A wind-induced flashover warning method for transmission lines based on numerical weather forecast

Abstract

The invention discloses a transmission line wind deflection flashover early warning method based on numerical weather forecast. The method comprises the following steps: step 1: inputting transmission line design parameters and transmission line area weather forecast data, and calculating a fluctuating wind speed time series Sv by using a Davenport spectrum; step 2: inputting a fluctuating wind speed time series Sv at each spatial point on a conductor and an angle θ between the wind direction and the transmission line in MATLAB, calculating the wind load on the conductor, and solving a maximum wind deflection angle φ of the transmission line by using a rigid body straight rod method; step 3: substituting the maximum wind deflection angle φ of the transmission line into structural dimension data of a specific tower, establishing a geometric relationship between the tower, the conductor, and a gap to be determined, and deducing a minimum distance x between the transmission line conductor and the tower; and step 4: introducing an S-type membership function based on a relationship between the minimum distance x between the transmission line conductor and the tower and an allowable minimum gap lmin specified in regulations to establish a mathematical model for wind deflection flashover probability and perform early warning level judgment.

Description

Technical Field

[0001] The present invention belongs to the technical field of disaster prevention and mitigation of power grids, and in particular relates to a wind deflection flashover early warning method for power transmission lines based on numerical weather forecasting. Background Art

[0002] Under the influence of strong winds, insulator strings tilt toward the tower, reducing the air gap between the conductor and the tower. When the distance fails to meet insulation strength requirements, discharge occurs, known as wind-induced discharge. Wind-induced tripping of transmission lines is one of the main factors affecting the safe and reliable supply of power. Because wind-induced tripping occurs in strong winds or in areas with low terrain, the duration of wind often exceeds the reclosing time limit, resulting in a small gap between the discharge and the reclosing device. Simultaneously, during reclosing, a switching overvoltage of a certain magnitude appears in the system, causing the gap to discharge again. This second discharge is likely to occur at a larger gap. Therefore, compared to tripping caused by other factors such as lightning strikes, the reclosing success rate is lower when the line is tripped due to wind-induced tripping, seriously affecting power supply reliability. Existing wind-induced tripping mitigation measures require either modifications to the tower structure or the installation of insulator strings and weights, which are currently difficult to fully implement. Furthermore, relying solely on primary system investment to mitigate wind-induced wind-induced discharge is neither economical nor rational. It must also be integrated with secondary system safety assessments and early warning systems, as well as optimization of power outage prevention systems. Therefore, the online early warning method for wind-induced discharge can provide scientific and technical support for power grid operators, allowing them to prepare targeted preventive control measures, as well as emergency and corrective control plans, to minimize the impact of high wind disasters. This is crucial for strengthening the power grid's analysis and outage prevention capabilities, ensuring safe and stable power transmission along major transmission lines, and improving the grid's ability to adapt to increasingly frequent meteorological disasters.

[0003] The current main research direction is to calculate the wind deviation angle and its model parameters based on wind deviation online monitoring devices or finite element simulation software. There is little research on wind deviation flashover risk warning for transmission lines.

[0004] The existing wind flashover warning for transmission lines is mainly judged based on the fitting results of parameters such as minimum distance and operating voltage. It can only qualitatively characterize the possibility of wind flashover. At this time, the accuracy of the prediction results is often affected by the errors of meteorological parameters. The opposite results are likely to occur at critical points, resulting in inaccurate prediction accuracy. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned deficiencies in the prior art and to provide a transmission line wind deflection flashover warning method based on numerical weather forecast.

[0006] In order to solve the technical problem, the technical solution of the present invention is: a transmission line wind deflection flashover early warning method based on numerical weather forecast, comprising the following steps:

[0007] Step 1: Input the transmission line design parameters and the transmission line area weather forecast data into the computer, and use the Davenport spectrum to calculate the fluctuating wind speed time history S v calculate;

[0008] Step 2: Input the pulsating wind speed time history S of each point on the conductor in MATLAB v The angle θ between the wind direction and the transmission line is used to calculate the wind load on the conductor, and the maximum wind deflection angle of the transmission line is solved using the rigid straight rod method. ;

[0009] Step 3: Set the maximum wind deflection angle of the transmission line Substitute the structural dimension data of the specific tower into the equation, establish the geometric relationship between the tower, conductor, and the gap to be determined, and derive the minimum distance x between the transmission line conductor and the tower.

[0010] Step 4: Based on the relationship between the minimum distance x between the transmission line conductor and the tower and the minimum allowable gap lmin specified in the regulations, an S-type membership function is introduced to establish a mathematical model for the probability of wind-induced flashover, and the warning level is determined based on the mathematical model.

[0011] Preferably, the specific solution of step 1 is: set the lower end of the insulator string on the left side of a base tower as the origin of the rectangular coordinate system, numbered 1, and increasing to the right, and use the average wind speed at a height of 10m above the ground in the transmission line area weather forecast provided by the Meteorological Bureau and wind direction angle β, the three coordinate axes of the rectangular coordinate system (x, y, z) are selected to correspond to the downwind direction, crosswind direction and vertical wind direction respectively, then the fluctuating wind at a certain point in space can be decomposed into three components parallel to the x, y, z coordinate axes. The Davenport spectrum is used to calculate the fluctuating wind power spectrum, and the calculation formula is:

[0012] (1)

[0013] Where:

[0014] is the average wind speed at a height of 10m above the ground, in m / s;

[0015] K is the surface roughness coefficient;

[0016] ω is the angular frequency in rad / s;

[0017] f is the frequency in Hz;

[0018] After obtaining the fluctuating wind power spectrum, the fluctuating wind speed time series S can be obtained by performing inverse Fourier transform. v .

[0019] Preferably, the maximum wind speed value in the pulsating wind speed time course is taken as the pulsating wind speed S at that point. v max .

[0020] Preferably, the specific scheme of step 2 is:

[0021] The wind direction, the angle between the transmission line direction and the due north direction are specified as the wind direction angle β and the line direction angle γ respectively. For any two towers in the transmission line, the line direction is certain, and the angle between the wind direction and the line conductor θ=β-γ.

[0022] The calculation formula of the insulator string-conductor wind deflection angle is obtained based on the tower, conductor and insulator parameters:

[0023] (2)

[0024] Where:

[0025] G d is the vertical load on the conductor, in kN,

[0026] G j is the weight of the insulator string, in kN,

[0027] F j is the wind load on the insulator string, in kN,

[0028] θ is the angle between the wind direction and the line conductor or ground line direction, in degrees.

[0029] F d is the horizontal wind load perpendicular to the conductor direction, in kN;

[0030] The horizontal wind load F d The standard value is calculated as follows:

[0031] (3)

[0032] Where:

[0033] α is the wind pressure unevenness coefficient,

[0034] μ z is the wind pressure height variation coefficient,

[0035] μ sc is the body factor of the conductor or ground wire,

[0036] d is the outer diameter of the conductor or ground wire or the calculated outer diameter when covered with ice, in meters.

[0037] L P is the horizontal spacing of the tower, in m,

[0038] θ is the angle between the wind direction and the line conductor or ground line direction, in degrees.

[0039] Is the standard value of the benchmark wind pressure, the unit is kN / m 2 ;

[0040] in Calculated by the following formula:

[0041] (4)

[0042] Insulator string wind load F j The standard value is calculated as follows:

[0043] (5)

[0044] Where:

[0045] A I is the wind-exposed area of the insulator string;

[0046] The wind deflection angle time history curve of the transmission line is obtained according to the insulator string-conductor wind deflection angle calculation formula, and then the maximum wind deflection angle of the transmission line is obtained.

[0047] Preferably, the analytical calculation formula for the minimum distance x between the transmission line conductor and the tower is:

[0048] (6)

[0049] (7)

[0050] (8)

[0051] Where:

[0052] a is the length of the insulator string, in meters,

[0053] b is the length of the cross arm of the side phase insulator hanging point, in m.

[0054] c is the horizontal distance between the middle phase insulator and the tower body, in meters.

[0055] d is the wire diameter, in m,

[0056] λ is the angle between the side cross arm and the main material of the tower, in degrees.

[0057] φ is the maximum wind deviation angle of the transmission line, in degrees.

[0058] Preferably, the specific scheme of step 4 is:

[0059] According to the relationship between the minimum distance x between the transmission line conductor and the tower in step 3 and the minimum allowable gap lmin specified in the regulations, an S-type membership function is introduced to establish a mathematical model of wind-induced flashover probability. The wind-induced flashover probability mathematical model is used to determine the warning level. The wind-induced flashover probability mathematical model is:

[0060] (9)

[0061] The values of q and Δq are determined based on actual engineering experience.

[0062] Preferably, q in step 4 is set to 1, Δq is set to 0.1, and s is set to x / lmin. s is defined as the ratio of the minimum distance x between the transmission line conductor and the tower to the minimum allowable gap lmin specified in the regulations, and lmin is the minimum allowable gap specified in the regulations. The membership relationship between the minimum distance x between the transmission line conductor and the tower and the minimum allowable gap lmin specified in the regulations is fitted to obtain the S-type membership function expression applied to wind deflection flashover:

[0063] (10).

[0064] Preferably, the warning level is determined based on the S-type membership function of wind flashover:

[0065] When 0≤s<0.9, it is a Level I warning, and wind flashover is very likely to occur;

[0066] When 0.9≤s<1, it is a Level II warning, and wind flashover is likely to occur;

[0067] When 1≤s<1.1, it is a Level III warning, and wind flashover is unlikely to occur;

[0068] When s>1.1, it is safe and wind flashover will not occur.

[0069] Compared with the prior art, the advantages of the present invention are:

[0070] (1) The present invention discloses a transmission line wind deflection flashover warning method based on numerical weather forecast. After obtaining weather forecast numerical information from the meteorological bureau, the suspension insulator string prone to wind deflection is taken as the object, and the pulsating wind speed time history is obtained by Davenport spectrum calculation. The maximum wind deflection angle of the insulator string is calculated, and based on the geometric relationship between the insulator string and the tower, an analytical calculation formula for the minimum gap is proposed. Then, an S-type membership function is introduced, and the minimum distance x between the transmission line conductor and the tower is compared with the minimum allowable gap lmin specified in the regulations, and a graded warning of wind deflection flashover is completed. The present invention quantifies the wind deflection flashover probability of a specific transmission line tower through mathematical methods, quantitatively characterizes the warning level of wind deflection flashover, and improves the reliability and accuracy of wind deflection flashover warning. The method has important practical significance for wind disaster prevention and reduction work of power grids.

[0071] (2) The present invention introduces the S-type membership function in the fuzzy function. The membership function is the basis for applying fuzzy mathematics theory to appropriately and quantitatively characterize fuzzy concepts. The present invention combines practical engineering problems with fuzzy mathematics theory, which can conveniently quantitatively characterize the probability of wind flashover and divide the warning level based on the fuzzy function, effectively ensuring the accuracy of the prediction results.

[0072] (3) The probability prediction accuracy of wind flashover of the present invention is not affected by the error of meteorological parameters, and the opposite result will not occur at the critical point. The prediction accuracy is relatively accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 This is a flow diagram of a method for early warning of wind deflection flashover of a transmission line based on numerical weather forecasting according to the present invention;

[0074] Figure 2 The time history curve of the pulsating wind speed at the hanging point of the transmission line suspension insulator string is shown in the figure.

[0075] Figure 3 It is the time history curve of wind deflection angle of transmission line insulator string;

[0076] Figure 4 This is a schematic diagram for calculating the minimum distance between a straight tower and a suspension insulator string;

[0077] Figure 5 Schematic diagram of the angle between wind direction and line direction;

[0078] Figure 6 This is a time history curve diagram of the pulsating wind speed of Example 7. DETAILED DESCRIPTION

[0079] The specific implementation of the present invention is described below in conjunction with examples:

[0080] It should be noted that the structures, proportions, sizes, etc. shown in this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions under which the present invention can be implemented. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in the present invention without affecting the efficacy and purpose that can be achieved by the present invention.

[0081] Example 1

[0082] like Figure 1 As shown, the present invention discloses a transmission line wind deflection flashover early warning method based on numerical weather forecast, comprising the following steps:

[0083] Step 1: Input the transmission line design parameters and the transmission line area weather forecast data into the computer, and use the Davenport spectrum to calculate the fluctuating wind speed time history S v calculate;

[0084] Step 2: Input the pulsating wind speed time history S of each point on the conductor in MATLAB v The angle θ between the wind direction and the transmission line is used to calculate the wind load on the conductor, and the maximum wind deflection angle of the transmission line is solved using the rigid straight rod method. ;

[0085] Step 3: Set the maximum wind deflection angle of the transmission line Substitute the structural dimension data of the specific tower into the equation, establish the geometric relationship between the tower, conductor, and the gap to be determined, and derive the minimum distance x between the transmission line conductor and the tower.

[0086] Step 4: Based on the relationship between the minimum distance x between the transmission line conductor and the tower and the minimum allowable gap lmin specified in the regulations, an S-type membership function is introduced to establish a mathematical model for the probability of wind-induced flashover, and the warning level is determined based on the mathematical model.

[0087] Example 2

[0088] like Figure 2 As shown, preferably, the specific solution of step 1 is: set the lower end of the insulator string on the left side of a base tower as the origin of the rectangular coordinate system, numbered 1, and increasing to the right. Assuming the span is 400m, a simulation point is set every 1m, and a total of 401 points are set within the 400m span; taking Class B area as an example, the 10m average wind speed v of the short-term weather forecast every 3 hours within 24 hours provided by the Meteorological Bureau is used. 10and wind direction angle β, the three coordinate axes of the rectangular coordinate system (x, y, z) are selected to correspond to the downwind direction, crosswind direction and vertical wind direction respectively, then the fluctuating wind at a certain point in space can be decomposed into three components parallel to the x, y, z coordinate axes. The Davenport spectrum is used to calculate the fluctuating wind power spectrum, and the calculation formula is:

[0089] (1)

[0090] Where:

[0091] is the average wind speed at a height of 10m above the ground, in m / s;

[0092] K is the surface roughness coefficient;

[0093] ω is the angular frequency in rad / s;

[0094] f is the frequency in Hz;

[0095] After obtaining the fluctuating wind power spectrum (fluctuating wind speed time history curve), the fluctuating wind speed time history S can be obtained by performing inverse Fourier transform. v .

[0096] Preferably, the maximum wind speed value in the pulsating wind speed time course is taken as the pulsating wind speed S at that point. v max .

[0097] Example 3

[0098] like Figure 3 、 5 As shown, preferably, preferably, the specific scheme of step 2 is:

[0099] The wind direction, the angle between the transmission line direction and the due north direction are specified as the wind direction angle β and the line direction angle γ respectively. For any two towers in the transmission line, the line direction is certain, and the angle between the wind direction and the line conductor θ=β-γ.

[0100] The calculation formula of the insulator string-conductor wind deflection angle is obtained based on the tower, conductor and insulator parameters:

[0101] (2)

[0102] Where:

[0103] G d is the vertical load on the conductor, in kN,

[0104] G j is the weight of the insulator string, in kN,

[0105] F j is the wind load on the insulator string, in kN,

[0106] θ is the angle between the wind direction and the line conductor or ground line direction, in degrees.

[0107] F d is the horizontal wind load perpendicular to the conductor direction, in kN;

[0108] The horizontal wind load F d The standard value is calculated as follows:

[0109] (3)

[0110] Where:

[0111] α is the wind pressure unevenness coefficient,

[0112] μ z is the wind pressure height variation coefficient,

[0113] μ sc is the body factor of the conductor or ground wire,

[0114] d is the outer diameter of the conductor or ground wire or the calculated outer diameter when covered with ice, in meters.

[0115] L P is the horizontal spacing of the tower, in m,

[0116] θ is the angle between the wind direction and the line conductor or ground line direction, in degrees.

[0117] Is the standard value of the benchmark wind pressure, the unit is kN / m 2 ;

[0118] in Calculated by the following formula:

[0119] (4)

[0120] Insulator string wind load F j The standard value is calculated as follows:

[0121] (5)

[0122] Where:

[0123] A I is the wind-exposed area of the insulator string;

[0124] The wind deflection angle time history curve of the transmission line is obtained according to the insulator string-conductor wind deflection angle calculation formula, and then the maximum wind deflection angle of the transmission line is obtained.

[0125] Example 4

[0126] like Figure 4 As shown, preferably, preferably, the analytical calculation formula for the minimum distance x between the transmission line conductor and the tower is:

[0127] (6)

[0128] (7)

[0129] (8)

[0130] Where:

[0131] a is the length of the insulator string, in meters,

[0132] b is the length of the cross arm of the side phase insulator hanging point, in m.

[0133] c is the horizontal distance between the middle phase insulator and the tower body, in meters.

[0134] d is the wire diameter, in m,

[0135] λ is the angle between the side cross arm and the main material of the tower, in degrees.

[0136] φ is the maximum wind deviation angle of the transmission line, in degrees.

[0137] Example 5

[0138] Preferably, according to the relationship between the minimum distance x between the transmission line conductor and the tower in step 3 and the minimum allowable gap lmin specified in the regulations, an S-type membership function is introduced to establish a wind-induced flashover probability mathematical model, and the wind-induced flashover probability mathematical model is used to determine the warning level. The wind-induced flashover probability mathematical model is:

[0139] (9)

[0140] Where q and Δq are determined based on actual engineering experience. is the independent variable.

[0141] Example 6

[0142] Preferably, q in step 4 is set to 1, Δq is set to 0.1, and s is set to x / lmin. s is defined as the ratio of the minimum distance x between the transmission line conductor and the tower to the minimum allowable clearance lmin specified in the regulations. lmin is the minimum allowable clearance specified in the regulations. See the table below for details:

[0143] Table 1 Minimum clearance allowed by regulations under different voltages

[0144]

[0145] The membership relationship between the minimum distance x between the transmission line conductor and the tower and the minimum allowable clearance lmin specified in the regulations is fitted, and the S-type membership function expression applied to wind deflection flashover is obtained:

[0146] (10)

[0147] The s in formula (10) serves as the independent variable of formula (9), that is, if x / lmin falls within the range of 0 to 0.9, the probability of wind-induced flashover on the line is 1, and so on.

[0148] Preferably, the warning level is determined based on the S-type membership function of wind flashover:

[0149] When 0≤s<0.9, it is a Level I warning, and wind flashover is very likely to occur;

[0150] When 0.9≤s<1, it is a Level II warning, and wind flashover is likely to occur;

[0151] When 1≤s<1.1, it is a Level III warning, and wind flashover is unlikely to occur;

[0152] When s>1.1, it is safe and wind flashover will not occur.

[0153] Example 7

[0154] The wind-induced flashover warning method proposed in this example was validated against a wind-induced tripping event that occurred on a faulty tower of a 220 kV transmission line in a certain region in 2021. Conductor model: 2×JL / G1A-300 / 25; insulator model: FXBW-220 / 120; tower model: 2A5-ZM2-24. The design wind speed for the faulty section was 29 m / s. The conductors in the faulty section were installed in an east-west direction, with the phase sequence from left to right, C, B, A, facing the main power line. The faulty section was flat with no micro-topography, eliminating the possibility of micro-topography affecting the line. At the time of the fault, the average wind speed at the site was 7.3 m / s (Force 4), with a maximum wind speed of 10.9 m / s (Force 6). The temperature was 32°C, the relative humidity was 26%, and there was no rainfall. At 19:19 on May 27, 2022, the line tripped, and reclosing failed. After on-site line fault inspection, it was found that the A-phase conductor (side phase) and tower body of Tower 98 had obvious discharge signs, while the other towers and ground wires on both sides were normal.

[0155] The weather station closest to the 2A5-ZM2-24 tower that caused the wind deviation trip recorded an average wind speed of 10.9m / s at a height of 10m above the ground. The wind direction was nearly perpendicular to the line direction, i.e. θ=90°, and there was no rainfall. Input the reference value into the computer, use formula (1) to calculate the simulated fluctuating wind power spectrum, and obtain the fluctuating wind speed time history curve at the point where the phase conductor hangs on the fault tower, as shown in Figure 6 As shown in the simulated pulsating wind speed time history curve of the tower, the maximum wind speed value is taken out, and the maximum wind deflection angle φ of the side phase conductor suspension insulator string is calculated based on the tower, conductor, insulator parameters, the maximum wind speed value and formula (2).

[0156] The side phase insulator string type is I string. Considering the length of the hanging ring hardware and the suspension wire clamp, the actual calculated length of the insulator string is finally taken as 2.618m. The angle between the cross arm and the main material of the tower body is 125.67°, and the distance between the cross arm and the tower body is 1.15m. According to formula (8), the minimum safe distance between the side phase conductor and the tower body is calculated to be x = 0.523m.

[0157] As shown in Table 1, the minimum allowable clearance specified in the 220 kV transmission line regulations is lmin = 0.55 m. Therefore, s = x / lmin = 0.523 / 0.55 = 0.951, indicating a Level II warning and a high risk of wind-induced flashover. Calculations show that 0.523 m < 0.550 m indicates that the distance between the edge phase conductor and the tower body exceeds the critical safety distance for discharge from the live conductor to the tower body when subjected to strong winds. Substituting this into Equation (10), the probability of line tripping due to conductor-to-tower flashover, p = 87%. The calculations and analysis confirm that the results are consistent with actual field conditions. The wind-induced flashover assessment accurately predicts that Tower #98 is prone to wind-induced flashover. Related calculations also verify the accuracy of this assessment.

[0158] The present invention discloses a transmission line wind deflection flashover warning method based on numerical weather forecast. After obtaining weather forecast numerical information from the meteorological bureau, the method takes a suspension insulator string prone to wind deflection as the object, uses Davenport spectrum calculation to obtain the pulsating wind speed time history, completes the calculation of the maximum wind deflection angle of the insulator string, and proposes an analytical calculation formula for the minimum gap based on the geometric relationship between the insulator string and the tower. Then, an S-type membership function is introduced to compare the minimum distance x between the transmission line conductor and the tower with the minimum allowable gap lmin specified in the regulations, and completes the graded warning of wind deflection flashover. The present invention quantifies the wind deflection flashover probability of a specific transmission line tower through a mathematical method, quantitatively characterizes the warning level of wind deflection flashover, and improves the reliability and accuracy of wind deflection flashover warning. The method has important practical significance for wind disaster prevention and reduction work of power grids.

[0159] The present invention introduces an S-type membership function in the fuzzy function. The membership function is the basis for applying fuzzy mathematics theory to appropriately and quantitatively characterize fuzzy concepts. The present invention combines practical engineering problems with fuzzy mathematics theory, which can conveniently quantitatively characterize the probability of wind flashover, and divides the warning level based on the fuzzy function, effectively ensuring the accuracy of the prediction results.

[0160] The probability prediction accuracy of wind flashover of the present invention is not affected by the error of meteorological parameters, and the opposite result will not occur at the critical point, so the prediction accuracy is relatively accurate.

[0161] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope of the present invention.

[0162] Many other changes and modifications can be made without departing from the spirit and scope of the present invention. It should be understood that the present invention is not limited to the specific embodiments, and the scope of the present invention is defined by the appended claims.

Claims

1. A transmission line wind deflection flashover warning method based on numerical weather forecast, characterized in that: The following steps are involved: Step 1: Input the transmission line design parameters and the transmission line area weather forecast data into the computer, and use the Davenport spectrum to calculate the fluctuating wind speed time history S v calculate; The specific solution of step 1 is as follows: let the lower end of the insulator string on the left side of a base tower be the origin of the rectangular coordinate system, numbered 1, and increase in order to the right, and use the average wind speed at a height of 10m above the ground provided by the weather forecast of the transmission line area provided by the meteorological bureau. and wind direction angle β, the three coordinate axes of the rectangular coordinate system (x, y, z) are selected to correspond to the downwind direction, crosswind direction and vertical wind direction respectively, then the fluctuating wind at a certain point in space can be decomposed into three components parallel to the x, y, z coordinate axes. The Davenport spectrum is used to calculate the fluctuating wind power spectrum, and the calculation formula is: （1）， Where: is the average wind speed at a height of 10m above the ground, in m / s; K is the surface roughness coefficient; ω is the angular frequency in rad / s; f is the frequency in Hz; After obtaining the fluctuating wind power spectrum, the fluctuating wind speed time series S can be obtained by performing inverse Fourier transform. v ; Step 2: Input the pulsating wind speed time history S of each point on the conductor in MATLAB v The angle θ between the wind direction and the transmission line is used to calculate the wind load on the conductor, and the maximum wind deflection angle of the transmission line is solved using the rigid straight rod method. ; Step 3: Set the maximum wind deflection angle of the transmission line Substitute the structural dimension data of the specific tower into the equation, establish the geometric relationship between the tower, conductor, and the gap to be determined, and derive the minimum distance x between the transmission line conductor and the tower. Step 4: Based on the relationship between the minimum distance x between the transmission line conductor and the tower and the minimum allowable clearance lmin specified in the regulations, an S-type membership function is introduced to establish a mathematical model for the probability of wind-induced flashover. The mathematical model is used to determine the warning level. The analytical calculation formula for the minimum distance x between the transmission line conductor and the tower is: (6), (7), (8), Where: a is the length of the insulator string, in meters, b is the length of the cross arm of the side phase insulator hanging point, in m. c is the horizontal distance between the middle phase insulator and the tower body, in meters. d is the wire diameter, in m, λ is the angle between the side cross arm and the main material of the tower, in degrees. φ is the maximum wind deflection angle of the transmission line, in degrees; The specific scheme of step 4 is: According to the relationship between the minimum distance x between the transmission line conductor and the tower in step 3 and the minimum allowable gap lmin specified in the regulations, an S-type membership function is introduced to establish a mathematical model of wind-induced flashover probability. The wind-induced flashover probability mathematical model is used to determine the warning level. The wind-induced flashover probability mathematical model is: （9）, The values of q and Δq are determined based on actual engineering experience.

2. The method for early warning of wind-induced flashover of power transmission lines based on numerical weather forecast according to claim 1, characterized in that: Take the maximum wind speed value in the pulsating wind speed history as the pulsating wind speed S at that point v max .

3. The method for early warning of wind-induced flashover of power transmission lines based on numerical weather forecast according to claim 1, characterized in that: The specific scheme of step 2 is: The wind direction, the angle between the transmission line direction and the true north direction are specified as the wind direction angle β and the line direction angle γ respectively. For any two towers in the transmission line, the line direction is fixed, and the angle between the wind direction and the line conductor is θ=β-γ. The calculation formula of the insulator string-conductor wind deflection angle is obtained based on the tower, conductor and insulator parameters: (2), Where: G d is the vertical load on the conductor, in kN, G j is the weight of the insulator string, in kN, F j is the wind load on the insulator string, in kN, θ is the angle between the wind direction and the line conductor or ground line direction, in degrees. F d is the horizontal wind load perpendicular to the conductor direction, in kN; The horizontal wind load F d The standard value is calculated as follows: (3), Where: α is the wind pressure unevenness coefficient, μ z is the wind pressure height variation coefficient, μ sc is the body factor of the conductor or ground wire, d is the outer diameter of the conductor or ground wire or the calculated outer diameter when covered with ice, in meters. L P is the horizontal spacing of the tower, in m, Is the standard value of the benchmark wind pressure, the unit is kN / m 2 ; in Calculated by the following formula: (4), Insulator string wind load F j The standard value is calculated as follows: (5), Where: A I is the wind-exposed area of the insulator string; The wind deflection angle time history curve of the transmission line is obtained according to the insulator string-conductor wind deflection angle calculation formula, and then the maximum wind deflection angle of the transmission line is obtained.

4. The method for early warning of wind-induced flashover of power transmission lines based on numerical weather forecast according to claim 1, characterized in that: Set q in step 4 to 1, Δq to 0.1, and let s = x / lmin. Define s as the ratio of the minimum distance x between the transmission line conductor and the tower to the minimum allowable gap lmin specified in the regulations, and lmin as the minimum allowable gap specified in the regulations. Fit the membership relationship between the minimum distance x between the transmission line conductor and the tower and the minimum allowable gap lmin specified in the regulations to obtain the S-type membership function expression applied to wind deflection flashover: (10)。 5. The method for early warning of wind-induced flashover of power transmission lines based on numerical weather forecast according to claim 4, characterized in that: The warning level is determined based on the S-type membership function of wind flashover: When 0≤s<0.9, it is a Level I warning, and wind flashover is very likely to occur; When 0.9≤s<1, it is a Level II warning, and wind flashover is likely to occur; When 1≤s<1.1, it is a Level III warning, and wind flashover is unlikely to occur; When s>1.1, it is safe and wind flashover will not occur.

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