Mine grounding system and construction method

Abstract

The present invention discloses a mine grounding system and construction method, which is not only applicable to open-pit mines, but also suitable for underground mines. In combination with the distribution of mining sections or underground tunnels in the mining area, holes are drilled and washed in soil-free geological conditions at a relatively central position near the mining area, and conductive powder is poured into the hole under pressure to penetrate into the rock mass through the rock gap, so that the rock mass and the earth form a larger good conductor, and then a metal conductor is inserted into the hole to lead out to the ground. Multiple grounding bodies are connected to each other to form an efficient, good and reliable grounding body. After forming a whole, it is connected to the non-charged shell of the electrical equipment through the grounding busbar, which plays a protective role for the electrical equipment; the system solves the problem that the grounding body cannot be installed on the mine working surface due to the lack of soil, the grounding resistance exceeds the standard and there are safety hazards, and the investment in laying the grounding network over a long distance is large. It has the characteristics of low installation cost, easy to form a reasonable layout in the mining area, simple, firm and reliable installation, and excellent grounding resistance value.

Description

Technical Field

[0001] The present invention relates to the field of mine operation electrical equipment, and in particular to a mine grounding system and a construction method. Background Art

[0002] In the power system, if leakage occurs due to insulation degradation or insulation breakdown of electrical equipment, it will cause the parts of the electrical equipment that should not be energized under normal circumstances to suddenly become energized, or the low-voltage parts will suddenly become high-voltage, which will cause serious accidents such as electric shock casualties or burning of electrical equipment. In order to prevent such accidents, relevant national departments stipulate that electrical equipment must be grounded in IT, TT or TN ways to form effective protection. According to GB16423-2006 Metal and Non-metal Mines Safety Regulations, GB50070-2009 Mine Power Design Specifications and other relevant national regulations, especially in mines, all electrical equipment must be grounded using IT grounding.

[0003] Many mines need to be operated underground, which not only involves many excavation sections, a large range and long corridors, but also many distribution and power supply equipment points. The air humidity is high underground, and factors such as dust and carbon deposition are not conducive to the safe operation of electrical equipment, and the possibility of inducing leakage of high-voltage and low-voltage electrical equipment is relatively high. Taking IT methods to prevent and protect is a necessary basic means to ensure the effective use of safe electricity. Therefore, the grounding network in a mining area alone can reach tens of thousands of meters or even more than 100,000 meters. The number of high-voltage and low-voltage cables, central substations, substations, distribution cabinets, distribution boxes and other electrical equipment equipped underground is huge. In order to ensure safe production, the grounding system investment is huge, which imposes a great economic burden on mining enterprises. Since the underground is mostly rock structure and there is no geological condition of soil, firstly, it is difficult to install the grounding body; secondly, it is difficult to meet the standard requirements for the grounding resistance after the grounding body is installed. Some mining areas have main and auxiliary water tanks underground. There are great safety risks in installing grounding electrodes in water tanks: first, the water level in the water tank will change. When it is insufficient or too low, the grounding resistance will increase greatly or the grounding will fail; second, when the insulation of high-voltage electrical equipment (cable) is broken down, the iron plate in the water tank transmits electricity to the earth through water, not dead grounding. At this time, the water in the water tank will be charged. If there are people working in or around the water tank at this time, the risk of electric shock is very high. If the protection device system has poor sensitivity or refuses to move, the risk of electric shock is even greater. Therefore, some mining areas install grounding electrodes on the ground and then introduce them underground. The long distance of introduction requires a large amount of steel, installation manpower and equipment, and the risk of damage and breakage is high. Due to the long distance of introduction, huge investments are made to set up grounding wires. After introduction, the grounding resistance will still exceed the standard. This phenomenon is a long-standing and difficult problem in the mining industry, especially in the underground mining industry. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a mine grounding system and a construction method. The system is suitable for open-pit mines, and the effect of installing a grounding system underground in mines is more obvious. It solves the problems of difficulty in installing grounding bodies in existing mines due to the lack of soil address conditions, difficulty in meeting the requirements of the grounding resistance of the grounding bodies, high installation costs, and the risk of electric shock. The system has the characteristics of low installation cost, reasonable layout, standardized installation, reliable power supply, excellent grounding resistance value, and eliminates the safety risks of leakage injury or damage to equipment.

[0005] To realize the above design, the technical solution adopted by the present invention is: a mine grounding system, including an underground tunnel, in which a plurality of grounding holes are opened; the grounding holes are opened beside the ditch and in the side ditch of the underground tunnel; a grounding body is arranged in the grounding hole.

[0006] Preferably, the grounding body includes a main grounding body and a local grounding body; the main grounding body is arranged in the central radiation area of ​​the mining area. Further, the main grounding body is composed of 3 to 15 grounding holes.

[0007] Preferably, the local grounding body is composed of 1 to 2 grounding holes; the local grounding body is arranged in the underground tunnel outside the central radiation zone according to actual construction needs.

[0008] Preferably, the number of central radiation zones is not less than one; the underground tunnels are divided into multiple areas according to specific construction requirements and the distribution of electrical equipment, and each area is provided with a central radiation zone; the total length of the path from the central radiation zone to the electrical equipment in each area is the shortest.

[0009] Preferably, the diameter of the grounding hole is 76 mm to 91 mm; the hole spacing between the multiple grounding holes of the grounding body is 3 m to 6 m, and the hole depth is 5 m to 15 m.

[0010] Preferably, the grounding body includes a conductive layer composed of a conductive medium buried in the grounding hole, and a conductor passing through the conductive layer.

[0011] Furthermore, the conductor is made of metal materials such as galvanized flat iron or galvanized angle steel.

[0012] Preferably, the bottom of the conductor contacts and cooperates with the bottom of the grounding hole; the top of the conductor is higher than the upper surface of the grounding hole, and the length of the higher part is greater than 50 cm; and the multiple conductors are connected to the electrical equipment through the connecting wires.

[0013] Preferably, the construction method of the mine grounding system as described above comprises the following steps:

[0014] S1, drilling: First, the main grounding body is constructed: drilling holes in the side ditch of the underground tunnel in the selected central radiation area, 3 to 5 holes are drilled as a group, and a group of grounding holes is drilled first, and each grounding hole is numbered, and the water gushing, water loss, leakage, hole collapse, block drop, drill jam, fault structure, karst development, and lithology changes during the drilling process are recorded; the hole position deviation shall not be greater than 0.5m. When the hole section encounters large-scale faults, karst and other geological defects, the hole position shall be readjusted; anti-inclination measures are taken during the drilling process, and the inclination deviation from the hole mouth to the hole bottom is less than 0.5m;

[0015] S2, flushing: After drilling a group of grounding holes, flush the residual rock powder in the grounding holes with external clean water. After the flushing return water is clear, continue flushing for 10 minutes. After the flushing is completed, measure and record the hole depth, and the thickness of the residue at the bottom of the hole is not more than 15 cm. Then use 0.9MPa~1.2MPa high-pressure water to flush the cracks around the inner wall of the grounding hole in a pulsating manner, and the time interval between high and low pressure pulsations is 5min~10min. After the flushing return water is clear, continue flushing for no less than 10min, and the total flushing time is no less than 20min. After the flushing is completed, use a cover plate to close the hole before the next process.

[0016] S3, after flushing is completed, a water pressure test is carried out: 1.0 MPa~2.0 MPa of pressure water is introduced into the grounding hole, and the water pressure of the pressure water is linearly proportional to the hole depth of the grounding hole; after water is introduced, the pressure flow rate is measured every 5 minutes, and the four most recent consecutive readings are taken for record; when the difference between the maximum and minimum values ​​of the four readings is less than 10% of the final value, or the difference between the maximum and minimum values ​​is less than 1L / min, the water pressure test is terminated, and the flow value reading Q at this time is taken as the final value to calculate the rock mass fracture ratio q;

[0017] S4, pouring conductive slurry: Use internal and external pipe plugs, circulation in the hole, and continuous drilling and pouring from top to bottom or from bottom to top to pour conductive slurry into the grounding hole, with a pouring pressure of 0.5Mpa~4Mpa; grouting is performed in sections at different heights in the grounding hole, and the grouting pressure gradually increases from bottom to top; when the grouting pressure of each section is stable, it indicates that the section has been filled. After filling, the pressure is maintained to stabilize the grouting for no less than 5 minutes, so that the conductive slurry fully penetrates and fills the cracks around the grounding hole, forming a tree root-like conductive layer radiating from the hole to the surrounding area;

[0018] S5, after the grouting is completed, the conductor is inserted into the bottom of the grounding hole, and the tops of multiple conductors are connected to each other through insulated cables; the grounding resistance of a group of grounding bodies that have been constructed is tested by a resistance tester. According to the test results, a second group of grounding holes can be added and the hole depth of the second group of grounding holes can be adjusted. S1 to S5 are repeated until the grounding resistance test results meet the requirements;

[0019] S6, use grounding wires to connect electrical equipment in the mining area to the main grounding electrode after construction is completed; for electrical equipment that is far away, arrange local grounding electrodes nearby and connect the electrical equipment to the local grounding electrodes through grounding wires; the number of grounding holes of the local grounding electrodes is 1~2, and the rest of the construction methods are the same as those of the main grounding electrodes.

[0020] Furthermore, the conductive powder slurry is a liquid obtained by stirring and mixing conductive powder or resistance reducing agent with a particle size less than 80 μm with clean water; the conductive powder slurry includes solutions with concentrations set to 1:10, 1:6, 1:4, 1:3, 1:2, 1:1, 1:0.8, and 1:0.6, and the grouting is performed in a dilute to concentrated manner.

[0021] Furthermore, after the conductor is inserted into the grounding hole in step S5, the opening of the grounding hole is sealed to prevent the conductive powder from being carried away by the running water.

[0022] The beneficial effects of the present invention are:

[0023] 1. By opening a grounding hole on the rock in the side ditch of the underground tunnel, pressurized conductive slurry is poured into the hole, so that the conductive slurry can fully penetrate and pour into the grounding hole and the surrounding rock cracks. By utilizing the conductive layer formed by the conductive slurry and the humid environment in the side ditch, a grounding body is created in the underground tunnel without soil, thus solving the problem of difficulty in installing the grounding body.

[0024] 2. Conductors are buried inside the conductive layer, and the top of the conductors is connected to the electrical equipment through a grounding wire, so that the electrical equipment can be directly connected to the earth through the conductor, avoiding the indirect connection between the electrical equipment and the earth through the water tank when grounding is performed through a water tank, etc., which will cause changes in grounding resistance due to changes in water level, as well as safety hazards caused by the electrification of the water tank.

[0025] 3. The grounding body is composed of multiple grounding holes and internal landfills. The construction is carried out in groups. The grounding resistance test is carried out after each group of construction. The number and depth of the grounding holes are adjusted according to the test values, and the grounding resistance of the grounding body can be adjusted more finely.

[0026] 4. By analyzing the number and distribution of electrical equipment in the mining area to install the main grounding electrode, the grounding network cable connecting the electrical equipment in the area to the grounding electrode can be used with the least consumables, and it can also ensure that the resistance value will not exceed the standard due to the long distance of the grounding network; it can also make the underground grounding bus, grounding trunk line, grounding branch line and local grounding layers clear, forming a grounding system with a reasonable layout, standardized installation and reliable grounding; for a small number of electrical equipment that are far away and in remote locations, the local grounding electrode can be installed by the same construction method, which is very convenient; compared with the existing common method of installing the grounding electrode on the ground and then leading it to the underground over an ultra-long distance, the grounding system of this patent is greatly reduced in cost and effectively guarantees excellent grounding resistance. The grounding network cable is easily damaged and broken if the introduction distance is too long. The layout of this system is reasonable and the distance is short, and the cost and difficulty of maintenance and replacement will also be greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0028] Figure 1 It is a schematic diagram of the external structure of the main grounding body in the present invention.

[0029] Figure 2 It is a schematic diagram of the main cross section of the main grounding body in the present invention.

[0030] Figure 3 It is a top view schematic diagram of the main grounding body in the present invention.

[0031] Figure 4 This is a distribution diagram of the grounding network cables in the underground tunnel of the present invention.

[0032] Figure 5 It is a schematic diagram of the connection between the electrical equipment and the grounding body in the underground tunnel of the present invention.

[0033] The reference numerals in the figure are: underground tunnel 1, grounding hole 11, main grounding body 21, local grounding body 22, central radiation area 3, conductive layer 4, conductor 5, electrical equipment 6, and grounding busbar 7. DETAILED DESCRIPTION

[0034] like Figure 1~Figure 3 A mine grounding system includes an underground tunnel, in which a plurality of grounding holes are opened; the grounding holes are opened beside a ditch and in a side ditch of the underground tunnel; and a grounding body is arranged in the grounding hole.

[0035] In a preferred solution, the grounding body includes a main grounding body and a local grounding body; the main grounding body is arranged in the central radiation zone of the mining area, and the main grounding body consists of 3 to 15 grounding holes.

[0036] In the preferred solution, the local grounding body is composed of 1 to 2 grounding holes; the local grounding body is arranged in the underground tunnel outside the central radiation zone according to actual construction needs.

[0037] In the preferred scheme, the number of central radiation zones is not less than one; the underground tunnels are divided into multiple areas according to specific construction requirements and the distribution of electrical equipment, and each area is equipped with a central radiation zone; the total length of the path from the central radiation zone to the electrical equipment in each area is the shortest.

[0038] In a preferred solution, the diameter of the grounding hole is 76 mm to 91 mm; the hole spacing between the multiple grounding holes of the grounding body is 3 m to 6 m, and the hole depth is 5 m to 15 m.

[0039] In a preferred solution, the grounding body includes a conductive layer composed of a conductive medium buried in the grounding hole, and a conductor passing through the conductive layer.

[0040] In a preferred solution, the conductor is made of metal materials such as galvanized flat iron or galvanized angle steel.

[0041] In a preferred embodiment, the bottom of the conductor contacts and cooperates with the bottom of the grounding hole; the top of the conductor is higher than the upper surface of the grounding hole, and the length of the higher part is greater than 50 cm; and multiple conductors are connected to electrical equipment through connecting wires.

[0042] In a preferred embodiment, the construction method of the mine grounding system as described above comprises the following steps:

[0043] S1, drilling: First, the main grounding body is constructed: drilling holes in the side ditch of the underground tunnel in the selected central radiation area, 3 to 5 holes are drilled as a group, and a group of grounding holes is drilled first, and each grounding hole is numbered, and the water gushing, water loss, leakage, hole collapse, block drop, drill jam, fault structure, karst development, and lithology changes during the drilling process are recorded; the hole position deviation shall not be greater than 0.5m. When the hole section encounters large-scale faults, karst and other geological defects, the hole position shall be readjusted; anti-inclination measures are taken during the drilling process, and the inclination deviation from the hole mouth to the hole bottom is less than 0.5m;

[0044] S2, flushing: After drilling a group of grounding holes, flush the residual rock powder in the grounding holes with external clean water. After the flushing return water is clear, continue flushing for 10 minutes. After the flushing is completed, measure and record the hole depth, and the thickness of the residue at the bottom of the hole is not more than 15 cm. Then use 0.9MPa~1.2MPa high-pressure water to flush the cracks around the inner wall of the grounding hole in a pulsating manner, and the time interval between high and low pressure pulsations is 5min~10min. After the flushing return water is clear, continue flushing for no less than 10min, and the total flushing time is no less than 20min. After the flushing is completed, use a cover plate to close the hole before the next process.

[0045] S3, after flushing is completed, a water pressure test is carried out: 1.0 MPa~2.0 MPa of pressure water is introduced into the grounding hole, and the water pressure of the pressure water is linearly proportional to the hole depth of the grounding hole; after water is introduced, the pressure flow rate is measured every 5 minutes, and the four most recent consecutive readings are taken for record; when the difference between the maximum and minimum values ​​of the four readings is less than 10% of the final value, or the difference between the maximum and minimum values ​​is less than 1L / min, the water pressure test is terminated, and the flow value reading Q at this time is taken as the final value to calculate the rock mass fracture ratio q;

[0046] S4, pouring conductive slurry: Use internal and external pipe plugs, circulation in the hole, and continuous drilling and pouring from top to bottom or from bottom to top to pour conductive slurry into the grounding hole, with a pouring pressure of 0.5Mpa~4Mpa; grouting is performed in sections at different heights in the grounding hole, and the grouting pressure gradually increases from bottom to top; when the grouting pressure of each section is stable, it indicates that the section has been filled. After filling, the pressure is maintained to stabilize the grouting for no less than 5 minutes, so that the conductive slurry fully penetrates and fills the cracks around the grounding hole, forming a tree root-like conductive layer radiating from the hole to the surrounding area;

[0047] S5, after the grouting is completed, the conductor is inserted into the bottom of the grounding hole, and the tops of multiple conductors are connected to each other through insulated cables; the grounding resistance of a group of grounding bodies that have been constructed is tested by a resistance tester. According to the test results, a second group of grounding holes can be added and the hole depth of the second group of grounding holes can be adjusted. S1 to S5 are repeated until the grounding resistance test results meet the requirements;

[0048] S6, use grounding wires to connect electrical equipment in the mining area to the main grounding electrode after construction is completed; for electrical equipment that is far away, arrange local grounding electrodes nearby and connect the electrical equipment to the local grounding electrodes through grounding wires; the number of grounding holes of the local grounding electrodes is 1~2, and the rest of the construction methods are the same as those of the main grounding electrodes.

[0049] In a preferred embodiment, the conductive powder slurry is a liquid obtained by stirring and mixing conductive powder or a resistance reducing agent with a particle size less than 80 μm with clean water; the conductive powder slurry includes solutions with concentrations set to 1:10, 1:6, 1:4, 1:3, 1:2, 1:1, 1:0.8, and 1:0.6, and the grouting is performed in a dilute to concentrated manner.

[0050] In a preferred solution, after the conductor is inserted into the grounding hole in step S5, the opening of the grounding hole is sealed to prevent the conductive powder from being carried away by the running water.

[0051] Embodiment 1:

[0052] like Figure 4~Figure 5A mine grounding system includes an underground tunnel, which is divided into four main areas according to the distribution of electrical equipment. A central radiation area is set in each area. The total length of the path from the central radiation area to the electrical equipment in each area is the shortest. A main grounding electrode is set in each central radiation area, with a total of four main grounding electrodes. Several local grounding electrodes are set in the remaining parts.

[0053] The main grounding body is composed of 3 to 15 grounding holes.

[0054] The local grounding body is composed of 1 to 2 grounding holes; the local grounding body is arranged in the underground tunnel outside the central radiation area according to actual construction needs.

[0055] In a preferred solution, the diameter of the grounding hole is 80 mm; the hole spacing between the multiple grounding holes of the grounding body is 4 m, and the hole depth is 12 m.

[0056] In a preferred solution, both the main grounding body and the local grounding body include a conductive layer composed of a conductive medium buried in the grounding hole, and a conductor passing through the conductive layer.

[0057] In a preferred solution, the conductor is made of galvanized angle steel.

[0058] In a preferred embodiment, the bottom of the conductor contacts and cooperates with the bottom of the grounding hole; the top of the conductor is 50 cm higher than the upper surface of the grounding hole; and the plurality of conductors are connected to the electrical equipment via connecting wires.

[0059] In a preferred embodiment, the construction method of the mine grounding system as described above comprises the following steps:

[0060] S1, drilling: First, the main grounding body is constructed: drilling holes in the side ditch of the underground tunnel in the selected central radiation area, 3 holes are drilled in a group, and each grounding hole is numbered. The water gushing, water loss, leakage, hole collapse, block drop, drill jam, fault structure, karst development, and lithology change during the drilling process are recorded; the hole position deviation shall not be greater than 0.5m. When the hole section encounters large-scale faults, karst and other geological defects, the hole position shall be readjusted; anti-inclination measures are taken during the drilling process, and the inclination deviation from the hole mouth to the hole bottom is less than 0.5m;

[0061] S2, flushing: After drilling a group of grounding holes, flush the residual rock powder in the grounding holes with external clean water. After the flushing return water is clear, continue flushing for 10 minutes. After the flushing is completed, measure and record the hole depth, and the thickness of the residue at the bottom of the hole is not more than 15 cm. Then use high-pressure water to flush the cracks around the inner wall of the grounding hole in a pulsating manner. The high and low pressure pulsation time interval is 5 minutes to 10 minutes. The low pressure is 0.9 MPa and the high pressure is 1.2 MPa. After the flushing return water is clear, continue flushing for 10 minutes, and the total flushing time is not less than 20 minutes. After the flushing is completed, the hole mouth is closed with a cover plate before the next process.

[0062] S3, after flushing is completed, a water pressure test is performed: 1.5MPa pressure water is passed into the grounding hole, and the pressure flow rate is measured every 5 minutes after the water is passed, and the four most recent consecutive readings are taken for record; when the difference between the maximum and minimum values ​​of the four readings is less than 10% of the final value, or the difference between the maximum and minimum values ​​is less than 1L / min, the water pressure test is terminated, and the flow value reading Q at this time is taken as the final value to calculate the rock mass fracture ratio q;

[0063] S4, pouring conductive slurry: Use internal and external pipe plugs, circulation in the hole, and continuous drilling and pouring from top to bottom or from bottom to top to pour conductive slurry into the grounding hole, with a pouring pressure of 0.5Mpa~4Mpa; grouting is performed in sections at different heights in the grounding hole, and the grouting pressure gradually increases from bottom to top; when the grouting pressure of each section is stable, it indicates that the section has been filled. After filling, the pressure is maintained to stabilize the grouting for no less than 5 minutes, so that the conductive slurry fully penetrates and fills the cracks around the grounding hole, forming a tree root-like conductive layer radiating from the hole to the surrounding area;

[0064] S5, after grouting is completed, the conductor is inserted into the bottom of the grounding hole, and the tops of multiple conductors are connected to each other through insulated cables; the grounding resistance of a group of grounding bodies that have been completed is tested by a resistance tester, and the resistance test shows that the resistance value exceeds the standard by 40%; according to the test results, 3 grounding holes of the second group are added, and the hole depth of the second group of grounding holes is adjusted to 14m, and then S1~S5 are repeated. When the resistance value meets the standard, the installation of the grounding body is completed;

[0065] S6, use grounding wires to connect electrical equipment in the mining area to the main grounding electrode after construction is completed; for electrical equipment that is far away, arrange local grounding electrodes nearby and connect the electrical equipment to the local grounding electrodes through grounding wires; the number of grounding holes in the local grounding electrode is 1, and the rest of the construction methods are the same as those of the main grounding electrode.

[0066] In a preferred embodiment, the conductive powder slurry is a liquid obtained by stirring and mixing conductive powder with a particle size of 70 μm with clean water; the conductive powder slurry includes solutions with concentrations set to 1:10, 1:6, 1:4, 1:3, 1:2, 1:1, 1:0.8, and 1:0.6, and the grouting is performed in a dilute to concentrated manner.

[0067] In a preferred solution, after the conductor is inserted into the grounding hole in step S5, the opening of the grounding hole is sealed with clay to prevent the conductive powder from being carried away by running water.

[0068] like Figure 5 As shown, several electrical equipment at the corners of the underground tunnel are far away from the main grounding electrode in the area, so a local grounding electrode is installed nearby. A grounding hole is opened in the local grounding electrode, and the hole depth is adjusted to 15m. After installation, the grounding resistance value is measured to meet the standard; the grounding busbar is connected to the electrical equipment through a grounding branch line (not shown in the figure).

[0069] The above-mentioned embodiments are only preferred technical solutions of the present invention and should not be regarded as limitations of the present invention. The embodiments and features in the embodiments of the present application can be arbitrarily combined with each other without conflict. The protection scope of the present invention shall be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A mine grounding system, comprising an underground tunnel (1), characterized in that: A plurality of grounding holes (11) are provided in an underground tunnel (1); the grounding holes (11) are provided beside a ditch and in a side ditch of the underground tunnel (1); a grounding body is provided in the grounding hole (11); the grounding body comprises a main grounding body (21) and a local grounding body (22); the main grounding body (21) is provided in a central radiation zone (3) of a mine area; the number of central radiation zones (3) is not less than one; the main grounding body (21) is composed of 3 to 15 grounding holes (11); the underground tunnel (1) is divided into a plurality of zones according to specific construction requirements and the distribution of electrical equipment, Each area is provided with a central radiation area (3); the total length of the path from the main grounding body (21) in the central radiation area (3) to the electrical equipment at each location in the area is the shortest; the grounding body comprises a conductive layer (4) composed of a conductive medium buried inside the grounding hole (11), and a conductor (5) passing through the conductive layer (4); the bottom of the conductor (5) is in contact with the bottom of the grounding hole (11); the top of the conductor (5) is higher than the upper surface of the grounding hole (11), and the length of the higher part is greater than 50 cm; and the plurality of conductors (5) are connected to the electrical equipment via connecting wires.

2. The mine grounding system according to claim 1, characterized in that: The local grounding body (22) is composed of one to two grounding holes (11); the local grounding body (22) is arranged in an underground tunnel (1) outside the central radiation zone (3) or in an underground electrical equipment chamber according to actual construction needs.

3. The mine grounding system according to claim 2, characterized in that: The diameter of the grounding hole (11) is 76 mm to 91 mm; the hole spacing between the multiple grounding holes (11) of the grounding body is 3 m to 6 m, and the hole depth is 5 m to 15 m.

4. The construction method of the mine grounding system according to claim 3 is characterized in that: It includes the following steps: S1, drilling: firstly, the main grounding body (21) is constructed: drilling is carried out in the side ditch of the underground tunnel (1) in the selected central radiation zone (3), 3 to 5 holes are drilled as a group, and a group of grounding holes (11) is first drilled, and each grounding hole (11) is numbered, and the water gushing, water loss, leakage, hole collapse, block drop, drill jam, fault structure, karst development, and lithology change during the drilling process are recorded; the hole position deviation shall not be greater than 0.5m, and when the hole section encounters large-scale faults, karst and other geological defects, the hole position shall be readjusted; anti-inclination measures are taken during the drilling process, and the inclination deviation from the hole mouth to the hole bottom is less than 0.5m; S2, flushing: After drilling a group of grounding holes (11), the residual rock powder in the grounding holes (11) is flushed openly with external clean water. After the flushing return water is clear, the flushing is continued for 10 minutes. After the flushing is completed, the hole depth is measured and recorded, and the thickness of the residue at the bottom of the hole is not more than 15 cm. Then, high-pressure water of 0.9 MPa to 1.2 MPa is used to pulsate the cracks around the inner wall of the grounding hole (11). The time interval between high and low pressure pulsations is 5 minutes to 10 minutes. After the flushing return water is clear, the flushing is continued for not less than 10 minutes, and the total flushing time is not less than 20 minutes. After flushing is completed, the orifice is closed with a cover plate before the next process; S3, after the flushing is completed, a water pressure test is performed: 1.0 MPa to 2.0 MPa of pressure water is introduced into the grounding hole (11), and the water pressure of the pressure water is linearly proportional to the hole depth of the grounding hole (11); after the water is introduced, the pressure flow rate is measured every 5 minutes, and the four most recent consecutive readings are taken for recording; when the difference between the maximum and minimum values ​​of the four readings is less than 10% of the final value, or the difference between the maximum and minimum values ​​is less than 1 L / min, the water pressure test is terminated, and the flow value reading Q at this time is taken as the final value to calculate the rock mass fracture ratio q; S4, pouring conductive slurry: using internal and external pipe plugs, circulating in the hole, and continuously drilling and pouring from top to bottom or from bottom to top to pour conductive slurry into the grounding hole (11), with a pouring pressure of 0.5Mpa~4Mpa; grouting is performed in sections at different heights in the grounding hole (11), with the grouting pressure gradually increasing from bottom to top; when the grouting pressure of each section is stable, it indicates that the section has been filled, and after filling, the pressure is maintained to stabilize the grouting for no less than 5 minutes, so that the conductive slurry fully penetrates and fills the cracks around the grounding hole (11), forming a tree root-like conductive layer (4) radiating from the hole to the surrounding area; S5, after the grouting is completed, the conductor (5) is inserted into the bottom of the grounding hole (11), and the tops of the multiple conductors (5) are connected to each other by galvanized flat iron; the grounding resistance of the completed group of grounding bodies is tested by a resistance tester, and according to the test results, a second group of grounding holes (11) can be added and the hole depth of the second group of grounding holes (11) can be adjusted, and S1 to S5 are repeated until the grounding resistance test result meets the requirements; S6, flat steel or round steel is used to form a grounding grid in the mining area, the starting point of the grounding grid is connected to the main grounding electrode (21) after construction, and the end point is connected to the casing of the electrical equipment; for electrical equipment that is far away, a local grounding electrode (22) is arranged nearby, and the casing of the electrical equipment is connected to the main grounding grid and the local grounding piles at the same time; the number of grounding holes (11) of the local grounding electrode (22) is 1 to 2, and the rest of the construction method is the same as the construction method of the main grounding electrode (21).

5. The construction method of the mine grounding system according to claim 4 is characterized in that: The conductive powder slurry is a liquid slurry obtained by stirring and mixing conductive powder or a resistance reducing agent with a particle size less than 80 μm with clean water.

6. The construction method of the mine grounding system according to claim 4, characterized in that: In the step S5, after the conductor (5) is inserted into the grounding hole (11), the opening of the grounding hole (11) is sealed to prevent the conductive powder from being carried away by the running water.

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