A dendritic DC grounding electrode for smart grids and its design method

Abstract

This invention belongs to the field of DC grounding electrode technology, and specifically relates to a tree-shaped DC grounding electrode for smart grids and its design method. The technical solution is as follows: A tree-shaped DC grounding electrode for smart grids includes an electrode comprising a straight electrode trunk, several straight electrode branches located near the trunk, and an annular end electrode located near the other end of each straight electrode branch, with each branch corresponding to an annular end electrode; it also includes a central device or grounding electrode line terminal tower. The electrode is divided into several segments, each segment connected to a feeder cable, which is connected to the central device or grounding electrode line terminal tower via a conductor. This invention provides a tree-shaped DC grounding electrode for smart grids and its design method, ensuring the current discharge effect of the electrode while avoiding problems such as the need for large-scale demolition due to the surrounding of numerous buildings caused by the annular electrode arrangement.

Description

Technical Field

[0001] This invention belongs to the field of DC grounding electrode technology, and specifically relates to a dendritic DC grounding electrode for smart grids and its design method. Background Technology

[0002] Currently, most of the DC grounding electrodes that have been built and put into operation in China adopt a horizontal, shallow-buried ring arrangement, such as circular or racetrack-shaped designs. This type of arrangement has advantages such as uniform current distribution and convenient construction and maintenance. However, it generally requires a large site area, relatively flat terrain, and a thick soil layer. In some mountainous, hilly, or even plain areas, due to the influence of the topography, geology, soil resistivity, or related facilities such as metal pipelines, railways, and buildings at the electrode site, available electrode sites may be extremely scarce. Furthermore, available electrode sites may not have the characteristics of a large site area and relatively flat terrain, making it unsuitable for a circular, elliptical, or racetrack-shaped ring arrangement, or resulting in poor technical and economic efficiency. Summary of the Invention

[0003] To address the aforementioned problems in existing technologies, the present invention aims to provide a dendritic DC grounding electrode for smart grids and its design method. The electrode is arranged in a strip shape according to the terrain and distribution of physical barriers such as buildings in the electrode site area. The electrode is placed in a strip-shaped area with relatively flat soil, thick soil layer and low soil resistivity. At the same time, it can flexibly avoid various physical barriers such as buildings, ensuring the current discharge effect of the electrode while avoiding various problems such as the need for large-scale demolition due to the large number of buildings being surrounded by the electrode in a ring arrangement.

[0004] The technical solution adopted in this invention is as follows:

[0005] A tree-shaped DC grounding electrode for smart grids includes an electrode comprising a straight electrode trunk, several straight electrode branches located near the straight electrode trunk, and an annular end electrode located near the other end of each straight electrode branch, with each straight electrode branch corresponding to an annular end electrode; it also includes a central device or grounding electrode line terminal tower. The electrode is divided into several segments, and each segment of the electrode is connected to a feeder cable, which is connected to the central device or grounding electrode line terminal tower via a conductor.

[0006] As a preferred embodiment of the present invention, the electrode material includes an active filling material and a plurality of feeding elements embedded in the active filling material, and the feeding cable is connected to the plurality of feeding elements in a segment of the electrode.

[0007] As a preferred embodiment of the present invention, the material of the power supply element is high silicon ferrochrome or high silicon cast iron, the power supply cable includes a power distribution cable and a number of lead cables built into the power supply element within a segment of the electrode, the power distribution cable is laid along with the electrode, the power distribution cable is connected to the lead wire, the power distribution cable is provided with a number of welding heads, and the number of lead cables are welded together to a welding head of the power distribution cable.

[0008] As a preferred embodiment of the present invention, the material of the power supply element is a steel rod, and the power supply cable includes several feeder cables that are built into the power supply elements within a segment of the electrode, and the feeder cables that are built into the power supply elements within a segment of the electrode are connected to a conductor.

[0009] As a preferred embodiment of the present invention, the guide lines are arranged by overhead or underground laying, and the central equipment or grounding electrode line terminal tower is connected to the busbar, and several guide lines are connected to the busbar.

[0010] A design method for a dendritic DC grounding electrode for a smart grid includes the following steps:

[0011] S1: Recommended pole site determination: Based on the distribution of obstacles including surrounding metal pipelines, railways, and substations, and taking into account the conditions of the pole site itself, a recommended pole site is determined;

[0012] S2: Recommended Polar Site Survey: Conduct surveys and data collection on recommended polar sites, including topographic mapping, topography, geological structure and seismic parameters, stratigraphy, groundwater level, adverse geological processes, mineral resources, shallow and deep soil resistivity, soil heat capacity and thermal conductivity, water conservancy projects, flood inundation, waterlogging, erosion, and soil temperature.

[0013] S3: Electrode arrangement scheme determined;

[0014] S4: Flow diversion system design;

[0015] S5: Auxiliary Facility Design: Based on the requirements of regulations and specifications and in combination with the actual situation of the project, specify the location, quantity and related requirements of auxiliary facilities including seepage wells, detection wells, diversion wells and marker posts;

[0016] S6: Impact of grounding electrode on surrounding facilities and protection design: Calculate and analyze the impact of the recommended electrode site on surrounding facilities including substations, power plants, converter stations, metal pipelines, and railways, and propose solutions for the affected facilities.

[0017] As a preferred embodiment of the present invention, step S3 includes the following specific steps:

[0018] S31: Based on the topography, landforms, and facility distribution of buildings in the electrode site area, select relatively flat strip areas with thick soil layers that are suitable for electrode placement.

[0019] S32: Estimate the required electrode length based on the system design conditions, and formulate all possible electrode arrangement schemes in conjunction with the selected strip regions;

[0020] S33: Perform simulation calculations on each electrode arrangement scheme to determine the relevant technical parameters of each scheme, including electrode burial depth, electrode material and size, and perform verification including step potential difference to confirm whether each arrangement scheme meets the technical requirements.

[0021] S34: By combining the engineering quantity and overflow density deviation coefficient, a comprehensive comparison of various layout schemes that meet the technical requirements is made to determine the recommended electrode layout scheme.

[0022] As a preferred embodiment of the present invention, in step S33, the step potential difference verification is performed according to the following formula:

[0023] ;

[0024] In the formula: U pm U is the maximum allowable step potential difference of the grounding electrode. pm =7.42+0.0318ρ s , ρ s U represents the equivalent resistivity of the surface soil in the polar region. max The maximum calculated value of the step potential difference under the designed electrode arrangement scheme;

[0025] The overflow density deviation coefficient is used as one of the indicators for evaluating the merits of various electrode arrangement schemes. The overflow density deviation coefficient k... er Defined as:

[0026] ;

[0027] In the formula: I d τ is the grounding current flowing into the ground electrode. av τ is the average overflow density; τ(l) is the overflow density at any point; L is the total length of the electrode.

[0028] As a preferred embodiment of the present invention, step S4 includes the following specific steps:

[0029] S41: Location of central equipment or grounding electrode line terminal tower: The central equipment should be located near the geometric center of the overall electrode as much as possible; when the conductor is overhead and no busbar is installed, the grounding electrode line terminal tower should be located near the geometric center of the overall electrode as much as possible.

[0030] S42: Determination of guide line scheme: Based on the electrode layout scheme and the site topography and features, determine whether the guide line will be an overhead line or a buried cable.

[0031] S43: Electrode segmentation scheme formulation: Segmentation is carried out according to the length and position of each straight electrode main trunk and straight electrode branch, and all possible segmentation schemes are formulated. The segmentation scheme is formulated with the goal of making the current in the conductor as uniform as possible.

[0032] S44: For each electrode segmentation scheme, determine the number, type, and cross-section of the power distribution cables and conductors, and clarify their laying path, laying method, and burial depth;

[0033] S45: By combining the engineering quantity and the uniformity coefficient of current distribution in the guide wire, a comprehensive comparison of various electrode segmentation schemes is conducted to determine the recommended electrode segmentation scheme and the guide system design scheme.

[0034] As a preferred embodiment of the present invention, in step S45, the uniformity coefficient σ of the current distribution in the conductor is defined as:

[0035] ;

[0036] In the formula: I i denoted as , where μ is the total current in the conductors of each segmented electrode under a given electrode segmentation scheme; μ is the average value of the total current in the conductors of each segmented electrode under a given electrode segmentation scheme; and n is the number of electrode segments.

[0037] The beneficial effects of this invention are as follows:

[0038] 1. The dendritic grounding electrode of the present invention can be arranged in a strip shape according to the terrain and distribution of physical barriers such as buildings in the electrode site area. The electrode is arranged in a strip area with relatively flat soil, thick soil layer and low soil resistivity. At the same time, it can flexibly avoid various physical barriers such as buildings, ensuring the current discharge effect of the electrode while avoiding various problems such as the need for large-scale demolition due to the large number of buildings being surrounded by the electrode ring arrangement. While meeting the engineering and technical conditions, it can reduce building demolition, engineering construction costs and construction coordination difficulties, and provides a new idea and reference for the design of unconventional DC grounding electrodes in the future.

[0039] 2. The grounding electrode design of this invention must meet various technical requirements such as current carrying capacity, temperature rise, corrosion, grounding resistance, step potential difference, contact potential difference, transfer potential, and surface current density to ensure that the grounding electrode operates safely and reliably under the corresponding system conditions and within its design life. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the structure of the present invention;

[0041] Figure 2This is a diagram showing the connection structure between the power supply cable and the power supply components;

[0042] Figure 3 This is a cross-sectional view of the electrodes of the feeder cable;

[0043] Figure 4 This is a diagram showing the connection structure between the power distribution cable and the conductor.

[0044] Figure 5 This is a flowchart of the method of the present invention;

[0045] Figure 6 This is a layout diagram of the double-ring circular electrode scheme;

[0046] Figure 7 This is a layout diagram of the double-ring racetrack-shaped electrode scheme;

[0047] Figure 8 This is a layout diagram of the electrode dendritic scheme;

[0048] Figure 9 This is a layout diagram of the electrode closed single-loop scheme;

[0049] Figure 10 This is the layout diagram of the single-ring electrode + line 2 scheme;

[0050] Figure 11 This is a layout diagram of the electrode split ring scheme;

[0051] Figure 12 This is a layout diagram of the electrode split ring + wire scheme;

[0052] Figure 13 This is the layout diagram of the single-ring electrode + line 1 scheme;

[0053] Figure 14 This is a layout diagram of the double-linear electrode scheme;

[0054] Figure 15 This is a schematic diagram of the optimal solution for dividing the electrode into 8 segments;

[0055] Figure 16 This is a schematic diagram of the optimal design for dividing the electrode into 9 segments;

[0056] Figure 17 This is a schematic diagram of the optimal scheme for dividing the electrode into 10 segments;

[0057] Figure 18 This is a schematic diagram of the optimal scheme for dividing the electrode into 11 segments;

[0058] Figure 19 This is a schematic diagram of the optimal scheme for dividing the electrode into 12 segments;

[0059] Figure 20 This is a schematic diagram of the grounding electrode current guiding system design scheme in the embodiment.

[0060] In the diagram: 1-Electrode; 2-Central equipment or grounding electrode line terminal tower; 3-Feeder cable; 4-Conductor line; 11-Active filler material; 12-Feeder element; 31-Distribution cable; 32-Drainage cable; 33-Welding head; 41-Busbar. Detailed Implementation

[0061] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0062] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the invention can be combined with each other.

[0063] like Figures 1-4 As shown, the smart grid uses a tree-shaped DC grounding electrode, which includes an electrode 1. The electrode 1 includes a main straight electrode 1, several branches of straight electrodes 1 set near the main straight electrode 1, and a ring-shaped end electrode set near the other end of the branches of straight electrodes 1. Each branch of straight electrodes corresponds to a ring-shaped end electrode. It also includes a central equipment or grounding electrode line terminal tower 2. The electrode 1 is divided into several segments, and each segment of the electrode 1 is connected to a feeder cable 3. The feeder cable 3 is connected to the central equipment or grounding electrode line terminal tower 2 through a conductor 4.

[0064] The electrode 1 is made of an active filling material 11 and a plurality of power feeding elements 12 embedded in the active filling material 11. The power feeding cable 3 is connected to a plurality of power feeding elements 12 in a segment of the electrode 1.

[0065] When the material of the power supply element 12 is high silicon ferrochrome or high silicon cast iron, the power supply cable 3 includes a power distribution cable 31 and several lead-in cables 32 that are built into the power supply element 12 within a segment of the electrode 1. The power distribution cable 31 is laid along with the electrode 1 and is connected to the guide wire 4. Several welding heads 33 are provided on the power distribution cable 31, and several lead-in cables 32 are welded together to one welding head 33 of the power distribution cable 31.

[0066] When the material of the power supply element 12 is a steel rod, there is no need to use the power distribution cable 31. The power supply cable 3 includes several feeder cables 32 that are built into the power supply elements 12 in a segment of the electrode 1. The feeder cables 32 built into the power supply elements 12 in a segment of the electrode 1 are connected to a conductor 4.

[0067] The guide line 4 is laid out in an overhead or underground manner. The central equipment or grounding electrode line terminal tower 2 is connected to the busbar 41, and several guide lines 4 are connected to the busbar 41.

[0068] To ensure the safe and reliable operation of grounding electrodes under corresponding system conditions and within their design lifespan, grounding electrode design must meet various technical requirements, including current carrying capacity, temperature rise, corrosion, grounding resistance, step potential difference, contact potential difference, transfer potential, and surface current density. Standards such as DL / T 5224-2014 "Technical Specification for Design of High Voltage Direct Current Transmission Earth Return System" have already discussed the relevant system and technical conditions for DC grounding electrode design in detail. This invention only provides a detailed discussion of the design method and process for dendritic grounding electrodes.

[0069] like Figure 5 As shown, the design method for a dendritic DC grounding electrode in a smart grid includes the following steps:

[0070] S1: Recommended pole site determination: Based on the distribution of surrounding obstacles such as metal pipelines, railways, and substations, and taking into account the conditions of the pole site itself, a recommended pole site is determined.

[0071] S2: Recommended Polar Site Survey: Conduct topographic mapping, topography and geomorphology, geological structure and seismic parameters, strata lithology, groundwater level, adverse geological processes, mineral resources, shallow and deep soil resistivity, soil heat capacity and thermal conductivity, water conservancy projects, flood inundation, waterlogging, erosion, soil temperature and other surveys and data collection for the recommended polar site.

[0072] S3: Electrode 1 arrangement scheme determined:

[0073] S31: Based on the topography, landforms, and distribution of buildings and other facilities in the electrode site area, select relatively flat strip areas with thick soil layers that can be used to arrange electrode 1.

[0074] S32: Estimate the required length of electrode 1 based on the design system conditions, and formulate all possible electrode 1 layout schemes in conjunction with the selected strip regions; in the process of formulating the electrode 1 layout scheme, the following points should be noted in order to obtain a relatively optimal scheme:

[0075] a) The electrode 1 should be extended as short as possible in all directions, and the entire electrode 1 should be arranged as "rounded" as possible to reduce the non-uniformity of the discharge density.

[0076] b) Electrode 1 should be arranged as symmetrically as possible to improve operating performance while taking into account the layout of the flow guiding system, thereby improving the balance and reliability of the flow guiding system.

[0077] c) When selecting the burial path for the straight electrode 1, the turning angle should be minimized as much as possible to avoid "large turning angles" and reduce the discharge density value at the turning angle;

[0078] d) At the end with the highest overflow density, a suitable "flow equalization ring" can be arranged according to the size of the site, such as a racetrack-shaped end electrode 1, to reduce the end effect;

[0079] S33: Perform simulation calculations on each electrode 1 arrangement scheme to determine the relevant technical parameters such as the burial depth, material, and size of electrode 1 for each scheme, and perform checks such as step potential difference to confirm whether each arrangement scheme meets the technical requirements; in particular, since the arrangement range of the electrode 1 of the dendritic grounding electrode may be wider than that of the ring grounding electrode, and the soil resistivity at different branch locations may vary greatly, it is advisable to use different soil models for simulation calculations at different locations to make the calculated values ​​such as current distribution more accurate;

[0080] S34: By comprehensively comparing and selecting various layout schemes that meet the technical requirements, taking into account factors such as the amount of work and the overflow density deviation coefficient, the recommended layout scheme for electrode 1 is determined.

[0081] S4: Flow diversion system design:

[0082] S41: Location of central equipment or grounding electrode line terminal tower 2: The central equipment should be located as close as possible to the geometric center of the overall electrode 1; when the current guiding system adopts an overhead method and does not set up a busbar 41, the grounding electrode line terminal tower should also be located as close as possible to the geometric center of the overall electrode 1, which is conducive to the layout of the current guiding system.

[0083] S42: Determination of the diversion system scheme: Based on the electrode 1 layout scheme, site topography and features, it is determined whether the diversion system will use overhead lines or buried cables;

[0084] S43: Electrode 1 segmentation scheme formulation: Segmentation is carried out according to the length and position of each branch electrode 1. All possible segmentation schemes are formulated. The segmentation scheme should aim to make the current in the guide wire as uniform as possible. The number of segments should not be too many to avoid making the guide system too complex.

[0085] S44: For each electrode 1 segmentation scheme, determine the number, type, cross-section, etc. of the power distribution cable 31 and the guide wire, and clarify its laying path, laying method, burial depth, etc.

[0086] S45: By comprehensively comparing and selecting various electrode 1 segment schemes based on factors such as engineering quantity and current distribution uniformity coefficient of the guide wire, the recommended electrode 1 segment scheme and the guide system design scheme are determined.

[0087] S5: Auxiliary Facility Design: Based on the requirements of regulations and specifications and in combination with the actual situation of the project, clarify the location, quantity and related requirements of auxiliary facilities such as seepage wells, detection wells, diversion wells, and marker posts.

[0088] S6: Impact of grounding electrode on surrounding facilities and protection design: Calculate and analyze the impact of the recommended electrode site on surrounding substations, power plants, converter stations, metal pipelines, railways and other related facilities, and propose solutions for the affected facilities.

[0089] In step S33, the step potential difference verification is performed according to the following formula:

[0090] ;

[0091] In the formula: U pm U is the maximum allowable step potential difference of the grounding electrode. pm =7.42+0.0318ρ s , ρ s U represents the equivalent resistivity (Ω•m) of the surface soil in the polar region. max The maximum calculated value of the step potential difference under the designed electrode 1 arrangement scheme;

[0092] Unlike circular or racetrack-shaped grounding electrodes, dendritic grounding electrodes are arranged linearly. This results in a more uneven distribution of overflow current density in the feeder elements (12). Therefore, the overflow current density deviation coefficient can be used as one of the indicators for evaluating the merits of different dendritic arrangement schemes. Overflow current density deviation coefficient k er Defined as:

[0093] ;

[0094] In the formula: I d τ is the grounding current flowing into the ground electrode. av τ is the average overflow density; τ(l) is the overflow density at any point; L is the total length of electrode 1.

[0095] Because the lengths and distribution positions of the segments of a dendritic grounding electrode may vary, there may be multiple segmentation schemes for electrode 1. The current magnitude of each conductor 4 in the current-conducting system design is closely related to the segmentation scheme of electrode 1. An unreasonable segmentation scheme may lead to significant current differences between conductors, reducing conductor utilization and threatening the safe and stable operation of the grounding electrode. Currently, there are no relevant evaluation indicators for the current uniformity of each conductor 4 in the specifications. This invention introduces a current distribution uniformity coefficient for conductor 4 to evaluate the uniformity of the current in each segmentation scheme of the dendritic grounding electrode. The smaller the value, the better the uniformity.

[0096] In step S45, the current distribution uniformity coefficient σ of the current guide 4 is defined as:

[0097] ;

[0098] In the formula: I i denoted as , where μ is the total current of the conductor 4 on each segmented electrode under a certain electrode 1 segmentation scheme; μ is the average value of the total current of the conductor 4 on each segmented electrode under a certain electrode 1 segmentation scheme; and n is the number of segments of electrode 1.

[0099] Example 1:

[0100] 1. Basic information on the grounding electrode address of a certain converter station:

[0101] The terrain of the extreme site area is generally low-altitude hills and inter-hill valleys, with relatively irregular, uneven, and disorderly terrain. The plateaus are mainly hills, and the valleys are generally about 30 to 50 meters wide, with some areas reaching 100 meters. They are mainly farmland, and there are also many houses scattered throughout the extreme site area.

[0102] 2. Arrangement scheme of grounding electrode 1 of the converter station:

[0103] Considering the relatively irregular, uneven, and cluttered nature of the electrode site, as well as the scattered distribution of numerous buildings, nine electrode layout schemes were proposed during the engineering design, including double-ring circular, double-ring runway, and tree-like arrangements. Figures 6 to 14 As shown. Given the large elevation difference of the terraces, the thin soil cover layer, and the high soil resistivity in the polar site area, under all the above layout schemes, electrode 1 is arranged as much as possible in farmland valleys with thick soil cover layer and low soil resistivity.

[0104] Due to the limited range of the polar address area, the length of electrode 1 in each scheme is limited. After verification such as step potential difference, only three arrangement schemes, namely double-ring circular, double-ring racetrack, and tree-shaped, can meet the technical requirements.

[0105] Under the double-ring circular and double-ring runway layout schemes, due to the limitations of the extreme site topography, both layout schemes require the demolition of buildings and the enclosure of a densely populated area. To avoid significant risks such as construction obstruction during subsequent construction and operation, the enclosed buildings also need to be demolished. Therefore, under these conditions, the technical and economic comparison of the three layout schemes—double-ring circular, double-ring runway, and tree-branch layout—is shown in Table 1.

[0106] Table 1 is a technical and economic comparison table of double-ring circular, double-ring runway, and tree-shaped schemes.

[0107]

[0108] Note: 1. Investment estimates for each scheme are based on the dendritic scheme, with added value considered; 2. The maximum allowable step potential difference is 7.98V / m, the maximum allowable grounding electrode temperature is 90℃, and the maximum allowable surface current density at the coke-soil contact surface is 1A / m. 2 .

[0109] As can be seen from Table 1, the dendritic grounding electrode requires a slightly longer electrode length than the other two schemes due to its more uneven discharge density. However, it does not involve demolition of buildings, does not surround dense buildings, has less difficulty in construction coordination, and is the most economical. Therefore, the dendritic scheme is the recommended scheme.

[0110] 3. Design of the grounding electrode current guiding system for this converter station:

[0111] After technical and economic comparison, it was determined that the grounding electrode adopts a tree-shaped arrangement scheme. Electrode 1 contains 8 branches with a total length of 5172m and a burial depth of 4.5m. At the same time, based on the site topography and facility distribution, the grounding electrode is located in the central equipment area and near the geometric center of the overall electrode 1. The current diversion system adopts buried cable.

[0112] Based on the design principles of the dendritic grounding electrode current conduction system and in light of the actual conditions of this project, five major schemes, ranging from 8 to 12 segments, were proposed for electrode 1, with a total of 28 detailed schemes.

[0113] Select the optimal solution from these five major options for comprehensive comparison, such as... Figures 15-19 As shown in Table 2, the comparison results of each scheme are as follows.

[0114] Table 2 is a comparison table of the 5-electrode 1-segment scheme.

[0115]

[0116] Note: The total investment for each plan is based on the optimal plan divided into 11 segments, taking into account the added value.

[0117] In terms of the uniformity of current distribution in the conductor, among the five schemes, the 11-segment scheme has the smallest uniformity coefficient of cable current distribution, the best uniformity of cable current distribution, and the highest cable utilization rate.

[0118] In terms of total investment, the 11-segment scheme is the most economical. The 8-segment, 9-segment, and 10-segment schemes have fewer electrode segments and fewer cable segments, resulting in shorter total cable lengths but larger required cable cross-sections, leading to poor economic efficiency. Compared to the 11-segment scheme, the 12-segment scheme uses cables with the same cross-section, but the total cable length is even longer, resulting in poor economic efficiency.

[0119] Considering both current uniformity and total investment, the 1-segment, 11-section electrode design is recommended. In summary, the design scheme for the tree-shaped grounding electrode current-conducting system of the Chongqing converter station is as follows: Figure 20 As shown.

[0120] Currently, the grounding electrode of the converter station has been built and put into operation. According to the high current test results, the grounding resistance, step potential difference, contact potential difference and other parameters of the grounding electrode all meet the design requirements and have good conformity with the design values, which proves the feasibility of the dendritic grounding electrode and its design method proposed in this invention.

[0121] This invention is not limited to the above-described optional embodiments. Anyone can derive other various forms of products under the guidance of this invention. However, regardless of any changes made in their shape or structure, any technical solution that falls within the scope of the claims of this invention shall be protected by this invention.

Claims

1. A dendritic DC grounding electrode for smart grids, characterized in that: It includes an electrode (1), which includes a straight electrode main trunk, several straight electrode branches set near the straight electrode main trunk, and an annular end electrode set near the other end of the straight electrode branch. Each straight electrode branch corresponds to an annular end electrode. It also includes a central equipment or grounding electrode line terminal tower (2). The electrode (1) is divided into several segments. Each segment of the electrode (1) is connected to a feed cable (3). The feed cable (3) is connected to the central equipment or grounding electrode line terminal tower (2) through a guide line (4).

2. The tree-shaped DC grounding electrode for smart grids according to claim 1, characterized in that: The electrode (1) is made of an active filling material (11) and a number of feeding elements (12) embedded in the active filling material (11). The feeding cable (3) is connected to a number of feeding elements (12) in a segment of the electrode (1).

3. A dendritic DC grounding electrode for a smart grid according to claim 2, characterized in that: The material of the power supply element (12) is high silicon ferrochrome or high silicon cast iron. The power supply cable (3) includes a power distribution cable (31) and a number of lead cables (32) on the power supply element (12) within a segment of the electrode (1). The power distribution cable (31) is laid along with the electrode (1). The power distribution cable (31) is connected to the guide line (4). A number of welding heads (33) are provided on the power distribution cable (31). A number of lead cables (32) are welded together on a welding head (33) of the power distribution cable (31).

4. A dendritic DC grounding electrode for a smart grid according to claim 2, characterized in that: The material of the power supply element (12) is a steel rod. The power supply cable (3) includes a number of feeder cables (32) on a segment of the electrode (1) and a conductor (4) on a segment of the electrode (1).

5. A dendritic DC grounding electrode for a smart grid according to claim 1, characterized in that: The guide line (4) is laid out in an overhead or underground manner. The central equipment or grounding electrode line terminal tower (2) is connected to the busbar (41), and several guide lines (4) are connected to the busbar (41).

6. A design method for a dendritic DC grounding electrode for a smart grid, used to design a dendritic DC grounding electrode for a smart grid as described in any one of claims 1 to 5, characterized in that: Includes the following steps: S1: Recommended pole site determination: Based on the distribution of obstacles including surrounding metal pipelines, railways, and substations, and taking into account the conditions of the pole site itself, a recommended pole site is determined; S2: Recommended Polar Site Survey: Conduct surveys and data collection on recommended polar sites, including topographic mapping, topography, geological structure and seismic parameters, stratigraphy, groundwater level, adverse geological processes, mineral resources, shallow and deep soil resistivity, soil heat capacity and thermal conductivity, water conservancy projects, flood inundation, waterlogging, erosion, and soil temperature. S3: Electrode (1) arrangement scheme determined; S4: Flow diversion system design; S5: Auxiliary Facility Design: Based on the requirements of regulations and specifications and in combination with the actual situation of the project, specify the location, quantity and related requirements of auxiliary facilities including seepage wells, detection wells, diversion wells and marker posts; S6: Impact of grounding electrode on surrounding facilities and protection design: Calculate and analyze the impact of the recommended electrode site on surrounding facilities including substations, power plants, converter stations, metal pipelines, and railways, and propose solutions for the affected facilities.

7. The design method of a dendritic DC grounding electrode for a smart grid according to claim 6, characterized in that: Step S3 includes the following specific steps: S31: Based on the distribution of facilities including the topography, landforms and buildings in the polar site area, select relatively flat strip areas with thick soil layers that can be used for electrode (1) placement; S32: Estimate the required electrode (1) length based on the design system conditions, and formulate all possible electrode (1) arrangement schemes in conjunction with the selected strip regions; S33: Perform simulation calculations on each electrode (1) arrangement scheme to determine the relevant technical parameters of each scheme, including the burial depth of electrode (1), electrode (1) material and size, and perform verification including step potential difference to confirm whether each arrangement scheme meets the technical requirements. S34: Combine the engineering quantity and overflow density deviation coefficient to comprehensively compare and select the layout schemes that meet the technical requirements, and determine the recommended electrode (1) layout scheme.

8. The design method of a dendritic DC grounding electrode for a smart grid according to claim 7, characterized in that: In step S33, the step potential difference verification is performed according to the following formula: ； In the formula: U pm U is the maximum allowable step potential difference of the grounding electrode. pm =7.42+0.0318ρ s , ρ s U represents the equivalent resistivity of the surface soil in the polar region. max The maximum calculated value of the step potential difference under the designed electrode (1) arrangement scheme; The overflow density deviation coefficient is used as one of the indicators for evaluating the merits of each electrode (1) arrangement scheme. The overflow density deviation coefficient k er Defined as: ； In the formula: I d τ is the grounding current flowing into the ground electrode. av τ is the average overflow density; τ(l) is the overflow density at any point; L is the total length of electrode (1).

9. The design method of a dendritic DC grounding electrode for a smart grid according to claim 6, characterized in that: Step S4 includes the following specific steps: S41: Location of central equipment or grounding electrode line terminal tower (2): The central equipment should be located near the geometric center of the overall electrode (1) as much as possible; when the conductor (4) is overhead and no busbar (41) is installed, the grounding electrode line terminal tower should be located near the geometric center of the overall electrode (1) as much as possible. S42: Determination of the guide line (4) scheme: Based on the arrangement scheme of the electrode (1) and the terrain and features of the site, determine whether the guide line (4) should be an overhead line or a buried cable. S43: Electrode (1) Segmentation scheme formulation: Segmentation is carried out according to the length and position of each straight electrode main trunk and straight electrode branch, and all possible segmentation schemes are formulated. The segmentation scheme is formulated with the goal of making the current of the guide wire (4) as uniform as possible. S44: For each electrode (1) segmentation scheme, determine the number, type, and cross-section of the power distribution cable (31) and the guide wire (4), and clarify their laying path, laying method, and burial depth; S45: Combine the engineering quantity and the current distribution uniformity coefficient of the guide line (4) to comprehensively compare and select the segmentation schemes of each electrode (1) and determine the recommended segmentation scheme of electrode (1) and the design scheme of the guide system.

10. The design method of a dendritic DC grounding electrode for a smart grid according to claim 9, characterized in that: In step S45, the current distribution uniformity coefficient σ of the conductor (4) is defined as: ； In the formula: I i μ is the total current of the guide lines (4) on each segmented electrode under a certain electrode (1) segmentation scheme; μ is the average value of the total current of the guide lines (4) on each segmented electrode under a certain electrode (1) segmentation scheme; n is the number of segments of the electrode (1).

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