Construction method for grounding resistance-reducing grounding grid of wind turbine generator

Abstract

The invention provides a construction method for a grounding resistance-reducing grounding grid of a wind turbine generator. The construction method mainly comprises the steps of digging a trench at a preset position, laying a resistance-reducing agent, connecting a vertical grounding electrode and a horizontal grounding body in a welding mode, manually digging a connecting wire trench, and enhancing the stability of a system by using a grounding module. By applying the method, the grounding resistance of the wind turbine generator can be effectively reduced, the stability of the wind turbine generator can be kept, and the operation safety of the wind turbine generator is greatly improved. Compared with a traditional construction method, the method has the advantages of being easy and convenient to construct, high in efficiency and the like, and is an ideal resistance-reducing grounding grid construction method in the field of wind power generation.

Description

Technical Field

[0001] The invention belongs to the field of electric power, and more specifically relates to a method for constructing a grounding grid for reducing resistance of a wind turbine generator set. Background Art

[0002] In the wind power generation system, the grounding network of the wind turbine is an important facility to ensure the safe operation of the wind turbine. Due to the tall and large characteristics of the wind turbine, it is easy to be struck by lightning. Under the impact of lightning, if the grounding resistance of the wind turbine is too large, it will cause serious harm to people and equipment. Therefore, it is necessary to design a method to reduce the grounding resistance of the wind turbine.

[0003] In the traditional wind turbine grounding network, the grounding resistance is mainly reduced by laying grounding wires with a length of several hundred meters or even thousands of meters near the wind turbine foundation. However, this method is time-consuming and labor-intensive in construction, and in later use, due to the excessive length of the grounding wires and the large wire spacing, it is very easy to cause unstable grounding resistance and sudden increase of grounding resistance.

[0004] At the same time, in the traditional method of grounding and reducing resistance of wind turbines, the grounding body is often buried in the subsoil layer. Factors such as the moisture content and salt content of the subsoil layer will significantly affect the magnitude of the grounding resistance. This causes the value of the grounding resistance to fluctuate greatly in different seasons and even at different times of the day, affecting the normal operation of the wind turbine and the safety and stability of the power system.

[0005] Therefore, it is an urgent problem to be solved in the current field of wind turbine technology to study and improve the construction method of the grounding grid for reducing the grounding resistance of wind turbines, reduce the grounding resistance of wind turbines, and maintain the stability of the grounding resistance. Summary of the invention

[0006] The present invention aims to solve the problems existing in the prior art of complex construction of grounding grid for reducing resistance of wind turbines and unstable grounding resistance, and proposes a construction method which is simple, efficient, and can effectively reduce the grounding resistance of wind turbines and maintain its stability.

[0007] In order to achieve the above object, the present invention is implemented by adopting the following technical scheme: the method comprises:

[0008] Use an excavator to dig a trench at the predetermined location, nail in the vertical grounding electrode, and connect the vertical grounding electrode to the horizontal grounding body by welding.

[0009] Then lay the resistance reducing agent in the trench and wrap the horizontal grounding body.

[0010] Finally fill the soil and compact it.

[0011] It also includes the artificial excavation of the connecting wire trench. Vertical grounding electrodes and horizontal grounding bodies are nailed into the connecting wire trench at certain intervals along the excavated trench. Grounding modules are also installed along both sides of the connecting wire. Finally, the soil is filled and compacted.

[0012] In one solution, vertical grounding electrodes, including Φ30 steel pipes and L40×40×4 angle steels, are nailed in at regular intervals along the excavated trench.

[0013] In one solution, grounding modules are installed on both sides of the connecting wire, and one end of the grounding module is welded to the connecting wire on both sides, with the overlap ratio being greater than 6 times the diameter of the round steel.

[0014] In one solution, the resistor is laid in the trench with a thickness of about 20 cm to 40 cm, completely wrapping the horizontal grounding body therein with a width greater than 80 cm.

[0015] In one scheme, the overlap ratio of the flat steel and the round steel is not less than 6 times the diameter of the round steel, and double-sided welding is performed.

[0016] In one solution, the connecting wire is welded to the inner ring of the wind turbine tower foundation, and the connecting wires led out from the inner ring of the wind turbine tower foundation use two 60×6 hot-dip galvanized flats to ensure connection reliability.

[0017] In one solution, a 20 to 30 cm portion is reserved at the upper end of the vertical grounding electrode to facilitate welding of the horizontal grounding body.

[0018] In one scheme, the grounding trench is excavated according to the depth and width of the grounding laying, and the depth is based on the highest standard required by the design or specification, with an over-excavation of about 50-100mm.

[0019] Beneficial effects of the present invention:

[0020] The wind turbine grounding resistance reduction grounding grid construction method is simple, and compared with the traditional wind turbine grounding network construction, the construction difficulty and construction time are greatly reduced.

[0021] The method can effectively reduce the grounding resistance of the wind turbine generator set, maintain the stability of the grounding resistance, and reduce grounding faults.

[0022] Since the trench in this method is welded and excavated manually, the connection between the grounding body and the grounding electrode is more secure, which effectively prevents the grounding body and the grounding electrode from falling off or breaking, thereby improving the safety and stability of the grounding equipment.

[0023] By laying a resistance-reducing agent in the trench to wrap the horizontal grounding electrode, the conductivity of the soil can be effectively improved, thereby further reducing the grounding resistance.

[0024] By reserving the upper end of the vertical grounding electrode, later maintenance and inspection are facilitated, thereby increasing the service life of the grounding network. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Prepare installation plan diagram for resistance reduction grounding grid of No. 4 and No. 5 wind turbines;

[0026] Figure 2 Prepare a schematic installation plan for the resistance reduction grounding grid for wind turbines No. 32 and No. 33. DETAILED DESCRIPTION

[0027] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. Typical embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in the present invention. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0028] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used in the present invention in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. Typical embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in the present invention. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0029] A method for constructing a grounding grid for reducing resistance of a wind turbine generator set, 1. The method comprises:

[0030] Use an excavator to dig a trench at a predetermined location, nail in a vertical grounding electrode, connect the vertical grounding electrode to the horizontal grounding body by welding, then lay a resistance reduction agent in the trench and wrap the horizontal grounding body, finally fill in the soil and compact it. It also includes the manual excavation of the connecting wire trench. The connecting wire trench has vertical grounding electrodes and horizontal grounding bodies nailed in at certain intervals along the excavated trench, and grounding modules are installed along both sides of the connecting wire. Finally, fill in the soil and compact it.

[0031] Whether the resistance reduction effect can meet the design requirements, the grounding system design is only one aspect that affects the grounding effect. Another key factor is the construction process. For example, when using the resistance reduction agent, it is not fully laid according to the design requirements, the vertical grounding electrode and the horizontal grounding electrode are not well welded at the connection with the main ground grid, the soil with low resistivity is not backfilled as required and not compacted enough, and the grounding body and the resistance reduction agent are not fully combined. In the process of construction according to the design, problems with certain construction processes will directly affect the grounding resistance value of the ground grid after the construction is completed. The process requirements for the main construction content are as follows:

[0032] (1) The horizontal grounding body and connecting conductor are made of -60×6 hot-dip galvanized flat steel. When installing the resistance-reducing grounding grid, ensure that it is flat and straight; when installing the connecting conductor, try to ensure that it is short, flat and straight, and any bends should be smooth.

[0033] (2) Due to geological conditions, vertical grounding electrodes can be made of hot-dip galvanized Φ50 steel pipes, L50×50×5 and L40×40×4 angle steels. The depth can be based on the geological conditions and buried vertically as deep as possible, not less than 1m; the spacing is required to be greater than 5m.

[0034] (3) Conductor connections are lap welded, with good welding and no false welds. The lap length of flat steel is not less than 18 cm, and welding is performed on three sides; the lap multiple of flat steel and round steel is not less than 6 times the diameter of the round steel, and double-sided welding is performed; the side flat steel is welded on three sides with the angle steel, and semi-wrapped three-sided welding is used with the vertical steel pipe, and the flat flat steel is fully welded with the vertical steel pipe and angle steel.

[0035] (4) Dig the grounding trench according to the grounding laying depth and width required by the design or specification. The depth shall be based on the highest standard required by the design or specification, and the over-digging shall be about 50-100mm. The trench wall needs to be sloped, and any stones at the bottom should be removed.

[0036] (5) The resistance reducing agent and water are fully mixed and evenly mixed until the viscosity is plastic; they are laid evenly according to the design requirements without any impurities; the horizontal grounding body is completely covered. The fine soil is backfilled and compacted.

[0037] Example:

[0038] A certain project has four wind turbines, 4#, 5#, 32# and 33#, and the specific construction process is as follows.

[0039] Installation steps and requirements for the grounding grid installation of 4# and 5# wind turbines

[0040] 4# fan resistance reduction grounding grid and connecting wires

[0041] (1) Fabrication, laying and installation of the resistance reduction grounding grid for 4# wind turbine

[0042] a. Use an excavator to dig a trench 44m long, 1m wide, and 0.8-0.9m deep at the predetermined location, and nail in a vertical grounding electrode (1m long L50×50×5 angle steel or Φ50 steel pipe). If you encounter a thick soil layer, try to lengthen the length of the vertical grounding electrode, and reserve 20-30cm at the upper end of the vertical grounding electrode to facilitate welding of the horizontal grounding electrode.

[0043] b. To ensure the reliability of the connection between the horizontal grounding body and the vertical grounding electrode, two horizontal grounding bodies are welded in the trench, one for the side elevation and the other for the horizontal surface, to increase the reliability of the contact surface and the grounding grid. First, weld the horizontal grounding body placed on the side elevation 20 cm from the bottom of the trench to the vertical grounding electrode (angle steel or steel pipe), and use the three-sided welding method at the connection. Then weld the horizontal grounding body placed on the horizontal surface. At the welding point of the flat steel and the round steel, bend the flat steel into an arc shape to ensure its contact surface and firmness. After welding, brush asphalt paint on the welding point.

[0044] c. Dilute the resistance reducing agent and stir it thoroughly to a moderate viscosity, then lay it in the trench with a thickness of about 20cm to 40cm, completely wrapping the horizontal grounding body in it, with a width greater than 80cm. After the resistance reducing agent solidifies and stabilizes, fill it with fine soil and tamp it.

[0045] (2) Grounding installation of the 4# fan connecting wire

[0046] a. The trench for connecting the wires between the foundation platform of the 4# wind turbine and the newly added grounding grid was excavated manually, and a trench about 120m long, 0.4m wide, and 0.3m-0.5m deep was excavated. The trench was excavated straight from the predetermined location of the newly added grounding grid to the direction of the wind turbine platform. There were some stones and cypress trees blocking the front half, so appropriate adjustments and avoidances were made. Since the bushes needed to be passed through the back half, the bushes were slightly trimmed to make them as short, flat, and straight as possible.

[0047] b. Twelve Φ30 steel pipes and seven L40×40×4 angle steels were nailed in every 4 to 6 meters along the excavated trench as vertical grounding electrodes; -60×6 flat steel horizontal grounding bodies were laid along the trench and overlapped and welded into a whole, with an overlap length of not less than 18cm and welded on three sides, and then welded to the Φ30 steel pipe and L40×40×4 angle steel, with welding on no less than 3 sides.

[0048] c. Install grounding modules on both sides of the connecting wire, dig a 1.3m long and 0.3m wide trench in the vertical direction of the connecting wire, put in 14 grounding modules, weld one end of the grounding module to the connecting wire on both sides, and the overlap multiple is greater than 6 times the diameter of the round steel (about 96mm). In order to ensure the connection reliability between the horizontal grounding body and the vertical grounding electrode, use flat steel to weld from the other side of the vertical grounding electrode to increase the contact surface. At the welding point between the flat steel and the round steel, bend the flat steel into an arc shape to ensure its contact surface and firmness. After welding, apply asphalt paint and then fill it, and finally fill the soil and tamp it.

[0049] 5# fan resistance reduction grounding grid production, laying and installation

[0050] (1) Fabrication, laying and installation of the resistance reduction grounding grid for 5# wind turbine

[0051] Use an excavator to dig a trench 64m long, 1m wide and 0.8-0.9m deep at the predetermined location. Other production and laying methods are the same as the 4# wind turbine resistance reduction grounding grid.

[0052] (2) Grounding installation of the 5# fan connecting wire

[0053] From the predetermined location of the newly added grounding grid, we excavated in a straight line toward the wind turbine platform. We made appropriate adjustments and avoidances to the places blocked by some stones and pine trees, and tried to meet the requirements of being short, flat and straight. We excavated a trench about 122m long, 0.4m wide and 0.3m-0.5m deep. Twelve Φ30 steel pipes and 19 L40×40×4 angle steels were nailed in every 2-3m along the excavated trench, for a total of 31. We installed grounding modules on both sides of the connecting wire, excavated a trench 1.3m long and 0.3m wide in the vertical direction of the connecting wire, and put in 22 grounding modules. The rest is the same as the 4# fan connecting wire.

[0054] Grid connection of 4# and 5# wind turbine resistance reduction grounding grid and connection with the main grounding grid of wind turbines

[0055] (1) Dig a trench about 52m long, 0.8m wide and 0.8m deep between the 4# wind turbine resistance reduction grounding grid and the 5# wind turbine resistance reduction grounding grid. Use -60×6 hot-dip galvanized flat wire to make two welded wires as connecting wires to connect the two grounding grids.

[0056] (2) The connecting wires are welded to the inner rings of the tower foundations of wind turbines No. 4 and No. 5 respectively. The connecting wires drawn out from the inner rings of the tower foundations of the wind turbines are two 60×6 hot-dip galvanized flats to ensure the reliability of the connection.

[0057] (3) The overall resistance reduction grounding grid is as follows Figure 1 shown.

[0058] 32#, 33# wind turbines resistance reduction grounding body and connecting wire laying installation steps and requirements 32#, 33# wind turbines resistance reduction grounding body production, laying and installation

[0059] According to the design, 32# and 33# wind turbines share a resistance reduction grounding grid.

[0060] (1) Due to the limitation of construction conditions, the resistance reduction grounding grid was installed in the low-lying area beside the villagers' land. A deep pit with a length of 6m, a width of 2m to 4m, and a depth of about 1.5m to 2.0m was excavated, and a vertical grounding electrode (1m long L50×50×5 angle steel or Φ50 steel pipe) was nailed in. If the soil layer was thick, the length of the vertical grounding electrode should be extended as much as possible, and a 20-30cm part was reserved at the upper end of the vertical grounding electrode to facilitate welding of the horizontal grounding body, and then the whole was nailed in after welding was completed. The resistance reduction grounding grid used a total of 38 L50×50×5 angle steels, 8 Φ50 steel pipes, 20 -60×6 flat steels, and 50 bags of resistance reduction agent (about 1 ton) to form a three-dimensional grounding body.

[0061] (2) To ensure the reliability of the connection between the horizontal grounding electrode and the vertical grounding electrode, two horizontal grounding electrodes are welded in the trench, one for the side elevation and the other for the horizontal surface, to increase the reliability of the contact surface and the grounding grid. First, weld the horizontal grounding electrode placed on the side elevation 20 cm from the bottom of the trench to the vertical grounding electrode (angle steel or steel pipe), and use the three-sided welding method at the connection. Then weld the horizontal grounding electrode placed on the horizontal surface. At the welding point of the flat steel and the round steel, bend the flat steel into an arc shape to ensure its contact surface and firmness. After welding, brush asphalt paint on the welding point.

[0062] (3) Since the soil layer at the location of the ground grid is thick and clay, which is not easy to drain, the resistance reducing agent does not need to be diluted and is directly poured into the pit. The thickness of the resistance reducing agent in the trench is about 30cm, which completely wraps the entire ground grid. Finally, the soil is filled and compacted.

[0063] 32# fan connection wire laying

[0064] (1) Lay the connecting wire between the 32# wind turbine platform and the resistance reduction grounding grid. The first half of the trench is excavated mechanically, starting from the edge of the wind turbine platform and excavating 212 meters along the drainage ditch on the inner side of the road. After that, it is necessary to pass through the bushes, and only 103 meters can be excavated manually to reach the vicinity of the newly added grounding grid. In the first half of the mechanical excavation, about 200 meters, the trench diagonally crosses the road and the manually excavated trench is connected. The excavation depth at the diagonal crossing of the road is about 1 meter. A trench about 315 meters long, 0.3m~0.5m wide, and 0.5m~0.8m deep was excavated. If stones are encountered during the excavation process, appropriate adjustments and avoidances can be made to try to meet the requirements of being short, flat, and straight.

[0065] (2) Along the excavated trench, in areas with good soil quality and thick soil layers, four L50×50×5 and three L40×40×4 angle steels were nailed in every 8 meters or so as vertical grounding electrodes, for a total of seven. -60×6 flat steel was used as the horizontal grounding body, laid along the trench and welded into a whole, with an overlap length of not less than 18cm, and welded on three sides. Finally, it was welded with L50×50×5 and L40×40×4 angle steels, with welding on no less than three sides, for a total of 53 flat steels.

[0066] (3) Place 6 grounding modules in parallel with the connecting wires. One end of the grounding module is welded to the connecting wires on both sides. The overlap is greater than 6 times the diameter of the round steel (about 96 mm). In order to ensure the connection reliability between the horizontal grounding body and the vertical grounding electrode, flat steel is welded from the other side of the vertical grounding electrode to increase the contact surface. At the welding point between the flat steel and the round steel, the flat steel is bent into an arc shape to ensure its contact surface and firmness. After welding, apply asphalt paint and then fill it. Finally, fill it with soil and compact it.

[0067] 33# fan connecting wire laying

[0068] (1) Lay the connecting wire between the 33# wind turbine platform and the resistance reduction grounding grid. The trench is excavated mechanically from the edge of the wind turbine platform along the drainage ditch on the inner side of the road. The trench is about 106m long, 0.5m wide and 0.3m-0.5m deep.

[0069] (2) Two Φ50 steel pipes, 18 L50×50×5 and 4 L40×40×4 angle steels were nailed into the trench every 4 to 6 meters as vertical grounding electrodes, for a total of 24.

[0070] (3) Other laying and installation methods are the same as those of 32# fan

[0071] Connection between the resistance reduction grounding grid of 32# and 33# wind turbines and the main grounding grid of the wind turbines

[0072] (1) The connecting wires are welded to the grounding rings of the No. 33 and No. 32 wind turbine tower foundations, that is, the connecting wires drawn from the inner ring of the wind turbine tower foundation are two 60×6 hot-dip galvanized flats to ensure connection reliability.

[0073] (2) The overall resistance reduction grounding grid is as follows Figure 2 shown.

[0074] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium, and when the program is executed, it can include the processes of the embodiments of the above-mentioned methods. The storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM).

[0075] It should be understood that the detailed description of the technical solutions of the present invention by means of the preferred embodiments is illustrative rather than restrictive. A person skilled in the art may modify the technical solutions described in the embodiments, or replace some of the technical features by equivalents, based on reading the specification of the present invention; and these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for constructing a grounding grid for reducing resistance of a wind turbine generator set, characterized in that: The method includes: Use an excavator to dig a trench at the predetermined location, nail in the vertical grounding electrode, and connect the vertical grounding electrode to the horizontal grounding body by welding. Then lay the resistance reducing agent in the trench and wrap the horizontal grounding body. Finally fill the soil and compact it. It also includes the artificial excavation of the connecting wire trench. Vertical grounding electrodes and horizontal grounding bodies are nailed into the connecting wire trench at certain intervals along the excavated trench. Grounding modules are also installed along both sides of the connecting wire. Finally, the soil is filled and compacted.

2. A wind turbine grounding resistance reduction grounding grid construction method according to claim 1, characterized in that: Vertical grounding electrodes, including Φ30 steel pipes and L40×40×4 angle steels, are nailed in at regular intervals along the excavated trench.

3. A wind turbine grounding resistance reduction grounding grid construction method according to claim 1, characterized in that: A grounding module is installed on both sides of the connecting wire. One end of the grounding module is welded to the connecting wire on both sides, and the overlap ratio is greater than 6 times the diameter of the round steel.

4. A wind turbine grounding resistance reduction grounding grid construction method according to claim 1, characterized in that: The resistor is laid in the trench with a thickness of about 20cm to 40cm, completely wrapping the horizontal grounding body and a width greater than 80cm.

5. A method for constructing a grounding grid for reducing resistance of a wind turbine according to claim 1, characterized in that: The overlap ratio of flat steel and round steel shall not be less than 6 times the diameter of the round steel, and double-sided welding shall be performed.

6. A method for constructing a grounding grid for reducing resistance of a wind turbine according to claim 1, characterized in that: The connecting wire is welded to the inner ring of the wind turbine tower foundation. The connecting wires led out from the inner ring of the wind turbine tower foundation use two 60×6 hot-dip galvanized flats to ensure connection reliability.

7. A wind turbine grounding resistance reduction grounding grid construction method according to claim 1, characterized in that: A 20 to 30 cm portion is reserved at the upper end of the vertical grounding electrode to facilitate welding of the horizontal grounding electrode.

8. A method for constructing a grounding grid for reducing grounding resistance of a wind turbine according to claim 1, characterized in that: The grounding trench is excavated according to the depth and width of the grounding laying. The depth shall be based on the highest standard required by the design or specifications, and the over-excavation shall be about 50-100mm.

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