A liquid recoil arc extinguishing lightning protection device

Abstract

The invention discloses a liquid recoil arc extinguishing lightning protection device, which belongs to the field of arc extinguishing lightning protection technology, including a recoil tube, a conductor is arranged at the bottom of the recoil tube and connected to the ground, and liquid is arranged in the recoil tube. Liquid is placed in the recoil tube, and when the arc enters the recoil tube, the moment the arc pre-breaks through the liquid, the lightning arc impact time is extremely short, the liquid cannot be instantly deformed and displaced, the liquid-electric detonation effect, the recoil arc extinguishing pressure peak is synchronized with the impact steepness arc pre-breakdown time, after the arc conducts the liquid, the arc and the liquid perform heat exchange to generate an electro-liquid heat exchange effect, the liquid bubbles and thermal evaporation effect generated by the arc heat store kinetic energy, and the downward shock wave generated by the liquid-electric detonation effect and the electro-liquid heat exchange effect is reflected back by the bottom of the recoil tube to form a shock wave positive reflection effect to extinguish the arc. The invention cuts off the arc early, the recoil arc extinguishing pressure peak is synchronized with the impact steepness arc pre-breakdown time, and the impact arc is cut off immediately when it is just formed.

Description

Technical Field

[0001] The invention relates to the technical field of arc extinguishing and lightning protection, and in particular to a liquid recoil arc extinguishing and lightning protection device. Background Art

[0002] Lightning strikes can cause various forms of damage and destruction to power facilities. Thundercloud discharges can cause lightning overvoltage in power systems. Lightning overvoltage can damage insulators and transmission lines. When lightning strikes a transmission line, the impulse flashover causes line insulator flashover, which in turn generates a large power frequency follow-current, damaging insulator strings and hardware, leading to line accidents. When lightning strikes a transmission line or lightning arrester, it may cause strand breakage or even fracture, making it impossible to carry out power transmission work.

[0003] The gas recoil arc extinguishing device can effectively reduce the lightning current and make the volt-second characteristic of the active arc extinguishing parallel gap flatter. However, the existing gas recoil arc extinguishing device has a low recoil pressure and can only reduce the steepness of the lightning current wave head, but cannot further attenuate the lightning current amplitude. The lightning current attenuation rate is low, and the arc current interruption capacity is not large enough. In view of the above problems, a liquid recoil arc extinguishing lightning protection device is proposed. Summary of the invention

[0004] The purpose of the present invention is to provide a liquid recoil arc extinguishing lightning protection device to solve the technical problems mentioned in the background technology. The purpose is to improve the attenuation intensity of the lightning current and the ability to cut off the huge arc of the gas recoil arc extinguishing device during the recoil arc extinguishing process. It is to enhance the arc extinguishing pressure of the single recoil arc extinguishing device during the recoil arc extinguishing process, which can not only attenuate the amplitude of the lightning current, but also prolong the discharge time of the arc, so as to avoid the instantaneous lightning current amplitude being too large to cause damage to the transmission line.

[0005] A liquid recoil arc extinguishing lightning protection device comprises a recoil pipe, a conductor is arranged at the bottom of the recoil pipe and connected to the ground, and liquid is arranged in the recoil pipe.

[0006] Furthermore, the liquid is water or insulating liquid.

[0007] Furthermore, the recoil tube includes a ceramic tube body, a top cover plate, a fixing device, a bottom cover plate, an insulating covering layer and a skirt, the top cover plate is arranged on the top of the ceramic tube body, the bottom cover plate is arranged on the bottom of the ceramic tube body, the fixing device passes through the top cover plate and the bottom cover plate and is fixedly arranged, the insulating covering layer is arranged on the outside of the ceramic tube body, the skirt is arranged on the outside of the insulating covering layer, and the top cover plate is provided with a recoil nozzle.

[0008] Furthermore, the interior of the ceramic tube body is arranged as a hollow cylindrical structure, and the internal hollow hole of the ceramic tube body and the recoil spray hole are arranged on the same straight line.

[0009] Furthermore, the top cover plate includes a top cover plate cover and a top cover plate edge, the top cover plate cover is arranged as an upwardly concave structure, and the top cover plate edge is arranged on the bottom side of the top cover plate cover.

[0010] Furthermore, the bottom cover plate includes a bottom cover plate cover and a bottom cover plate edge, the bottom cover plate cover is arranged as a downwardly concave structure, and the bottom cover plate edge is arranged on the top side of the bottom cover plate cover.

[0011] Furthermore, the fixing device is configured as an insulating screw, and screw holes of the same number and size are provided on the edge of the top cover plate and the sleeve of the bottom cover plate, and the insulating screw passes through the screw holes and is tightened with a nut.

[0012] Furthermore, the top cover plate is sleeved on the top of the ceramic tube body, the bottom cover plate is sleeved on the bottom of the ceramic tube body, the top cover plate edge and the bottom cover plate are arranged as a circular structure, and the inner diameter is the same as the outer diameter of the ceramic tube body.

[0013] Furthermore, the insulating covering layer is configured as an epoxy resin layer, which covers the insulating screw, the nut, the edge of the top cover plate and the sleeve of the bottom cover plate, and encloses the ceramic tube body.

[0014] Furthermore, the top cover plate and the bottom cover plate are steel plates or zinc alloy plates.

[0015] Furthermore, a fixing pier is provided at the bottom of the bottom cover plate of the bottom cover plate, a recessed screw hole is provided at the bottom of the fixing pier, a screw rod is provided in the thread of the screw hole, and the fixing pier is made of conductive material and is integrally provided with the bottom cover plate.

[0016] The present invention adopts the above technical solution, and the present invention has the following technical effects:

[0017] The present invention cuts off the arc early, and the peak value of the recoil arc extinguishing pressure is synchronized with the pre-breakdown time of the impact high-steepness arc. The impact arc is cut off immediately when it is just formed. The pressure of cutting off the arc is huge, and the arc extinguishing pressure reaches 100 atmospheres. Such a large pressure peak time appears at the moment of impact pre-breakdown, and the pressure lasts for a long time. The liquid bubbles and thermal evaporation effect generated by the arc heat store a large amount of kinetic energy, which can release the arc extinguishing pressure for a long time, and the reignition of the impact arc is delayed. The long-lasting and huge recoil pressure destroys the continuous discharge conditions and the reignition conditions. After the impact arc is cut off, the reignition breakdown time is greatly delayed by more than ten to tens of microseconds, the steepness of the lightning current is significantly reduced by 90%, and the current amplitude is attenuated by more than 50%. The superposition and complementarity of various arc extinguishing mechanisms of liquid recoil - the arc extinguishing pressure under the liquid-electric effect generated by the sudden impact arc appears early and strong; the liquid vapor pressure generated by the thermal effect of the impact or power frequency arc strengthens the arc extinguishing pressure characteristic; the liquid vapor cools the arc temperature to extinguish the arc; the capillary perfusion and wave reflection improve the arc extinguishing pressure characteristic. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the principle structure of the present invention.

[0019] Figure 2 It is a cross-sectional view of the recoil tube structure of the present invention.

[0020] Figure 3 A top view of the recoil tube structure of the present invention without the skirt and epoxy installed.

[0021] Figure 4 It is a schematic diagram of the top cover plate structure of the recoil pipe structure of the present invention.

[0022] Figure 5 It is a schematic diagram of the bottom cover plate structure of the recoil pipe structure of the present invention.

[0023] Figure 6 This is the natural arc waveform diagram of the present invention.

[0024] Figure 7 This is the arc waveform when the liquid of the present invention is water.

[0025] Figure 8 This is the arc waveform when the liquid of the present invention is an insulating liquid.

[0026] Numbers in the figure: A-recoil tube; 1-ceramic tube body; 2-top cover plate; 2.1-top cover plate cover; 2.2-top cover plate edge; 2.3-top cover plate edge fixing hole; 3-nut; 4-fixing device; 5-bottom cover plate; 5.1-bottom cover plate cover; 5.2-bottom cover plate edge; 5.3-bottom cover plate edge fixing hole; 6-insulating covering layer; 7-skirt; 8-recoil nozzle; 9-fixing pier; 10-screw hole; 11-liquid; 12-screw. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention more clear, preferred embodiments are given to further describe the present invention in detail. However, it should be noted that many details listed in the specification are only for the purpose of enabling readers to have a thorough understanding of one or more aspects of the present invention, and these aspects of the present invention can be implemented even without these specific details.

[0028] A liquid recoil arc extinguishing lightning protection device, such as Figure 1 As shown, it includes a recoil pipe A, a conductor is arranged at the bottom of the recoil pipe A and connected to the ground, and liquid 11 is arranged in the recoil pipe A.

[0029] The specific liquid recoil arc extinguishing lightning protection process of the device is as follows: at the moment when the arc pre-breaks through the liquid 11, due to the extremely short impact time of the lightning arc, the liquid cannot be deformed and displaced instantaneously, and a liquid-electric explosion effect occurs. The recoil arc extinguishing pressure peak is synchronized with the impact steepness arc pre-breakdown time, and the impact arc is immediately cut off when it is just formed. After the arc conducts through the liquid, the arc and liquid exchange heat to produce an electro-liquid heat exchange effect. The liquid bubbles and thermal evaporation effect generated by the arc heat store kinetic energy and release the arc extinguishing pressure for a long time. The downward shock wave generated by the liquid-electric explosion effect and the electro-liquid heat exchange effect is reflected back by the bottom of the recoil tube A to form a shock wave positive reflection effect for arc extinguishing.

[0030] Liquid-electric detonation effect: Liquid is injected into a recoil tube cavity with only one arc inlet and the other end blocked by a grounding electrode. The arc is poured into the recoil tube from the cavity inlet and then enters the ground through the electrode at the other end of the cavity to form a discharge circuit. The arc in the cavity will discharge in the liquid, and the discharge arc temperature in the liquid will instantly reach 10 4 K or more, the arc will inevitably expand instantaneously due to the huge temperature gradient difference. 4 Temperatures above 0.1 K appear instantly, and the liquid wrapped around the arc has no time to move and evaporate due to heat. The liquid is in a "rigid" solid state and tightly wraps the arc, not allowing the arc to expand. At this time, the arc current value is extremely small but the arc voltage drop is very large. The energy accumulated in the arc is equal to the integral of the product of the arc voltage and the arc current. The temperature of the arc depends on the arc energy, and the peak value of the arc energy must appear at the moment the arc is connected, because as the arc current increases, the arc voltage drop will drop to near 0, the product of the current and the arc voltage drop is also close to 0, and the integrated energy also drops rapidly. Since the arc expansion pressure that the liquid bears depends on the arc temperature determined by the arc energy, the pressure will inevitably reach a peak value at the moment the arc is connected. The "rigid" wrapping of the arc by the liquid instantly converts the huge expansion force generated by the arc temperature into a pressure shock wave. The only release outlet of the shock wave can only be the arc entrance. At this time, the arc wrapped in the liquid in the entire cavity suddenly expands, an arc "detonation" effect occurs, and a peak pressure shock wave of more than 100Mpa is simultaneously generated and "ejected" from the only outlet in the cavity. At the same time as the pressure wave is released from the cavity outlet, the mechanical pressure wave "piston" quickly pushes the arc out of the cavity to cut off the arc in the cavity. At the same time, the inertia of the pressure wave "ejected" out of the cavity cuts off the arc outside the cavity, and the scale of arc cutting is very large.

[0031] When lightning strikes the recoil tube containing liquid, at the moment of high steepness pre-breakdown, the liquid cannot deform and displace instantaneously due to the extremely short impact time of the lightning arc. At this time, the liquid can be regarded as a shock wave transmission medium that will not be compressed itself. Under the "hammering" action of the arc, the liquid will simultaneously generate a pressure of about 100Mpa, and the impact arc in the recoil tube will be released through the recoil pressure and cut off, thus cutting off the arc building channel.

[0032] Electro-hydraulic heat exchange effect: The electro-hydraulic detonation effect generated at the moment the arc is connected will produce an arc detonation effect that generates a pressure peak at the moment the arc is connected. As the arc develops, the arc ionization degree increases, the arc current increases, the arc voltage drop drops to almost zero, the arc energy also decreases, and the pressure generated by the electro-hydraulic detonation effect also decreases. However, heat exchange between the arc and the liquid will occur. The arc generates a large amount of steam by vaporizing the liquid, taking away a large amount of arc heat, attenuating the arc ionization degree and weakening the arc strength. At the same time, the water vapor will generate expansion pressure to compensate for the pressure decay of the electro-hydraulic detonation. The heat exchange pressure can be maintained for a longer time, which is very beneficial for arc reignition suppression and arc interruption again. Experiments have shown that heat exchange pressure can delay arc reignition by more than 10μs. Since the impulse reignition current starts again from 0, the increase in impulse current amplitude is greatly attenuated, and the attenuation of lightning current amplitude is more than 60%. The ohmic voltage drop caused by lightning current on the ground grid resistance can be linearly reduced. The huge pressure generated by the impulse arc also produces a rapid and huge "interruption" effect on the power frequency arc building process at the starting point of arc building, effectively avoiding the occurrence of lightning tripping.

[0033] Positive reflection effect of shock wave: When the various shock waves generated by the electric arc are transmitted to the blocked bottom obstacles in the chamber, positive reflection shock waves will be generated. The pressure of the reflected wave will increase several times. The reflected wave is equivalent to amplifying the pressure of the electro-hydraulic explosion wave and the heat exchange expansion wave several times, which is very beneficial to the increase in pressure and the improvement of arc extinguishing ability.

[0034] The liquid-electric detonation effect and the liquid-electric heat exchange effect jointly inhibit the reignition of the arc: when the arc plasma enters the recoil tube, the physical shape changes from a thick arc to an extremely thin arc, and the radial pressure turns into an axial pressure. At the same time, due to the restriction of the recoil tube wall, the speed and temperature of the arc increase after entering the recoil tube, resulting in an increase in the pressure inside the tube, and finally a compression explosion effect, which causes the arc to be subjected to the recoil force. At the same time, the liquid-electric effect generated by the arc in the liquid further enhances the pressure inside the recoil tube. The persistent and huge recoil pressure destroys the continuous discharge conditions and the reignition conditions. After the impact arc is cut off, the reignition breakdown time is greatly delayed by more than ten to tens of microseconds, the steepness of the lightning current is significantly reduced by 90%, and the current amplitude is attenuated by more than 60%. Among them, the electro-hydraulic detonation effect generates a pressure peak synchronously with the arc connection time, cuts off the arc at the very weak starting point of the arc, and has the advantage of asymmetric arc extinguishing; the electro-hydraulic heat exchange effect will produce a persistent expansion pressure after the pressure peak to maintain the arc cut-off state, delay the arc reignition time and attenuate the arc current amplitude.

[0035] Effective protection against direct lightning overvoltage: When the pilot channel of lightning discharge hits the conductor, pole tower or other buildings of the transmission line, a large amount of lightning current passes through the struck object, generating an ohmic voltage drop on the impedance grounding resistance of the struck object, causing a very high potential at the struck point, forming a counter-attack overvoltage. The liquid recoil arc extinguishing method can attenuate the amplitude of the lightning current by more than 60%, and attenuate the ohmic voltage drop of the ground grid resistance by more than 60% by reducing the lightning current intensity, thereby avoiding insulation flashover caused by counter-attack overvoltage, effectively reducing the lightning trip rate and improving the lightning resistance level. Reducing the ohmic voltage drop of the ground grid by reducing the amplitude of the lightning current is more effective, controllable and economical than the traditional method of reducing the ohmic voltage drop of the ground grid by reducing the ground grid resistance.

[0036] Avoid damage caused by induced overvoltage: When lightning strikes near a line, it will induce overvoltage on the three-phase conductors of the overhead line. Since the main discharge has a development process, the induced charge on the conductor is not released instantly, but gradually. The horizontal distance between the lightning strike point and the bottom of the conductor is S, m, the lightning current amplitude is I, kA, and the average hanging height of the conductor is hd, m. According to the power industry standard DL / T620-1997, the lightning induced overvoltage Ug is:

[0037]

[0038] The liquid recoil arc extinguishing method releases the impact arc in the recoil tube through the recoil pressure and cuts it off, reducing the amplitude of the lightning current, and thus reducing the lightning induced overvoltage. It avoids the flashover caused by the induced overvoltage on the distribution network insulation, and reduces the lightning trip rate, accident rate and line break rate.

[0039] Avoid electromagnetic induction overvoltage from damaging equipment: During lightning discharge, a transient strong electromagnetic field pulse is generated in the space around the discharge channel. The protected objects in the space-changing electromagnetic field, whether conductors or non-conductors, will cut through the magnetic lines of force, causing them to generate higher electromagnetic induction electromotive force and cause harm. Affected by electrostatic induction, it interferes with signal lines, antennas and other radio communications, and even damages instruments and equipment. The liquid recoil arc extinguishing method releases shock waves through the liquid-electric effect to cut off the arc, which not only delays the arc discharge time, but also reduces the steepness of the lightning wave. Avoid the harm of induced electromagnetic overvoltage to power electronic components, communication signals, etc.

[0040] Avoid the hazards of step voltage: When a ground fault occurs in a transmission line or electrical equipment, there is a potential distribution around the ground current entry point. When a person walks into the current range, a potential difference is generated due to the different voltages between the left and right legs, forming a step voltage, which is harmful to personal safety. The liquid recoil arc extinguishing method reduces the magnitude of the ground current, which also reduces the potential difference of the ground near the ground point as the center, preventing the hazards caused by step voltage.

[0041] The arc is affected by the compression of the tube wall and the hydroelectric effect in the recoil tube, and a part of the energy is discharged from the upper port of the recoil tube in the form of recoil, which reduces the amplitude of the lightning current, reduces the steepness of the lightning wave, and prolongs the discharge time of the arc. The remaining arc energy enters the ground through the conductive channel of "conductor electrode-screw-ground".

[0042] In the embodiment of the present invention, the liquid 11 is water or an insulating liquid. When the liquid 11 is water, the effect is not so good, and the recoil waveform is as follows: Figure 7 As shown, when the liquid 11 is an insulating liquid such as oil, the waveform after recoil is as follows Figure 8 As shown. Figure 6 It is a natural arc waveform. Figure 7 For Figure 8 Under the same conditions, the discharge in water has a delayed and attenuated waveform, but the effect is not as good as that in oil. Figure 8 This is the waveform after the insulating oil and the arc are coupled (discharge in oil). The current waveform has completely disappeared, indicating that the arc intensity has been reduced to an extremely low level that cannot be measured, but the charge has been completely released.

[0043] like Figure 2As shown, the recoil tube A includes a ceramic tube body 1, a top cover plate 2, a fixing device 4, a bottom cover plate 5, an insulating cover layer 6 and a skirt 7. The top cover plate 2 is arranged on the top of the ceramic tube body 1, the bottom cover plate 5 is arranged on the bottom of the ceramic tube body 1, the fixing device 4 passes through the top cover plate 2 and the bottom cover plate 5 and is fixedly arranged, the insulating cover layer 6 is arranged on the outside of the ceramic tube body 1, the skirt 7 is arranged on the outside of the insulating cover layer 6, and the top cover plate 2 is provided with a recoil nozzle 8. The interior of the ceramic tube body 1 is arranged as a hollow cylindrical structure, and the internal hollow hole of the ceramic tube body 1 and the recoil nozzle 8 are arranged on the same straight line.

[0044] The fixing device 4 is configured as an insulating screw, and the top cover plate edge 2.2 and the bottom cover plate sleeve cover 5.1 are both provided with screw holes of the same number and size, and the insulating screw passes through the screw holes and is provided with nuts 3 to be tightened. The top cover plate sleeve cover 2.1 is sleeved on the top of the ceramic tube body 1, and the bottom cover plate sleeve cover 5.1 is sleeved on the bottom of the ceramic tube body 1. The top cover plate edge 2.2 and the bottom cover plate sleeve cover 5.1 are configured as circular structures, and the inner diameter is the same as the outer diameter of the ceramic tube body 1. The insulating covering layer 6 is configured as an epoxy resin layer, which covers the insulating screw, the nut 3, the top cover plate edge 2.2 and the bottom cover plate sleeve cover 5.1, and encloses the ceramic tube body 1. The top sleeve cover plate 2 and the bottom sleeve cover plate 5 are steel plates or zinc alloy plates.

[0045] First, a circular steel plate with a groove is tightly bonded to the upper and lower ends of the recoil tube with epoxy resin. The center of the steel plate at the upper end of the recoil tube has an opening, which is the same size as the aperture of the recoil tube. There are also 4 circular holes on the steel plate for installing insulating bolts, evenly distributed on the periphery of the steel plate. 8 nuts are used at the upper and lower ends of the 4 insulating screws to fix the position of the recoil tube. In order to avoid lightning strikes due to the close distance between the steel plates, the insulating screws, ceramic tubes and nuts are fully encapsulated with epoxy resin. The umbrella skirt is located at the outermost edge of the epoxy resin cylinder after encapsulation.

[0046] like Figure 4 As shown, the top cover plate 2 includes a top cover plate cover 2.1 and a top cover plate edge 2.2. The top cover plate cover 2.1 is set to an upward concave structure, and the top cover plate edge 2.2 is set on the bottom side of the top cover plate cover 2.1. The top cover plate 2 is mainly used to fix the upper end of the ceramic tube body 1. Then, when the top of the top cover plate cover 2.1 is exposed, it can be directly used as an arc-starting electrode to achieve the functions of fixation and arc-starting electrode, and realize dual functions. At the same time, the practical life of this arc-starting electrode will be very good, it has fixity, and the thickness is thick enough. After the arc is burned many times, it can still work normally after being worn.

[0047] like Figure 5As shown, the bottom cover plate 5 includes a bottom cover plate cover 5.1 and a bottom cover plate edge 5.2. The bottom cover plate cover 5.1 is set as a downwardly concave structure, and the bottom cover plate edge 5.2 is set on the top side of the bottom cover plate cover 5.1. The bottom cover plate 5 is mainly used to cover and fix the bottom of the ceramic tube body 1, wrap the bottom, and prevent it from breaking. At the same time, the bottom cover plate cover 5.1 is used as a lightning pole to transmit the remaining recoil energy backward, solving the technical problems that the original lightning pole is difficult to fix and has a short service life.

[0048] like Figure 1 As shown, the bottom of the bottom cover plate 5 is provided with a fixing pier 9, and the bottom of the fixing pier 9 is provided with an inwardly sunken screw hole. The fixing pier 9 is made of conductive material and is integrally provided with the bottom cover plate 5.1. The fixing pier 9 is mainly used to fix the entire recoil device on the external structure to achieve rapid fixation.

[0049] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A liquid recoil arc extinguishing lightning protection device, characterized in that: It comprises a recoil pipe (A), a conductor is arranged at the bottom of the recoil pipe (A) and connected to the ground, and liquid (11) is arranged in the recoil pipe (A); The liquid (11) is an insulating liquid; The recoil tube (A) comprises a ceramic tube body (1), a top cover plate (2), a fixing device (4), a bottom cover plate (5), an insulating covering layer (6) and a skirt (7), wherein the top cover plate (2) is arranged on the top of the ceramic tube body (1), the bottom cover plate (5) is arranged on the bottom of the ceramic tube body (1), the fixing device (4) passes through the top cover plate (2) and the bottom cover plate (5) and is fixedly arranged, the insulating covering layer (6) is arranged on the outside of the ceramic tube body (1), the skirt (7) is arranged on the outside of the insulating covering layer (6), and a recoil nozzle (8) is arranged on the top cover plate (2); The interior of the ceramic tube body (1) is arranged as a hollow cylindrical structure, and the internal hollow hole of the ceramic tube body (1) and the recoil spray hole (8) are arranged on the same straight line; The top cover plate (2) comprises a top cover plate cover (2.1) and a top cover plate edge (2.2); the top cover plate cover (2.1) is arranged as an upwardly concave structure, and the top cover plate edge (2.2) is arranged on the bottom side of the top cover plate cover (2.1); The bottom cover plate (5) comprises a bottom cover plate cover (5.1) and a bottom cover plate edge (5.2); the bottom cover plate cover (5.1) is arranged as a downwardly concave structure, and the bottom cover plate edge (5.2) is arranged on the top side of the bottom cover plate cover (5.1); The fixing device (4) is set as an insulating screw, and the top cover plate edge (2.2) and the bottom cover plate sleeve (5.1) are both provided with screw holes of the same number and size, and the insulating screw passes through the screw holes and is provided with nuts (3) to be tightened; The top cover plate cover (2.1) is sleeved on the top of the ceramic tube body (1), the bottom cover plate cover (5.1) is sleeved on the bottom of the ceramic tube body (1), the top cover plate edge (2.2) and the bottom cover plate cover (5.1) are arranged in a circular structure, and the inner diameter is the same as the outer diameter of the ceramic tube body (1); The insulating covering layer (6) is configured as an epoxy resin layer, covering the insulating screw, the nut (3), the edge of the top cover plate (2.2) and the bottom cover plate cover (5.1), and enclosing the ceramic tube body (1); the top cover plate (2) and the bottom cover plate (5) are steel plates or zinc alloy plates; A fixing pier (9) is arranged at the bottom of the bottom cover plate cover (5.1) of the bottom cover plate (5), and an inwardly recessed screw hole is arranged at the bottom of the fixing pier (9). The fixing pier (9) is made of a conductive material and is integrally arranged with the bottom cover plate cover (5.1).

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