Wind deflection gap safety evaluation method for power transmission line in strong wind area

Abstract

The invention provides a windage yaw gap safety evaluation method for a power transmission line in a strong wind area, and belongs to the technical field of power transmission line wind damage prevention and control. According to the technical scheme, firstly, a high-altitude power transmission line wind field actual measurement system is established, strong wind characteristics are actually measured, then, a non-rigid finite element model of an overhead power transmission line insulator string wind deflection analysis model is established, wind deflection characteristics are analyzed, finally, the applicability of two wind deflection prevention measures is calculated and analyzed, and optimization and improvement measures are put forward. The method can be used for calculation of windage yaw prevention and insulation gaps in high-voltage transmission lines in high-altitude areas such as Qinghai, Haibei and the like, so that an objective safety evaluation conclusion is obtained, improvement of an engineering structure is guided, and the method has high engineering application value.

Description

Technical Field

[0001] The invention belongs to the technical field of wind damage prevention and control for power transmission lines, and specifically relates to a windage clearance safety assessment method for power transmission lines in strong wind areas. Background Art

[0002] As the main carrier of electric energy transmission in power grid construction, how to ensure the normal and stable operation of overhead transmission lines has become an important scientific research topic. Strong winds have brought great harm to the safe operation of transmission lines. Taking Haibei Prefecture in Qinghai Province as an example, it is located in the northeast of Qinghai Province, the northeast of the Qinghai-Tibet Plateau, and the western edge of the Loess Plateau. It has a plateau continental climate, with a long cold period, a short warm and cool period, sufficient sunlight, strong solar radiation, distinct dry and wet seasons, rain and heat in the same season, and frequent night rains and strong winds. Overhead transmission lines in this area often suffer from wind damage failures.

[0003] The occurrence of wind damage accidents caused by strong winds is not only reflected in the increase of stress on overhead lines and the destruction of the structural strength of the lines, but also in the large-scale displacement of live conductors, resulting in insufficient electrical safety clearance. Among many wind damage accidents, wind deflection flashover accidents of overhead lines have the characteristics of wide existence, high frequency of occurrence, and great harm. They are the main reason for line shutdown under strong wind weather and are also the focus of many scholars and designers. The wind field characteristics of the atmospheric boundary layer are the basic factors and necessary conditions for determining the wind load borne by the structure. Through on-site measurement methods, the wind speed and direction of the actual wind field can be directly captured, which is the most direct and effective method to study the characteristics of wind loads. At present, scholars generally believe that the main reason for the increase in wind deflection flashover accidents is the inapplicability of the insulator pendulum model in the code calculation and the unreasonable selection of wind loads. Therefore, a large number of literatures have revised the calculation formula of wind deflection codes based on the analysis results. However, existing studies are generally based on the rigid straight rod theory of insulators, assuming that insulators do not bend and deform during wind deflection. The simulation of wind loads is also based on a well-conditioned wind field, without considering the actual environment of Qinghai's high altitude. As a result, the adopted wind deflection prevention measures did not achieve good results.

[0004] Windage gap refers to the deviation of the insulator string under the action of wind, which causes the air gap between the live body and the tower structure to decrease. Insufficient windage gap is one of the main causes of windage tripping accidents. When the windage angle is too large, the air gap between the live body at the lower end of the insulator string and the tower decreases. If the electrical strength of this gap cannot withstand the system operating voltage, discharge will occur, causing tripping. The size of the windage gap is affected by many factors, including wind speed, wind pressure unevenness coefficient, wind pressure height variation coefficient, vertical span, etc. In addition, the weight of the insulator string also affects the size of the windage gap to a certain extent.

[0005] In the design of transmission lines, windage clearance is an important consideration. During the design, the minimum allowable clearance distance between the conductor and the ground and each object to be crossed needs to be determined according to the requirements of internal overvoltage and external overvoltage. For EHV and UHV lines, the influence of the ground electrostatic field strength also needs to be considered. Through reasonable design and measures, the occurrence of windage flashover accidents can be effectively prevented to ensure the safe operation of transmission lines. Summary of the invention

[0006] The technical problem to be solved by the present invention is: how to achieve a safe assessment of the windage clearance of a transmission line, and then optimize the strong wind resistance performance of typical components.

[0007] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0008] A windage clearance safety assessment method for a power transmission line in a high wind area comprises the following steps:

[0009] 1) Establish a wind speed measurement system on the transmission line tower and calculate the wind field characteristic parameters based on the measured results;

[0010] 2) Construct a tower-line system model, calculate the wind deviation of the transmission line, and analyze the impact of wind deviation on the insulator string of the overhead transmission line.

[0011] Preferably, the wind speed measurement system in step 1) includes a wind speed and direction sensor, a meteorological environment monitoring unit, a data processing and substation scheduling unit, a wireless communication module, and a power supply system; the wind speed measurement system collects real-time data through the wind speed and direction sensor, and the meteorological environment monitoring unit converts the collected data into an electrical signal, and the data processing and substation scheduling unit performs standardized processing on the data, and receives instructions from the main station to decompose and execute them; the wireless communication module sends the data to the substation switch via Ethernet, and the switch transmits the data to the computing, analysis and monitoring center through the communication network; the computing, analysis and monitoring center stores and analyzes the data.

[0012] Preferably, the wind speed and direction sensor is a cup anemometer or an ultrasonic anemometer; the sampling frequency of the cup anemometer is 1 Hz, and it is installed facing due north. The wind direction angle reading increases in a clockwise direction when viewed from above, with north wind as 0 degrees and east wind as 90 degrees; the sampling frequency of the ultrasonic anemometer is 4 Hz.

[0013] Preferably, the wind speed and direction sensor includes a data acquisition instrument, which processes wind speed and direction data in real time, integrates a 4G communication module, sets the central IP, port number and communication method through serial port instructions, and then uses wireless communication to upload the collected data to the cloud server according to the time period set by the user.

[0014] Preferably, the wind field characteristic parameters in step 1) include average wind speed, average wind direction, gust factor, turbulence intensity, turbulence integral scale, and wind speed power spectrum.

[0015] As a preferred method, the downwind calculation formula of turbulence intensity is as follows:

[0016]

[0017] The crosswind direction calculation formula of turbulence intensity is as follows:

[0018]

[0019] The downwind calculation formula of the gust factor is as follows:

[0020]

[0021] The crosswind direction calculation formula of the gust factor is as follows:

[0022]

[0023] The downwind calculation formula of the turbulence integral scale is as follows:

[0024]

[0025] The crosswind direction calculation formula of the turbulence integral scale is as follows:

[0026]

[0027] Preferably, in step 2), in the process of constructing the tower-line system model, the load simulation includes gravity load, concentrated force load, wind load, and ice load, wherein the wind load includes a stable wind load and a random wind load;

[0028] The calculation formula for the conductor wind load is:

[0029]

[0030] In the formula, α, μ sc , d, β c ,δ,l H , μ z , θ, and V represent wind pressure unevenness coefficient, conductor body type number, conductor outer diameter, load adjustment coefficient, ice thickness, horizontal span, wind pressure height coefficient, wind direction angle, and basic design wind speed, respectively;

[0031] V is the steady wind speed; the steady wind load is applied by inputting the reference wind speed, ice thickness and wind direction angle;

[0032] Before applying the random wind load, the random wind is simulated first. The downwind time history curve of the wind includes two parts: average wind and fluctuating wind v(t). The fluctuating wind is randomly simulated through the wind power spectrum. The calculation formula of the fluctuating wind is as follows:

[0033]

[0034] The harmonic superposition method is used to simulate the pulsating wind field.

[0035] Preferably, in step 2), in the process of calculating the windage of the transmission line, the masses of the insulators, spacers and fittings in the line are known, and the calculation formula of the gravity load G is as follows:

[0036] G=G0+nlq

[0037] Where: G0 is the mass of the insulator string and hardware, n is the number of conductor splits, l is the conductor span, and q is the gravity distribution per unit length of the conductor;

[0038] The rigid straight rod method is used to calculate the wind deflection angle of the suspension insulator string; the calculation formula for the wind deflection angle under wind load and gravity load is as follows:

[0039]

[0040] W x =0.5W x左 +0.5W x右

[0041] W x =Pl H

[0042] G c =G w l H +qT

[0043] Where, Wx is the equivalent wind load on the conductors on both sides, Gc is the equivalent gravity of the conductors on both sides, Wl is the self-generated wind load of the insulator string, Gl is the gravity load of the insulator string itself, lH is the horizontal span of the conductor, P is the wind load acting on the unit length of the conductor, Gw is the gravity per unit length of the conductor, T is the horizontal tension of the conductor, q is the height difference coefficient, when the height difference is 0, Gc is independent of the conductor tension T.

[0044] Preferably, step 2) analyzes the effect of wind deflection on insulator strings of overhead transmission lines, comprising: adjusting the size of static wind and pulsating wind, setting different working conditions for wind speed impact analysis; inputting the data of pulsating wind working conditions into the program, establishing the left and right span range and interval of the transmission line according to the line span of the actual line, selecting the actual working conditions, applying static wind and pulsating wind with average wind speeds of 15m / s, 20m / s, and 25m / s to its diagonal for wind deflection response analysis, and the wind field duration is 10min to obtain the statistical results of the respective wind deflection angles; establishing a two-span 400m conductor model, with an average pulsating wind speed of 25m / s, setting different attack angles, and performing wind deflection response analysis.

[0045] Preferably, the method further comprises the following step 3): optimizing the wind-resistant structure of the transmission line components; in the process of the optimization, simulating the connection mode of hard-connected and soft-connected jumper strings of different tower shapes, simulating the arrangement mode and fatigue stress of bird-proof spikes on the top of the tower under strong wind conditions, simulating the stress characteristics of the bird-proof umbrella or grading ring of the insulator string in strong wind areas, and simulating the influence of bird-proof covers and bird-proof spikes on the electric field distribution and insulation performance under strong wind conditions.

[0046] The present invention provides a method for evaluating the wind deflection clearance safety of power transmission lines in high-wind areas. The technical solution first establishes a wind field measurement system for high-altitude transmission lines to perform actual measurements of strong wind characteristics, then establishes a non-rigid finite element model for the wind deflection analysis model of the insulator string of the overhead transmission line, analyzes the wind deflection characteristics, and finally calculates and analyzes the applicability of two wind deflection prevention measures and proposes optimization and improvement measures. The present invention can be used for the calculation of wind deflection prevention and insulation clearance in high-voltage transmission lines in high-altitude areas such as Haibei, Qinghai, so as to obtain objective safety evaluation conclusions, and then guide the improvement of engineering structures, and has high engineering application value.

[0047] The technical advantages of the present invention are mainly reflected in the following aspects:

[0048] (1) Strong wind field characteristics of transmission lines

[0049] A wind speed measurement system is established on the transmission line towers in strong wind areas, and a measured study is conducted on wind fields in high altitude areas. The measured wind speed records are used as the research object, and the stable and Gaussian characteristics of strong wind records in wind fields are studied. The turbulent characteristics of the two types of wind fields, the evolution spectrum characteristics, the gust factor and other wind field elements are analyzed to provide measured data and theoretical basis support for subsequent wind deflection prevention measures, strong wind area renovation, and new project design.

[0050] (2) Characteristics of wind deflection effects on insulator strings of overhead transmission lines

[0051] By analyzing the empirical calculation method of the typical wind deflection of insulator strings of 110kV transmission lines, a tower-line system model was established, and numerical wind speed was simulated using Matlab to generate wind loads. The empirical calculation method of wind deflection of transmission lines, static wind simulation and dynamic wind simulation were compared and analyzed, and suggestions for improving the wind deflection calculation formula were proposed. Combined with the power frequency flashover test results of conductors and towers in high-altitude areas and the measured results of wind characteristics, the influence of pulsating wind speed, span, insulator string length and wind attack angle on the wind deflection of insulator strings was analyzed, and correction coefficients and correction suggestions under high-altitude conditions were proposed to provide a basis for improving the accuracy of wind deflection of insulator strings.

[0052] (3) Optimization of typical components of transmission lines against strong winds

[0053] Aiming at the common faults of transmission lines in windy areas, the connection methods of hard-connected and soft-connected jumper strings of different tower shapes are simulated and optimized; the layout of bird-proof spikes on the top of the tower and fatigue stress under strong wind conditions are simulated and analyzed, and optimization measures are studied; the stress characteristics of bird-proof umbrellas or grading rings of insulator strings in windy areas are simulated and optimized; the influence of bird-proof covers and bird-proof spikes on the electric field distribution and insulation performance in strong wind environments is simulated and optimized. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is a schematic diagram of the wind speed measurement system in the present invention.

[0055] Figure 2 It is a force analysis diagram of the rigid straight rod method in the present invention.

[0056] Figure 3 It is a schematic diagram of a simulation model of a bird-proof cover in the present invention. DETAILED DESCRIPTION

[0057] The specific embodiments of the present invention will be described in detail below. In order to avoid too much unnecessary details, the well-known structures or functions will not be described in detail in the following examples. The approximate language used in the following examples can be used for quantitative expression, indicating that the quantity can be allowed to have a certain change without changing the basic function. Unless otherwise defined, the technical and scientific terms used in the following examples have the same meaning as those generally understood by those skilled in the art to which the present invention belongs.

[0058] 1. Characteristics of strong wind field of power transmission lines in Haibei area

[0059] Regarding the strong wind field characteristics of the transmission lines in Haibei area, we first established a wind speed measurement system on the transmission line towers in the strong wind area of ​​Haibei area, and conducted a measured study on the wind field in Haibei area. Taking the measured wind speed records as the research object, we studied the steady characteristics and Gaussian characteristics of the strong wind records in the wind field, analyzed the turbulence characteristics of the two types of wind fields, the evolution spectrum characteristics, the gust factor and other wind field elements, and provided measured data support for subsequent wind deviation prevention measures.

[0060] (1) Construction of wind speed measurement system and data processing

[0061] The wind speed measurement system is an intelligent large-scale remote distributed monitoring system, which consists of several automatic meteorological instruments. It can monitor ground rainfall, air temperature and humidity, and can also measure wind speed and wind direction. It is a new type of fully automatic meteorological observation equipment. The measurement system consists of wind speed and direction sensors, meteorological environment monitoring devices, data analysis systems, substation scheduling, communication modules, power supply systems and other units. The system collects real-time data through sensors, and the meteorological environment monitoring unit converts the collected data into electricity. Through data processing and substation scheduling units, data is standardized and instructions from the main station are received and decomposed and executed; the wireless communication module sends the data to the substation switch via Ethernet, and the switch transmits it to the calculation analysis monitoring center through the power dedicated communication network. The calculation analysis monitoring center stores and analyzes the data to provide data support for the study of the basic characteristics of the wind farm.

[0062] The mechanical anemometer is a cup type with a sampling frequency of 1Hz. The wind vane is installed facing due north. The wind direction angle reading increases clockwise from the top, with north wind as 0 degrees and east wind as 90 degrees. The ultrasonic anemometer has higher accuracy and a sampling frequency of 4Hz. The data acquisition instrument can process wind speed and direction data in real time. It integrates a 4G communication module. After setting the center IP, port number and communication method through serial port instructions, it uses wireless communication to upload the collected data to the cloud server according to the user-set time period. Users can remotely monitor real-time data through the background server, understand data trends, query, review, and display historical data in graphics, etc. At the same time, a 50W solar panel is used to power the equipment, and a 38Ah battery is added to ensure that the sensor equipment can work normally under 30 consecutive days of no sunshine. Figure 1 Schematic diagram of the measured system.

[0063] According to the topographical features of the Haibei area and combined with the basic meteorological observation data of Qinghai provided by the National Meteorological Science Data Center, the actual installation location of the wind speed measurement system on the transmission line tower was determined.

[0064] The real-time wind speed and direction data collected by the ultrasonic anemometer will be temporarily stored locally, and then wirelessly transmitted to the backend server via the 4G router using the mobile communication network; the conductor tension monitoring includes two sets of horizontal tension sensors and two sets of vertical tension sensors. The data of the horizontal tension sensor is transmitted to the data storage station via a wireless transceiver, and the vertical tension sensor is directly transmitted to the data storage station via the 485 bus to USB. The data storage station is managed by an industrial computer, which accesses the Internet via a 4G router and can remotely operate the on-site industrial computer through the local server. Solar panels and batteries provide power for the transmission tower line monitoring system.

[0065] Since the equipment is in long-term outdoor work and collection, the sensor is easily affected by the external environment such as lightning, electromagnetism, rain, etc., which may cause extreme abnormal values ​​in some measured data or interruption of data collection and transmission. In order to reduce the impact of abnormal data and system errors, the measured data should be preprocessed before research and analysis to ensure the validity of the measured data.

[0066] When checking the measured data, due to signal loss or instrument failure during data transmission, some data may be lost for a period of time, resulting in time discontinuity; at the same time, due to the instability of signal transmission or the anemometer's own failure, a series of fixed values ​​may appear, which are called "rigid points"; in addition, accidental errors in instrument measurement or errors in data transmission decoding may cause some abnormal data, which are called "wild points". Packet loss, rigid points, wild points, etc. are all very easy to occur in the actual measurement process, so these data need to be judged and processed.

[0067] For the determination of wild points, the commonly used method is the Lysundar criterion, and its specific implementation steps are as follows:

[0068] 1) For the nth data, calculate the mean of the 5 numbers before and after it;

[0069] 2) Calculate the variance of the 5 data before and after the point;

[0070] 3) Judgment: Data that do not meet 5W root mean squares near the mean are judged as outliers, and w can generally be 5.

[0071] (2) Basic elements of wind farm

[0072] The basic characteristics of the wind field mainly include average wind speed, average wind direction, turbulence intensity, turbulence integral scale, wind speed power spectrum, etc. The calculation formulas for the steady state characteristics and Gaussian characteristics in strong winds are listed in Table 1.

[0073] Table 1 Calculation formula for basic turbulence characteristics of wind field

[0074]

[0075] Turbulence intensity is an important parameter that characterizes wind speed fluctuations and is mainly affected by surface roughness and height above the ground. IEC61400-1 provides an inverse proportional relationship model between turbulence intensity and average wind speed:

[0076]

[0077] The ratio of the turbulence intensity in the crosswind direction to that in the downwind direction is approximately equal to I v :I u =0.75.

[0078] The gust factor is used to calculate the conversion ratio between the average wind speed peaks at different time intervals, usually the ratio of the short-time interval to the long-time interval average wind speed. The short time interval is 3s, and the long time interval is 10 minutes, which is the design wind speed adopted in my country.

[0079] Both turbulence intensity and gust factor characterize the pulsation intensity of turbulent wind, and the two are not completely independent.

[0080] The turbulence integral scale characterizes the average size of turbulent vortices in the airflow. The turbulence integral scale also reflects the intensity of the turbulence effect. The larger the turbulence integral scale, the more significant the turbulence effect.

[0081] The ratio of the turbulence integral scales along the wind to across the wind, the average value is approximately equal to L u :L v =1:0.85.

[0082] The vonKarman spectrum is a spectral model based on classical turbulence theory. It is used to describe the three-dimensional energy spectrum distribution characteristics of isotropic turbulence. It has a clear physical background in the low-frequency region and the inertial sub-region, and conforms to the fourth power law of the wave number in the low-frequency large eddy range and the "-5 / 3" curtain law in the inertial sub-region. In many field studies, vonKarman is considered to be the most reliable spectral model currently available for describing the distribution of fluctuating wind speed energy spectrum, and has been included as a standard form of fluctuating wind speed energy spectrum distribution by internationally authoritative engineering science data organizations. The specific form of the vonKarman spectrum is:

[0083]

[0084]

[0085] The vonKarman spectrum model reflects the law of change of turbulent energy with frequency. The model uses the turbulence integral scale as a parameter to characterize the influence of vortex scale on the energy distribution of the wind field end flow. For the fluctuating wind speed obtained by the non-steady wind speed model, establishing a suitable vonKarman spectrum model involves accurately calculating the end flow integral scale of the wind field. Calculate the turbulence integral scale of the non-steady wind speed model, substitute the result into the vonKarman spectrum model, and compare the spectral deviation between the measured wind speed spectrum and the vonKarman wind speed spectrum to determine a more reasonable method for calculating the longitudinal turbulence integral scale.

[0086]

[0087] 2. Characteristics of wind deflection effects on insulator strings of overhead transmission lines

[0088] Wind deflection is the phenomenon that overhead transmission lines deviate from their vertical position under wind load. Excessive wind deflection can cause flashover and line tripping, which not only threatens the safe operation of the power grid but also causes significant economic losses. Studying and accurately calculating the wind deflection of conductors has become an urgent need for the normal operation of the power grid.

[0089] The present invention analyzes the empirical calculation method of the typical insulator string type wind deflection of 110kV transmission lines, establishes a tower-line system model, uses Matlab to simulate numerical wind speed, generates wind load, performs comparative analysis of the empirical calculation method of wind deflection of transmission lines, static wind simulation and dynamic wind simulation, and proposes improvement suggestions for wind deflection calculation formulas. Combined with the power frequency flashover test results of conductors and towers in high-altitude areas and the measured results of wind characteristics, the influence of pulsating wind speed, span, insulator string length and wind attack angle on the wind deflection of insulator strings is analyzed, and correction coefficients and correction suggestions under high-altitude conditions are proposed to provide a reference for improving the accuracy of wind deflection of insulator strings.

[0090] (1) Construction and simulation of tower-line system model

[0091] In the study of transmission lines, the catenary model is often used to simplify the analysis. The model assumes that the conductor is suspended in the air like a soft chain. Under this assumption, the rigidity of the conductor has little effect on the geometry due to the large distance between the suspension points. Based on this assumption, it can be concluded that the conductor can only withstand axial tension, but not bending moments. Furthermore, it is assumed that the loads on the conductor are all directed in the same direction and are evenly distributed along the length of the wire. These basic assumptions form the basis of the catenary formula.

[0092] Insulator strings are usually used to support conductors and ensure proper insulation spacing between conductors and poles. Tension towers usually use tension insulator strings, while straight towers use suspension insulator strings. The design of suspension insulator strings includes two types: I-type and V-type. Their purpose is to achieve good electrical insulation performance in power transmission systems. In order to simplify the structure of the overall model, the suspension insulator string unit is simplified to a pole unit.

[0093] Load simulation mainly includes gravity load, concentrated force load, wind load and ice load, among which wind load is divided into stable wind load and random wind load.

[0094] The calculation formula for the conductor wind load is:

[0095]

[0096] In the formula, α, μ sc , d, β c ,δ,l H , μ z , θ, and V represent the wind pressure unevenness coefficient, conductor type number, conductor outer diameter, load adjustment coefficient, ice thickness, horizontal span, wind pressure height coefficient, wind direction angle, and basic design wind speed, respectively.

[0097] V is the steady wind speed, and the load is the steady wind load. The steady wind load is applied by inputting the corresponding reference wind speed, ice thickness and wind direction angle.

[0098] Before applying random wind loads, random wind needs to be simulated first. The wind downwind time history curve generally contains two parts: average wind and fluctuating wind v(t). Steady wind can be obtained from the specification, while fluctuating wind needs to be randomly simulated through wind power spectrum. The calculation formula for fluctuating wind is as follows:

[0099]

[0100] The fluctuating wind speed can be treated as a Gaussian stationary random process with zero mean, that is, its statistical characteristics are equal everywhere and do not depend on the choice of the time origin, and the wind speed spectrum obeys the normal distribution. Since the fluctuating wind speed itself can be expressed by a Gaussian stationary random process with zero mean and has obvious ergodicity, the power spectrum density function is its most important statistical feature, reflecting the energy of the fluctuating wind in a certain frequency domain.

[0101] Commonly used numerical simulation methods for pulsating wind fields are harmonic superposition method and linear filter method. The linear filter method has high calculation accuracy, but the theory is relatively complex and the selection of calculation parameters is difficult. In contrast, the harmonic superposition method has clear theory, but the amount of calculation is relatively large. However, with the rapid development of computer hardware and the improvement of computing power, the impact of the amount of calculation on the calculation speed has gradually decreased. In addition, the harmonic superposition method can also reduce the computational complexity through fast Fourier transform. Therefore, the harmonic superposition method is chosen to simulate the pulsating wind field.

[0102] (2) Calculation of windage deviation of transmission lines

[0103] The masses of insulators, spacers and fittings in the line are all known, so only the gravity load of the conductor needs to be calculated. From the specification, it can be known that the calculation formula for the gravity load G of the transmission line is as follows:

[0104] G=G0+nlq

[0105] Where: G0 is the mass of the insulator string and hardware, n is the number of conductor splits, l is the conductor span, and q is the gravity distribution per unit length of the conductor.

[0106] There are two main methods for calculating the wind deflection angle of an insulator string: the rigid straight rod method and the chord polygon method. Since the chord polygon method is more complicated to calculate, the rigid straight rod method is used to calculate the wind deflection angle of a suspension insulator string. The rigid straight rod method regards the insulator string as a straight rod with infinite rigidity, the upper end of which is hinged to the tower, and the lower end connected to the conductor can swing freely. The schematic diagram is shown in the figure. Figure 2 The gravity load and wind load on the transmission line are simplified to concentrated loads, acting on the free end of the rigid straight rod, and the gravity load and wind load of the insulator string itself act on the center of the insulator string. This method can be used to calculate the maximum deflection angle of the insulator string under wind load, thereby determining its wind deflection size.

[0107] According to the force balance, the calculation formula of wind deflection angle under wind load and gravity load is as follows:

[0108]

[0109] W x =0.5W x左 +0.5W x右

[0110] W x =Pl H

[0111] G c =G w l H +qT

[0112] Where, Wx is the equivalent wind load on the conductors on both sides, Gc is the equivalent gravity of the conductors on both sides, Wl is the self-generated wind load of the insulator string, Gl is the gravity load of the insulator string itself, lH is the horizontal span of the conductor, P is the wind load acting on the unit length of the conductor, Gw is the gravity per unit length of the conductor, T is the horizontal tension of the conductor, q is the height difference coefficient, when the height difference is 0, Gc is independent of the conductor tension T.

[0113] (3) Characteristics of wind deflection effects on insulator strings of overhead transmission lines

[0114] By adjusting the size of static wind and pulsating wind, different working conditions are set to analyze the impact of wind speed. The data of pulsating wind working conditions are input into the program to analyze the wind deviation response.

[0115] According to the line span statistics table of the actual line, the left and right span range and interval of the transmission line are established with the actual line as a reference. Representative working conditions are selected to cover the common span conditions in the actual line, while considering some rare but possible extreme conditions. The wind deviation response analysis is carried out by applying static wind and pulsating wind with average wind speeds of 15m / s, 20m / s, and 25m / s to the diagonal of the above working conditions. The wind field duration is 10 minutes, and the respective wind deviation angle statistics are obtained.

[0116] A two-gap 400m conductor model was established. The average wind speed of the pulsating wind was 25m / s. Different attack angles were set and the wind deviation response analysis was carried out.

[0117] 3. Optimization of strong wind resistance for typical components of power transmission lines

[0118] Aiming at the common faults of power transmission lines in the windy areas of Haibei region, the present invention simulates and optimizes the connection mode of jumper strings; simulates and analyzes the stress characteristics of bird-proof umbrellas or grading rings of insulator strings in windy areas, and optimizes the stress characteristics of bird-proof umbrellas or grading rings.

[0119] The jumper of the transmission line is taken as the research object. The finite element models of two jumpers (with and without suspended insulator strings) are established by finite element simulation software. The wind vibration response of the jumper is analyzed by time domain finite element analysis method, and the wind deflection characteristics of the jumper and the suppression effect of the wind deflection of the jumper by adding insulator strings are studied. Based on the constructed jumper finite element model, the vibration response of the jumper under wind load is analyzed, that is, transient dynamic analysis is performed. Transient dynamic analysis, also known as time history analysis, is a method for solving the dynamic response of the structure, and its excitation force is any load that changes with time. The load on the jumper of the transmission line is mainly wind load, which can be divided into two parts: average wind and pulsating wind. The average wind part can be simulated according to the exponential function, and the pulsating wind part can be simulated by the power spectrum function. Based on the autoregressive model in the linear filtering method, the wind speed time history curve of the horizontal pulsating wind is simulated and generated by MATLAB. The reference height of the jumper is taken as 30m from the ground, the average wind speed v acting on the jumper is 33.6m / s, the wind speed power spectrum S takes the Davenport spectrum, and the cut-off frequency w=6Hz; according to the calculation formula of the wind load acting on the conductor, the simulated wind speed time history curve is converted into a wind load time history curve, and the corresponding wind load is applied to the finite element model of the jumper. The finite element analysis is carried out on the wind vibration response of the jumper under different wind speeds, different wind directions and with or without the installation of a suspension insulator string, so as to obtain the wind deflection characteristics of the jumper under different conditions, better propose optimization measures, and conduct electrical and mechanical performance analysis on the optimized jumper string to detect the rationality of the optimization measures.

[0120] Since the length of the bird-proof needles is short and there is no sag similar to that of the ground wire, it is impossible to refer to the wind load calculation method of the ground wire. Therefore, the wind load standard value of the insulator string is used for calculation. According to the commonly used bird-proof needle lengths, 700mm, 600mm and 500mm needles are taken to calculate the wind load. The coefficient of wind pressure variation with ground height is taken according to the ground roughness according to the actual environmental conditions, and the wind load of needles of different lengths at a reference wind speed of 35m / s is calculated. According to the calculated wind load and the mass of different bird spikes, the wind load is simulated by applying gravity acceleration. The equivalent acceleration can be obtained by dividing the wind load by the weight of the needles, thereby obtaining the gravity acceleration equivalent to the force of the wind load applied to needles of different lengths and diameters. In the simulation, gravity is directly changed to equivalent acceleration to simulate the force of the needles in strong winds. The bird thorn model was established using Solidworks. Since the wind direction would blow vertically toward the bird thorn, one end of the bird thorn was fixed during the simulation, and the wind load equivalent gravity acceleration was applied to the bird thorn to observe whether the needles made of different materials would yield. If the maximum force on the needle exceeds the yield strength of a certain material, it is considered that it is not suitable as a needle material. A similar simulation method was used to obtain the results of whether needles of different materials with different diameters and lengths would yield when encountering a wind speed of 35m / s. Based on the above results, the best material for anti-bird thorns was determined and improved.

[0121] In order to study the wind resistance of silicone rubber bird shield, the CFX module in finite element simulation software ANSYS Workbench was used to simulate and analyze the flow field around it. According to the on-site application conditions and relevant regulations, the diameters of silicone rubber bird shields for 110, 220, and 330KV transmission lines were set to 400, 450, and 500mm, respectively. The schematic diagram of the bird shield simulation model is shown in Figure 2. Figure 3 shown.

[0122] According to the actual situation on site, the inlet wind speed of the flow field is specified, and the simulation operation is performed to obtain the streamline distribution diagram of bird-proof covers and composite insulators of different voltage levels. According to the flow field distribution diagram, the wind pressure around the bird-proof cover and the shed and the bending deformation effect on the shed are judged, so as to optimize the design of the bird-proof cover, and install the optimized bird-proof cover between the insulator string and the crossarm, which meets the bird-proof function and has sufficient wind resistance and rigidity, but will affect the electric field distribution at the low-voltage end of the insulator string. In order to analyze the degree of influence, the spatial electric field near the insulator of the line insulator string after the new silicone rubber bird-proof cover is installed is simulated, and compared with the bird-proof spikes (bird-proof shed) without bird-proof spikes (bird-proof shed) and the bird-proof spikes (bird-proof shed) with the standard number of bird-proof spikes (bird-proof shed), so as to obtain the optimal solution for high altitude and micro-topography.

[0123] The embodiments of the present invention are described in detail above, but the contents are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the scope of the present invention shall be included in the protection scope of the present invention.

Claims

1. A windage clearance safety assessment method for power transmission lines in high wind areas, characterized in that: The following steps are involved: 1) Establish a wind speed measurement system on the transmission line tower and calculate the wind field characteristic parameters based on the measured results; 2) Construct a tower-line system model, calculate the wind deviation of the transmission line, and analyze the impact of wind deviation on the insulator string of the overhead transmission line.

2. A wind deviation clearance safety assessment method for power transmission lines in high wind areas according to claim 1, characterized in that: The wind speed measurement system in step 1) includes a wind speed and direction sensor, a meteorological environment monitoring unit, a data processing and substation scheduling unit, a wireless communication module, and a power supply system; the wind speed measurement system collects real-time data through the wind speed and direction sensor, and the meteorological environment monitoring unit converts the collected data into an electrical signal, and the data processing and substation scheduling unit performs standardized processing on the data, and receives instructions from the master station to decompose and execute them; The wireless communication module sends the data to the substation switch via Ethernet, and the switch transmits the data to the computing, analysis and monitoring center through the communication network; the computing, analysis and monitoring center stores and analyzes the data.

3. A wind deviation clearance safety assessment method for power transmission lines in high wind areas according to claim 2, characterized in that: The wind speed and direction sensor is a cup anemometer or an ultrasonic anemometer; the cup anemometer has a sampling frequency of 1 Hz and is installed facing due north. The wind direction angle reading increases in a clockwise direction from a top view, with north wind as 0 degrees and east wind as 90 degrees; the ultrasonic anemometer has a sampling frequency of 4 Hz.

4. A wind deviation clearance safety assessment method for power transmission lines in high wind areas according to claim 2, characterized in that: The wind speed and direction sensor includes a data acquisition instrument, which processes wind speed and direction data in real time, integrates a 4G communication module, sets the central IP, port number and communication method through serial port instructions, and then uses wireless communication to upload the collected data to the cloud server according to the user-set time period.

5. The method for evaluating windage clearance safety of power transmission lines in high wind areas according to claim 1, characterized in that: The wind field characteristic parameters in step 1) include average wind speed, average wind direction, gust factor, turbulence intensity, turbulence integral scale, and wind speed power spectrum.

6. A wind deviation clearance safety assessment method for power transmission lines in high wind areas according to claim 5, characterized in that: The downwind calculation formula for turbulence intensity is as follows: The crosswind direction calculation formula of turbulence intensity is as follows: The downwind calculation formula of the gust factor is as follows: The crosswind direction calculation formula of the gust factor is as follows: The downwind calculation formula of the turbulence integral scale is as follows: The crosswind direction calculation formula of the turbulence integral scale is as follows: 。 7. The method for evaluating windage clearance safety of power transmission lines in high wind areas according to claim 1, characterized in that: Step 2) in the process of constructing the tower-line system model, the load simulation includes gravity load, concentrated force load, wind load, and ice load, wherein the wind load includes stable wind load and random wind load; The calculation formula for the conductor wind load is: In the formula, α, μ sc , d, β c ,δ,l H , μ z , θ, and V represent wind pressure unevenness coefficient, conductor body type number, conductor outer diameter, load adjustment coefficient, ice thickness, horizontal span, wind pressure height coefficient, wind direction angle, and basic design wind speed, respectively; V is the steady wind speed; the steady wind load is applied by inputting the reference wind speed, ice thickness and wind direction angle; Before applying the random wind load, the random wind is simulated first. The downwind time history curve of the wind includes two parts: average wind and fluctuating wind v(t). The fluctuating wind is randomly simulated through the wind power spectrum. The calculation formula of the fluctuating wind is as follows: The harmonic superposition method is used to simulate the pulsating wind field.

8. The method for evaluating windage clearance safety of power transmission lines in high wind areas according to claim 1, characterized in that: Step 2) In the process of calculating the windage of the transmission line, the mass of the insulators, spacers and fittings in the line is known, and the calculation formula of the gravity load G is as follows: G=G0+nlq Where: G0 is the mass of the insulator string and hardware, n is the number of conductor splits, l is the conductor span, and q is the gravity distribution per unit length of the conductor; The rigid straight rod method is used to calculate the wind deflection angle of the suspension insulator string; the calculation formula for the wind deflection angle under wind load and gravity load is as follows: <h2 style=";text-align:left;direction:ltr">W<h2 style=";text-align:left;direction:ltr"> x <h2 style=";text-align:left;direction:ltr"> <0.5W<h2 style=";text-align:left;direction:ltr"> x左 <h2 style=";text-align:left;direction:ltr"> +0.5W<h2 style=";text-align:left;direction:ltr"> x右 IN x =En H G c =G w l H +qT Where, Wx is the equivalent wind load on the conductors on both sides, Gc is the equivalent gravity of the conductors on both sides, Wl is the self-generated wind load of the insulator string, Gl is the gravity load of the insulator string itself, lH is the horizontal span of the conductor, P is the wind load acting on the unit length of the conductor, Gw is the gravity per unit length of the conductor, T is the horizontal tension of the conductor, q is the height difference coefficient, when the height difference is 0, Gc is independent of the conductor tension T.

9. The method for evaluating windage clearance safety of power transmission lines in high wind areas according to claim 1, characterized in that: Step 2) The analysis of the wind deflection effect of the insulator string of the overhead transmission line includes: by adjusting the size of static wind and pulsating wind, setting different working conditions for wind speed impact analysis; inputting the data of the pulsating wind working condition into the program, establishing the left and right span range and interval of the transmission line according to the line span of the actual line, selecting the actual working condition, applying static wind and pulsating wind with an average wind speed of 15m / s, 20m / s, and 25m / s to its diagonal for wind deflection response analysis, and the wind field duration is 10min to obtain the respective wind deflection angle statistical results; establishing a two-span 400m conductor model, the average wind speed of the pulsating wind is 25m / s, setting different angles of attack, and performing wind deflection response analysis.

10. The method for evaluating windage clearance safety of power transmission lines in high wind areas according to claim 1, characterized in that: The method also includes the following step 3): optimizing the wind-resistant structure of the transmission line components; in the process of the optimization, simulating the connection mode of the hard connection and soft connection jumper strings of different tower shapes, simulating the arrangement mode and fatigue stress of the bird-proof spikes on the top of the tower under strong wind conditions, simulating the stress characteristics of the bird-proof umbrella or grading ring of the insulator string in the strong wind area, and simulating the influence of the bird-proof cover and bird-proof spikes on the electric field distribution and insulation performance under strong wind conditions.

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