Residual voltage optimization method for metal oxide arrester with series gap

Abstract

The invention discloses a residual voltage optimization method for a metal oxide arrester with a series gap, which relates to the technical field of lightning protection and comprises a working circuit, a metal oxide arrester and a closed gas gap device, and the metal oxidation lightning arrester is connected in series with the closed gas gap device and then is connected in parallel with the working circuit after being connected in series with the closed gas gap device. According to the invention, the residual voltage of the metal oxide lightning arrester connected in series with the closed series gap is improved by changing the air pressure and the spacing of the closed series gap, and the gas density and the electric field intensity are changed by cooperatively changing the pressure intensity of the closed gas and the spacing between the upper electrode and the lower electrode of the closed cavity on the premise of ensuring that the conduction voltage of the closed series gap is not changed. The conduction time delay can be shortened by proper adjustment, and the residual voltage of the lightning arrester connected in series with the gap is further influenced. According to the matching method provided by the invention, the residual voltage of the metal oxide lightning arrester connected in series with the sealed gas gap can be properly reduced under the condition that the work of an original circuit is not influenced, so that the protection effect is improved.

Description

Technical Field

[0001] The invention relates to the technical field of lightning protection, and more particularly to a residual voltage optimization method for a metal oxide lightning arrester with a series gap. Background Art

[0002] With the rapid development of science and technology and the continuous progress of society, the power system is facing higher and higher electricity requirements. This change has not only brought about a sharp increase in electricity demand, but also increased the risks in the operation of the power system, one of which is the overvoltage problem. Overvoltage phenomenon may cause equipment damage, system failure, and even cause safety hazards. Therefore, how to effectively prevent and manage overvoltage problems and ensure the safety and stability of the power system has become a key issue that needs to be urgently solved in the current power industry. One of the most common causes of overvoltage is lightning strikes. In areas with frequent rainfall and lightning, the probability of lightning disasters to equipment and factories has increased significantly. If the equipment is relatively expensive, for the safety of the equipment and subsequent work efficiency, it may often suspend work on rainy days for lightning protection. In this way, the work efficiency will be reduced to a corresponding extent, which will cause considerable losses in special circumstances. Therefore, lightning protection research has become an indispensable part.

[0003] The mainstream lightning protection methods are lightning rods and lightning arresters. However, lightning arresters have strict requirements on equipment height and protection area. For example, some communication devices may reach a height of nearly 200 meters, and occupy a large area. The cables in the middle cover a wide area, even hundreds of meters. If the lightning rod is to achieve the desired effect, it needs to be built hundreds of meters above the original signal tower. In terms of engineering, this cannot take into account both cost and practical application. Therefore, in this special case, the use of lightning arresters should be considered.

[0004] The maximum voltage across the metal oxide arrester when it is turned on due to overvoltage is called residual voltage. The residual voltage is the maximum overvoltage encountered by the original working circuit. Therefore, if the residual voltage is too large, it means that the current passing through the circuit is too large, which will cause the circuit to burn out. If the residual voltage of the arrester is set too low, the circuit may be turned on during normal operation, thereby affecting the normal operation of the original circuit.

[0005] Therefore, how to propose a residual pressure optimization method for a metal oxide lightning arrester with a series gap, using a closed air gap in series with the lightning arrester, and actively setting the residual pressure so that if the air gap is not conductive, the lightning arrester will not work because no current passes through it. If the air gap is conductive, the low conduction value set for the lightning arrester enables it to respond quickly is a problem that technical personnel in this field urgently need to solve. Summary of the invention

[0006] In view of this, the present invention provides a residual pressure optimization method for a metal oxide arrester with a series gap, which adopts a closed air gap in series with the arrester, and actively sets the residual pressure so that if the air gap is not conductive, the arrester will not work without current passing through, and if the air gap is conductive, the low conduction value set by the arrester enables it to respond quickly. In order to achieve the above purpose, the present invention adopts the following technical solutions: A method for optimizing residual voltage of a metal oxide arrester with a series gap comprises: a working circuit, a metal oxide arrester and a closed gas gap device; the metal oxide arrester is connected in series with the closed gas gap device, and the metal oxide arrester is connected in parallel with the working circuit after being connected in series with the closed gas gap device.

[0007] Optionally, the closed gas gap device includes: an upper plate metal sheet, an upper pole plate, a metal isolation block, an insulating support column, an air inlet, a spherical valve, gas, an air outlet, a sealed insulating wall, a lower pole plate and a lower plate metal sheet; the metal isolation block is fixedly connected to the upper pole plate, one end of the insulating support column is connected to the upper plate metal sheet, and the other end is connected to the lower plate metal sheet, and the bottom of the sealed insulating wall is sealed and connected to the lower plate metal sheet; the lower pole plate is sealed and connected to the inner wall of the bottom of the sealed insulating wall, and is fixedly connected to the lower plate metal sheet, the upper pole plate and the sealed insulating wall are slidably sealed and connected, the air inlet and the air outlet respectively penetrate the sealed insulating wall, and a closed cavity is formed by the sealed insulating wall, the upper pole plate and the lower pole plate, air is taken in through the air inlet, and exhaust is discharged through the air outlet; a spherical valve is provided at the air inlet for opening and closing the air inlet to control the entry of gas, and a spherical valve is provided on the air outlet for opening and closing the air outlet to control the discharge of gas.

[0008] Optionally, one end of the insulating support column is connected to the upper plate metal sheet, and the other end is connected to the lower plate metal sheet, wherein the upper plate metal sheet is circumferentially provided with bolt holes, the upper end of the insulating support column is provided with threads that cooperate with the bolt hole threads of the upper plate metal sheet, the lower plate metal sheet is circumferentially provided with through holes that are adapted to the bolt holes, and the lower end of the insulating support column is interference fit with the through holes.

[0009] Optionally, the shape of the inner wall of the sealing insulating wall is adapted to the shapes of the upper electrode plate and the lower electrode plate.

[0010] Optionally, the number of the bolt holes, the insulating support columns and the through holes are adapted, and the number is N.

[0011] Optionally, the setting heights of the air inlet and the air outlet are both lower than the maximum stroke of the upper plate, and the setting heights of the air inlet and the air outlet are both higher than the height of the lower plate.

[0012] Optionally, it also includes: based on the Paschen's law formula, calculating the residual voltage value and the conduction current according to the discharge delay, gas density and electric field strength.

[0013] Optionally, ATP-EMTP software circuit simulation is performed based on the calculation results, and simulation experiment verification is performed.

[0014] It can be seen from the above technical solution that, compared with the prior art, the present invention discloses a method for optimizing the residual voltage of a metal oxide arrester with a series gap, which has the following beneficial effects: The present invention proposes a residual pressure optimization method for a metal oxide arrester with a series gap, comprising: a working circuit, a metal oxide arrester and a closed gas gap device; the metal oxide arrester is connected in series with the closed gas gap device, and the metal oxide arrester is connected in series with the closed gas gap device and then connected in parallel with the working circuit. The present invention improves the residual pressure of the metal oxide arrester connected in series with it by changing the air pressure and spacing of the closed series gap. In the metal oxide arrester with a series gap, the residual pressure can be numerically regarded as the conduction voltage of the series gap plus the voltage value that rises during the conduction delay. Under the premise of ensuring that the conduction voltage of the closed series gap remains unchanged, the gas density and electric field strength are changed by changing the pressure of the closed gas and the spacing between the upper and lower electrodes of the closed cavity. The gas density and electric field strength are important factors for changing the conduction time. Appropriate adjustment can shorten the conduction delay and further affect the residual pressure of the arrester connected in series with the gap. The matching method provided by the present invention can appropriately reduce the residual pressure of the metal oxide arrester with a series closed gas gap without affecting the operation of the original circuit, thereby improving the protection effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0016] Figure 1 A structural schematic diagram of a residual voltage optimization method for a metal oxide arrester with a series gap provided by the present invention.

[0017] Figure 2 This is a diagram of the installation position and overall layout of the lightning protection device provided by the present invention.

[0018] Figure 3 This is a diagram of the minimum breakdown residual pressure results under standard atmospheric pressure and original spacing provided by the present invention.

[0019] Figure 4This is a graph of the minimum breakdown residual pressure results provided by the present invention at 10 times the atmospheric pressure and 1 / 10 spacing.

[0020] Figure 5 This is a schematic diagram of the insulating support column structure provided by the present invention.

[0021] Among them, 1-upper plate metal sheet, 2-upper pole plate, 3-metal isolation block, 4-insulating support column, 5-air inlet, 6-spherical valve, 7-gas, 8-air outlet, 9-sealed insulating wall, 10-lower pole plate, 11-lower plate metal sheet. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The embodiment of the present invention discloses a method for optimizing the residual voltage of a metal oxide arrester with a series gap, comprising: a working circuit, a metal oxide arrester and a closed gas gap device; the metal oxide arrester is connected in series with the closed gas gap device, and the metal oxide arrester is connected in parallel with the working circuit after being connected in series with the closed gas gap device.

[0024] The present invention discloses a residual pressure optimization method for a metal oxide arrester with a series gap, which improves the residual pressure of the metal oxide arrester connected in series by changing the air pressure and spacing of the closed series gap. The residual pressure in the metal oxide arrester with a series gap can be numerically regarded as the conduction voltage of the series gap plus the voltage value that rises during the conduction delay. Under the premise of ensuring that the conduction voltage of the closed series gap remains unchanged, the gas density and electric field strength are changed by changing the pressure of the closed gas and the spacing between the upper and lower electrodes of the closed cavity. The gas density and electric field strength are important factors for changing the conduction time. Appropriate adjustment can shorten the conduction delay and further affect the residual pressure of the arrester connected in series with the gap. The matching method provided by the present invention can appropriately reduce the residual pressure of the metal oxide arrester with a series closed gas gap without affecting the operation of the original circuit, thereby improving the protection effect.

[0025] Furthermore, the closed gas gap device includes: an upper plate metal sheet 1, an upper electrode plate 2, a metal isolation block 3, an insulating support column 4, an air inlet 5, a ball valve 6, a gas 7, an air outlet 8, a sealed insulating wall 9, a lower electrode plate 10 and a lower plate metal sheet 11; the metal isolation block 3 is fixedly connected to the upper electrode plate 2, one end of the insulating support column 4 is connected to the upper plate metal sheet 1, and the other end is connected to the lower plate metal sheet 11, and the bottom of the sealed insulating wall 9 is sealed and connected to the lower plate metal sheet 11; the lower electrode plate 10 is connected to the inner bottom of the sealed insulating wall 9 The upper electrode plate 2 is sealed and connected to the sealed insulating wall 9 and fixedly connected to the lower plate metal sheet 11; the upper electrode plate 2 is slidably sealed and connected to the sealed insulating wall 9; the air inlet 5 and the air outlet 8 respectively penetrate the sealed insulating wall 9; a closed cavity is formed by the sealed insulating wall 9, the upper electrode plate 2 and the lower electrode plate 10; air is taken in through the air inlet 5 and exhaust is taken out through the air outlet 8; a ball valve 6 is provided on the air inlet 5 for switching the air inlet 5 to control the entry of the gas 7; a ball valve is provided on the air outlet 8 for switching the air outlet 8 to control the discharge of the gas 7.

[0026] Furthermore, one end of the insulating support column 4 is connected to the upper plate metal sheet 1, and the other end is connected to the lower plate metal sheet 11, wherein the upper plate metal sheet 1 is circumferentially provided with bolt holes, and the upper end of the insulating support column 4 is provided with threads that match the bolt hole threads of the upper plate metal sheet 1, and the lower plate metal sheet 11 is circumferentially provided with through holes that are adapted to the bolt holes, and the lower end of the insulating support column 4 is interference fit with the through holes.

[0027] Furthermore, the inner wall shape of the sealing insulating wall 9 is adapted to the shapes of the upper electrode plate 2 and the lower electrode plate 10 .

[0028] Furthermore, the number of the bolt holes, the insulating support columns 4 and the through holes is adapted, and the number is N.

[0029] In a specific embodiment, Figure 5 As shown, the number of the bolt holes, the insulating support columns 4 and the through holes are all four.

[0030] Further, the setting heights of the air inlet 5 and the air outlet 8 are both lower than the maximum stroke of the upper plate 2, and the setting heights of the air inlet 5 and the air outlet 8 are both higher than the height of the lower plate 10. In a specific embodiment, the air inlet 5 is arranged above the air outlet 8, the setting height of the air inlet 5 is lower than the maximum stroke of the upper plate 2, and the setting height of the air outlet 8 is greater than the height of the lower plate 10.

[0031] Furthermore, it also includes: based on the Paschen's law formula, the residual voltage value and the conduction current are calculated according to the discharge delay, gas density and electric field strength.

[0032] Furthermore, ATP-EMTP software circuit simulation is performed based on the calculation results, and simulation experiments are carried out to verify the results.

[0033] In a specific implementation, the protective effect of reducing the residual voltage can be achieved by connecting a roughly air gap in series with the arrester, but by changing the parameters of the air gap, the residual voltage can be further reduced and the protective effect can be improved. Specifically, after the air gap is connected in series with the arrester, the residual voltage can be roughly equal to the conduction voltage of the air gap plus the voltage rise value during the conduction time. Therefore, without changing the conduction voltage, the conduction speed can be increased and the conduction time can be shortened to reduce the residual voltage value. The specific steps are as follows: The conduction time is mainly affected by several factors: conduction voltage, air pressure and distance between the plates. The conduction voltage is quite special. Reducing the conduction voltage can reduce the residual voltage, but such a rough reduction method lacks the ability to protect the circuit from surges. For example, if the peak working voltage is 80kv, it is obviously unreasonable to reduce the conduction voltage to 81kv. If there is a slight fluctuation, it may trigger the arrester and affect the working circuit. Therefore, another goal of shortening the conduction time is selected as air pressure and distance between the plates.

[0034] According to Paschen's law: ; Among them, P is the atmospheric pressure, d is the gas gap, A and B are empirical coefficients related to the gas properties, and γ is the surface ionization coefficient.

[0035] Increasing the gas pressure unilaterally will increase the conduction voltage, and reducing the distance between the plates unilaterally will reduce the conduction voltage. Both are not feasible, so the two must be changed in coordination to keep the product of the gas pressure and the distance between the plates fixed. For example, if the gas pressure increases to 3 times the original, the distance between the plates will be shortened to 1 / 3 of the original. The fixed value of the product is selected according to the conduction voltage required. In this way, the gas pressure conduction time can be changed by changing the density of the enclosed gas and the electric field strength through the change of the gas pressure and the distance between the plates, while ensuring that the conduction voltage remains unchanged.

[0036] In a specific implementation, a residual pressure optimization method for a metal oxide arrester with a series gap optimizes the residual pressure of a metal oxide arrester with a series gap by changing the air pressure and the distance between the plates, so that the lightning protection device can further improve the protection effect and protection accuracy under customized requirements, and provide protection for devices that require high protection, such as Figure 1As shown, the upper plate metal sheet 1 is used to connect the circuit; the upper electrode plate 2 is the conductive material of the upper electrode; the metal isolation block 3 is used to connect the upper electrode plate and the upper plate metal sheet; the insulating support column 4 plays a supporting role and uses insulating material to prevent conduction. The upper side is threaded and used to adjust the height of the upper electrode plate from the lower electrode plate. It is detachable. The height is first adjusted with the thread, and then the lower side is fixed on the lower plate metal sheet; the air inlet 5 is used to blow in gas to change the pressure. After conduction, the pressure and temperature of the sealed cavity will be affected due to gas ionization and other reasons. At the same time, the air inlet can also be added to replace the internal gas; the ball valve 6 is used to switch the air inlet and outlet. When the gas is not flowing, it can ensure that the cavity is sealed; the gas 7 is placed in the sealed cavity, and the main component can be air; the air outlet 8 is used to discharge the old gas; the sealed insulating wall 9 plays a supporting, sealing and insulating role; the lower plate 10 is the conductive material of the lower electrode; the lower plate metal sheet 11 is used to connect the circuit, and in this embodiment, the lightning arrester is connected.

[0037] In a specific implementation, the installation position and overall layout of the lightning protection device are as follows: Figure 2 As shown, the closed gas gap and the metal oxide arrester are connected in series between the antenna and the working circuit to ensure that when lightning strikes the antenna, the device can react quickly and conduct the current into the ground.

[0038] In a specific implementation, a residual pressure optimization method for a metal oxide arrester with a series gap is mainly achieved by changing the air pressure of the enclosed gas gap and the distance between the plates. In order to verify the method, MATLAB is used for calculation and analysis, and the formula of the final discharge time changing with the change of the air pressure and the distance between the plates is obtained by using the Paschen's law formula, the gas density formula, the electric field strength formula and the discharge delay empirical formula. The specific steps are as follows: (1) Lightning current is a double exponential function of 18400A 8 / 20µ s For reference, k=4, α=86600s -1 , β = 173200s -1 The temperature is set to 20 degrees Celsius, that is, T=293k, and the air gas constant is set to R=287.05. The air A value is 0.11 (1 / (Pa·cm)), the B value is 2.74 (V / (Pa·cm)), and γ is 0.025 when copper is used as the electrode material.

[0039] (2) The normal working rated voltage of the circuit is set to 110 kV, and the maximum statistical overvoltage of the system is 3 times the rated voltage, i.e., U G =330000V, so according to the metal oxide arrester specification for series gap, the breakdown voltage is assumed to be 402600kV.

[0040] (3) The calculation formula for discharge delay is: ; Where ρ is the gas density (g / cm 3 ); τ is the discharge delay (s); E is the average electric field strength of the gap (kv / cm).

[0041] (4) The formula for gas density is: ; Where P is pressure, M is molar mass, R is ideal gas constant, and T is temperature.

[0042] (5) If the confined space is regarded as a uniform electric field (plate to plate), the average electric field strength is: .

[0043] (6) Finally, the discharge delay under standard atmospheric pressure (approximately 103000Pa) is calculated to be 0.11021µ s , 0.03734µ at 3 times atmospheric pressure and 1 / 3 spacing s , 0.02162µ at 5 times atmospheric pressure and 1 / 5 times spacing s , 0.01081µ at 10 times atmospheric pressure and 1 / 10 times spacing s .

[0044] (7) The numerical calculation formula for residual pressure is: ; Among them, Z is the impedance of the branch when the arrester is in action, For a steady-state current, the steady-state current of a working circuit in an AC environment can be expressed by a sine function as follows: ; Among them, I G It is the maximum overcurrent of the system.

[0045] (8) On-current I s It can be expressed as follows: , where I L For lightning current.

[0046] In a specific implementation, circuit simulation is performed by simulation software, and simulation experiments are performed on the theoretical method to test whether the conclusion is correct. Figure 3 and Figure 4 As shown: The simulation shows that the time to reach the minimum breakdown voltage of 402600V is 0.00500287s. The discharge delay τ under standard atmospheric pressure / original spacing and 10 times atmospheric pressure and 1 / 10 times spacing is added to obtain the final total discharge time.

[0047] The gas switch of the arrester branch is set to close at 0.005002979s and 0.005002881s to simulate the fully conductive state of the two cases. The result obtained by reading the voltage meter of the arrester branch is that the residual pressure under standard atmospheric pressure and original spacing is 427613V; the residual pressure under 10 times atmospheric pressure and 1 / 10 times spacing is 404652V. The difference between the residual pressure under standard atmospheric pressure and 10 times atmospheric pressure reaches 22961V, which has an impact of 5.70% on the target residual pressure of 402600V, effectively reducing the residual pressure at both ends of the arrester.

[0048] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0049] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for optimizing residual voltage of a metal oxide arrester with a series gap, characterized in that: include: A working circuit, a metal oxide arrester and a closed gas gap device; the metal oxide arrester is connected in series with the closed gas gap device, and the metal oxide arrester is connected in series with the closed gas gap device and then connected in parallel with the working circuit; The sealed gas gap device comprises: an upper plate metal sheet (1), an upper electrode plate (2), a metal isolation block (3), an insulating support column (4), an air inlet (5), a spherical valve (6), gas (7), an air outlet (8), a sealed insulating wall (9), a lower electrode plate (10) and a lower plate metal sheet (11); the metal isolation block (3) is fixedly connected to the upper electrode plate (2); one end of the insulating support column (4) is connected to the upper plate metal sheet (1) and the other end is connected to the lower plate metal sheet (11); the bottom of the sealed insulating wall (9) is sealedly connected to the lower plate metal sheet (11); the lower electrode plate (10) and the inner bottom of the sealed insulating wall (9) are connected to each other; The upper plate (2) is sealed and connected to the sealing insulating wall (9) and is fixedly connected to the lower plate metal sheet (11); the upper plate (2) is slidably sealed and connected to the sealing insulating wall (9); the air inlet (5) and the air outlet (8) respectively penetrate the sealing insulating wall (9); a closed cavity is formed by the sealing insulating wall (9), the upper plate (2) and the lower plate (10); air is taken in through the air inlet (5) and exhausted through the air outlet (8); a ball valve (6) is provided on the air inlet (5) for opening and closing the air inlet (5) to control the entry of the gas (7); and a ball valve is provided on the air outlet (8) for opening and closing the air outlet (8) to control the discharge of the gas (7).

2. The method for optimizing residual voltage of a metal oxide surge arrester with a series gap according to claim 1, characterized in that: One end of the insulating support column (4) is connected to the upper plate metal sheet (1), and the other end is connected to the lower plate metal sheet (11), wherein the upper plate metal sheet (1) is provided with bolt holes in a circumferential direction, and the upper end of the insulating support column (4) is provided with threads that match the threads of the bolt holes of the upper plate metal sheet (1), and the lower plate metal sheet (11) is provided with through holes in a circumferential direction, and the through holes are adapted to the bolt holes, and the lower end of the insulating support column (4) is interference-fitted with the through holes.

3. The method for optimizing residual voltage of a metal oxide surge arrester with a series gap according to claim 1, characterized in that: The inner wall shape of the sealing insulating wall (9) is adapted to the shapes of the upper electrode plate (2) and the lower electrode plate (10).

4. The method for optimizing residual voltage of a metal oxide arrester with a series gap according to claim 2, characterized in that: The number of the bolt holes, the insulating support columns (4) and the through holes is adapted, and the number is N.

5. The method for optimizing residual voltage of a metal oxide arrester with a series gap according to claim 1, characterized in that: The air inlet (5) and the air outlet (8) are both arranged at a height lower than the maximum stroke of the upper electrode plate (2), and the air inlet (5) and the air outlet (8) are both arranged at a height higher than the height of the lower electrode plate (10).

6. The method for optimizing residual voltage of a metal oxide arrester with a series gap according to claim 1, characterized in that: Also includes: Based on the Paschen's law formula, the residual voltage value and conduction current are calculated according to the discharge delay, gas density and electric field strength.

7. A method for optimizing residual voltage of a metal oxide arrester with a series gap according to claim 6, characterized in that: According to the calculation results, ATP-EMTP software circuit simulation is carried out and simulation experiments are performed to verify it.

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