Grounding grid construction method for high resistance small area

Abstract

The application relates to the technical field of grounding grids, and discloses a grounding grid construction method for a small-area high-resistance region. According to the limitation of a construction environment, the method adopts a deep-buried grounding grid device combined with a resistance-reducing agent filling and filling mode, so that the earthwork excavation engineering quantity is reduced as much as possible under the condition of the buried depth, the problem of the small geographical environment space of equipment installation and the large installation limitation of the comprehensive grounding device is solved, the construction period is reduced, and the construction operation amount is reduced; the horizontal grounding electrode and the vertical grounding electrode are arranged, and the two are electrically welded in an equipotential manner, so that the grounding resistance effect is better reduced, the technical and economic indexes are optimized, the construction difficulty is reduced, and the safe and stable operation of the grounding equipment is ensured; in addition, the application is a summary of practical engineering application, the present situation that a small-resistance grounding grid relies on a large surface area is improved, and practical experience of implementing deep-well grounding technology in a local small-area region is provided.

Description

Technical Field

[0001] This invention relates to the field of grounding grid technology, and in particular to a grounding grid construction method for high-resistance, small-area regions. Background Technology

[0002] Due to the limited space of the construction site, it was impossible to set up an independent grounding system using conventional methods. The average soil resistivity of the equipment and installation site was as high as 1300 Ω·m or more, making it impossible to reduce the overall grounding resistance to the standard requirement of no more than 0.4 Ω as stipulated by the national mandatory standard and the design reference guide for medical linear accelerators.

[0003] Following standard grounding grid expansion, adding more grounding electrodes, replacing low-resistivity soil, and injecting resistance-reducing agents are all standard and recommended methods for reducing grounding resistance, but these are difficult and simply impossible to implement. The reason is that the area available for grounding grid construction in hospitals is limited; the usable green space is small, and the area beneath the surface of the green space is mostly construction waste accumulated from the previous construction of the main building. Removing this waste and replacing the clay would significantly increase costs. Including the area occupied by public service roads and facilities within the hospital grounds for grounding grid construction would extensively damage existing public road infrastructure, further increasing the cost of infrastructure demolition and repair. Furthermore, the construction period would be lengthy, directly impacting the hospital's medical care, emergency response, and other medical operations during the construction phase. Summary of the Invention

[0004] The technical problem solved by this invention is to provide a grounding grid construction method for small areas with high resistance, which facilitates construction in narrow areas and improves the resistance reduction effect of the grounding grid.

[0005] The technical solution adopted by this invention to solve its technical problem is: a grounding grid construction method for high-resistance small areas, comprising the following steps:

[0006] S1: Analyze the soil composition, determine the maximum frozen soil thickness based on historical statistics, measure the soil resistivity of different soil layers at the construction site, and formulate a construction plan based on the existing construction site and conditions.

[0007] S2: The burial depth of the horizontal grounding electrode is greater than the maximum frost thickness. Excavate the trench for burying the horizontal grounding electrode. Then, determine the spacing, diameter and depth of the wells for the installation of the vertical grounding electrode according to the soil composition. Then, lay out the positioning on the construction site and drill the wells for the installation of the vertical grounding electrode.

[0008] S3: Make a vertical grounding electrode using galvanized steel pipe, then install the vertical grounding electrode in the center of the well, and fill the well and galvanized steel pipe with a drag-reducing agent to ensure that the drag-reducing agent is fully filled in the well and galvanized steel pipe.

[0009] S4: Make a horizontal grounding electrode using galvanized flat steel, wrap a resistance-reducing agent of not less than 300mm around the horizontal grounding electrode, install the horizontal grounding electrode in the center of the trench, and then perform equipotential electrical welding between the horizontal grounding electrode and the vertical grounding electrode.

[0010] S5: Electrically connect the installed grounding grid and test its resistance. If the resistance does not meet the equipment requirements, add a vertical grounding electrode and weld it to the horizontal grounding electrode at the same potential. After the grounding grid resistance meets the standard, backfill and compact the external grounding wires of the grounding grid with clay with low resistivity.

[0011] Furthermore, in step S2, mechanical drilling is adopted, with a borehole spacing of 5m and a drilling depth of 15m.

[0012] Furthermore, in step S3, through holes are opened on the outer peripheral wall of the galvanized steel pipe along its axial direction, with a hole diameter ≥ Φ14mm and a through hole spacing of 1m~1.5m.

[0013] Furthermore, in step S4, the horizontal grounding electrode and the vertical grounding electrode are electrically welded, with welding on no less than three sides, and the welded joints are treated with anti-corrosion measures.

[0014] Furthermore, in steps S3 and S4, the drag-reducing agent is a physical long-lasting drag-reducing agent.

[0015] The beneficial effects of this invention are as follows: Based on the limitations of the construction environment, this invention adopts a deep-buried grounding grid device combined with resistance-reducing agent filling and filling method, minimizing earthwork excavation while utilizing the burial depth. This improves the problems of limited geographical space for equipment installation and the significant limitations of integrated grounding device installation, reducing the construction period and workload. Furthermore, by setting horizontal and vertical grounding electrodes and equipotentially welding them, this invention achieves better grounding resistance reduction, optimizes technical and economic indicators, reduces construction difficulty, and ensures the safe and stable operation of the grounding equipment. In addition, this invention is a summary of practical engineering applications, improving upon the previous reliance on large surface areas for low-resistance grounding grids, and providing practical experience for implementing well grounding technology in localized, small-area areas. Detailed Implementation

[0016] The present invention will be further described below with reference to specific embodiments.

[0017] The grounding grid construction method for high-resistivity small areas according to the present invention includes the following steps:

[0018] S1: Soil composition analysis was conducted, and the maximum frozen soil thickness was determined based on historical statistics. According to these statistics, the maximum frozen soil thickness in the Liangshan area is 80cm. Soil resistivity was measured at different soil layers at the construction site, and a construction plan was developed based on the existing construction site and conditions. Related public service roads and facilities within the site were paved with concrete, and the green area is approximately 30×36m². 2 Furthermore, according to the hospital's disclosure, the area beneath the green space is mostly construction waste accumulated during the construction of the earlier comprehensive building. Removing the construction waste and replacing the clay will also increase the financial investment. The construction site is small and cannot be equipped with an independent grounding system. The average soil resistivity of the equipment and installation site is as high as 1300Ω·m or more. The national mandatory standard for comprehensive grounding resistance and the design reference guide for medical linear accelerators stipulate that it should not exceed 0.4Ω. Based on the construction conditions and in coordination with the hospital's requirements, the construction plan was determined, and a construction method of deep burial grounding device combined with resistance-reducing agent filling was adopted.

[0019] S2: The burial depth of the horizontal grounding electrode should be greater than the maximum frost thickness. A trench should be dug for the horizontal grounding electrode. Since the maximum frost thickness is 80cm, the trench depth for the horizontal grounding electrode installation should be 1.5m. Based on the workable area and the soil resistivity, the grounding resistance of the grounding grid formed by only the horizontal grounding electrodes is calculated. Then, the resistance of the additional vertical grounding electrodes is determined based on the difference between the calculated grounding resistance and the required resistance. The calculation is based on the empirical formula for the grounding resistance of artificial grounding electrodes in soil.

[0020]

[0021] In the formula: R p —Grounding resistance (Ω) of the horizontal grounding electrode; r —Soil resistivity (Ω.m); L —Total length of horizontal grounding electrode (m); h — Burial depth of horizontal grounding electrode (m); d —Diameter or equivalent diameter of the horizontal grounding electrode (m); A — Shape factor of horizontal grounding electrode (1 for mesh). — Utilization coefficient of drag reducer.

[0022] Furthermore, the formula for calculating the grounding resistance value after multiple vertical grounding electrodes are connected in parallel and in parallel with a horizontal grounding electrode is as follows:

[0023]

[0024] In the formula: R —Grounding resistance of the grounding grid (Ω); R z —Grounding resistance of the vertical grounding electrode (Ω); n This refers to the number of vertical grounding electrodes;R p —Grounding resistance (Ω) of the horizontal grounding electrode; or To utilize the coefficient ( or <1), which is related to the length and spacing of the vertical grounding electrode, and can usually be taken as 0.65 to 0.9.

[0025] Theoretically, considering the uniform soil geological structure (soil resistivity 1300Ω·m), and constructing horizontal grounding electrodes with a grounding grid area of ​​15.2m × 13.2m (buried depth 2m), the grounding resistance can reach 32.1Ω, far below the standard requirement of no more than 0.4Ω for safe grounding of linear accelerators. Therefore, based on the actual situation, if high-tech methods (electrolytic ion rods, etc.) and coating with resistance-reducing agents are used for construction, theoretically, electrolytic ion grounding technology would significantly increase costs (4000 yuan / rod, theoretical usage 50 rods); the amount of resistance-reducing agent used (8000 yuan / ton, theoretical usage 10 tons) would also increase the overall grounding grid construction cost significantly. For economic reasons, galvanized steel pipes and physical long-lasting resistance-reducing agents are used to construct vertical grounding electrodes. Since the well passes through soil layers with different resistivities (lower at the bottom and higher at the top), the average soil resistivity is used for theoretical calculation. The formula for calculating the grounding resistance of a single vertical grounding electrode is as follows:

[0026]

[0027] In the formula: R z —Grounding resistance of the vertical grounding electrode (Ω); r —Soil resistivity or average soil resistivity (Ω·m). —Total length of vertical grounding electrode (m); d 0 —The diameter or equivalent diameter of the vertical grounding electrode (m). In the formula, forming a low-resistivity material filling region (physical long-lasting resistance-reducing agent, etc.) around the grounding electrode is equivalent to increasing the equivalent diameter of the grounding electrode. d 0 The total length and diameter or equivalent diameter range of the vertical grounding electrodes are determined based on the required resistance. Considering the geological structure, soil composition, and construction difficulty, and ensuring the grounding grid can be installed and the structure is stable, the drilling depth is first determined to be 15m, then the equivalent diameter of the vertical grounding electrodes is determined, and finally the drilling spacing and borehole diameter are determined. Since there are three groups of vertical grounding electrodes, three boreholes are drilled at fixed points, with a diameter of 200mm, a spacing of 5m, and a depth of 15m. Mechanical drilling is used, with the location marked on the construction site, and the boreholes drilled for the installation of the vertical grounding electrodes are then prepared.

[0028] S3: A vertical grounding electrode is made using a Φ40 galvanized steel pipe. Through holes with a diameter of 15mm are opened on the outer circumference of the galvanized steel pipe along its axial direction. The through holes are spaced 1.2m apart. The through holes can be set in an alternating oblique manner. The vertical grounding electrode is then installed in the center of the well. A resistance-reducing agent is poured into the well and inside the galvanized steel pipe to ensure that the resistance-reducing agent is fully filled in the well and inside the galvanized steel pipe.

[0029] S4: Use galvanized flat steel of specification -50×5 to make horizontal grounding electrodes, and wrap the upper surface of the horizontal grounding electrode with a resistance reducing agent of not less than 300mm. Install the horizontal grounding electrode in the center of the trench, and then perform equipotential electrical welding between the horizontal grounding electrode and the vertical grounding electrode, with welding on no less than three sides, and perform anti-corrosion treatment on the weld.

[0030] S5: Electrical connection was established for the installed grounding grid, and its resistance was tested. The on-site test showed a grounding resistance of 0.46Ω, indicating an ideal resistance reduction mechanism. Although the medical linear accelerator could be powered on, it did not meet the 0.4 ohm safety grounding requirement for medical linear accelerator equipment. Therefore, an additional set of vertical grounding electrodes was installed and electrically welded to the horizontal grounding electrodes at equipotential. The grounding grid resistance was then tested again, and the overall grounding grid resistance was 0.38Ω, meeting the required safety grounding standards for the equipment. Finally, the external grounding wires of the grounding grid were backfilled and compacted using clay with low resistivity.

[0031] This invention uses a deep-buried grounding grid device combined with resistance-reducing agent filling to create a comprehensive grounding grid. Compared with conventional methods of increasing the area to reduce resistance, the cost is significantly reduced, the construction period is short, and the efficiency is high, with almost no impact on the normal medical care work of the hospital.

[0032] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A grounding grid construction method for a high resistance small area, characterized by: The method comprises the following steps: S1: analyzing soil composition, determining maximum frozen soil thickness according to historical statistics, measuring soil resistivity of different soil layers at the construction site, and formulating a construction scheme in combination with the existing construction site and construction conditions; S2: the embedding depth of the horizontal grounding electrode is greater than the maximum frozen soil thickness, a embedding trench of the horizontal grounding electrode is dug out, and the resistance R of the horizontal grounding electrode is calculated according to the horizontal grounding electrode embedded in the embedding trench p , and the calculation formula is: , wherein R p is the grounding resistance of the horizontal grounding electrode, in Ω; p is the soil resistivity, in Ω.m; L is the total length of the horizontal grounding electrode, in m; h is the embedding depth of the horizontal grounding electrode, in m; d is the diameter or equivalent diameter of the horizontal grounding electrode, in m; and A is the shape coefficient of the horizontal grounding electrode; is the utilization coefficient of the resistance reduction agent; Then according to the soil composition, the spacing, aperture and depth of the drill hole for installing the vertical ground electrode are determined, then the drill hole for installing the vertical ground electrode is positioned and drilled on the construction site, and the resistance R of a single vertical ground electrode is calculated z , and the calculation formula is: , wherein R z is the grounding resistance of the vertical ground electrode, in Ω; p is the soil resistivity or average soil resistivity, in Ω.m; is the total length of the vertical ground electrode, in m; d0 is the diameter or equivalent diameter of the vertical ground electrode, in m; Finally, the number of vertical grounding electrodes n is calculated by the following formula: where R is the ideal grounding resistance of the grounding grid, in Ω; R z is the grounding resistance of a single vertical grounding electrode, in Ω; n is the number of vertical grounding electrodes; R p is the grounding resistance of a horizontal grounding electrode, in Ω; and η is the utilization coefficient. S3: making a vertical grounding electrode by using a galvanized steel pipe, installing the vertical grounding electrode at the center position of the drill hole, and filling the drill hole and the galvanized steel pipe with a resistance reducing agent so that the resistance reducing agent is fully filled in the drill hole and the galvanized steel pipe; S4: making a horizontal grounding electrode by using a galvanized flat steel, wrapping the horizontal grounding electrode with a resistance reducing agent with a thickness of not less than 300 mm, installing the horizontal grounding electrode at the center position of the trench, and electrically welding the horizontal grounding electrode and the vertical grounding electrode in an equipotential manner; S5: electrically connecting the installed grounding grid, testing the resistance of the grounding grid, adding a vertical grounding electrode and electrically welding the vertical grounding electrode and the horizontal grounding electrode in an equipotential manner if the resistance does not meet the equipment requirement standard, and backfilling and tamping the grounding grid with clay with small resistivity after the resistance of the grounding grid meets the standard.

2. The grounding net construction method for a small area of high resistance value according to claim 1, characterized by: In step S2, mechanical drilling is adopted, the drilling interval is 5 m, and the drilling depth is 15 m.

3. The grounding net construction method for a small area of high resistance value according to claim 1, characterized by: In step S3, a through hole with a diameter of not less than Φ14 mm is formed in the peripheral wall of the galvanized steel pipe along the axial direction of the galvanized steel pipe, and the interval between the through holes is 1 m to 1.5 m.

4. The grounding net construction method for a small area of high resistance value according to Claim 1, wherein: In step S4, the horizontal grounding electrode and the vertical grounding electrode are electrically welded, and the welding is performed on not less than three sides, and the welded position is subjected to corrosion protection treatment.

5. The grounding net construction method for a small area of high resistance value according to Claim 1, wherein: In steps S3 and S4, the resistance reducing agent is a physical long-acting resistance reducing agent.