Transformer with lightning protection structure

Abstract

This invention discloses a transformer with a lightning protection structure, comprising: an oil tank, windings, an iron core, an integrated lightning protection cover, a grounding structure, a lightning protection conductive plate, and a layered insulation structure. The transformer features a lightning protection cover and lightning-proof protrusion electrically connected to the outer casing at the top of the oil tank, a grounding structure including a grounding base and grounding electrodes at the bottom, and a lightning protection conductive plate connecting the lightning protection cover and the grounding base internally. The plate has conductive contacts that fit against the insulating outer casing of the windings. Multiple layers of insulating sleeves and insulating spacers are provided on the outer side of the windings. This application achieves dual protection against direct and induced lightning strikes through structural optimization, shortens the lightning current conduction path for rapid voltage relief, enhances internal insulation performance, effectively prevents insulation breakdown caused by lightning overvoltage, and improves operational stability.

Description

Technical Field

[0001] This invention relates to the field of transformer technology, and in particular to a transformer with a lightning protection structure. Background Technology

[0002] Transformers are core power conversion devices in power systems, widely used in power generation, transmission, and distribution, undertaking the crucial functions of voltage transformation and power distribution. In existing technologies, transformer lightning protection primarily relies on externally installed lightning rods, lightning conductors, and other direct lightning strike protection devices, as well as electrical components such as zinc oxide surge arresters connected in series or parallel within the circuit. External lightning rods capture direct lightning currents through lightning arresters and conduct them to the ground, protecting the transformer itself from direct strikes. Surge arresters utilize their nonlinear volt-ampere characteristics to rapidly conduct when lightning overvoltages occur, limiting the overvoltage to a certain range and thus protecting the transformer's internal winding insulation. These existing solutions, combined with the transformer's own tank grounding measures, constitute a basic lightning protection system to cope with lightning threats under complex outdoor weather conditions.

[0003] However, in existing technologies, the lightning protection effectiveness of transformers is often limited by the performance stability and installation layout of external electrical components, and the transformer's own structure lacks optimized design for lightning current conduction paths. When encountering high-intensity lightning strikes, due to the long current conduction path or the lack of targeted reinforcement of the internal insulation structure, the induced lightning current is easily discharged in a timely manner, causing internal winding insulation breakdown or core damage, resulting in transformer failure and outage, and affecting the safe and stable operation of the power system. Summary of the Invention

[0004] A transformer with a lightning protection structure is proposed to solve the problems of existing transformers that rely on external electrical components, cannot achieve dual protection against direct lightning strikes and induced lightning strikes at the same time, and have insufficient lightning protection optimization of their own structure and untimely voltage discharge.

[0005] To achieve the above objectives, this application provides the following technical solution: A transformer with a lightning protection structure includes an oil tank, windings, and an iron core. The windings are sleeved on the outside of the iron core. The top of the oil tank has terminals, and an integrated lightning protection cover is fixedly installed on the top of the oil tank. The lightning protection cover is electrically connected to the outer shell of the oil tank, and the top of the lightning protection cover has a lightning protection protrusion. The bottom of the oil tank has a grounding structure, which includes a grounding base and a grounding electrode. The grounding base is electrically connected to the outer shell of the oil tank, and the grounding electrode is connected to the grounding base and extends to the ground. A lightning protection conductive plate is vertically fixed inside the oil tank. The upper end of the lightning protection conductive plate is electrically connected to the lightning protection cover, and the lower end is electrically connected to the grounding base. The lightning protection conductive plate has conductive contacts at positions corresponding to the windings, and the conductive contacts are tightly fitted to the insulating outer shell of the windings. The outer side of the windings has a layered insulation structure, which includes multiple layers of insulating sleeves and insulating spacers. Insulating end plates are provided at both ends of the windings.

[0006] Preferably, a transformer with a lightning protection structure is provided, wherein the coverage area of ​​the lightning protection cover completely covers the top of the oil tank and the terminal area, the bottom of the lightning protection cover is fixedly connected to the outer shell of the oil tank by bolts, and the bottom of the lightning protection cover is provided with a conductive connecting piece, which is tightly fitted to the outer shell of the oil tank to achieve electrical connection.

[0007] Preferably, in a transformer with a lightning protection structure, the lightning protection protrusions are symmetrically distributed along the center line of the lightning protection cover, and the lightning protection protrusions are pointed structures.

[0008] Preferably, in a transformer with a lightning protection structure, the grounding base is fixed at the four corners of the bottom of the oil tank, and the grounding base has a connection structure inside for connecting the grounding electrode. The grounding base is fixedly connected to the outer shell of the oil tank by conductive bolts to achieve electrical connection.

[0009] Preferably, in a transformer with a lightning protection structure, the conductive contact is arc-shaped, one end of the conductive contact is fixedly connected to the lightning protection conductive plate, and the other end is tightly fitted to the insulating shell of the winding without contacting the winding conductor.

[0010] Preferably, in a transformer with a lightning protection structure, a conductive protective sleeve is provided on the outside of the terminal block, the conductive protective sleeve is fixedly connected to the lightning protection cover, and a conductive spring is provided inside the conductive protective sleeve, the conductive spring being in close contact with the metal part of the terminal block.

[0011] Preferably, in a transformer with a lightning protection structure, in the layered insulation structure, multiple layers of insulating bushings are sequentially fitted onto the outer side of the winding from the inside to the outside, and the insulating spacers are disposed between adjacent layers of insulating bushings, and the insulating spacers are evenly distributed.

[0012] Preferably, in a transformer with a lightning protection structure, an iron core insulating cover is fitted on the outside of the iron core, and an insulating support block is provided between the iron core insulating cover and the inner wall of the oil tank. The insulating support blocks are symmetrically distributed and fixedly connected to the iron core insulating cover and the inner wall of the oil tank respectively.

[0013] Preferably, in a transformer with a lightning protection structure, the inner wall of the tank is provided with an insulating coating that covers the entire area of ​​the inner wall of the tank.

[0014] Preferably, in a transformer with a lightning protection structure, a connecting wire is provided between the terminal block and the winding, and a conductive branch is provided at one end of the connecting wire near the lightning protection conductive plate, and the conductive branch is fixedly connected to the lightning protection conductive plate.

[0015] Compared with the prior art, this application has at least the following beneficial effects: This application, by installing an integrated surge protector on the top of the oil tank, combined with the grounding structure at the bottom of the tank, can effectively guide direct lightning current, which is rapidly conducted to the ground through the surge protector, the tank shell, the grounding base, and the grounding electrode, achieving reliable protection against direct lightning strikes and preventing direct impact on the oil tank and internal core components. This solves the problem of incomplete direct lightning strike protection coverage in existing technologies. Simultaneously, the vertically installed surge protection conduction plate inside the oil tank, electrically connected at the top to the surge protector and at the bottom to the grounding base, along with the conductive contacts corresponding to the windings, can rapidly conduct induced lightning current on the windings, achieving effective protection against induced lightning strikes. This fills the gap in existing technologies where there is no dedicated induced lightning conduction structure and insufficient induced lightning protection. The layered insulation structure on the outside of the windings, including multiple layers of insulating bushings and insulating spacers, combined with the insulating end plates at both ends of the windings, forms reliable insulation protection, effectively resisting the impact of lightning overvoltages and preventing winding insulation breakdown, thus solving the problem of insufficient insulation protection capability of existing transformer windings. The overall technical solution eliminates the reliance on external electrical lightning protection components in existing technologies through the coordinated operation of mechanical structures. It has a simple structure, strong adaptability, and can be directly applied to the renovation of existing transformers or the production of new transformers. While achieving dual protection against direct lightning strikes and induced lightning, it improves the operational stability and service life of transformers and reduces manufacturing costs and maintenance difficulties. Attached Figure Description

[0016] Figure 1 is a schematic diagram of the overall structure of a transformer with lightning protection; Figure 2 is a partially enlarged schematic diagram of the connection structure between the lightning protection cover and the top of the oil tank; Figure 3 is a schematic diagram of the distribution structure of the lightning protection protrusions; Figure 4 is a cross-sectional schematic diagram of the connection structure between the grounding base and the bottom of the oil tank; Figure 5 is a schematic diagram of the structure of the conductive contact and the winding. Figure 6 is a schematic diagram of the terminal protection structure; Figure 7 is a schematic cross-sectional view of the layered insulation structure; Figure 8 is a schematic diagram of the iron core insulation support structure; Figure 9 is a schematic diagram of the insulating coating structure on the inner wall of the fuel tank; Figure 10 is a schematic diagram of the connection structure between the wiring terminal and the lightning protection conduction plate.

[0017] In the diagram: 1-oil tank; 2-winding; 3-iron core; 4-terminal; 5-lightning protection cover; 6-lightning protection protrusion; 7-grounding structure; 71-grounding base; 72-grounding electrode; 8-lightning protection conductive plate; 9-conductive contact piece; 10-layered insulation structure; 101-insulating sleeve; 102-insulating block; 11-insulating end plate; 12-bolt; 13-conductive connecting piece; 14-conductive bolt; 15-conductive protective sleeve; 16-conductive spring; 17-iron core insulating cover; 18-insulating support block; 19-insulating coating; 20-connecting wire; 21-conductive branch. Detailed Implementation

[0018] The technical solutions in the embodiments of this application will be described in detail below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the protection scope of this application.

[0019] As shown in Figure 1, the transformer with lightning protection structure in this embodiment includes a tank 1, windings 2, and an iron core 3 as its core components. The windings 2 are sleeved on the outside of the iron core 3. A terminal block 4 is installed on the top of the tank 1 for connecting to an external power transmission line. An integrated lightning protection cover 5 is fixedly mounted on the top of the tank 1. The lightning protection cover 5 is reliably electrically connected to the outer shell of the tank 1, and a lightning protection protrusion 6 is provided on its top. A grounding structure 7 is arranged at the bottom of the tank 1. This structure consists of a grounding base 71 and a grounding electrode 72. The grounding base 71 is electrically connected to the outer shell of the tank 1, and the grounding electrode 72 is connected to the grounding base 71 and extends to the ground. Inside the oil tank 1, a lightning protection conductive plate 8 is vertically fixed. Its upper end is electrically connected to the lightning protection cover 5, and its lower end is electrically connected to the grounding base 71. Conductive contact pieces 9 are installed on the lightning protection conductive plate 8 at the positions corresponding to the winding 2. The conductive contact pieces 9 are tightly fitted to the insulating shell of the winding 2 but do not contact the winding conductor. A layered insulation structure 10 is provided on the outside of the winding 2. This structure includes multiple layers of insulating sleeves 101 and insulating spacers 102. Insulating end plates 11 are assembled at both ends of the winding 2 to strengthen the end insulation protection.

[0020] The transformer in this embodiment, through its integrated structural design of external protection, internal pressure relief, and enhanced insulation, achieves dual protection against both direct and induced lightning strikes without requiring additional complex electrical components. In the event of a direct lightning strike, the lightning is first captured by the lightning protection protrusion 6 on the top of the lightning protection cover 5. The lightning current is conducted through the lightning protection cover 5 to the outer casing of the oil tank 1, and then quickly conducted to the ground through the grounding base 71 and grounding electrode 72, preventing damage to the transformer body from direct lightning strikes. When induced lightning is conducted through the line, the induced overvoltage acts on the winding 2. The charge accumulated on its surface is collected by the conductive contact 9 and conducted to the lightning protection conduction plate 8, and then discharged to the ground through the grounding structure 7, preventing the induced lightning current from entering the winding and causing insulation breakdown. Simultaneously, the layered insulation structure 10, through the cooperation of multiple insulating sleeves 101 and insulating spacers 102, further blocks residual overvoltages, prevents internal discharge, effectively improves the transformer's insulation protection capability, extends its service life, and is simple in structure, cost-effective, and easy to maintain.

[0021] The oil tank 1 adopts a rectangular sealed steel plate structure, which is mainly used to accommodate internal components such as winding 2, iron core 3 and insulating oil. At the same time, as an important part of the direct lightning current conduction path, its outer shell must have good conductivity. Together with the lightning protection cover 5, it can smoothly conduct the lightning current into the grounding structure 7 to ensure smooth discharge.

[0022] Winding 2, made of copper or aluminum wire, is sleeved on the outside of the iron core 3 and is the core component of the transformer for voltage transformation. The outside of winding 2 is wrapped with an insulating shell and is tightly fitted with the conductive contact 9, which can quickly conduct induced lightning current without penetrating into the conductor. Its parameters such as the number of turns and wire diameter can be flexibly set according to the actual capacity and voltage level of the transformer to adapt to different application scenarios.

[0023] The iron core 3 is made of laminated silicon steel sheets, but other suitable magnetically conductive materials can also be selected. Its core function is to provide a magnetic flux path. The iron core 3 is isolated from the inner wall of the oil tank 1 by a special insulation structure to prevent discharge between the iron core and the oil tank caused by lightning overvoltage, thus ensuring internal electrical safety.

[0024] Terminal 4 is a metal connector on the top of tank 1. Its core function is to connect to external power transmission lines. Its installation position is within the coverage area of ​​lightning protection cover 5, which can effectively prevent direct lightning strikes and reduce the risk of damage to the terminal.

[0025] The surge protector 5 is an integrated conductive enclosure, made of galvanized steel, stainless steel, or aluminum alloy. Its shape can be curved or flat-topped depending on the actual installation requirements. Its coverage must completely cover the top of the tank and the terminal area to ensure comprehensive protection. The electrical connection between the surge protector 5 and the tank casing can be achieved by welding or bolts with conductive gaskets. As a direct lightning strike arrestor, its core function is to guide the lightning current through the tank casing to the grounding structure 7, thus constructing the first line of defense against external lightning strikes.

[0026] The lightning protection protrusion 6 is a pointed protrusion on the top of the lightning protection cover 5, with no fewer than two protrusions. They can be symmetrically or evenly distributed along the center line of the lightning protection cover, and their height is controlled between 30mm and 100mm. Utilizing the principle of point discharge, the lightning protection protrusion 6 can preferentially attract lightning and quickly conduct the lightning current into the body of the lightning protection cover, preventing lightning from striking other weak parts of the transformer.

[0027] The grounding structure 7 consists of a grounding base 71 and a grounding electrode 72. Its core function is to conduct lightning current into the ground. Its overall size, burial depth and other parameters need to be determined according to the soil resistivity and lightning protection level of the installation site. It also needs to be reliably electrically connected to the tank shell to ensure smooth discharge of lightning current without any stagnation.

[0028] The grounding base 71 is a metal base fixed to the bottom of the oil tank. It can be made of cast iron, copper, or galvanized steel and has internal threaded holes and other connection structures for fixing the grounding electrode 72. The grounding base 71 is securely connected to the oil tank casing via conductive bolts, serving as a crucial link to smoothly transfer the lightning current conducted through the oil tank casing to the grounding electrode 72.

[0029] Grounding electrode 72 uses metal conductors such as round steel or steel pipes to extend underground. Its length, diameter and burial depth need to be set according to the grounding resistance requirements. The lower end can be sharpened or have water-permeable holes to facilitate driving into the soil and making full contact with the soil, so as to ensure that the lightning current can be effectively dissipated to the ground.

[0030] The lightning protection conduction plate 8 is a metal plate such as a copper plate or aluminum plate that is vertically fixed inside the oil tank. Its size is adapted to the internal space of the oil tank. The upper end is connected to the lightning protection cover 5 and the lower end is connected to the grounding base 71, forming a longitudinal low impedance conductive path. It is specially designed to provide a fast discharge channel for the induced charge on the winding surface and shorten the pressure relief path.

[0031] The conductive contact 9 can be an arc-shaped, sheet-shaped, or spring-shaped conductive component. One end is fixedly connected to the lightning protection conductive plate 8, and the other end is tightly fitted to the insulating shell of the winding 2 through elastic compression or surface contact. It is strictly forbidden to contact the winding conductor. Its core function is to quickly guide the induced charge on the surface of the winding to the lightning protection conductive plate 8 to avoid charge accumulation.

[0032] The layered insulation structure 10 is a multi-layered insulation assembly wrapped around the outside of the winding 2. It consists of an insulating bushing 101 and an insulating spacer 102. The number of layers, thickness and material selection need to be determined according to the transformer voltage level and insulation requirements. It can effectively improve the insulation withstand voltage level and prevent lightning overvoltage from damaging the winding 2.

[0033] The insulating bushing 101 is made of insulating materials such as polytetrafluoroethylene and epoxy resin, and is made into a tubular structure. It is sequentially fitted on the outside of the winding 2 from the inside to the outside. Insulating spacers 102 can be set between adjacent layers as needed. Their thickness and number of layers can be adjusted according to the actual application scenario. They mainly undertake the main insulation function to prevent high voltage breakdown.

[0034] The insulating spacer 102 is made of insulating materials such as ceramic and epoxy resin, and is made into a block structure. It is evenly distributed along the circumference between adjacent insulating sleeves. It not only supports the sleeves and maintains the interlayer spacing, but also forms an insulating gap. At the same time, it also has the functions of heat dissipation and buffering mechanical stress, ensuring the stability of the layered insulation structure.

[0035] The insulating end plate 11 is made of epoxy resin board or mica board, and its shape is adapted to the end face of winding 2. Heat dissipation holes can be opened according to heat dissipation requirements. Its core function is to seal the electric field at the end of the winding, prevent end discharge, and enhance the axial insulation strength of the winding.

[0036] The surge protector 5 must completely cover the top of the tank and the terminal area. The bottom is fixed to the tank shell by bolts 12. At the same time, conductive connecting pieces 13 are provided on the mating surface to ensure reliable electrical connection between the surge protector 5 and the tank shell, forming the first line of defense against direct lightning strikes and preventing lightning from hitting the terminal or weak parts of the tank.

[0037] Bolt 12 is mainly used to mechanically fix the surge protector 5 to the tank shell. Its quantity and specifications are set according to the size of the surge protector and the installation strength requirements to ensure that the surge protector will not loosen due to wind, vibration and other factors during long-term outdoor operation. At the same time, bolt 12 can help to tighten the conductive connecting piece 13, maintain contact stability and provide a reliable foundation for lightning current conduction.

[0038] The conductive connecting piece 13 is made of materials with excellent conductivity such as copper and aluminum. Its shape is adapted to the mating surface, which can effectively reduce contact resistance, make up for the gaps in the bolt connection, and ensure that the lightning current can be quickly introduced into the tank shell with low impedance, avoiding safety risks such as local high temperature and arc discharge caused by poor contact.

[0039] When a lightning strike occurs, the lightning protection cover 5 first intercepts the direct lightning current, which is then quickly conducted to the tank shell via the conductive connecting piece 13. The bolt 12 ensures stable contact between the two, thereby achieving efficient transmission of the lightning current from the external protection structure to the grounding system and ensuring timely discharge.

[0040] The lightning protection protrusions 6 are symmetrically distributed along the center line of the lightning protection cover 5. They adopt a pointed structure and are based on the principle of point discharge. They can concentrate the electric field intensity and preferentially attract lightning, preventing lightning from hitting other parts of the transformer. The lightning current is conducted through the lightning protection cover 5 to the grounding structure 7 and then discharged to the ground, ensuring the safety of the internal components.

[0041] The symmetrically distributed lightning protection protrusions 6 can make the electric field distribution above the lightning protection cover 5 uniform, eliminating protection blind spots. The number of them is set according to the actual protection requirements, and the material is consistent with the lightning protection cover 5 to ensure that the lightning current can be conducted quickly without stagnation.

[0042] During thunderstorms, corona discharge occurs at the top of the lightning protection protrusion 6. The symmetrically distributed protrusions work together to create a stable and strong electric field above the lightning protection cover 5, guiding the main discharge channel of lightning to fall on the lightning protection protrusion 6. The lightning current is discharged to the ground through the lightning protection cover 5, the tank shell, and the grounding structure 7, effectively protecting the internal components of the transformer from direct lightning strikes.

[0043] The grounding base 71 is fixed at the four corners of the bottom of the oil tank and has an internal connection structure for connecting the grounding electrode 72. It is electrically connected to the outer shell of the oil tank through conductive bolts 14. The four-corner layout not only evenly distributes the weight of the transformer, but also creates a multi-point grounding channel, avoiding the hidden dangers of single-point grounding and ensuring stable discharge of lightning current.

[0044] The internal connection structure of the grounding base 71 can be in the form of threaded holes, plug slots, etc., which facilitates the fixing of the grounding electrode 72 and the realization of reliable electrical connection. At the same time, it facilitates on-site installation and subsequent maintenance and replacement, ensuring that lightning current can flow to the grounding electrode 72 without obstruction.

[0045] The conductive bolt 14 is made of highly conductive material and is used to fasten the grounding base 71 to the tank shell. It can be used with conductive gaskets or the contact surface can be treated to ensure a reliable electrical connection between the two, so that the tank 1, grounding base 71 and grounding electrode 72 form a continuous conductive whole, ensuring efficient transmission of lightning current.

[0046] During a lightning strike, the lightning current is conducted through the lightning protection cover 5 and the lightning protection conduction plate 8 to the outer shell of the oil tank 1, and then dispersed to the grounding bases 71 at the four corners. Through the internal connection structure, it is conducted to the grounding electrode 72 and discharged to the ground. The four-corner layout provides redundant discharge channels. Even if a connection at one corner becomes slightly loose or corroded, the other grounding bases can still maintain effective grounding, ensuring the reliable operation of the lightning protection system.

[0047] The conductive contact 9 adopts an arc-shaped structure. One end is fixedly connected to the lightning protection conductive plate 8, and the other end is tightly fitted to the insulating shell of the winding 2 without contacting the winding conductor. The arc-shaped design can effectively compensate for manufacturing tolerances, maintain stable contact pressure, reduce contact resistance, and provide a path for induced charge discharge only during lightning strikes, without affecting the normal operation of the transformer.

[0048] The arc-shaped conductive contact piece can adapt to the slight unevenness on the surface of winding 2 through its own elastic deformation, ensuring continuous and stable contact. It works in conjunction with the lightning protection conduction plate 8 and winding 2 to quickly discharge induced charges, avoid the risk of partial discharge or short circuit, and ensure the safe operation of the transformer.

[0049] The conductive contact 9 can be a composite structure of a single stamped copper sheet, multiple stacked elastic copper foils, or an embedded spring steel sheet. The material is a highly conductive metal, and its contact area and curvature can be adjusted according to the size of the winding 2 to ensure tight contact and reliable conductivity, meeting the needs of different application scenarios.

[0050] When struck by induced lightning, the induced charge accumulated on the surface of winding 2 is quickly collected by the conductive contact 9 and conducted into the lightning protection conduction plate 8, and then discharged to the ground through the grounding structure 7. Since the conductive contact 9 does not contact the winding conductor, it does not affect the normal transformation function of the transformer, thus achieving rapid discharge of internal induced lightning.

[0051] The terminal 4 is covered with a conductive protective sleeve 15, which can be made of copper, aluminum alloy, etc., and is fixedly connected to the surge protector 5. The conductive protective sleeve 15 is equipped with a conductive spring 16, which is in close contact with the metal part of the terminal 4. This allows the terminal 4 to be incorporated into the external surge protection system, clamping the potential and preventing discharge caused by excessive potential difference.

[0052] The conductive spring 16 is made of highly conductive and elastic material such as phosphor bronze. It maintains stable contact pressure by utilizing its own elastic deformation, which solves the problem of poor contact that is prone to occur in rigid connections. It can quickly divert the lightning current on the terminal 4 to the conductive protective sleeve 15 and then transmit it to the lightning protection system for discharge.

[0053] When a lightning surge enters terminal 4, its voltage rises instantaneously. The lightning current is quickly conducted through the conductive spring 16 into the conductive protective sleeve 15, and then transmitted to the lightning protection cover 5 and the grounding structure 7 to be discharged to the ground. At the same time, the conductive protective sleeve 15 can suppress the concentration of the electric field around terminal 4, avoiding the occurrence of partial discharge.

[0054] In the layered insulation structure 10, multiple layers of insulating bushings 101 are sequentially fitted onto the outer side of the winding 2 from the inside out, with uniformly distributed insulating spacers 102 between adjacent layers. The multiple bushings form a gradient insulation barrier, which can effectively weaken the electric field strength generated by lightning overvoltage. The insulating spacers 102 maintain the interlayer spacing, disperse electric field stress, and improve insulation reliability.

[0055] The insulating spacer 102 can adopt a block or columnar structure, and the material can be ceramic, epoxy resin, etc. It is evenly distributed along the circumference of the winding to ensure consistent insulation performance in the circumferential direction of the winding. While supporting the insulating bushing, it forms a dielectric buffer zone to avoid partial discharge.

[0056] When the high voltage generated by lightning strikes acts on the layered insulation structure 10, the multi-layer insulating bushing 101 gradually reduces the voltage, and the gap formed by the insulating spacer 102 disperses the electric field stress, eliminates weak points in the insulation, significantly improves the overall insulation withstand voltage level and resistance to partial discharge, and prevents winding insulation breakdown.

[0057] An insulating cover 17 is fitted over the outer side of the iron core 3. The material is epoxy resin or other high-temperature resistant insulating materials. Symmetrically distributed insulating support blocks 18 are provided between the insulating cover 17 and the inner wall of the oil tank 1, and are fixedly connected to both. The insulating cover 17 can block the electrical path between the iron core 3 and the conductive parts, while the insulating support blocks 18 achieve mechanical fixation and maintain insulation isolation.

[0058] The insulating support block 18 is made of high-strength insulating material. Its symmetrical distribution can balance the supporting force, offset the vibration and impact generated by the iron core 3 during operation, prevent the iron core from shifting and wear the insulation layer, and at the same time maintain the electrical isolation between the iron core 3 and the oil tank 1 to ensure electrical safety.

[0059] During a lightning strike, the iron core insulation cover 17 isolates the iron core 3 from the oil tank 1 to prevent discharge and burns to the components; the insulation support block 18 stabilizes the iron core 3 and counteracts the vibration. Together, they form a composite insulation and fixing structure that balances the electrical safety and mechanical stability of the iron core.

[0060] The inner wall of fuel tank 1 is fully covered with an insulating coating 19, made of temperature- and aging-resistant insulating materials such as epoxy resin, with the thickness set according to the insulation class. As the last line of insulation protection inside, the insulating coating 19 can block potential discharge paths and eliminate electric field concentration. Together with other insulation structures, it comprehensively ensures the electrical safety inside the fuel tank.

[0061] After a lightning strike, induced overvoltage may remain inside the oil tank 1. The fully covered insulating coating 19 can effectively isolate the live parts from the inner wall of the oil tank, prevent partial discharge from evolving into a breakdown accident, maintain the integrity of the internal insulation system, and ensure the normal operation of the transformer in the future.

[0062] A connecting wire is installed between terminal 4 and winding 2. A conductive branch is installed at the end of the connecting wire near the lightning protection conduction plate 8, and it is fixedly connected to the lightning protection conduction plate 8. The connecting wire undertakes the current transmission function during normal operation, while the conductive branch forms a lightning current bypass channel to realize the discharge of lightning current nearby and shorten the conduction path.

[0063] The conductive branches are connected to the connecting wires and the lightning protection conductive plate 8 by welding, crimping, etc. The material is made of highly conductive materials such as copper core, which can quickly divert the lightning current at the terminal 4, reduce the current propagation delay, avoid the lightning current from impacting the insulation layer of the winding 2, and reduce the risk of damage.

[0064] During normal operation, the conductive branch does not participate in current transmission and does not affect the normal operation of the transformer. When encountering an induced lightning strike, the potential of terminal 4 rises instantaneously, and the lightning current flows into the lightning protection conduction plate 8 through the conductive branch first, and then is discharged to the ground to avoid damaging the insulation of winding 2 and achieve rapid voltage discharge nearby.

[0065] As a preferred embodiment, the specific implementation of this application is as follows: The transformer body adopts a rectangular sealed steel plate oil tank 1, and the winding 2 is installed inside and sleeved on the outside of the iron core 3. The top of the oil tank 1 is provided with a terminal block 4. The external lightning protection adopts an arc-shaped lightning protection cover 5 made of 3mm thick galvanized steel plate, which completely covers the top of the oil tank and the terminal block 4. The bottom is fixed to the outer shell of the oil tank by bolts, and a conductive connecting piece 13 is provided on the contact surface to ensure electrical connection; two 50mm high pointed lightning protection protrusions 6 are welded to the top of the lightning protection cover 5. The grounding structure 7 includes cast iron grounding bases 71 fixed at the four corners of the bottom of the oil tank 1, and galvanized round steel grounding electrodes 72 with a length of 1.5m. The lower end of the grounding electrode 72 extends into the soil to a depth of 1.2m. The grounding base 71 is fastened to the outer shell of the oil tank 1 by conductive bolts 14. For internal pressure relief, a 4mm thick copper lightning protection conductive plate 8 is vertically fixed on the left side inside the oil tank 1. The upper end is connected to the lightning protection cover 5, and the lower end is connected to the grounding base 71. Three arc-shaped copper conductive contacts 9 are set on the lightning protection conductive plate 8 corresponding to the position of the winding 2. One end is riveted to the conductive plate, and the other end is tightly attached to the surface of the first layer of insulating sleeve of the winding 2. For insulation reinforcement, a polytetrafluoroethylene first insulating sleeve, a glass fiber insulating tape is wrapped around the outside of the winding 2, and an epoxy resin second insulating sleeve is installed in sequence. Ceramic insulating spacers 102 are evenly distributed between adjacent layers of sleeves. Epoxy resin insulating end plates 11 with heat dissipation holes are installed at both ends of the winding 2.

[0066] Through the above specific implementation methods, this application achieves the following beneficial effects: The lightning protection cover 5 and the grounding structure 7 work together to form a complete conductive circuit, which can simultaneously guide direct lightning strikes and discharge induced lightning, solving the problem of limited lightning protection coverage in traditional solutions; The lightning protection conduction plate 8 and the conductive contact 9 shorten the conduction path of induced lightning current, achieve rapid voltage discharge, and reduce the risk of damage to winding 2 and iron core 3 by lightning impact; The layered insulation structure 10 significantly improves the transformer's own insulation protection capability, effectively prevents insulation breakdown caused by lightning overvoltage, and extends service life; All lightning protection measures are achieved through mechanical structure optimization, without the need to add complex electrical components, resulting in a simple structure, low cost, and easy maintenance, possessing good practicality and promotional value.

[0067] When a thunderstorm approaches and lightning strikes the transformer first, the pointed lightning protection protrusions 6 symmetrically distributed along the centerline on the top of the surge protector 5 utilize the principle of point discharge to preferentially capture the direct lightning current. At this time, the terminal 4 is within the full coverage of the surge protector 5, and is covered by a conductive protective sleeve 15 fixedly connected to the surge protector 5. The internal conductive spring 16 is in close contact with the metal part of the terminal 4, preventing the direct lightning strike from hitting the terminal 4. The direct lightning current is guided into the integrated surge protector 5 through the lightning protection protrusions 6. The bottom of the surge protector 5 is fixed to the outer shell of the tank 1 by bolts 12, and the contact surface is provided with conductive connecting pieces 13 to ensure that the lightning current is conducted to the outer shell of the tank 1 with low impedance. At the same time, the insulating coating 19 covering the inner wall of the tank 1 blocks the current from flowing turbulently along the inner wall and avoids electric field concentration. The lightning current in the outer shell of the tank 1 is quickly conducted to the grounding bases 71 fixed at the four corners at the bottom. The grounding bases 71 are connected to the tank 1 by conductive bolts 14. The outer casing is reliably electrically connected, and the internal connection structure transmits the lightning current to the grounding electrode 72 extending into the ground. The grounding electrode 72 then dissipates the direct lightning current to the ground, completing direct lightning protection. If lightning is conducted through the line, generating induced lightning, the induced overvoltage acts on the winding 2. The layered insulation structure 10 (composed of multiple layers of insulating sleeves 101 and uniformly distributed insulating blocks 102) wrapped around the winding 2 first blocks part of the overvoltage. Simultaneously, the induced charge accumulated on the surface of the winding 2 is collected by the arc-shaped conductive contact 9 on the lightning protection conduction plate 8. The induced charge is guided through the conductive contact 9 to the lightning protection conduction plate 8, which is vertically fixed inside the oil tank 1. The upper end of the lightning protection conduction plate 8 is electrically connected to the lightning protection cover 5, and the lower end is electrically connected to the grounding base 71, forming a longitudinal low-impedance discharge channel. This conducts the induced charge to the grounding base 71, and then discharges it to the ground through the grounding electrode 72, completing the induced lightning pressure relief. During this process, the iron core insulating cover 17 fitted outside the iron core 3 and the oil tank 1... The symmetrically distributed insulating support blocks 18 on the inner walls work together to isolate the iron core 3 from the inner wall of the oil tank 1, preventing discharge due to potential difference. The insulating end plates 11 at both ends of the winding 2 seal the end electric field to prevent end discharge. The connecting wire between the terminal 4 and the winding 2 has its conductive branch near the lightning protection conduction plate 8 fixedly connected to the lightning protection conduction plate 8, which can divert the residual induced lightning current at the terminal 4 to the lightning protection conduction plate 8 nearby, further improving the voltage discharge efficiency. After the lightning impact, the layered insulation structure 10, the iron core insulation cover 17, and the insulating coating 19 on the inner wall of the oil tank 1 work together to maintain the internal insulation integrity of the transformer, ensuring that the transformer returns to normal operation. The whole process forms a dual protection closed loop of "direct lightning interception - current conduction - grounding discharge" and "induced lightning collection - internal conduction - grounding discharge". All necessary features work together to achieve all-round lightning protection.

[0068] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A transformer with a lightning protection structure, comprising an oil tank, windings, and an iron core, wherein the windings are sleeved on the outside of the iron core, and the top of the oil tank is provided with terminals, characterized in that, An integrated lightning protection cover is fixedly installed on the top of the oil tank, and the lightning protection cover is electrically connected to the outer shell of the oil tank. The top of the lightning protection cover has a lightning protection protrusion. The bottom of the oil tank has a grounding structure, which includes a grounding base and a grounding electrode. The grounding base is electrically connected to the outer shell of the oil tank, and the grounding electrode is connected to the grounding base and extends to the ground. A lightning protection conductive plate is vertically fixed inside the oil tank. The upper end of the lightning protection conductive plate is electrically connected to the lightning protection cover, and the lower end is electrically connected to the grounding base. The lightning protection conductive plate has conductive contact pieces at the positions corresponding to the windings. The conductive contact pieces are tightly fitted to the insulating outer shell of the windings. A layered insulation structure is provided on the outside of the windings. The layered insulation structure includes multiple layers of insulating sleeves and insulating spacers. Insulating end plates are provided at both ends of the windings.

2. A transformer with a lightning protection structure according to claim 1, characterized in that, The lightning protection cover completely covers the top of the oil tank and the terminal area. The bottom of the lightning protection cover is fixedly connected to the outer shell of the oil tank by bolts, and the bottom of the lightning protection cover is provided with a conductive connecting piece. The conductive connecting piece is tightly fitted to the outer shell of the oil tank to achieve electrical connection.

3. A transformer with a lightning protection structure according to claim 1, characterized in that, The lightning protection protrusions are symmetrically distributed along the center line of the lightning protection cover, and the lightning protection protrusions are pointed structures.

4. A transformer with a lightning protection structure according to claim 1, characterized in that, The grounding base is fixed at the four corners of the bottom of the oil tank. The grounding base has a connection structure inside for connecting the grounding electrode. The grounding base is fixedly connected to the outer shell of the oil tank by conductive bolts to achieve electrical connection.

5. A transformer with a lightning protection structure according to claim 1, characterized in that, The conductive contact has an arc-shaped structure. One end of the conductive contact is fixedly connected to the lightning protection conductive plate, and the other end is tightly fitted to the insulating shell of the winding without contacting the winding conductor.

6. A transformer with a lightning protection structure according to claim 1, characterized in that, The terminal block is covered with a conductive protective sleeve, which is fixedly connected to the surge protector. Inside the conductive protective sleeve is a conductive spring, which is in close contact with the metal part of the terminal block.

7. A transformer with a lightning protection structure according to claim 1, characterized in that, In the layered insulation structure, multiple layers of insulating sleeves are sequentially fitted onto the outer side of the winding from the inside out, and the insulating spacers are disposed between adjacent layers of insulating sleeves and are evenly distributed.

8. A transformer with a lightning protection structure according to claim 1, characterized in that, An insulating cover is fitted on the outside of the iron core. An insulating support block is provided between the insulating cover and the inner wall of the oil tank. The insulating support blocks are symmetrically distributed and fixedly connected to the insulating cover and the inner wall of the oil tank, respectively.

9. The transformer with lightning protection structure according to claim 1, characterized in that, The inner wall of the fuel tank is provided with an insulating coating, which covers the entire area of ​​the inner wall of the fuel tank.

10. The transformer with lightning protection structure according to claim 6, characterized in that, A connecting wire is provided between the terminal block and the winding. A conductive branch is provided at one end of the connecting wire near the lightning protection conductive plate. The conductive branch is fixedly connected to the lightning protection conductive plate.

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