Arc striking angle gap discharge design method of section insulator

Abstract

The invention discloses an arc striking angle gap discharge design method of a section insulator, and belongs to the technical field of section insulator discharge optimization. Comprising the following steps: influence of high altitude on arc striking gap discharge of a section insulator; simulating electric field distribution of the section insulator; optimizing the angle of the arc striking rod; and a grading ring is added. By the adoption of the arc striking angle gap discharge design method for the section insulator, the discharge voltage of the section insulator in a high-altitude area is improved, the method has high economical efficiency and practicability for optimizing the angle of the arc striking rod of the section insulator and improving the discharge voltage of the section insulator, the service life of the section insulator is effectively prolonged, and the service life of the section insulator is prolonged. The service life of equipment can be prolonged, the replacement and maintenance frequency is reduced, the maintenance cost of the equipment is reduced, and the operation expenditure of a company is saved.

Description

Technical Field

[0001] The invention relates to the technical field of discharge optimization of segmented insulators, and in particular to a method for designing arc-starting angle gap discharge of segmented insulators. Background Art

[0002] Segment insulators and phase insulators (short for segment and phase insulators) are the main equipment of electrified railways, but there are many types, some imported and some domestic, and they play a very important role in my country's electrified railways. Through participating in the inspection of the opening lines of Beijing-Zhengzhou, Guangzhou-Shenzhen, Hunan-Guizhou, Chengdu-Kunming, Shenshuo, and Waifu, it was found that the largest hard points of the contact network are at the segment and phase insulators. In order to solve the current collection of the pantograph network, this problem must be carefully studied and solved. According to the test results, combined with the actual situation on site and the joint analysis with the construction personnel, the formation of large hard points is mainly caused by the installation of segment and phase insulators. Segment and phase insulators have defects, concentrated mass, and are not easy to install and adjust. If the installation is defective, it is easy to form large hard points, so that the locomotive pantograph cannot pass smoothly, and in severe cases it will also affect the safety of the pantograph network. When the construction personnel adjust and deal with the problems existing in the inspection, the pantograph can pass smoothly when it is inspected again, and the hard point value is significantly reduced. Due to the inspection of the inspection vehicle, the installation and commissioning of the insulator. In short, in addition to the inherent shortcomings of segmented and phase insulators, construction and installation are very important links.

[0003] In a high-altitude, low-pressure environment, the surface discharge process of segmented insulation will be affected by the air pressure, and the flashover voltage will drop. Current research mainly focuses on the surface flashover process and arc development process of insulators in a high-altitude, low-pressure environment, and the influence of single factor analysis. There is a lack of systematic analysis of the influencing mechanism of the operating environment of electrified railways. Considering the operating environment of segmented insulators in the traction power supply system, the devices are affected by frequent overvoltage, plasma sputtering, pollution distribution and airflow field. There is still a gap in the research on insulation degradation and optimization methods of segmented insulators. Summary of the invention

[0004] The purpose of the present invention is to provide a method for designing arc-starting angle gap discharge of a segmented insulator, analyze the development characteristics of arc between electrodes and arc along the surface on the effect of high-speed airflow, pay attention to the electric field distribution characteristics of the segmented insulation device in the tunnel environment, explore the discharge mechanism of the segmented insulator, and propose an optimization theory for the insulation segmented device.

[0005] To achieve the above object, the present invention provides a method for designing arc-starting angle gap discharge of a segmented insulator, comprising the following steps:

[0006] S1. The influence of high altitude on the arc gap discharge of segmented insulators. There is an air gap between the arc gaps of segmented insulators. The factors that cause the insulation strength of the air gap to decrease significantly with increasing altitude are studied.

[0007] S2. Electric field distribution simulation of segmented insulator: establish a three-dimensional model of segmented insulator and import it into finite element simulation software to calculate the electric field distribution characteristics of the segmented insulator body and the electric field distribution of the arc-starting rod gap of the segmented insulator through mesh division;

[0008] S3. Optimize the arc-starting rod angle. Adjust the arc-starting angle of the segmented insulator to multiple arc-starting angles. Carry out pre-breakdown electric field simulation under multiple arc-starting angles. Analyze the electric field variation law in the arc-starting angle area under different arc-starting angles, and obtain the optimal arc-starting angle.

[0009] S4. Add a voltage-equalizing ring. Design the voltage-equalizing ring structure above the arc-starting rod based on the finite element simulation software. Compare the local maximum field strength of the arc-starting angle of the segmented insulator under lightning impulse at different voltage-equalizing ring radii with the local maximum field strength under the original structure.

[0010] Preferably, in step S1, the factor that significantly reduces the insulation strength of the air gap with increasing altitude is the influence of air pressure and temperature on the air, and the air pressure and temperature are expressed by relative air density δ:

[0011]

[0012] In the formula, δ is the relative density of the gas, which refers to the relative density of the gas to the standard atmospheric conditions (p s =101.3kPa,

[0013] T s =293K) density ratio; p——gas pressure during breakdown test, unit is kPa; t——temperature during breakdown test, unit is K;

[0014] The relative air density δ is expressed by the altitude H and the temperature T. The empirical formula is:

[0015] δ=(1-aH / T0) 4.26

[0016] Where, a is the air temperature gradient, which is 0.0065℃ / m; T0 is the absolute temperature under standard conditions, 293K; H is the altitude, m.

[0017] Preferably, in step S2, when performing electric field analysis, a scalar function is introduced to facilitate calculation Helps calculate electric field strength The relationship between the two is shown as follows:

[0018]

[0019] Preferably, in step S2, four basic law equations contained therein are selected for analysis according to actual electromagnetic field conditions, namely, the Maxwell-Ampere law equation, the Faraday electromagnetic induction law equation, the Gauss law equation, and the Gauss magnetic law equation;

[0020] The differential form of Maxwell's equations is shown below:

[0021]

[0022] In the formula Indicates the magnetic field strength (A / m), Indicates the electric flux density (C / m 2 ), represents magnetic induction intensity, ρ represents charge density (C / m 3 ), Indicates current density (A / m 2 );

[0023] When analyzing the electric field of high-voltage equipment, the existence of the medium is considered to supplement the above Maxwell equations. For isotropic linear media, there are:

[0024]

[0025] In the differential form of Gauss's law In, bring in and The uniform dielectric potential Poisson's equation:

[0026]

[0027] When the charge density of the electrode part of the segmented insulator is , when ρ = 0, the above formula becomes the potential Laplace equation for:

[0028]

[0029] Preferably, in step S2, when analyzing the electrostatic field problem of the segmented insulator, the Laplace equation must be combined with the boundary conditions of the electrostatic field and the properties of the potential to uniquely determine the solution. The engineering electromagnetic field divides the boundary conditions of the electrostatic field into three types:

[0030] The first type of boundary value condition: the potential value of each point on the boundary surface S of the given field is:

[0031]

[0032] The second type of boundary value condition: the potential method guide value of each point on the given field boundary surface S is:

[0033]

[0034] The third type of boundary value condition: the value of the linear combination of the potential and the potential normal derivative at each point on the given field boundary S:

[0035]

[0036] According to Gauss's law, the electric field flux within the surface S is equal to 1 / ε times the total amount of charge enclosed by the closed surface, that is:

[0037]

[0038] Where, is Φ E The electric field flux inside the surface, is the electric field strength, is the area vector of the surface element, Q m is the total amount of charge enclosed by the surface, and ε is the dielectric constant of air;

[0039] For the inhomogeneous electric field, the surface S is divided into small bins, Gauss's law is applied to each small bin, and the sum is calculated over the entire surface:

[0040]

[0041] In the formula, S i Represents each small facet on the surface S.

[0042] Therefore, the present invention adopts the arc-starting angle gap discharge design method of a segmented insulator with the above structure, which has the following beneficial effects:

[0043] The present invention improves the discharge voltage of the segmented insulator in high-altitude areas, optimizes the angle of the arc-starting rod of the segmented insulator, and improves the discharge voltage of the segmented insulator, which is highly economical and practical, effectively improves the service life of the segmented insulator, can extend the life of the equipment, reduce the frequency of replacement and maintenance, reduce the maintenance cost of the equipment, and save the company's operating expenses.

[0044] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A schematic diagram of a segmented insulator electric field simulation technology route for a segmented insulator arc-starting angle gap discharge design method of the present invention;

[0046] Figure 2 A cloud diagram of the main body potential distribution of the electric field simulation of the segmented insulator main body of the arc-starting angle gap discharge design method of the segmented insulator of the present invention;

[0047] Figure 3A local maximum field intensity distribution cloud diagram of a segmented insulator main body electric field simulation of an arc-starting angle gap discharge design method for a segmented insulator of the present invention;

[0048] Figure 4 A cloud diagram of electric field distribution of arc-starting angle gap of a segmented insulator body in an arc-starting angle gap discharge design method of a segmented insulator according to the present invention;

[0049] Figure 5 A cloud diagram of electric field distribution of arc-starting angle gap of segmented insulator main body electric field simulation of arc-starting angle gap discharge design method of segmented insulator of the present invention;

[0050] Figure 6 A schematic diagram of an equivalent circuit of voltage distribution of an insulator of a segmented insulator according to an arc-starting angle gap discharge design method of a segmented insulator of the present invention;

[0051] Figure 7 It is a distribution diagram of electric field intensity at an arcing angle of 30° for an arcing angle gap discharge design method for a segmented insulator of the present invention;

[0052] Figure 8 It is a distribution diagram of electric field intensity at an arcing angle of 40° for an arcing angle gap discharge design method for a segmented insulator of the present invention;

[0053] Fig. 9 It is a distribution diagram of electric field intensity at an arcing angle of 50° for an arcing angle gap discharge design method for a segmented insulator of the present invention;

[0054] Fig.10 It is a distribution diagram of electric field intensity at an arcing angle of 55° for an arcing angle gap discharge design method for a segmented insulator of the present invention;

[0055] Fig.11 It is a distribution diagram of electric field intensity at an arcing angle of 60° for an arcing angle gap discharge design method for a segmented insulator of the present invention;

[0056] Fig.12 It is a distribution diagram of electric field intensity at an arcing angle of 65° for an arcing angle gap discharge design method for a segmented insulator of the present invention;

[0057] Fig.13 It is a distribution diagram of electric field intensity at an arcing angle of 70° for an arcing angle gap discharge design method for a segmented insulator of the present invention;

[0058] Fig.14 It is a distribution diagram of electric field intensity at an arcing angle of 75° for an arcing angle gap discharge design method for a segmented insulator of the present invention;

[0059] Fig.15 It is a distribution diagram of electric field intensity at an arcing angle of 80° for an arcing angle gap discharge design method for a segmented insulator of the present invention;

[0060] Fig.16 It is a distribution diagram of electric field intensity at an arcing angle of 85° for an arcing angle gap discharge design method for a segmented insulator of the present invention;

[0061] Fig.17 A schematic diagram of the local maximum field strength at different arc starting angles of an arc starting angle gap discharge design method for a segmented insulator of the present invention;

[0062] Fig.18 A schematic diagram of the maximum field strength of an arcing angle of 45° under a lightning impulse in an arcing angle gap discharge design method for a segmented insulator of the present invention;

[0063] Fig.19 A schematic diagram of the maximum field strength at an arcing angle of 55° under a lightning impulse in an arcing angle gap discharge design method for a segmented insulator of the present invention;

[0064] Fig. 20 A schematic diagram of an air gap of an arc-starting structure of an arc-starting angle gap discharge design method for a segmented insulator of the present invention;

[0065] Fig.21 It is a schematic diagram of the local maximum field intensity at the arc starting angle when the grading ring diameter is 40mm in a design method for arc starting angle gap discharge of a segmented insulator of the present invention;

[0066] Fig. 22 A schematic diagram of the local maximum field intensity at the arc starting angle when the grading ring diameter is 50 mm in a design method for arc starting angle gap discharge of a segmented insulator of the present invention;

[0067] Fig.23 It is a schematic diagram of the local maximum field intensity of the arc starting angle when the grading ring diameter is 60mm in a design method of arc starting angle gap discharge of a segmented insulator of the present invention;

[0068] Fig.24 It is a schematic diagram of the local maximum field intensity at the arc starting angle when the grading ring diameter is 70mm in a design method for arc starting angle gap discharge of a segmented insulator of the present invention;

[0069] Fig.25 A schematic diagram of the local maximum electric field intensity of the voltage-sharing structure of an arc-starting angle gap discharge design method for a segmented insulator of the present invention. DETAILED DESCRIPTION

[0070] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0071] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0072] Example

[0073] The present invention provides a method for designing arc-starting angle gap discharge of a segmented insulator, comprising the following steps:

[0074] S1. The influence of high altitude on the arc gap discharge of segmented insulators. There is an air gap between the arc gaps of segmented insulators. The factors that cause the insulation strength of the air gap to decrease significantly with increasing altitude are studied.

[0075] S2. Electric field distribution simulation of segmented insulator: establish a three-dimensional model of segmented insulator and import it into finite element simulation software to calculate the electric field distribution characteristics of the segmented insulator body and the electric field distribution of the arc-starting rod gap of the segmented insulator through mesh division;

[0076] S3. Optimize the arc-starting rod angle. Adjust the arc-starting angle of the segmented insulator to multiple arc-starting angles. Carry out pre-breakdown electric field simulation under multiple arc-starting angles. Analyze the electric field variation law in the arc-starting angle area under different arc-starting angles, and obtain the optimal arc-starting angle.

[0077] S4. Add a voltage-equalizing ring. Design the voltage-equalizing ring structure above the arc-starting rod based on the finite element simulation software. Compare the local maximum field strength of the arc-starting angle of the segmented insulator under lightning impulse at different voltage-equalizing ring radii with the local maximum field strength under the original structure.

[0078] When conducting electric field analysis, a scalar function is introduced to facilitate calculations. Helps calculate electric field strength The relationship between the two is shown as follows:

[0079]

[0080] Maxwell's equations point out that when analyzing the four basic law equations contained in it according to the actual electromagnetic field conditions, they are Maxwell-Ampere's law equation, Faraday's law of electromagnetic induction equation, Gauss's law equation, and Gauss's magnetic law equation.

[55] .

[0081] The differential form of Maxwell's equations is shown below:

[0082]

[0083] In the formula Indicates the magnetic field strength (A / m), Indicates the electric flux density (C / m 2 ), represents magnetic induction intensity, ρ represents charge density (C / m 3 ), Indicates current density (A / m 2 ).

[0084] When analyzing the electric field of high-voltage equipment, the existence of the medium is considered to supplement the above Maxwell equations. For isotropic linear media, there are:

[0085]

[0086] In the differential form of Gauss's law In, bring in and The uniform dielectric potential Poisson's equation:

[0087]

[0088] When the charge density of the electrode part of the segmented insulator is , when ρ = 0, the above formula becomes the potential Laplace equation for:

[0089]

[0090] When analyzing the electrostatic field problem of segmented insulators, the Laplace equation must be combined with the boundary conditions of the electrostatic field and the properties of the potential to determine the unique solution. The engineering electromagnetic field divides the boundary conditions of the electrostatic field into three types:

[44] :

[0091] (1) The first type of boundary value condition: The potential value of each point on the boundary surface S of the given field is:

[0092]

[0093] (2) The second type of boundary value condition: The potential method guide value of each point on the given field boundary surface S is:

[0094]

[0095] (3) The third type of boundary value condition: The value of the linear combination of the potential and the potential normal derivative at each point on the given field boundary S is:

[0096]

[0097] When analyzing the electric field of the segmented insulator, since most of its electric field is non-uniform, a closed surface S is assumed to enclose the non-uniform electric field. According to Gauss's law, the electric field flux within the surface S is equal to 1 / ε times the total amount of charge enclosed by the closed surface, that is:

[0098]

[0099] Where, is Φ E The electric field flux inside the surface, is the electric field strength, is the area vector of the surface element, Q m is the total amount of charge enclosed by the surface, and ε is the dielectric constant of air.

[0100] For the inhomogeneous electric field, the surface S is divided into small cells, Gauss's law is applied to each small cell, and the sum is calculated over the entire surface, that is:

[0101]

[0102] In the formula, S i Represents each small facet on the surface S.

[0103] Electric Field Distribution Characteristics and Analysis of Sectional Insulators

[0104] Taking the main insulation part and metal guide slide of the segmented insulator as the object, the three-dimensional model of the segmented insulator is established through Solidworks software, and the technical route for electric field simulation is as follows: Figure 1 shown.

[0105] Based on the structural characteristics of the segmented insulator and referring to the accident record data of the segmented insulator in actual operation, this paper simulates the main insulation structure and arc-starting rod gap of the segmented insulator. The structural model of the segmented insulator is investigated. The number of sheds of the segmented insulator is 80, and the arc-starting angle at the connection between the arc-starting rod and the metal slide is 45°.

[0106] The first type of boundary conditions is used, that is, the potential distribution and electric field distribution of the segmented insulator components are solved when the potential of the high-voltage end and the grounding point are known. The worst operating condition of the segmented insulator is during maintenance, so the simulation conditions in this paper are set as the left side of the segmented insulator is connected to the working voltage, the right side is zero potential, and the surrounding air domain is set to zero potential.

[0107] Table 1 Relative dielectric constants of segment insulator materials

[0108]

[0109] Since the effective value of the operating voltage of the overhead line is 27.5 kV for a single phase, and considering the most serious electric field characteristics of the segmented insulator during normal operation, the high-voltage side of the segmented insulator is set to The potential distribution diagram and electric field distribution diagram of the segmented insulator body and arc-starting structure obtained from the simulation test results are shown in the figure below: Figure 2 , 3 , 4, and 5.

[0110] From the above simulation results, it can be seen that the electric field of the segmented insulator is mainly concentrated at the connection between the metal electrode and the main insulator and at the arcing angle of the metal slide. The concentrated electric field is the main factor inducing discharge of the segmented insulator. In order to study the electric field strength at the electric field concentration point, the electric field strength along the surface of the segmented insulator and the electric field strength at the arcing angle are extracted, and the electric field strength distribution diagram of the two electric field concentration points can be obtained.

[0111] Depend on Figure 6 It can be seen that the surface potential of the insulator of the segmented insulator gradually decreases from the high-voltage end to the ground end. The surface potential of the shed at the high-voltage end decreases faster and the voltage it bears is higher, while the potential in the middle part of the insulator is more uniform and the voltage it bears is lower. In engineering, insulators are usually represented as capacitors to analyze the change of their potential. The equivalent circuit of the segmented insulator insulator is as follows: Figure 6 As shown, C is the capacitance between the insulators of the segmented insulator, C1 is the capacitance of each part to the ground, C2 is the equivalent capacitance of each part to the high voltage end, and C3 is the equivalent capacitance of the air gap of the arcing angle. Because the two sides of the segmented insulator are metal electrodes, the body capacitance formed between them and the insulator is small, and the dielectric constant at the connection between the metal electrode and the insulator changes greatly, resulting in the concentration of potential at the end of the segmented insulator.

[0112] Depend on Figure 4 , 5It can be seen that there is a concentrated point of the electric field at the arc-starting angle of the segmented insulator. The main reason is that the arc-starting angle is the tip of the electrode, and the charge in the metal conductor is freely distributed, thus maintaining the electric field inside the electrode at zero. According to Gauss's law, in order to maintain the potential inside the conductor at zero, and there is no charge inside the conductor, the charge can only be distributed on the outer surface of the electrode, which can only be achieved when the charge distribution density is large where the curvature of the electrode is large and the charge distribution density is small where the curvature is small. Therefore, the potential gradient at the arc-starting angle is large, that is, the electric field strength is large.

[0113] Optimization of arc-starting rod angle

[0114] The electric field concentration in the arc-starting angle of the segmented insulator is related to the angle of the arc-starting angle in addition to the sudden change of the electric field caused by the connection of the dielectric. In order to study the optimal arc-starting angle, this section adjusts the arc-starting angle and records the change of the field strength at the bend of the arc-starting angle to determine the optimal angle of the arc-starting angle.

[0115] The arc striking angle of the segmented insulator was adjusted to 30°, 40°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, and 85°, respectively. The pre-breakdown electric field simulation was carried out under the above 10 different arc striking angles. The change law of the electric field in the arc striking angle area under different arc striking angles was studied, and the optimal arc striking angle was obtained.

[0116] Depend on Figure 7-16 It can be seen that with the adjustment of the arc striking angle, the field strength at the arc striking angle has no obvious change pattern, but compared with the original electric field strength at 45°, there is an arc striking angle lower than the field strength. When the arc striking angle is 55°, the field strength at the arc striking angle is 1.63×10 6 V / m. Fig.17 The curves of the local maximum field intensity changing with the angle adjustment under 10 different arc ignition angles were plotted.

[0117] Depend on Fig.17 It can be seen that under the 10 different arcing angles in the figure, the maximum field strength in the area at the arcing angle generally shows a trend of first decreasing and then increasing. The maximum field strength curves are relatively close when the angles are 50°, 55°, 60°, 65°, 70°, and 75°. The local maximum field strength at 55° is 13.7% lower than the maximum field strength at 45°. Therefore, it is recommended to design the arcing angle of the segmented insulator to 55° when the segmented insulator is put into use to improve the maximum field strength.

[0118] In order to further study the influence of the optimized arcing angle on the local electric field of lightning impulse, the lightning impulse simulation was carried out for the 55° arcing angle. The difference between the maximum field strength on the surface of the hardware under the instantaneous lightning impulse and the maximum field strength under the peak voltage of the lightning impulse, that is, the electrostatic field, is between 0.58% and 2.92%. In order to save the amount of calculation, this paper uses the electrostatic field instead of the transient lightning impulse for simulation. The simulation test was carried out using the lightning impulse voltage at an altitude of 4300m, and the arcing angles at 45° and 55° were tested with a lightning impulse voltage of 221.99kV to compare the optimized response of the arcing angle to the lightning impulse in high altitude areas.

[0119] From 18-19, we can see that after the arc striking angle is changed to 55°, the local maximum field strength is 9.31×10 6 V / m, compared with the original local maximum field strength of 1.08×10 7 V / m decreased by about 13.8%, and the optimized segmented insulator had increased tolerance to lightning impulses at high altitudes.

[0120] In engineering, shielding devices are often used to weaken the influence of local field strength on the protruding parts of electrodes of high-voltage equipment. Due to the characteristics of the arc-starting structure, the segmented insulator belongs to the tip of the electrode. When the electric field strength of this part exceeds the corona-starting field strength of the air, it is easy to cause gap discharge. If limiting measures are not taken in time, the arc is easy to float to the outer surface of the insulator, causing damage to the silicone rubber and affecting its overall insulation performance.

[0121] Based on the finite element simulation software, the equalizing ring structure is designed above the arc-starting rod. From the structure of the arc-starting rod, it can be seen that its end is the extension end of the electrode. Directly connecting the equalizing structure at its end can avoid the use of other parts for fixation, which will increase the protruding point of the electrode. Since adding an arc-starting device to the top of the arc-starting rod will shorten the air gap at the maximum opening of the arc-starting rod, the radius of the equalizing ring must be limited, and the air gap at the maximum opening of the arc-starting rod must not be smaller than the air gap between the arc-starting angles on both sides. The air gap diagram is shown in the figure below. Fig. 20 shown.

[0122] Therefore, based on the arc striking angle of 55°, the radii of the grading ring are designed to be 40mm, 50mm, 60mm, and 70mm respectively. The arc striking angle is taken as the research object to reduce the maximum value of its surface electric field strength to reduce the possibility of discharge accidents in the arc striking angle gap.

[0123] The electric field distribution cloud diagram at the arcing angle of the segmented insulator after installing the grading ring is as follows Figure 21-24 As shown in the figure, the local field intensity at the arc starting angle under the four different radii of the equalizing ring is reduced compared with the case without adding the equalizing ring. The local field intensity at the arc starting angle is 1.42×10 6 V / m, 1.41×10 6V / m, 1.46×10 6 V / m, 1.4×10 6 V / m, the maximum electric field strength of the four grading rings under power frequency conditions is relatively close, but compared with the structure without grading ring, the local maximum field strength of the arc striking angle is reduced. Among them, the local maximum field strength of the 70mm grading structure is 14% lower than that of the 55° arc striking structure, and about 26% lower than that of the 45° arc striking structure. Therefore, it is recommended to use a 70mm grading ring structure in engineering to optimize the local electric field at the arc striking angle.

[0124] At the same time, in order to verify the optimization performance of the grading ring structure on the local maximum field strength of the segmented insulator under lightning impulse, a simulation analysis of the segmented insulator with a 70mm grading ring was carried out with a 221.99kV lightning impulse voltage.

[0125] Depend on Fig.25 It can be seen that under the 70mm grading ring, the local maximum field strength at the arc starting angle is 8.01×10 6 V / m, compared with the local maximum field strength of 1.08×10 7 V / m decreased by 25.8%. Therefore, this structure also plays a role in optimizing the local maximum electric field intensity for the lightning impulse withstand characteristics of segmented insulators in high altitude areas.

[0126] Therefore, the present invention adopts the above-mentioned arc-starting angle gap discharge design method of a segmented insulator, which improves the discharge voltage of the segmented insulator in high altitude areas, optimizes the arc-starting rod angle of the segmented insulator, and improves the discharge voltage of the segmented insulator, which is highly economical and practical, effectively improves the service life of the segmented insulator, can extend the life of the equipment, reduce the frequency of replacement and maintenance, reduce the maintenance cost of the equipment, and save the company's operating expenses.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for designing arc-starting angle gap discharge of a segmented insulator, characterized in that: The following steps are involved: S1. The influence of high altitude on the arc gap discharge of segmented insulators. There is an air gap between the arc gaps of segmented insulators. The factors that cause the insulation strength of the air gap to decrease significantly with increasing altitude are studied. S2. Electric field distribution simulation of segmented insulator: establish a three-dimensional model of segmented insulator and import it into finite element simulation software to calculate the electric field distribution characteristics of the segmented insulator body and the electric field distribution of the arc-starting rod gap of the segmented insulator through mesh division; S3. Optimize the arc-starting rod angle. Adjust the arc-starting angle of the segmented insulator to multiple arc-starting angles. Carry out pre-breakdown electric field simulation under multiple arc-starting angles. Analyze the electric field variation law in the arc-starting angle area under different arc-starting angles, and obtain the optimal arc-starting angle. S4. Add a voltage-equalizing ring. Design the voltage-equalizing ring structure above the arc-starting rod based on the finite element simulation software. Compare the local maximum field strength of the arc-starting angle of the segmented insulator under lightning impulse at different voltage-equalizing ring radii with the local maximum field strength under the original structure.

2. The arc-starting angle gap discharge design method of a segmented insulator according to claim 1, characterized in that: In step S1, the factor that significantly reduces the insulation strength of the air gap with increasing altitude is the influence of air pressure and temperature on the air. The air pressure and temperature are expressed by relative air density δ: In the formula, δ is the relative density of the gas, which refers to the relative density of the gas to the standard atmospheric conditions (p s =101.3kPa, T s =293K) density ratio; p——gas pressure during breakdown test, unit is kPa; t——temperature during breakdown test, unit is K; The relative air density δ is expressed by the altitude H and the temperature T. The empirical formula is: δ=(1-aH / T0) 4.26 Where, a is the air temperature gradient, which is 0.0065℃ / m; T0 is the absolute temperature under standard conditions, 293K; H is the altitude, m.

3. The arc-starting angle gap discharge design method of a segmented insulator according to claim 1, characterized in that: In step S2, when performing electric field analysis, a scalar function is introduced to facilitate calculation Helps calculate electric field strength The relationship between the two is shown as follows:

4. The arc-starting angle gap discharge design method of a segmented insulator according to claim 1, characterized in that: In step S2, four basic law equations are selected for analysis according to the actual electromagnetic field conditions, namely, the Maxwell-Ampere law equation, the Faraday electromagnetic induction law equation, the Gauss law equation, and the Gauss magnetic law equation; The differential form of Maxwell's equations is shown below: In the formula Indicates the magnetic field strength (A / m), Indicates the electric flux density (C / m 2 ), represents magnetic induction intensity, ρ represents charge density (C / m 3 ), Indicates current density (A / m 2 ); When analyzing the electric field of high-voltage equipment, the existence of the medium is considered to supplement the above Maxwell equations. For isotropic linear media, there are: In the differential form of Gauss's law In, bring in and The uniform dielectric potential Poisson's equation: When the charge density of the electrode part of the segmented insulator is , when ρ = 0, the above formula becomes the potential Laplace equation for:

5. The arc-starting angle gap discharge design method of a segmented insulator according to claim 1, characterized in that: In step S2, when analyzing the electrostatic field problem of the segmented insulator, the Laplace equation must be combined with the boundary conditions of the electrostatic field and the properties of the potential to determine the unique solution. The engineering electromagnetic field divides the boundary conditions of the electrostatic field into three types: The first type of boundary value condition: the potential value of each point on the boundary surface S of the given field is: The second type of boundary value condition: the potential method guide value of each point on the given field boundary surface S is: The third type of boundary value condition: the value of the linear combination of the potential and the potential normal derivative at each point on the given field boundary S: According to Gauss's law, the electric field flux within the surface S is equal to 1 / ε times the total amount of charge enclosed by the closed surface, that is: Where, is Φ E The electric field flux inside the surface, is the electric field strength, is the area vector of the surface element, Q m is the total amount of charge enclosed by the surface, and ε is the dielectric constant of air; For the inhomogeneous electric field, the surface S is divided into small bins, Gauss's law is applied to each small bin, and the sum is calculated over the entire surface: In the formula, S i Represents each small facet on the surface S.

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