Electric field analysis method and risk assessment system for composite post insulator in different dirty forms

Abstract

The invention belongs to the technical field of electrical equipment, and discloses an electric field analysis method and a risk assessment system for a composite post insulator in different dirty forms. According to the system, an umbrella skirt which is most seriously influenced by pollution is identified by analyzing the difference of electric field characteristics of an insulator in a clean state, an integral dry pollution covering state and an integral wet pollution covering state. Wet dirt with different coverage ranges and positions is sequentially applied to the surface of the umbrella skirt, and the influence of the wet dirt on electric field characteristics is deeply analyzed. By calculating the electric field distortion rate, pollution flashover risk levels under different conditions are defined, and corresponding solutions are provided according to the risk levels. According to the method, a scientific basis is provided for a daily cleaning and maintenance strategy of the insulator, especially when the method is applied to electrified water washing operation, the operation and maintenance efficiency of the insulator is improved, and the occurrence probability of pollution flashover accidents is reduced. The quantitative analysis can help to accurately judge the pollution degree of the insulator, has a wide application prospect, and can remarkably improve the safety and operation reliability of a power system.

Description

Technical Field

[0001] The invention belongs to the technical field of power systems, and in particular relates to an electric field analysis method and a risk assessment system for composite post insulators under different contamination forms. Background Art

[0002] Composite post insulators are easy to install and resistant to pollution flashover. They have been widely used in transmission lines in recent years. Their operating stability is related to the safe operation of the power system. Post insulators are important electrical equipment and are widely used in transmission lines. Due to exposure to the air, their umbrellas are prone to accumulate dirt, which can cause the electric field along the surface of the insulator to be distorted, causing insulation aging and flashover, and even power outages. The dirt on the umbrella surface has two states: dry and wet. Under different weather conditions, the coverage range and coverage position of the dirt on the surface of the umbrella skirt are different. The dirt has two states: dry and wet. The dirt can cause the electric field along the surface of the insulator to be distorted, thereby causing insulation aging and flashover, affecting the stability of power supply, and even causing serious power outages. Therefore, it is necessary to invent the influence of different dirt on the distribution law of the electric field on the surface of the insulator. In this regard, domestic and foreign scholars have carried out a series of inventions and achieved certain results.

[0003] Since water droplets are easily formed on the surface of insulators in foggy weather and gather at the tip, Wu Guangning, Shao Mengchun and others invented the distortion characteristics of the field strength along the surface of the insulator during the dripping process of the gathered water droplets. Li Gang, Li Yanzhe and others covered the surface of the QBG-25 wrist arm insulator with clean snow and dirty snow respectively, and analyzed the changes in the field strength along the surface of the insulator when snow accumulated. Bi Maoqiang, Li Kai and others changed the structure of the ICOG corona ring and invented the influence of different bird droppings parameters on the flashover of insulators installed with ICOG corona rings. Xia Xin, Dan Shuheng and others analyzed the electric field of 10kV lightning protection insulators and optimized the parameters of the arc starting plate to make the arc starting plate have less influence on the electric field of the insulator. Zhang Zhijin, Zhang Hang and others simulated the natural freezing process on three different types of insulators and invented the phenomenon of ice flashover of insulator strings. Jia Zhidong, Ouyang Xiaogang and others invented the AC flashover characteristics of insulators when the degree of algae pollution on the surface of the insulator was different. Zhou Xudong, Lin Xin and others changed the temperature field of the pot-type insulator and analyzed the changes in the field strength distribution along the surface of the insulator under different ambient temperatures. Yang Lin, Sun Yijie and others invented the dynamic deformation of raindrops on the surface of hollow magnetic insulators under extreme rainfall, and invented the changing trend of the maximum value of the electric field between the insulator umbrellas during the dynamic deformation of raindrops. Suhaib Al-Karawi, Aws Al-Taie and others coated the insulator surface with three hydrophobic materials: Al2O3, RTV-SR, and PTFE. It was found that compared with the other two materials, when the insulator coating is PTFE, the insulator has better anti-flashover performance under pollution. HR Sezavar, N. Fahimi and others invented the probability of flashover when the insulator is contaminated with a dry band, and proposed a new risk assessment method for outdoor contaminated insulators.

[0004] The existing technology has made important progress in the research of insulator pollution flashover, but there are still several technical problems in industrial application:

[0005] 1. Lack of quantitative connection between pollution range and pollution flashover risk: Although existing studies have extensively explored the relationship between different pollutants (such as water droplets, snow, bird droppings, algae, etc.) and insulator pollution flashover, most studies focus on the phenomenon analysis under specific conditions, and lack quantitative research on the relationship between the pollution range and pollution location of composite insulators and pollution flashover. This deficiency makes it impossible to accurately assess the risk of pollution flashover under different pollution conditions, limiting reliability prediction in practical applications.

[0006] 2. Insufficient systematic research on the effects of pollutant types and environmental conditions on insulator surfaces: The effects of different environmental factors such as temperature, humidity, rainfall, and icing on the accumulation and deformation of pollutants on the insulator surface have been preliminarily analyzed. However, these studies mainly focus on single pollutants or specific environmental conditions, and lack systematic research on insulator performance under complex pollutants and complex environmental factors (such as the coexistence of multiple pollutants, extreme weather, etc.), making it difficult to provide comprehensive guidance for insulator design under different environmental conditions.

[0007] 3. Lack of relationship between composite insulator structure optimization and flashover performance: At present, the optimization of insulator corona rings, arc-starting plates and other structures has been applied to traditional ceramic or glass insulators. However, due to its unique material and structural characteristics, there are few studies on optimizing electric field distribution and reducing flashover risks. This leads to the relatively insufficient flashover protection performance of existing composite insulators in complex environments, which affects their widespread promotion and application.

[0008] 4. Insufficient long-term performance evaluation under pollution conditions: Existing technologies focus more on short-term research on pollution deformation, pollution thickness and insulation performance of insulator surfaces, but lack evaluation of insulator flashover performance under long-term pollution conditions. This deficiency makes it difficult to accurately predict the performance of insulators after long-term operation in practical applications, thus bringing potential safety hazards and affecting the operational stability of the power system.

[0009] 5. Lack of quantitative methods for pollution risk assessment: Although some studies have proposed some pollution risk assessment methods, such as flashover probability calculation for different types of pollutants, these methods are mostly based on laboratory conditions and lack quantitative assessment in actual complex environments. Especially in the application of composite insulator industry, the types of pollutants, environmental conditions and insulator structures are complex and changeable. The reliability and application promotion of the assessment model still need to be further improved.

[0010] In general, the existing technology has not yet completely solved the quantitative relationship between the pollution location, pollution range and pollution flashover risk of composite insulators in industrial applications. The lack of systematic research and long-term evaluation has restricted the reliable operation and promotion and application of insulators in complex environments. Summary of the invention

[0011] In view of the problems existing in the prior art, the present invention provides an electric field analysis method and system for a composite post insulator under different contamination forms.

[0012] The present invention is implemented as follows: an electric field analysis method for composite post insulators under different pollution forms, applying a rated voltage of 110kV to the composite post insulator, and performing calculation and analysis using a finite element algorithm, specifically comprising the following steps:

[0013] Step 1: Analyze the differences in electric field characteristics when the composite post insulator is clean, covered with dry pollution, and covered with wet pollution, and find the shed that is most seriously affected by pollution;

[0014] First, the electric field intensity distribution along the surface of the composite insulator under clean conditions is calculated; then, all surfaces of the insulator sheds are evenly covered with dirt, and the dirt is defined as dry dirt and wet dirt in turn, and the electric field intensity distribution along the surface of the insulator under dry dirt and wet dirt conditions is calculated respectively; compared with the electric field intensity distribution when clean, the shed most seriously affected by dirt is found; then, the change in the magnitude of the electric field intensity is calculated and analyzed when the scope and position of dirt accumulation on the surface of this shed changes;

[0015] Step 2, applying wet dirt with different coverage ranges and different positions on the upper surface of the shed of the composite post insulator in sequence; analyzing the influence of the dirt coverage range and dirt coverage position on the upper surface of the shed on the electric field characteristics of the insulator;

[0016] The thickness and state of the pollution on the upper surface of the shed are the same, and the changes in the field strength along the surface of the insulator are analyzed when the upper surface of the shed is completely covered with pollution, 2 / 3 of the upper surface is covered with pollution, and 1 / 3 of the upper surface is covered with pollution;

[0017] The pollution with the same coverage range and the same state on the upper surface of the shed is analyzed, and the changes of the electric field along the surface of the insulator are analyzed when the pollution covers the front section, the middle section and the rear section of the upper surface of the shed respectively.

[0018] Calculate the electric field distortion rate in each case and confirm the risk level and response measures for each contamination situation according to the pre-defined risk range.

[0019] Furthermore, the composite post insulator has a total of 25 sheds, one large shed and two small sheds arranged in sequence, from the high voltage end to the grounding end, and the sheds are marked as shed No. 1 to shed No. 25 in sequence.

[0020] Furthermore, the composite post insulator shed material is silicone rubber with a rated voltage of 110 kV. In the simulation calculation, a high potential is applied. The electric potential and the electric field frequency are 50 Hz, and the current field module is used in COMSOL to calculate.

[0021] Furthermore, under natural conditions, the surface of the insulator is covered with fine dirt. Therefore, the dirt on the surface of the insulator is set to a uniform dirt layer of 1 mm.

[0022] Furthermore, to reflect the change of the electric field, the electric field distortion rate α is defined as:

[0023] α=(e Δ / e0)×100% (1)

[0024] e Δ =et -e0 (2)

[0025] where e t is the peak value of field strength when a shed is polluted, e0 is the peak value of field strength when the shed is clean, and e Δ is the change in electric field intensity when the shed is contaminated compared to when it is clean.

[0026] Furthermore, four levels of insulator flashover risk are defined here. When the electric field distortion rate is greater than 50%, the risk level is dangerous. At this time, the insulation performance of the insulator is significantly reduced, and flashover accidents are prone to occur. The insulator needs to be cleaned with live water immediately; when the electric field distortion rate is between 50% and 35%, the risk level is high risk, and a cleaning strategy should be formulated as soon as possible; when the electric field distortion rate is between 35% and 20%, the risk level is medium risk, and the safety performance of the insulator is general. When the air humidity is high, the insulator should be cleaned; when the electric field distortion rate is between 20% and 10%, the risk level is low risk, the electric field distortion of the insulator is not large, and the probability of flashover is small. Generally, there is no need to consider cleaning the insulator; when the electric field distortion rate is less than 10%, it is defined as low risk. At this time, the dirt has little effect on the insulation performance of the insulator, and the change of the insulator electric field is within a safe range.

[0027] Furthermore, the electric field distribution along the surface of the insulator is approximately symmetrical. The electric field strength is relatively large near the sheds of the hardware on both sides, which is prone to pollution flashover. When the surface of the insulator is covered with dirt, the field strength of the insulator will increase. At the No. 1 shed, the field strength distortion is the most serious. Since wet dirt has better conductivity, the field strength distortion caused by wet dirt is greater than that caused by dry dirt.

[0028] Furthermore, at the No. 1 shed, the larger the coverage of dirt on the shed surface, the greater the field strength distortion along the shed surface;

[0029] At the No. 1 shed, the closer the dirt coverage position on the shed upper surface is to the shed edge, the greater the field strength distortion along the shed surface; when the dirt covers the back of the shed, it has little effect on the shed field strength.

[0030] Another object of the present invention is to provide a pollution flashover risk assessment system for composite post insulators under different pollution forms, comprising:

[0031] The shed determination module analyzes the differences in the electric field characteristics of the composite post insulator when it is clean, covered with dry pollution, and covered with wet pollution, and finds the shed that is most seriously affected by pollution;

[0032] The electric field characteristic analysis module sequentially applies wet dirt with different coverage ranges and different positions on the upper surface of the shed of the composite post insulator; and analyzes the influence of the dirt coverage range and dirt coverage position on the upper surface of the shed on the electric field characteristics of the insulator.

[0033] The risk assessment module calculates the electric field distortion rate under different pollution conditions, and rates the risk of pollution flashover according to the magnitude of the electric field distortion rate. Under standard atmospheric pressure, the breakdown field strength of air is about 30kV / cm. According to calculations, the maximum field strength of this type of insulator under clean and rated voltage conditions is 22.36kV / cm. If the air breakdown field strength is reached, the electric field distortion rate is 34.17%. Therefore, when the electric field distortion rate is less than about 35%, the field strength of the insulator is in a safer range. Four levels of insulator pollution flashover risk are defined. When the electric field distortion rate is greater than 50%, the risk level is dangerous. At this time, the insulation performance of the insulator is significantly reduced, and flashover accidents are prone to occur. The insulator needs to be cleaned with live water immediately; when the electric field distortion rate is between 50% and 35%, the risk level is high risk, and a cleaning strategy should be formulated as soon as possible; when the electric field distortion rate is between 35% and 20%, the risk level is medium risk, and the safety performance of the insulator is general. When the air humidity is high, the insulator should be cleaned; when the electric field distortion rate is between 20% and 10%, the risk level is low risk, the electric field distortion of the insulator is not large, and the probability of flashover is small. Generally, there is no need to consider cleaning the insulator; when the electric field distortion rate is less than 10%, it is defined as low risk. At this time, the dirt has almost no effect on the insulation performance of the insulator, and the change of the insulator electric field is within a safe range. Through the electric field distortion rate, we can intuitively understand the changes in the insulation field strength, and formulate a cleaning strategy scientifically and efficiently according to the risk level.

[0034] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0035] First, the present invention uses FZ-110 / 5 composite post insulator as the invention object and uses COMSOL finite element analysis software for calculation and analysis. Compared with other inventions, the present invention mainly conducts quantitative analysis on the change of electric field strength along the surface of the insulator when the pollution coverage range and coverage position are different, based on the electric field distortion rate.

[0036] First, the differences in the electric field characteristics of the insulator when it is clean, covered with dry dirt as a whole, and covered with wet dirt as a whole are analyzed. The analysis shows that compared with the clean state, the electric field strength is improved when all surfaces of the shed are evenly covered with dry dirt; when all surfaces are evenly covered with wet dirt, the electric field strength is significantly improved, and the changes in the electric field strength of the first and last sheds of the insulator are most significant. In order to explore the influence of the coverage range and position of dirt on the upper surface of the shed on the electric field characteristics of the insulator. Wet dirt with different coverage ranges and different positions is applied to the upper surface of the No. 1 shed of the insulator in sequence. The analysis shows that the larger the coverage range of dirt on the upper surface, the higher the electric field strength at the tip of the insulator, and the more likely it is to flashover; when the coverage range of dirt is the same, the closer the dirt position is to the tip of the insulator, the more likely it is for the insulator to flashover. The invention of the electric field distribution characteristics of the insulator umbrella surface under different forms of dirt is conducive to determining the risk of insulator flashover, facilitating the scientific formulation of live water washing strategies for insulators, improving the efficiency of daily operation and maintenance of insulators, and reducing the economic losses caused by flashover.

[0037] Based on finite element simulation, the present invention studies the coverage range and coverage position of the surface contamination of the FZ-110 / 5 composite post insulator shed, and the following conclusions are drawn:

[0038] (1) The electric field distribution along the insulator surface is approximately symmetrical. The electric field strength is larger near the sheds of the hardware on both sides, making it more prone to flashover. When the surface of the insulator is covered with dirt, the field strength of the insulator will increase. At the shed No. 1, the field strength distortion is the most serious. Since wet dirt has better conductivity, the field strength distortion caused by wet dirt is greater than that caused by dry dirt.

[0039] (2) At the No. 1 shed, the larger the dirt coverage on the shed surface, the greater the field strength distortion along the shed surface.

[0040] (3) At the No. 1 shed, the closer the dirt coverage position on the shed is to the shed edge, the greater the distortion of the field strength along the shed. When the dirt covers the rear section of the shed, the effect on the shed field strength is small.

[0041] (4) At the No. 1 shed, when the upper surface of the shed is fully covered with wet dirt, the electric field distortion rate is 61.09%. At this time, the risk level is dangerous, and the insulator should be immediately washed with live water; when the wet dirt covers 2 / 3, the electric field distortion rate is 48.12%. At this time, the risk level is high risk, and the insulator should be cleaned as soon as possible; when the wet dirt covers 1 / 3, the electric field distortion rate is 21.82%. At this time, the risk level is medium risk and close to low risk, and the insulator should be cleaned as needed.

[0042] (5) At the No. 1 shed, when the wet dirt covers the front section of the upper surface of the shed, the electric field distortion rate is 21.82%. At this time, the risk level is medium risk, and the impact on the insulator electric field is small; when the wet dirt covers the middle section, the electric field distortion rate is 11.72%, and the risk level is low risk; when the wet dirt covers the rear section, the electric field distortion rate is 5.90%, and the risk level is low risk, and the insulator does not need to be cleaned.

[0043] Second, the expected benefits and commercial value of the technical solution of the present invention after transformation are:

[0044] Pollution flashover is most likely to occur at the sheds at both ends of composite post insulators. The electric field distortion rate can be determined by analyzing the electric field distribution characteristics under different surface pollution conditions, and the risk level of pollution flashover can be determined by the magnitude of the electric field distortion rate. Based on the risk level, a scientific live water flushing strategy for insulators can be formulated to provide guidance for on-site equipment operation and maintenance, and improve the efficiency of daily operation and maintenance of insulators, which has important practical significance.

[0045] The technical solution of the present invention fills the technical gap in the industry at home and abroad: currently there are few quantitative inventions on the relationship between the pollution range, pollution location and pollution flashover of composite insulators. The present invention quantitatively analyzes the risk level of pollution flashover of insulators under different pollution conditions, and thus determines the pollution degree of the insulator according to the risk level.

[0046] Third, the technical solution of the present invention solves the following key problems in the prior art in industrial applications and has achieved significant technical progress:

[0047] 1. Existing technical problems: Deterioration of insulator performance due to uneven electric field distribution

[0048] When traditional composite post insulators are covered with dirt, the electric field distribution is prone to imbalance, especially under different dirt forms, the electric field strength on the insulator surface varies significantly, which can easily cause partial discharge or flashover of the insulator, affecting the insulation performance. The present invention analyzes the electric field of different dirt forms and finds the shed area with the most serious dirt impact, which can effectively identify and optimize the insulator structure design and improve the insulator's anti-pollution performance.

[0049] 2. Problems with existing technologies: Inability to effectively assess the impact of pollution coverage

[0050] Traditional electric field analysis methods are difficult to accurately assess the impact of pollution coverage and location on electric field distribution, resulting in the inability to take targeted countermeasures in insulator design and maintenance. This invention introduces the finite element algorithm and combines the electric field calculation under various pollution conditions to deeply analyze the impact of pollution coverage and location on electric field characteristics, providing a theoretical basis for the rational design of insulators and solving the problem of inaccurate assessment in the prior art.

[0051] 3. Existing technical problems: lack of targeted detection and maintenance measures

[0052] In the prior art, the detection and maintenance of insulators under different pollution conditions mainly rely on experience and lack scientific basis. The present invention simulates and analyzes the changes in the electric field under different pollution conditions, accurately identifies which areas have the most serious electric field distortion when covered by pollution, and introduces the electric field distortion rate to determine the risk level of pollution flashover of insulators, effectively helping power engineering personnel to clean and maintain insulators in a targeted manner, reducing the risk of insulator failure.

[0053] 4. Significant technological progress: Improving insulator stability and reliability

[0054] The present invention not only solves the problems of uneven electric field and inaccurate detection, but also finds the most vulnerable shed area through in-depth analysis of the coverage and location of pollution, and proposes an optimized design scheme to improve the electric field distribution; it also proposes an insulator risk assessment scheme, which uses the electric field distortion rate to determine the risk level of pollution flashover of insulators, and proposes insulator maintenance methods under corresponding risks. Operation and maintenance personnel can scientifically formulate insulator cleaning strategies based on risk levels, which significantly improves the stability and reliability of insulators and has important application value in power systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 is a sample structure diagram provided by an embodiment of the present invention;

[0056] Figure 2 is a two-dimensional axisymmetric model diagram of an insulator provided by an embodiment of the present invention;

[0057] Figure 3 This is a surface electric field distribution diagram of an insulator provided by an embodiment of the present invention when it is clean;

[0058] Figure 4 It is a line diagram of the field strength along the surface of the insulator when it is clean provided by an embodiment of the present invention;

[0059] Figure 5 is a schematic diagram of a contamination layer provided by an embodiment of the present invention;

[0060] Figure 6 It is a line diagram of field strength along the surface of an insulator during dry pollution provided by an embodiment of the present invention;

[0061] Figure 7 This is a comparison diagram of the field strength along the surface of the insulator when it is clean and when it is dry and polluted provided by an embodiment of the present invention;

[0062] Figure 8 It is a line diagram of field strength along the surface of an insulator when wet contaminated provided by an embodiment of the present invention;

[0063] Fig. 9This is a comparison diagram of the field strength along the surface of the insulator when it is clean and wet and contaminated provided by an embodiment of the present invention;

[0064] Fig.10 It is a comparison diagram of the field strength along the surface of clean, dry-contaminated and wet-contaminated insulators provided by an embodiment of the present invention;

[0065] Fig.11 It is a model diagram of different pollution coverage ranges provided by an embodiment of the present invention;

[0066] Fig.12 1 is a field strength distribution diagram of No. 1 shed with different coverage ranges provided by an embodiment of the present invention; (a) electric field distribution along the surface when the upper surface of No. 1 shed is fully covered by dirt, (b) electric field distribution along the surface when the upper surface of No. 1 shed is 2 / 3 covered by dirt, (c) electric field distribution along the surface when the upper surface of No. 1 shed is 1 / 3 covered by dirt;

[0067] Fig.13 It is a field strength comparison diagram for different pollution coverage ranges provided by an embodiment of the present invention;

[0068] Fig.14 It is a model diagram of different pollution coverage positions provided by an embodiment of the present invention;

[0069] Fig.15 1 shed at different coverage positions provided by an embodiment of the present invention; (a) the electric field distribution along the surface when the dirt on the upper surface of the shed No. 1 covers the front section, (b) the electric field distribution along the surface when the dirt on the upper surface of the shed No. 1 covers the middle section, (c) the electric field distribution along the surface when the dirt on the upper surface of the shed No. 1 covers the rear section;

[0070] Fig.16 It is a comparison diagram of field strength at different pollution coverage positions provided by an embodiment of the present invention;

[0071] Fig.17 It is a flow chart of the electric field analysis method of the composite post insulator under different pollution forms provided by the embodiment of the present invention;

[0072] Fig.18 It is a structural diagram of an electric field analysis system under different contamination forms of a composite post insulator provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0073] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0074] The electric field analysis method of composite post insulators under different pollution forms provided by the present invention applies a rated voltage of 110kV to the insulator and analyzes its electric field characteristics in combination with the finite element algorithm, revealing the influence of pollution coverage on the electric field intensity distribution of the insulator. Its working principle can be divided into the following steps:

[0075] First, in a clean state, the distribution of the electric field strength along the surface of the insulator is calculated. Through numerical simulation, the electric field strength at each location on the surface of the clean insulator shed is obtained as a basic reference value. Then, the surface of the insulator shed is evenly covered with dirt. The dirt is divided into two states: dry dirt and wet dirt. The electric field strength distribution of the insulator in the dry dirt and wet dirt states is calculated respectively. By comparing the difference in electric field distribution between the clean state and the dirt-covered state, the part of the shed most seriously affected by dirt is found.

[0076] Next, the analysis focuses on the sheds that are most affected by contamination. When the coverage or position of contamination on the surface of the shed changes, the electric field strength also changes. Through finite element analysis, the changes in the distribution of electric field strength on the shed surface under different contamination coverage and positions can be accurately calculated. For example, when the contamination is mainly concentrated at the front, middle or rear end of the shed, the distribution of electric field strength will be different. This process helps to understand the extent to which the accumulation of contamination in different parts affects the electric field distribution of the insulator.

[0077] Then, the analysis is conducted for different pollution coverage conditions. When the same pollution is applied to the upper surface of the shed, but the coverage is 1 / 3, 2 / 3, and full coverage, the electric field strength distribution will show different change trends. Through the calculation and analysis of these changes, the influence of pollution coverage on the electric field distribution along the insulator surface can be revealed, and the area with the most severe field strength under a specific coverage range can be found.

[0078] Finally, we further analyzed the changes in the electric field strength when the front, middle and rear ends of the shed were covered with dirt. Through these analyses, we can derive the influence mechanism of the dirt coverage position on the electric field distribution of the insulator, and clarify how the accumulation of dirt at different positions causes electric field distortion. This analysis method can not only provide a basis for cleaning dirt, but also provide a reference for insulator design and maintenance, and improve the stability and reliability of power equipment.

[0079] The present invention takes FZ-110 / 5 type composite post insulator as the analysis object, applies a rated voltage of 110 kV to the insulator, and performs calculation and analysis using a finite element algorithm.

[0080] like Fig.17As shown in the figure, the differences in electric field characteristics when the insulator is clean, covered with dry dirt as a whole, and covered with wet dirt as a whole are analyzed. The analysis found that compared with the clean state, the electric field strength is improved when all surfaces of the shed are evenly covered with dry dirt; the electric field strength is significantly improved when all surfaces are evenly covered with wet dirt, and the change in electric field strength between the first and last sheds of the insulator is the most significant.

[0081] In order to analyze the influence of the pollution coverage range and pollution coverage position on the shed surface on the electric field characteristics of the insulator. Wet dirt with different coverage ranges and different positions was applied to the upper surface of the shed No. 1 insulator in turn. The analysis found that: the larger the pollution coverage range on the upper surface, the higher the electric field strength at the tip of the insulator, and the more prone to flashover; when the pollution coverage range is the same, the closer the pollution position is to the tip of the insulator, the more likely the insulator is to flashover. The invention of the electric field distribution characteristics of the insulator umbrella surface under different forms of pollution is conducive to the scientific formulation of the live water washing strategy for the insulator and improve the efficiency of daily operation and maintenance of the insulator.

[0082] 1 Calculation model and parameters

[0083] 1.1 Insulator model and parameters

[0084] This invention takes FZ-110 / 5 type post composite insulator as the invention object. The test product structure diagram and modeling diagram are as follows: Figure 1 The test specimen structural parameters are shown in Table 1. The test specimen has a total of 25 sheds, one large shed and two small sheds arranged in sequence. For the convenience of subsequent discussion, the sheds are marked as sheds No. 1 to No. 25 from the high voltage end to the ground end.

[0085] Table 1 Structural parameters of the test pieces

[0086]

[0087] The insulator of this test product is axisymmetric. To simplify the calculation, a two-dimensional axisymmetric model is established for the insulator. The circular air region with a radius of 2.3m near the insulator is as follows: Figure 2 This simulation only focuses on the insulator itself, calculating the electric field distribution within a relatively small range around the insulator and its surroundings, and ignoring the effects of the pantograph and contact network.

[0088] 1.2 Condition setting and material parameters

[0089] The shed material of the composite post insulator of this test product is silicone rubber, with a rated voltage of 110kV. In the simulation calculation, a potential is applied to the high potential, the electric field frequency is 50Hz, and the current field module is used in COMSOL for calculation. The relative dielectric constants of the composite post insulator material and contamination are shown in Table 2.

[0090] Table 2 Material parameters

[0091]

[0092] The surface of the insulator is often covered with a thin layer of fine ash. Therefore, in subsequent inventions, the dirt on the surface of the insulator is set to a uniform dirt layer of 1 mm. There are two types of dirt. Generally, the dirt is dry. In drizzling weather, the dirt is fully wetted to form wet dirt. The relative dielectric constant of dry dirt is set to 2.8, and the relative dielectric constant of wet dirt is set to 35. The specific analysis method is:

[0093] (1) First, calculate the electric field intensity distribution along the surface of the composite insulator under clean conditions. Then, all surfaces of the insulator sheds are evenly covered with dirt, and the dirt is defined as dry dirt and wet dirt in turn. The electric field intensity distribution along the surface of the insulator under dry dirt and wet dirt conditions is calculated respectively. Compare with the electric field intensity distribution when it is clean to find the shed that is most seriously affected by dirt. Then focus on calculating and analyzing the changes in the magnitude of the field when the scope and position of dirt accumulated on the surface of this shed changes.

[0094] (2) Under natural conditions, the upper surface of the large shed is most likely to accumulate dirt. In order to simulate the actual situation, only the upper surface of the shed is covered with dirt. In order to explore the influence of different dirt coverage areas on the electric field strength along the insulator surface, the above-mentioned shed upper surface is covered with dirt of the same thickness and state, and the insulator surface field strength changes when the upper surface of the shed is completely covered with dirt, 2 / 3 of the area is covered with dirt, and 1 / 3 of the area is covered with dirt.

[0095] (3) In order to analyze the influence of different pollution positions on the electric field strength along the surface of the insulator, the invention discloses the change of the electric field along the surface of the insulator when the pollution covers the front end, middle end and rear end of the upper surface of the shed respectively, with the same coverage range and the same state of pollution on the upper surface of the shed.

[0096] Define the electric field distortion rate α.

[0097] α=(e Δ / e0)×100% (1)

[0098] e Δ =e t -e0 (2)

[0099] where e t is the peak value of field strength when a shed is polluted, e0 is the peak value of field strength when the shed is clean, and e Δ is the change in electric field intensity when the shed is contaminated compared to when it is clean.

[0100] like Fig.18 As shown, the electric field analysis method of the composite post insulator under different pollution forms and the electric field analysis system of the composite post insulator under different pollution forms provided by the embodiment of the present invention include:

[0101] The shed determination module analyzes the differences in the electric field characteristics of the composite post insulator when it is clean, covered with dry pollution, and covered with wet pollution, and finds the shed that is most seriously affected by pollution;

[0102] The electric field characteristic analysis module sequentially applies wet dirt with different coverage ranges and different positions on the upper surface of the shed of the composite post insulator; and analyzes the influence of the dirt coverage range and dirt coverage position on the upper surface of the shed on the electric field characteristics of the insulator.

[0103] The risk assessment module calculates the electric field distortion rate under different pollution conditions, and rates the risk of flashover according to the magnitude of the electric field distortion rate. Four levels of insulator flashover risk are defined. When the electric field distortion rate is greater than 50%, the risk level is dangerous; when the electric field distortion rate is between 50% and 35%, the risk level is high risk; when the electric field distortion rate is between 35% and 20%, the risk level is medium risk; when the electric field distortion rate is between 20% and 10%, the risk level is low risk; when the electric field distortion rate is less than 10%, it is defined as low risk.

[0104] The present invention studies the change of electric field strength when the surface of FZ-110 / 5 type post composite insulator is covered with dirt, and proposes a risk assessment method based on electric field distortion rate. Compared with other inventions, the present invention analyzes different dirt and quantitatively analyzes the change of field strength caused by dirt. The electric field distortion rate can intuitively judge the degree of insulator pollution and the risk of pollution flashover of insulator.

[0105] The invention belongs to the technical field of power system, and is applicable to judging the pollution degree of FZ-110 / 5 type post composite insulator and the risk level of pollution flashover. The idea of ​​the invention is also applicable to similar composite post insulators. It provides a basis for formulating daily cleaning and maintenance plans for insulators, and has good application prospects.

[0106] By drawing the electric field strength model diagram, we can preliminarily determine the electric field strength distribution of the insulator. When the insulator is clean, the surface electric field distribution is as follows: Figure 3 shown.

[0107] exist Figure 3 In the figure, it can be clearly seen that the field strength at the two ends of the hardware is relatively large, the field strength of the shed close to the hardware is relatively large, and the field strength of the shed in the middle is relatively small. In the same shed, the field strength at the edge of the shed is relatively large.

[0108] In order to more intuitively reflect the changing trend of the electric field value, a distribution line diagram of the electric field intensity along the surface of the insulator is drawn when it is clean, such as Figure 4 shown.

[0109] It can be seen that when clean, the electric field strength of the No. 1 shed is the largest, with an extreme value of 22.36 kV / cm; the electric field strength near the No. 13 shed located in the middle area of ​​the insulator is relatively small; the field strength from No. 13 to No. 25 sheds is generally on the rise; the electric field strength is generally symmetrically distributed. It can be seen that the sheds close to the high-voltage end and the ground end are prone to surface discharge.

[0110] 2.1.2 Distribution of electric field along the surface of insulator when it is covered with dry pollution

[0111] A layer of dirt with a thickness of 1 mm is evenly covered on the surface of the insulator shed. Figure 5 First, assume that the dirt is dry dirt, and its specific parameters are shown in Table 2.

[0112] Observe the electric field distribution line diagram along the surface of the umbrella skirt when the dirty layer is dry dirt, such as Figure 6 As shown in the figure, it can be seen that the electric field strength is the largest at the No. 1 shed, with the extreme value reaching 29.05kV / cm, and the electric field distortion rate is 29.92%, which is a medium risk. The closer to the two ends, the more serious the impact of pollution on the insulator field strength.

[0113] Compared with the clean insulator, Figure 7 shown.

[0114] It can be seen that in the dry-contaminated state, the overall electric field distribution of the insulator is similar to that in the clean state, and is approximately symmetrically distributed, with high ends and low in the middle.

[0115] 2.1.3 Distribution of electric field along the surface of insulator when it is covered with wet dirt

[0116] Assume that the dirt is wet dirt, and the specific parameters are shown in Table 2. The calculation results are as follows Figure 8 shown.

[0117] Compared with the clean insulator, Fig. 9 shown.

[0118] It can be seen that when the surface is covered with wet dirt, the extreme field strength still appears at the tip of the No. 1 shed, reaching 36.06 kV / cm, which is 13.70 kV / cm higher than the maximum field strength when clean. The electric field distortion rate is 61.27%. At this time, the risk level is dangerous and the electrical insulator needs to be cleaned immediately.

[0119] 2.1.4 Comparative analysis of clean, dry-contaminated and wet-contaminated field strength of insulators

[0120] In order to more intuitively compare the changes in the field strength along the surface of the insulator when it is clean, covered with dry dirt, and covered with wet dirt. The electric field strength along the surface of the insulator when it is clean, dry dirt, and wet dirt is compared together, such as Fig.10 Observe the change of the electric field strength of No. 1 shed.

[0121] The maximum electric field strength of some sheds is taken as a comparison to calculate the field strength change, as shown in Table 3.

[0122] Table 3 Comparison of the maximum field strength of some sheds

[0123]

[0124] It can be seen that when the surface is covered with dirt, the electric field strength change value at the No. 1 shed is the largest. At the No. 1 shed, when the insulator surface is covered with dry dirt, the electric field distortion rate is 29.92%; when the insulator surface is covered with wet dirt, the electric field distortion rate reaches 61.27%.

[0125] 2.2 Field strength analysis of the No. 1 shed when the upper surface is wet and dirty

[0126] From the analysis in 2.1, it can be seen that when the shed is polluted, the closer to the two end fittings, especially the closer to the high-voltage end, the greater the distortion of the electric field strength, and the pollution has the greatest impact on the No. 1 shed. Moreover, compared with dry pollution, the field strength distortion of the No. 1 shed is greater when wet pollution occurs. In order to simulate the most stringent conditions in actual operation, the subsequent analysis focuses on the situation of wet pollution attached to the surface of the No. 1 shed, and compares and analyzes the changes and laws of the electric field distribution when the pollution coverage and position are different.

[0127] 2.2.1 Analysis of different wet dirt coverage

[0128] The surface of the No. 1 shed is covered with wet dirt with a thickness of 1 mm. The dirt is set to be fully covered, 2 / 3 covered, and 1 / 3 covered respectively. The model diagram is as follows Fig.11 shown.

[0129] Calculate the changes in the electric field along the surface of shed No. 1 in three cases respectively.

[0130] The electric field intensity distribution diagrams of the three cases are shown in Fig.12 shown.

[0131] In order to more intuitively compare the changes in the electric field intensity along the surface of No. 1 shed when the pollution is fully covered, 2 / 3 of the range is covered, and 1 / 3 of the range is covered. Fig.13 As shown, the electric field intensity distribution diagrams of the three cases are put together for comparative analysis.

[0132] It can be seen that when the surface of the No. 1 shed is completely covered with dirt, the maximum electric field strength is 36.02kV / cm; when the dirt covers 2 / 3 of the range, the maximum electric field strength is 33.12kV / cm; when the dirt covers 1 / 3 of the range, the maximum electric field strength is 27.24kV / cm. It can be seen from 3.1.1 that the maximum electric field strength of the No. 1 shed of the insulator is 22.36kV / cm when it is clean.

[0133] Compared with the clean surface of the insulator, the field strength changes when the No. 1 shed is fully covered by dirt, 2 / 3 of the area is covered by dirt, and 1 / 3 of the area is covered by dirt are shown in Table 4.

[0134] Table 4 Comparison of maximum field strength at different coverage areas

[0135]

[0136] It can be seen that the greater the coverage of dirt on the upper surface of the shed skirt, the greater the change in field strength. Compared with the clean state, the electric field distortion rate is 61.09% when the dirt is fully covered. At this time, the risk level is dangerous, and the insulator should be washed with live water immediately; when the dirt coverage is 2 / 3, the electric field distortion rate is 48.12%, and the risk level is high risk. The insulator should be cleaned as soon as possible; when the dirt coverage is 1 / 3, the electric field distortion rate is 21.82%, and the risk level is medium risk and close to low risk. The insulator should be cleaned according to operation and maintenance needs.

[0137] The electric field distortion rate and the corresponding risk level when the pollution coverage is different are more intuitively shown in Table 5:

[0138] Table 5 Electric field distortion rate and corresponding risk level for different coverage areas

[0139]

[0140] 2.2.2 Analysis of different wet dirt coverage locations

[0141] On the upper surface of the No. 1 shed, wet dirt with a thickness of 1 mm and the same coverage is placed on the front, middle and rear sections of the shed. Fig.14 shown.

[0142] For the above three models, the electric field intensity distribution curves along the surface of No. 1 shed are calculated under the three types of pollution coverage. The field intensity distribution is shown in Fig.15 shown.

[0143] In order to more intuitively observe the changing trend of the electric field intensity along the surface when the dirt covers the front, middle and rear sections of the upper surface of the No. 1 shed, the electric field intensity distribution diagrams at different dirt coverage positions are compared together, such as Fig.16 shown.

[0144] It can be seen that when the dirt covers the front section of the upper surface of the No. 1 shed, the maximum value of the electric field strength is 27.24kV / cm; when the dirt covers the middle section, the maximum value of the electric field strength is 24.98kV / cm; when the dirt covers the rear section, the maximum value of the electric field strength is 23.68kV / cm. Compared with the clean state, the field strength changes when the dirt covers the front section, middle section, and rear section are shown in Table 6.

[0145] Table 6 Comparison of maximum field strength at different coverage locations

[0146]

[0147] Compared with the clean state, when the dirt covers the front section, the electric field distortion rate is 21.82%, and the risk level is medium risk at this time, which has little impact on the insulator electric field; when the dirt covers the middle section, the electric field distortion rate is 11.72%, and the risk level is low risk at this time; when the dirt covers the rear section, the electric field distortion rate is 5.90%, and the risk level is low risk at this time, and the insulator does not need to be cleaned. It can be seen that the closer the dirt coverage position on the upper surface of the shed is to the edge of the shed, the greater the field strength distortion. When the dirt is in the rear section, the impact on the insulator electric field is small.

[0148] The electric field distortion rate and the corresponding risk level when the pollution coverage is different are more intuitively shown in Table 7:

[0149]

[0150] Based on finite element simulation, the coverage range and coverage position of the surface contamination of the FZ-110 / 5 composite post insulator shed were studied, and the following conclusions were drawn:

[0151] (1) The electric field distribution along the insulator surface is approximately symmetrical. The electric field strength is larger near the sheds of the hardware on both sides, making it more prone to flashover. When the surface of the insulator is covered with dirt, the field strength of the insulator will increase. At the shed No. 1, the field strength distortion is the most serious. Since wet dirt has better conductivity, the field strength distortion caused by wet dirt is greater than that caused by dry dirt.

[0152] (2) At the No. 1 shed, the larger the dirt coverage on the shed surface, the greater the field strength distortion along the shed surface.

[0153] (3) At the No. 1 shed, the closer the dirt coverage position on the shed is to the shed edge, the greater the distortion of the field strength along the shed. When the dirt covers the rear section of the shed, the effect on the shed field strength is small.

[0154] (4) At the No. 1 shed, when the upper surface of the shed is fully covered with wet dirt, the electric field distortion rate is 61.09%. At this time, the risk level is dangerous, and the insulator should be immediately washed with live water; when the wet dirt covers 2 / 3, the electric field distortion rate is 48.12%. At this time, the risk level is high risk, and the insulator should be cleaned as soon as possible; when the wet dirt covers 1 / 3, the electric field distortion rate is 21.82%. At this time, the risk level is medium risk and close to low risk, and the insulator should be cleaned as needed.

[0155] (5) At the No. 1 shed, when the wet dirt covers the front section of the upper surface of the shed, the electric field distortion rate is 21.82%. At this time, the risk level is medium risk, and the impact on the insulator electric field is small; when the wet dirt covers the middle section, the electric field distortion rate is 11.72%, and the risk level is low risk; when the wet dirt covers the rear section, the electric field distortion rate is 5.90%, and the risk level is low risk, and the insulator does not need to be cleaned.

[0156] Therefore, when cleaning the insulator, the sheds near the high-voltage end and the grounding end are cleaned first; since the dirt at the rear of the shed has little effect on the field strength of the insulator, the dirt near the edge of the shed is cleaned first. This invention is conducive to the scientific formulation of the live water washing strategy for insulators and can improve the daily operation and maintenance efficiency of insulators.

[0157] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for analyzing the electric field of a composite post insulator under different pollution forms, characterized in that: Applying a rated voltage of 110 kV to the composite post insulator, the finite element method is used for calculation and analysis, which specifically includes the following steps: Step 1: Analyze the differences in electric field characteristics when the composite post insulator is clean, covered with dry pollution, and covered with wet pollution, and find the shed that is most seriously affected by pollution; First, the electric field intensity distribution along the surface of the composite insulator under clean conditions is calculated; then, all surfaces of the insulator sheds are evenly covered with dirt, and the dirt is defined as dry dirt and wet dirt in turn, and the electric field intensity distribution along the surface of the insulator under dry dirt and wet dirt conditions is calculated respectively; compared with the electric field intensity distribution when clean, the shed most seriously affected by dirt is found; then, the change in the magnitude of the electric field intensity is calculated and analyzed when the scope and position of dirt accumulation on the surface of this shed changes; Step 2, applying wet dirt with different coverage ranges and different positions on the upper surface of the shed of the composite post insulator in sequence, and analyzing the influence of the dirt coverage range and dirt coverage position on the upper surface of the shed on the electric field characteristics of the insulator; The thickness and state of the pollution on the upper surface of the shed are the same, and the changes in the field strength along the surface of the insulator are analyzed when the upper surface of the shed is completely covered with pollution, 2 / 3 of the upper surface is covered with pollution, and 1 / 3 of the upper surface is covered with pollution; The pollution with the same coverage range and the same state on the upper surface of the shed is analyzed, and the changes of the electric field along the surface of the insulator are analyzed when the pollution covers the front end, the middle end and the rear end of the upper surface of the shed respectively.

2. The electric field analysis method of the composite post insulator under different pollution forms according to claim 1 is characterized in that: The composite post insulator has a total of 25 sheds, one large shed and two small sheds arranged in sequence, from the high voltage end to the grounding end, and the sheds are marked as No. 1 to No. 25 sheds.

3. The electric field analysis method of the composite post insulator under different pollution forms according to claim 1 is characterized in that: The shed material of the composite post insulator is silicone rubber, with a rated voltage of 110kV. In the simulation calculation, a high potential is applied The electric potential and the electric field frequency are 50 Hz, and the current field module is used in COMSOL to calculate.

4. The electric field analysis method of the composite post insulator under different pollution forms according to claim 1 is characterized in that: The dirt on the surface of the insulator is set to a uniform dirt layer of 1mm.

5. The electric field analysis method of the composite post insulator under different pollution forms according to claim 1 is characterized in that: Reflect the change of electric field and define the electric field distortion rate α: α=(e Δ / e0)×100=(1 e Δ =he t -e0 (2) where e t is the peak value of field strength when a shed is polluted, e0 is the peak value of field strength when the shed is clean, and e Δ is the change in electric field intensity when the shed is contaminated compared to when it is clean.

6. The electric field analysis method of composite post insulator under different pollution forms according to claim 1, characterized in that: The electric field distribution along the surface of the insulator is approximately symmetrical. The electric field strength is relatively large near the sheds of the hardware on both sides, and pollution flashover is prone to occur. When the surface of the insulator is covered with dirt, the field strength of the insulator will increase. At the No. 1 shed, the field strength distortion is the most serious. Since wet dirt has better conductivity, the field strength distortion caused by wet dirt is greater than that caused by dry dirt.

7. The electric field analysis method of the composite post insulator under different pollution forms according to claim 1 is characterized in that: At the No. 1 shed, the larger the coverage of dirt on the shed surface, the greater the field strength distortion along the shed surface; At the No. 1 shed, the closer the dirt coverage position on the shed upper surface is to the shed edge, the greater the field strength distortion along the shed surface; when the dirt covers the rear section of the shed, it has little effect on the shed field strength. At the No. 1 shed, the electric field distortion rate is 61.09% when the upper surface of the shed is fully covered with wet dirt. At this time, the risk level is dangerous, and the insulator should be immediately washed with live water; When the wet pollution coverage is 2 / 3, the electric field distortion rate is 48.12%. At this time, the risk level is high risk and the insulators should be cleaned as soon as possible; when the wet pollution coverage is 1 / 3, the electric field distortion rate is 21.82%. At this time, the risk level is medium risk and close to low risk. The insulators should be cleaned as needed. At the No. 1 shed, when the wet dirt on the upper surface of the shed covers the front section, the electric field distortion rate is 21.82%. At this time, the risk level is medium risk, and the impact on the insulator electric field is small; when the wet dirt covers the middle section, the electric field distortion rate is 11.72%, and the risk level is low risk; when the wet dirt covers the rear section, the electric field distortion rate is 5.90%, and the risk level is low risk, and the insulator does not need to be cleaned.

8. The electric field analysis system of a composite post insulator under different pollution forms and the electric field analysis method of a composite post insulator under different pollution forms according to any one of claims 1 to 7, characterized in that: include: The shed determination module analyzes the differences in the electric field characteristics of the composite post insulator when it is clean, covered with dry pollution, and covered with wet pollution, and finds the shed that is most seriously affected by pollution; An electric field characteristic analysis module sequentially applies wet stains with different coverage ranges and positions on the upper surface of the shed of the composite post insulator; Analyze the influence of the pollution coverage range and pollution coverage position on the shed surface on the electric field characteristics of the insulator. The risk assessment module calculates the electric field distortion rate under different pollution conditions, and rates the risk of flashover according to the magnitude of the electric field distortion rate. Four levels of insulator flashover risk are defined. When the electric field distortion rate is greater than 50%, the risk level is dangerous; when the electric field distortion rate is between 50% and 35%, the risk level is high risk; when the electric field distortion rate is between 35% and 20%, the risk level is medium risk; when the electric field distortion rate is between 20% and 10%, the risk level is low risk; when the electric field distortion rate is less than 10%, it is defined as low risk.

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