A method and device for analyzing lightning stroke faults of a power transmission line

Abstract

The application provides a power transmission line lightning stroke fault analysis method and device, relates to the technical field of fault analysis, and comprises the following steps: in response to the triggering of a line trip signal, performing spatial correlation screening on a lightning stroke event set in a first time window based on a fault distance interval of the line, obtaining a candidate lightning stroke subset, sorting each lightning stroke event in the candidate lightning stroke subset, and mapping each lightning stroke event to the nearest tower on the line corridor to obtain a time sequence lightning stroke queue and a target tower set; constructing a multi-lightning stroke time sequence simulation model of the target tower based on the account parameters of the target tower; superimposing and simulating the lightning current parameters of each lightning stroke event in the order of the time sequence lightning stroke queue to obtain an insulation damage coefficient, and then determining whether the target tower flashes over and determining the fault cause in combination with the superimposed simulation result. The application can reflect the cumulative process of insulation damage in simulation, thereby accurately determining the key lightning stroke triggering the flashover and the fault cause in the multi-lightning stroke superposition scene.

Description

Technical Field

[0001] This application relates to the field of fault analysis technology, and in particular to a method and apparatus for analyzing lightning strike faults in power transmission lines. Background Technology

[0002] Transmission lines are susceptible to lightning strikes during operation. When a lightning strike causes a line to trip, it is necessary to analyze the cause of the fault to determine whether it was a backflash or a side flash, thus providing a basis for subsequent maintenance and lightning protection upgrades. Lightning fault analysis typically requires combining lightning strike data recorded by lightning location devices with line parameters to determine the correlation between the lightning strikes during the tripping period and the faulty line.

[0003] Current analytical methods typically rely on a single lightning strike occurring within a time window prior to or after the tripping event, close to the line. This is combined with a comparison of the lightning current amplitude of that strike with the tower's insulation level to determine whether flashover occurred and its cause. However, in actual thunderstorms, multiple lightning strikes may occur simultaneously on the same tower or adjacent sections. While the overvoltage from the preceding strike may not directly cause insulator flashover, it can damage the insulation to some extent, reducing its ability to withstand subsequent lightning overvoltages. In such cases, simply comparing the lightning current amplitude of a single strike with the initial insulation level fails to reflect the cumulative changes in insulation under the combined effects of multiple lightning strikes, making it difficult to determine the critical lightning strike event that ultimately triggered the flashover and its cause.

[0004] Therefore, accurately determining the key lightning strike and the cause of the fault when multiple lightning strikes occur successively on the same line section has become a problem that needs to be solved. Summary of the Invention

[0005] This application provides a method and apparatus for analyzing lightning strike faults in transmission lines, in order to solve the problem of how to accurately determine the key lightning strikes that trigger flashovers and the causes of faults by simulating the temporal superposition of the effects of multiple lightning strikes on the same line section.

[0006] The first aspect of this application provides a method for analyzing lightning strike faults in transmission lines, comprising: In response to the triggering of the line trip signal, the set of lightning strike events within the first time window is spatially correlated and filtered based on the fault distance interval of the line to obtain a candidate lightning strike subset; The lightning strike events in the candidate lightning strike subset are sorted and each lightning strike event is mapped to the nearest tower on the line corridor to obtain the time-series lightning strike queue and the target tower set; Based on the ledger parameters of the target towers in the target tower set, a multi-lightning strike time-series simulation model of the target towers is constructed. The lightning current parameters of each lightning strike event are sequentially injected into the multi-lightning strike time-series simulation model according to the order of the time-series lightning strike queue for superposition simulation to obtain the insulation damage coefficient. Based on the insulation damage coefficient and the results of the superimposed simulation, it is determined whether the target tower has experienced flashover and the cause of the fault is identified.

[0007] Optionally, in one possible implementation of the first aspect, the set of lightning strike events within the first time window is spatially correlated and filtered based on the fault distance interval of the line to obtain a candidate lightning strike subset, including: The arrival time of the traveling wave when a line fault occurs is obtained from the traveling wave ranging device, and the fault distance is calculated. Based on the fault distance, the fault section is marked on the line geographic information map, and the length of the fault section covers the measurement error range of the fault distance; Calculate the geographical coordinates of each lightning strike event in the lightning strike event set within the first time window before and after the line trip signal triggering time, and the straight-line distance between each base tower in the fault section; Lightning strike events with a straight-line distance less than a preset distance threshold are retained, while lightning strike events with a straight-line distance greater than or equal to the preset distance threshold are removed. The retained lightning strike events are then used to form the candidate lightning strike subset.

[0008] Optionally, in one possible implementation of the first aspect, the step of sorting the lightning strike events in the candidate lightning strike subset and mapping each lightning strike event to the nearest tower on the line corridor to obtain a time-series lightning strike queue and a target tower set includes: The lightning strike events in the candidate lightning strike subset are sorted according to the order of their occurrence, and the sorted sequence is used as the time-series lightning strike queue. Determine the distance between the geographical coordinates of each lightning strike event in the time-series lightning strike queue and the base coordinates of each tower on the line corridor, and determine the tower with the smallest distance as the mapping tower of the corresponding lightning strike event; The towers to which all lightning strike events are mapped are counted. Towers that appear more than a preset mapping frequency threshold, as well as towers located within the fault distance range, are collectively included as elements in the target tower set.

[0009] Optionally, in one possible implementation of the first aspect, constructing a multi-lightning-strike time-series simulation model of the target towers based on the ledger parameters of the target towers in the target tower set includes: Retrieve the structural parameters, insulator configuration parameters, and grounding resistance parameters of the target towers from the target tower set from the production management device; In the electromagnetic transient simulation platform, an electrical geometric model of the target tower is built based on the structural parameters, insulator configuration parameters, and grounding resistance parameters. Multiple excitation source interfaces are set in the electrical geometry model. The number of excitation source interfaces is consistent with the number of lightning strike events in the time-series lightning strike queue, and each excitation source interface corresponds to one lightning strike event. State parameter variables are set at the insulator string positions in the electrical geometry model; the state parameter variables are used to characterize the dynamic changes in insulation state, and the initial values ​​of the state parameter variables correspond to the reference insulation level of the insulator configuration parameters.

[0010] Optionally, in one possible implementation of the first aspect, the step of sequentially injecting the lightning current parameters of each lightning strike event into the multi-lightning strike time-series simulation model according to the order of the time-series lightning strike queue for superposition simulation to obtain the insulation damage coefficient includes: Select a lightning strike event sequentially from the time-series lightning strike queue as the current simulation event; The amplitude and polarity of the lightning current in the current simulation event are converted into a lightning current waveform signal. At the time of occurrence of the current simulation event, the lightning current waveform signal is injected into the electrical geometry model through the corresponding excitation source interface. Run the simulation platform to calculate the overvoltage values ​​at both ends of the insulator string of the target tower after this injection; Determine whether the overvoltage value is higher than the product of the current value of the state parameter variable and the preset safety margin. If yes, determine that a flashover has occurred and end the simulation. If no, calculate the insulation damage increment caused by the lightning strike based on the magnitude and duration of the overvoltage value and update the state parameter variable. Repeat the above steps until all lightning events in the time-series lightning strike queue have been injected and simulated, or until a flashover is determined to have occurred during the simulation. The insulation damage coefficient is obtained based on the percentage decrease of the final value of the state parameter variable relative to its initial value.

[0011] Optionally, in one possible implementation of the first aspect, determining whether the target tower has experienced flashover and identifying the cause of the fault based on the insulation damage coefficient and the results of the superimposed simulation includes: If the simulation process determines that a flashover has occurred before all lightning strike events have been injected, then the output will show that the fault has been diagnosed. If the simulation process fails to determine that a flashover has occurred after all lightning events have been injected, the overvoltage value obtained from the last simulation is compared with the final value of the state parameter variable. If the overvoltage value is higher than the final value of the state parameter variable, the result of fault diagnosis is output; otherwise, the result of fault diagnosis is output. For cases where the fault has been diagnosed, the simulation process records are traced back to identify the lightning strike event that caused the overvoltage value to exceed the current value of the state parameter variable as the key triggering lightning strike. Analyze the first flow path of the lightning current that triggered the key lightning strike in the electrical geometric model. If the first flow path is through the lightning conductor to the tower and then to the insulator string, the fault is determined to be caused by backflashover. If the first flow path is a direct strike to the conductor through the insulator string, the fault is determined to be caused by backflashover.

[0012] Optionally, in one possible implementation of the first aspect, the method further includes: Before constructing the multi-lightning-strike time-series simulation model of the target tower, obtain the ledger update record of the target tower; When there is a record of updated ledger entries and the update time is later than the preset ledger freeze time, a parameter review prompt will be issued. The actual parameters of the target tower, confirmed by manual review, are received and used to replace the ledger parameters in order to construct the multi-lightning strike time-series simulation model.

[0013] Optionally, in one possible implementation of the first aspect, the method further includes: When the fault is caused by a counterattack and the insulation damage coefficient is higher than the preset high-loss threshold, a full-line lightning protection performance review of the line section where the target tower is located is triggered. The review of the lightning protection performance of the entire line includes: obtaining the ledger parameters of all towers in the line section and the record of the most recent lightning trip; For each tower, a multi-lightning strike time-series simulation model was re-executed, along with subsequent simulation and judgment steps, to identify potentially high-risk towers. Preventive modification recommendations are generated for the identified potentially high-risk towers.

[0014] Optionally, in one possible implementation of the first aspect, the method further includes: When the number of lightning strike events in the candidate lightning strike subset is greater than a preset event threshold, and the duration between the occurrence time of the first lightning strike event and the occurrence time of the last lightning strike event in the time-series lightning strike queue is less than a preset superposition duration, the current scenario is determined to be a multi-lightning strike superposition scenario. A deep analysis command is triggered for the multiple lightning strike scenarios, which instructs the generation of a weighted table of the contribution of each lightning strike event to insulation damage.

[0015] A second aspect of this application provides a transmission line lightning strike fault analysis device, comprising: The filtering module is used to respond to the triggering of the line trip signal, and to perform spatial correlation filtering on the set of lightning strike events within the first time window based on the fault distance interval of the line to obtain a candidate lightning strike subset; The mapping module is used to sort the lightning strike events in the candidate lightning strike subset and map each lightning strike event to the nearest tower on the line corridor to obtain the time-series lightning strike queue and the target tower set. The construction module is used to construct a multi-lightning strike time-series simulation model of the target towers based on the ledger parameters of the target towers in the target tower set; The simulation module is used to inject the lightning current parameters of each lightning strike event into the multi-lightning strike time-series simulation model in the order of the time-series lightning strike queue for superposition simulation to obtain the insulation damage coefficient. The determination module, based on the insulation damage coefficient and the results of the superimposed simulation, determines whether the target tower has experienced flashover and identifies the cause of the fault.

[0016] The beneficial effects of the transmission line lightning strike fault analysis method and device provided in this application are as follows: This application constructs a multi-lightning-strike time-series simulation model by sorting candidate lightning strike events within the tripping period according to their occurrence time and mapping them to corresponding towers. This model includes multiple excitation source interfaces and insulation state parameter variables. The lightning current parameters of each lightning strike event are injected into the model sequentially for superimposed simulation. The insulation state parameter variables are updated after each injection, allowing the damage to the insulator under preceding lightning strikes to be continuously accumulated and reflected during the simulation. Compared to a static comparison of a single lightning strike event with the initial insulation level, this application can dynamically track the changes in insulation state under the superimposed effects of multiple lightning strikes during the simulation. It can then determine the moment when the overvoltage exceeds the current insulation state parameters, identify the key triggering lightning strike that ultimately causes the insulator to flashover, and distinguish between backflashover and side-flashover fault causes by analyzing the flow path of this lightning strike in the electrical geometry model. This allows for a verifiable and quantitative determination of the fault causes in multi-lightning-strike scenarios. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating a method for analyzing lightning strike faults in transmission lines provided in an embodiment of this application. Figure 2 This is an application scenario diagram of a method for analyzing lightning strike faults in power transmission lines provided in an embodiment of this application; Figure 3 This is a schematic diagram of the structure of a power transmission line lightning strike fault analysis device provided in an embodiment of this application; Figure 4 This is a schematic diagram of the hardware structure of an electronic device provided in an embodiment of this application. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0019] The technical solutions of this application will be described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0020] See Figure 1 This is a flowchart of a method for analyzing lightning strike faults in transmission lines provided in an embodiment of this application. Figure 1 The execution entity of the method shown can be a software and / or hardware device. The execution entity of this application can include, but is not limited to, at least one of the following: user equipment, network equipment, etc. User equipment can include, but is not limited to, computers, smartphones, personal digital assistants (PDAs), and the aforementioned electronic devices. Network equipment can include, but is not limited to, a single network server, a server group consisting of multiple network servers, or a cloud based on cloud computing consisting of a large number of computers or network servers. Cloud computing is a type of distributed computing, consisting of a super virtual computer composed of a group of loosely coupled computers. This embodiment does not impose any limitations on this.

[0021] like Figure 2 The diagram shown illustrates the application scenario of this application. When a substation or monitoring terminal detects a line trip signal, it filters lightning strike events near the line corridor based on the fault distance range and the first time window to obtain a candidate lightning strike subset. The candidate lightning strike events correspond to different tower locations on the line, providing basic data for subsequent time-series lightning strike event sorting, tower mapping, and multi-lightning strike time-series simulation.

[0022] This application provides a method for analyzing lightning strike faults in power transmission lines, comprising steps S1 to S5.

[0023] Step S1: In response to the triggering of the line trip signal, the set of lightning strike events within the first time window is spatially correlated and filtered based on the fault distance interval of the line to obtain a candidate lightning strike subset.

[0024] In some embodiments, prior to step S1, this application embodiment further includes obtaining a set of lightning strike events within a first time window before and after the line trip signal triggering time, as well as the line fault distance range and tower ledger parameters, including steps A1 to A3: Step A1: In response to the trip signal issued by the line protection device, take the trigger time of the trip signal as the reference point and determine the time interval including the trigger time as the first time window. Step A2: Send a query request containing the first time window to the lightning location device; Step A3: Receive all lightning strike events recorded within the first time window from the lightning location device in response to the query request, and combine all lightning strike events into a lightning strike event set.

[0025] Each lightning strike event includes the time of occurrence, geographical coordinates, lightning current amplitude, and polarity.

[0026] It should be noted that the lightning strike that triggers a line trip does not necessarily coincide completely with the moment the line protection device issues a trip signal. After a lightning strike, the lightning current forms a discharge channel through the insulator string, and the protection device detects the fault current before initiating the trip. This entire process involves a time delay of several milliseconds. In scenarios with multiple lightning strikes, preceding lightning strikes related to the current fault may have occurred several seconds before the tripping moment, already causing varying degrees of cumulative damage to the insulators. Therefore, setting the first time window to include a period of time encompassing the trigger moment, rather than just a very short period near the trigger moment, is to include all relevant preceding lightning strike events in scenarios with multiple lightning strikes in the analysis scope, avoiding the omission of preceding lightning strike records that caused cumulative damage to the insulators due to time truncation.

[0027] The preset duration of the first time window consists of two segments: a forward extension duration and a backward extension duration. The forward extension duration should cover the time period of all preceding lightning strikes that may cause cumulative damage to the insulators during this thunderstorm. The backward extension duration should cover the time deviation that may be caused by the delay in the action of the protection device and the time synchronization error of the lightning location device data. For example, the preset duration is set to an asymmetrical interval of 30 seconds forward and 5 seconds backward. The forward extension duration is set longer because the preceding lightning strikes that cause cumulative damage to the insulators all occur before the trip signal is triggered. The backward extension duration is set shorter only to cover the delay in the action of the protection device and the time synchronization error of the data. Step A3 receives all the lightning strike events returned by step A2 and uses all the lightning strike events returned by step A2 to form a lightning strike event set, which serves as the original input for the spatial correlation filtering in step S1. It is easy to understand that the four types of data fields carried by each lightning strike event have a clear purpose in steps S1 to S4: the occurrence time is used for time sequence sorting in step S2, the geographical coordinates are used for spatial distance calculation in step S1 and tower mapping in step S2, and the lightning current amplitude and polarity are converted into lightning current waveform signals and injected into the simulation model in step S4. Without any one of the four types of data fields, it is impossible to complete the complete multi-lightning strike superposition simulation analysis process.

[0028] In some embodiments, step S1, "spatial correlation filtering of the lightning strike event set within the first time window based on the fault distance interval of the line to obtain a candidate lightning strike subset," includes the following steps: Step S11: Obtain the arrival time of the traveling wave when the line fault occurs and the calculated fault distance from the traveling wave ranging device; Step S12: Mark the fault section on the line geographic information map according to the fault distance. The length of the fault section covers the measurement error range of the fault distance. Step S13: Calculate the geographical coordinates of each lightning strike event in the lightning strike event set and the straight-line distance between each base tower in the fault section.

[0029] Step S14: Retain lightning strike events with a straight-line distance less than a preset distance threshold, and remove lightning strike events with a straight-line distance greater than or equal to the preset distance threshold. The retained lightning strike events are then combined into a candidate lightning strike subset.

[0030] Specifically, the traveling wave ranging device calculates the distance between the fault location and the reference measuring end by recording the time difference between the traveling wave of lightning current propagating along the line to both ends and arriving at each measuring end at the time of the fault. Step S11 records the distance calculated by the traveling wave ranging device as the fault distance. Due to certain errors in the calibration of the traveling wave propagation speed and certain time deviations in the waveform start-up identification, the fault distance itself contains a certain measurement uncertainty, and the actual location of the fault point cannot be accurately located to a specific coordinate point on the line. Therefore, step S12 marks a fault section covering the actual location of the fault point on the line geographic information map, extending half a measurement error range to both sides of the fault distance as the center, thereby ensuring that the actual location of the fault point falls within the fault section with a very high probability. Step S13 extracts the geographic coordinates of each lightning strike event in the lightning strike event set, calculates the straight-line distance between the coordinates of the lightning strike event and the base coordinates of each tower in the fault section, and uses the minimum value among the distance calculation results as a distance index to measure the spatial proximity between the lightning strike event and each tower in the fault section. The method of using the minimum value as the distance index ensures that lightning strikes that land in the middle of the span between two adjacent towers can be screened based on their distance from the tower on the closer side, rather than being incorrectly rejected because the distance between the middle of the span and the towers at both ends is too large.

[0031] The preset distance threshold is a distance threshold used to determine whether a single lightning strike event is spatially close enough to a tower within the faulty section to retain it as a candidate event. A larger value results in more candidate events being retained, but also a higher probability of irrelevant events being mistakenly retained. A smaller value results in stricter filtering, but edge events with weak correlation to the fault may be incorrectly rejected. The preset distance threshold should be matched to the line span and the typical offset range of lightning strike points in bypass scenarios. For example, using 0.6 times the average line span as the preset distance threshold can cover the maximum possible straight-line distance between a lightning strike point in the middle of the span and the nearest tower, since the straight-line distance between the strike point and the nearest tower is no more than half a span. This also filters out irrelevant lightning strike events that are far from the faulty section.

[0032] For example, suppose a line trips at 14:35:22, with the first time window set from 14:34:52 to 14:35:27. The lightning location device returns 52 lightning strike events within this first time window. The traveling wave ranging device gives a fault distance of 47.3 km, with a measurement error of ±0.8 km. The fault section is calibrated as 46.5 km to 48.1 km, encompassing four towers: No. 83, No. 84, No. 85, and No. 86. For each of the 52 lightning strike events, the minimum straight-line distance between the event and the four towers was calculated. After filtering with a preset distance threshold of 300 meters, five lightning strike events with a distance index of less than 300 meters were retained as a candidate lightning strike subset. The remaining 47 lightning strike events were eliminated because the distance to each tower in the fault section exceeded 300 meters. This reduced the input data range for subsequent modeling and simulation from 52 to 5, ensuring the computational efficiency and relevance of the superimposed simulation.

[0033] Step S2: Sort the lightning strike events in the candidate lightning strike subset and map each lightning strike event to the nearest tower on the line corridor to obtain the time-series lightning strike queue and the target tower set.

[0034] In some embodiments, step S2 includes steps S21 to S23: Step S21: Sort the lightning events in the candidate lightning strike subset according to the order of their occurrence time, and use the sorted sequence as the time-series lightning strike queue. Step S22: Determine the distance between the geographical coordinates of each lightning strike event in the time-series lightning strike queue and the tower base coordinates of each tower on the line corridor, and determine the tower with the smallest distance as the mapping tower of the corresponding lightning strike event; Step S23: Count all towers mapped to all lightning strike events, and include towers that have occurred more than the preset mapping number threshold, as well as towers located within the fault distance range, as elements in the target tower set.

[0035] Specifically, in step S21, the occurrence time of each lightning event in the candidate lightning strike subset is used as the sorting key, and the lightning events are arranged from earliest to latest time. The ordered sequence after arrangement is determined as the time-series lightning strike queue. The establishment of the time-series lightning strike queue is not only a data processing operation, but also a fundamental condition for the superposition simulation in step S4 to inject data according to the actual time sequence. In the scenario of multiple lightning strikes, the damage to the insulator is the result of the sequential superposition of each lightning strike in the actual occurrence order. If the sorting is based on other dimensions such as the magnitude of the lightning current instead of the order of occurrence, the update path of the insulation withstand capability during the simulation will deviate from the actual physical process. This will cause the identified lightning strike event that ultimately causes the insulator to flashover to be inconsistent with the actual lightning strike event that triggers the flashover. Therefore, strictly establishing the time-series lightning strike queue according to the order of occurrence is a basic prerequisite for ensuring that the superposition simulation results accurately reflect the actual multi-lightning strike superposition process.

[0036] Step S23 involves statistically analyzing the mapping results of all lightning events in the time-series lightning strike queue. Both conditions must be met simultaneously; any tower satisfying either condition is included in the target tower set. Using an occurrence count exceeding a preset mapping count threshold as an inclusion condition is to identify towers with concentrated lightning strikes during this thunderstorm. Even if a tower with concentrated lightning strikes is not exactly within the fault distance range calibrated by traveling wave ranging, it may still be associated with this fault due to the cumulative effect of multiple lightning strikes. Using location within the fault distance range as a fallback condition ensures that towers corresponding to potential fault locations indicated by traveling wave ranging results are always included in the target set, preventing them from being missed because the mapping count of a tower within the fault distance range just happens not to exceed the preset mapping count threshold.

[0037] The preset mapping threshold is a threshold number of mappings used to determine whether a certain tower has a high probability of being associated with a fault due to a concentration of lightning strikes. It can be set in different tiers based on the total number of lightning strike events in the candidate lightning strike subset. For example, when there are 5 or more lightning strike events in the candidate lightning strike subset, the preset mapping threshold can be set to 2 times, meaning that only towers mapped to 2 or more lightning strike events are considered as towers in the lightning strike concentration and included in the target set. When there are only 1 to 2 lightning strike events in the candidate lightning strike subset, the preset mapping threshold can be set to 1 time, ensuring that no tower mapped is missed.

[0038] For example, following the example of step S14, there are 5 lightning strike events in the candidate lightning strike subset, which are numbered E1, E2, E3, E4, and E5 in order of occurrence from earliest to latest. Step S21 arranges the 5 lightning strike events into a time-series lightning strike queue [E1, E2, E3, E4, E5]. Step S22 maps each lightning strike event to a tower: E1 is mapped to tower 84, E2 to tower 84, E3 to tower 85, E4 to tower 84, and E5 to tower 83. Step S23 counts the number of mappings: tower 84 is mapped 3 times, which meets the condition that the number of occurrences exceeds the preset mapping threshold of 2 times; towers 83, 84, 85, and 86 are all located within the fault distance range of 46.5 km to 48.1 km, which meets the fallback condition. Therefore, the elements of the target tower set are towers No. 83, 84, 85 and 86. Tower No. 84 satisfies two conditions at the same time and is the tower with the most concentrated lightning strikes in this multiple lightning strike event.

[0039] Step S3: Based on the ledger parameters of the target towers in the target tower set, construct a multi-lightning strike time-series simulation model for the target towers.

[0040] In some embodiments, prior to step S3, this application further includes steps B1 to B3: Step B1: Before constructing the multi-lightning-strike time-series simulation model of the target tower, obtain the record update of the target tower's ledger; Step B2: When there is an updated ledger record and the update time is later than the preset ledger freeze time, issue a parameter review prompt; Step B3: Receive the actual parameters of the target tower after manual verification, and use the actual parameters to replace the ledger parameters to construct a multi-lightning strike time-series simulation model.

[0041] If a power tower undergoes changes such as grounding resistance modification or insulator replacement after the recorded time point in the data log, but the data log parameters have not been updated accordingly, building a simulation model using these outdated parameters will result in discrepancies between the insulation level or grounding resistance values ​​in the model and the actual state of the tower, thus distorting the simulation results. Therefore, verifying the data log update records before building a multi-lightning-strike time-series simulation model, and issuing parameter review prompts when recent changes that may affect the simulation results are found, followed by on-site manual verification and confirmation to replace the data log parameters with actual parameters, is a necessary prerequisite to ensure that the multi-lightning-strike time-series simulation model is consistent with the actual state of the tower. The preset data log freeze time is the time point for determining whether a review is needed after updating the data log parameters. This can be a time point determined by counting forward 30 days from the time of the fault occurrence, or a time point determined by the start date of the current lightning season.

[0042] In some embodiments, step S3 includes steps S31 to S34: Step S31: Retrieve the structural parameters, insulator configuration parameters, and grounding resistance parameters of the target towers from the target tower set in the production management device; Step S32: In the electromagnetic transient simulation platform, build the electrical geometric model of the target tower based on structural parameters, insulator configuration parameters, and grounding resistance parameters; Step S33: Set up multiple excitation source interfaces in the electrical geometry model. The number of excitation source interfaces is consistent with the number of lightning strike events mapped to the currently modeled tower in the time-series lightning strike queue. Each excitation source interface corresponds to one lightning strike event. Step S34: Set state parameter variables at the insulator string positions in the electrical geometry model. The state parameter variables are used to record the gradual changes in the insulator string's withstand capacity after each lightning strike injection. The initial value of the state parameter variables corresponds to the rated lightning impulse withstand voltage of the insulator configuration parameters.

[0043] Specifically, step S31 retrieves three types of ledger parameters for the target tower from the production management device. Structural parameters should include the tower type number, total tower height, height of each crossarm above the ground, height of the conductor suspension point above the ground, height of the lightning protection wire suspension point above the ground, horizontal distance between conductor phases, and the equivalent radius of the tower body cross-section within the height range of each tower segment. These fields collectively determine the spatial positional relationship of each segment of the tower body and the mounting position of each conductor in the electrical geometric model. Insulator configuration parameters should include the insulator string model, the standard value of the 50% impulse flashover voltage of a single insulator piece, the number of insulator pieces in the string, and the corresponding rated lightning impulse withstand voltage. The rated lightning impulse withstand voltage field is the direct source for setting the initial values ​​of the state parameter variables in step S34. Grounding resistance parameters should include the measured value of the power frequency grounding resistance at the base of the target tower. If the actual parameters have been confirmed in step B3, the confirmed values ​​from step B3 will replace the original ledger values.

[0044] Step S32 involves building the electrical geometric model of the target tower in the simulation platform based on the ledger parameters retrieved in step S31. The ground clearance values ​​of each crossarm are sequentially read from the structural parameters in step S31, arranged in ascending order. A zero value representing the ground clearance is added at the beginning of the arrangement, and the ground clearance value of the lightning protection wire suspension point is added at the end, forming a complete height node sequence. The segment between each pair of adjacent values ​​in the height node sequence is marked as a tower segment. For each tower segment, the equivalent radius of the tower cross-section and the height difference between the segments are read. A two-port conductive element is created for each tower segment in the simulation platform and connected in series to form a connecting path from the ground node to the top node. Crossarm extension elements are established on both sides at the height of the crossarm. Conductor extension elements with span lengths are established on both sides at each conductor and lightning protection wire suspension point. Each conductor extension element is connected to a terminal resistor element at the far end with a value equal to the standard value of the corresponding conductor wave impedance. An insulator string monitoring element is established between the crossarm end node and the conductor node corresponding to each conductor phase. A grounding resistance element corresponding to the measured value of the power frequency grounding resistance is established and connected to the ground node and the reference ground node. After the connectivity verification is completed, the electrical geometric model of the target tower is built. Candidate access positions for excitation source interfaces are reserved at each lightning protection wire suspension node and conductor suspension node.

[0045] The electrical geometry model completed in step S32 only has the ability to receive a single lightning strike injection and output the corresponding overvoltage calculation result. It does not yet have the ability to retain the insulation withstand capability change information between multiple injections or to correlate the calculation results of each injection. Steps S33 and S34 are based on the electrical geometry model. By setting multiple excitation source interfaces and state parameter variables, the electrical geometry model is transformed into a multi-lightning strike time-series simulation model that can support multiple lightning strikes injected sequentially in time, and whose insulation withstand capability is continuously updated with each injection. This is the core setting that distinguishes the multi-lightning strike time-series simulation model of this application from the conventional single-lightning strike simulation model. The two work together, and the absence of either one will prevent the realization of the complete multi-lightning strike superposition simulation function.

[0046] In step S33, multiple excitation source interfaces are set in the electrical geometry model. The number of excitation source interfaces is consistent with the number of lightning strike events mapped to the currently modeled tower in the time-series lightning strike queue. Each excitation source interface corresponds to one lightning strike event. In step S4, the lightning current signal of each lightning strike event will be injected into the electrical geometry model through the corresponding excitation source interface at the actual occurrence time of the lightning strike event. The other excitation source interfaces do not inject any current or voltage signals into the model during the injection period. Conventional single-strike simulation models typically only have one excitation source interface. There is no transfer and accumulation of insulation withstand capability between independent simulations. If multiple lightning strike events are calculated separately by building independent single-strike simulation models one by one, each calculation starts from the initial insulation level and cannot reflect the actual physical state where the insulator's withstand capability has decreased after the previous lightning strikes have damaged it. By setting multiple excitation source interfaces in the same electrical geometry model, each lightning strike event can be injected sequentially within the same model. The updated state parameter variables between each injection are continuously retained within the model. The simulation calculation of subsequent lightning strike events is based on the insulation withstand capability after the current accumulated damage, rather than on the initial insulation level. This allows the simulation process to accurately reflect the physical process of continuous degradation of insulation withstand capability under the superposition of multiple lightning strikes.

[0047] The excitation source interface can be a current source interface, a voltage source interface, or a controlled source interface. When using a current source interface, a controlled current source is configured for each excitation source interface. Each controlled current source is in a zero-output state at the start of the simulation. When the simulation reaches the occurrence time of a lightning strike event, the controlled current source corresponding to that lightning strike event is activated, causing it to output a waveform current according to the amplitude and polarity of the lightning current in the lightning strike event. After the effective waveform period ends, the output of the controlled current source is restored to zero. At any given time, only the controlled current source corresponding to the lightning strike event at the current moment is in an active output state; the outputs of other controlled current sources remain zero and do not inject current into the model, thus ensuring that the model is not disturbed by irrelevant excitations between injection periods. The access node locations for each excitation source interface can be set in two groups, one at the lightning rod suspension node and one at the conductor suspension node, or uniformly at the tower top node. Alternatively, two sets of candidate access nodes can be preset simultaneously, and the activation of which group is determined before step S4 based on the nature of the lightning strike's impact point. When setting up one set each for the lightning protection wire suspension node and the conductor suspension node, the lightning protection angle of the target tower needs to be calculated from the structural parameters retrieved in step S31 before starting step S4. Then, the critical lightning current value corresponding to the shield failure of the lightning protection angle is retrieved from the line lightning protection design code. The lightning current amplitude of each lightning strike event is compared with the critical lightning current value of shield failure. Lightning strike events with amplitudes exceeding the critical lightning current value of shield failure are judged as backflashover scenarios and the excitation source interface corresponding to the lightning protection wire suspension node is activated. Lightning strike events with amplitudes not exceeding the critical lightning current value of shield failure are judged as backflashover scenarios and the excitation source interface corresponding to the conductor suspension node is activated.

[0048] Step S34 sets state parameter variables at the corresponding nodes of the insulator string monitoring elements in the electrical geometry model. The initial value of the state parameter variables corresponds to the rated lightning impulse withstand voltage in the insulator configuration parameters of step S31, which is the upper limit of the peak overvoltage that the insulator string can withstand without any lightning strike damage. In existing single-strike simulations, the rated lightning impulse withstand voltage is typically used as a fixed threshold. The peak overvoltage at both ends of the insulator string after a single lightning strike is compared with this fixed threshold. This fixed threshold remains unchanged throughout the simulation and is not adjusted based on the effects of preceding lightning strikes. However, in scenarios involving multiple lightning strikes, although preceding strikes may not directly trigger flashover, they have already caused some cumulative damage to the insulator, causing the actual peak overvoltage that the insulator can withstand to decrease compared to the initial rated value. If the overvoltage of each lightning strike is still judged using a fixed initial rated value, the actual state of the reduced withstand capability of the insulator cannot be reflected. Therefore, this application sets state parameter variables at the corresponding nodes of the insulator string monitoring element. Starting from the initial rated lightning impulse withstand voltage, the value of the state parameter variable is updated according to the damage caused to the insulator by each lightning injection after the injection. The updated value of the state parameter variable at that time is used as the basis for the flashover determination in step S44. This changes the existing method of performing a one-time static comparison with a fixed initial rated value to a method of comparing the state parameter variable at that time with the cumulative damage. This allows the gradual deterioration of the insulator's withstand capability under multiple lightning strike scenarios to be continuously quantified in the simulation.

[0049] The initial values ​​of the state parameter variables can be taken directly from the rated lightning impulse withstand voltage field in the ledger parameters, or estimated values ​​calculated by looking up tables in the insulation coordination standard regulations based on the insulator type and the number of insulator discs, or estimated values ​​obtained by converting measured values ​​obtained from withstand voltage tests on insulator strings to the service life. When taking values ​​directly from the ledger parameters, the value of the rated lightning impulse withstand voltage field is read from the insulator configuration parameter record retrieved in step S31, and the value is directly used as the initial value of the state parameter variable. This method is suitable for situations where the ledger parameter record is complete and the rated lightning impulse withstand voltage field has been verified in step B3.

[0050] When the target tower set contains multiple towers, step S3 independently executes the complete modeling process from step S31 to step S34 for each tower, constructing an independent multi-lightning strike time-series simulation model for each target tower. Each tower simulation model only contains the excitation source interface corresponding to the lightning strike event mapped to the currently modeled tower, ensuring that the simulation results of each tower accurately reflect its actual electrical parameters and lightning strike correlation.

[0051] For example, following the example in step S2, take tower No. 84 as an example. Step B1 retrieves the log update records of tower No. 84 and finds that there is an update operation record for the grounding resistance parameter field 18 days before the fault occurred. The update time is later than the preset log freeze time determined by extrapolating 30 days backward from the time of the fault. Step B2 issues a review prompt for the grounding resistance parameter field. After on-site verification by the maintenance personnel, it is confirmed that the actual measured value of the grounding resistance has been updated from 15 ohms in the original log record to 8 ohms after the modification. Step B3 replaces the original recorded value with 8 ohms as the actual grounding resistance parameter. Step S31 retrieves the parameters from the tower record for No. 84: Structural parameters record a tower height of 52 meters, a first crossarm height of 32 meters, a second crossarm height of 42 meters, and a lightning conductor suspension point height of 51 meters. The equivalent radii of the first to third sections of the tower body are 0.8 meters, 0.5 meters, and 0.3 meters, respectively. Insulator configuration parameters record the model as XP-70, the number of insulators as 14, and the rated lightning impulse withstand voltage as 900 kV. The grounding resistance parameter is the value confirmed in step B3: 8 ohms. Step S32 constructs the electrical geometry model of tower No. 84. Step S33 sets three excitation source interfaces corresponding to E1, E2, and E4 in the electrical geometry model. If the lightning current amplitude of E1 and E2 exceeds the critical lightning current value for shield failure, it is determined to be a backflashover scenario. In step S4, the excitation source interface corresponding to the lightning conductor suspension node will be activated. If the lightning current amplitude of E4 does not exceed the critical lightning current value for shield failure, it is determined to be a backflashover scenario. In step S4, the excitation source interface corresponding to the conductor suspension node will be activated. Step S34 sets the voltage-type state parameter variable, with an initial value U0 of 900 kV. The initial value will be gradually reduced by the damage increment after each of the three lightning strike events E1, E2, and E4 in step S4, and updated to the upper limit that the insulator string can withstand at that time after each injection.

[0052] Step S4: The lightning current parameters of each lightning strike event are sequentially injected into the multi-lightning strike time-series simulation model according to the order of the time-series lightning strike queue for superposition simulation to obtain the insulation damage coefficient.

[0053] In some embodiments, step S4 includes steps S41 to S46: Step S41: Select a lightning strike event that has not yet been injected from the time-series lightning strike queue as the current simulation event; Step S42: Convert the amplitude and polarity of the lightning current in the current simulation event into a lightning current waveform signal, and inject the lightning current waveform signal into the electrical geometry model through the corresponding excitation source interface at the time of occurrence of the current simulation event; Step S43: Run the simulation platform step by step to record the overvoltage timing sequence of the two ports of the insulator string monitoring element. Extract the overvoltage peak value generated by this injection from the overvoltage timing sequence. Step S44: Use the product of the current value of the state parameter variable and the preset safety margin as the flashover judgment threshold, and determine whether the overvoltage peak value is higher than the flashover judgment threshold; if the overvoltage peak value is higher than the flashover judgment threshold, then determine that a flashover has occurred, record the current simulation event as a flashover judgment event and terminate the loop; if the overvoltage peak value is not higher than the flashover judgment threshold, then retrieve the current insulation damage increment from the type test insulation damage characteristic data table corresponding to the insulator string model, subtract the insulation damage increment from the current value of the state parameter variable, and update the state parameter variable. Step S45: Repeat steps S41 to S44 until all lightning strike events mapped to the current target tower have been injected, or step S44 determines that a flashover has occurred; Step S46: Obtain the insulation damage coefficient by the proportion of the magnitude of the decrease in the state parameter variable from the initial value to the final value relative to the initial value.

[0054] Specifically, at the beginning of each cycle, step S41 maps the lightning event sequence of the current target tower to the time-series lightning strike queue, finds the first lightning strike event that has not yet been marked as completed injection, and identifies it as the current simulation event. The occurrence time, lightning current amplitude, and polarity of the current simulation event are extracted for use in step S42. The time-series lightning strike queue has already been arranged in chronological order in step S21. The current simulation events selected in each cycle of step S41 strictly maintain an increasing time order, ensuring that the time sequence of each injection in the superimposed simulation strictly corresponds to the occurrence sequence of each lightning strike in the actual multiple lightning strike superposition process. This guarantees that the simulation results accurately reflect the actual cumulative state of damage to the insulator caused by previous lightning strikes.

[0055] Step S42: Read the lightning current amplitude I from the current simulation event log. m And polarity identifier, the polarity identifier is positive I m I is denoted as positive when the polarity is negative. m Recorded as negative values. From the appendix of the technical standard corresponding to the standard impulse current waveform selected in this application, obtain the unit amplitude time-current comparison table for the standard specified waveform. The comparison table lists the time points and unit amplitude current values ​​corresponding to each time step, row by row, starting from the injection start time, with the unit amplitude current value increasing row by row from zero in the first row to a peak value of 1.00, and then decreasing row by row, stopping when the current value is below 0.05. Starting from the first row of the comparison table, each row is compared with I... m The product of the two values ​​is used as the actual current value for the corresponding time step, and these values ​​are recorded sequentially according to the row order of the lookup table to form the waveform current time sequence. The absolute value of the peak time step current and I are then confirmed within the waveform current time sequence. mIf the absolute values ​​are equal, and the two values ​​are not equal due to decimal precision errors, the error is compensated at the time step where the peak value is located, thereby ensuring that the peak value of the injected waveform strictly corresponds to the lightning current amplitude recorded by the lightning location device. Based on the access node type confirmed for the current simulation event in step S33, the waveform current timing sequence is loaded onto the corresponding excitation source interface step by step at the actual occurrence time of the current simulation event. All other excitation source interfaces maintain zero output throughout the entire injection period, ensuring that the injection process of each lightning strike event is independent and does not interfere with each other.

[0056] Step S43: The calculation proceeds step by step according to the simulation step size. After each step is completed, the voltage difference between the two ports of the insulator string monitoring element is read and appended to the overvoltage timing record array indexed by the current simulation event number in the order of the step. This continues until the preset overvoltage recording duration is reached after the injection start time. Then, the item with the largest absolute value is selected from all the values ​​in the overvoltage timing record array and determined as the overvoltage peak value U. k The preset overvoltage recording duration is the length of time that the voltage difference between the two ports of the insulator string monitoring element is continuously recorded after each activation of the excitation source interface. The value should be sufficient to cover the entire process of the lightning current waveform decaying completely from the injected peak to below the preset damage initiation threshold. It is usually set as a reference several times the half-value time specified in the selected standard impulse current waveform technical standard. Step S43 completely saves the overvoltage timing record array for each injection. Step S44 requires retrieving the time steps in the overvoltage timing record array where the overvoltage exceeds the preset damage initiation threshold and calculating the duration. Step S53, which traces back the overvoltage peak value of each injection, also depends on the overvoltage timing record array of each injection. Completely saving the overvoltage timing record array ensures the entire superposition simulation process has complete traceability.

[0057] Step S44 extracts the overvoltage peak value U from step S43. k Then, read the current value V of the state parameter variable. k , with V k The product of the product with the preset safety margin is determined as the flashover determination threshold T for this injection. k Determine U k Is it higher than T? kThe preset safety margin is a reduction ratio applied to the current value of the state parameter variable. It is used to incorporate the overall uncertainty caused by factors such as modeling parameter estimation deviation, traveling wave ranging and positioning deviation, and the numerical calculation accuracy of the simulation platform into the setting of the flashover judgment threshold. This ensures that the final judgment has a certain fault tolerance capability for the uncertainty of the modeling input. The smaller the preset safety margin value, the lower the flashover judgment threshold and the more conservative the judgment. The larger the value, the closer the judgment threshold is to the current value of the state parameter variable and the higher the dependence on the modeling accuracy. The specific value of the preset safety margin is determined by reading from the preset safety margin value reference table after evaluating the overall confidence level of the input for this modeling: the confidence level of the traveling wave ranging is judged by whether the traveling wave ranging device provides double-ended traveling wave data and whether the deviation of the calculation results at both ends is lower than the preset deviation tolerance; the degree of verification of the ledger parameters is judged by whether all ledger parameter fields have been verified on-site in step B3. The preset safety margin value of the corresponding level is retrieved from the preset safety margin value reference table according to the combination of the two dimensions. The combination with the highest confidence level corresponds to the largest preset safety margin value, and the combination with the lowest confidence level corresponds to the smallest preset safety margin value.

[0058] If U k Higher than T k Then, the current simulation event number is recorded as the flashover determination event number, and the first event higher than T is found in the overvoltage timing record array. k The time step is recorded as the flashover determination time, and the loop of step S45 is terminated. Meaningless calculations are promptly stopped after confirming that a flashover has occurred. If U k Not higher than T k Then initiate a table lookup operation: first confirm the preset damage initiation threshold V. d The preset damage initiation threshold is the lower limit of the overvoltage amplitude that causes measurable damage to the insulator. The preset damage initiation threshold V is read from the type test report corresponding to the insulator model. d ;if U k Below V d Therefore, it is assumed that this injection does not produce measurable damage, and the insulation damage increment ΔV k Record it as zero, and the state parameter variable is not updated; if U k Not lower than V d Then, retrieve the voltage difference absolute value higher than V from the overvoltage timing record array hour by hour. d The time step will continuously exceed V d The number of time steps in each time step segment is calculated by converting the simulation step size into a time length and then summing them up to obtain the injected overvoltage exceeding V. d Total duration τ k In the type test insulation damage characteristic data table, U is used as the reference. k The magnitude ratio relative to the initial value U0 of the state parameter variable is the row index, with τ as the index. kLocate the cell at the intersection of the row and column using the column index, and read the value recorded in the cell as the insulation damage increment ΔV. k The state parameter variable V at that time k With insulation damage increment ΔV k The difference is used as the updated state parameter variable value. The updated value is used as the state parameter variable value when calculating the flashover judgment threshold in the next cycle step S44. This allows the decrease in the insulator's ability to withstand the previous lightning strike to be continuously reflected in the flashover judgment in each cycle, realizing the quantitative accumulation of insulation damage in the process of multiple lightning strikes.

[0059] After exiting the loop, step S46 reads the initial value U0 of the state parameter variable from the record set in step S34, and reads the value of the state parameter variable after the last update from the update record of each round in step S44 as the final value V. n U0 and V n The insulation damage coefficient is obtained by taking the ratio of the difference to U0. The insulation damage coefficient is between zero and one. The larger the value, the more severe the cumulative damage to the insulator under the superposition of multiple lightning strikes. The insulation damage coefficient expresses the degree of cumulative damage experienced by the insulator in the scenario of multiple lightning strikes in a single quantitative index, so that the degree of insulation damage between different scenarios can be directly compared, and provides a traceable quantitative basis for the fault cause determination in step S5.

[0060] For example, following the example in step S3, take tower No. 84 as an example. The initial value of the state parameter variable U0 is 900 kV. The traveling wave ranging device provides double-ended traveling wave data and the deviation between the two ends is lower than the preset deviation tolerance. The confidence level of the traveling wave ranging is recorded as high. Step B3 has verified the grounding resistance parameter, but the insulator configuration parameter has not been confirmed on-site. The verification degree of the ledger parameter is recorded as incomplete. The preset safety margin value of the corresponding position is retrieved from the preset safety margin value reference table and recorded as C. m The preset damage initiation threshold V was read from the XP-70 insulator type test report. d Step S41: Select E1 as the current simulation event, with an amplitude of 55 kA, positive polarity, and an occurrence time of 14:34:52. Step S42: Generate the E1 waveform current sequence according to the standard impulse current waveform reference table, confirming that the absolute value of the current at the peak time step is consistent with 55 kA. At 14:34:52, activate the excitation source interface corresponding to E1 at the lightning arrester suspension node, while keeping the other excitation source interfaces at zero output. Step S43: Record the overvoltage sequence hourly until the preset overvoltage recording duration is reached, then extract the overvoltage peak value U1. Step S44: Use 900 kV and C... m The product determines the flashover threshold T1. If U1 is below T1, E1 injection does not trigger a flashover; if the retrieval exceeds V... dThe time-step accumulation is used to calculate τ1. The insulation damage increment ΔV1 is retrieved from the type test insulation damage characteristic data table using the amplitude ratio of U1 relative to 900 kV and τ1 as indexes. The difference between 900 kV and ΔV1 is used as the updated state parameter variable value V1. V1 is less than 900 kV, reflecting that E1 injection has caused measurable damage to the insulator. Step S44 then calculates the next round of flashover judgment threshold based on V1, ensuring that the judgment at the time of E2 injection accurately reflects the actual state of the insulator at that time. Step S41 sequentially selects E2. After E2 injection, the state parameter variable is updated to V2. V2 is lower than V1, and the cumulative damage caused by the superposition of two backflashover lightning strikes is quantified in the continuous updating of the state parameter variable. Step S41 selects E4, amplitude 30 kA, negative polarity, in a bypass scenario, injected through the conductor suspension node excitation source interface. Step S43 extracts the overvoltage peak value U4. Step S44 uses V2 and C... m The product of the values ​​determines the flashover threshold T4. Since V2 has fallen below 900 kV due to the cumulative damage from the two backflashovers E1 and E2, T4 is lower than the initial static threshold determined based on 900 kV, and U4 is higher than T4. Therefore, it is determined that a flashover occurred in the insulator string after E4 injection, and E4 is recorded as a flashover event, terminating the loop. Step S46 uses the ratio of the difference between U0 and V2 to U0 to obtain the insulation damage coefficient. The insulation damage coefficient reflects the cumulative damage caused to the insulator by the two backflashovers E1 and E2, providing quantitative support for the comprehensive determination of the fault cause in step S5. If the existing single-strike static comparison method is used, only the 30 kA lightning current of E4 is compared with the initial insulation level of tower No. 84. The static threshold determined based on the initial rated value of 900 kV remains unchanged. The overvoltage U4 injected by E4 is lower than the static threshold, and the conclusion is that E4 does not trigger a flashover. The cause of this fault cannot be located. This directly demonstrates the essential superiority of this application over the existing technology method of one-time static comparison with a fixed initial insulation level in the case of multiple lightning strikes.

[0061] Step S5: Based on the insulation damage coefficient and the results of superimposed simulation, determine whether the target tower has experienced flashover and identify the cause of the fault.

[0062] In some embodiments, step S5 includes steps S51 to S54: Step S51: If a flashover is determined to have occurred before all lightning strike events mapped to the current target tower are injected in step S44, then the result that the fault has been diagnosed is output. Step S52: If step S45 exits the loop after all lightning strike events mapped to the current target tower have been injected and step S44 has not determined that a flashover has occurred, then the overvoltage peak value in the overvoltage timing record array corresponding to the last injection and the final value V of the state parameter variable are recorded. nDirect comparison shows that the overvoltage peak value is higher than V. n The output fault has been confirmed, and the overvoltage peak value is no higher than V. n Output the result of an undiagnosed fault. Step S53: For the target tower with the confirmed fault output, retrieve the current value of the state parameter variable, the preset safety margin, and the overvoltage peak value of each lightning strike event mapped to the current target tower in the corresponding round in step S44, identify the lightning strike event where the overvoltage peak value first exceeds the product of the current value of the state parameter variable and the preset safety margin, and determine it as a critical triggering lightning strike. Step S54: From the current timing sequence of each branch in the simulation round corresponding to the critical triggering lightning strike, determine the branch path with the highest current flow ratio as the first flow path of the critical triggering lightning strike by taking the proportion of the cumulative amount of the absolute value of the current of each branch from the injection start time to the flashover determination time to the sum of the cumulative amounts of all branches. Based on the first flow path, determine whether the fault is caused by backflash or bypass.

[0063] Specifically, step S51 corresponds to the situation in step S44 where flashover is determined midway through the lightning strike event sequence mapped to the current target tower when there are still lightning strike events that have not been injected. In this case, the superimposed simulation has already met the flashover determination condition in a certain injection, and the result of fault diagnosis is directly output. Step S52 corresponds to the situation where the loop exits after all lightning strike events have been injected normally and flashover has not been triggered in each of the subsequent determinations in step S44. In step S44, the flashover determination threshold is the product of the current value of the state parameter variable and the preset safety margin. The reduction of the preset safety margin makes the flashover determination threshold lower than the current value of the state parameter variable. The overvoltage peak value of the last injection has exceeded the final value V of the state parameter variable. n However, because the flashover detection threshold is reduced by a preset safety margin and is lower than V... n If the result was not identified in step S44, step S52 will perform a supplementary determination on the last injection result, comparing the overvoltage peak value with V. n By directly comparing without introducing a preset safety margin, the boundary situation where the overvoltage just exceeds the actual upper limit of the insulator but does not exceed the reduction threshold is supplemented, so that the successive determination in step S44 and the supplementary determination in step S52 together constitute a complete flashover determination coverage.

[0064] When the output of the fault diagnosis result is not confirmed, check the simulation judgment results of other target towers in the target tower set. If there are other target towers that have output the fault diagnosis result, then continue to execute steps S53 and S54 with the diagnosed target towers as the objects. If all target towers in the target tower set output the fault diagnosis result, then note in the diagnosis report that the cause of the fault has not yet been located by the superimposed simulation, and add a note suggesting that the preset duration of the first time window in step S1 be extended forward appropriately, or the preset distance threshold in step S14 be appropriately increased before re-executing the complete analysis process.

[0065] Step S53 performs key-triggered lightning strike identification on the target tower with the confirmed fault output, starting from the first lightning strike event in the time-series lightning strike queue mapped to the current target tower and tracing back sequentially: from the operation data recorded in step S44 during the corresponding round, read the value V of the state parameter variable at the beginning of this round of the cycle. k and preset safety margin, in V k The product of the current and the preset safety margin determines the flashover detection threshold T for this round. k From the overvoltage timing record array indexed by the corresponding lightning strike event number saved in step S43, retrieve the overvoltage peak value U. k ;if U k No more than T k If the corresponding lightning strike event is not a critical trigger for the lightning strike, the backtracking object will be moved to the next lightning strike event and the operation will be repeated; if U k More than T k The corresponding lightning strike event is the one that causes the overvoltage peak value to exceed the flashover threshold for the first time. This is identified as a critical triggering lightning strike. The critical triggering lightning strike number, occurrence time, lightning current amplitude and polarity, and the value of the state parameter variable V before injection are recorded. k and the peak overvoltage U after injection k Stop backtracking.

[0066] It should be noted that in scenarios involving multiple lightning strikes, the critical triggering lightning strike is not necessarily the lightning event with the largest lightning current amplitude in the time-series lightning strike queue, nor is it necessarily the latest lightning strike in time sequence. Rather, it is the lightning strike in which the peak overvoltage after injection first exceeds the flashover determination threshold after the cumulative damage from preceding lightning strikes has reduced the state parameter variables to a certain level. An earlier high-amplitude lightning strike may not trigger a flashover because the state parameter variable values ​​are still high at that time, but the state parameter variable values ​​will decrease due to the deduction of the insulation damage increment. A later medium-amplitude lightning strike, encountering a state parameter variable value that has decreased due to preceding damage, triggers the final flashover with a relatively low overvoltage, and is thus identified as a critical triggering lightning strike. Step S53 uses the actual state parameter variables recorded round by round during the superimposed simulation and the peak value of the overvoltage as the basis for retrospection, so that the identification of key triggering lightning strikes is based on the direct support of simulation data. The identification conclusion has a traceable and verifiable quantitative basis, which is fundamentally different from the single static comparison method of the existing technology that directly takes the maximum amplitude lightning strike event as the analysis object. This is the core capability of this application to accurately locate the triggering cause in multiple lightning strike superimposed scenarios.

[0067] Step S54 determines the analysis period starting from the critical triggering lightning injection start time and ending at the flashover determination time recorded in step S44. During the analysis period, the current values ​​of each branch at each time step in the electrical geometric model are sequentially read from the calculation results of each branch saved on the simulation platform. The absolute value of the current is taken for each branch at each time step and accumulated over all time steps in the analysis period to obtain the cumulative amount of the absolute value of the current of each branch. The cumulative amounts of the absolute values ​​of the current of all branches are added together to obtain the total cumulative amount. The current shunting ratio of each branch is determined by the proportion of the cumulative amount of the absolute value of the current of each branch to the total cumulative amount. The current flow direction is traced from the injection node to the far end along the branch with the highest current shunting ratio, and the path of the branch with the highest current shunting ratio is determined as the first flow path. If the first flow path is that the lightning current enters from the suspension node of the lightning conductor, flows downward along the conductive elements of each section of the tower to the ground node, and then flows into the reference ground through the grounding resistance element, then the fault cause is determined to be backflashover. If the first flow path is that the lightning current enters from the suspension node of the conductor and propagates along the conductor extension element to both sides of the span, then the fault cause is determined to be side-strike. By determining the first flow path through the measured analysis of the current shunting ratio of each branch in the simulation rounds, the distinction of fault causes is based on the direct support of quantitative simulation data, rather than relying on pre-assumptions about the lightning strike scenario. This ensures that in the case of backflashover and side-strike scenarios coexisting in the time-series lightning strike queue, the determination of the cause of the critical triggering lightning strike can accurately correspond to the actual flow direction of the lightning current in the electrical geometry model when a flashover is triggered.

[0068] For example, step S51 outputs the result that the fault of tower No. 84 has been confirmed. Step S53 traces back from E1: the state parameter variable before E1 injection was 900 kV. T1 is determined by the product of 900 kV and the preset safety margin. The overvoltage peak value U1 of E1 is lower than T1, so E1 is not a critical triggering lightning strike, and the process moves to E2. The state parameter variable before E2 injection was V1. V1 is lower than 900 kV due to the damage from E1. T2 is determined by the product of V1 and the preset safety margin. T2 is lower than T1. The overvoltage peak value U2 of E2 is lower than T2, so E2 is not a critical triggering lightning strike, and the process moves to E4. Before E4 injection, the state parameter variable was V2. After the accumulation of damage from E1 and E2, V2 further decreased to below V1. T4 was determined by the product of V2 and the preset safety margin. T4 was lower than the initial static threshold determined based on 900 kV. The overvoltage peak value U4 of E4 was higher than T4. E4 was determined to be a critical trigger lightning strike. The occurrence time of E4 was recorded as 14 hours, 35 minutes, and 05 seconds, the lightning current amplitude was 30 kA, the polarity was negative, the state parameter variable before injection was V2, and the overvoltage peak value U4 after injection was recorded. Backtracking was then stopped. Step S54 uses the time period from the start of E4 injection to the flashover determination time as the analysis period. The current sequence of all branches was read and the current shunting ratio of each branch was calculated. The branch current shunting ratio propagating from the conductor suspension node to both sides of the span direction was the highest. The first flow path was the lightning current propagating from the conductor suspension node along the conductor extension element to both sides. The cause of the fault was determined to be a side-strike. The complete cause of the tripping fault at tower No. 84 is as follows: Two large-amplitude backflash lightning strikes, E1 and E2, struck tower No. 84 successively. The cumulative damage caused the state parameter variable to drop from the initial value of 900 kV to V2. Subsequently, a small-amplitude backflash event, E4, generated a backflash overvoltage U4 that exceeded the flashover determination threshold T4 at that time, triggering the final flashover. If only E4 is statically compared separately using existing technology, the overvoltage U4 generated by E4 is lower than the static threshold determined by the initial rated value of 900 kV, which would lead to the erroneous conclusion that no lightning strike could trigger a flashover, and the cause of this fault would not be able to be located.

[0069] In some embodiments, step S5 further includes: when the fault is caused by a backflash and the insulation damage coefficient is higher than a preset high-loss threshold, triggering a full-line lightning protection performance review of the line section where the target tower is located, the full-line lightning protection performance review includes steps C1 to C3: Step C1: Obtain the ledger parameters of all towers within the line section and the record of the most recent lightning trip; Step C2: Repeat the complete processing flow of steps S1 to S54 for each tower to identify potentially high-risk towers; Step C3: Generate preventative modification recommendations for the potentially high-risk towers identified in Step C2.

[0070] The conditions for triggering a full-line lightning protection performance review are limited to two dimensions: the cause of the fault and the degree of insulation damage. The cause of the fault must be backflashover, because the overvoltage amplitude in a backflashover scenario is closely related to the grounding resistance level. The geological conditions and grounding construction quality of adjacent towers in the same line section are usually correlated. If the insulation damage coefficient of a certain tower due to backflashover reaches a high level, it indicates that there may be a weak link in the grounding or insulation configuration of the line section. Other towers in the same section are likely to face similar problems, and it is necessary to carry out a device-based review. Backflashover scenarios usually have local characteristics and do not trigger a full-line review. The preset high-loss threshold is determined from the historical lightning fault records of the line where the target tower is located: all lightning trip fault records of the line where the target tower is located in the past few years are extracted from the operation and maintenance record device. After performing superimposed simulation analysis of each record from step S1 to step S46, the insulation damage coefficient corresponding to each fault is obtained. In the cases diagnosed as flashover faults, the distribution of insulation damage coefficients is statistically analyzed, and the 25th quantile of the distribution is taken as the preset high-loss threshold. This ensures that at least one-quarter of the historical confirmed cases are identified as high-risk when the preset high-loss threshold is reached. The actual distribution pattern of historical data provides a quantitative basis for setting the preset high-loss threshold.

[0071] In some embodiments, step S5 further includes: when the number of lightning events in the candidate lightning strike subset is greater than a preset event threshold, and the duration between the occurrence time of the first lightning strike and the occurrence time of the last lightning strike in the time-series lightning strike queue is less than a preset superposition duration, the current scenario is determined to be a multi-lightning strike superposition scenario, and a deep analysis command for the multi-lightning strike superposition scenario is triggered. The deep analysis command is used to instruct the generation of a weighted ranking table of the contribution weights of each lightning strike event to insulation damage. The preset event threshold is determined from the annual lightning activity characteristic report published by the lightning monitoring department of the target tower's location: the statistical item marked as the average number of consecutive return strokes of a multi-return lightning storm is searched, the statistical value is read, and the integer part after subtracting 1 from the statistical value is used as the preset event threshold. The preset superposition duration is determined from the same report by the statistical item marked as the 95th percentile of the consecutive return stroke time interval, the statistical value is read, and the product of the statistical value and the preset event threshold is used as the preset superposition duration, so that multiple lightning strikes exceeding the product value are not judged as scenarios with cumulative damage superposition effects because the time is too dispersed. After determining it to be a scenario of multiple lightning strikes, the insulation damage increments recorded after each injection in step S44 are read one by one from the insulation damage increments of each lightning event except for the critical triggering lightning strike. The insulation damage increments of all non-triggered lightning events are summed to obtain the total insulation damage increment. The contribution weight of each non-triggered lightning event is determined by the proportion of the insulation damage increment of each non-triggered lightning event to the total insulation damage increment. The non-triggered lightning events are sorted from high to low according to their contribution weight and filled into a sorting table. Each row shows the number of the lightning event, the occurrence time, the amplitude and polarity of the lightning current, the insulation damage increment value, and the contribution weight. At the end of the sorting table, a separate row is added to list the critical triggering lightning strike and marked as the final triggering event in the remarks column. This allows maintenance personnel to intuitively judge from the sorting table which preceding lightning strike contributed the most to the cumulative damage to the insulator, providing a quantitative reference for subsequent targeted investigation of similar lightning strike risks.

[0072] In some embodiments, after step S5, a diagnostic report containing a time-series lightning strike queue, insulation damage coefficient, and fault cause is output. A structured text report is generated, consisting of three parts: fault overview, time-series analysis, and cause diagnosis. The fault overview section includes the tower number and line name of the target tower, the trip signal trigger time, simulation judgment conclusion, insulation damage coefficient value, and, if determined to be a multi-lightning strike superposition scenario, the current scenario type is noted. The time-series analysis section displays, in tabular form, the number, occurrence time, lightning current amplitude and polarity, overvoltage peak value, flashover judgment threshold, and insulation damage increment of each lightning strike event mapped to the target tower. The row containing the key triggering lightning strike is specially marked, and a contribution weight ranking table is added when the scenario is determined to be a multi-lightning strike superposition scenario. The cause diagnosis section includes the fault cause type, the number and occurrence time of the key triggering lightning strike, the comparison value of the state parameter variable before injection and the overvoltage peak value after injection, and a textual description of the first flow path. When a viewing command is received from the maintenance terminal, the overvoltage timing waveform of each injection is plotted on the display interface with time as the horizontal axis and overvoltage as the vertical axis. Horizontal step lines are used to mark the flashover judgment threshold corresponding to the product of the current value of the state parameter variable before each injection and the preset safety margin. Vertical lines are used to mark the injection time point of each lightning strike event and the corresponding lightning current amplitude and polarity. The injection time point of critical lightning strikes is distinguished from other lightning strike events by a different marking method. This allows maintenance personnel to intuitively read the relationship between the time of each lightning strike injection and the gradual decrease of the flashover judgment threshold as damage accumulates from the waveform diagram, forming a complete fault analysis record that is traceable and verifiable.

[0073] In some embodiments, step S5 is followed by generating differentiated governance recommendations based on the cause of the failure and attaching the governance recommendations to the diagnostic report output. When the fault is caused by a lightning strike, the height of the lightning conductor suspension point above the ground, the height of the nearest side conductor suspension point above the ground, and the horizontal distance between them in the direction of the crossarm are read from the structural parameters retrieved in step S31. In the calculation tool, the quotient is obtained by using the horizontal distance as the numerator and the difference in height of the two suspension points above the ground as the denominator. The arctangent function of the quotient is used to obtain the current protection angle. The current annual lightning strike shielding failure rate is read from the lightning strike shielding failure rate estimation table in the standard code for line lightning protection design, using the current protection angle and the terrain category of the section where the target tower is located as the index. The equivalent protection angle correspondence table attached to the standard code is used to read the equivalent protection angle ranges that can be achieved by adding a lateral lightning rod at the top of the tower or the end of the upper crossarm, and by adjusting the position of the lightning conductor crossarm to reduce the current protection angle. The equivalent protection angles are substituted into the lightning strike shielding failure rate estimation table to read the corresponding expected annual lightning strike shielding failure rate. The achievable equivalent protection angle ranges and corresponding expected annual lightning strike shielding failure rates of the two types of measures are written into the treatment recommendations. When the fault is caused by backflashover, the rated lightning impulse withstand voltage is read from the insulator configuration parameters retrieved in step S31, and the power frequency grounding resistance is read from the grounding resistance parameters. The corresponding impulse coefficient and tower characteristic wave impedance standard reference value are retrieved from the line lightning protection design standard code using the target tower type as the index. The backflashover critical lightning current parameter attached to the standard code is substituted into the table to read the backflashover critical lightning current value. The current annual backflashover rate is read from the backflashover withstand level estimation table using the backflashover critical lightning current value and the annual ground flash density of the section as the index. The corresponding expected annual backflashover rate is generated by reducing the power frequency grounding resistance and increasing the number of insulator string configuration pieces, respectively, and written into the treatment recommendation. If the implementation of the two types of measures alone is insufficient to meet the annual backflashover rate standard requirements, the treatment recommendation will indicate that the two types of measures are recommended to be used in combination and provide the parameter combination that meets the requirements.

[0074] Preferably, step S5 determines whether the fault is confirmed or not based on the two exit scenarios of the superimposed simulation, and the supplementary determination of the last injection in step S52 compensates for the boundary omissions that may be caused by the reduction of the preset safety margin; after confirmation, the key triggering lightning strike is identified by comparing the value of the state parameter variables before each lightning strike injection with the overvoltage peak value by retrospectively tracing back each lightning strike event, based on the actual dynamic comparison record in the superimposed simulation process rather than the maximum amplitude event as the starting point for inference, so that the identification conclusion of the key triggering lightning strike has direct support from the simulation data; then, the first current path is determined by analyzing the current shunting ratio of each branch in the key triggering lightning strike simulation round. The system distinguishes between backflashover and flashover faults based on quantitative simulation data. When the fault is caused by backflashover and the insulation damage coefficient exceeds the preset high-loss threshold, a full-line lightning protection performance review is triggered. When the scenario is determined to be a multi-lightning-strike scenario, a ranking table of the insulation damage contribution weights of each lightning event is generated. Differentiated governance suggestions are generated based on the fault cause. Finally, the judgment conclusion, key triggering lightning information, overvoltage time-series waveform diagram showing the change of flashover judgment threshold with damage accumulation, and governance suggestions are summarized into a diagnostic report and output to the operation and maintenance terminal, forming a complete fault analysis process for multi-lightning-strike scenarios covering fault location, cause analysis, full-line risk assessment, and governance suggestion generation.

[0075] See Figure 3 This is a schematic diagram of the structure of a transmission line lightning strike fault analysis device provided in an embodiment of this application, comprising: The filtering module is used to respond to the triggering of the line trip signal, and to perform spatial correlation filtering on the set of lightning strike events within the first time window based on the fault distance interval of the line to obtain a candidate lightning strike subset; The mapping module is used to sort the lightning strike events in the candidate lightning strike subset and map each lightning strike event to the nearest tower on the line corridor, thus obtaining the time-series lightning strike queue and the target tower set; The module is used to construct a multi-lightning strike time-series simulation model of the target towers based on the ledger parameters of the target towers in the target tower set; The simulation module is used to inject the lightning current parameters of each lightning strike event into the multi-lightning strike time-series simulation model in the order of the time-series lightning strike queue for superposition simulation to obtain the insulation damage coefficient. The judgment module, based on the insulation damage coefficient and the results of superimposed simulation, determines whether the target tower has experienced flashover and identifies the cause of the fault.

[0076] Figure 3 The apparatus of the illustrated embodiment can be used to perform corresponding actions. Figure 1 The steps in the method embodiments shown are implemented in a similar manner and have similar technical effects, and will not be repeated here.

[0077] See Figure 4This is a schematic diagram of the hardware structure of an electronic device provided in an embodiment of this application. The electronic device 40 includes: a processor 41, a memory 42, and a computer program; wherein, The memory 42 is used to store computer programs, and the memory may also be flash memory. Computer programs may be, for example, application programs or functional modules that implement the methods described above.

[0078] The processor 41 is used to execute the computer program stored in the memory to implement the various steps performed by the device in the above method. For details, please refer to the relevant descriptions in the preceding method embodiments.

[0079] Alternatively, the memory 42 can be either standalone or integrated with the processor 41.

[0080] When the memory 42 is a device independent of the processor 41, the device may also include: Bus 43 is used to connect memory 42 and processor 41.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for analyzing lightning strike faults in power transmission lines, characterized in that, include: In response to the triggering of the line trip signal, the set of lightning strike events within the first time window is spatially correlated and filtered based on the fault distance interval of the line to obtain a candidate lightning strike subset; The lightning strike events in the candidate lightning strike subset are sorted and each lightning strike event is mapped to the nearest tower on the line corridor to obtain the time-series lightning strike queue and the target tower set; Based on the ledger parameters of the target towers in the target tower set, a multi-lightning-strike time-series simulation model of the target towers is constructed, including: retrieving the structural parameters, insulator configuration parameters, and grounding resistance parameters of the target towers in the target tower set from the production management device; building an electrical geometric model of the target towers in an electromagnetic transient simulation platform based on the structural parameters, insulator configuration parameters, and grounding resistance parameters; setting multiple excitation source interfaces in the electrical geometric model, the number of excitation source interfaces being consistent with the number of lightning strike events in the time-series lightning strike queue, with each excitation source interface corresponding to one lightning strike event; setting state parameter variables at the insulator string positions in the electrical geometric model; the state parameter variables are used to characterize the dynamic changes in insulation state, and the initial values ​​of the state parameter variables correspond to the baseline insulation level of the insulator configuration parameters; The lightning current parameters of each lightning strike event are sequentially injected into the multi-lightning-strike time-series simulation model according to the order of the time-series lightning strike queue for superposition simulation to obtain the insulation damage coefficient. This includes: selecting a lightning strike event sequentially from the time-series lightning strike queue as the current simulation event; converting the lightning current amplitude and polarity of the current simulation event into a lightning current waveform signal; injecting the lightning current waveform signal into the electrical geometry model through the corresponding excitation source interface at the occurrence time of the current simulation event; running the simulation platform to calculate the overvoltage across the insulator string of the target tower after this injection. The simulation process involves determining whether the overvoltage value is higher than the product of the current value of the state parameter variable and the preset safety margin. If so, a flashover is determined to have occurred, and the simulation ends. If not, the insulation damage increment caused by the lightning strike is calculated based on the magnitude and duration of the overvoltage value, and the state parameter variable is updated. The above steps are repeated until all lightning events in the time-series lightning strike queue have been injected and simulated, or a flashover is determined to have occurred during the simulation. The insulation damage coefficient is obtained based on the decrease ratio of the final value of the state parameter variable relative to its initial value. Based on the insulation damage coefficient and the results of the superimposed simulation, it is determined whether the target tower has experienced flashover and the cause of the fault is identified.

2. The method for analyzing lightning strike faults in transmission lines according to claim 1, characterized in that, The fault distance interval based on the line is used to perform spatial correlation filtering on the set of lightning strike events within the first time window to obtain a candidate lightning strike subset, including: The arrival time of the traveling wave when a line fault occurs is obtained from the traveling wave ranging device, and the fault distance is calculated. Based on the fault distance, the fault section is marked on the line geographic information map, and the length of the fault section covers the measurement error range of the fault distance; Calculate the geographical coordinates of each lightning strike event in the lightning strike event set within the first time window before and after the line trip signal triggering time, and the straight-line distance between each base tower in the fault section; Lightning strike events with a straight-line distance less than a preset distance threshold are retained, while lightning strike events with a straight-line distance greater than or equal to the preset distance threshold are removed. The retained lightning strike events are then used to form the candidate lightning strike subset.

3. The method for analyzing lightning strike faults in transmission lines according to claim 2, characterized in that, The process of sorting the lightning strike events in the candidate lightning strike subset and mapping each lightning strike event to the nearest tower on the line corridor to obtain a time-series lightning strike queue and a target tower set includes: The lightning strike events in the candidate lightning strike subset are sorted according to the order of their occurrence, and the sorted sequence is used as the time-series lightning strike queue. Determine the distance between the geographical coordinates of each lightning strike event in the time-series lightning strike queue and the base coordinates of each tower on the line corridor, and determine the tower with the smallest distance as the mapping tower of the corresponding lightning strike event; The towers to which all lightning strike events are mapped are counted. Towers that appear more than a preset mapping frequency threshold, as well as towers located within the fault distance range, are collectively included as elements in the target tower set.

4. The method for analyzing lightning strike faults in transmission lines according to claim 1, characterized in that, The determination of whether the target tower has experienced flashover and the identification of the cause of the fault, based on the insulation damage coefficient and the results of the superimposed simulation, includes: If the simulation process determines that a flashover has occurred before all lightning strike events have been injected, then the result that the fault has been diagnosed will be output. If the simulation process fails to determine that a flashover has occurred after all lightning events have been injected, the overvoltage value obtained from the last simulation is compared with the final value of the state parameter variable. If the overvoltage value is higher than the final value of the state parameter variable, the result of fault diagnosis is output; otherwise, the result of fault diagnosis is output. For cases where the fault has been diagnosed, the simulation process records are traced back to identify the lightning strike event that caused the overvoltage value to exceed the current value of the state parameter variable as the key triggering lightning strike. Analyze the first flow path of the lightning current that triggered the key lightning strike in the electrical geometric model. If the first flow path is through the lightning conductor to the tower and then to the insulator string, the fault is determined to be caused by backflashover. If the first flow path is a direct strike to the conductor through the insulator string, the fault is determined to be caused by backflashover.

5. The method for analyzing lightning strike faults in transmission lines according to claim 1, characterized in that, The method further includes: Before constructing the multi-lightning-strike time-series simulation model of the target tower, obtain the ledger update record of the target tower; When there is a record of updated ledger entries and the update time is later than the preset ledger freeze time, a parameter review prompt will be issued. The actual parameters of the target tower, confirmed by manual review, are received and used to replace the ledger parameters in order to construct the multi-lightning strike time-series simulation model.

6. The method for analyzing lightning strike faults in transmission lines according to claim 1, characterized in that, The method further includes: When the fault is caused by a counterattack and the insulation damage coefficient is higher than the preset high-loss threshold, a full-line lightning protection performance review of the line section where the target tower is located is triggered. The review of the lightning protection performance of the entire line includes: obtaining the ledger parameters of all towers in the line section and the record of the most recent lightning trip; For each tower, a multi-lightning strike time-series simulation model was re-executed, along with subsequent simulation and judgment steps, to identify potentially high-risk towers. Preventive modification recommendations are generated for the identified potentially high-risk towers.

7. The method for analyzing lightning strike faults in transmission lines according to claim 1, characterized in that, The method further includes: When the number of lightning strike events in the candidate lightning strike subset is greater than a preset event threshold, and the duration between the occurrence time of the first lightning strike event and the occurrence time of the last lightning strike event in the time-series lightning strike queue is less than a preset superposition duration, the current scenario is determined to be a multi-lightning strike superposition scenario. A deep analysis command is triggered for the multiple lightning strike scenarios, which instructs the generation of a weighted table of the contribution of each lightning strike event to insulation damage.

8. A transmission line lightning strike fault analysis device, employing the transmission line lightning strike fault analysis method as described in any one of claims 1 to 7, characterized in that, include: The filtering module is used to respond to the triggering of the line trip signal, and to perform spatial correlation filtering on the set of lightning strike events within the first time window based on the fault distance interval of the line to obtain a candidate lightning strike subset; The mapping module is used to sort the lightning strike events in the candidate lightning strike subset and map each lightning strike event to the nearest tower on the line corridor to obtain the time-series lightning strike queue and the target tower set. A construction module is used to construct a multi-lightning-strike time-series simulation model of the target towers based on the ledger parameters of the target towers in the target tower set. This includes: retrieving structural parameters, insulator configuration parameters, and grounding resistance parameters of the target towers from the production management device; building an electrical geometric model of the target towers in an electromagnetic transient simulation platform based on the structural parameters, insulator configuration parameters, and grounding resistance parameters; setting multiple excitation source interfaces in the electrical geometric model, the number of which is consistent with the number of lightning strike events in the time-series lightning strike queue, with each excitation source interface corresponding to one lightning strike event; and setting state parameter variables at the insulator string positions in the electrical geometric model. These state parameter variables characterize the dynamic changes in insulation state, and their initial values ​​correspond to the baseline insulation level of the insulator configuration parameters. The simulation module is used to sequentially inject the lightning current parameters of each lightning strike event into the multi-lightning strike time-series simulation model according to the order of the time-series lightning strike queue for superposition simulation to obtain the insulation damage coefficient. This includes: selecting a lightning strike event sequentially from the time-series lightning strike queue as the current simulation event; converting the lightning current amplitude and polarity of the current simulation event into a lightning current waveform signal; injecting the lightning current waveform signal into the electrical geometry model through the corresponding excitation source interface at the occurrence time of the current simulation event; and running the simulation platform to calculate the insulation damage coefficient at both ends of the insulator string of the target tower after this injection. The overvoltage value is determined; it is then determined whether the overvoltage value is higher than the product of the current value of the state parameter variable and the preset safety margin. If so, a flashover is determined to have occurred, and the simulation ends; if not, the insulation damage increment caused by this lightning strike is calculated based on the magnitude and duration of the overvoltage value, and the state parameter variable is updated. The above steps are repeated until all lightning strike events in the time-series lightning strike queue have been injected and simulated, or a flashover is determined to have occurred during the simulation. The insulation damage coefficient is obtained based on the decrease ratio of the final value of the state parameter variable relative to the initial value of the state parameter variable. The determination module, based on the insulation damage coefficient and the results of the superimposed simulation, determines whether the target tower has experienced flashover and identifies the cause of the fault.

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