lightning resistance level for heavy lightning strikes The value of ;if Less than Lightning resistance level of lines under heavy lightning strikes ,but Lightning resistance level for heavy lightning strikes The value of ; The lightning resistance level is the counter-strike lightning resistance level. Or lightning protection level ; S4. Calculation Lightning trip rate of transmission lines under heavy lightning strikes: according to the lightning resistance level Get the counter-attack trip rate and the shielding failure trip rate, and calculate according to the counter-attack trip rate and the shielding failure trip rate Lightning tripping rate of transmission lines under heavy lightning strikes.

2. The method for calculating the trip rate of a power transmission line under multiple lightning strikes according to claim 1, characterized in that: The overall simulation model of the lightning resistance level of the transmission line in S1 includes: transmission line model, tower model, insulator string model and arrester model; Transmission line model: The JMarti frequency characteristic overhead line model is used to simulate transmission lines and lightning arresters; Tower model: The tower is simulated using a multi-wave impedance model. The tower is divided into three parts: the main body, the bracket and the cross arm. The wave impedance of each part is calculated separately. The main body includes the vertical body and the bottom body. The cross arms are horizontally arranged on both sides of the vertical body. The vertical body is divided into part; Insulator string model: A voltage-controlled switch is used to simulate the insulator string flashover model. When the voltage at both ends of the insulator string reaches 50% of the impulse discharge voltage U 50% , the voltage-controlled switch is actuated to close the switch and short-circuit, simulating the flashover of the insulator; Arrester model: Draw the arrester's volt-ampere characteristic curve by simulating the arrester's volt-ampere characteristic curve parameters.

3. The method for calculating the trip rate of a power transmission line under multiple lightning strikes according to claim 2, characterized in that: In the tower model, Wave impedance of a vertical body The calculation method is: ， in, For the The height of a cross arm refers to the height difference between the cross arm part of the tower and the ground; ， In the formula, For the The radius of the vertical body of the segment; is the horizontal distance between the two vertical bodies; is the bottom body radius; is the horizontal distance between the two bottom bodies; is the equivalent calculation radius of the tower body; Wave impedance of cross arm The calculation formula is: ， In the formula, For the The equivalent calculation radius of each cross arm is one quarter of the length of a single cross arm; No. The cross arm and The wave impedance of the bracket between the cross arms The calculation method is: 。 4. The method for calculating the trip rate of a power transmission line under multiple lightning strikes according to claim 1, characterized in that: In S2, the median of the lightning current amplitude of each lightning strike frequency is used as the lightning parameter. The lightning current related parameters include: lightning current amplitude, time interval, lightning strike frequency and subsequent lightning strike waveform; The specific contents of S2 include: A separate lightning strike channel is added for each lightning strike, and an independent simulation analysis is performed. Based on the statistically obtained median data of lightning currents of each frequency for multiple lightning strikes of negative polarity, the amplitude ratio of lightning currents of each frequency is calculated.

5. The method for calculating the trip rate of a power transmission line under multiple lightning strikes according to claim 1, characterized in that: The specific contents of S4 include: Total line tripping rate under heavy lightning strike Including back-tripping rate and shielding trip rate : ， In the formula, The number of lightning strikes on the tower per 100 km line in D lightning days; is the pole striking rate, which is the ratio of the number of lightning strikes on the pole tower to the total number of lightning strikes on the lines; is the arc building rate, which refers to the probability of an impulse flashover being converted into a stable power frequency arc; The lightning current amplitude exceeds the tower's lightning strike resistance level. probability; is the bypass rate; The lightning current amplitude exceeds the shielding lightning withstand level probability.

6. The method for calculating the trip rate of a power transmission line under multiple lightning strikes according to claim 5, characterized in that: The calculation method is: ， In the formula, is the ground lightning density; is the number of days with thunder and lightning; is the average height of the upper conductor; The distance between lightning conductors; and The calculation method is: ， In the formula, for or ; for or ; The calculation method is: ， In the formula, is the average operating voltage gradient of the insulator string: ， In the formula, is the system rated voltage, is the insulator string length, is the phase-to-phase distance of the tower crossarms. For iron crossarms and reinforced concrete crossarms, .

7. The method for calculating the trip rate of a power transmission line under multiple lightning strikes according to claim 5, characterized in that: Also includes: S5. Use the lightGBM algorithm to build a probability distribution model of multiple lightning strike severity and obtain the weighted trip rate of transmission lines with different lightning strike severity. The specific method is as follows: (1) Data collection: Obtain lightning strike data of historical lightning events and their corresponding meteorological data as a data set; (2) Data preprocessing: After interpolating and cleaning the data set using the K-nearest neighbor interpolation method, both the lightning strike data and the meteorological data were normalized; (3) Model training: The preprocessed data set is divided into training set, test set and validation set. The LightGBM model is optimized through training parameter adjustment and cross-validation. The optimized LightGBM model is tested and evaluated through the sample set to obtain the final LightGBM model. (4) Prediction of lightning strike severity probability distribution: Using the final LightGBM model, input lightning strike data and meteorological data within any historical period, and output the probability distribution of lightning strike severity: ， in, for Probability distribution of heavy lightning strikes; (5) The tripping rate for high-severity lightning strikes, i.e. When the probability is greater than or equal to 3, a probability correction module based on the attention mechanism is introduced, and the corrected probability is: ， in, is an empirical parameter; Replace the corrected probability middle The probability is greater than or equal to 3, and the probability distribution after replacement is obtained ; (6) Dynamic update mechanism: When new lightning strike data is added, the model parameters are updated through incremental training to maintain the real-time prediction. Combined with real-time meteorological warning data, the model parameters are dynamically adjusted through online learning to ensure that the probability distribution of lightning strike severity changes dynamically with the weather and that the calculation results are more in line with the actual situation. The model is retrained every preset time period to avoid concept drift. (7) Weighted trip rate calculation framework: Replace the probability distribution As a weight, Total line tripping rate under heavy lightning strike Perform weighted summation to obtain the weighted trip rate of the transmission line: 。

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