A method for calculating flashover risk level based on an AC discharge model of icing composite insulators

Abstract

This invention discloses a method for calculating flashover risk level based on an AC discharge model of iced composite insulators. The method includes: acquiring field parameters through an intelligent monitoring device; establishing an AC discharge model of the iced composite insulator; calculating the remaining ice resistance in the AC discharge model based on the field parameters; obtaining arc development-related constants in the AC discharge model; calculating the ice flashover voltage based on the AC discharge model, field parameters, calculated remaining ice resistance, and arc development-related constants; comparing the ice flashover voltage with a preset value, and calculating and outputting the flashover risk level. This invention is adaptable to different umbrella-shaped composite insulators in light / medium / heavy icing areas, providing efficient decision support for the operation and maintenance of iced transmission lines, effectively reducing the risk of ice flashover tripping during line operation, and ensuring a safe and reliable power supply.

Description

Technical Field

[0001] This invention belongs to the field of composite insulator technology for power grids, and relates to the intelligent calculation and application of flashover voltage of icing composite insulators. Specifically, it is a method for calculating flashover risk level based on an AC discharge model of icing composite insulators. Background Technology

[0002] The insulation performance of insulators in transmission lines is severely affected by icing. Ice and snow accumulation can shorten the creepage distance and change the distribution of the surrounding electric field, leading to a sharp decline in their electrical performance.

[0003] With the development of de-icing technology for transmission line insulators, hot water jet de-icing has been increasingly applied to the removal of ice accretion from transmission line insulators due to its advantages such as high de-icing efficiency, strong adaptability, and cleanliness and environmental friendliness. During hot water jet de-icing, after the water jet acts on the insulator, the ice surface exhibits a complex state of water film, ice layer, or ice ridges. Under this non-uniform icing state, the creepage path, electric field distribution, and leakage current characteristics of the insulator surface change significantly, easily inducing multiple discharge phenomena where air gap arcs and ice surface arcs coexist, thus significantly increasing the risk of ice flashover.

[0004] Evaluating the insulation performance of insulators during hot water jet de-icing through icing flashover tests is not only extremely labor-intensive but also costly. Therefore, many scholars both domestically and internationally have conducted extensive simulation and theoretical research on the initiation and development of surface arcs on iced insulators. Based on this, they have established discharge models for iced insulators to predict critical flashover voltages and other important parameters, thereby reducing experimental costs and workload. However, existing research mostly focuses on uniform icing conditions, which fails to reflect the actual discharge characteristics of multiple ice bands coexisting and multiple arcs developing simultaneously during hot water jet de-icing. Summary of the Invention

[0005] The technical problem to be solved by this invention is to overcome the problems existing in the prior art and provide a method for calculating the flashover risk level based on the AC discharge model of icing composite insulators. This method collects insulator umbrella-shaped parameters, icing parameters, and air gap arc length through an intelligent monitoring device. After preprocessing, the data is input into the AC discharge model of the icing composite insulator. The characteristics of the air gap arc and the ice surface arc are distinguished. The remaining ice layer resistance is broken down into ice ridge resistance, umbrella surface ice layer resistance, and arc foot resistance for accurate calculation. Combined with ice ridge geometric parameters, the discharge path is adaptively determined, the ice flashover voltage is solved, and the flashover risk level is output. This realizes the engineering application of the "multi-arc-multi-ice zone" theory. It can be adapted to different umbrella-shaped composite insulators in light / medium / heavy icing areas, providing efficient decision support for the operation and maintenance of icing transmission lines, effectively reducing the risk of ice flashover tripping during line operation, and ensuring a safe and reliable power supply.

[0006] Therefore, the present invention adopts the following technical solution: a method for calculating flashover risk level based on an AC discharge model of icing composite insulators, comprising the following steps: a) Obtain field parameters through intelligent monitoring devices; b) Establish an AC discharge model for ice-covered composite insulators; c) Based on the field parameters obtained in step a) and the calculation formula for the remaining ice layer resistance, calculate the remaining ice layer resistance in the AC discharge model of the ice-covered composite insulator. d) Obtain the arc development-related constants in the AC discharge model of the icing composite insulator, including the air gap arc constant, the ice surface arc constant, the upward arc re-ignition constant, the downward arc re-ignition constant, and the arc re-ignition constant; e) Calculate the ice flashover voltage based on the AC discharge model of the ice-covered composite insulator and the data obtained in steps a), c), and d); f) Compare the ice flash voltage calculated in step e) with the preset value of ice flash voltage, calculate and output the flashover risk level.

[0007] Existing ultra-high voltage and extra-high voltage transmission lines face harsh operating conditions such as high altitude, heavy snow accumulation, and severe icing. During actual de-icing operations (commonly using hot water jets), the melting of ice on the insulator surface dynamically creates a complex water-ice mixture, leading to distortions in the surface electric field distribution and alterations in partial discharge characteristics. This introduces new uncertainties to the accurate prediction of flashover voltage. Current methods for predicting flashover voltage of iced insulators largely rely on manual testing, which is time-consuming, costly, and lacks accuracy. This invention collects a series of parameters from iced composite insulators on-site using intelligent monitoring devices, calculates and processes them to obtain the flashover voltage, and outputs the flashover risk level. The method employed in this invention eliminates the need for high-voltage testing of iced composite insulators, enabling rapid response and support for on-site operation and maintenance decisions, and has practical engineering significance.

[0008] Furthermore, in step a), the field parameters include: the diameter of the insulator's extra-large shed. D 1. Unit is cm; Diameter of the insulator's main skirt. D 2, unit is cm; thickness of ice layer on insulator surface d The unit is cm; air gap arc length x 1. Unit is cm; length of electric arc on ice surface x2. Units are in cm; a1 is the axial extension length of the tip of the ice ridge of the insulator's extra-large umbrella skirt along the insulator axis to the starting end of the ice ridge of the umbrella skirt; a2 is the vertical distance between the tip of the ice ridge and the ice ridge on the surface of the next umbrella skirt of the same type; h1 is the length of the ice ridge from the extra-large umbrella skirt to the tip; h2 is the vertical distance from the tip of the ice ridge along the radial direction of the insulator to the adjacent ice ridge; h3 is the axial distance from the tip of the ice ridge of the extra-large umbrella skirt of the icing composite insulator along the insulator axis to the surface of the ice layer of the next adjacent extra-large umbrella skirt; h4 is the distance from the end of the ice ridge along the radial direction to the surface of the outer edge of the ice layer inside the extra-large umbrella skirt of the icing composite insulator.

[0009] Furthermore, step b) specifically includes: b1) Using the improved Obenaus pollution discharge model, the basic equations for the AC discharge model of the icing composite insulator are established as follows: (1) (2) in, This is the ice flashover voltage, measured in volts (V). This is the peak leakage current, expressed in amperes (A). 、 All are air gap arc constants; 、 All are ice surface arc constants; The length of the local electric arc is expressed in cm. x 1 represents the length of the air gap arc, in cm; x 2 represents the length of the electric arc on the ice surface, in cm; Indicates the resistance of the remaining ice layer; b2) Considering the two arc feet of the air gap arc extending upward and downward respectively, the conditions for arc reignition are obtained: (3) in, To extend the arc reignition constant upwards; The re-ignition constant is developed for downward arc extension; b is the arc reignition constant.

[0010] Further, in step c), the remaining ice layer resistance is the sum of the ice cone resistance, the ice surface resistance, and the resistance generated by the convergence of the arc head current.

[0011] Furthermore, the ice cone resistance The calculation formula is: (5) In the formula, Represents a piecewise function. It represents the equivalent surface conductivity.

[0012] Furthermore, the surface resistance of the ice layer The calculation formula is: (6).

[0013] Furthermore, the resistance generated by the current convergence at the arc head The calculation formula is: (7) The formula for calculating the arc radius r is as follows: (10) in, The radius of the electric arc is expressed in centimeters. This is the arc root radius coefficient.

[0014] Furthermore, piecewise functions The calculation expression is as follows: (8) The equivalent surface conductivity The calculation expression is as follows: (9) in, The surface conductivity of the insulator when it is energized and covered with ice; The conductivity of the icing water is converted to 20°C, and the unit is... S / cm; This is a temperature correction factor; T The temperature of the water jet acting on the surface of the insulator is expressed in °C. The thickness of the water film formed by the water jet, in cm; The electrical conductivity of the hot water jet is expressed in units of... μS / cm ; , Both represent constants used to calculate the surface conductivity of an insulator at 20°C.

[0015] Furthermore, in step e), the formula for calculating the ice flash voltage is as follows: (11).

[0016] Furthermore, in step f), the formula for calculating the flashover risk level is as follows: (12) in, levelThe risk level is indicated by flashover risk: 0 represents no risk, 1 represents low risk, 2 represents medium risk, and 3 represents high risk. U This refers to the ice flashover voltage, measured in kV. U 0 represents the preset value for ice flashover voltage, in kV. This is a low-risk ice flashover voltage warning value; This is a medium-risk ice flashover voltage warning value; This is a high-risk ice flashover voltage warning value.

[0017] The beneficial effects of this invention are as follows: 1) This invention is the first to realize the engineering application of the "multi-arc-multi-ice zone" theory in hot water jet de-icing of insulators, with an ice flashover voltage prediction error of ≤10%, which is significantly better than the traditional single-arc assumption model; 2) This invention does not require artificial climate chamber testing, and can complete the ice flash voltage calculation within 30 seconds, reducing testing costs by more than 90%; 3) During hot water jet de-icing operations, a non-uniform distribution of "a water film-covered area in the middle and unmelted ice areas on both sides" is formed on the surface of the insulator. Based on this special working condition, this invention calculates the conductivity of the insulator surface and the resistance of the remaining ice layer during de-icing. 4) This invention dynamically determines the discharge path based on a2 and h2, adapting to all umbrella-shaped parameters in light / medium / heavy icing zones; 5) Composite insulators in icing areas often employ a structure with skirts of various diameters arranged in a cross configuration. After icing, they cannot be simply equated to semi-cylinders. Furthermore, the resistance of the ice ridges and the ice layer on the umbrella surface of the insulator also differs and needs to be calculated separately. In addition, multiple ice ridge air gaps are formed after the composite insulator is iced. However, the arc characteristics of the ice ridge air gaps are different from the arc development characteristics on the iced surface. It is necessary to treat these two types of arcs differently. Based on the above two differences, this invention establishes an AC discharge model according to the flashover arc extension path, which can accurately calculate the flashover voltage of different iced composite insulators. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart of a method for calculating flashover risk level based on an AC discharge model of an ice-covered composite insulator according to the present invention; Figure 2 This is a schematic diagram showing the development of the arc along the ice ridge during flashover in the AC discharge model of the ice-covered composite insulator of the present invention. Figure 3 This is a schematic diagram showing that during flashover, the electric arc develops entirely along the ice ridge in the AC discharge model of the ice-covered composite insulator of this invention. Figure 4 This is a schematic diagram showing the air gap of the field-iced insulator, the electric arc on the ice surface, and the resistance length of the remaining ice layer in a specific embodiment of the present invention; Figure 5 This is a schematic diagram illustrating the calculated values ​​of the flashover voltage of the field-iced insulator as a function of the lengths of the air gap arc and the ice surface arc in a specific embodiment of the present invention. Detailed Implementation

[0020] 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. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] Example 1 This embodiment provides a method for calculating the flashover risk level based on an AC discharge model of icing-covered composite insulators, such as... Figure 1 As shown, the steps are as follows: a) Obtain field parameters through intelligent monitoring devices; b) Establish an AC discharge model for ice-covered composite insulators; c) Based on the field parameters obtained in step a) and the calculation formula for the remaining ice layer resistance, calculate the remaining ice layer resistance in the AC discharge model of the ice-covered composite insulator. d) Obtain the arc development-related constants in the AC discharge model of the icing composite insulator, including the air gap arc constant, the ice surface arc constant, the upward arc re-ignition constant, the downward arc re-ignition constant, and the arc re-ignition constant; e) Calculate the ice flashover voltage based on the AC discharge model of the ice-covered composite insulator and the data obtained in steps a), c), and d); f) Compare the ice flash voltage calculated in step e) with the preset value of ice flash voltage, calculate and output the flashover risk level.

[0022] Specifically, in step a), the field parameters include: the diameter of the insulator's extra-large shed. D 1. Unit is cm; Diameter of the insulator's main skirt. D 2, unit is cm; thickness of ice layer on insulator surface d The unit is cm; air gap arc length x 1. Unit is cm; length of electric arc on ice surface x2. Units are in cm; a1 is the axial extension length of the tip of the ice ridge of the insulator's extra-large umbrella skirt along the insulator axis to the starting end of the ice ridge of the umbrella skirt; a2 is the vertical distance between the tip of the ice ridge and the ice ridge on the surface of the next umbrella skirt of the same type; h1 is the length of the ice ridge from the extra-large umbrella skirt to the tip; h2 is the vertical distance from the tip of the ice ridge along the radial direction of the insulator to the adjacent ice ridge; h3 is the axial distance from the tip of the ice ridge of the extra-large umbrella skirt of the icing composite insulator along the insulator axis to the surface of the ice layer of the next adjacent extra-large umbrella skirt; h4 is the distance from the end of the ice ridge along the radial direction to the surface of the outer edge of the ice layer inside the extra-large umbrella skirt of the icing composite insulator.

[0023] Specifically, step b) includes: b1) Using the improved Obenaus pollution discharge model, the basic equations for the AC discharge model of the icing composite insulator are established as follows: (1) (2) in, This is the ice flashover voltage, measured in volts (V). This is the peak leakage current, expressed in amperes (A). 、 All are air gap arc constants; 、 All are ice surface arc constants; The length of the local electric arc is expressed in cm. x 1 represents the length of the air gap arc, in cm; x 2 represents the length of the electric arc on the ice surface, in cm; Indicates the resistance of the remaining ice layer; b2) Considering the two arc feet of the air gap arc extending upward and downward respectively, the conditions for arc reignition are obtained: (3) in, To extend the arc reignition constant upwards; The re-ignition constant is developed for downward arc extension; b is the arc reignition constant.

[0024] Specifically, in step c), the remaining ice layer resistance is the sum of the ice cone resistance, the ice surface resistance, and the resistance generated by the convergence of the arc head current, calculated as follows: (4) in, The remaining ice layer resistance is expressed in units of . ; Ice cone resistance, unit: ; The surface resistance of the ice layer, in units of ; The resistance generated by the convergence of current at the tip of the electric arc, measured in units of . .

[0025] The ice cone resistance The calculation formula is: (5) In the formula, Represents a piecewise function. It represents the equivalent surface conductivity.

[0026] The surface resistance of the ice layer The calculation formula is: (6) The resistance generated by the current convergence at the arc head The calculation formula is: (7) Among them, the piecewise functions in formulas (5), (6), and (7) The calculation expression is as follows: (8) The equivalent surface conductivity The calculation expression is as follows: (9) in, is the surface conductivity coefficient of the insulator when it is energized and iced, used to characterize the surface conductivity under energized conditions, and is taken as 0.9; The conductivity of the icing water is converted to 20°C, and the unit is... S / cm; This is a temperature correction factor, adjusted according to the actual type of defrosting water. Select a concentration of 0.01~0.03, generally 0.02 for deionized water; T The temperature of the water jet acting on the surface of the insulator is expressed in °C. The thickness of the water film formed by the water jet, in cm; The electrical conductivity of the hot water jet is expressed in units of... μS / cm ; , Both represent constants used to calculate the surface conductivity of an insulator at 20°C.

[0027] During hot water jet de-icing, the residual ice layer on the surface of the composite insulator partially melts, forming a continuous or discontinuous liquid water film, which alters the conductivity of the remaining ice surface. Hot water jet de-icing not only changes the insulator surface temperature, thus altering the surface conductivity of the ice layer, but also the surface conductivity of the ice layer changes after the de-icing hot water with different conductivity interacts with the insulator surface. Therefore, the equivalent surface conductivity... γ e It can accurately characterize the conductivity of the remaining ice layer under hot water jet de-icing conditions.

[0028] The formula for calculating the arc radius r is as follows: (10) in, The radius of the electric arc is expressed in centimeters. This is the arc root radius coefficient.

[0029] In step d), the arc development-related constants are obtained from Table 1.

[0030] Table 1. Relevant constants for alternating current arcs on ice-covered surfaces.

[0031] Specifically, in step e), the ice flash voltage is obtained through the following steps: When both equations (1) and (2) are satisfied, the electric arc on the ice surface can be maintained and develop into a flashover. Therefore, by combining equations (1) and (2), we can obtain the expression for the ice flashover voltage, as follows: (11).

[0032] In the formula, 、 、 、 、 、 、 As is known from step d), This is obtained through monitoring by intelligent monitoring devices. The calculation is performed through step c). Therefore, the ice flash voltage value can be calculated in real time according to formula (11).

[0033] Specifically, in step f), the formula for calculating the flashover risk level is as follows: (12) in, levelThe risk level is indicated by flashover risk: 0 represents no risk, 1 represents low risk, 2 represents medium risk, and 3 represents high risk. U This refers to the ice flashover voltage, measured in kV. U 0 represents the preset value for ice flashover voltage, in kV. The low-risk ice flashover voltage warning value is set at 0.3; The warning value for medium-risk ice flashover voltage is set at 0.6. The high-risk ice flashover voltage warning value is set at 0.9.

[0034] Example 2 This embodiment provides a method for calculating the flashover risk level based on an AC discharge model of icing-covered composite insulators, such as... Figure 1 As shown, the steps are as follows: a) Obtain field parameters through intelligent monitoring devices; b) Establish an AC discharge model for ice-covered composite insulators; c) Based on the field parameters obtained in step a) and the calculation formula for the remaining ice layer resistance, calculate the remaining ice layer resistance in the AC discharge model of the ice-covered composite insulator. d) Obtain the arc development-related constants in the AC discharge model of the icing composite insulator, including the air gap arc constant, the ice surface arc constant, the upward arc re-ignition constant, the downward arc re-ignition constant, and the arc re-ignition constant; e) Calculate the ice flashover voltage based on the AC discharge model of the ice-covered composite insulator and the data obtained in steps a), c), and d); f) Compare the ice flash voltage calculated in step e) with the preset value of ice flash voltage, calculate and output the flashover risk level.

[0035] In this embodiment, the composite insulator is model FXBW-220 / 160.

[0036] In step a), acquiring field parameters through an intelligent monitoring device includes: Insulator extra-large umbrella skirt diameter D 1. Unit is cm; Diameter of the insulator's main skirt. D 2, unit is cm; thickness of ice layer on insulator surface d The unit is cm; air gap arc length x 1. Unit is cm; length of electric arc on ice surface x2. Units are in cm; a1 is the axial extension length of the tip of the ice ridge of the insulator's extra-large umbrella skirt along the insulator axis to the starting end of the ice ridge of the umbrella skirt; a2 is the vertical distance between the tip of the ice ridge and the ice ridge on the surface of the next umbrella skirt of the same type; h1 is the length of the ice ridge from the extra-large umbrella skirt to the tip; h2 is the vertical distance from the tip of the ice ridge along the radial direction of the insulator to the adjacent ice ridge; h3 is the axial distance from the tip of the ice ridge of the extra-large umbrella skirt of the icing composite insulator along the insulator axis to the surface of the ice layer of the next adjacent extra-large umbrella skirt; h4 is the distance from the end of the ice ridge along the radial direction to the surface of the outer edge of the ice layer inside the extra-large umbrella skirt of the icing composite insulator.

[0037] Step b) specifically includes: b1) Using the improved Obenaus pollution discharge model, the basic equations for the AC discharge model of iced insulators are established, and the specific formulas are as follows: (1) (2) in: Ice flashover voltage, kV; The peak value of the leakage current is A; 、 The air gap arc constant is taken as 178.8 and 0.5093 respectively from Table 1 of the examples; 、 The values ​​for the ice surface arc constant are 204.7 and 0.5607, respectively, taken from Table 1 of Example 1. The length of the local electric arc is in cm; x 1 represents the air gap length, in cm; x 2 represents the length of the electric arc on the ice surface, in cm.

[0038] b2) Considering that the two arc feet of the air gap arc extend upward and downward respectively, the arc reignition condition is obtained, and the specific formula is as follows: (3) in: To increase the arc reignition constant; denoted as , where b is the arc reignition constant for downward arc development; b is the arc reignition constant.

[0039] In step c), there are two possible paths for arc development during flashover of the icing composite insulator: the arc part develops along the ice ridge (…). The electric arc developed entirely along the icicle. ), respectively as Figure 2 , Figure 3 As shown, Figure 2 a1 in the middle equals Figure 3In the text, h1 and S1-S7 refer to the sheds of the FXBW-220 / 160 composite insulator. Among them, S1 and S7 are extra-large sheds, S3 and S5 are large sheds, and S2, S4 and S6 are small sheds.

[0040] The resistance of the remaining ice layer is obtained through the following steps: (4) in, The resistance of the remaining ice layer, ; For ice cone resistance, ; The surface resistance of the ice layer. ; The resistance is generated by the convergence of current at the tip of the electric arc. The relationship between the arc length of the air gap of the iced insulator, the arc length on the ice surface, and the resistance of the remaining ice layer is shown in the figure. Figure 4 .

[0041] The ice cone resistor The specific calculation formula is as follows: (5) The surface resistance of the ice layer The specific calculation formula is as follows: (6) The resistance generated by the current convergence at the arc head The specific calculation formula is as follows: (7) Among them, in formulas (5), (6), and (7) It is a piecewise function, and its specific calculation expression is as follows: (8) Among them, the equivalent surface conductivity in formulas (5), (6), and (7) γ e The calculation expression is as follows: (9) in: is the surface conductivity coefficient when charged and iced, used to characterize the surface conductivity under charged conditions, and is taken as 0.9; To convert the conductivity of the ice-covered water to 20°C, S / cm; This is a temperature correction factor, adjusted according to the actual type of defrosting water. A concentration of 0.01~0.03 is generally used for deionized water. Select 0.02; TThe temperature at which the water jet acts on the surface of the insulator is, in °C; The thickness of the water film formed by the water jet, in cm; The conductivity of the hot water jet is... μS / cm .

[0042] During hot water jet de-icing, the residual ice layer on the surface of the composite insulator partially melts, forming a continuous or discontinuous liquid water film, which alters the conductivity of the remaining ice surface. Hot water jet de-icing not only changes the insulator surface temperature, but the interaction of de-icing hot water with different conductivity levels with the insulator surface also changes the surface conductivity of the ice layer. Therefore, the equivalent surface conductivity... γ e It can accurately characterize the conductivity of the remaining ice layer under hot water jet de-icing conditions.

[0043] Based on the icicle geometry parameter a2 、 h2 determines the discharge path. Substituting equations (5), (6), and (7) into equation (9) updates the equivalent surface conductivity, yielding the ice cone resistance. K Resistance of the ice surface K .

[0044] Among them, the arc radius in formula (7) r The specific calculation formula is as follows: (10) in, The radius of the electric arc is in cm; The arc root radius coefficient is taken as 0.875 A / cm. 2 The peak leakage current is given by formula (3):

[0045] Substitute r into formula (7), and use For example, there are:

[0046] Remaining ice layer resistance value for:

[0047] In step e), the ice flashover voltage is calculated and obtained through the following steps: When both equations (1) and (3) are satisfied, the electric arc on the ice surface can be maintained and develop into a flashover. Therefore, by combining equations (1) and (3), we can obtain the expression for the ice flashover voltage, as follows: (11) In the formula, 、 、 、 、 、 、 As is known from step d), The value is obtained through intelligent monitoring devices, in centimeters. The calculation is performed through step c).

[0048] Figure 5 middle, and A univariate function, when The arc distance increases from 0 to the flashover distance. hour, At the critical length of the electric arc The maximum value appears at time ,have to U The implicit nonlinear equation is: (13) The critical arc length can be obtained by numerically solving the above equation. and critical ice flash voltage .

[0049] It should be noted that due to the ice flash voltage U Equation (13) appears simultaneously on both the left and right sides of the formula, making it an implicit nonlinear equation that cannot be solved directly analytically. In actual calculations, a numerical iteration method is used, given... Under initial conditions, first assume the initial voltage U (0) Based on the empirical ice flash voltage value of the equivalent creepage distance, it sequentially updates the arc radius, remaining ice resistance, and discharge voltage until the results of two consecutive calculations meet the convergence condition. The convergence condition is considered to be that the relative change of the ice flash voltage obtained between the two iterations is less than 1%. Alternatively, to avoid non-convergence of iterations under extreme conditions, a maximum number of iterations is set. Nmax For 50 times:

[0050]

[0051] Through the Scan for different values ​​to obtain U The functional relationship between the arc distance and the voltage is used, and its maximum value is taken as the ice flash voltage.

[0052] In step f), the specific formula for calculating the flashover risk level is as follows: (12) Where level represents the flashover risk level, 0 represents no risk, 1 represents low risk, 2 represents medium risk, and 3 represents high risk; U represents the ice flashover voltage, kV; and U0 represents the preset value of the ice flashover voltage, kV. The low-risk ice flashover voltage warning value is set at 0.3; The warning value for medium-risk ice flashover voltage is set at 0.6. The high-risk ice flashover voltage warning value is set to 0.9, and the output level is set accordingly.

[0053] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. Those skilled in the art can readily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without creative effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made to the present invention by those skilled in the art based on the disclosure thereof should be within the scope of protection of the present invention.

Claims

1. An icing composite insulator flashover risk level calculation method based on an AC discharge model, characterized in that, Including the following steps: a) Obtain field parameters through intelligent monitoring devices; b) Establish an AC discharge model for ice-covered composite insulators; c) Based on the field parameters obtained in step a) and the calculation formula for the remaining ice layer resistance, calculate the remaining ice layer resistance in the AC discharge model of the ice-covered composite insulator. d) Obtain the arc development-related constants in the AC discharge model of the icing composite insulator, including the air gap arc constant, the ice surface arc constant, the upward arc re-ignition constant, the downward arc re-ignition constant, and the arc re-ignition constant; e) Calculate the ice flashover voltage based on the AC discharge model of the ice-covered composite insulator and the data obtained in steps a), c), and d); f) Compare the ice flash voltage calculated in step e) with the preset value of ice flash voltage, calculate and output the flashover risk level.

2. The method for calculating flashover risk level based on the AC discharge model of icing composite insulators according to claim 1, characterized in that, In step a), the field parameters include: the diameter of the super-shed of the insulator D 1, unit: cm; the diameter of the large shed of the insulator D 2, unit: cm; the thickness of the ice layer on the surface of the insulator d , unit: cm; the length of the air gap arc x 1, unit: cm; the length of the ice surface arc x 2, unit: cm; the axial extension length a1 of the ice ridge tip of the super-shed of the insulator along the axial direction of the insulator to the starting end of the shed ice ridge, unit: cm; the vertical distance a2 of the ice ridge tip to the next same type shed surface ice ridge, unit: cm; the length h1 of the ice ridge from the super-shed to the tip, unit: cm; the vertical distance h2 of the ice ridge tip along the radial direction of the insulator to the adjacent ice ridge, unit: cm; the axial distance h3 of the ice ridge tip of the icing composite insulator super-shed along the axial direction of the insulator to the surface of the adjacent next level super-shed ice layer, unit: cm; the distance h4 from the ice ridge end to the outer edge ice layer surface in the radial direction of the icing composite insulator super-shed, unit: cm.

3. The method for calculating the flashover risk level based on the AC discharge model of the icing composite insulator according to claim 2, characterized in that, Step b) specifically includes: b1) Using the improved Obenaus pollution discharge model, the basic equations for the AC discharge model of the icing composite insulator are established as follows: wherein, is the ice flashover voltage in V; is the leakage current peak in A; 、 are both air gap arc constants; 、 are both ice surface arc constants; is the local arc length in cm; x 1 is the air gap arc length in cm; x 2 is the ice surface arc length in cm; denotes the residual ice layer resistance; b2) Considering the two arc feet of the air gap arc extending upward and downward respectively, the conditions for arc reignition are obtained: wherein, Kup is the upward extending development arc restriking constant; Kdown is the downward arc extending development restriking constant; b K is the arc restriking constant.

4. The method for calculating the flashover risk level based on the AC discharge model of the icing composite insulator according to claim 3, characterized in that, In step c), the remaining ice layer resistance is the sum of the ice cone resistance, the ice surface resistance, and the resistance generated by the convergence of the current at the arc head.

5. The method for calculating flashover risk level based on the AC discharge model of icing composite insulators according to claim 4, characterized in that, The ice cone resistance The calculation formula is: wherein denotes a piecewise function, denotes the equivalent surface conductivity.

6. The method for calculating flashover risk level based on the AC discharge model of icing composite insulators according to claim 4, characterized in that, The surface resistance of the ice layer The calculation formula is: In the formula, Represents a piecewise function. It represents the equivalent surface conductivity.

7. The method for calculating flashover risk level based on the AC discharge model of icing composite insulators according to claim 4, characterized in that, The resistance generated by the current convergence at the arc head The calculation formula is: In the formula, Represents a piecewise function. Indicates the equivalent surface conductivity; The formula for calculating the arc radius r is as follows: in, The radius of the electric arc is in cm. This is the arc root radius coefficient.

8. The method for calculating flashover risk level based on the AC discharge model of icing composite insulators according to any one of claims 5-7, characterized in that, Piecewise function The calculation expression is as follows: The equivalent surface conductivity The calculation expression is as follows: in, The surface conductivity of the insulator when it is energized and covered with ice; The conductivity of the icing water is converted to 20°C, and the unit is... S / cm; This is a temperature correction factor; T The temperature of the water jet acting on the surface of the insulator is expressed in °C. The thickness of the water film formed by the water jet, in cm; The electrical conductivity of the hot water jet is expressed in units of... μS / cm ; , Both represent constants used to calculate the surface conductivity of an insulator at 20°C.

9. The method for calculating flashover risk level based on the AC discharge model of icing composite insulators according to claim 3, characterized in that, In step e), the formula for calculating the ice flash voltage is as follows: 。 10. The method for calculating flashover risk level based on the AC discharge model of icing composite insulators according to claim 1, characterized in that, In step f), the formula for calculating the flashover risk level is as follows: in, level The risk level is indicated by flashover risk: 0 represents no risk, 1 represents low risk, 2 represents medium risk, and 3 represents high risk. U This refers to the ice flashover voltage, measured in kV. U 0 represents the preset value for ice flashover voltage, in kV. This is a low-risk ice flashover voltage warning value; This is a medium-risk ice flashover voltage warning value; This is a high-risk ice flashover voltage warning value.

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