A lightning stroke under transmission tower state monitoring and evaluation method

Abstract

The application discloses a lightning stroke transmission tower state monitoring and evaluation method, relates to the technical field of state monitoring, and collects the ground potential signal data set of the transmission tower at the lightning moment in the system operation, carries out time synchronization processing on the signals of each monitoring point, obtains the ground potential mutation time sequence set, calculates the propagation time delay set between the monitoring points, establishes the propagation characteristic model in combination with the geometric distance set of the tower to the grounding body, generates the propagation characteristic distance set, and compares with the preset reference propagation characteristic distance set, calculates the deviation ratio set, determines that the grounding performance is abnormal when the deviation ratio set exceeds the threshold value, obtains the grounding dynamic impedance set, calculates the grounding performance index according to the grounding dynamic impedance set and the ground potential mutation energy set, compares with the historical standard performance index set again, generates the alarm set if the deviation exceeds the safety limit value, and outputs the safety control instruction to the monitoring system.

Description

Technical Field

[0001] This invention relates to the field of condition monitoring technology, specifically a method for condition monitoring and evaluation of transmission towers under lightning strikes. Background Technology

[0002] Transmission towers, as crucial supporting structures for high-voltage transmission lines, directly impact the stability and continuity of the power grid. With the continuous increase in transmission line voltage levels and the expansion of new energy grid integration, transmission tower condition monitoring technology has gradually shifted from traditional periodic manual inspections to real-time online monitoring. Traditional condition monitoring primarily focuses on static indicators such as tower structural deformation, insulator contamination, and conductor temperature rise. However, under strong lightning conditions, the transient electrical response characteristics of the tower become a key factor determining its safety performance. Under lightning strikes, towers not only suffer direct lightning strikes but also experience combined electrical stresses such as ground potential backflashover and tower foot current surges, leading to partial discharge, insulation flashover, or deterioration of grounding electrode performance. To address this issue, existing lightning strike condition monitoring largely relies on single-point current sensors or surge arrester discharge counters, which cannot accurately reflect the propagation path and diffusion characteristics of lightning current within the grounding grid system.

[0003] Although existing technologies exist for detecting the lightning protection performance of transmission towers, they generally suffer from problems such as slow response, limited analytical dimensions, and low data utilization. On the one hand, traditional lightning monitoring systems typically deploy single-point measuring devices only at the lightning current path or insulators, making it difficult to capture the dynamic changes in ground potential backflash, leading to significant biases in the assessment of the grounding system's condition. On the other hand, existing methods often focus on determining the "presence" of a lightning strike, neglecting the decay of grounding performance over time after a lightning strike, and lacking a comprehensive assessment capability of the energy absorption and discharge characteristics of the grounding body.

[0004] Furthermore, existing solutions have poor reliability in complex geological environments, especially in areas with non-uniform soil conductivity and significant humidity variations. The propagation path is greatly affected by geological parameters, and traditional static models cannot accurately reflect actual propagation patterns. In actual operation, grounding anomalies caused by lightning strikes are often concealed and sudden. Due to the extremely short duration and high impact energy of lightning strikes, when the ground grid system has problems such as poor contact, corrosion, or structural aging, the lightning current cannot quickly flow into the ground, causing a sharp rise in ground potential backflash voltage. If the monitoring system cannot capture the propagation delay change of ground potential at the moment of lightning strike, errors in grounding performance assessment are highly likely, leading to an inability to accurately identify the degree of degradation of the grounding body. In addition, some existing systems rely on fixed models or static parameters for analysis, failing to consider the dynamic nonlinear characteristics of the lightning strike process, resulting in data distortion or misjudgment. For example, in cases of sudden changes in humidity or a sudden increase in soil resistivity, the increased propagation path delay can lead to abnormal concentration of local potential at the tower feet, causing secondary flashover phenomena, which in severe cases can cause lightning protection device failure or main transformer protection malfunction. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for monitoring and evaluating the condition of transmission towers under lightning strikes, thus solving the problems mentioned in the background section.

[0006] To achieve the above objectives, the present invention provides a method for monitoring and evaluating the condition of transmission towers under lightning strikes, comprising the following steps:

[0007] S1: Collect the ground potential signal data set Sig of the transmission tower at the moment of lightning strike, and perform time synchronization processing on the signals of each monitoring point to obtain the ground potential change time series set Tim;

[0008] S2: Calculate the propagation delay set Del between each monitoring point based on the ground potential change time series set Tim, and establish a propagation characteristic model by combining the geometric distance set Geo from the tower to the grounding body, generating the propagation characteristic distance set Dis;

[0009] S3: Compare the propagation characteristic distance set Dis with the preset reference propagation characteristic distance set Ref, calculate the deviation ratio set Rat, and when the deviation ratio set Rat exceeds the threshold Thr, determine that there is an abnormality in the grounding performance and obtain the grounding dynamic impedance set Imp;

[0010] S4: The grounding performance index Gnd is calculated based on the grounding dynamic impedance set Imp and the ground potential change energy set Ene, which is used to characterize the discharge capacity of the grounding body under lightning strike;

[0011] S5: Compare the grounding performance index Gnd with the historical standard performance index set Std. If the deviation exceeds the safety limit Lim, generate an alarm set Alm and output the safety control command Cmd to the monitoring system.

[0012] Preferably, the ground potential signal data set Sig undergoes smoothing preprocessing via a time-filtering function Flt during acquisition to eliminate high-frequency noise, inductive coupling interference, and waveform distortion caused by transient eddy currents from lightning strikes, thereby improving the signal's temporal continuity and voltage change accuracy. The time-filtering function Flt dynamically adjusts the sampling interval using a sliding window method during processing to adapt to the characteristics of the ground potential signal at different sampling frequencies. By smoothing the variance difference between the instantaneous value ti and the interval mean μ of each sampling interval, abnormal abrupt changes are suppressed. The time-filtering function Flt is defined as follows:

[0013] ;

[0014] Where ti is the instantaneous value of the ground potential signal at the sampling time, μ is the mean of the sampling interval, n is the number of sampling points, and the result of Flt is used to correct the accuracy of the time series set Tim, thereby improving the computational stability of the propagation delay set Del.

[0015] Preferably, the calculation of the propagation characteristic distance set Dis includes the construction of the propagation model equation and the environmental correction steps. The propagation model equation takes the surface propagation velocity constant, soil moisture correction factor and ground resistance non-uniformity coefficient as the main parameters input, and comprehensively corrects the diffusion characteristics of lightning current on the surface under different geological conditions through multi-parameter correlation modeling.

[0016] The calculation of the propagation feature distance set Dis includes the propagation model equations:

[0017] ;

[0018] Where c is the surface lightning current propagation velocity constant, α is the soil moisture correction factor, and k is the ground resistance nonuniformity coefficient. The above propagation model equations enable differentiated compensation for lightning propagation effects under different geological environments.

[0019] In the calculation of the propagation characteristic distance set Dis, the system first extracts the geometric distance set Geo based on the tower foundation structure, grounding electrode shape, and geological layer thickness information, and then matches and maps it with the propagation delay set Del to establish a correspondence between "time difference and spatial propagation". This mapping relationship is used to reflect the propagation characteristics of the lightning current wavefront in different soil conductive paths, so that Dis not only represents the distance in a geometric sense, but also reflects the phase delay characteristics in the electromagnetic wave propagation process. After calculation, the propagation characteristic distance set Dis is corrected by an environmental adaptation module. The environmental adaptation module dynamically corrects the model output results based on the surface moisture content, soil density, and climate humidity parameters of the monitoring site to avoid the deviation of propagation distance judgment caused by environmental non-uniformity. By establishing a dynamic matching model between the propagation characteristic distance set Dis and the propagation delay set Del, the real-time prediction of the trend of lightning current diffusion velocity can be achieved. This method further identifies local grounding grid contact anomalies, tower foundation soil conductivity degradation, and hidden faults such as poor ground wire contact through statistical analysis of the propagation characteristics of different monitoring points. Ultimately, the propagation characteristic distance set Dis serves as a key input parameter for subsequent impedance inversion and performance evaluation, and its accuracy directly determines the reliability of grounding status determination.

[0020] Preferably, the solution of the grounding dynamic impedance set Imp is based on the joint characteristic analysis of the ground potential change signal and the lightning current signal. By back-calculating the difference in the response time of the two, the change in dynamic electrical impedance at the moment of lightning strike is obtained.

[0021] Furthermore, the calculation process of the grounding dynamic impedance set Imp comprehensively considers the soil dielectric constant, contact resistance, and signal steepness factor, and is used to reflect the energy discharge capacity and transient conduction performance of the grounding system under lightning strike.

[0022] The solution for the grounding dynamic impedance set Imp is obtained using the impedance inverse function Fun, which is defined as follows:

[0023] ;

[0024] Where ΔV is the amplitude of the ground potential change at the moment of lightning strike, ΔI is the amplitude of the lightning current change, β is the soil dielectric adjustment coefficient, and η is the signal steepness factor. This function Fun can quantify the degree of impedance disturbance caused by the propagation of the lightning wave within the grounding grid structure.

[0025] Preferably, the grounding performance index Gnd is determined by the changing trends of the grounding dynamic impedance set Imp and the ground potential change energy set Ene, and is used to characterize the energy absorption and discharge characteristics of the grounding system under lightning strike; the grounding performance index Gnd is used to conduct a health assessment of the grounding state after lightning strike, and its numerical change can reflect the conductivity of the grounding body and the intensity of ground potential backflash.

[0026] The grounding performance index Gnd is calculated using the following formula:

[0027] ;

[0028] Where Imp is the mean of the set of dynamic grounding impedances, Ene is the integral result of the set of ground potential change energy, Ref is the median of the set of reference propagation characteristic distances, and Gnd is used to comprehensively reflect the energy absorption and discharge efficiency during lightning strikes. The smaller its value, the healthier the grounding system.

[0029] Preferably, the grounding performance index Gnd is subjected to graded analysis to establish a two-layer safety judgment mechanism of primary assessment and secondary assessment; the primary assessment determines the primary risk level set Lev1 based on the comparison results of the grounding performance index Gnd and the safety limit Lim; the secondary assessment calculates the stability coefficient Sta and forms a comprehensive safety factor Saf based on the changing trends of the dynamic impedance set Imp and the propagation delay set Del, which is used to reflect the overall stability of the grounding grid system under different lightning strike intensities.

[0030] The secondary evaluation constructs a stability coefficient Sta based on the changing trends of Lev1 and the dynamic impedance set Imp, and calculates the comprehensive safety factor Saf:

[0031] ;

[0032] When Saf falls below the threshold Thr2, the system triggers a secondary alarm event.

[0033] Preferably, the stability coefficient Sta is jointly determined by the statistical volatility of the grounding dynamic impedance set Imp and the propagation delay set Del. The stability of the lightning response process is characterized by analyzing the ratio of its standard deviation to its mean. When the stability coefficient Sta exceeds a preset threshold, the system determines that there is a risk of dynamic imbalance in the grounding state and inputs this risk parameter into the secondary evaluation module for comprehensive judgment.

[0034] The stability coefficient Sta is jointly constructed from the standard deviation of the dynamic impedance set Imp and the coefficient of variation of the propagation delay set Del, and is defined as follows:

[0035] ;

[0036] Where σImp and σDel are the standard deviations of Imp and Del, respectively, and μImp and μDel are their mean values; Sta can reflect the dynamic fluctuation of the grounding state and realize the adaptive evaluation of multi-source parameters.

[0037] Preferably, the alarm set Alm is generated based on a dual-parameter condition judgment mechanism of the comprehensive safety factor Saf and the grounding performance index Gnd. When Saf is lower than the safety threshold and Gnd exceeds the safety limit, the system generates a valid alarm event. The alarm set Alm uses a logical judgment method to form a binary output result so that the system can realize automatic identification and control response.

[0038] The generation logic of the alarm set Alm is based on a dual-condition triggering mechanism of the comprehensive safety factor Saf and the grounding performance index Gnd, and is defined as follows:

[0039] If Saf < Thr2 and Gnd > Lim, then Alm = {1};

[0040] If Saf ≥ Thr2 and Gnd ≤ Lim, then Alm = {0};

[0041] This mechanism is used to improve the accuracy of alarms and avoid misjudgments based on a single parameter.

[0042] Preferably, the safety control command Cmd is generated by the alarm set Alm. The safety control command Cmd includes three types: current limiting control command, isolation control command, and signal verification command, which are used to realize rapid protection and operation adjustment of the lightning-affected area. After the safety control command Cmd is executed, it triggers the real-time update of the grounding parameter set Par to maintain the consistency between the monitoring system and the field status.

[0043] Preferably, the method further establishes a joint evaluation mechanism of time and space dimensions, and realizes multi-dimensional determination of lightning strike ground potential backflash path by performing correlation analysis between the set of time series signal change rates and the set of spatial distances;

[0044] The spatial response evaluation value Res is calculated as follows:

[0045] ;

[0046] Where n is the number of monitoring points.

[0047] The spatial response evaluation value Res and the grounding performance index Gnd together form a multi-dimensional comprehensive evaluation matrix, which is used to generate a comprehensive diagnostic report on lightning strike status, and realize a multi-dimensional visual evaluation of the ground potential backflash path and grounding health status.

[0048] This invention provides a method for monitoring and evaluating the condition of transmission towers under lightning strikes, which has the following beneficial effects:

[0049] (1) When the system is running, the data set of ground potential signal of the transmission tower at the moment of lightning strike is collected, and the signals of each monitoring point are processed in time synchronization to obtain the time series set of ground potential change. The propagation delay set between each monitoring point is calculated, and the propagation characteristic model is established in combination with the geometric distance set from the tower to the grounding body. The propagation characteristic distance set is generated and compared with the preset reference propagation characteristic distance set. The deviation ratio set is calculated. When the deviation ratio set exceeds the threshold, it is determined that there is an abnormality in the grounding performance. The grounding dynamic impedance set is obtained. The grounding performance index is calculated based on the grounding dynamic impedance set and the ground potential change energy set. Then it is compared with the historical standard performance index set. If the deviation exceeds the safety limit, an alarm set is generated and a safety control command is output to the monitoring system.

[0050] (2) This invention establishes a multi-level evaluation system that includes signal acquisition, time delay analysis, propagation modeling, impedance inversion, performance index evaluation, and comprehensive judgment, thereby realizing dynamic monitoring and quantitative evaluation of the grounding status of transmission towers under lightning strikes. Through the progressive data processing flow from steps S1 to S5, this invention can acquire the ground potential signal data set Sig in real time at the moment of lightning strike, extract the ground potential change time series Tim, and calculate the propagation delay set Del and the propagation characteristic distance set Dis, thus accurately reflecting the propagation path and energy distribution characteristics of ground potential backflash. At the same time, the grounding performance index Gnd is constructed using the grounding dynamic impedance set Imp and the ground potential change energy set Ene to achieve quantitative characterization of the health status of the grounding body. Based on the comparison of the historical performance standard set Std, this invention further outputs the alarm set Alm and the safety control command Cmd, forming a closed-loop monitoring mechanism of "acquisition-calculation-evaluation-control", enabling the dynamic control of the operation status of transmission towers under lightning strike conditions throughout the entire process.

[0051] (3) Compared with the prior art, this invention significantly improves the accuracy and timeliness of grounding status assessment by introducing a modeling mechanism based on ground potential backflash propagation delay analysis without increasing hardware sensing devices. Traditional monitoring methods mostly rely on single-point current detection or insulation flashover counting, which cannot reflect the diffusion law of current in the grounding grid during lightning strikes. This invention innovatively proposes a joint solution method for the propagation characteristic distance set Dis and the propagation delay set Del, and establishes an environmental adaptation model by combining correction parameters such as soil moisture and ground resistance non-uniformity, thereby realizing dynamic correction of lightning current propagation characteristics under complex geological conditions. In addition, this invention introduces the inversion calculation of the grounding dynamic impedance set Imp, which transforms the lightning strike response from a single current amplitude judgment to a multi-parameter collaborative analysis, breaking through the limitation of traditional methods that only rely on peak signals for risk identification. By setting up a two-layer assessment system (primary assessment and secondary assessment), this invention realizes hierarchical management of grounding performance, can provide early warning of potential risks in the early stage of lightning strike events, and significantly improve the accuracy and response speed of transmission tower grounding safety monitoring.

[0052] (4) The implementation of this invention not only realizes the visualization analysis of the lightning propagation process, but also greatly improves the intelligence and real-time performance of grounding status diagnosis. Through multi-dimensional data fusion and the calculation of the comprehensive safety factor Saf, this invention can quickly determine the grounding performance degradation trend, identify dynamic imbalance states, and complete automated protection control through the alarm set Alm and the safety control command Cmd. Compared with traditional static monitoring methods, the evaluation system of this invention has higher sensitivity and robustness, and can operate stably in complex terrain, different soil conditions, and high thunderstorm environments. Practice has proven that this method can effectively reduce the probability of transmission line tripping and equipment damage caused by ground potential backflash, tower foot current concentration, and grounding performance degradation, realizing the technological transformation from passive monitoring to active protection. Thus, this invention has achieved a comprehensive improvement in evaluation accuracy, response speed, and system reliability in the field of lightning protection for transmission towers, providing highly adaptable and practical technical support for the safe operation of new energy grid-connected transmission systems. Attached Figure Description

[0053] Figure 1 This is a schematic diagram illustrating the steps of a method for monitoring and evaluating the condition of a transmission tower under lightning strikes according to the present invention.

[0054] Figure 2 This is a flowchart of a method for monitoring and evaluating the condition of power transmission towers under lightning strikes according to the present invention. Detailed Implementation

[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0056] Example 1

[0057] This invention provides a method for monitoring and evaluating the condition of transmission towers under lightning strikes. Please refer to [link / reference]. Figure 1 This includes the following steps:

[0058] S1: Collect the ground potential signal data set Sig of the transmission tower at the moment of lightning strike, and perform time synchronization processing on the signals of each monitoring point to obtain the ground potential change time series set Tim;

[0059] S2: Calculate the propagation delay set Del between each monitoring point based on the ground potential change time series set Tim, and establish a propagation characteristic model by combining the geometric distance set Geo from the tower to the grounding body, generating the propagation characteristic distance set Dis;

[0060] S3: Compare the propagation characteristic distance set Dis with the preset reference propagation characteristic distance set Ref, calculate the deviation ratio set Rat, and when the deviation ratio set Rat exceeds the threshold Thr, determine that there is an abnormality in the grounding performance and obtain the grounding dynamic impedance set Imp;

[0061] S4: The grounding performance index Gnd is calculated based on the grounding dynamic impedance set Imp and the ground potential change energy set Ene, which is used to characterize the discharge capacity of the grounding body under lightning strike;

[0062] S5: Compare the grounding performance index Gnd with the historical standard performance index set Std. If the deviation exceeds the safety limit Lim, generate an alarm set Alm and output the safety control command Cmd to the monitoring system.

[0063] In this embodiment, a set of ground potential signal data of the transmission tower at the moment of lightning strike is collected, and the signals of each monitoring point are processed in time synchronization to obtain a set of ground potential change time series. The set of propagation delay between each monitoring point is calculated, and a propagation characteristic model is established by combining the set of geometric distances from the tower to the grounding body to generate a set of propagation characteristic distances. This set of propagation characteristic distances is compared with a preset reference set of propagation characteristic distances to calculate a set of deviation ratios. When the set of deviation ratios exceeds a threshold, it is determined that there is an anomaly in the grounding performance, and the set of grounding dynamic impedances is obtained. The grounding performance index is calculated based on the set of grounding dynamic impedances and the set of ground potential change energy, and then compared with the set of historical standard performance indices. If the deviation exceeds the safety limit, an alarm set is generated, and a safety control command is output to the monitoring system.

[0064] Example 2

[0065] This embodiment is an explanation based on Embodiment 1. Please refer to it. Figure 1 Specifically: the ground potential signal data set Sig undergoes smoothing preprocessing via a time-filtering function Flt during acquisition to eliminate high-frequency noise, inductive coupling interference, and waveform distortion caused by transient eddy currents from lightning strikes, thereby improving the signal's temporal continuity and voltage change accuracy. The time-filtering function Flt dynamically adjusts the sampling interval using a sliding window method during processing to adapt to the characteristics of the ground potential signal at different sampling frequencies. By smoothing the variance difference between the instantaneous value ti and the interval mean μ in each sampling interval, abnormal abrupt changes are suppressed. The time-filtering function Flt is defined as follows:

[0066] ;

[0067] Where ti is the instantaneous value of the ground potential signal at the sampling time, μ is the mean of the sampling interval, n is the number of sampling points, and the result of Flt is used to correct the accuracy of the time series set Tim, thereby improving the computational stability of the propagation delay set Del.

[0068] The calculation of the propagation characteristic distance set Dis includes the construction of the propagation model equation and the environmental correction steps. The propagation model equation takes the surface propagation velocity constant, soil moisture correction factor and ground resistance non-uniformity coefficient as the main parameters input, and comprehensively corrects the diffusion characteristics of lightning current on the surface under different geological conditions through multi-parameter correlation modeling.

[0069] The calculation of the propagation feature distance set Dis includes the propagation model equations:

[0070] ;

[0071] Where c is the surface lightning current propagation velocity constant, α is the soil moisture correction factor, and k is the ground resistance nonuniformity coefficient. The above propagation model equations enable differentiated compensation for lightning propagation effects under different geological environments.

[0072] In the calculation of the propagation characteristic distance set Dis, the system first extracts the geometric distance set Geo based on the tower foundation structure, grounding electrode shape, and geological layer thickness information, and then matches and maps it with the propagation delay set Del to establish a correspondence between "time difference and spatial propagation". This mapping relationship is used to reflect the propagation characteristics of the lightning current wavefront in different soil conductive paths, so that Dis not only represents the distance in a geometric sense, but also reflects the phase delay characteristics in the electromagnetic wave propagation process. After calculation, the propagation characteristic distance set Dis is corrected by an environmental adaptation module. The environmental adaptation module dynamically corrects the model output results based on the surface moisture content, soil density, and climate humidity parameters of the monitoring site to avoid the deviation of propagation distance judgment caused by environmental non-uniformity. By establishing a dynamic matching model between the propagation characteristic distance set Dis and the propagation delay set Del, the real-time prediction of the trend of lightning current diffusion velocity can be achieved. This method further identifies local grounding grid contact anomalies, tower foundation soil conductivity degradation, and hidden faults such as poor ground wire contact through statistical analysis of the propagation characteristics of different monitoring points. Ultimately, the propagation characteristic distance set Dis serves as a key input parameter for subsequent impedance inversion and performance evaluation, and its accuracy directly determines the reliability of grounding status determination.

[0073] In this embodiment, a collaborative calculation mechanism of the time filtering function Flt and the propagation feature distance set Dis is introduced in the two key stages of ground potential signal acquisition and propagation modeling, achieving high-fidelity acquisition and high-precision modeling analysis of lightning strike signals. Firstly, the time filtering function Flt employs a sliding window dynamic smoothing method to correct variance and suppress noise in the instantaneous signal within the sampling interval. This effectively eliminates high-frequency waveform distortion caused by lightning transient eddy currents and ground-inductive coupling interference, and enhances the temporal continuity and voltage change accuracy of the ground potential signal, making the subsequent time series set Tim more stable and reliable. Secondly, the calculation of the propagation feature distance set Dis, based on the established propagation model equations, comprehensively incorporates multiple environmental parameters such as the surface propagation velocity constant, soil moisture correction factor, and ground resistance non-uniformity coefficient. Dynamic compensation under different geological conditions is achieved through an environmental adaptation module, making the calculation of the lightning current propagation path more consistent with actual physical laws. This method can stably extract propagation features under complex terrain and variable climate conditions, achieving joint modeling from the time dimension to the spatial dimension. Through the above-described optimized design, this invention significantly improves the sampling accuracy of ground potential signals and the environmental adaptability of propagation modeling, solving problems such as signal distortion, large propagation delay calculation errors, and weak model generalization ability in traditional lightning strike monitoring. Compared with existing techniques that rely solely on current peak values ​​or single-point voltage measurements, this invention can capture propagation differences during lightning strikes in real time, accurately identify the performance change trends of grounding bodies, and provide a higher-confidence data foundation for subsequent impedance inversion and grounding health assessment, thereby achieving high-precision and intelligent assessment of the state of transmission towers under lightning strikes.

[0074] Example 3

[0075] This embodiment is an explanation based on Embodiment 1. Please refer to it. Figure 1 Specifically: The solution of the grounding dynamic impedance set Imp is based on the joint characteristic analysis of the ground potential change signal and the lightning current signal. By back-calculating the difference in the response time of the two, the change in dynamic electrical impedance at the moment of lightning strike is obtained.

[0076] Furthermore, the calculation process of the grounding dynamic impedance set Imp comprehensively considers the soil dielectric constant, contact resistance, and signal steepness factor, and is used to reflect the energy discharge capacity and transient conduction performance of the grounding system under lightning strike.

[0077] The solution for the grounding dynamic impedance set Imp is obtained using the impedance inverse function Fun, which is defined as follows:

[0078] ;

[0079] Where ΔV is the amplitude of the ground potential change at the moment of lightning strike, ΔI is the amplitude of the lightning current change, β is the soil dielectric adjustment coefficient, and η is the signal steepness factor. This function Fun can quantify the degree of impedance disturbance caused by the propagation of the lightning wave within the grounding grid structure.

[0080] The grounding performance index Gnd is determined by the changing trends of the grounding dynamic impedance set Imp and the ground potential change energy set Ene, and is used to characterize the energy absorption and discharge characteristics of the grounding system under lightning strikes. The grounding performance index Gnd is used to conduct a health assessment of the grounding state after a lightning strike, and its numerical change can reflect the conductivity of the grounding body and the intensity of ground potential backflash.

[0081] The grounding performance index Gnd is calculated using the following formula:

[0082] ;

[0083] Where Imp is the mean of the set of dynamic grounding impedances, Ene is the integral result of the set of ground potential change energy, Ref is the median of the set of reference propagation characteristic distances, and Gnd is used to comprehensively reflect the energy absorption and discharge efficiency during lightning strikes. The smaller its value, the healthier the grounding system.

[0084] The grounding performance index Gnd is subjected to a graded analysis to establish a two-layer safety judgment mechanism of primary assessment and secondary assessment. The primary assessment determines the primary risk level set Lev1 based on the comparison results between the grounding performance index Gnd and the safety limit Lim. The secondary assessment calculates the stability coefficient Sta and forms a comprehensive safety factor Saf based on the changing trends of the dynamic impedance set Imp and the propagation delay set Del, which is used to reflect the overall stability of the grounding grid system under different lightning strike intensities.

[0085] The secondary evaluation constructs a stability coefficient Sta based on the changing trends of Lev1 and the dynamic impedance set Imp, and calculates the comprehensive safety factor Saf:

[0086] ;

[0087] When Saf falls below the threshold Thr2, the system triggers a secondary alarm event.

[0088] In this embodiment, the present invention constructs a dynamic evaluation system based on time response differences and energy change trends by introducing the inverse calculation of the grounding dynamic impedance set Imp and the multidimensional quantitative analysis of the grounding performance index Gnd, thereby achieving accurate determination of the grounding performance of transmission towers under lightning strikes. Firstly, the solution of the grounding dynamic impedance set Imp is based on the joint characteristics of the ground potential abrupt change signal and the lightning current signal, enabling real-time capture of the amplitude and change trend of impedance disturbances at the moment of lightning strike, thus reflecting the transient dynamic characteristics of the grounding grid's conductivity and discharge capacity. Through the establishment of the impedance inversion function Fun, the system can quantitatively describe the change in propagation impedance of lightning waves in non-uniform soil structures, overcoming the technical limitation of traditional static resistance measurement methods that cannot reflect the instantaneous conduction state. Secondly, the introduction of the grounding performance index Gnd allows for the quantitative expression of the health status of the grounding system, comprehensively considering the influence of multiple factors such as lightning energy absorption, discharge efficiency, and ground potential backflash strength, realizing a technical transformation from single-parameter judgment to a three-dimensional collaborative evaluation of energy-impedance-propagation. Thirdly, by conducting a graded analysis of the grounding performance index Gnd, this invention constructs a two-layer judgment system of primary and secondary assessments. The introduction of the stability coefficient Sta and the comprehensive safety factor Saf enables the system to dynamically identify grounding anomaly trends under different lightning strike intensities and geological conditions. Through this synergistic mechanism, this invention not only achieves real-time monitoring of lightning strike response characteristics but also provides early warnings of latent faults such as grounding body performance degradation, sudden changes in contact resistance, and blockage of grounding grid conductive channels. Compared to existing traditional methods that rely solely on voltage and current peak values ​​for risk assessment, this invention can accurately capture energy transfer and impedance coupling changes during lightning strikes, achieving a leap from "event detection" to "performance assessment." Experimental verification shows that this method significantly improves the resolution and stability of grounding condition diagnosis, enhances assessment accuracy, risk identification sensitivity, and system adaptability, providing reliable technical support for the safe operation of transmission towers in high-thunderstorm, variable geological environments.

[0089] Example 4

[0090] This embodiment is an explanation based on Embodiment 1. Please refer to it. Figure 1 Specifically: the stability coefficient Sta is determined by the statistical volatility of the grounding dynamic impedance set Imp and the propagation delay set Del. By analyzing the ratio of its standard deviation to mean, the stability of the lightning strike response process is characterized. When the stability coefficient Sta exceeds the preset threshold, the system determines that there is a risk of dynamic imbalance in the grounding state and inputs this risk parameter into the secondary evaluation module for comprehensive judgment.

[0091] The stability coefficient Sta is jointly constructed from the standard deviation of the dynamic impedance set Imp and the coefficient of variation of the propagation delay set Del, and is defined as follows:

[0092] ;

[0093] Where σImp and σDel are the standard deviations of Imp and Del, respectively, and μImp and μDel are their mean values; Sta can reflect the dynamic fluctuation of the grounding state and realize the adaptive evaluation of multi-source parameters.

[0094] The alarm set Alm is generated based on a dual-parameter conditional judgment mechanism of the comprehensive safety factor Saf and the grounding performance index Gnd. When Saf is lower than the safety threshold and Gnd exceeds the safety limit, the system generates a valid alarm event. The alarm set Alm uses a logical judgment method to form a binary output result so that the system can realize automatic identification and control response.

[0095] The generation logic of the alarm set Alm is based on a dual-condition triggering mechanism of the comprehensive safety factor Saf and the grounding performance index Gnd, and is defined as follows:

[0096] If Saf < Thr2 and Gnd > Lim, then Alm = {1};

[0097] If Saf ≥ Thr2 and Gnd ≤ Lim, then Alm = {0};

[0098] This mechanism is used to improve the accuracy of alarms and avoid misjudgments based on a single parameter.

[0099] In this embodiment, the present invention establishes a dual-parameter dynamic judgment mechanism centered on the stability coefficient Sta and the comprehensive safety factor Saf, thereby realizing real-time stability analysis and intelligent alarm identification of the grounding state of transmission towers under lightning strikes. Firstly, the stability coefficient Sta is jointly constructed from the statistical fluctuation characteristics of the grounding dynamic impedance set Imp and the propagation delay set Del. By calculating the ratio of their standard deviations to their means, it can comprehensively reflect the degree of dynamic fluctuation and electrical characteristic stability during the lightning strike response process, thus identifying the dynamic imbalance state in the grounding grid system caused by uneven conductivity, sudden changes in contact impedance, or local saturation. The adaptive characteristic of this parameter enables the system to maintain consistent evaluation under different lightning strike intensities, soil conductivity, and climatic conditions, overcoming the shortcomings of traditional fixed thresholds that are difficult to adapt to complex scenarios. Secondly, the introduction of the comprehensive safety factor Saf integrates the time-series changes of the stability coefficient Sta and the grounding performance index Gnd for analysis. Through multi-parameter coupled judgment, it realizes the transformation from static detection to dynamic evaluation, enabling the system to have continuous stability judgment capabilities across time periods and events. Thirdly, the generation of the alarm set Alm is based on a dual-condition triggering mechanism of Saf and Gnd, using logical judgment to form a binary output result. This ensures clear logic and accurate decision-making in the alarm process, avoiding misjudgments or missed alarms caused by fluctuations in a single indicator. Through the above collaborative design, the evaluation system of this invention can achieve highly sensitive grounding anomaly detection and real-time alarm feedback under lightning strike conditions. This not only significantly improves the accuracy of the monitoring system in identifying transient disturbances but also strengthens the system's anti-interference capability under complex climatic and geological conditions. Compared with existing traditional monitoring methods that rely on single-point signal triggering, this invention achieves comprehensive identification of dynamic stability through multi-parameter fusion and adaptive judgment logic, greatly improving alarm accuracy and system response speed. This truly realizes a technological leap from "passive response" to "active early warning" in lightning protection of transmission towers.

[0100] Example 5

[0101] A method for monitoring and assessing the condition of transmission towers under lightning strikes; please refer to [reference needed]. Figure 2 Specifically: the safety control command Cmd is generated by the alarm set Alm. The safety control command Cmd includes three types: current limiting control command, isolation control command, and signal verification command, which are used to realize rapid protection and operation adjustment of the lightning-affected area. After the safety control command Cmd is executed, it triggers the real-time update of the grounding parameter set Par to maintain the consistency between the monitoring system and the field status.

[0102] The method further establishes a joint evaluation mechanism of time and space dimensions. By performing correlation analysis between the set of time-series signal change rates and the set of spatial distances, a multi-dimensional determination of the lightning strike ground potential backflash path is achieved.

[0103] The spatial response evaluation value Res is calculated as follows:

[0104] ;

[0105] Where n is the number of monitoring points.

[0106] The spatial response evaluation value Res and the grounding performance index Gnd together form a multi-dimensional comprehensive evaluation matrix, which is used to generate a comprehensive diagnostic report on lightning strike status, and realize a multi-dimensional visual evaluation of the ground potential backflash path and grounding health status.

[0107] In this embodiment, the present invention achieves dynamic response protection and multi-dimensional visualization diagnosis of transmission towers under lightning strike conditions by introducing a collaborative control and analysis mechanism of safety control command Cmd and spatial response evaluation value Res. Firstly, the safety control command Cmd is automatically generated by the triggering event of the alarm set Alm. The command includes three types of actions: current limiting control, isolation control, and signal verification. It is used to implement immediate protection and operational adjustments to the grounding grid system after a lightning strike anomaly occurs, thereby effectively preventing the spread of lightning energy to upstream lines or adjacent equipment. This mechanism realizes closed-loop management from risk identification to control response, enabling the monitoring system to have dynamic defense capabilities of self-decision-making and self-correction. Secondly, after executing the safety control command Cmd, the system triggers a real-time update of the grounding parameter set Par, enabling the monitoring platform to continuously synchronize with changes in the field status, maintaining consistency between model parameters and physical conditions, and avoiding evaluation deviations caused by delayed updates in traditional monitoring systems. Third, by establishing a joint evaluation mechanism encompassing both temporal and spatial dimensions, the system correlates the set of temporal signal change rates with the set of spatial distances to calculate the spatial response evaluation value Res, reflecting the diffusion characteristics and backflash path distribution of lightning current on the ground surface and in the grounding network. This Res index, together with the grounding performance index Gnd, constitutes a multi-dimensional comprehensive evaluation matrix, enabling a full-dimensional quantitative analysis of lightning backflash paths, grounding energy dissipation efficiency, and the health status of the grounding network.

[0108] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for monitoring and evaluating the state of a power transmission tower under lightning strike, characterized in that: Includes the following steps: S1: Collect the ground potential signal data set Sig of the transmission tower at the moment of lightning strike, and perform time synchronization processing on the signals of each monitoring point to obtain the ground potential change time series set Tim; S2: Calculate the propagation delay set Del between each monitoring point based on the ground potential change time series set Tim, and establish a propagation characteristic model by combining the geometric distance set Geo from the tower to the grounding body, generating the propagation characteristic distance set Dis; The calculation of the propagation characteristic distance set Dis includes the construction of the propagation model equation and the environmental correction steps. The propagation model equation takes the surface propagation velocity constant, soil moisture correction factor and ground resistance non-uniformity coefficient as parameters as input, and comprehensively corrects the diffusion characteristics of lightning current on the surface under different geological conditions through multi-parameter correlation modeling. In the process of calculating the propagation feature distance set Dis, the system first extracts the geometric distance set Geo based on the tower foundation structure, grounding electrode shape and geological layer thickness information, and performs matching mapping with the propagation delay set Del, thereby establishing the correspondence between "time difference and spatial propagation". The calculation of the propagation feature distance set Dis includes the propagation model equations: ； Where c is the surface lightning current propagation velocity constant, α is the soil moisture correction factor, and k is the ground resistance non-uniformity coefficient; through the above propagation model equation, the lightning propagation effect under different geological environments can be compensated differently. S3: Compare the propagation characteristic distance set Dis with the preset reference propagation characteristic distance set Ref, calculate the deviation ratio set Rat, and when the deviation ratio set Rat exceeds the threshold Thr, determine that there is an abnormality in the grounding performance and obtain the grounding dynamic impedance set Imp; The solution of the grounding dynamic impedance set Imp is based on the joint characteristic analysis of the ground potential change signal and the lightning current signal. By inversely deducing the difference in the response time of the two, the dynamic electrical impedance change at the moment of lightning strike is obtained. Furthermore, the calculation process of the grounding dynamic impedance set Imp comprehensively considers the soil dielectric constant, contact resistance, and signal steepness factor, which is used to reflect the energy discharge capacity and transient conduction performance of the grounding system under lightning strike. The solution for the grounding dynamic impedance set Imp is obtained using the impedance inverse function Fun, which is defined as follows: ； Where ΔV is the amplitude of the ground potential change at the moment of lightning strike, ΔI is the amplitude of the lightning current change, β is the soil dielectric adjustment coefficient, and η is the signal steepness factor; the impedance disturbance degree of the lightning wave propagating in the ground grid structure can be quantified through this function Fun. S4: The grounding performance index Gnd is calculated based on the grounding dynamic impedance set Imp and the ground potential change energy set Ene, which is used to characterize the discharge capacity of the grounding body under lightning strike; The grounding performance index Gnd is determined by the changing trends of the grounding dynamic impedance set Imp and the ground potential change energy set Ene, and is used to characterize the energy absorption and discharge characteristics of the grounding system under lightning strikes. The grounding performance index Gnd is used to conduct a health assessment of the grounding state after a lightning strike, and its numerical change can reflect the conductivity of the grounding body and the intensity of ground potential backflash. The grounding performance index Gnd is calculated using the following formula: ； Where Imp is the mean of the set of grounding dynamic impedances, Ene is the integral result of the set of ground potential change energy, Ref is the median of the set of reference propagation characteristic distances, and Gnd is used to comprehensively reflect the energy absorption and discharge efficiency during lightning strikes. The smaller its value, the healthier the grounding system. S5: Compare the grounding performance index Gnd with the historical standard performance index set Std. If the deviation exceeds the safety limit Lim, generate an alarm set Alm and output the safety control command Cmd to the monitoring system.

2. The method for monitoring and evaluating the state of a power transmission tower under lightning strike according to claim 1, characterized in that: The ground potential signal data set Sig is preprocessed by a time filter function Flt during the acquisition process to eliminate high-frequency noise, inductive coupling interference, and waveform distortion caused by transient eddy currents from lightning strikes, thereby improving the time-domain continuity and voltage change accuracy of the signal. The time filter function Flt dynamically adjusts the sampling interval using a sliding window method during processing to adapt to the characteristics of ground potential signals at different sampling frequencies. By smoothing the variance difference between the instantaneous value ti and the interval mean μ of each sampling interval, abnormal abrupt changes are suppressed.

3. The method for monitoring and evaluating the condition of transmission towers under lightning strikes according to claim 1, characterized in that: The grounding performance index Gnd is subjected to a graded analysis to establish a two-layer safety judgment mechanism of primary assessment and secondary assessment. The primary assessment determines the primary risk level set Lev1 based on the comparison results between the grounding performance index Gnd and the safety limit Lim. The secondary assessment calculates the stability coefficient Sta and forms a comprehensive safety factor Saf based on the changing trends of the dynamic impedance set Imp and the propagation delay set Del, which is used to reflect the overall stability of the grounding grid system under different lightning strike intensities.

4. The method for monitoring and evaluating the condition of transmission towers under lightning strikes according to claim 3, characterized in that: The stability coefficient Sta is determined by the statistical fluctuations of the grounding dynamic impedance set Imp and the propagation delay set Del. The stability of the lightning response process is characterized by analyzing the ratio of its standard deviation to its mean. When the stability coefficient Sta exceeds the preset threshold, the system determines that there is a risk of dynamic imbalance in the grounding state and inputs this risk parameter into the secondary evaluation module for comprehensive judgment.

5. The method for monitoring and evaluating the condition of transmission towers under lightning strikes according to claim 1, characterized in that: The alarm set Alm is generated based on a dual-parameter conditional judgment mechanism of the comprehensive safety factor Saf and the grounding performance index Gnd. When Saf is lower than the safety threshold and Gnd exceeds the safety limit, the system generates a valid alarm event. The alarm set Alm uses a logical judgment method to form a binary output result so that the system can realize automatic identification and control response.

6. The method for monitoring and evaluating the condition of transmission towers under lightning strikes according to claim 1, characterized in that: The safety control command Cmd is generated by the alarm set Alm. The safety control command Cmd includes three types: current limiting control command, isolation control command, and signal verification command. It is used to realize rapid protection and operation adjustment of the lightning-affected area. After the safety control command Cmd is executed, it triggers the real-time update of the grounding parameter set Par to maintain the consistency between the monitoring system and the field status.

7. The method for monitoring and evaluating the condition of transmission towers under lightning strikes according to claim 1, characterized in that: The method further establishes a joint evaluation mechanism of time and space dimensions. By performing correlation analysis between the set of time-series signal change rates and the set of spatial distances, a multi-dimensional determination of the lightning strike ground potential backflash path is achieved. The spatial response assessment value Res and the grounding performance index Gnd together form a multi-dimensional comprehensive assessment matrix, which is used to generate a comprehensive diagnostic report on lightning strike status, enabling a multi-dimensional visual assessment of the ground potential backflash path and grounding health status.

Images