Power transmission tower ground potential side flashover prevention structure and construction method thereof

Abstract

The present application relates to the technical field of power transmission tower, and discloses a power transmission tower ground potential side anti-flashover structure and a construction method thereof.The first insulating coating, the umbrella skirt and the second insulating coating are matched to form a continuous closed protection whole.The first insulating coating is coated on the surface of the base material to provide basic insulation protection; the umbrella skirts are arranged along the length direction of the base material at intervals to increase the surface creepage distance; the second insulating coating continuously covers the surface of the umbrella skirt, the assembly gap between the umbrella skirt and the first insulating coating and the outer surface of the first insulating coating, closes the assembly gap, prevents the accumulation of dirt and moisture in the gap, and simultaneously fixes the umbrella skirt at the installation position, so that the umbrella skirt is not easy to be loosened or warped under the wind vibration or temperature change.The present application can avoid the assembly part of the umbrella skirt from becoming a flashover hidden danger due to the accumulation of dirt in the gap, ensure that the ground potential side of the power transmission tower maintains stable insulation performance, and reduce the risk of flashover discharge.

Description

Technical Field

[0001] This invention relates to the field of power transmission tower technology, and in particular to a flashover prevention structure on the ground potential side of a power transmission tower and its construction method. Background Technology

[0002] The ground potential side of transmission towers (including crossarms and tower body) is a critical protection area in the power system, and its insulation performance directly affects the safe and stable operation of transmission lines. Anti-flashover structures need to be installed on the ground potential side of transmission towers to increase creepage distances and block arc conduction, thereby preventing flashover discharge accidents under complex climatic conditions such as humidity, salt spray, and condensation.

[0003] Chinese patent CN205822908U discloses a composite crossarm, comprising: a body (i.e., a substrate) and an insulating layer. The insulating layer covers at least a portion of the body. The insulating layer can be a skirt. The skirt can increase the creepage distance to a certain extent. However, the skirt is sleeved and installed on the body. The interfacial bonding between the skirt and the body is relatively weak. With long-term use, it is easily affected by wind vibration and temperature changes, which can cause the skirt to loosen and fall off. In addition, there are gaps at the assembly parts of the skirt and the substrate. These gaps can easily accumulate dirt and moisture, thus becoming a flashover hazard. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a flashover prevention structure on the ground potential side of the transmission tower and its construction method that can prevent flashover hazards caused by dirt accumulation in the gaps of the umbrella skirt assembly area.

[0005] To solve the above-mentioned technical problems, the present invention provides a flashover prevention structure on the ground potential side of a transmission tower, comprising: Substrate; A first insulating coating is applied to the surface of the substrate; A multiple umbrella skirt is fitted onto the substrate and is spaced apart along the length of the substrate. And a second insulating coating, which continuously covers the surface of the umbrella skirt, the assembly gap between the umbrella skirt and the first insulating coating, and the outer surface of the first insulating coating; The radius of the umbrella skirt is 75mm-100mm, and the distance between two adjacent umbrella skirts is 100mm-200mm.

[0006] As a preferred embodiment of the present invention, the base material is angle steel, and the umbrella skirt includes a first part and a second part. The first part is a fan-shaped structure with a notch and a central angle greater than 180 degrees. The notch fits with the outer surface of the base material. The second part is a fan-shaped structure with a angle less than 180 degrees and has an edge. The second part is embedded in the notch, and the edge fits with the inner surface of the base material. The first part and the second part are connected by a connector so that the first part and the second part clamp the base material.

[0007] As a preferred embodiment of the present invention, the first split body has a first connecting plate axially protruding from the two sides of the notch. The first connecting plate is attached to the outer surface of the substrate. The two ends of the first connecting plate are respectively provided with a first connecting portion extending out of the substrate along the width direction of the substrate. The edge of the second split body has a second connecting plate axially protruding from the second split body. The second connecting plate is attached to the inner surface of the substrate. The two ends of the second connecting plate are respectively provided with a second connecting portion extending out of the substrate along the width direction of the substrate. The first connecting portion and the second connecting portion correspond one-to-one and are arranged opposite to each other. The oppositely arranged first connecting portion and second connecting portion are connected by the connector. The second insulating coating continuously covers the assembly gap between the first connecting plate and the outer surface of the substrate and the assembly gap between the second connecting plate and the inner surface of the substrate.

[0008] As a preferred embodiment of the present invention, the first connecting portion and the second connecting portion, which are disposed opposite to each other, are respectively provided with through holes for the connecting member to pass through.

[0009] As a preferred embodiment of the present invention, the second insulating coating also continuously covers the assembly gap between the connector and the through hole.

[0010] As a preferred embodiment of the present invention, the thickness of the first insulating coating is 3.5mm-7.5mm, and the thickness of the second insulating coating is 0.5mm-1mm.

[0011] As a preferred embodiment of the present invention, the wind deflection verification point on the ground potential side of the transmission tower is located on the surface of the substrate. At least two sets of spaced-apart skirts are provided on the first insulating coating. Each skirt set includes multiple skirts spaced-apart along the length direction of the substrate. The distance between the skirt set and the wind deflection verification point is greater than 0.5m.

[0012] Meanwhile, the present invention also provides a construction method for an anti-flashover structure on the ground potential side of a transmission tower, comprising the following steps: S1: Spray insulating material onto the surface of the substrate to form a first insulating coating; S2: Install umbrella skirts on the substrate, wherein the umbrella skirts are fitted onto the substrate, and there are multiple umbrella skirts, which are spaced apart along the length direction of the substrate; S3: Spray insulating material onto the surface of the umbrella skirt and the outer surface of the first insulating coating to form a second insulating coating. The second insulating coating continuously covers the surface of the umbrella skirt, the assembly gap between the umbrella skirt and the first insulating coating, and the outer surface of the first insulating coating.

[0013] As a preferred embodiment of the present invention, in S1 and S3, the insulating material is formed by mixing an isocyanate component and an amine chain extender component in a 1:1 volume ratio.

[0014] As a preferred embodiment of the present invention, before S1, the method further includes: S0: removing the umbrella skirts on the surface of the substrate on the old transmission tower and cleaning the surface of the substrate.

[0015] This invention discloses a flashover prevention structure and construction method for the ground potential side of a transmission tower. Compared with existing technologies, its advantages lie in the following: This invention forms a continuous and closed protective structure through the cooperation of a first insulating coating, skirts, and a second insulating coating. By using skirts of specific sizes in conjunction with the first and second insulating coatings, the creepage distance is effectively increased, bridging between skirts is prevented, flashover hazards caused by assembly gaps are eliminated, and the long-term stability of the skirts is strengthened. Specifically, the first insulating coating covers the surface of the substrate, providing basic insulation protection; multiple skirts are spaced apart along the length of the substrate to increase the surface creepage distance; the second insulating coating continuously covers the surface of the skirts, the assembly gaps between the skirts and the first insulating coating, and the outer surface of the first insulating coating, sealing the assembly gaps, preventing the accumulation of dirt and moisture inside the gaps, and simultaneously securing the skirts to the installation position, making them less prone to loosening or warping under wind vibration or temperature changes. This invention can ensure stable insulation performance on the ground potential side of the transmission tower, reducing the risk of flashover discharge. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a flashover prevention structure on the ground potential side of a power transmission tower provided by the present invention; Figure 2 yes Figure 1 Enlarged view of point A; Figure 3 This is a connection structure diagram of the umbrella skirt, the first insulating coating, and the substrate of the present invention; Figure 4 This is a structural diagram of the first component of the present invention; Figure 5 This is a structural diagram of the second component of the present invention; In the figure, substrate 1; first insulating coating 2; umbrella skirt 3; first split 31; notch 311; second split 32; edge 321; first connecting plate 33; first connecting part 331; second connecting plate 34; second connecting part 341; through hole 35; second insulating coating 4; umbrella skirt assembly 5; wind deflection check point 6. Detailed Implementation

[0017] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0018] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are used only for the convenience of describing the invention and for simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0019] like Figure 1-2 As shown in the preferred embodiment of the present invention, a flashover prevention structure on the ground potential side of a transmission tower is provided. It should be noted that the area near the wind deflection check point on the ground potential side of the transmission tower is a section with relatively tight air gaps between the conductor and the transmission tower. Under polluted and damp conditions, the risk of surface flashover is high. Therefore, the flashover prevention structure is mainly arranged in this area (such as at the connection between the crossarm or the tower body and the crossarm). This flashover prevention structure includes: a substrate 1, a first insulating coating 2, a skirt 3, and a second insulating coating 4. The first insulating coating 2 covers the surface of the substrate 1; the skirt 3 is fitted onto the substrate 1 (specifically, onto the first insulating coating 2 on the surface of the substrate 1). Multiple skirts 3 are provided, spaced apart along the length of the substrate 1. The material of the skirt 3 can be EPDM rubber or fluororubber, ensuring that its tensile strength, UV aging resistance, etc., meet the standards; the second insulating coating 4 continuously covers the surface of the skirt 3, the assembly gap between the skirt 3 and the first insulating coating 2, and the outer surface of the first insulating coating 2.

[0020] The radius R of the umbrella skirt is 75mm-100mm. Within this range, the creepage distance can be effectively increased without significantly increasing the wind-exposed area of ​​the component, thus avoiding excessive wind load on the substrate 1. The spacing S between two adjacent umbrella skirts 3 is 100mm-200mm. Within this range, rainwater or snow can prevent overlap between the edges of adjacent umbrella skirts 3. If the spacing is too small, rainwater can easily form water columns, directly bridging adjacent umbrella skirts 3, thereby shortening the creepage path. Furthermore, when spraying the second insulating coating 4, the spray gun may have difficulty covering the narrow area between two adjacent umbrella skirts 3, easily causing missed spraying or uneven coating thickness. If the spacing is too large, the number of umbrella skirts 3 that can be arranged on a unit length of substrate 1 will decrease, and the anti-flashover effect will be weakened accordingly.

[0021] The working principle of this anti-flashover structure is as follows: The first insulating coating 2 is mainly responsible for isolating the substrate 1 from the external environment, thereby providing basic insulation protection. The setting of the umbrella skirt 3 can effectively increase the creepage distance on the surface and improve the anti-flashover capability. The radius R of the umbrella skirt 3 is 75mm-100mm, and the distance S between two adjacent umbrella skirts 3 is 100mm-200mm. The above radius and distance range can achieve a good balance between creepage distance, anti-bridging capability, and wind resistance load. At the same time, this distance also facilitates the spraying operation, so that the entire structure maintains a relatively stable protective state. This structure, through the cooperation of umbrella skirts of specific sizes with the first insulating coating and the second insulating coating, effectively increases the creepage distance, prevents bridging between umbrella skirts, eliminates the flashover risk caused by assembly gaps, and strengthens the long-term stability of the umbrella skirts. Specifically, the second insulating coating 4 continuously covers the surface of the umbrella skirt 3 and the exposed outer surface of the first insulating coating 2, especially sealing the gaps at the assembly parts of the umbrella skirt 3 and the first insulating coating 2, thereby preventing the accumulation of dirt and moisture inside the gaps. Meanwhile, the second insulating coating 4 adheres tightly to the outside of the umbrella skirt 3 and the first insulating coating 2, firmly securing the umbrella skirt 3 to its installation position. Even if the substrate 1 experiences vibration due to wind or thermal expansion and contraction due to day-night temperature differences, the umbrella skirt 3 is not prone to loosening or curling at the edges, and the interface is less likely to experience minor peeling. The first insulating coating 2, the umbrella skirt 3, and the second insulating coating 4 of this anti-flashover structure are connected to form a relatively seamless protective whole, which adheres to the surface of the substrate 1, maintaining stable insulation performance on the ground potential side of the transmission tower and reducing the risk of flashover discharge.

[0022] For example, see Figure 3The base material 1 is angle steel. The umbrella skirt 3 includes a first part 31 and a second part 32. The first part 31 is a fan-shaped structure with a notch 311 and a central angle greater than 180 degrees. The notch 311 fits with the outer surface of the base material 1. The second part 32 is a fan-shaped structure with an angle less than 180 degrees and has a side 321. The second part 32 is embedded in the notch 311, and the side 321 fits with the inner surface of the base material 1. The first part 31 and the second part 32 are connected by a connector (not shown in the figure) so that the first part 31 and the second part 32 clamp the base material 1. The notch 311 of the first part 31 is tightly fitted to the first insulating coating 2 covering the outer surface of the base material 1. The side 321 of the second part 32 is tightly fitted to the first insulating coating 2 covering the inner surface of the base material 1, which facilitates the assembly and positioning of the first part 31 and the second part 32. The first part 31 and the second part 32 are connected by a connector to fix the umbrella skirt 3. The installation is simple. After the first part 31 and the second part 32 are installed on the substrate 1, an insulating coating 4 is formed by spraying insulating material. The second insulating coating 4 can firmly fix the umbrella skirt 3 of the split structure to the substrate 1, so that the umbrella skirt 3 is not easy to loosen or curl under wind vibration or temperature change. This allows the umbrella skirt 3 to work stably on the angle steel structure substrate 1 and reduces the risk of flashover discharge.

[0023] Furthermore, the connection between the first component 31 and the second component 32 is located at the end of the substrate 1, thus offsetting the assembly gap between the first component 31 and the second component 32 from the edge of the substrate 1 (the intersection line of the two limbs of the angle steel). This is because the edge of the angle steel is a location where the electric field is concentrated. If the assembly gap is located here, and the second insulating coating 4 ages and cracks during long-term operation, this assembly gap will be directly exposed to a high electric field environment, increasing the risk of breakdown. By moving the assembly gap between the first component 31 and the second component 32 to the end of the substrate 1 (the plane of the angle steel's limbs), the assembly gap is located in a flat area with a more uniform electric field distribution. Even if the coating is accidentally damaged here, the assembly gap is exposed to a weaker electric field, relatively reducing the probability of breakdown.

[0024] For example, see Figure 3-5The first segment 31 has a first connecting plate 33 axially protruding from the two sides of the notch 311. The first connecting plate 33 is attached to the outer surface of the substrate 1. The two ends of the first connecting plate 33 are respectively provided with a first connecting part 331 extending out of the substrate 1 along the width direction of the substrate 1. The edge 321 of the second segment 32 has a second connecting plate 34 axially protruding from the second segment 32. The second connecting plate 34 is attached to the inner surface of the substrate 1. The two ends of the second connecting plate 34 are respectively provided with a second connecting part 341 extending out of the substrate 1 along the width direction of the substrate 1. The first connecting part 331 and the second connecting part 341 correspond one to one and are arranged opposite each other. The oppositely arranged first connecting part 331 and second connecting part 341 are connected by a connector. The second insulating coating 4 continuously covers the assembly gap between the first connecting plate 33 and the outer surface of the substrate 1 and the assembly gap between the second connecting plate 34 and the inner surface of the substrate 1.

[0025] The first connecting plate 33 increases the contact area between the first split 31 and the outer surface of the substrate 1 (corresponding to the first insulating coating 2). The second connecting plate 34 increases the contact area between the second split 32 and the inner surface of the substrate 1 (corresponding to the first insulating coating 2). The clamping force of the first split 31 and the second split 32 on the substrate 1 is distributed and transmitted to the substrate 1 through the surfaces of the first connecting plate 33 and the second connecting plate 34, making the umbrella skirt 3 more stable and preventing damage to the first insulating coating 2 due to excessive local stress during assembly. The first connecting part 331 and the second connecting part 341 extend beyond the substrate 1, providing assembly space for the connectors. The connectors are assembled on the outer edge of the substrate 1 without drilling holes in the substrate 1, ensuring the integrity of the first insulating coating 2. The second insulating coating 4 seals the assembly gap between the connecting plate and the substrate, preventing dirt and moisture from entering and avoiding creepage caused by dirt accumulation in the gap. At the same time, the coating strengthens the bonding between the connecting plate and the substrate, effectively preventing the connecting plate from loosening under vibration and temperature difference, and maintaining long-term stable protective performance.

[0026] For example, see Figure 3-5 The first connecting portion 331 and the second connecting portion 341, which are arranged opposite to each other, are respectively provided with through holes 35 for the connector to pass through. The through holes 35 provide a passage for the connector. After the connector (such as a cable tie) passes through the through holes 35, the first connecting portion 331 and the second connecting portion 341 are locked, which is simple to operate. In this embodiment, the second insulating coating 4 also continuously covers the assembly gap between the connector and the through hole 35. The second insulating coating 4 seals the gap, which can prevent dirt and moisture from seeping into the inner wall of the through hole 35 and eliminate the creepage shortcut that may be formed at the through hole 35. At the same time, the cured coating penetrates into the tiny gap between the through hole and the connector, and bonds the connector to the inner wall of the through hole 35, which plays an auxiliary role in fixing the connector and reduces the risk of it loosening or slipping under wind vibration.

[0027] For example, the thickness of the first insulating coating 2 is 3.5mm-7.5mm. As a basic insulating layer, the first insulating coating 2 provides initial isolation between the substrate 1 and the external environment. Its main function is to provide sufficient withstand voltage breakdown capability. Its thickness is adapted to the voltage level, ranging from 3.5mm to 7.5mm, with 3.5mm for 110kV and 7.5mm for 220kV. Its breakdown strength is ≥20kV / mm, meeting the usage requirements. The thickness of the second insulating coating 4 is 0.5mm-1mm. The second insulating coating 4 mainly serves as a surface sealing layer. This thickness range can cover the small gaps at the base of the umbrella skirt 3 without altering the geometry of the umbrella skirt 3 itself. In this embodiment, the thickness of the first insulating coating 2 and the second insulating coating 4 is measured using vernier calipers. Specifically, at least five key measuring points are selected at the ends, corners, connection points, and the center of the sprayed area of ​​the substrate 1. The dimensions of each key measuring point are measured before spraying, after the first insulating coating 2 has cured, and after the second insulating coating 4 has cured. The thickness of the first insulating coating 2 is defined as the difference between the measured dimensions after curing and before spraying; the thickness of the second insulating coating 4 is defined as the difference between the measured dimensions after curing and after curing the first insulating coating 2. To reduce error, each key measuring point is measured three times consecutively, and the average value is taken. The arithmetic mean of the thickness calculation results of each key measuring point is then taken as the actual thickness of the corresponding insulating coating.

[0028] For example, see Figure 1 The wind deflection check point 6 on the ground potential side of the transmission tower is located on the surface of the substrate 1. At least two sets of spaced-apart skirt groups 5 are provided on the first insulating coating 2. Each skirt group 5 includes multiple skirts 3 spaced along the length of the substrate 1. The distance L between the skirt group 5 and the wind deflection check point 6 is greater than 0.5m. In strong winds, the transmission conductor will sway to a certain extent. The wind deflection check point is usually a dangerous location where the conductor may approach the ground potential side of the transmission tower during swaying. The skirts 3 are solid insulators protruding from the surface of the substrate 1. If the skirts 3 are too close to the check point (distance less than or equal to 0.5m), discharge tips can easily form on the outer edge of the skirts, leading to surface flashover or air gap breakdown at smaller wind deflection angles. A distance greater than 0.5m is maintained to ensure that, under wind deflection conditions, the discharge channel is still controlled by the originally designed pure air gap, ensuring the overall safe operation of the power grid.

[0029] In addition, the construction method of the above-mentioned anti-flashover structure on the ground potential side of the transmission tower includes the following steps: S1: Spray insulating material onto the surface of the substrate to form the first insulating coating. Before application, clean the substrate surface to remove rust, oil, and dust, ensuring good adhesion of the insulating material. During spraying, maintain an appropriate distance between the spray gun and the substrate surface, moving it at a uniform speed to evenly cover the substrate surface with the insulating material. The first insulating coating isolates the substrate from the external environment, providing a smooth and insulating base for subsequent umbrella skirt installation. After the coating has cured, the operator should touch the surface to check for complete drying, no missed areas or runs, and that the thickness of the first insulating coating meets requirements before proceeding to the next step.

[0030] S2: Install umbrella skirts on the substrate, wherein the umbrella skirts are fitted onto the substrate (specifically onto the first insulating coating on the surface of the substrate), and multiple umbrella skirts are provided, which are spaced apart along the length of the substrate; after the first insulating coating has cured, the construction personnel mark the installation position of each umbrella skirt on the surface of the first insulating coating according to the design drawings, ensuring that the spacing between adjacent umbrella skirts meets the requirements, and then install the umbrella skirts one by one in their corresponding installation positions.

[0031] S3: Apply insulating material to the surface of the umbrella skirt and the outer surface of the first insulating coating (i.e., the exposed surface not covered by the umbrella skirt) to form a continuous second insulating coating. This second insulating coating continuously covers the surface of the umbrella skirt, the assembly seams between the umbrella skirt and the first insulating coating, and the outer surface of the first insulating coating. After all the umbrella skirts are installed, the workers perform a second cleaning of the sprayed area, wiping away any dust that may be adhering to the surface of the umbrella skirt and the outer surface of the first insulating coating with a dry cloth. During spraying, the spray gun continuously sprays the surface of the umbrella skirt, the seams between the umbrella skirt root and the first insulating coating, and the exposed areas of the first insulating coating not covered by the umbrella skirt. The insulating material covers the tiny assembly seams at the base of the umbrella skirt, while simultaneously spreading on the surface of the umbrella skirt and the outer surface of the first insulating coating to form the second insulating coating. The second insulating coating connects the umbrella skirt and the first insulating coating into a continuous, closed protective unit. The workers check the coverage of the second insulating coating, confirming that all seams are covered, there are no missed areas or thin spots, and the thickness of the second insulating coating meets the requirements, thus forming a complete flashover protection structure.

[0032] This construction method involves first spraying a first insulating coating, then installing the umbrella skirt, and finally spraying a second insulating coating, creating a relatively seamless connection between the first, umbrella skirt, and second insulating coatings. The assembly gap between the umbrella skirt base and the first insulating coating is sealed by the second insulating coating, preventing dirt and moisture from easily seeping into the interior and avoiding weak points for flashover due to accumulated dirt. Simultaneously, the second insulating coating adheres tightly to the surface of the umbrella skirt and the outer surface of the first insulating coating, firmly securing the umbrella skirt to its installation position. Even when the substrate vibrates due to wind or experiences thermal expansion and contraction due to diurnal temperature variations, the umbrella skirt is less likely to loosen or warp, and minor peeling at the interface is less likely to occur. This structure ensures stable insulation performance on the ground potential side of the transmission tower, reducing the risk of flashover discharge.

[0033] For example, in S1 and S3, the insulating material is prepared by mixing an isocyanate component and an amine chain extender component in a 1:1 volume ratio. This insulating material possesses good insulation properties, hydrophobic properties, and anti-aging capabilities. Furthermore, the insulating material can quickly solidify after spraying, making it less prone to sagging on the substrate surface.

[0034] Furthermore, some existing technologies involve injection molding the umbrella skirt onto the substrate. While this method avoids assembly gaps between the umbrella skirt and the substrate, it is relatively complex and cannot be used on transmission towers, making it unsuitable for retrofitting existing transmission towers. This new method, however, involves spraying to form a first and second insulating coating, and the umbrella skirt uses a split installation structure. Therefore, it can be applied to the substrate of existing transmission towers without removing the existing substrate.

[0035] When this construction method is used to treat old transmission towers, before S1, it also includes: S0: Removing the umbrella skirts on the surface of the base material of the old transmission tower and cleaning the surface of the base material. In the flashover protection structure of the old transmission tower, the umbrella skirts are directly fitted onto the base material, and there are often gaps between the umbrella skirts and the base material. After long-term operation, dirt and moisture easily accumulate in the gaps. The construction personnel first remove the old umbrella skirts one by one. Then, the surface of the base material is cleaned to remove the original residual old coating, rust, oil stains, and accumulated dust. During cleaning, the present invention can use grinding or sandblasting to restore the surface of the base material to clean and have a certain roughness, providing a good adhesion base for the subsequent spraying of the first insulating coating. After cleaning, the construction personnel wipe off the surface dust with a dry cloth, confirm that the surface of the base material is dry and free of oil stains, and then proceed to the next step. It is understood that, in order to ensure the safety of the construction operation, the operation needs to be carried out in a state of power outage.

[0036] This method first removes the existing umbrella skirt and cleans the substrate surface, then sprays a first insulating coating, installs a new umbrella skirt, and finally sprays a second insulating coating to form a continuous, sealed protective structure. After treatment, the gaps caused by the umbrella skirt directly fitting onto the substrate in the original structure no longer exist. The assembly gap between the new umbrella skirt and the first insulating coating is covered and sealed by the second insulating coating, making it difficult for dirt and moisture to enter the interface, thus improving the problem of flashover weak points caused by dirt accumulation in the gaps. At the same time, the second insulating coating bonds the umbrella skirt and the first insulating coating together, making the umbrella skirt less likely to loosen or warp under wind vibration or temperature changes, thus improving the long-term stability of the structure. This method is suitable for the renovation of the anti-flashover structure on the ground potential side of old transmission towers, restoring and improving the anti-flashover performance without disassembling the substrate or affecting the tower structure.

[0037] The following comparative tests were conducted on multiple samples employing the anti-flashover structure of this invention, divided into two groups: a 110kV voltage level comparison test and a 220kV voltage level comparison test. For each voltage level, one sample with only the first insulating coating applied and without the skirt and second insulating coating installed was used as a comparative reference. The remaining samples maintained consistency in substrate specifications, insulating coating materials, construction steps, and test conditions, with adjustments only made to the skirt radius and the spacing between adjacent skirts. The thicknesses of the first and second insulating coatings used in the two voltage levels differed to match the insulation level requirements of their respective voltage levels. The test compared the anti-flashover performance under different skirt parameters by measuring the surface power frequency breakdown voltage of each scheme. Specific parameter settings for each sample in the 110kV group are detailed in Table 1, and specific parameter settings for each sample in the 220kV group are detailed in Table 2.

[0038] Table 1 Table 2 In the comparative test of the 110kV group, power frequency voltage discharge tests were carried out on each sample listed in Table 1. It should be noted that Comparative Example 1 only had the first insulating coating sprayed on, without the shed and the second insulating coating installed. The thickness of its first insulating coating was 4mm, which is equivalent to the sum of the thickness of the first insulating coating (3.5mm) and the second insulating coating (0.5mm) of Samples 1 to 10, so as to compare the difference in flashover prevention performance with and without the shed structure under the premise of the same total coating thickness. The test operation steps are as follows: the corresponding sample was placed on the test platform, and the relative position of the conductor and the substrate was adjusted, i.e., the minimum gap distance. The minimum gap for 110kV was 25cm. The end of the conductor was pressurized through the power frequency transformer, and the pressure was linearly increased within 1 minute until the gap broke down or flashover occurred. Each sample was tested 3 times to ensure that the influence of randomness in the test process on the test results was eliminated. During the test, a camera was used to capture images and record the voltage at the moment of breakdown or flashover of each sample. The test results are shown in Table 3.

[0039] Table 3 In the comparative test of the 220kV group, power frequency voltage discharge tests were carried out on the samples listed in Table 2. It should be noted that the sample of Comparative Example 2 only had the first insulating coating sprayed on, without the shed and the second insulating coating installed. The thickness of its first insulating coating was 8mm, which is equivalent to the sum of the thickness of the first insulating coating (7.5mm) and the second insulating coating (0.5mm) of samples eleven to twenty, so as to compare the difference in flashover prevention performance with and without the shed structure under the premise of the same total coating thickness. The test operation steps are as follows: the corresponding sample was placed on the test platform, and the relative position of the conductor and the substrate was adjusted, i.e., the minimum gap distance. The minimum gap for 220kV was 55cm. The end of the conductor was pressurized through the power frequency transformer, and the pressure was linearly increased within 1 minute until the gap broke down or flashover occurred. Each sample was tested 3 times to ensure that the influence of randomness in the test process on the test results was eliminated. During the test, a camera was used to capture images and record the voltage at the moment of breakdown or flashover of each sample, and the data was recorded. The test results are shown in Table 4.

[0040] Table 4 As shown in Table 3, at a voltage level of 110kV, the breakdown voltages of samples one through ten are all improved compared to comparative sample one, indicating that the anti-flashover structure of the present invention can effectively improve the insulation performance of the transmission tower's ground potential side and meet the anti-flashover protection requirements of high-voltage transmission lines. Based on this, the optimal range of values ​​for the skirt radius and skirt spacing is further analyzed.

[0041] By comparing samples one to five (the distance between two adjacent umbrella skirts is 100mm, and the radii are 60mm, 75mm, 85mm, 100mm, and 115mm respectively), the improvement rates of samples two to four (radii from 75mm to 100mm) were 10.50%, 14.40%, and 17.90% respectively, all higher than 9%. Sample 1 (radius 60mm) showed an improvement of only 6.60%, lower than 9%. This is because its relatively small radius results in a shorter radial extension of the outer edge of the umbrella skirt over the substrate surface, thus shortening the surface path for leakage current and limiting the increase in creepage distance. Furthermore, an excessively small radius may prevent the outer edge of the umbrella skirt from completely enclosing the substrate surface, making it difficult to form effective creepage shielding around the substrate circumference. Sample 5 showed an improvement of 8.00%, also lower than 9%. This is because an excessively large umbrella skirt radius significantly reduces the air gap between the outer edge of the umbrella skirt and the conductor, lowering the insulation strength of this gap and making air breakdown more likely during pressure testing, thereby weakening the overall flashover protection effect. Additionally, an excessively large radius increases the wind-exposed area of ​​the component, leading to a larger wind resistance load, which is detrimental to the long-term stability of the structure. Therefore, a skirt radius of 75mm-100mm is preferable.

[0042] By comparing samples 2 and 6 to 9 (with a skirt radius of 75mm and spacing between adjacent skirts of 100mm, 80mm, 150mm, 200mm, and 250mm respectively), the improvement rates for samples 2, 7, and 8 (spacing from 100mm to 200mm) were 10.50%, 9.90%, and 9.50%, respectively, all higher than 9%. However, sample 6 (spacing 80mm) showed only a 6.00% improvement, lower than 9%. This is because its relatively small spacing shortens the air gap between adjacent skirt edges, leading to a more concentrated electric field and a greater likelihood of air breakdown, thus weakening the skirt's effect of increasing creepage distance. Furthermore, a small spacing can easily cause bridging under humid or condensing conditions and is detrimental to spray coating application. Sample 9 (spacing 250mm) showed a 4.60% improvement, also lower than 9%. This is because a larger spacing reduces the number of skirts per unit length, weakening the segmented blocking effect on the discharge channel and resulting in a decrease in overall flashover prevention. Therefore, a spacing of 100mm to 200mm between two adjacent umbrella skirts is preferable.

[0043] In addition, the improvement of sample 10 (radius 100mm, spacing 200mm) was 16.30%, which is at a relatively high level.

[0044] As shown in Table 4, at the 220kV voltage level, the breakdown voltages of samples eleven to twenty are all improved compared to comparative sample two, further verifying the effectiveness of the anti-flashover structure of the present invention. Regarding the skirt radius, the improvement rates of samples twelve to fourteen (radii 75mm to 100mm) are all higher than 14%, while the improvement rates of samples eleven (radius 60mm) and fifteen (radius 115mm) are both lower than 14%, consistent with the trend of the 110kV group. Regarding the skirt spacing, the improvement rates of samples twelve, seventeen, and eighteen (spacing 100mm to 200mm) are all higher than 14%, while the improvement rates of samples sixteen (spacing 80mm) and nineteen (spacing 250mm) are both lower than 14%, also consistent with the trend of the 110kV group. Furthermore, the improvement rate of sample twenty (radius 100mm, spacing 200mm) is 17.30%, which is at a relatively high level.

[0045] In summary, a skirt radius of 75mm to 100mm and a spacing of 100mm to 200mm between adjacent skirts represent an optimal range considering creepage distance, anti-bridging capability, air gap insulation strength, wind resistance load, and ease of construction. Within this range, the skirts effectively extend the creepage path along the surface, minimizing the formation of air breakdown short-circuit paths or contamination bridging between adjacent skirts. Simultaneously, sufficient air gap is maintained between the outer edge of the skirts and the conductor, resulting in controllable overall wind resistance and ample space for spraying operations. These dimensions, combined with the continuous closed protective structure formed by the first and second insulating coatings, ensure stable insulation performance on the ground potential side of the transmission tower under adverse conditions such as contamination and moisture, reducing the risk of flashover discharge.

[0046] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A flashover prevention structure on the ground potential side of a transmission tower, characterized in that: include: Substrate; A first insulating coating is applied to the surface of the substrate; A multiple umbrella skirt is fitted onto the substrate and is spaced apart along the length of the substrate. And a second insulating coating, which continuously covers the surface of the umbrella skirt, the assembly gap between the umbrella skirt and the first insulating coating, and the outer surface of the first insulating coating; The radius of the umbrella skirt is 75mm-100mm, and the distance between two adjacent umbrella skirts is 100mm-200mm. The base material is angle steel. The umbrella skirt includes a first part and a second part. The first part is a fan-shaped structure with a notch and a central angle greater than 180 degrees. The notch fits with the outer surface of the base material. The second part is a fan-shaped structure with an angle less than 180 degrees and has an edge. The second part is embedded in the notch, and the edge fits with the inner surface of the base material. The first part and the second part are connected by a connector to clamp the base material. The first part has a first connecting plate axially protruding from the first part at both sides of the notch. The first connecting plate is attached to the outer surface of the base material. The two ends of the first connecting plate... Each of the two components has a first connecting portion extending outward along the width direction of the substrate. The edge of the second component has a second connecting plate axially protruding outward from the second component. The second connecting plate is attached to the inner surface of the substrate. Each end of the second connecting plate has a second connecting portion extending outward along the width direction of the substrate. The first connecting portion and the second connecting portion correspond one-to-one and are arranged opposite each other. The oppositely arranged first connecting portion and second connecting portion are connected by the connector. The second insulating coating continuously covers the assembly gap between the first connecting plate and the outer surface of the substrate and the assembly gap between the second connecting plate and the inner surface of the substrate.

2. The anti-flashover structure on the ground potential side of the transmission tower according to claim 1, characterized in that: The first connecting portion and the second connecting portion, which are arranged opposite to each other, are respectively provided with through holes for the connecting member to pass through.

3. The anti-flashover structure on the ground potential side of the transmission tower according to claim 2, characterized in that: The second insulating coating also continuously covers the assembly gap between the connector and the through hole.

4. The anti-flashover structure on the ground potential side of the transmission tower according to claim 1, characterized in that: The thickness of the first insulating coating is 3.5mm-7.5mm, and the thickness of the second insulating coating is 0.5mm-1mm.

5. The anti-flashover structure on the ground potential side of the transmission tower according to claim 1, characterized in that: The wind deflection check point on the ground potential side of the transmission tower is located on the surface of the substrate. At least two sets of spaced-apart skirts are provided on the first insulating coating. Each skirt set includes multiple skirts spaced-apart along the length of the substrate. The distance between the skirt set and the wind deflection check point is greater than 0.5m.

6. A construction method for the anti-flashover structure on the ground potential side of a transmission tower according to any one of claims 1-5, characterized in that: Includes the following steps: S1: Spray insulating material onto the surface of the substrate to form a first insulating coating; S2: Install umbrella skirts on the substrate, wherein the umbrella skirts are fitted onto the substrate, and there are multiple umbrella skirts, which are spaced apart along the length direction of the substrate; S3: Spray insulating material onto the surface of the umbrella skirt and the outer surface of the first insulating coating to form a second insulating coating. The second insulating coating continuously covers the surface of the umbrella skirt, the assembly gap between the umbrella skirt and the first insulating coating, and the outer surface of the first insulating coating.

7. The construction method according to claim 6, characterized in that: In S1 and S3, the insulating material is made by mixing isocyanate component and amine chain extender component in a 1:1 volume ratio.

8. The construction method according to claim 6, characterized in that: Before S1, it also includes: S0: Remove the umbrella skirts on the surface of the base material on the old transmission tower and clean the surface of the base material.

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