A Calculation Method for Tripping Rate of Transmission Lines under Multiple Lightning Strike Conditions

Abstract

The present invention discloses a method for calculating the tripping rate of a transmission line under multiple lightning strike conditions, comprising the following steps: S1. Construct an overall simulation model of the lightning withstand level of the transmission line; S2. Simulate a multiple lightning current model; S3. Analyze the lightning withstand level of n-fold lightning strikes: separately simulate and analyze each lightning strike frequency, obtain the lightning withstand level of each lightning strike frequency, and then derive the amplitude I1 of the first lightning strike through the lightning current amplitude ratio, so as to make a comparison and determine the lightning withstand level of the transmission line under n-fold lightning strikes; S4. Calculate the lightning tripping rate of the transmission line under n-fold lightning strikes: the tripping rate is divided into the back-strike tripping rate and the shielding failure tripping rate. Calculate the two parts separately through relevant formulas and add them up to obtain the lightning tripping rate of the transmission line under n-fold lightning strikes.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and particularly relates to a method for calculating the tripping rate of a 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. To solve the problem of power transmission, long-distance power transmission is required, 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. Therefore, it is crucial to improve the lightning protection level of transmission lines. According to statistics, among the tripping accidents that occur during the operation of transmission lines, the proportion caused by lightning strikes is relatively high. Especially in areas with frequent lightning, high soil resistivity, and complex terrain, the tripping rate caused by lightning strikes is even higher. Moreover, lightning mostly exhibits multiple characteristics. Statistical data shows that the proportion of multiple lightning strikes in lightning is as high as 80%, seriously threatening the safe operation of the power grid. Generally speaking, the peak value of the subsequent lightning strike current is generally smaller than that of the first lightning strike current. However, due to its high steepness, whether it is the overvoltage generated on the insulator or the electromagnetic interference induced on electrical equipment, the subsequent lightning strike may cause more serious consequences than the first lightning strike.

[0003] However, most of the existing research focuses on the impact of single lightning strikes or lightning intrusion waves under idealized conditions on transmission lines, and there is little relevant research on the situation of multiple lightning strikes. Currently, there is no clear understanding of the amplitude of the impact voltage suffered by the transmission line under multiple lightning strike conditions and the operating state of the transmission line at this time, and no systematic calculation and analysis method for the lightning withstand level and tripping rate of the transmission line under multiple lightning strikes is given. Summary of the Invention

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

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for calculating the tripping rate of a transmission line under multiple lightning strike conditions includes the following steps:

[0007] S1. Construct an overall simulation model of the lightning withstand level of the transmission line: Obtain the relevant parameters of the transmission line, and construct an overall simulation model of the lightning withstand level of the transmission line according to the relevant parameters of the transmission line;

[0008] S2. Simulate the multiple lightning current model: Obtain the lightning parameters under multiple lightning strikes in the study area at any time period, analyze the proportional relationship of the lightning current amplitude for each lightning strike according to the lightning parameters, and simulate the lightning current waveform for each lightning strike based on the relevant parameters of the lightning current.

[0009] S3. Analyze The lightning withstand level of multiple lightning strikes: Separately conduct simulation analysis on the lightning current waveforms of each lightning strike simulated in S2 to obtain the lightning withstand levels of each lightning strike, and deduce the lightning current amplitude of the first lightning strike through the proportional relationship of the lightning current amplitude of each lightning strike so as to make comparisons and determine the lightning withstand level of the transmission line under multiple lightning strikes ;

[0010] S4. Calculate The lightning trip rate of the transmission line under multiple lightning strikes: Obtain the back flashover trip rate and the shielding failure trip rate according to the lightning withstand level and calculate the lightning trip rate of the transmission line under multiple lightning strikes.

[0011] Preferably, the overall simulation model of the lightning withstand level of the transmission line in S1 includes: a transmission line model, a tower model, an insulator string model, and a lightning arrester model;

[0012] Transmission line model: Use the JMarti frequency characteristic overhead line model to simulate the transmission line and the shield wire;

[0013] Tower model: Use the multi-wave impedance model to simulate the tower. Divide the tower into three parts: the main body, the support, and the crossarm, and calculate the wave impedance of each part respectively; among them, the main body includes the vertical main body and the bottom main body, the crossarm is horizontally arranged on both sides of the vertical main body, and the number of crossarms in the vertical direction divides the vertical main body into sections;

[0014] Insulator string model: Use a voltage-controlled switch 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% of the insulator string, the voltage-controlled switch acts to close the switch and short-circuit, simulating the situation of insulator flashover;

[0015] Lightning arrester model: Simulate and draw the volt-ampere characteristic curve of the lightning arrester through the volt-ampere characteristic curve parameters of the lightning arrester.

[0016] Preferably, in the tower model, the calculation method of the wave impedance of the th section of the vertical main body is:

[0017] ,

[0018] Among them, is the height of the th crossarm, which refers to the height difference between the crossarm part of the pole tower and the ground;

[0019] ,

[0020] In the formula, is the radius of the th vertical main body; is the horizontal distance between the two vertical main bodies; is the bottom main body radius; is the horizontal distance between the two bottom main bodies; is the equivalent calculation radius of the pole tower main body;

[0021] The wave impedance of the crossarm part The calculation formula method is:

[0022] ,

[0023] In the formula, is the equivalent calculation radius of the th crossarm, and the value is one-fourth of the single crossarm length;

[0024] The th crossarm and the th crossarm, the wave impedance of the bracket between them The calculation method is:

[0025] .

[0026] Preferably, in S2, the median value of the lightning current amplitude of each lightning strike 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;

[0027] The specific content of S2 includes:

[0028] Separate lightning strike channels are added for each lightning strike for independent simulation analysis; according to the median data of the lightning current of each frequency of negative multiple lightning strikes obtained by statistics, the amplitude ratio of the lightning current of each frequency is calculated.

[0029] Preferably, the specific content of S3 includes:

[0030] Input the lightning current waveform, lightning current amplitude of the th lightning strike and the lightning withstand level of the line under multiple lightning strikes , gradually change the lightning current amplitude, and by observing the voltage waveforms at both ends of the three-phase insulators of the lightning-struck tower, test the critical lightning current amplitude that causes the insulator to experience lightning flashover, so as to determine the lightning withstand level of the tower under the th lightning strike;

[0031] Based on the proportional relationship of the lightning current amplitude for each lightning strike frequency calculated in S2, and according to the lightning withstand level of the tower under the th lightning strike, inversely deduce the lightning current amplitude of the first lightning strike , and Compare with the lightning withstand level of the line under multiple lightning strikes to obtain the value of the lightning withstand level of multiple lightning strikes : If is greater than or equal to the lightning withstand level of the line under multiple lightning strikes , then the value of the lightning withstand level of multiple lightning strikes is ; If is less than the lightning withstand level of the line under multiple lightning strikes , then the value of the lightning withstand level of multiple lightning strikes is ;

[0032] Among them, the lightning withstand level is the back-striking lightning withstand level or the shielding failure lightning withstand level .

[0033] Preferably, the specific content of S4 includes:

[0034] The total line tripping rate under multiple lightning strikes includes the back-striking tripping rate and the shielding failure tripping rate :

[0035] ,

[0036] In the formula, is the number of lightning strikes on the tower per 100 km of line under D lightning days; is the strike rate on the tower, that is, the ratio of the number of lightning strikes on the tower to the total number of lightning strikes on the line; is the arc-building rate, which is the probability that an impulse flashover is converted into a stable power-frequency arc; is the probability that the lightning current amplitude exceeds the back-striking lightning withstand level of the tower ; is the shielding failure rate; is the probability that the lightning current amplitude exceeds the shielding failure lightning withstand level probability

[0037] Preferably The calculation method is as follows

[0038] ,

[0039] In the formula is the ground lightning strike density is the number of lightning days is the average height of the upper conductor is the distance between shield wires

[0040] and The calculation method is as follows

[0041] ,

[0042] In the formula is or ; is or ;

[0043] The calculation method is as follows

[0044] ,

[0045] In the formula is the average operating voltage gradient of the insulator string

[0046] ,

[0047] In the formula is the system rated voltage is the length of the insulator string is the phase distance of the cross arm of the pole tower. For iron cross arm and reinforced concrete cross arm lines .

[0048] Preferably, it further includes: S5. Using the lightGBM algorithm to construct a probability distribution model of multiple lightning strike multiplicities, and obtaining the weighted tripping rate of the transmission line including different lightning strike multiplicities. The specific method is as follows

[0049] (1) Data collection: Obtain the lightning strike data of historical lightning events and their corresponding meteorological data as a data set

[0050] (2) Data preprocessing: After interpolating and cleaning the data set using the K-nearest neighbor interpolation method, normalize both the lightning strike data and the meteorological data

[0051] (3) Model training: Divide the preprocessed dataset into a training set, a test set, and a validation set. Optimize the LightGBM model through training parameter tuning and cross-validation methods. Use the sample set to test and evaluate the optimized LightGBM model to obtain the final LightGBM model;

[0052] (4) Lightning strike multiplicity probability distribution prediction: Use the final LightGBM model, input the lightning strike data and meteorological data within any historical time period, and output the probability distribution of the lightning strike multiplicity:

[0053] ,

[0054] where, is the probability distribution of heavy lightning strikes;

[0055] (5) For the tripping rate of high multiplicity lightning strikes, that is, when it is greater than or equal to 3, introduce a probability correction module based on the attention mechanism. The corrected probability is:

[0056] ,

[0057] where, is an empirical parameter;

[0058] Replace the probability in that is greater than or equal to 3 with the corrected probability to obtain the replaced probability distribution ; ;

[0059] (6) Dynamic update mechanism: When new lightning strike data is added, update the model parameters through incremental training to maintain prediction real-time; Combine real-time meteorological warning data, and dynamically adjust the model parameters through online learning to ensure that the probability distribution of lightning strike multiplicity changes dynamically with the weather, ensuring that the calculation results are more in line with the actual situation; And retrain the model every preset time period to avoid concept drift;

[0060] (7) Weighted tripping rate calculation framework: Use the replaced probability distribution as the weight, and perform weighted summation on the total line tripping rate under heavy lightning strikes to obtain the weighted tripping rate of the transmission line:

[0061] .

[0062] It can be seen from the above technical solutions that compared with the prior art, the present invention discloses a method for calculating the tripping rate of a transmission line under multiple lightning strike conditions, which has the following beneficial effects:

[0063] (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, it can calculate the tripping rate of transmission lines under n-fold lightning strikes and is applicable to the calculation of the tripping rate under multiple lightning strikes with different lightning strike frequencies.

[0064] (2)When calculating the tripping rate, the present invention takes into account the back-striking tripping rate caused by multiple lightning strikes on the tower and shield wire and the direct-striking tripping rate caused by lightning strikes on the conductor, and proposes a comprehensive calculation method for all situations affecting the lightning strike tripping rate of distribution lines, which has comprehensive and universal applicability.

[0065] (3)The present invention can customize multiple lightning current parameters, transmission line parameters, tower parameters, grounding resistance parameters, arrester parameters, etc., and has strong flexibility and pertinence. It can calculate the tripping rate under different tower shapes and circuits of transmission lines.

[0066] (4)The present invention can be used to guide the lightning protection optimization design of transmission lines and has practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0068] Figure 1 Schematic diagram of the tower model provided by the embodiment of the present invention;

[0069] Figure 2 Schematic diagram of the multi-wave impedance model provided by the embodiment of the present invention;

[0070] Figure 3 Simulation diagram of the volt-ampere characteristic curve of the arrester provided by the embodiment of the present invention

[0071] Figure 4 Lightning current waveform diagram provided by the 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;

[0072] Figure 5 Structural diagram of the overall simulation model of the transmission line provided by the embodiment of the present invention;

[0073] Figure 6 Flow chart for calculating the line tripping rate under n-fold lightning strikes provided by the embodiment of the present invention;

[0074] Figure 7 Flow chart for constructing the final LightGBM model provided by the embodiment of the present invention. Specific Embodiment

[0075] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0076] The present invention provides a method for calculating the tripping rate of a transmission line under multiple lightning strike conditions, including the following steps:

[0077] S1. Construct an overall simulation model of the lightning withstand level of the transmission line: Obtain the relevant parameters of the transmission line, and construct an overall simulation model of the lightning withstand level of the transmission line according to the relevant parameters of the transmission line;

[0078] S2. Simulate the multiple lightning current model: Obtain the lightning parameters under multiple lightning strike conditions in the study area at any time period, analyze the proportional relationship of the lightning current amplitudes for each lightning strike frequency according to the lightning parameters, and simulate the lightning current waveforms for each lightning strike frequency respectively according to the relevant parameters of the lightning current;

[0079] S3. Analyze the lightning withstand level of the multiple lightning strikes: Conduct simulation analysis on the lightning current waveforms of each lightning strike frequency simulated in S2 separately, obtain the lightning withstand levels of each lightning strike frequency, and deduce the lightning current amplitude of the first lightning strike through the proportional relationship of the lightning current amplitudes of each lightning strike frequency so as to make comparisons and determine the lightning withstand level of the transmission line under multiple lightning strikes ;

[0080] S4. Calculate the lightning strike tripping rate of the transmission line under multiple lightning strikes: Obtain the back-strike tripping rate and the shielding failure tripping rate according to the lightning withstand level and calculate the lightning strike tripping rate of the transmission line under multiple lightning strikes according to the back-strike tripping rate and the shielding failure tripping rate.

[0081] It should be noted that:

[0082] The relevant parameters of the transmission line include the relevant parameters of the transmission line, tower, insulator string, lightning arrester, etc.

[0083] The relevant parameters of the lightning current include the amplitude of the lightning current, the front time of the lightning current, the wavelength, and the steepness of the lightning current.

[0084] To further implement the above technical solution, the overall simulation model of the lightning withstand level of the transmission line in S1 includes: a transmission line model, a tower model, an insulator string model, and a lightning arrester model;

[0085] Transmission line model: The JMarti frequency characteristic overhead line model is used to simulate the transmission line and the lightning protection line;

[0086] Tower model: The multi-wave impedance model is used for the simulation of the tower. The tower is divided into three parts: the main body, the bracket and the cross arm, and the wave impedance of each part is calculated separately. The main body includes the vertical main body and the bottom main body. The cross arm is horizontally arranged on both sides of the vertical main body. The number of cross arms in the vertical direction divides the vertical main body into sections;

[0087] Insulator string model: The 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% of the insulator string, the voltage-controlled switch acts to close the switch and short-circuit, simulating the situation of insulator flashover;

[0088] Surge arrester model: The volt-ampere characteristic curve of the surge arrester is simulated and drawn through the volt-ampere characteristic curve parameters of the surge arrester.

[0089] It should be noted that:

[0090] Investigate and count the relevant parameters of transmission lines, towers, insulator strings, surge arresters, etc. According to these parameters, build models of transmission lines, towers, insulator strings, grounding resistors and surge arresters in the ATP-EMTP software to form an overall simulation model of the lightning withstand level of the transmission line for the simulation analysis of the lightning withstand level.

[0091] Transmission line model: In the current lightning protection design of transmission lines, generally two lightning protection lines are installed, forming a three-phase five-wire (three transmission lines) form. When simulating, 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, and the simulation results are relatively close to the actual situation. In this embodiment, the JMarti model is used to simulate the transmission line and the lightning protection line, and the LCC module in the ATP-EMTP software is used for fitting;

[0092] Tower model: The multi-wave impedance model is used in the present invention for the simulation calculation of the tower. This model is established based on the different wave impedances at different heights of the vertical conductor, taking into account the propagation process of waves in the tower, having obvious advantages in lightning strike calculation, and the calculation results are more accurate. Its simulation structure is as Figures 1 - 2 shown, where Figure 1 is the schematic diagram of the tower, Figure 2 is the corresponding multi-wave impedance model diagram.

[0093] Insulator string model: In current industry standards and projects, to determine whether an insulator flashes over, it is mainly by 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% , it is determined as flashover. In this embodiment, the flashover of the insulator is determined by this method, and a voltage-controlled switch is used to simulate the insulator string flashover model.

[0094] Arrester model: In the ATP-EMTP software, a type 92 non-linear resistance element is used for the simulation of the arrester. By inputting the volt-ampere characteristic curve parameters of the arrester, its volt-ampere characteristic curve can be simulated and drawn, as Figure 3 shown.

[0095] To further implement the above technical solution, in the tower model, the wave impedance k of the th vertical main body is calculated as follows:

[0096] ,

[0097] where is the height of the th crossarm, which refers to the height difference between the crossarm part of the tower and the ground;

[0098] ,

[0099] In the formula, is the radius of the th vertical main body; is the horizontal distance between two vertical main bodies; is the radius of the bottom main body; is the horizontal distance between two bottom main bodies; is the equivalent calculation radius of the tower main body;

[0100] The wave impedance of the crossarm part is calculated as follows:

[0101] ,

[0102] In the formula, is the equivalent calculation radius of the th crossarm, and its value is one-fourth of the single crossarm length;

[0103] The wave impedance of the bracket between the th crossarm and the th crossarm is calculated as follows:

[0104] .

[0105] It should be noted that:

[0106] From operation experience, it is known that if the pole tower has a bracket, its wave impedance is 0.9 times that without a bracket. Thus, the equivalent wave impedance of the pole tower bracket part can be obtained. .

[0107] To further implement the above technical solution, in S2, the median value of the lightning current amplitude per 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.

[0108] The specific content of S2 includes:

[0109] For each lightning strike, a separate lightning strike channel is added for independent simulation analysis; according to the median data of the lightning current of each frequency of negative-polarity multiple lightning strikes obtained by statistics, the amplitude ratio of the lightning current of each frequency is calculated.

[0110] It should be noted that:

[0111] In this embodiment, lightning parameters such as the lightning current amplitude, time interval, number of subsequent strokes, and subsequent stroke waveform of multiple lightning strikes in the research 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.

[0112] The subsequent lightning strike waveform refers to the lightning strike waveform after the first lightning strike;

[0113] Multiple lightning current simulation scheme: When the transmission line is struck by lightning, the lightning overvoltage generated on the line will decay rapidly and tend to a steady state after about 1 ms. According to statistical data, the average interval time of multiple lightning strikes is about 140.5 ms, which is significantly longer than the decay time of the lightning overvoltage. Therefore, without considering energy accumulation, a separate lightning strike channel can be added for each lightning strike for independent simulation analysis. According to the median data of the lightning current of each frequency of negative-polarity multiple lightning strikes obtained by statistics, the amplitude ratio of the lightning current of each frequency is calculated for the subsequent analysis of the lightning withstand level of the transmission line under multiple lightning strikes.

[0114] In the ATP-EMTP software, the lightning channel can be equivalent by connecting the built-in lightning current model of the software in parallel with the wave impedance. When the line has a back flashover, the wave impedance of the lightning channel is set to 300 Ω; when the line has a shielding failure, the wave impedance of the lightning channel is set to 800 Ω. The lightning strike waveforms obtained by fitting in the software are as Figure 4 shown.

[0115] The lightning current waveform is simulated by inputting the lightning current amplitude, wavefront, wavelength, and steepness data into the Heidler model.

[0116] To further implement the above technical solution, the specific content of S3 includes:

[0117] Input the lightning current waveform, lightning current amplitude of the th lightning strike, and the lightning withstand level of the line under multiple lightning strikes , gradually change the lightning current amplitude, and by observing the voltage waveforms at both ends of the three-phase insulators of the lightning-struck tower, test the critical lightning current amplitude that causes the insulator to experience lightning flashover, so as to determine the lightning withstand level of the tower under the th lightning strike;

[0118] Based on the proportional relationship of the lightning current amplitude of each lightning strike calculated in S2, reverse-deduce the lightning current amplitude of the first lightning strike according to the lightning withstand level of the tower under the th lightning strike , and compare with the lightning withstand level of the line under multiple lightning strikes to obtain the value of the lightning withstand level of multiple lightning strikes : If is greater than or equal to the lightning withstand level of the line under multiple lightning strikes , then the value of the lightning withstand level of multiple lightning strikes is ; If is less than the lightning withstand level of the line under multiple lightning strikes , then the value of the lightning withstand level of multiple lightning strikes is ;

[0119] where the lightning withstand level is the back-strike lightning withstand level or the shielding failure lightning withstand level .

[0120] It should be noted that:

[0121] Finally, the overall lightning withstand level simulation model of the transmission line is as shown in Figure 5 .

[0122] To further implement the above technical solution, the specific content of S4 includes:

[0123] The total tripping rate of the line under multiple lightning strikes includes the back-strike tripping rate and the shielding failure tripping rate :

[0124] ,

[0125] In the formula, is the number of times the tower is struck by lightning under D lightning days per 100 km of line; is the striking rate of the tower, that is, the ratio of the number of times the tower is struck by lightning to the total number of times the line is struck by lightning; is the arc - building rate, which refers to the probability that an impulse flashover is converted into a stable power - frequency arc; is the probability that the lightning current amplitude exceeds the back - flashover lightning withstand level of the tower ; is the shielding failure rate; is the probability that the lightning current amplitude exceeds the shielding - failure lightning withstand level ;

[0126] It should be noted that:

[0127] In this embodiment, D is taken as 40. The lightning - induced trip rate refers to the number of breaker openings caused by lightning per 100 km of line under 40 lightning days, and it is a comprehensive index to measure the lightning protection performance of the line. The present invention proposes a calculation method for the trip rate of a transmission line under n - fold lightning strikes. The specific flow chart is as Figure 6 shown, where the lightning current amplitude is set to increase by 1 each time on the basis of the original lightning current amplitude.

[0128] From the perspective of the lightning - struck location, the back - flashover includes two parts: one is that the lightning strikes the top of the tower and the shield wire near the tower, and the other is that the lightning strikes the middle of the shield - wire span. Since as long as the air gap meets the requirements of the regulations, the lightning striking the middle of the shield - wire span generally does not cause flashover, it can be considered that the back - flashover trip rate is mainly determined by the first situation.

[0129] The striking rates of different numbers of shield wires and the terrain of the line corridor are different, and their specific values refer to Table 1.

[0130] Table 1 Striking rates of different lines

[0131] .

[0132] In order to further implement the above - mentioned technical solution, the calculation method of

[0133] ,

[0134] In the formula, is the ground flash density; is the number of lightning days; is the average height of the upper conductor; is the distance between shield wires;

[0135] and The calculation methods of

[0136] ,

[0137] Wherein, is or ; is or ;

[0138] The calculation method of

[0139] ,

[0140] Wherein, is the average operating voltage gradient of the insulator string:

[0141] ,

[0142] Wherein, is the system rated voltage, is the length of the insulator string, is the phase distance between cross arms of the pole tower. For the iron cross arm and reinforced concrete cross arm lines, .

[0143] To further implement the above solution, it further includes: S5. Using the lightGBM algorithm to construct a probability distribution model of multiple lightning strike multiplicities, and obtaining the weighted tripping rate of the transmission line including different lightning strike multiplicities. The specific method is:

[0144] (1) Data collection: Obtaining the lightning strike data of historical lightning events and their corresponding meteorological data as a data set;

[0145] (2) Data preprocessing: After interpolating and cleaning the data set using the K-nearest neighbor interpolation method, normalizing both the lightning strike data and the meteorological data;

[0146] (3) Model training: Dividing the preprocessed data set into a training set, a test set, and a validation set, optimizing the LightGBM model through training parameter tuning and cross-validation methods, and testing and evaluating the optimized LightGBM model through the sample set to obtain the final LightGBM model;

[0147] (4) Lightning strike multiplicity probability distribution prediction: Using the final LightGBM model, inputting the lightning strike data and meteorological data within any historical time period, and outputting the probability distribution of the lightning strike multiplicity:

[0148] ,

[0149] Wherein, is Probability distribution of heavy lightning strikes;

[0150] (5) For the tripping rate of high-multiplicity lightning strikes, that is when it is greater than or equal to 3, introduce a probability correction module based on the attention mechanism, and the corrected probability is:

[0151] ,

[0152] where is an empirical parameter;

[0153] Replace the probability in that is greater than or equal to 3 with the corrected probability to obtain the replaced probability distribution ; ;

[0154] (6) Dynamic update mechanism: When new lightning strike data is added, update the model parameters by incremental training to maintain prediction real-time; combine real-time meteorological warning data, and dynamically adjust the model parameters through online learning to ensure that the probability distribution of lightning strike multiplicities changes dynamically with the weather, ensuring that the calculation results are more in line with the actual situation; and retrain the model every preset time period to avoid concept drift;

[0155] (7) Weighted tripping rate calculation framework: Use the replaced probability distribution as the weight, and perform weighted summation on the total tripping rate of the line under heavy lightning strikes to obtain the weighted tripping rate of the transmission line:

[0156] .

[0157] It should be noted that:

[0158] The flow chart for constructing the final LightGBM model is as Figure 7 shown;

[0159] In this embodiment, lightning strike data (lightning strike multiplicity, lightning strike intensity, lightning strike location, etc.) and meteorological data (temperature, humidity, wind speed, air pressure) of historical lightning events are obtained from a lightning location network, meteorological satellites, etc.

[0160] After interpolating and cleaning the dataset using the K-nearest neighbor interpolation method, both the lightning strike data and meteorological feature variables are normalized to eliminate clutter data and improve data accuracy.

[0161] During the model training process, the dataset is divided into a training set, a test set, and a validation set according to a ratio of 7:2:1.

[0162] During the process of predicting the probability distribution of lightning strike multiplicity and the dynamic update mechanism, the specific duration of any historical time period and preset time period can be selected according to the actual situation, such as one month.

[0163] For the tripping rate of high multiplicity lightning strikes (such as more than 3 times), a probability correction module based on the attention mechanism is introduced, and its weight is amplified through an exponential function to reflect the effect of multiple lightning strikes on the cumulative damage of insulators.

[0164] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate 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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