Grounding transformer for detecting faults of wind power generation and power supply system
By introducing heat-conducting plates, staggered heat dissipation fins, and limiting components into the grounding transformer, the heat dissipation and stability issues of the grounding transformer are solved, ensuring the normal fault detection and protection functions of the wind power generation system.
Patent Information
- Application Number
- CN202510778517.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-11
- Publication Date
- 2025-10-17
AI Technical Summary
Existing grounding transformers used in wind power supply systems lack effective heat dissipation and robust grounding rod designs, leading to temperature buildup and loose contact, which affects the effective performance of protection functions.
A grounding transformer was designed, which uses a heat-conducting plate and an interlaced heat dissipation fin structure for heat dissipation, and improves the stability of the grounding rod through a limiting component and a clamping plate structure. The transformer includes a combination of components such as a heat-conducting block, a heat-conducting plate, first and second heat dissipation fins, a limiting component, and a clamping plate.
This achieves effective heat dissipation of the grounding transformer, ensuring that the internal temperature does not exceed the limit, and improves the tightness and reliability of the contact between the grounding rod and the ground, thereby enhancing the protection function and safety guarantee of the wind power generation system.
Smart Images
Figure CN120809446A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of grounding transformers, in particular to a grounding transformer for detecting faults of a wind power supply system. BACKGROUND
[0002] With the increasing demand for clean energy worldwide, wind power generation as a renewable energy generation method has been widely used. The wind power supply system mainly consists of wind turbine generators, transformers, transmission lines and power electronic devices. Among them, the grounding transformer plays a crucial role in the process of power transmission and distribution, which raises the low-voltage power generated by the wind turbine to a voltage level suitable for power transmission, and then transmits it to the power grid through the transmission line.
[0003] In the power system, overvoltage may occur due to various reasons (such as lightning, switch operation, etc.). The grounding transformer can limit the overvoltage within a certain range through its own grounding structure and parameter design, protecting electrical equipment from overvoltage damage; at the same time, in the power system without direct grounding at the neutral point, when a single-phase grounding fault occurs, the grounding transformer can provide a return path for the fault current, so that the protection device can accurately detect the fault and act.
[0004] However, most of the grounding transformers for detecting faults of the wind power supply system do not have good heat dissipation function, resulting in high internal temperature accumulation, which can cause overall failure and affect the normal fault detection work of the entire wind power supply system; at the same time, the inserted grounding rod does not have good stability function, resulting in insufficient close and reliable contact between the grounding rod and the ground. This poor contact effect can directly affect the protection function of the grounding transformer, greatly reducing its protection effect on the entire system, and cannot provide sufficient and effective safety protection for the wind power supply system. SUMMARY
[0005] Therefore, the present application provides a grounding transformer for detecting faults of a wind power supply system to solve the problem that the existing grounding transformer does not have good heat dissipation function and does not have good stability function for the inserted grounding rod.
[0006] In order to achieve the above purpose, the present application provides the following technical scheme:
[0007] A grounding transformer for detecting faults of a wind power supply system, comprising a grounding transformer box, a heat conducting plate and a flow guide iron plate, a transmission assembly is arranged at the lower side of the rear end of the grounding transformer box, a grounding box is connected to the outer side of the lower end of the transmission assembly, a limiting assembly is arranged inside the grounding box below the transmission assembly, and the limiting assembly is connected with a grounding rod.
[0008] The upper end rear side of the grounding transformer box is fixedly installed with a heat conduction plate, and heat conduction blocks are installed at equal intervals on the front end outer side of the heat conduction plate. The rear end upper side of the heat conduction plate is provided with first heat dissipation fins, and the rear side edge of the heat conduction plate is fixedly connected with second heat dissipation fins.
[0009] The rear middle part of the grounding transformer box is fixedly installed with a flow guide iron plate, the rear end inner side of the flow guide iron plate is installed with a grounding rod, and the lower end of the grounding rod penetrates and inserts into the lower end inner side of the grounding transformer box.
[0010] Further, the lower end left and right sides of the grounding transformer box are fixedly installed with mounting bases, and the inner side of the grounding transformer box is provided with a grounding transformer main body. The upper end outer side of the grounding transformer box is provided with a coil assembly.
[0011] Further, the lower end middle part of the grounding transformer box is installed with an insulating tube, and the lower end of the insulating tube is in communication with the grounding rod. The grounding rod penetrates the inner sides of the insulating tube and the grounding box. The middle part of the grounding rod is in the shape of an "X" in cross section. The upper end middle part of the grounding rod is provided with a fixing screw for installing a wire.
[0012] Further, the grounding transformer main body is located directly in front of the heat conduction block. The diameter of the front end of the heat conduction block is larger than the diameter of the rear end.
[0013] Further, the length of the first heat dissipation fin is greater than the length of the second heat dissipation fin, and the first heat dissipation fin and the second heat dissipation fin are arranged in an up-and-down staggered manner.
[0014] Further, the rear end inner side of the grounding transformer box is installed with an access door located at the rear side of the flow guide iron plate through a hinge. The second heat dissipation fin is located on both sides of the access door. The inner side of the access door is fixedly installed with an adjusting block.
[0015] Further, the transmission assembly includes a pressing plate, a connecting abutting rod, and a return spring. The pressing plate is installed in the lower end inner side of the grounding transformer box. The lower end outer side of the pressing plate is fixedly installed with the connecting abutting rod. The upper end outer side of the connecting abutting rod is installed with the return spring located in the grounding transformer box.
[0016] Further, the pressing plate and the connecting abutting rod are connected to the grounding transformer box in a sliding manner. The lower end of the connecting abutting rod extends to the inner side of the grounding box. The connection between the pressing plate and the adjusting block is provided with a matching inclined surface structure.
[0017] Further, the limiting assembly comprises a connecting plate, a clamping plate, a torsion spring shaft and an insulating sheet, the connecting plate is installed in the inside of the grounding box, and the connecting plate is in contact with the lower end of the connecting rod, and the clamping plate is fixedly installed on the outer side of one end of the connecting plate close to the grounding rod.
[0018] Further, the clamping plate is provided with a torsion spring shaft inside one end close to the connecting plate, and the torsion spring shaft constitutes a rotating structure in the grounding box through a bearing, and the outer side of the torsion spring shaft is provided with an insulating sheet.
[0019] Compared with the prior art, the present application has the following advantages:
[0020] 1. The length of the first heat dissipation fin is larger than that of the second heat dissipation fin, and the first heat dissipation fin and the second heat dissipation fin are arranged in an up-down staggered manner, so that the heat dissipation block can absorb the heat generated by the grounding transformer main body and conduct it to the heat dissipation plate, and the heat dissipation plate can transfer the heat to the first heat dissipation fin and the second heat dissipation fin, thereby facilitating the dissipation of heat in the grounding transformer box through the first heat dissipation fin and the second heat dissipation fin, and the arrangement of the first heat dissipation fin and the second heat dissipation fin can enhance air flow, which helps to more effectively transfer heat from the transformer to the air, so that the whole has better heat dissipation function, and the internal temperature will not be too high, avoiding the influence of high temperature on the normal fault detection work of the whole wind power supply system.
[0021] 2. The torsion spring shaft is provided inside one end of the clamping plate close to the connecting plate, and the torsion spring shaft constitutes a rotating structure in the grounding box through a bearing, and the connecting plate and the torsion spring shaft have a good adjusting effect on the clamping plate, so that the connecting plate can be driven by the torsion spring shaft to rotate synchronously with the clamping plate under the extrusion of the connecting rod, so that the torsion spring shaft and the insulating sheet can be tightly connected with the grounding rod, thereby improving the stability of the grounding rod and improving the tightness and reliability of the contact between the grounding rod and the ground.
[0022] 3. The pressing plate and the connecting rod are connected to the grounding transformer box in a sliding manner, and the lower end of the connecting rod extends into the inside of the grounding box, and the connecting part between the pressing plate and the adjusting block is provided with a matching inclined surface structure, so that the adjusting block, the pressing plate and the connecting rod can be moved correspondingly by driving the adjusting block, the pressing plate and the connecting rod through the opening and closing of the maintenance door, thereby facilitating the subsequent change of the state of the connecting plate and the clamping plate, and having a good auxiliary transmission effect, thereby improving the convenience of use. BRIEF DESCRIPTION OF DRAWINGS
[0023] In order to more intuitively illustrate the prior art and the present application, exemplary drawings are given below. It should be understood that the specific shapes, configurations shown in the drawings should not be considered as limiting conditions in the implementation of the present application; for example, based on the technical concepts disclosed in the present application and the exemplary drawings, those skilled in the art can easily make routine adjustments or further optimizations to the increase / decrease / assignment of certain units, specific shapes, positional relationships, connection methods, size ratio relationships, etc.
[0024] Figure 1 A front view cross-sectional view of a grounding transformer for detecting faults of a wind power supply system according to some embodiments of the present application.
[0025] Figure 2 A side view cross-sectional view of a grounding transformer for detecting faults of a wind power supply system according to some embodiments of the present application.
[0026] Figure 3 A top view cross-sectional view of a heat-conducting plate and a heat-conducting block connection of a grounding transformer for detecting faults of a wind power supply system according to some embodiments of the present application.
[0027] Figure 4 A front view cross-sectional view of a grounding box and a grounding rod connection of a grounding transformer for detecting faults of a wind power supply system according to some embodiments of the present application.
[0028] Figure 5 A top view of a maintenance door in an open state of a grounding transformer for detecting faults of a wind power supply system according to some embodiments of the present application.
[0029] Figure 6 A top view cross-sectional view of a grounding rod and an insulating sheet connection of a grounding transformer for detecting faults of a wind power supply system according to some embodiments of the present application.
[0030] Legend of reference signs:
[0031] 1, grounding transformer box; 2, mounting base; 3, grounding transformer main body; 4, coil assembly; 5, heat-conducting plate; 6, heat-conducting block; 7, first heat dissipation fin; 8, second heat dissipation fin; 9, maintenance door; 10, insulating tube; 11, grounding box; 12, grounding rod; 13, fixing screw; 14, flow guide iron plate; 15, adjusting block; 16, pressing plate; 17, connecting resistance rod; 18, connecting plate; 19, clamping plate; 20, torsion spring shaft; 21, insulating sheet; 22, return spring. DETAILED DESCRIPTION
[0032] The present application will be further described in detail below with reference to the accompanying drawings.
[0033] AsFigures 1 to 6 As shown, a grounding transformer for detecting faults in a wind power generation power supply system in an embodiment of the present invention includes: a grounding transformer for detecting faults in a wind power generation power supply system, including a grounding transformer box 1, a heat conducting plate 5 and a guide iron plate 14, a mounting base 2 is fixedly installed on the left and right sides of the lower end of the grounding transformer box 1, and a grounding transformer main body 3 is arranged inside the grounding transformer box 1, and a coil assembly 4 is arranged on the outer side of the upper end of the grounding transformer box 1.
[0034] The grounding transformer body 1, mounting base 2, grounding transformer main body 3, and coil assembly 4 together constitute the grounding transformer body, which can be conveniently fixed to a mounting rail compatible with the mounting base 2 using the mounting base 2 and screws. The grounding transformer main body 3 is the main working component of the grounding transformer and includes multiple layers of stacked silicon steel sheets, multiple sets of primary coils, and multiple sets of secondary coils. The number of turns of the secondary coils is greater than the number of turns of the primary coils. The silicon steel sheets, primary coils, and secondary coils are isolated by insulating material. The multiple sets of primary coils and secondary coils are then connected by multiple wires. During actual operation, the input electrical energy is delivered to the corresponding coils through the multiple coil assemblies 4 and then transmitted to the corresponding transmission line to the substation.
[0035] A heat conducting plate 5 is fixedly mounted on the rear side of the upper end of the grounding transformer box 1, and heat conducting blocks 6 are installed at equal intervals on the outer side of the front end of the heat conducting plate 5. A first heat dissipating fin 7 is provided on the upper side of the rear end of the heat conducting plate 5, and a second heat dissipating fin 8 is fixedly connected to the rear side of the heat conducting plate 5.
[0036] Among them, the grounding transformer main body 3 is located in front of the heat-conducting block 6, and the front end diameter of the heat-conducting block 6 is larger than the rear end diameter, which is convenient for passing through the front end of the heat-conducting block 6, increasing the heat conduction area of the heat-conducting block 6, and the heat-conducting block 6 is installed at equal intervals on the outer side of the rear end of the grounding transformer main body 3 under the action of the heat-conducting plate 5. At this time, the heat-conducting block 6 can absorb the heat generated by the operation of the grounding transformer main body 3 and conduct it to the heat-conducting plate 5, making it convenient for the heat-conducting plate 5 to transfer the heat to the first heat dissipation fins 7 and the second heat dissipation fins 8, thereby facilitating the heat dissipation of the heat inside the grounding transformer box 1 through the first heat dissipation fins 7 and the second heat dissipation fins 8. The second heat dissipation fins 8 are located on both sides of the inspection door 9 to avoid affecting the opening and closing of the inspection door 9, and a door lock assembly is provided at the connection between the inspection door 9 and the front end of the grounding transformer box 1 to facilitate locking the inspection door 9;
[0037] Meanwhile, the length of the first heat dissipation fin 7 is greater than that of the second heat dissipation fin 8, and the first heat dissipation fin 7 and the second heat dissipation fin 8 are arranged in an up-down staggered manner, facilitating air flow through the first heat dissipation fin 7 and the second heat dissipation fin 8, helping to more effectively transfer heat from the transformer to the air, so that the whole has better heat dissipation function, and the internal temperature will not be too high, avoiding the influence of high temperature on the normal fault detection of the whole wind power supply system.
[0038] The middle part of the rear side of the grounding transformer box 1 is fixedly provided with a flow guide iron plate 14, the rear end of the flow guide iron plate 14 is internally provided with a grounding rod 12, the lower end of the grounding rod 12 penetrates into the lower end of the grounding transformer box 1, the middle part of the lower end of the grounding transformer box 1 is provided with an insulating tube 10, and the lower end of the insulating tube 10 is in communication with the grounding rod 12, the grounding rod 12 penetrates into the insulating tube 10 and the grounding box 11, and the upper end of the grounding rod 12 is provided with a fixing screw 13 for installing a wire.
[0039] Before installation, the wire is installed on the upper end of the grounding rod 12 through the fixing screw 13, so that the current carried by the grounding transformer box 1 and the flow guide iron plate 14 can be guided to the grounding rod 12 through the flow guide iron plate 14 and the wire, and the grounding rod 12 can guide the current to the ground, thereby facilitating the protection of the whole.
[0040] Meanwhile, the middle part of the grounding rod 12 is in the shape of "X", which facilitates the increase of the contact area between the grounding rod 12 and the ground, and facilitates the improvement of the conductivity of the grounding rod 12.
[0041] The rear end of the grounding transformer box 1 is provided with a transmission assembly, the lower end of the transmission assembly is connected with the grounding box 11, the transmission assembly comprises a pressing plate 16, a connecting rod 17 and a reset spring 22, the pressing plate 16 is installed in the lower end of the grounding transformer box 1, the lower end of the pressing plate 16 is fixedly provided with the connecting rod 17, and the upper end of the connecting rod 17 is provided with the reset spring 22 in the grounding transformer box 1.
[0042] The pressing plate 16 and the connecting rod 17 are connected with the grounding transformer box 1 in a sliding manner, the lower end of the connecting rod 17 extends into the grounding box 11, the connection between the pressing plate 16 and the adjusting block 15 is provided with a matching inclined surface structure, the rear end of the grounding transformer box 1 is provided with a maintenance door 9 on the rear side of the flow guide iron plate 14 through a hinge, the inner side of the maintenance door 9 is fixedly provided with the adjusting block 15, the opening and closing of the maintenance door 9 drives the adjusting block 15, the pressing plate 16 and the connecting rod 17 to move correspondingly, thereby facilitating the subsequent change of the state of the connecting plate 18 and the clamping plate 19, playing a good auxiliary transmission role and improving the convenience of the whole.
[0043] The inside of the grounding box 11 is provided with a limiting assembly below the transmission assembly, the limiting assembly is connected with the grounding rod 12, the limiting assembly comprises a connecting plate 18, a clamping plate 19, a torsion spring shaft 20 and an insulating sheet 21, the connecting plate 18 is installed in the inside of the grounding box 11, and the connecting plate 18 is in contact with the lower end of the connecting abutting rod 17, and the outer side of the end of the connecting plate 18 close to the grounding rod 12 is fixedly installed with the clamping plate 19.
[0044] The inside of the end of the clamping plate 19 close to the connecting plate 18 is provided with the torsion spring shaft 20 in penetration, and the torsion spring shaft 20 constitutes a rotating structure in the grounding box 11 through a bearing, and the outer side of the torsion spring shaft 20 is pasted with the insulating sheet 21, and the connecting plate 18 and the torsion spring shaft 20 have a good adjusting effect on the clamping plate 19, so that the connecting plate 18 can drive the clamping plate 19 to rotate synchronously with the connecting plate 18 through the torsion spring shaft 20 under the extrusion of the connecting abutting rod 17, so that the torsion spring shaft 20 and the insulating sheet 21 can be closely connected with the grounding rod 12, thereby improving the stable effect of the grounding rod 12, and improving the close and reliable contact between the grounding rod 12 and the ground.
[0045] Working principle
[0046] Firstly, the whole is fixedly installed on the installation rail through the installation base 2 and the screw, then the flow guide iron plate 14 is opened, the grounding rod 12 is sequentially inserted into the insulating pipe 10, the grounding box 11 and the ground bottom from top to bottom, and the wire connected with the flow guide iron plate 14 is installed on the outer side of the upper end of the grounding rod 12 through the fixing screw 13. Then the access door 9 is closed and locked, at this time, the two groups of adjusting blocks 15 move to the outer side of the upper end of the pressing plate 16 with the closing of the access door 9, at this time, the inclined surface on the upper end of the pressing plate 16 is matched with the inclined surface in the inside of the lower end of the adjusting block 15 and slides, so that the adjusting block 15 generates downward extrusion on the pressing plate 16, and the pressing plate 16 and the connecting abutting rod 17 move downward in the grounding transformer box 1, and the reset spring 22 is compressed.
[0047] When the connecting abutting rod 17 moves downward, the connecting abutting rod 17 generates downward extrusion on the connecting plate 18, at this time, the connecting plate 18 and the clamping plate 19 move in a circular motion around the torsion spring shaft 20 under the action of the connecting abutting rod 17, so that the clamping plate 19 moves to the end close to the grounding rod 12, and the insulating sheet 21 is closely connected with the grounding rod 12, thereby facilitating the clamping of the two groups of insulating sheets 21 on the grounding rod 12, having a good stable function on the inserted grounding rod 12, improving the close and reliable contact between the grounding rod 12 and the ground, facilitating the improvement of the protection function of the grounding transformer, and facilitating the grounding transformer to better provide sufficient and effective safety protection for the wind power generation power supply system.
[0048] When it is necessary to adjust or disassemble the height of the grounding rod 12, only the maintenance door 9 is opened, and the maintenance door 9 drives the adjusting block 15 away from the pressing plate 16 at the same time, so that the adjusting block 15 releases the pressing plate 16 and the connecting rod 17 from extrusion, at this time, the reset spring 22 in the compressed state restores the deformation, drives the connecting rod 17 and the pressing plate 16 to return to the original position, at the same time, the torsion spring shaft 20 restores the deformation, drives the clamping plate 19 to move away from the grounding rod 12, that is, the clamping plate 19 is released from the clamping action, which improves the overall use convenience.
[0049] When the grounding transformer body 3 works, the heat conduction block 6 can absorb the heat generated by the grounding transformer body 3 working and conduct to the heat conduction plate 5, which facilitates the heat conduction plate 5 to transfer the heat to the first and second heat dissipation fins 7 and 8, so as to facilitate the heat dissipation of the heat inside the grounding transformer box 1 through the first and second heat dissipation fins 7 and 8, and the setting of the first and second heat dissipation fins 7 and 8 can enhance the air flow, which helps to more effectively transfer the heat from the transformer to the air, so that the whole has better heat dissipation function, and the internal temperature will not be too high, which avoids that the high temperature affects the normal fault detection work of the whole wind power supply system.
[0050] The technical features of the above embodiments can be combined in any manner (as long as the combination of the technical features does not exist contradictory), in order to make the description simple, not all possible combinations of the technical features in the above embodiments are described; these embodiments which are not explicitly written should also be considered as the scope of the present application.
Claims
1. A grounding transformer for detecting faults in a wind power generation system, comprising a grounding transformer housing (1), a heat conducting plate (5) and a guide iron plate (14), characterized in that: A transmission assembly is provided at the lower rear end of the grounding transformer box (1), a grounding box (11) is connected to the outer side of the lower end of the transmission assembly, a limit assembly located below the transmission assembly is provided inside the grounding box (11), and the limit assembly is connected to the grounding rod (12); A heat conducting plate (5) is fixedly mounted on the rear side of the upper end of the grounding transformer box (1), and heat conducting blocks (6) are evenly spaced and mounted on the outer side of the front end of the heat conducting plate (5); a first heat dissipation fin (7) is provided on the upper side of the rear end of the heat conducting plate (5), and a second heat dissipation fin (8) is fixedly connected to the side of the rear side of the heat conducting plate (5); A guide iron plate (14) is fixedly installed in the middle of the rear side of the grounding transformer box (1), a grounding rod (12) is installed inside the rear end of the guide iron plate (14), and the lower end of the grounding rod (12) is inserted into the lower end of the grounding transformer box (1).
2. A grounding transformer for detecting faults in a wind power generation and power supply system according to claim 1, characterized in that: Mounting bases (2) are fixedly mounted on the left and right sides of the lower end of the grounding transformer box (1), a grounding transformer body (3) is arranged inside the grounding transformer box (1), and a coil assembly (4) is arranged on the outer side of the upper end of the grounding transformer box (1).
3. A grounding transformer for detecting faults in a wind power generation and power supply system according to claim 1, characterized in that: An insulating tube (10) is installed in the middle of the lower end of the grounding transformer box (1), and the lower end of the insulating tube (10) is connected to the grounding rod (12). The grounding rod (12) passes through the inside of the insulating tube (10) and the grounding box (11). The middle cross section of the grounding rod (12) is an "X"-shaped structure. A fixing screw (13) for installing a wire is provided in the middle of the upper end of the grounding rod (12).
4. A grounding transformer for detecting faults in a wind power generation and power supply system according to claim 2, characterized in that: The grounding transformer body (3) is located directly in front of the heat conducting block (6), and the front end diameter of the heat conducting block (6) is larger than the rear end diameter.
5. The grounding transformer for detecting faults in a wind power generation and power supply system according to claim 1, characterized in that: The length of the first heat dissipation fin (7) is greater than the length of the second heat dissipation fin (8), and the first heat dissipation fin (7) and the second heat dissipation fin (8) are arranged in an up-and-down staggered manner.
6. A grounding transformer for detecting faults in a wind power generation and power supply system according to claim 1, characterized in that: An inspection door (9) located behind the guide iron plate (14) is installed inside the rear end of the grounding transformer box (1) through a hinge, the second heat dissipation fins (8) are located on both sides of the inspection door (9), and an adjustment block (15) is fixedly installed on the inner side of the inspection door (9).
7. A grounding transformer for detecting faults in a wind power generation and power supply system according to claim 1, characterized in that: The transmission assembly comprises a pressing plate (16), a connecting push rod (17) and a return spring (22); the pressing plate (16) is mounted inside the lower end of the grounding transformer box (1), and the connecting push rod (17) is fixedly mounted on the outer side of the lower end of the pressing plate (16); and the return spring (22) located in the grounding transformer box (1) is mounted on the outer side of the upper end of the connecting push rod (17).
8. A grounding transformer for detecting faults in a wind power generation and power supply system according to claim 7, characterized in that: The pressing plate (16) and the connecting rod (17) are both connected to the grounding transformer box (1) in a sliding manner, and the lower end of the connecting rod (17) extends to the interior of the grounding box (11). The connection between the pressing plate (16) and the adjustment block (15) is provided with a matching inclined surface structure.
9. The grounding transformer for detecting faults in a wind power generation and power supply system according to claim 1, characterized in that: The limiting assembly comprises a connecting plate (18), a clamping plate (19), a torsion spring shaft (20) and an insulating sheet (21); the connecting plate (18) is installed inside the grounding box (11), and the connecting plate (18) contacts the lower end of the connecting rod (17); the clamping plate (19) is fixedly installed on the outer side of one end of the connecting plate (18) close to the grounding rod (12).
10. A grounding transformer for detecting faults in a wind power generation and power supply system according to claim 9, characterized in that: A torsion spring shaft (20) is provided inside one end of the clamping plate (19) close to the connecting plate (18), and the torsion spring shaft (20) forms a rotating structure in the grounding box (11) through a bearing. An insulating sheet (21) is adhered to the outer side of the torsion spring shaft (20).