Low-residual-voltage and high-current-passing lightning arrester for high-altitude transmission and distribution line

Abstract

An implementation approach of high-performance low-residual-voltage extra-high-voltage lightning arrester, including reducing donor density, increasing grain boundary surface state density, reducing grain resistivity, reducing grain size, and improving grain size uniformity, the measure of reducing grain resistivity is to reduce the residual voltage ratio of ZnO voltage-dependent resistor by reducing the residual voltage gradient, the measures of reducing donor density, increasing grain boundary surface state density, reducing grain size, and improving grain size uniformity are to reduce the residual voltage ratio of ZnO voltage-dependent resistor by increasing the reference voltage gradient. Its beneficial effects are: developing an excellent performance extra-high-voltage lightning arrester, shortening the length of lightning arrester and improving the potential distribution of lightning arrester, and high-voltage gradient ZnO valve.

Description

Technical Field

[0001] This invention relates to the field of power distribution equipment, and in particular to a low residual voltage, high current surge arrester for high-altitude power transmission and distribution lines. Background Technology

[0002] my country began independently developing ZnO surge arresters and valve plates in the 1970s, and in the 1980s, it imported production technology for ZnO surge arresters and valve plates from abroad, mainly from Japan. Through assimilation and absorption of the imported formulas and technologies, and through two Five-Year Plans of scientific and technological research, my country's manufacturing technology for ZnO surge arresters and valve plates has basically reached international standards. Currently, in China's power system, imported and domestically produced ZnO surge arresters account for almost half of the 500 kV voltage level ZnO surge arresters actually in operation; in addition, domestically produced 750 kV voltage level ZnO surge arresters have also been successfully developed and put into operation. This demonstrates that domestic ZnO surge arrester manufacturers have the foundation and capability to independently develop and produce ultra-high voltage surge arresters. Consequently, the State Grid Corporation of China has entrusted the research and production of ultra-high voltage surge arresters to leading domestic manufacturers such as Xi'an Electric Power and Fushun Ceramic.

[0003] The key to the development of ultra-high voltage (UHV) surge arresters is the development of high-performance ZnO varistors that can fully meet the overvoltage protection requirements of UHV systems. Drawing on the research approaches of Japanese UHV surge arrester varistors and novel high-voltage gradient varistors, domestic manufacturers have basically prepared two development schemes for UHV surge arrester varistors: - The first scheme adopts the basic formula and process of the existing 500 kV voltage level traditional ZnO valve plates, makes necessary improvements, and meets the application requirements of UHV surge arresters by connecting more and larger valve plates in series and parallel.

[0004] - The second scheme develops a new type of high-performance ZnO valve plate with a high voltage gradient to meet the application requirements of UHV surge arresters. This scheme can significantly improve the structural design and overall performance of UHV surge arresters compared to the first scheme.

[0005] The first design improves upon existing 500 kV voltage-level conventional ZnO varistors. However, compared to the actual application requirements of ultra-high voltage (UHV) surge arresters, the main performance issues with this design lie in its insufficient residual voltage ratio and current carrying capacity. It is understood that, based on imported Japanese formulas and technologies, and through independent research and development, the residual voltage ratio (under 8 / 20 µs, 20 kA nominal discharge current conditions, relative to the DC reference voltage) of ZnO varistors produced by domestic manufacturers has decreased from approximately 1.7 initially to approximately 1.6, but this still falls short of the 1.45 required for UHV surge arresters. For this first design, relevant manufacturers are making localized performance improvements based on formulas and processes used in long-term production and manufacturing, and can also draw upon publicly available information related to Japanese UHV surge arrester varistor development programs.

[0006] Compared to the first approach, the second approach, which focuses on developing a novel high-performance ZnO valve element with a high voltage gradient, represents a higher-level research objective. This approach aims to effectively reduce the size and weight of UHV surge arresters, improve their structural design, reduce manufacturing difficulty and costs, and enhance the overall potential distribution of the arrester, thereby increasing the reliability of both the arrester itself and the protected power system. This results in significant economic and social benefits. However, the second approach currently lacks sufficient publicly available data for reference, requiring domestic manufacturers to conduct entirely independent exploratory research, which undoubtedly presents greater challenges.

[0007] Besides relevant manufacturers, researchers from some domestic research institutions have also conducted research on new high-performance ZnO varistors. However, judging from the publicly available research results, most of them are small-sized samples studied in the laboratory, and they only focus on improving individual performance parameters of ZnO varistors, without comprehensively considering whether the overall performance parameters of ZnO varistors can meet the basic technical indicators required for the actual application of surge arresters.

[0008] The greatest challenge in developing novel high-performance ZnO varistors lies in balancing their overall performance parameters. Adjusting the ZnO varistor formulation and process can easily improve certain performance parameters, including the varistor voltage gradient, but inevitably leads to a significant decrease in one or more other performance parameters. This results in the varistor's overall performance failing to meet the basic technical requirements for practical applications of UHV surge arresters. For a novel high-performance ZnO varistor to ultimately meet the practical application needs of UHV surge arresters, every performance parameter must meet the basic technical requirements. Therefore, a suitable balance must be found between the varistor's raw material composition formulation and processing conditions. The key to developing high-performance, low-residual-voltage UHV surge arresters lies in improving the performance of the core component, the ZnO varistor varistor, reducing its residual voltage ratio, and improving its energy absorption capacity, among other overall performance indicators. The electrical performance of ZnO varistors is closely related to their microstructure parameters, including grain parameters, grain boundary parameters, and dimensional parameters. Based on simulation analysis, the effects of various parameters on the electrical performance of ZnO varistor, especially the residual voltage ratio, were studied. Among them, the residual voltage ratio K of the surge arrester corresponds to a current density of 63.7 A / cm2, which is equivalent to the current density flowing through the ZnO varistor varistor in a 1000 kV AC UHV system surge arrester (GIS type 10 cm varistor four columns in parallel) under a nominal impulse current of 20 kA. Summary of the Invention

[0009] The purpose of this invention is to solve the above-mentioned problems by designing a low residual voltage, high current surge arrester for high-altitude power transmission and distribution lines. The specific design scheme is as follows: An approach to achieving a high-performance, low-residual-voltage ultra-high-voltage surge arrester includes reducing donor density, increasing grain boundary surface state density, reducing grain resistivity, reducing grain size, and improving grain size uniformity. The measure to reduce grain resistivity is to reduce the residual voltage ratio of the ZnO varistor by reducing the residual voltage gradient. The measures to reduce donor density, increase grain boundary surface state density, reduce grain size, and improve grain size uniformity are all to reduce the residual voltage ratio of the ZnO varistor by increasing the reference voltage gradient.

[0010] Based on simulation analysis of the influence of ZnO varistor microstructure characteristics on macroscopic electrical performance parameters, measures that can significantly reduce the macroscopic residual voltage ratio of ZnO varistors include: reducing donor density, increasing grain boundary surface state density, reducing grain resistivity, reducing grain size, and improving grain size uniformity. Among these, reducing grain resistivity has the most significant effect on reducing the residual voltage ratio of ZnO varistors; reducing donor density, increasing surface state density, reducing grain size, and improving grain size uniformity have significant effects on reducing the residual voltage ratio of ZnO varistors. Analyzing the macroscopic influence mechanism of the residual voltage ratio, only the measure of reducing grain resistivity reduces the residual voltage ratio of ZnO varistors by decreasing the residual voltage gradient; the other methods all reduce the residual voltage ratio of ZnO varistors by increasing the reference voltage gradient.

[0011] Of all the measures mentioned above, reducing donor density and increasing surface state density can significantly reduce the macroscopic residual voltage ratio of ZnO varistors, but they also have corresponding adverse effects on other macroscopic electrical performance parameters. Only reducing grain resistivity mainly affects the residual voltage ratio without significantly affecting other macroscopic electrical performance parameters, and it can be effectively controlled by adding donor dopants. Therefore, reducing grain resistivity should be the basic approach for developing low residual voltage ZnO varistors.

[0012] In addition, reducing grain size and improving grain size uniformity also have a certain effect on reducing the residual voltage ratio of ZnO varistors, and reducing grain size can improve grain size uniformity at the same time.

[0013] Most importantly, the reduction in grain size, apart from leading to an increase in voltage gradient, does not significantly affect other performance characteristics of ZnO varistor, and a high voltage gradient is one of the high-performance characteristics of ZnO varistor; improving grain size uniformity can effectively improve the current carrying capacity and energy absorption capacity of ZnO varistor.

[0014] Therefore, reducing grain resistivity can be used as the main approach to studying low residual voltage ZnO varistors; when the grain resistivity decreases to a certain extent, reducing grain size and improving grain size uniformity can be used as auxiliary approaches to develop low residual voltage ZnO varistors and improve their overall performance.

[0015] The low residual voltage and high current surge arrester for high-altitude power transmission and distribution lines obtained by the above-mentioned technical solution of the present invention has the following advantages: Develop high-performance ultra-high voltage surge arresters, shorten the length of the surge arresters and improve the potential distribution of the surge arresters, and use ZnO varistors with high voltage gradients. Attached Figure Description

[0016] Figure 1The effect of grain resistivity on the electrical properties of ZnO varistors; Figure 2 This is a graph showing the effect of grain resistivity on JE characteristics; Figure 3 The influence of ZnO grain donor density on the electrical properties of ZnO varistors; Figure 4 The effect of ZnO grain donor density on JE properties; Figure 5 The effect of grain boundary surface state density on JE characteristics; Figure 6 The influence of grain boundary surface state density on the electrical properties of ZnO varistors; Figure 7 The effect of grain size on the electrical properties of ZnO varistors; Figure 8 The effect of grain size on JE properties; Figure 9 The effect of grain inhomogeneity on the electrical performance of ZnO varistors; Figure 10 This refers to the effect of grain inhomogeneity on JE properties. Detailed Implementation

[0017] The present invention will now be described in detail with reference to the accompanying drawings.

[0018] Example 1

[0019] The effect of ZnO grain resistivity ρ on the electrical performance of ZnO varistors is as follows: Figure 1 As shown, its JE characteristics are as follows Figure 2 As shown, grain resistivity has a very small effect on the voltage gradient, leakage current, and nonlinear coefficient of ZnO varistors, but a very significant effect on the residual voltage ratio.

[0020] As the grain resistivity decreases, the residual voltage ratio drops significantly, and the decrease is very pronounced. According to the JE curve, the grain resistivity only alters the electrical characteristics of the residual voltage gradient region, having almost no effect on the reference voltage gradient region. This indicates that the grain resistivity affects the residual voltage ratio by suppressing it through reducing the residual voltage gradient. Since reducing the grain resistivity can significantly decrease the residual voltage gradient, the grain resistivity of the sample should be minimized as much as possible to reduce the residual voltage ratio of the ZnO varistor.

[0021] Example 2

[0022] The effect of the donor density Nd in the ZnO varistor on its electrical performance is shown in Figure 3, and its JE characteristics are as follows: Figure 4As shown, with the increase of donor density, both the voltage gradient and the nonlinear coefficient decrease, while the leakage current continues to increase. The effect of donor density on the residual voltage ratio of the ZnO varistor is achieved by changing the reference voltage gradient. To reduce the residual voltage ratio of the ZnO varistor, the increase of donor density should be appropriately controlled.

[0023] Example 3

[0024] The effect of grain boundary surface state density (Ni) on the electrical performance of ZnO varistor is shown in Figure 6, and its JE characteristics are shown in Figure 5. The voltage gradient and nonlinear coefficient increase with increasing grain boundary surface state density, while the leakage current and residual voltage ratio decrease. The residual voltage ratio gradually decreases as the grain boundary surface state density increases. From the JE characteristic diagram, it can be seen that the effect of grain boundary surface state density on the residual voltage ratio of ZnO varistor is achieved by changing the reference voltage gradient. Therefore, to reduce the residual voltage ratio of ZnO varistor, the grain boundary surface state density should be increased as much as possible. Example 4

[0025] The effect of ZnO grain size d on the electrical properties of ZnO varistors is as follows: Figure 7 Its JE characteristics are as follows Figure 8 As shown, with the increase of grain size, the voltage gradient decreases significantly, the residual voltage ratio gradually increases, and the grain size has almost no effect on the nonlinear coefficient leakage current.

[0026] As the grain size decreases, the reference voltage gradient increases, while the grain size has little effect on the residual voltage gradient. Therefore, the decrease in the residual voltage ratio caused by grain size is due to the alteration of the reference voltage gradient of the ZnO varistor. Thus, to reduce the residual voltage ratio of the ZnO varistor, the ZnO grain size should be appropriately reduced.

[0027] Example 5

[0028] The effect of ZnO grain inhomogeneity σg on the performance of ZnO varistors is as follows: Figure 9 As shown, its JE characteristics are as follows Figure 10 As grain inhomogeneity increases, the voltage gradient and leakage current of the ZnO varistor decrease, while the nonlinear coefficient shows little change with increasing grain inhomogeneity. The effect of inhomogeneity on the residual voltage ratio is also achieved by influencing the reference voltage gradient.

[0029] The above technical solutions only embody the preferred technical solutions of the present invention. Any modifications that may be made by those skilled in the art to certain parts thereof embody the principles of the present invention and fall within the protection scope of the present invention.

Claims

1. A method for achieving a high-performance, low-residual-voltage ultra-high voltage surge arrester, comprising reducing donor density, increasing grain boundary surface state density, reducing grain resistivity, reducing grain size, and improving grain size uniformity, characterized in that, The measures to reduce grain resistivity are to reduce the residual voltage ratio of the ZnO varistor by reducing the residual voltage gradient. The measures to reduce donor density, increase grain boundary surface state density, reduce grain size, and improve grain size uniformity are all to reduce the residual voltage ratio of the ZnO varistor by increasing the reference voltage gradient.

2. The low residual voltage, high current surge arrester for high-altitude power transmission and distribution lines as described in claim 1, characterized in that, The measures to reduce grain resistivity are the basic approach for developing low residual voltage ZnO varistors.

3. The low residual voltage, high current surge arrester for high-altitude power transmission and distribution lines as described in claim 1, characterized in that, Reducing grain resistivity is the main approach to studying low residual voltage ZnO varistors.

4. The low residual voltage, high current surge arrester for high-altitude power transmission and distribution lines as described in claim 1, characterized in that, Reducing grain size and improving grain size uniformity are auxiliary ways to develop low residual voltage ZnO varistors and improve their overall performance.

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