A high-voltage surge arrester with built-in self-balancing electrodes

Abstract

The application discloses a high-voltage lightning arrester with built-in self-balancing electrodes, comprising an upper end electrode, a self-balancing valve piece group, a plurality of standard zinc oxide valve pieces, a lower end electrode and an insulating outer cover. The self-balancing valve piece group is arranged at the first section of the high-voltage end of the valve piece column, and a coaxial annular self-balancing electrode is embedded in the valve piece ceramic base, which, together with the upper end surface electrode and the upper medium layer, forms a built-in compensation capacitor. Under the steady-state power frequency voltage, the axial injection current generated by the built-in compensation capacitor is equal in size and opposite in direction to the shunt current of the ground stray capacitance at this position, and the reverse balance is realized locally in the valve piece, thereby eliminating the uneven distribution of the axial voltage of the valve piece column from the root. Under the condition of a large impact current, the annular self-balancing electrode is automatically equipotential with the surrounding ceramic base. The application does not need external voltage equalizing rings and parallel voltage equalizing capacitors, and realizes excellent voltage equalization effect without secondary performance cost under the premise of not changing the size of the lightning arrester, and is suitable for compact high-voltage lightning arresters of various voltage grades.

Description

Technical Field

[0001] This invention relates to the field of power system overvoltage protection equipment technology, and in particular to a high-voltage surge arrester with built-in self-balancing electrodes. Background Technology

[0002] Zinc oxide surge arresters are core devices in power systems that limit overvoltage and protect the insulation of transmission and transformation equipment. Their core working element is a valve column formed by multiple zinc oxide valve plates stacked in series along the axial direction. Composite-insulated surge arresters use epoxy fiberglass insulating cylinders as inner insulation and silicone rubber sheds as outer insulation. They have advantages such as light weight, good pollution resistance, and excellent explosion-proof performance, and are widely used in power systems.

[0003] Under steady-state power frequency operating voltage, stray capacitance to ground exists at various positions on the valve plate column of a vertically installed surge arrester. Along the axial direction from the high-voltage end to the grounding end, a portion of the axial current of each valve plate flows to the ground through the stray capacitance, forming a gradually decreasing current gradient. Due to the nonlinear volt-ampere characteristics of zinc oxide valve plates in the low-current region, the voltage increases as the current decreases, resulting in the voltage borne by the first section of the valve plate at the high-voltage end reaching up to 1.8 times the average voltage of the entire column. Under long-term operation, the electrical and thermal aging rates of the first section of the valve plate increase exponentially. The service life of the entire surge arrester is entirely determined by the first section of the valve plate, which deteriorates the fastest, becoming the core bottleneck restricting the reliability and lifespan of the surge arrester.

[0004] To improve the uneven voltage distribution of the valve plate column, the industry conventionally adopts two types of technical solutions. The first type is an external voltage equalization device, a typical example being the capacitorless surge arrester disclosed in patent document CN201397717Y. This type of arrester distorts the electric field and alleviates uneven voltage distribution by optimizing the structural parameters such as the outer diameter and depth of the voltage equalization ring on the high-voltage side. This type of solution is technically mature and widely used, but it has inherent drawbacks: the voltage equalization ring increases the radial dimension of the surge arrester by 3 to 5 times, making it unsuitable for installation spaces with limited space, such as GIS gas-insulated switchgear and compact switchgear; at the same time, the voltage equalization ring is prone to corona loss, and flashover is likely to occur after surface contamination, bringing new fault risks. Some solutions use a parallel voltage equalization capacitor next to the valve plate column to replace the voltage equalization ring, but the long-term reliability of the capacitor element is low, and it will degrade the impulse response characteristics, which also has secondary costs.

[0005] The second category involves optimizing valve plate structural parameters. A typical example is the small-diameter valve plate solution disclosed in patent document CN113823470B, which redistributes voltage and reduces the charge rate of the first valve plate by reducing the diameter of the controllable portion of the high-voltage side and increasing its resistance. Another example is the high-gradient valve plate solution disclosed in patent document CN101383209A, which uses a high-voltage gradient zinc oxide valve plate to shorten the total length of the valve plate column and reduces the impact of stray capacitance to ground by reducing the overall height. Although this type of solution avoids external additional devices, it essentially alleviates unevenness by sacrificing some performance parameters. The physical mechanism of uneven voltage distribution is not eliminated, and it brings new problems such as reduced current carrying capacity and increased valve plate cost. The voltage equalization effect is also very limited.

[0006] In summary, existing surge arrester voltage equalization technologies are consistently trapped in a trade-off between performance and cost: externally added solutions offer better voltage equalization but incur higher structural costs, while internal parameter optimization solutions have lower structural costs but limited voltage equalization effects. All solutions follow the technical approach of "external suppression or overall adaptation," never addressing the root cause of side effects or achieving reverse equalization and elimination of unevenness within a localized area. Therefore, developing a high-voltage surge arrester that requires no external voltage equalization devices, incurs no secondary performance costs, and eliminates voltage unevenness at its source is a pressing technical problem in this field. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a high-voltage surge arrester with a built-in self-balancing electrode. By embedding a ring-shaped self-balancing electrode inside the first-stage valve plate, and using the valve plate's own ceramic as a dielectric to form a built-in compensation capacitor, reverse current is directly injected into the localized location caused by stray capacitance shunting to achieve balancing, thereby eliminating uneven voltage distribution from the root cause. Furthermore, it eliminates the need for external voltage equalization devices and incurs no secondary performance costs.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A high-voltage surge arrester with a built-in self-balancing electrode includes an upper electrode, a self-balancing valve plate group, several standard zinc oxide valve plates, a lower electrode, and an insulating jacket. The upper electrode, the self-balancing valve plate group, the several standard zinc oxide valve plates, and the lower electrode are sequentially connected in series along the axial direction to form a valve plate column, and the insulating jacket coaxially covers the outside of the valve plate column. The self-balancing valve plate group is located at the high-voltage end of the valve plate column and is disposed adjacent to the upper electrode. The self-balancing valve plate group includes at least one self-balancing valve plate, which includes a valve plate ceramic substrate, an upper end face electrode, a lower end face electrode, and at least one annular self-balancing electrode. The upper end face electrode and the lower end face electrode are respectively disposed on the upper and lower end face surfaces of the valve plate ceramic substrate. The annular self-balancing electrode is embedded inside the valve plate ceramic substrate, forming an upper dielectric layer between itself and the upper end face electrode, and a lower resistive layer between itself and the lower end face electrode. The ring-shaped self-balancing electrode, together with the upper end face electrode and the upper dielectric layer, constitutes a built-in compensation capacitor. The capacitance of the built-in compensation capacitor is configured such that, under steady-state power frequency voltage, the axial injection current generated by the built-in compensation capacitor is equal in magnitude and opposite in direction to the shunt current of the stray capacitance to ground of the valve plate at that position, thereby locally canceling the shunt effect of the stray capacitance to ground inside the valve plate.

[0009] Furthermore, the self-balancing valve plate assembly contains 2 to 3 self-balancing valve plates, all of which are arranged at the high-pressure end of the valve plate column, while the remaining positions are filled with standard zinc oxide valve plates. The outer diameter of the self-balancing valve plates is exactly the same as that of the standard zinc oxide valve plates.

[0010] Furthermore, the embedment depth of the annular self-balancing electrode is 1 / 4 to 1 / 3 of the axial thickness of the valve ceramic substrate. The embedment depth is measured from the upper end face electrode to the lower end face electrode, and the annular self-balancing electrode is coaxially arranged with the valve ceramic substrate.

[0011] Furthermore, the outer diameter of the annular self-balancing electrode is 0.6 to 0.8 times the outer diameter of the valve ceramic substrate, the annular width is 5 to 15 mm, and the thickness is 0.2 to 0.5 mm.

[0012] Furthermore, the annular self-balancing electrode is made of a high-temperature resistant metal, specifically tungsten, molybdenum, or their alloys, and is integrally formed with the valve plate ceramic substrate through a co-firing process.

[0013] Furthermore, the upper dielectric layer and the lower resistive layer are made of zinc oxide ceramic material with the same formulation. The upper dielectric layer exhibits dielectric capacitance characteristics under steady-state power frequency, while the lower resistive layer exhibits zinc oxide nonlinear resistive characteristics.

[0014] Furthermore, under steady-state power frequency voltage, the capacitance value of the built-in compensation capacitor satisfies the following relationship: ; Where C is the capacitance of the built-in compensation capacitor, Cs is the stray capacitance to ground of the single valve plate at this position, h is the thickness of the lower resistive layer, and d is the thickness of the upper dielectric layer.

[0015] Furthermore, under high-current impact conditions, the ceramic substrate of the valve plate enters a low-resistance state, and the annular self-balancing electrode and the surrounding ceramic substrate of the valve plate automatically reach the same potential, becoming part of the resistance path, without changing the impact residual voltage and current flow characteristics of the valve plate.

[0016] Furthermore, the insulating jacket includes an epoxy glass fiber insulating cylinder and a silicone rubber umbrella sleeve installed on the outer wall of the epoxy glass fiber insulating cylinder. The high-voltage end of the surge arrester does not have an external equalizing ring and a parallel equalizing capacitor. The overall radial dimension is consistent with that of a conventional surge arrester of the same voltage level without an equalizing device.

[0017] Furthermore, the annular self-balancing electrode includes an inner conductive part on the inner side and a radial gradient field control ring on the outer periphery. The inner conductive part is made of a high-temperature resistant metal material, and the radial gradient field control ring is made of a doped zinc oxide-based metal ceramic material. Its resistivity gradually increases radially from the inside to the outside, forming a continuous resistance gradient. The outer edge of the radial gradient field control ring extends to the side surface close to the ceramic substrate of the valve plate.

[0018] Compared with the prior art, the present invention has the following beneficial effects: First, this invention directly addresses the physical essence of steady-state voltage unevenness. Through the built-in compensation capacitor within the valve plate, reverse current is directly injected into the localized location caused by stray capacitance shunting, achieving precise reverse balancing at the vector level and eliminating the voltage concentration effect of the first-stage valve plate at its root. Unlike existing technologies that only alleviate unevenness, this invention makes the operating voltage of the entire valve plate more uniform, synchronizing aging rates and completely changing the failure mode where "the shortest component in the first stage determines the overall lifespan." This source-level balancing method is not limited by voltage level or valve plate formulation, and its balancing effect is far superior to external voltage equalization solutions. It can fundamentally delay the steady-state degradation of the surge arrester and extend its service life.

[0019] Secondly, this invention completely abandons the conventional approach of using external pressure equalization devices, integrating the pressure equalization function entirely within the valve plate. This eliminates the risks of radial dimensional expansion, corona loss, and contamination associated with pressure equalization rings, and avoids reliability issues and impact performance degradation caused by parallel capacitors. Simultaneously, utilizing the nonlinear characteristics of zinc oxide material, the annular self-balancing electrode automatically achieves equipotentiality under impact conditions, without affecting the valve plate's current-carrying capacity or residual pressure characteristics. The optimized steady-state pressure equalization benefits come without any secondary performance cost. This achievement overcomes the long-standing industry prejudice that "pressure equalization effect cannot be simultaneously achieved with structural dimensions and impact performance," realizing a truly cost-free performance improvement.

[0020] Third, all improvements in this invention are limited to the internal components of the first 2-3 valve plates; all other parts, dimensions, installation interfaces, and assembly processes are completely identical to conventional surge arresters. This localized improvement approach allows the surge arrester of this invention to directly replace existing conventional products without altering system installation dimensions or maintenance procedures, exhibiting strong process inheritance and extremely low mass production and promotion costs. Furthermore, this design concept of "completing offsetting effects within a very small range without changing the rest of the system" is entirely different from the external addition or overall optimization approaches of existing technologies. It lacks clear technical inspiration in this field and possesses extremely strong patent inventiveness and technological barriers.

[0021] Fourth, the built-in self-balancing structure of this invention possesses inherent adaptive capability under various operating conditions: it exhibits capacitive compensation characteristics in steady state, achieving voltage equalization; under impulse conditions, it automatically switches to a conductive path, retaining complete current-carrying performance. The added radial gradient field control ring can also simultaneously improve the radial electric field distribution at the valve edge, suppressing lateral corona and surface aging, and automatically enters a low-resistance state under impulse conditions, promoting uniform radial current diffusion and further enhancing current-carrying capacity. This multi-condition adaptive characteristic allows the surge arrester to maintain optimal performance under various operating conditions. Simultaneously, due to the elimination of the external equalizing ring, the radial dimension of the surge arrester is significantly reduced, enabling its widespread application in confined spaces where traditional surge arresters are unsuitable, such as GIS gas-insulated switchgear, compact switchgear, and underground power distribution equipment, greatly expanding the application boundaries of zinc oxide surge arresters. Attached Figure Description

[0022] Figure 1 This is an axial cross-sectional view of the overall structure of the surge arrester of the present invention; Figure 2 This is a schematic diagram of the internal structure of the self-balancing valve plate of the present invention; Figure 3 This is a schematic diagram of the steady-state operation equivalent circuit and current cancellation principle of the present invention; Figure 4 This is a comparison of the axial voltage distribution of the valve plate column in this invention.

[0023] In the figure: 1—upper electrode, 2—self-balancing valve plate assembly, 21—valve plate ceramic substrate, 22—upper end face electrode, 23—lower end face electrode, 24—ring self-balancing electrode, 25—upper dielectric layer, 26—lower resistive layer, 3—standard zinc oxide valve plate, 4—lower electrode, 5—insulating jacket, 51—epoxy glass fiber insulating cylinder, 52—silicone rubber umbrella sleeve. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] Example 1: like Figure 1-4 As shown, this embodiment provides a high-voltage surge arrester with built-in self-balancing electrodes, suitable for AC power systems with a voltage level of 110kV, used to limit system overvoltage and protect power transmission and transformation equipment from damage caused by lightning and switching overvoltage.

[0026] The surge arrester consists of an upper electrode 1, a self-balancing valve plate assembly 2, several standard zinc oxide valve plates 3, a lower electrode 4, and an insulating jacket 5. The upper electrode 1, self-balancing valve plate assembly 2, several standard zinc oxide valve plates 3, and lower electrode 4 are sequentially connected in series along the axial direction to form a complete valve plate column. The insulating jacket 5 coaxially covers the outside of the valve plate column, and both ends are sealed by a sealing structure. The interior can be filled with dry air or sulfur hexafluoride gas, or a solid composite insulation structure can be used.

[0027] The upper electrode 1 is made of aluminum alloy and has a terminal block at the top for connection to the high-voltage busbar. Its lower surface is a flat conductive surface that makes close contact with the upper electrode 22 of the first self-balancing valve plate, ensuring good electrical conductivity. The lower electrode 4 is also made of aluminum alloy and has a mounting flange and grounding terminal at the bottom for fixing the surge arrester to the bracket and achieving reliable grounding. Its upper surface is a flat conductive surface that makes close contact with the lower electrode of the last standard zinc oxide valve plate 3.

[0028] The insulating jacket 5 includes an epoxy glass fiber insulating cylinder 51 and a silicone rubber awning 52 disposed on the outer wall of the epoxy glass fiber insulating cylinder 51. The epoxy glass fiber insulating cylinder 51 is made of glass fiber impregnated with epoxy resin and then produced by drawing or winding processes, possessing high mechanical strength and insulation performance. The silicone rubber awning 52 is coated on the outer wall of the epoxy glass fiber insulating cylinder 51 by high-temperature vulcanization or injection molding processes. The awning structure is used to increase the creepage distance and improve the dirt resistance.

[0029] The self-balancing valve plate assembly 2 is located at the high-voltage end of the valve plate column, adjacent to the upper electrode 1. In this embodiment, the self-balancing valve plate assembly 2 includes two identical self-balancing valve plates, which are stacked in series at the first section of the high-voltage end. The remaining part of the valve plate column is composed of 12 standard zinc oxide valve plates 3 stacked in series. The standard zinc oxide valve plates 3 are industry-standard conventional zinc oxide resistance plates, possessing standard nonlinear volt-ampere characteristics and current-carrying capacity. The outer diameter and thickness of the self-balancing valve plates are completely consistent with the standard zinc oxide valve plates 3, ensuring the coaxiality and assembly consistency of the entire valve plate column without requiring any changes to tooling fixtures or assembly processes.

[0030] like Figure 2 As shown, each self-balancing valve plate includes a valve plate ceramic substrate 21, an upper end face electrode 22, a lower end face electrode 23, and an annular self-balancing electrode 24. The upper end face electrode 22 and the lower end face electrode 23 are respectively disposed on the upper and lower end faces of the valve plate ceramic substrate 21, and are prepared by aluminum spraying or silver infiltration processes. An insulating edge of a certain width is reserved at the electrode edge to prevent surface flashover. The annular self-balancing electrode 24 is embedded inside the valve plate ceramic substrate 21, forming an upper dielectric layer 25 between it and the upper end face electrode 22, and a lower resistive layer 26 between it and the lower end face electrode 23.

[0031] The ceramic substrate 21 of the valve plate is a zinc oxide-based varistor ceramic, with zinc oxide as the main component and doped with various additives such as bismuth oxide, cobalt oxide, manganese oxide, and antimony oxide. It is formed by spray granulation, pressing, and high-temperature sintering, exhibiting excellent nonlinear current-voltage characteristics. The upper dielectric layer 25 and the lower resistive layer 26 use the exact same ceramic formula and are integrally formed during sintering, without interface delamination, ensuring consistency in mechanical strength and electrical performance. Under steady-state power frequency voltage, the upper dielectric layer 25, due to its thinner thickness, has a higher electric field strength and mainly exhibits dielectric capacitance characteristics; the lower resistive layer 26, with its greater thickness, bears the main voltage drop and exhibits the nonlinear resistive characteristics of zinc oxide.

[0032] The annular self-balancing electrode 24 is made of high-temperature resistant molybdenum metal and is fabricated into a thin annular sheet structure with a thickness of 0.3~0.5mm. During the valve plate pressing stage, the pre-fabricated annular self-balancing electrode 24 is placed into the ceramic powder at a predetermined depth, and then pressed together to form a green body. A high-temperature co-firing process is then performed to ensure that the annular self-balancing electrode 24 is tightly bonded to the ceramic substrate, forming an integral structure. This co-firing process ensures that there are no air gaps between the electrode and the ceramic, avoiding the risk of partial discharge, while also ensuring the mechanical stability of the structure.

[0033] In this embodiment, the total thickness of the single valve plate is 22 mm, the embedment depth of the annular self-balancing electrode 24 is 6 mm, that is, the thickness of the upper dielectric layer 25 is 6 mm, and the thickness of the lower resistive layer 26 is 16 mm. The outer diameter of the annular self-balancing electrode 24 is 42 mm, the outer diameter of the valve plate ceramic substrate 21 is 56 mm, and the annular width is 7 mm. With the above parameter configuration, the built-in compensation capacitor of the single self-balancing valve plate is approximately 12 pF.

[0034] Example 2: Based on Example 1, this embodiment details the voltage self-balancing principle and parameter matching method during steady-state power frequency operation.

[0035] Under steady-state power frequency operating voltage, stray capacitance exists between the surge arrester valve plates and ground. A portion of the axial current of each valve plate flows to the ground through this stray capacitance, creating a current shunting effect. The closer to the high-voltage end, the more pronounced the current shunting effect of the stray capacitance, resulting in a lower axial current in the first valve plate section compared to the middle and later sections, leading to a higher voltage drop and uneven axial voltage distribution. In conventional surge arresters, the voltage borne by the first valve plate section can reach 1.8 to 2.2 times the average voltage. Under long-term operation, the aging rate of the first valve plate section is significantly faster than that of the other valve plates, becoming the shortest link in the lifespan of the entire surge arrester.

[0036] In this embodiment, the annular self-balancing electrode 24 inside the self-balancing valve plate, together with the upper end electrode 22 and the upper dielectric layer 25, constitutes a built-in planar compensation capacitor. Under the action of power frequency AC voltage, this compensation capacitor generates capacitive current. The current flows from the upper end electrode 22 through the upper dielectric layer 25 to the annular self-balancing electrode 24, and then through the lower resistive layer 26 to the lower end electrode 23, forming an additional axial injection current. The direction of this injection current is exactly opposite to the shunting direction of the stray capacitor to ground: the stray capacitor to ground shuns the axial current outward, while the built-in compensation capacitor injects current inward into the resistive layer.

[0037] By precisely matching the capacitance value of the built-in compensation capacitor, the injected current is made equal to the shunt current of the stray capacitance to ground at that location, achieving reverse balance between the two within the local space inside the valve plate. After balance, the axial current of the lower resistive layer 26 returns to the average current level of the entire valve plate, and the corresponding voltage drop is also equal to the average voltage drop of the entire column, thus completely eliminating the voltage concentration phenomenon in the first section of the valve plate. Calculations show that after adopting the scheme of this embodiment, the voltage distribution non-uniformity coefficient of the entire valve plate can be reduced to below 1.05, which is far better than the 1.2~1.4 of the conventional equalizing ring scheme.

[0038] The capacitance matching of the built-in compensation capacitor can be determined by the following formula: ; Where C is the capacitance of the built-in compensation capacitor, Cs is the stray capacitance to ground of the single valve plate at this position, h is the thickness of the lower resistive layer 26, and d is the thickness of the upper dielectric layer 25.

[0039] The derivation logic of this relationship is as follows: To achieve reverse current balance, the capacitive current of the built-in compensation capacitor must be equal to the shunt current of the stray capacitance to ground, i.e., C·ω·ΔU = Cs·ω·U, where ΔU is the voltage across the upper dielectric layer 25, and U is the total voltage of a single valve plate. Since the upper dielectric layer 25 and the lower resistive layer 26 are connected in series for voltage division, and the capacitive reactance is much larger than the equivalent resistance of the lower resistive region in steady state, most of the voltage drop occurs in the upper dielectric layer 25. The ratio of ΔU to U is approximately equal to the ratio of the upper dielectric layer thickness d to the total valve plate thickness. Combining the relationship between the lower resistive layer thickness h and the total thickness, the above capacitance matching formula can be simplified to obtain.

[0040] Taking typical parameters of a 110kV surge arrester as an example, the stray capacitance to ground of a single valve piece, Cs, is approximately 5~20pF. The thickness of the lower resistive layer, h, is 16mm, and the thickness of the upper dielectric layer, d, is 6mm. Substituting these values ​​into the formula, the target value of the built-in compensation capacitor is approximately 13~53pF. In this embodiment, by adjusting the outer diameter of the annular self-balancing electrode 24, the built-in compensation capacitor is configured to approximately 12pF, which is on the same order of magnitude as the stray capacitance to ground of the first valve piece, achieving a good balancing effect. For the second self-balancing valve piece, since its stray capacitance to ground is slightly smaller than that of the first piece, the outer diameter of the annular self-balancing electrode 24 can be appropriately reduced to match a smaller capacitance value, achieving precise balancing of each piece.

[0041] Example 3: This embodiment, based on Embodiment 1, details the adaptive characteristics under high-current impact conditions.

[0042] When a lightning strike or switching overvoltage occurs in the system, a large surge current acts on the surge arrester, causing the zinc oxide varistor to instantly enter a low-resistance state, and the electric field strength inside the varistor changes drastically. At this time, the annular self-balancing electrode 24 quickly reaches equipotential with the surrounding ceramic substrate through displacement current, essentially becoming part of the resistive body, and does not impede the axial flow of the surge current.

[0043] Under impact conditions, the upper dielectric layer 25 no longer acts as a capacitor blocking DC layer, and the entire self-balancing valve plate is equivalent to a complete low-resistance zinc oxide valve plate. The impact current flows from the upper end electrode 22 through the entire valve plate ceramic substrate 21 to the lower end electrode 23, and the annular self-balancing electrode 24 does not constitute additional impedance or capacitive obstruction. Therefore, the key impact characteristics of the self-balancing valve plate, such as impact residual voltage, current carrying capacity, and energy absorption capacity, are completely consistent with those of the standard zinc oxide valve plate 3, and there will be no performance degradation due to the built-in annular self-balancing electrode 24.

[0044] In other words, the surge arrester in this embodiment achieves excellent voltage equalization under steady-state conditions while fully retaining the impulse performance of conventional varistors. The optimized benefits do not come at any secondary performance cost, truly achieving a cost-free performance improvement. This effect is unattainable by traditional external voltage equalization schemes: although traditional voltage equalization rings can improve voltage distribution, they bring a series of secondary problems such as increased radial dimensions, corona loss, and flashover due to pollution accumulation; parallel voltage equalization capacitors bring costs such as reduced reliability, increased cost, and slower impulse response.

[0045] This adaptive characteristic stems from the nonlinear current-voltage characteristics of the zinc oxide material itself and the floating design of the annular self-balancing electrode 24. The annular self-balancing electrode 24 is not directly connected to any external electrode; its potential is entirely determined by the electric field distribution of the surrounding ceramic substrate. In steady state, due to the capacitive voltage division effect of the upper dielectric layer 25, the potential of the annular self-balancing electrode 24 lies between the upper end electrode 22 and the lower end electrode 23, forming effective capacitive compensation. Under impact, the resistivity of the ceramic substrate drops sharply, and the annular self-balancing electrode 24 quickly becomes equipotential with the entire substrate through the low-resistivity ceramic, no longer acting as a capacitor plate. The functional switching between the two operating conditions is entirely achieved automatically by the material's physical properties, requiring no control circuits or mechanical switches, resulting in extremely high reliability.

[0046] Example 4: Based on Example 1, this embodiment improves the structure of the annular self-balancing electrode 24 by adding a radial gradient field control ring.

[0047] While the original solution addressed the uneven axial voltage distribution, the first section of the valve plate also suffers from radial edge electric field concentration. The edge electric field strength of the high-voltage valve plate is much higher than that in the central region, which can easily lead to lateral corona, surface aging, and flashover risks during long-term operation. Existing technologies typically coat the valve plate with a semi-conductive glaze to improve the edge electric field, but this increases leakage current, and the glaze layer is prone to aging and peeling, resulting in insufficient reliability.

[0048] To address the aforementioned issues, the annular self-balancing electrode 24 in this embodiment comprises an inner conductive portion and an outer radial gradient field control ring, both of which are co-fired integrally. The inner conductive portion is made of high-temperature resistant molybdenum metal and formed into a circular thin sheet structure, serving as the lower electrode of the built-in compensation capacitor. The radial gradient field control ring is made of doped zinc oxide-based cermet material. By adjusting the concentration gradient of dopants such as cobalt and manganese, the resistivity gradually increases radially from the inside out, forming a continuous resistance gradient. The inner edge of the radial gradient field control ring is tightly bonded to the outer edge of the inner conductive portion, with the outer edge extending to a position close to the side surface of the valve ceramic substrate 21.

[0049] Under steady-state power frequency voltage, the radial gradient field control ring exhibits a high-resistivity state, with the resistivity gradually increasing radially outwards. The corresponding voltage drop also gradually changes radially, thus gradually dispersing the concentrated electric field at the valve edge, reducing the peak electric field intensity in the edge region, suppressing side corona generation, and slowing down surface aging. Compared to traditional side-coated semi-conductive glaze solutions, the embedded radial gradient field control ring eliminates the problems of glaze peeling and aging, resulting in higher reliability and no increase in surface leakage current of the valve.

[0050] When a large surge current arrives, the radial gradient field-controlled loop automatically enters a low-resistivity state under the influence of a strong electric field. The nonlinear characteristics of zinc oxide cause its resistivity to drop sharply, creating an excellent conductive path. At this point, the radial gradient field-controlled loop actually expands the current path, promoting a uniform distribution of the surge current radially across the valve plate and preventing current concentration in the central region, thereby enhancing the valve plate's current-carrying capacity and energy absorption capacity. In other words, the radial gradient field-controlled loop improves the electric field in steady state and increases current-carrying capacity under surge, not only without any side effects but also bringing additional performance gains.

[0051] This dual-function design integrates axial voltage equalization and radial electric field equalization into a single annular self-balancing electrode 24, eliminating the need for additional components and processes, and simultaneously addressing two sources of steady-state degradation. Furthermore, it suppresses the side effect of radial electric field inhomogeneity within its localized region through internal structural equalization, rather than through external coatings or additional shielding.

[0052] Example 5: This embodiment provides a method for manufacturing the above-mentioned high-voltage surge arrester with built-in self-balancing electrodes: Step 1: Powder preparation. Weigh the main zinc oxide and additives such as bismuth oxide, cobalt oxide, manganese oxide, and antimony oxide according to the conventional zinc oxide valve plate formula. Add deionized water and dispersant, and mix by ball milling for 24 hours. Then add binder and spray granulate to obtain ceramic powder with good flowability.

[0053] Step 2: Pressing the lower green body. Take a portion of ceramic powder, add it to the mold and pre-press it to form the green body of the lower resistance layer 26. The thickness is determined according to the design requirements (in this example, the green body thickness is 16mm after sintering).

[0054] Step 3: Placement of the annular self-balancing electrode. Place the pre-fabricated annular self-balancing electrode 24 (molybdenum sheet, 0.3mm thick) at the center of the upper surface of the lower green body, ensuring coaxiality using mold positioning pins. For the radial gradient field control ring in Example 4, gradient-doped ceramic powder needs to be laid around the outer periphery of the molybdenum ring and placed together with it.

[0055] Step 4: Upper Green Body Pressing. Upper ceramic powder is filled above the annular self-balancing electrode 24, and a second overall pressing is performed at a pressure of approximately 50-100 MPa, forming a single green body from the upper dielectric layer 25, the annular self-balancing electrode 24, and the lower resistive layer 26. The green body thickness of the upper dielectric layer 25 is calculated based on the sintering shrinkage rate to correspond to a thickness of 6 mm after sintering.

[0056] Step 5: Debinding. Place the green blank in a debinding furnace and heat it to 400-600°C at a rate of 0.5-1°C / min. Hold it at this temperature for 2-4 hours to remove the binder and prevent bubbles or cracks from forming during sintering.

[0057] Step Six: Co-firing. The debinded green body is placed in a high-temperature sintering furnace and heated to 1100-1200°C at a rate of 2-3°C / min under a reducing atmosphere of nitrogen or nitrogen plus hydrogen. It is held at this temperature for 2-4 hours, and then cooled in the furnace. The reducing atmosphere ensures that the molybdenum electrode is not oxidized at high temperatures, while simultaneously allowing the zinc oxide ceramic to acquire the desired microstructure and electrical properties.

[0058] Step 7: End face machining. After sintering, grind both ends of the valve plate to the specified thickness (22mm in this example) to ensure that the flatness and parallelism of both ends meet the requirements.

[0059] Step 8: Electrode preparation. Aluminum-impregnated electrodes or zinc-aluminum electrodes are fired onto both ends of the valve plate to form the upper end electrode 22 and the lower end electrode 23. An insulating edge of 3-5 mm is reserved at the edge of the electrodes.

[0060] Step Nine: Performance Testing. The prepared self-balancing valve plates are subjected to volt-ampere characteristic testing, power frequency reference voltage testing, impulse current residual voltage testing, and partial discharge testing to screen qualified products.

[0061] Step 10: Surge Arrester Assembly. Stack the two self-balancing valve plates and twelve standard zinc oxide valve plates 3 in sequence. Install the upper electrode 1 and lower electrode 4 at both ends. Insert the entire assembly into the epoxy fiberglass insulation cylinder 51. After sealing both ends, inject or install silicone rubber shed sleeves 52 to complete the surge arrester assembly. The assembly process is completely consistent with conventional surge arresters; only the first two standard valve plates need to be replaced with self-balancing valve plates.

[0062] The above manufacturing process is highly compatible with existing zinc oxide valve plate production lines. The main new process is the placement of the annular self-balancing electrode and the secondary stacking and pressing, which can be achieved on existing presses by changing the mold, resulting in low cost for mass production modification.

[0063] Example 6: This example illustrates the parameter adaptation method of the present invention at different voltage levels.

[0064] The technical solution of this invention is applicable to surge arresters of various voltage levels, such as 35kV, 110kV, 220kV, and 500kV. For different voltage levels, the same voltage equalization effect can be achieved by adjusting the number of self-balancing valves, the diameter and embedment depth of the annular self-balancing electrode 24, and matching the stray capacitance parameters to ground for the corresponding voltage level.

[0065] For a 35kV voltage level, the valve column typically contains 6 to 8 valves, resulting in relatively small stray capacitance to ground and a relatively mild degree of voltage unevenness in the initial stage. In this case, the self-balancing valve group 2 can be equipped with only one self-balancing valve, the outer diameter of the annular self-balancing electrode 24 can be appropriately reduced, and the target value of the built-in compensation capacitor is approximately 5 to 10 pF.

[0066] For the 110kV voltage level, as described in Example 1, two self-balancing valve plates are set, and the target value of the built-in compensation capacitor is about 10~15pF.

[0067] For a 220kV voltage level, the valve column typically contains 30 to 40 valves. The stray current accumulation effect in the first stage is more significant. The self-balancing valve group 2 is equipped with 2 to 3 self-balancing valves, and the built-in compensation capacitor has a target value of approximately 15 to 20pF.

[0068] For a 500kV voltage level, the valve column usually contains 80 to 100 valves, and the problem of voltage unevenness is the most prominent. The self-balancing valve group 2 is equipped with 3 self-balancing valves, and the built-in compensation capacitor has a target value of about 20 to 25pF.

[0069] At each voltage level, the outer diameter of the self-balancing valve plate is consistent with that of the standard zinc oxide valve plate 3 at that voltage level. The overall dimensions and installation interface of the surge arrester are compatible with conventional surge arresters of the same voltage level and can be directly replaced.

[0070] Furthermore, for special application scenarios such as GIS tank-type surge arresters and surge arresters for compact switchgear, traditional surge arresters with equipotential rings cannot be used due to limited installation space. However, since the present invention eliminates the external equipotential ring, its radial dimensions are consistent with those of conventional surge arresters without equipotential rings, which can perfectly adapt to these narrow installation scenarios and greatly expand the application range of zinc oxide surge arresters.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-voltage surge arrester with a built-in self-balancing electrode, comprising an upper electrode (1), a self-balancing valve plate group (2), several standard zinc oxide valve plates (3), a lower electrode (4), and an insulating jacket (5), wherein the upper electrode (1), the self-balancing valve plate group (2), the several standard zinc oxide valve plates (3), and the lower electrode (4) are sequentially connected in series along the axial direction to form a valve plate column, and the insulating jacket (5) is coaxially wrapped around the outside of the valve plate column, characterized in that: The self-balancing valve plate assembly (2) is located at the high-pressure end of the valve plate column, adjacent to the upper electrode (1); the self-balancing valve plate assembly (2) includes at least one self-balancing valve plate, the self-balancing valve plate including a valve plate ceramic substrate (21), an upper end face electrode (22), a lower end face electrode (23) and at least one annular self-balancing electrode (24); the upper end face electrode (22) and the lower end face electrode (23) are respectively disposed on the upper and lower end faces of the valve plate ceramic substrate (21); the annular self-balancing electrode (24) is embedded in the valve plate ceramic substrate (21). The upper dielectric layer (25) is formed between the upper end face electrode (22) and the lower end face electrode (23), and the lower resistive layer (26) is formed between the upper end face electrode (23). The annular self-balancing electrode (24), together with the upper end face electrode (22) and the upper dielectric layer (25), constitutes a built-in compensation capacitor. The capacitance value of the built-in compensation capacitor is configured such that, under steady-state power frequency voltage, the axial injection current generated by the built-in compensation capacitor is equal in magnitude and opposite in direction to the shunt current of the stray capacitance to ground of the valve plate at this position, thereby locally canceling the shunt effect of the stray capacitance to ground inside the valve plate.

2. The high-voltage surge arrester with built-in self-balancing electrodes according to claim 1, characterized in that: The self-balancing valve plate group (2) contains 2 to 3 self-balancing valve plates, all of which are arranged at the high-pressure end of the valve plate column, and the remaining positions are standard zinc oxide valve plates (3). The outer diameter of the self-balancing valve plate is completely consistent with the outer diameter of the standard zinc oxide valve plate (3).

3. The high-voltage surge arrester with built-in self-balancing electrodes according to claim 1, characterized in that: The embedment depth of the annular self-balancing electrode (24) is 1 / 4 to 1 / 3 of the axial thickness of the valve ceramic substrate (21). The embedment depth is measured from the upper end face electrode (22) to the lower end face electrode (23) with reference as the reference. The annular self-balancing electrode (24) is coaxially arranged with the valve ceramic substrate (21).

4. The high-voltage surge arrester with built-in self-balancing electrodes according to claim 1, characterized in that: The outer diameter of the annular self-balancing electrode (24) is 0.6 to 0.8 times the outer diameter of the valve ceramic substrate (21), the annular width is 5 to 15 mm, and the thickness is 0.2 to 0.5 mm.

5. The high-voltage surge arrester with built-in self-balancing electrodes according to claim 1, characterized in that: The annular self-balancing electrode (24) is made of high-temperature resistant metal material, specifically tungsten, molybdenum or their alloys, and is integrally formed with the valve plate ceramic substrate (21) by co-firing process.

6. The high-voltage surge arrester with built-in self-balancing electrodes according to claim 1, characterized in that: The upper dielectric layer (25) and the lower resistive layer (26) are made of zinc oxide ceramic material with the same formulation. The upper dielectric layer (25) exhibits dielectric capacitance characteristics under steady-state power frequency, while the lower resistive layer (26) exhibits zinc oxide nonlinear resistance characteristics.

7. The high-voltage surge arrester with built-in self-balancing electrodes according to claim 1, characterized in that: Under steady-state power frequency voltage, the capacitance value of the built-in compensation capacitor satisfies the following relationship: ； in, This refers to the capacitance value of the built-in compensation capacitor. This refers to the stray capacitance to ground of a single valve disc at this location. The thickness of the lower resistive layer (26) is... The thickness of the upper dielectric layer (25) is given.

8. The high-voltage surge arrester with built-in self-balancing electrodes according to claim 1, characterized in that: Under the condition of high impact current, the ceramic substrate (21) of the valve plate enters a low resistance state, and the annular self-balancing electrode (24) and the surrounding ceramic substrate (21) automatically reach the same potential, becoming part of the resistance path, without changing the impact residual pressure and current flow characteristics of the valve plate.

9. The high-voltage surge arrester with built-in self-balancing electrodes according to claim 1, characterized in that: The insulating jacket (5) includes an epoxy glass fiber insulating cylinder (51) and a silicone rubber umbrella sleeve (52) disposed on the outer wall of the epoxy glass fiber insulating cylinder (51). The high-voltage end of the surge arrester is not provided with an external equalizing ring and a parallel equalizing capacitor. The overall radial dimension is consistent with that of a conventional surge arrester without an equalizing device at the same voltage level.

10. The high-voltage surge arrester with built-in self-balancing electrodes according to claim 1, characterized in that: The annular self-balancing electrode (24) includes an inner conductive part and an outer radial gradient field control ring. The inner conductive part is made of a high-temperature resistant metal material, and the radial gradient field control ring is made of a doped zinc oxide-based metal ceramic material. Its resistivity gradually increases radially from the inside to the outside, forming a continuous resistance gradient. The outer edge of the radial gradient field control ring extends to the side surface close to the valve ceramic substrate (21).

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