Grouping grounding system of modular transformer substation

Abstract

The grouping grounding system comprises a modularized prefabricated cabin body and an outdoor grounding grid arranged outside the prefabricated cabin body, and a screen cabinet, an isolation grouping lightning protection grounding box, a working grounding ring, a lightning protection grounding ring and a protection grounding ring are arranged in the prefabricated cabin body; the lightning protection grounding ring is connected with a total grounding terminal of the isolation grouping lightning protection grounding box, the working grounding ring and the protection grounding ring are respectively connected with a protection terminal of the isolation grouping lightning protection grounding box, each grounding copper bar in the screen cabinet is connected with a corresponding grounding ring child grounding wire in the prefabricated cabin body, and the lightning protection grounding ring is connected with an outdoor grounding grid. The prefabricated cabin body is connected with an outdoor grounding grid through grounding flat steel. According to the utility model, a grouping grounding technology is adopted, lightning stroke current is blocked by using the isolation suppressor, lightning pulses are prevented from invading equipment in the prefabricated cabin through counterattack of protection grounding and working grounding, and construction of a large-scale grounding grid can be reduced.

Description

Technical Field

[0001] This utility model relates to lightning protection and grounding technology for substations, specifically to a group grounding system for a modular substation. Background Technology

[0002] To achieve lightning protection, the power and electronic equipment in substations typically need to be grounded, mainly including functional grounding, protective grounding, and lightning protection grounding. Current technology primarily employs a combined grounding system, which involves constructing a large-area underground grounding grid using metallic materials, connecting the functional grounding wire, protective grounding wire, and lightning protection grounding wire to the same grid. In this combined grounding system, to reduce the impact of surge current on the functional and protective grounding, the resistance of the grounding grid needs to be reduced. This often involves using resistance-reducing agents with excessive levels of heavy metals, causing severe heavy metal pollution to the land.

[0003] Isolated group grounding technology uses electronic equipment instead of grounding grids, eliminating the need for steel and resistance-reducing agents. The isolated group grounding equipment incorporates a high-frequency suppressor with high impedance, which can suppress and block lightning current from entering the protected system through the "working ground" and "protective ground." It is particularly suitable for use in modular prefabricated substations. Installing the isolated group grounding equipment within a prefabricated cabin reduces the need for grounding grid construction and avoids soil pollution. Utility Model Content

[0004] This utility model discloses a group grounding system for a modular substation, designed for lightning protection grounding of the secondary prefabricated compartment of the substation. It can effectively achieve isolation between the lightning protection grounding network and the working grounding network and protective grounding network of secondary equipment, preventing damage to secondary equipment caused by lightning backflash.

[0005] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0006] A modular substation group grounding system includes a prefabricated enclosure and an outdoor grounding grid deployed outside the prefabricated enclosure. The interior of the prefabricated enclosure houses a cabinet, an isolated group lightning protection grounding box, a working grounding ring, a lightning protection grounding ring, and a protective grounding ring. The working grounding ring is fixed to the prefabricated enclosure by supporting insulators. Both the protective grounding ring and the lightning protection grounding ring are connected to the prefabricated enclosure using L-shaped connectors. The main grounding terminal of the isolated group lightning protection grounding box is connected to the lightning protection grounding ring by a copper cable, and the working grounding terminal of the isolated group lightning protection grounding box is connected to the working grounding ring by a copper cable. The protective grounding terminal of the isolated group lightning protection grounding box is connected to the protective grounding ring with copper cable; each cabinet is equipped with an internal working grounding copper busbar, an internal protective grounding copper busbar, and an internal lightning protection grounding copper busbar. The internal working grounding copper busbar in each cabinet is connected to the working grounding ring with a grounding wire, the internal protective grounding copper busbar in each cabinet is connected to the protective grounding ring with a grounding wire, and the internal lightning protection grounding copper busbar in each cabinet is connected to the lightning protection grounding ring with a grounding wire; the lightning protection grounding ring is connected to the outdoor grounding grid through copper cable, and the prefabricated cabin is connected to the outdoor grounding grid using grounding flat steel.

[0007] Furthermore, multiple sections of grounding copper busbars are laid inside the cable layer below the cabinet in the prefabricated cabin. Adjacent grounding copper busbars are pressed together vertically and fixed with connectors. All grounding copper busbars are connected in sequence to form a rectangular closed-loop structure, which is the working grounding ring. Inside the cable layer below the cabinet in the prefabricated cabin, multiple sections of hot-dip galvanized flat steel are laid in two rings, inner and outer. Adjacent flat steel in each ring is pressed together vertically and fixed with connectors. All flat steel in each ring is connected in sequence to form a rectangular closed-loop structure. The two rectangular closed-loop structures formed by the flat steel are the protective grounding ring and the lightning protection grounding ring, respectively.

[0008] Furthermore, the connector uses hot-dip galvanized bolts, and there are no fewer than two hot-dip galvanized bolts at the same end of adjacent grounding copper busbars, with a pressing surface length ≥ 50 mm and a bend radius ≥ 25 mm formed by the grounding copper busbar.

[0009] Furthermore, the connector uses hot-dip galvanized bolts, and there are no fewer than two hot-dip galvanized bolts at the same end of adjacent flat steels, with a minimum turning radius of the flat steel ≥ 60mm.

[0010] Furthermore, the withstand voltage level of the supporting insulator is not less than 2kV.

[0011] Furthermore, the prefabricated cabin body has no fewer than two connection points with the outdoor grounding grid.

[0012] Furthermore, the electrical characteristics of the isolated group lightning protection grounding box meet the following conditions: maximum isolation voltage is 20kV; withstand fault current ≥50A; withstand power frequency impulse current ≥5kA; high frequency impedance characteristics are 1kHz~100kHz.

[0013] Furthermore, the working grounding ring is connected to the lightning protection grounding ring via an isolation group lightning protection grounding box using a grounding soft copper wire, and the protective grounding ring is connected to the lightning protection grounding ring via an isolation group lightning protection grounding box using a grounding soft copper wire.

[0014] Furthermore, the diameter of the grounding soft copper wire is 100mm. 2 .

[0015] Furthermore, the grounding wires connecting the grounding copper busbars within each panel of the cabinet to the grounding rings within the prefabricated compartment are made of copper wire, and the cross-sectional area of ​​the grounding wires is not less than 50 mm². 2 .

[0016] This invention employs group grounding technology, setting up annular working grounding rings, protective grounding rings, and lightning protection grounding rings within the prefabricated cabin. The working grounding rings and protective grounding rings are connected to an isolation group lightning protection grounding box. The isolation suppressor within the isolation group lightning protection grounding box is used to block lightning current, preventing lightning pulses from backflashing into the equipment within the prefabricated cabin via protective grounding and working grounding. This efficiently achieves isolation between the lightning protection grounding network and secondary equipment, reducing the need for large-scale grounding network construction. Attached Figure Description

[0017] Figure 1 This is a schematic diagram showing the connection of the grounding guide ring in the prefabricated compartment in the embodiment;

[0018] Figure 2 Layout diagram of the grouped lightning protection and grounding system inside the prefabricated cabin;

[0019] Figure 3 This is a schematic diagram of the grounding connection method for the prefabricated cabin's internal cabinet.

[0020] Explanation of icon numbers:

[0021] 1. Lightning protection grounding ring; 2. Protective grounding ring; 3. Working grounding ring; 4. Isolation group lightning protection grounding box; 5. Prefabricated cabin; 6. Outdoor grounding grid; 7. Working grounding copper busbar inside the cabinet; 8. Protective grounding copper busbar inside the cabinet; 9. Lightning protection grounding copper busbar inside the cabinet; 10. Working grounding copper busbar of the cable layer; 11. Protective grounding copper busbar of the cable layer; 12. Lightning protection grounding copper busbar of the cable layer. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention.

[0023] This embodiment discloses a grouped grounding system for a modular substation. The modular substation is arranged using prefabricated container-style modules. An outdoor grounding grid 6 is constructed underground in the substation. Multiple cabinets are installed in each prefabricated module, and various equipment is installed inside the cabinets. The lightning protection of the secondary equipment in the cabinets adopts a grouped lightning protection grounding technology scheme, which is described below in conjunction with... Figures 1 to 3 Please provide a detailed explanation.

[0024] Figure 1 The lightning protection grounding system inside a single prefabricated cabin 5 is shown. It mainly includes three grounding rings and an isolation group lightning protection grounding box 4. The three U-shaped grounding rings are the working grounding ring 3, the lightning protection grounding ring 1, and the protective grounding ring 2. The isolation group lightning protection grounding box 4 contains an isolation suppressor and has a main grounding terminal, a working grounding terminal, and a protective grounding terminal. The main grounding terminal of the isolation group lightning protection grounding box 4 is connected to the lightning protection grounding ring 1 using a 100mm diameter... 2 The copper cables are connected by bolt crimping; the working grounding terminal of the isolation group lightning protection grounding box 4 is connected to the working grounding ring 3 with a diameter of 100mm. 2 The copper cables are connected by bolt crimping; the protective grounding terminal of the isolation group lightning protection grounding box 4 is connected to the protective grounding ring 2 with a diameter of 100mm. 2 The copper cables are connected by bolt crimping.

[0025] The grounding ring 3 is formed as follows: Multiple sections of grounding copper busbars are laid inside the cable layer below the cabinet within the prefabricated cabin 5. The grounding copper busbars are laid according to the direction of the cabinet layout, with a laying area of ​​100mm². 2 Arrange these grounding copper busbars into a rectangular closed-loop structure, pressing adjacent grounding copper busbars together vertically and fixing them with connectors. The length of the overlapping pressing surface at the connection of the grounding copper busbars should be ≥50mm, and the connection should be fixed with no less than two M8 hot-dip galvanized bolts. The radius of the bend formed by the grounding copper busbars should be ≥25mm. The working grounding ring 3 is fixed to the prefabricated cabin 5 by a supporting insulator, and the withstand voltage level of the supporting insulator should be no less than 2kV. There should only be one connection point between the working grounding ring 3 and the protective grounding ring 2 and the lightning protection grounding ring 1, and the connection point should preferably be located at the cable entry point. To ensure reliable connection, the working grounding ring 3 should use at least four wires with a cross-sectional area of ​​no less than 50mm². 2 The copper strips (cables) are connected to the protective grounding ring 2 and the lightning protection grounding ring 1 inside the cabin at a single point. A clear secondary grounding mark must be set at the connection point.

[0026] The protective grounding ring 2 is formed as follows: Multiple 60mm × 6mm hot-dip galvanized flat steel sections are laid inside the cable layer below the cabinet within the prefabricated cabin 5, arranged according to the cabinet's layout direction. These flat steel sections are arranged into a rectangular closed-loop structure, with adjacent sections pressed together and fixed with connectors. The joints of the flat steel sections are pressed together with no fewer than two M12 hot-dip galvanized bolts, and the minimum turning radius of the flat steel is ≥60mm. The protective grounding ring 2 is connected to the base frame of the prefabricated cabin 5 using L-shaped connectors. One end of the L-shaped connector is welded to the base frame, and the other end is connected to the flat steel section with no fewer than two M12 hot-dip galvanized bolts. The distance between two adjacent connectors is no greater than 5m, and the connectors are made of hot-dip galvanized material.

[0027] The lightning protection grounding ring 1 is set up in the same way as the protective grounding ring 2. Please refer to the above description of the protective grounding ring 2. It will not be repeated here.

[0028] The isolation group lightning protection grounding box 4 has an isolation suppressor installed inside. Its internal structure is existing technology and will not be described in detail. When selecting the model of the isolation group lightning protection grounding box 4, the following requirements should be met:

[0029] (1) The maximum withstand fault current should be selected based on the actual transformer capacity of the engineering substation; the maximum withstand fault current is calculated and selected according to the following formula:

[0030]

[0031] I d ≥I2%

[0032] In the above formula: I2 is the three-phase short-circuit current on the low-voltage side of the station service transformer; S N U represents the rated capacity of the station service transformer. 2N U is the rated voltage of the low-voltage side of the station service transformer. d % represents the short-circuit impedance voltage of the station service transformer; I d The maximum withstand fault current is selected based on the low-voltage side short-circuit current. It is worth noting that the withstand power frequency impulse current value should be greater than the low-voltage side short-circuit current value.

[0033] (2) The electrical characteristics shall meet the following requirements:

[0034] a. Maximum isolation voltage: 20kV;

[0035] b. Fault current withstand capability: ≥50A;

[0036] c. Withstands power frequency inrush current: ≥5kA;

[0037] d. High-frequency impedance characteristics: 1kHz~100kHz;

[0038] e. Equipment fault self-test: dry contact signal.

[0039] The grounding system of the internal cabinet of prefabricated cabin 5 is set as follows: Figure 3 As shown, each cabinet is equipped with an internal working grounding copper busbar 7, an internal protective grounding copper busbar 8, and an internal lightning protection grounding copper busbar 9. The internal working grounding copper busbar 7 in each cabinet is connected to the working grounding copper busbar 10 of the cable layer using a copper grounding wire. The internal protective grounding copper busbar 8 in each cabinet is connected to the protective grounding copper busbar 11 of the cable layer using a copper grounding wire. The internal lightning protection grounding copper busbar 9 in each cabinet is connected to the lightning protection grounding copper busbar 12 of the cable layer using a copper grounding wire. The cross-sectional area of ​​the copper grounding wires used is not less than 50 mm². 2 The lightning protection grounding copper busbar 9 and the working grounding copper busbar 7 inside the screen should be fixed by post insulators.

[0040] The working grounding ring 3 inside the prefabricated cabin 5 is connected to the lightning protection grounding ring 1 via an isolation group lightning protection grounding box 4 with a diameter of 100mm. 2 The grounding wire is used for connection. The protective grounding ring 2 inside the prefabricated cabin 5 is connected to the lightning protection grounding ring 1 via the isolation group lightning protection grounding box 4 using a 100mm diameter wire. 2 Connect the grounding soft copper wire. Connect the lightning protection grounding ring 1 to the outdoor grounding grid 6 via two grounding copper cables, welding them together at two different locations. Connect the prefabricated cabin 5 to the outdoor grounding grid 6 using grounding flat steel; there should be no fewer than two connection points between the prefabricated cabin 5 and the outdoor grounding grid 6. The copper busbars in the secondary cable trench (trough) must be welded to the outdoor grounding grid 6 at the cable entry point of the prefabricated cabin 5.

[0041] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A modular substation group grounding system, characterized in that: The system includes a prefabricated cabin and an outdoor grounding grid installed outside the prefabricated cabin. Inside the prefabricated cabin, there are cabinets, isolated group lightning protection grounding boxes, working grounding rings, lightning protection grounding rings, and protective grounding rings. The working grounding rings are fixed to the prefabricated cabin via supporting insulators. Both the protective grounding rings and lightning protection grounding rings are connected to the prefabricated cabin using L-shaped connectors. The main grounding terminal of the isolated group lightning protection grounding box is connected to the lightning protection grounding ring with a copper cable, and the working grounding terminal of the isolated group lightning protection grounding box is connected to the working grounding ring with a copper cable. The protective grounding terminal of the grounding box is connected to the protective grounding ring with copper cable; each cabinet is equipped with an internal working grounding copper busbar, an internal protective grounding copper busbar, and an internal lightning protection grounding copper busbar. The internal working grounding copper busbar in each cabinet is connected to the working grounding ring with a grounding wire, the internal protective grounding copper busbar in each cabinet is connected to the protective grounding ring with a grounding wire, and the internal lightning protection grounding copper busbar in each cabinet is connected to the lightning protection grounding ring with a grounding wire; the lightning protection grounding ring is connected to the outdoor grounding grid through copper cable, and the prefabricated cabin body is connected to the outdoor grounding grid using grounding flat steel.

2. The group grounding system of a modular substation according to claim 1, characterized in that: The prefabricated cabin contains multiple sections of grounding copper busbars within the cable layer below the cabinet. Adjacent grounding copper busbars are pressed together vertically and fixed with connectors. All grounding copper busbars are connected sequentially to form a rectangular closed-loop structure, which is the working grounding ring. The prefabricated cabin also contains multiple sections of hot-dip galvanized flat steel within the cable layer below the cabinet, in inner and outer rings. Adjacent flat steel in each ring is pressed together vertically and fixed with connectors. All flat steel in each ring is connected sequentially to form a rectangular closed-loop structure. The two rectangular closed-loop structures formed by the flat steel are the protective grounding ring and the lightning protection grounding ring, respectively.

3. The group grounding system of a modular substation according to claim 2, characterized in that: The connector uses hot-dip galvanized bolts. There are no fewer than two hot-dip galvanized bolts at the same end of adjacent grounding copper busbars. The length of the pressing surface is ≥50mm, and the radius of the bend formed by the grounding copper busbar is ≥25mm.

4. The group grounding system of a modular substation according to claim 2, characterized in that: The connectors use hot-dip galvanized bolts, and there are no fewer than two hot-dip galvanized bolts at the same end of adjacent flat steels. The minimum turning radius of the flat steel is ≥60mm.

5. The group grounding system of a modular substation according to claim 1, characterized in that: The withstand voltage level of the supporting insulator is not less than 2kV.

6. The group grounding system of a modular substation according to claim 1, characterized in that: The prefabricated cabin body has no fewer than two connection points with the outdoor grounding grid.

7. The group grounding system of a modular substation according to claim 1, characterized in that: The electrical characteristics of the isolation group lightning protection grounding box meet the following conditions: maximum isolation voltage is 20kV; withstand fault current ≥50A; withstand power frequency impulse current ≥5kA; high frequency impedance characteristics are 1kHz~100kHz.

8. The group grounding system of a modular substation according to claim 1, characterized in that: The working grounding ring is connected to the lightning protection grounding ring via an isolation group lightning protection grounding box using a grounding soft copper wire, and the protective grounding ring is connected to the lightning protection grounding ring via an isolation group lightning protection grounding box using a grounding soft copper wire.

9. A modular substation group grounding system according to claim 8, characterized in that: The diameter of the grounding soft copper wire is 100mm. 2 .

10. A modular substation group grounding system according to claim 1, characterized in that: The grounding wires connecting the internal grounding copper busbars of each panel within the cabinet to the grounding rings within the prefabricated compartment are made of copper wire, and the cross-sectional area of ​​the grounding wire is not less than 50 mm². 2 .

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