Branch-shaped direct current grounding electrode for smart power grid and design method of branch-shaped direct current grounding electrode

Abstract

The invention belongs to the technical field of direct-current grounding electrodes, and particularly relates to a branch-shaped direct-current grounding electrode for an intelligent power grid and a design method of the branch-shaped direct-current grounding electrode. According to the technical scheme, the branch-shaped direct-current grounding electrode for the intelligent power grid comprises an electrode, and the electrode comprises a linear electrode trunk, a plurality of linear electrode branches arranged close to the linear electrode trunk and annular end electrodes arranged close to the other ends of the linear electrode branches; the system further comprises a central device or a grounding electrode line terminal tower, the electrode is divided into a plurality of sections, each section of the electrode is connected with a feed cable, and the feed cables are connected with the central device or the grounding electrode line terminal tower through diversion wires. The invention provides a branch-shaped direct-current grounding electrode for an intelligent power grid and a design method of the branch-shaped direct-current grounding electrode. The problems that a large number of houses are surrounded and need to be demolished in a large range due to annular arrangement of electrodes are solved while the discharge effect of the electrodes is ensured.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of DC grounding electrode, and particularly relates to a tree-shaped DC grounding electrode for smart grid and a design method thereof. BACKGROUND

[0002] At present, the DC grounding electrodes built and put into operation in China mostly adopt the horizontal shallow-buried annular arrangement scheme of circular, runway-shaped and the like. Such scheme has the advantages of uniform current distribution, convenient construction and operation and maintenance, etc., but generally requires a large site, a generally flat terrain, thick soil and the like. For some mountainous, hilly and even plain areas, the available electrode site resources can be extremely scarce due to the influence of the terrain, geology, soil resistivity or metal pipelines, railways, houses and other related facilities of the electrode site, and the available electrode site can not have the characteristics of a large site and a generally flat terrain, and can not be suitable for the overall circular, elliptical, runway-shaped and other annular arrangement modes or the adoption of the latter technical and economic performance. SUMMARY

[0003] In order to solve the above problems existing in the prior art, the purpose of the present application is to provide a tree-shaped DC grounding electrode for smart grid and a design method thereof, which arranges the electrode in a strip shape according to the terrain, house and other physical isolation facility distribution of the electrode site, arranges the electrode in a relatively flat, thick soil and low soil resistivity strip-shaped area, and can flexibly avoid various physical isolation facilities such as houses, ensure the current leakage effect of the electrode and avoid various problems such as the need for large-scale demolition of a large number of houses surrounded by the electrode due to the annular arrangement of the electrode.

[0004] The technical scheme adopted by the present application is as follows: A tree-shaped DC grounding electrode for smart grid, comprising an electrode, the electrode comprising a straight electrode trunk, a plurality of straight electrode branches arranged close to the straight electrode trunk, and a ring-shaped end electrode arranged close to the other end of the straight electrode branch; further comprising a central device or a grounding electrode line terminal tower, the electrode is divided into a plurality of segments, each segment of the electrode is connected with a feeder cable, and the feeder cable is connected with the central device or the grounding electrode line terminal tower through a current guide wire.

[0005] As a preferred scheme of the present application, the material of the electrode comprises an active filling material and a plurality of feeder elements embedded in the active filling material, and the feeder cable is connected with the plurality of feeder elements in one segment of the electrode.

[0006] As a preferred scheme of the present application, the material of the feeder element is high-silicon chromium iron or high-silicon cast iron, the feeder cable comprises a distribution cable and a drainage cable provided on the plurality of feeder elements in one segment of the electrode, the distribution cable is laid along with the electrode, the distribution cable is connected with the current guide wire, a plurality of welding heads are provided on the distribution cable, and the plurality of drainage cables are welded on one welding head of the distribution cable.

[0007] As a preferred scheme of the present application, the material of the feeding element is a steel rod, the feeding cable comprises a current leading cable on each feeding element in a section of the electrode, and the current leading cables on each feeding element in a section of the electrode are connected with a current leading wire.

[0008] As a preferred scheme of the present application, the current leading wire is arranged in an overhead or underground manner, a bus bar is connected with the central device or the ground electrode line terminal tower, and the current leading wires are connected with the bus bar.

[0009] A design method of a tree-shaped DC grounding electrode for a smart grid, comprising the following steps: S1: determining a recommended electrode site according to the distribution of obstacle facilities including surrounding metal pipelines, railways and transformer substations, and comprehensively considering the conditions of the electrode site itself; S2: surveying the recommended electrode site, including topographic survey, topography and geomorphology, geological structure and seismic parameters, stratum lithology, underground water level, adverse geological action, mineral resources, shallow and deep soil resistivity, soil heat capacity and heat conductivity, water conservancy projects, flood inundation, waterlogging, erosion, and soil temperature; S3: determining an electrode arrangement scheme; S4: designing a current leading system; S5: designing auxiliary facilities, including the setting positions, quantities and related requirements of water seepage wells, detection wells, drainage wells and marker piles according to the requirements of regulations and specifications and the actual engineering conditions; S6: designing the influence of the grounding electrode on surrounding facilities and protection, including transformer substations, power plants, converter stations, metal pipelines and railways, and proposing treatment schemes for the related facilities that are affected;

[0010] As a preferred scheme of the present application, step S3 comprises the following specific steps: S31: screening out each relatively flat and thick-soil belt-shaped region available for electrode arrangement according to the topography, geomorphology and facility distribution of the electrode site region; S32: estimating the required electrode length according to the design system conditions, and formulating all possible electrode arrangement schemes in combination with the screened out belt-shaped regions; S33: performing simulation and calculation on each electrode arrangement scheme to determine the related technical parameters including electrode burial depth, electrode material and size, and performing verification including step potential difference to confirm whether each arrangement scheme meets the technical condition requirements; S34: The engineering quantity and the overflow density deviation coefficient are combined to comprehensively compare and select each layout scheme meeting the technical condition requirement, and a recommended electrode layout scheme is determined.

[0011] As a preferred scheme of the present application, in step S33, the step potential difference verification is performed according to the following formula: ; In the formula, U pm is the maximum allowable step potential difference of the grounding electrode, U pm = 7.42 + 0.0318p s , p s is the equivalent resistivity of the surface soil of the electrode site area, U max is the maximum calculated step potential difference under the designed electrode layout scheme. The overflow density deviation coefficient is taken as one of the indexes for evaluating the pros and cons of each electrode layout scheme, and the overflow density deviation coefficient k er is defined as: ; In the formula, I d is the grounding current, t av is the average overflow density, t(l) is the overflow density of any point, and L is the total length of the electrode.

[0012] As a preferred scheme of the present application, step S4 includes the following specific steps: S41: The center device or the grounding electrode line terminal tower is located: the center device is arranged as close as possible to the geometric center position of the overall electrode; when the current-carrying wire adopts an overhead mode and no busbar is arranged, the grounding electrode line terminal tower is arranged as close as possible to the geometric center position of the overall electrode; S42: The current-carrying wire scheme is determined: according to the electrode layout scheme, the site topography and objects, the current-carrying wire adopts an overhead wire or a buried cable mode; S43: The electrode segmentation scheme is developed: according to the length and position of each straight electrode trunk and straight electrode branch, all possible segmentation schemes are developed, and the segmentation scheme development aims to make the current-carrying wire current as uniform as possible; S44: For each electrode segmentation scheme, the number, type, and cross section of the distribution cable and the current-carrying wire are determined, and the laying path, laying mode, and burial depth are clarified; S45: The engineering quantity and the current-carrying wire current distribution uniformity coefficient are combined to comprehensively compare and select each electrode segmentation scheme, and a recommended electrode segmentation scheme and a current-carrying system design scheme are determined.

[0013] As a preferred scheme of the present application, in step S45, the current-carrying wire current distribution uniformity coefficient s is defined as: ; In the formula: I i is the total current of the current-carrying wire on each segmented electrode under a certain electrode segmentation scheme; μ is the average value of the total current of the current-carrying wire on each segmented electrode under a certain electrode segmentation scheme; and n is the number of segments of the electrode.

[0014] The beneficial effects of the present application are: 1. The tree-shaped grounding electrode of the present application can arrange the electrode in a strip shape according to the terrain of the grounding electrode area, the distribution of physical isolation facilities such as houses, and the like, and can arrange the electrode in a relatively flat, thick soil layer, and low soil resistivity belt-shaped area, while flexibly avoiding various physical isolation facilities such as houses, ensuring the current leakage effect of the electrode and avoiding the problem of a large number of houses being surrounded and requiring a large range of demolition and the like caused by the ring-shaped arrangement of the electrode, reducing the house demolition and construction cost and construction coordination difficulty while meeting the engineering technical conditions, and providing a new idea and reference for the design of unconventional arrangement of the direct current grounding electrode in the future.

[0015] 2. The grounding electrode design of the present application needs to meet the technical condition requirements of current carrying, temperature rise, corrosion, grounding resistance, step potential difference, contact potential difference, transfer potential, surface current density and the like, to ensure the safe and reliable operation of the grounding electrode under the corresponding system conditions and within the design service life. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a structural schematic diagram of the present application; Figure 2 is a connection structure diagram of the feeder cable and the feeder element; Figure 3 is a sectional view of the electrode of the feeder cable; Figure 4 is a connection structure diagram of the distribution cable and the current-carrying wire; Figure 5 is a method flowchart of the present application; Figure 6 is a layout diagram of the electrode double-ring circular scheme; Figure 7 is a layout diagram of the electrode double-ring runway scheme; Figure 8 is a layout diagram of the electrode tree-shaped scheme; Figure 9 is a layout diagram of the electrode closed single-ring scheme; Figure 10 is a layout diagram of the electrode single-ring + line 2 scheme; Figure 11 is a layout diagram of the electrode split-ring scheme; Figure 12 is a layout diagram of the electrode split-ring + line scheme; Figure 13is the layout of electrode single ring + line 1 scheme; Figure 14 is the layout of electrode double line scheme; Figure 15 is the schematic diagram of electrode 8-segment optimal scheme; Figure 16 is the schematic diagram of electrode 9-segment optimal scheme; Figure 17 is the schematic diagram of electrode 10-segment optimal scheme; Figure 18 is the schematic diagram of electrode 11-segment optimal scheme; Figure 19 is the schematic diagram of electrode 12-segment optimal scheme; Figure 20 is the schematic diagram of the grounding electrode current guide system design scheme in the embodiment.

[0017] In the figure: 1-electrode; 2-center device or grounding electrode line terminal tower; 3-feeder cable; 4-current guide wire; 11-active filler material; 12-feeder element; 31-distribution cable; 32-drainage cable; 33-welding head; 41-busbar. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0020] As Figures 1-4 shown, the tree-shaped DC grounding electrode for smart grid includes an electrode 1, the electrode 1 includes a straight electrode 1 trunk, a plurality of straight electrode 1 branches arranged close to the straight electrode 1 trunk, and a ring-shaped end electrode 1 arranged close to the other end of the straight electrode 1 branch; further includes a center device or grounding electrode line terminal tower 2, the electrode 1 is divided into a plurality of segments, each segment of the electrode 1 is connected with a feeder cable 3, and the feeder cable 3 is connected with the center device or grounding electrode line terminal tower 2 through a current guide wire 4.

[0021] The material of the electrode 1 comprises active filling material 11 and several feeding elements 12 embedded in the active filling material 11, and the feeding cable 3 is connected with the several feeding elements 12 in one segment of the electrode 1.

[0022] When the material of the feeding elements 12 is high-silicon chromium iron or high-silicon cast iron, the feeding cable 3 comprises a distribution cable 31 and several self-provided current-carrying cables 32 on the several feeding elements 12 in one segment of the electrode 1, the distribution cable 31 is laid along with the electrode 1, the distribution cable 31 is connected with the current-carrying wire 4, and the distribution cable 31 is provided with several welding heads 33, and the several current-carrying cables 32 are welded on one welding head 33 of the distribution cable 31.

[0023] When the material of the feeding elements 12 is steel rods, the distribution cable 31 is not needed, and the feeding cable 3 comprises the several self-provided current-carrying cables 32 on the several feeding elements 12 in one segment of the electrode 1, and the several self-provided current-carrying cables 32 on the several feeding elements 12 in one segment of the electrode 1 are connected with one current-carrying wire 4.

[0024] The current-carrying wire 4 is arranged in an overhead laying or underground laying mode, the central device or the grounding electrode line terminal tower 2 is connected with a bus bar 41, and the several current-carrying wires 4 are all connected with the bus bar 41.

[0025] In order to ensure that the grounding electrode is safe and reliable in operation under the corresponding system conditions and in the design service life, the design of the grounding electrode needs to meet the technical condition requirements of current-carrying, temperature rise, corrosion, grounding resistance, step potential difference, touch potential difference, transfer potential, surface current density and the like. The system conditions and technical conditions related to the design of the DC grounding electrode are discussed in detail in the specification and specification such as DL / T 5224-2014 “Technical Specification for Design of High-voltage Direct-current Transmission Ground Return System”. The present application only discusses the design method and process of the dendritic grounding electrode in detail.

[0026] As shown in Figure 5 The design method of the dendritic DC grounding electrode for the smart grid comprises the following steps: S1: Recommended pole site determination: according to the distribution of surrounding metal pipelines, railways, substations and other obstacle facilities, and combined with the conditions of the pole site itself, the recommended pole site is determined.

[0027] S2: Recommended pole site survey: topographic map measurement, topography, geological structure and seismic parameters, stratum lithology, underground water level, adverse geological action, mineral resources, shallow and deep soil resistivity, soil heat capacity and thermal conductivity, water conservancy projects, flood inundation, waterlogging, erosion, soil temperature and the like are surveyed and collected.

[0028] S3: electrode 1 arrangement scheme determination: S31: According to the terrain, topography, and distribution of facilities such as houses, etc. in the electrode area, screen out each relatively flat and thick soil layer belt for electrode 1 arrangement; S32: Estimate the required electrode 1 length according to the design system conditions, and combine the screened out each belt to develop all possible electrode 1 arrangement schemes; In the process of developing the electrode 1 arrangement scheme, in order to obtain a relatively optimal scheme, the following points need to be noted: a) The overall electrode 1 extension in each direction should be as short as possible, and the entire electrode 1 arrangement should be as "round" as possible to reduce the non-uniformity of the leakage current density; b) The electrode 1 should be arranged as symmetrically as possible to improve the operating performance while considering the arrangement scheme of the current diversion system to improve the balance and reliability of the current diversion system; c) In the process of selecting the burial path of the straight electrode 1, the number of angles should be reduced as much as possible to avoid "large angles" and reduce the leakage current density value at the angles; d) At the end with the largest overflow density, a suitable "flow equalization ring" such as a runway-shaped end electrode 1 can be arranged according to the size of the site to reduce the end effect; S33: Simulate and calculate each electrode 1 arrangement scheme to determine the related technical parameters such as electrode 1 burial depth, electrode 1 material and size, and perform step-over potential difference check to confirm whether each arrangement scheme meets the technical condition requirements; In particular, since the tree-shaped grounding electrode has a wider electrode 1 arrangement range than the ring-shaped grounding electrode, there may be a large difference in soil resistivity at different branch locations, so different soil models can be considered for simulation calculation at different locations to make the current distribution and other calculation values more accurate; S34: Combine the engineering quantity, overflow density deviation coefficient, etc. to comprehensively compare and select each arrangement scheme that meets the technical condition requirements to determine the recommended electrode 1 arrangement scheme.

[0029] S4: Current diversion system design: S41: Center device or grounding electrode line terminal tower 2 site selection: The center device should be arranged as close as possible to the geometric center of the overall electrode 1; When the current diversion system adopts overhead mode without setting up a bus 41, the grounding electrode line terminal tower should also be arranged as close as possible to the geometric center of the overall electrode 1, which is beneficial to the arrangement of the current diversion system; S42: Current diversion system scheme determination: Determine whether to adopt overhead line or buried cable mode according to the electrode 1 arrangement scheme, site terrain and objects, etc.; S43: Electrode 1 segmentation scheme development: Segment each branch electrode 1 according to its length and position to develop all possible segmentation schemes, and the segmentation scheme should aim to make the current of the current diversion line as uniform as possible, and the number of segments should not be too many to avoid making the current diversion system too complex; S44: For each electrode 1 segmentation scheme, determine the number, model, cross section, etc. of power distribution cable 31, flow line, and determine its laying path, laying method, burial depth, etc. S45: Comprehensive comparison of each electrode 1 segmentation scheme in combination with engineering quantity, current distribution uniformity coefficient of flow line, etc. to determine the recommended electrode 1 segmentation scheme and flow system design scheme.

[0030] S5: Auxiliary facility design: According to the requirements of regulations and specifications and combined with the actual situation of the project, determine the setting position, quantity and related requirements of auxiliary facilities such as infiltration well, detection well, drainage well, marker pile, etc.

[0031] S6: Influence of grounding electrode on surrounding facilities and protection design: Calculate and analyze the influence of the recommended site on surrounding substations, power plants, converter stations, metal pipelines, railways, etc. Related facilities that are affected are proposed for treatment.

[0032] In step S33, the step potential difference check is performed according to the following formula: ; In the formula: U pm is the maximum allowable step potential difference of the grounding electrode, U pm = 7.42 + 0.0318ρ s , ρ s is the equivalent resistivity of the surface soil in the electrode site area (Ω•m), U max is the maximum calculated value of the step potential difference under the designed electrode 1 arrangement scheme; Unlike circular, racetrack-shaped and other ring-shaped grounding electrodes, the tree-shaped grounding electrode is linearly arranged, and the overflow density distribution of its feeder element 12 will be more uneven, so the overflow density deviation coefficient can be used as one of the indicators to evaluate the pros and cons of each tree-shaped arrangement scheme. The overflow density deviation coefficient k er is defined as: ; In the formula: I d is the grounding electrode current; τ av is the average overflow density; τ(l) is the overflow density at any point; L is the total length of the electrode 1.

[0033] Because the length and distribution position of each segment electrode 1 of the tree-shaped grounding electrode can be different, the segment scheme of the tree-shaped grounding electrode 1 can be more, and the current size of each current guide line 4 is closely related to the segment scheme of the electrode 1 when the current guide system is designed. If the segment scheme is unreasonable, the current difference between each current guide line can be large, which reduces the utilization rate of the current guide line and threatens the safe and stable operation of the grounding electrode. For the uniformity of the current of each current guide line 4, there is no related evaluation index in the current regulation specification. The current guide line 4 current distribution uniformity coefficient is introduced to evaluate the uniformity of the current of each segment scheme of the tree-shaped grounding electrode. The smaller the value is, the better the uniformity is.

[0034] In step S45, the current guide line 4 current distribution uniformity coefficient σ is defined as: ; In the formula, I i is the total current of the current guide line 4 on each segment electrode 1 under a certain electrode 1 segment scheme; μ is the average value of the total current of the current guide line 4 of each segment electrode 1 under a certain electrode 1 segment scheme; and n is the number of segments of the electrode 1.

[0035] Embodiment 1: 1. Basic situation of the grounding electrode site of a certain converter station: The overall topography of the grounding electrode site is low-altitude hilly and inter-hill valley land. The site is relatively irregular, uneven and messy. The terraces are mainly mountainous and valley land, which is generally about 30-50 m wide, and locally up to 100 m. The terraces are mainly farmland, and there are also many scattered houses in the grounding electrode site.

[0036] 2. The electrode 1 arrangement scheme of the grounding electrode of the converter station: In view of the characteristics that the site is relatively irregular, uneven and messy, and many houses are scattered, nine electrode 1 arrangement schemes such as double-ring circular, double-ring runway, and tree-shaped are formulated in the engineering design, as shown in FIG. 1. Figures 6-14 In view of the large height difference of the terraces in the grounding electrode site, the thin soil cover layer and the high soil resistivity, the electrodes 1 in all the above arrangement schemes are arranged in the farmland valley land with thick soil cover layer and low soil resistivity as much as possible.

[0037] Because the length of the electrode 1 in each scheme is limited due to the limited range of the grounding electrode site, only the double-ring circular, double-ring runway and tree-shaped arrangement schemes can meet the technical condition requirements after step potential difference verification.

[0038] Under the double ring circular and double ring racetrack scheme, due to the limitation of the site topography, the two arrangement schemes need to produce house demolition, and need to surround a piece of dense houses. In order to avoid the risk of blocking work during subsequent construction and operation, the surrounded houses also need to be demolished. Therefore, under the above premise, the technical and economic comparison of the double ring circular, double ring racetrack and tree branch schemes is shown in Table 1.

[0039] Table 1 is a table for comparing the technical and economic comparison of the double ring circular, double ring racetrack and tree branch schemes.

[0040]

[0041] Note: 1. The investment estimation of each scheme is based on the tree branch scheme as the benchmark, considering the value-added; 2. The maximum allowable step potential difference is 7.98V / m, the maximum allowable grounding electrode temperature is 90℃, and the maximum surface current density of the coke and soil contact surface is 1A / m 2 .

[0042] As can be seen from Table 1, the tree branch grounding electrode has a more uneven discharge density, resulting in a slightly longer electrode 1 length compared to the other two schemes. However, it does not require house demolition, does not surround dense houses, has less construction coordination difficulty and is the most economical, so the tree branch scheme is recommended.

[0043] 3. Design of the grounding electrode current lead system of the converter station: After technical and economic comparison, the tree branch arrangement scheme is selected for the grounding electrode, electrode 1 includes 8 branches with a total length of 5172m and a burial depth of 4.5m. According to the site topography and facility distribution, the grounding electrode is set in the central equipment area near the geometric center of the overall electrode 1, and the current lead system uses buried cable.

[0044] According to the design principles of the tree branch grounding electrode current lead system and combined with the actual situation of the project, 5 major schemes including 8 segments and 12 segments are proposed for the segmentation of electrode 1, and a total of 28 detailed schemes are proposed.

[0045] The optimal scheme of the 5 major schemes is selected for comprehensive comparison, as shown in Figures 15-19 Table 2 shows the comparison of each scheme.

[0046] Table 2 is a comparison table of 5 electrode 1 segmentation schemes.

[0047]

[0048] Note: The total investment of each scheme is based on the 11th segment optimal scheme as the benchmark, considering the value-added.

[0049] From the aspect of current uniformity of the flow line, the cable current distribution uniformity coefficient of the 11-section scheme is the smallest, the cable current distribution uniformity is the best, and the cable utilization rate is the highest.

[0050] From the aspect of total investment, the 11-section scheme is the most economical. The 8-section, 9-section and 10-section schemes have less electrode 1 sections and cable sections, so that the total cable length is shorter but the required cable cross section is larger, resulting in poor economy. Compared with the 11-section scheme, the 12-section scheme uses the same cross-section cable but has a longer total cable length, resulting in poor economy.

[0051] Considering the current uniformity and total investment, the 11-section scheme of the electrode 1 is recommended. In summary, the design scheme of the flow guide system of the tree-shaped grounding electrode of the Chongqing converter station is as shown in Figure 20

[0052] At present, the grounding electrode of the converter station has been built and put into operation. According to the results of the large current test, the parameters such as the grounding resistance, the step potential difference and the contact potential difference of the grounding electrode meet the design requirements and have good compliance with the design values, proving the feasibility of the tree-shaped grounding electrode and the design method thereof.

[0053] The present application is not limited to the above-mentioned optional embodiments, and anyone can derive other various forms of products under the inspiration of the present application, but regardless of any changes in shape or structure, any technical solutions falling within the scope defined by the claims of the present application fall within the protection scope of the present application.​

Claims

1. A dendritic DC grounding electrode for smart grids, characterized in that: It includes an electrode (1), which includes a straight electrode main body, a straight electrode branch set near the straight electrode main body, and an annular end electrode (1) set near the other end of the straight electrode branch; 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).

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, the 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 (1) 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 (1) under a certain electrode (1) segmentation scheme; n is the number of segments of the electrode (1).

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