A deep well grounding electrode current equalization configuration method and system

Abstract

This invention discloses a method and system for current sharing configuration of deep well grounding electrodes. First, it detects whether the current distribution of each sub-grounding electrode in the deep well grounding electrode is uniform. If the current distribution is uneven, current sharing is performed on each sub-grounding electrode based on the current dissipation density at the end of each sub-grounding electrode. Once the current distribution of all sub-grounding electrodes in the deep well grounding electrode is uniform, iterative current sharing is performed between the electrodes until the sub-grounding electrodes reach the optimal current sharing state. This makes the current dissipation density distribution on the DC deep well grounding electrode more uniform, reduces the maximum current dissipation density, reduces the grounding electrode temperature rise, and avoids damage to the deep well grounding electrode due to excessive current density. This solves the technical problem that existing deep well grounding electrodes are prone to malfunction due to excessively concentrated current dissipation, leading to failure and damage due to excessive current density.

Description

Technical Field

[0001] This invention relates to the field of high voltage direct current transmission grounding technology, and in particular to a method and system for configuring current sharing of deep well grounding electrodes. Background Technology

[0002] As a key component of DC transmission systems, the grounding electrode plays an important role in clamping the neutral point potential and providing a path for current to enter the ground, ensuring the safety of the monopolar ground during operation.

[0003] Compared to traditional grounding electrodes, deep well grounding electrodes offer significant advantages, including smaller footprint, fewer sub-grounding electrodes, the ability to utilize deep, low-resistivity soil for current dissipation, and minimal impact on shallow metal pipeline corrosion. They save land, reduce land acquisition difficulties, and, due to lower site requirements, can be built near converter stations, reducing grounding electrode lead construction costs. They also mitigate step and contact voltage hazards, avoid stray current corrosion, reduce vegetation damage, and are not limited by complex terrain. However, deep well grounding electrodes also present challenges. Their conductors are slender, straight electrodes. Soil stratification and end effects lead to uneven current density distribution, with current density and temperature rise in the end layers and low-resistivity soils far exceeding other areas. When sub-grounding electrodes are asymmetrically arranged, the large differences in current density cause current to concentrate in some sub-grounding electrodes. If the design is inadequate, the grounding electrode will malfunction, potentially leading to failure due to excessive current density. Current technologies do not offer feasible solutions to the problem of excessive current concentration in deep well grounding electrodes. Summary of the Invention

[0004] This invention provides a method and system for configuring current sharing of deep well grounding electrodes, which solves the technical problem that existing deep well grounding electrodes are prone to failure due to excessive concentration of current, leading to malfunctions and damage due to excessive current density.

[0005] In view of this, the first aspect of the present invention provides a method for configuring current sharing of grounding electrodes in deep wells, comprising:

[0006] Current distribution detection is performed on each sub-grounding electrode in the deep well grounding electrode;

[0007] If the current distribution of each sub-grounding electrode in the deep well grounding electrode is uneven, then the current sharing treatment of each sub-grounding electrode in the deep well grounding electrode shall be performed separately.

[0008] When the current distribution of all sub-grounding electrodes in the deep well grounding electrode is uniform, based on the current dissipation density at the end of each sub-grounding electrode in the deep well grounding electrode, the inter-electrode iterative current sharing process is performed on each sub-grounding electrode in the deep well grounding electrode until each sub-grounding electrode in the deep well grounding electrode reaches the optimal current sharing state.

[0009] Optionally, based on the current dissipation density at the ends of each sub-grounding electrode in the deep well grounding electrode, current sharing processing is performed on each sub-grounding electrode in the deep well grounding electrode, including:

[0010] For the sub-grounding electrode portion in a deep well where the current density exceeds a threshold, the surface resistivity should be at least 10. A high-resistance coating is applied to the outside of the grounding conductor protective steel pipe of the deep well grounding electrode to suppress areas where the stray current density exceeds the threshold.

[0011] Optionally, the surface resistivity of the high-resistivity coating can be calculated as follows:

[0012]

[0013] in, The resistivity of the high-resistivity coating per unit length of the deep well grounding electrode. d is the volume resistivity of the high-resistivity coating, d is the thickness of the high-resistivity coating, and D is the outer diameter of the grounding conductor sheath steel pipe.

[0014] Optionally, the threshold is:

[0015]

[0016] in, For the threshold, The constant coefficient, The average current density of the deep well grounding electrode.

[0017] Optionally, iterative current sharing processing is performed on each sub-grounding electrode in the deep well grounding electrode until each sub-grounding electrode in the deep well grounding electrode reaches the optimal current sharing state, including:

[0018] With minimizing the maximum current dissipation density as the current sharing design objective, the current sharing resistance value of each sub-grounding electrode in the deep well grounding electrode is calculated;

[0019] Adjust the ground current of each sub-grounding electrode according to the calculated current sharing resistance value until each sub-grounding electrode in the deep well reaches the optimal current sharing state.

[0020] Optionally, iterative current sharing processing is performed on each sub-grounding electrode in the deep well grounding electrode until each sub-grounding electrode in the deep well grounding electrode reaches the optimal current sharing state, including:

[0021] A flow distribution calculation model is constructed with the goal of minimizing the maximum flow density in the flow distribution design.

[0022] A current-sharing resistor is connected in series in the feeder cable, the current shunting ratio between each sub-grounding electrode is adjusted, and the current-sharing resistance value of each sub-grounding electrode in the deep well grounding electrode is calculated according to the current dissipation calculation model.

[0023] Adjust the current sharing resistance according to the calculated current sharing resistance value to adjust the ground current of each sub-grounding electrode until each sub-grounding electrode in the deep well grounding electrode reaches the optimal current sharing state.

[0024] Optionally, the optimization objective of the current distribution calculation model is:

[0025]

[0026] The constraints of the diffuse flow calculation model are:

[0027]

[0028]

[0029]

[0030]

[0031]

[0032] in, Let be the current dissipation density of the k-th conductor segment of the i-th sub-grounding electrode. Let be the potential of the m-th conductor segment of the n-th sub-grounding electrode. Let be the ground current of the k-th conductor segment of the i-th sub-grounding electrode. Let be the surface area of ​​the k-th conductor segment of the i-th sub-grounding electrode. Let be the equivalent series resistance value of the i-th sub-grounding electrode, and U be an N-dimensional column vector whose elements are all u. For the reason The diagonal matrix is ​​composed of u, where u is the voltage of the busbar at the center of the grounding electrode, R is an N×N matrix of mutual resistance between sub-grounding electrodes, and I is a matrix composed of The column vector formed Let be the mutual resistance between the k-th conductor segment of the i-th sub-grounding electrode and the m-th conductor segment of the n-th sub-grounding electrode. Let be the current flowing into ground from the i-th sub-grounding electrode.

[0033] Optionally, the current-sharing resistance is adjusted according to the calculated current-sharing resistance value to adjust the ground current of each sub-grounding electrode until the sub-grounding electrodes in the deep well grounding electrode reach the optimal current-sharing state, including:

[0034] Construct the mutual resistance matrix between each sub-grounding electrode based on the calculated current sharing resistance value;

[0035] The solution of the mutual resistance matrix between each sub-grounding electrode is made to minimize the sum of the equivalent series resistance values ​​of all grounding conductor segments in the deep well grounding electrode, so that each sub-grounding electrode in the deep well grounding electrode reaches the optimal current sharing state.

[0036] Optionally, based on the current dissipation density at the ends of each sub-grounding electrode in the deep well grounding electrode, current sharing processing is performed on each sub-grounding electrode in the deep well grounding electrode, including:

[0037] For sub-grounding electrode portions in deep wells where the current density exceeds a threshold, the outer diameter of the target grounding conductor sheath steel pipe is determined based on the current density and target current density of the current sub-grounding electrode portion and the current density calculation model. The outer diameter of the grounding conductor sheath steel pipe corresponding to the current sub-grounding electrode portion is then replaced with the outer diameter of the target grounding conductor sheath steel pipe, where the target current density is below the threshold.

[0038] A second aspect of the present invention provides a deep well grounding electrode current sharing configuration system, comprising:

[0039] The current distribution detection module is used to detect the current distribution in each sub-grounding electrode in a deep well grounding electrode.

[0040] The single grounding electrode current sharing processing module is used to perform current sharing processing on each sub-grounding electrode in the deep well if the current distribution of each sub-grounding electrode in the deep well is uneven.

[0041] The sub-grounding electrode current sharing processing module is used to perform inter-electrode iterative current sharing processing on each sub-grounding electrode in the deep well grounding electrode when the current distribution of all sub-grounding electrodes in the deep well grounding electrode is uniform, until each sub-grounding electrode in the deep well grounding electrode reaches the optimal current sharing state.

[0042] As can be seen from the above technical solutions, the deep well grounding electrode current sharing configuration method provided by the present invention has the following advantages:

[0043] The deep well grounding electrode current sharing configuration method provided by this invention first detects whether the current distribution of each sub-grounding electrode in the deep well grounding electrode is uniform. If the current distribution is not uniform, current sharing processing is performed on each sub-grounding electrode based on the current dissipation density at the end of each sub-grounding electrode in the deep well grounding electrode. After the current distribution of all sub-grounding electrodes in the deep well grounding electrode is uniform, inter-electrode iterative current sharing processing is performed on each sub-grounding electrode until the sub-grounding electrodes in the deep well grounding electrode reach the optimal current sharing state. This can make the current dissipation density distribution on the DC deep well grounding electrode more uniform, reduce the maximum current dissipation density, reduce the grounding electrode temperature rise, and avoid damage to the deep well grounding electrode due to excessive current density. This solves the technical problem that existing deep well grounding electrodes are prone to failure due to excessive concentration of current dissipation, leading to failure and damage due to excessive current density. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a flowchart illustrating a method for configuring current sharing of a deep well grounding electrode according to an embodiment of the present invention.

[0046] Figure 2 This is a schematic diagram of the high-resistivity coating flow equalization measure provided in an embodiment of the present invention;

[0047] Figure 3 This is a flow uniformity effect diagram based on a high-resistivity coating provided in an embodiment of the present invention;

[0048] Figure 4 This is a schematic diagram of the current on the feeder cable of each sub-grounding electrode of the polygonal grounding electrode provided in this embodiment of the invention;

[0049] Figure 5 This is a schematic diagram of the flow equalization scheme under the polygonal asymmetric arrangement provided in the embodiments of the present invention;

[0050] Figure 6 The diagram shows the flow equalization effect based on diameter expansion provided in this embodiment of the invention.

[0051] Figure 7 This is a schematic diagram of a deep well grounding electrode current equalization configuration system provided in an embodiment of the present invention. Detailed Implementation

[0052] To enable those skilled in the art to better understand the present invention, 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. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] For easier understanding, please refer to Figure 1 This invention provides an embodiment of a deep well grounding electrode current sharing configuration method, comprising:

[0054] Step 101: Detect the current distribution of each sub-grounding electrode in the deep well grounding electrode.

[0055] It should be noted that deep well grounding electrodes typically consist of multiple individual sub-grounding electrodes, and the ground current must flow to each sub-grounding electrode via the feeder cable. Due to end effects and horizontal stratification of soil resistivity, the current distribution among individual sub-grounding electrodes is uneven. Furthermore, differences in soil conditions at the location of each sub-grounding electrode result in significant differences in the ground current flowing into each sub-grounding electrode. Some sub-grounding electrodes have excessively high maximum current density, while others have extremely low current density. Therefore, uneven current distribution occurs among the sub-grounding electrodes in a deep well grounding electrode. This embodiment mainly includes two steps for current sharing in the deep well grounding electrode. First, current sharing is performed on each individual sub-grounding electrode within the deep well grounding electrode. After the current sharing of each individual sub-grounding electrode is completed, current sharing is then performed among the sub-grounding electrodes in the deep well grounding electrode.

[0056] In this embodiment of the invention, the current distribution of each sub-grounding electrode in the deep well grounding electrode is first detected.

[0057] Step 102: If the current distribution of each sub-grounding electrode in the deep well grounding electrode is uneven, then the current sharing treatment shall be performed on each sub-grounding electrode in the deep well grounding electrode.

[0058] It should be noted that if the current distribution among the sub-grounding electrodes in the deep well grounding electrode is uneven, current sharing processing is performed on each sub-grounding electrode separately. In one embodiment, the uneven distribution of current density on a single sub-grounding electrode is caused by end effects and local low resistivity layers. Therefore, based on the current density at the ends of each sub-grounding electrode in the deep well grounding electrode, current sharing processing is performed on each sub-grounding electrode separately, including:

[0059] For the sub-grounding electrode portion in a deep well where the current density exceeds a threshold, the surface resistivity should be at least 10. A high-resistance coating is applied to the outside of the grounding conductor protective steel pipe of the deep well grounding electrode to suppress areas where the stray current density exceeds the threshold.

[0060] High-resistivity coatings are used at ends with excessively high flow density and in low-resistivity soil layers, such as... Figure 2 As shown, the high-resistivity layer reduces the area of ​​the grounding electrode with excessive current density, thereby achieving the goal of balancing the current density on the sub-grounding electrode. Specifically, the end effect causes the current density at the upper and lower ends of the sub-grounding electrode to be much greater than the average current density. Therefore, this embodiment of the invention considers using a high-resistivity coating on the protective steel pipes at the upper and lower ends to reduce the current density. Since the outer diameter of the protective steel pipe may vary with the drilling size, the coating resistance per unit length of the grounding electrode is used for description. That is, the formula for calculating the surface resistivity of the high-resistivity coating is:

[0061]

[0062] in, The resistivity of the high-resistivity coating per unit length of the deep well grounding electrode, in units of , The volume resistivity of the high-resistivity coating is expressed in units of... d represents the thickness of the high-resistivity coating in meters (m), and D represents the outer diameter of the grounding conductor sheathing steel pipe in meters (m). For practical engineering projects, the required coating resistance per unit length of the grounding electrode can be obtained by adjusting the appropriate coating thickness based on the resistivity of the selected material.

[0063] The grounding performance parameters of each sub-grounding electrode after applying high-resistivity coatings with different resistivity per unit length are shown in Table 1. The current sharing effect diagram based on the high-resistivity coating is shown in the figure. Figure 3 As shown.

[0064] Table 1

[0065]

[0066] As shown in Table 1, the high-resistivity coating will affect the current dissipation of the grounding electrode, which will lead to a slight increase in the grounding resistance. However, since the grounding electrode in the deep well is buried at a greater depth, it will not affect the grounding performance parameters such as the surface potential rise and step voltage. Figure 3 This indicates that using a high-resistivity coating at the end of a grounding electrode with excessive current dissipation can effectively reduce the maximum current dissipation density on the grounding electrode. As the coating resistance per unit length increases, the current dissipation density of the coated grounding conductor will decrease rapidly, while the current dissipation density of the uncoated grounding electrode will gradually increase. When the maximum current dissipation density of the coated grounding conductor is close to that of the uncoated conductor, it can be considered a reasonable current sharing configuration scheme.

[0067] In one embodiment, the threshold is determined based on the average current dissipation density of the deep well grounding electrode, and the formula for calculating the threshold is:

[0068]

[0069] in, For the threshold, The constant coefficient, The average current dissipation density of the deep well grounding electrode. In this embodiment of the invention, the threshold is taken as 1.05 to 1.20 times the average current dissipation density of the deep well grounding electrode, i.e. The value ranges from 1.05 to 1.20.

[0070] Step 103: When the current distribution of all sub-grounding electrodes in the deep well grounding electrode is uniform, perform inter-electrode iterative current sharing processing on each sub-grounding electrode in the deep well grounding electrode until each sub-grounding electrode in the deep well grounding electrode reaches the optimal current sharing state.

[0071] It should be noted that when the current distribution of all sub-grounding electrodes in the deep well grounding electrode is uniform, the inter-electrode iterative current sharing process is performed on each sub-grounding electrode in the deep well grounding electrode until each sub-grounding electrode in the deep well grounding electrode reaches the optimal current sharing state.

[0072] In one embodiment, with minimizing the maximum current dissipation density as the current sharing design objective, the current sharing resistance value of each sub-grounding electrode in the deep well grounding electrode is calculated based on the current asymmetric arrangement type of the deep well grounding electrode. The ground current of each sub-grounding electrode is adjusted according to the calculated current sharing resistance value until the sub-grounding electrodes in the deep well grounding electrode reach the optimal current sharing state. Asymmetric arrangement types of deep well grounding electrodes include linear, polygonal, and radial types. Specifically, with minimizing the maximum current dissipation density as the current sharing design objective, a current dissipation calculation model is constructed. A current sharing resistor is connected in series in the feeder cable, and the current shunting ratio between each sub-grounding electrode is adjusted. The current sharing resistance value of each sub-grounding electrode in the deep well grounding electrode is calculated according to the current dissipation calculation model. The current sharing resistance is adjusted according to the calculated current sharing resistance value to adjust the ground current of each sub-grounding electrode until the sub-grounding electrodes in the deep well grounding electrode reach the optimal current sharing state. The optimization objective of the current dissipation calculation model is:

[0073]

[0074] The constraints of the diffuse flow calculation model are:

[0075]

[0076]

[0077]

[0078]

[0079]

[0080] in, Let be the current dissipation density of the k-th conductor segment of the i-th sub-grounding electrode. Let be the potential of the m-th conductor segment of the n-th sub-grounding electrode. Let be the ground current of the k-th conductor segment of the i-th sub-grounding electrode. Let be the surface area of ​​the k-th conductor segment of the i-th sub-grounding electrode. Let be the equivalent series resistance value of the i-th sub-grounding electrode, and U be an N-dimensional column vector whose elements are all u. For the reason The diagonal matrix is ​​composed of u, where u is the voltage of the busbar at the center of the grounding electrode, R is an N×N matrix of mutual resistance between sub-grounding electrodes, and I is a matrix composed of The column vector formed Let be the mutual resistance between the k-th conductor segment of the i-th sub-grounding electrode and the m-th conductor segment of the n-th sub-grounding electrode. Let be the current flowing into ground from the i-th sub-grounding electrode.

[0081] The mutual resistance matrix R between each sub-grounding electrode is calculated based on the current dissipation calculation model:

[0082]

[0083] In the mutual resistance matrix R, the diagonal elements are the self-resistance of each sub-ground electrode, and the off-diagonal elements are the mutual resistance between the sub-ground electrodes.

[0084] The solution to the mutual resistance matrix between each sub-grounding electrode satisfies the condition that the sum of the equivalent series resistance values ​​of all grounding conductor segments in the deep well grounding electrode is minimized, i.e. This ensures that each sub-grounding electrode in the deep well grounding electrode achieves the optimal current sharing state.

[0085] When the number of grounding electrode segments is sufficiently large, and assuming that the current dissipation density is equal everywhere on each conductor segment, then:

[0086]

[0087] Therefore, the optimization objective of the diffused flow calculation model can be expressed as:

[0088]

[0089] Assuming there are N sub-grounding electrodes, the equivalent series resistance of the i-th sub-grounding electrode is... According to the basic principles of grounding current field and Ohm's law, the voltage u of the busbar at the center of the grounding electrode obtained from the i-th sub-grounding electrode is:

[0090]

[0091] Similarly, the voltage of the central busbar of the grounding electrode can be obtained sequentially from all N sub-grounding electrodes, resulting in the matrix equation:

[0092]

[0093] Divide each sub-grounding electrode into segments. Assuming each sub-grounding electrode is divided into M conductor segments, then:

[0094]

[0095] From the Green's function, we have:

[0096]

[0097] Solve for multiple solutions in the divergent flow computation model, based on The optimal solution to the matrix equation is obtained when the sum of the equivalent series resistances of all grounded conductor segments is minimized.

[0098] After solving the system of equations, the equivalent series resistance values ​​of each section of the grounding electrode can be obtained, and then the current-sharing resistance value that should be connected in series with each feeder cable can be obtained, which is the optimal combination of current-sharing resistances.

[0099] To analyze the current sharing effect based on current sharing resistors, this embodiment takes the asymmetrical arrangement of grounding electrodes in a broken-line deep well as an example to determine the current sharing resistor configuration scheme in which each sub-grounding electrode has the same grounding current.

[0100] For the asymmetrical arrangement model of the polygonal deep well grounding electrode, the current sharing scheme includes: equalizing the current density of the scattered current on each sub-grounding electrode (i.e., using 20mm steel pipes for the protective wall of the deep well grounding electrode in the ranges of 150~192m and 926~1000m). (after applying the high-resistivity coating), the mutual resistance matrix between each sub-ground electrode can be calculated as follows:

[0101]

[0102] Directly solving the above optimization model is quite difficult. To simplify the calculation, we consider the current-sharing resistance when the ground current flowing into each sub-grounding electrode is the same as the initial solution. Then, we iterate based on the ratio of the maximum current dissipation density on each sub-grounding electrode to obtain the optimal current-sharing resistance configuration. The combination of current-sharing resistances required to make the ground current flowing into each sub-grounding electrode the same is as follows:

[0103]

[0104] After adopting the above current sharing scheme, the grounding performance parameters of the grounding electrode and the current distribution of the current dissipation are shown in Table 2.

[0105] Table 2

[0106]

[0107] As shown in Table 2, the current sharing measures effectively improve the distribution ratio of ground current in each sub-grounding electrode and reduce the maximum current density of the deep well grounding electrode. The maximum current density is reduced from 5.42 A / m2 to 4.55 A / m2, a decrease of 16.1%. In addition, although the current sharing measures will increase the grounding resistance, they have almost no impact on grounding performance parameters such as surface potential distribution and step voltage.

[0108] like Figure 4 and Figure 5As shown, when the current flowing to each sub-grounding electrode is equal, due to the shielding effect, the maximum current density of the stray current on the middle sub-grounding electrode will be the largest. The ratio of the maximum current density of the stray current on each sub-grounding electrode is 4.346:4.547:4.527:4.547:4.346. To reduce the maximum current density of the middle sub-grounding electrode, we consider reducing the current proportionally, that is, considering that the current flowing to the ground on each sub-grounding electrode is distributed in the ratio of 615.8:588.6:591.2:588.6:615.8. Then the optimal current-sharing resistor combination can be calculated as follows:

[0109]

[0110] After adopting the above current sharing scheme, the current distribution ratio of each sub-grounding electrode can be effectively improved, and the maximum current density of the deep well grounding electrode can be reduced. The maximum current density is reduced from 5.52 A / m2 to 4.48 A / m2, a reduction of 18.4%. In summary, by using a high-resistance coating to balance the current density of each sub-grounding electrode (i.e., using a 20Ω·m high-resistance coating on the steel pipe of the deep well grounding electrode in the range of 150~192m and 926~1000m), and by using current sharing resistors to optimize the current distribution ratio of each sub-grounding electrode (i.e., connecting current sharing resistors of 31.1mΩ, 0mΩ, 5.8mΩ, 0mΩ, and 31.1mΩ in series on the feeder cable of the five sub-grounding electrodes respectively), current sharing can be achieved for the asymmetrical arrangement of the zigzag deep well grounding electrode, and the maximum current density of the grounding electrode can be reduced.

[0111] In one embodiment, based on the current dissipation density at the ends of each sub-grounding electrode in the deep well grounding electrode, another implementation method can be adopted to perform current sharing treatment on each sub-grounding electrode of the deep well grounding electrode:

[0112] For sub-grounding electrode portions in deep wells where the current dissipation density exceeds a threshold, the outer diameter of the target grounding conductor sheath steel pipe is determined based on the current dissipation density and the target current dissipation density of the current sub-grounding electrode portion, according to the current dissipation calculation model. The outer diameter of the grounding conductor sheath steel pipe corresponding to the current sub-grounding electrode portion is then replaced with the outer diameter of the target grounding conductor sheath steel pipe, where the target current dissipation density is below the threshold. This embodiment primarily uses a larger radius grounding conductor structure in grounding electrode portions with excessive current dissipation density to reduce the current dissipation density. Since deep well grounding electrodes are located in extremely deep boreholes, it is difficult to change the outer radius of the sheath steel pipe at the depth of the intermediate low-resistivity soil layer; therefore, this embodiment is applicable to deep well grounding electrode portions. Specifically, this embodiment mainly adopts measures to increase the radius of the grounding conductor for grounding electrodes with a current dissipation density greater than 3.57 A / m². Under the condition of the same current dissipation per unit length of grounding conductor, the current dissipation density of the grounding electrode is inversely proportional to the conductor radius; therefore, this embodiment expands the conductor radius to 4.25 / 3.57 = 1.19 times the previous value. The outer diameter of the protective steel pipes, totaling 35m in length and width (150-163m and 978-1000m), will be increased by 19% (because the location with the highest heat power is in the soil outside the protective steel pipe, it is necessary to reduce the diffusion density of the protective steel pipe, i.e., increase the outer diameter of the protective steel pipe). For example... Figure 6 As shown, after adopting the current sharing measure with diameter expansion, the grounding electrode resistance of a single sub-grounding electrode is 0.317Ω, the maximum ground potential rise is 43V, the maximum step voltage is 0.04V, the maximum current dissipation density is 3.60A / m², and the minimum current dissipation density is 2.94A / m². Unlike current sharing measures based on high-resistivity coatings, which lead to an increase in the current dissipation density of uncoated grounding electrodes, current sharing measures based on diameter expansion almost only affect the current dissipation of the grounding electrode within the range of the measures adopted. Therefore, in this embodiment, it is only necessary to expand the diameter of the excess portion according to the ratio of current dissipation density to safety limit based on the requirement of maximum current dissipation density.

[0113] In summary, uneven current distribution on a single sub-grounding electrode can be addressed by using a high-resistance coating on the outside of the protective steel pipe or by increasing the outer diameter of the protective steel pipe. Uneven current distribution among sub-grounding electrodes can be adjusted using current-sharing resistors. By combining current-sharing measures for individual sub-grounding electrodes with those among sub-grounding electrodes, the current-dissipating characteristics of deep well grounding electrodes can be significantly improved, resulting in a more uniform distribution of current on and among the sub-grounding electrodes. This not only reduces local temperature rise of the grounding electrode and minimizes gas production, but also improves the safety, stability, and operational reliability of the DC transmission system. Furthermore, this invention offers advantages such as simple construction and low cost, providing strong technical support for the widespread application of deep well grounding electrodes.

[0114] The deep well grounding electrode current sharing configuration method provided by this invention first detects whether the current distribution of each sub-grounding electrode in the deep well grounding electrode is uniform. If the current distribution is not uniform, current sharing processing is performed on each sub-grounding electrode based on the current dissipation density at the end of each sub-grounding electrode in the deep well grounding electrode. After the current distribution of all sub-grounding electrodes in the deep well grounding electrode is uniform, inter-electrode iterative current sharing processing is performed on each sub-grounding electrode until the sub-grounding electrodes in the deep well grounding electrode reach the optimal current sharing state. This can make the current dissipation density distribution on the DC deep well grounding electrode more uniform, reduce the maximum current dissipation density, reduce the grounding electrode temperature rise, and avoid damage to the deep well grounding electrode due to excessive current density. This solves the technical problem that existing deep well grounding electrodes are prone to failure due to excessive concentration of current dissipation, leading to failure and damage due to excessive current density.

[0115] For easier understanding, please refer to Figure 7 This invention provides an embodiment of a deep well grounding electrode current sharing configuration system, comprising:

[0116] The current distribution detection module is used to detect the current distribution in each sub-grounding electrode in a deep well grounding electrode.

[0117] The single grounding electrode current sharing processing module is used to perform current sharing processing on each sub-grounding electrode in the deep well if the current distribution of each sub-grounding electrode in the deep well is uneven.

[0118] The sub-grounding electrode current sharing processing module is used to perform inter-electrode iterative current sharing processing on each sub-grounding electrode in the deep well grounding electrode when the current distribution of all sub-grounding electrodes in the deep well grounding electrode is uniform, until each sub-grounding electrode in the deep well grounding electrode reaches the optimal current sharing state.

[0119] In one embodiment, based on the current dissipation density at the ends of each sub-grounding electrode in the deep well grounding electrode, current sharing processing is performed on each sub-grounding electrode in the deep well grounding electrode, including:

[0120] For the sub-grounding electrode portion in a deep well where the current density exceeds a threshold, the surface resistivity should be at least 10. A high-resistance coating is applied to the outside of the grounding conductor protective steel pipe of the deep well grounding electrode to suppress areas where the stray current density exceeds the threshold.

[0121] In one embodiment, the surface resistivity of the high-resistivity coating is calculated as follows:

[0122]

[0123] in, The resistivity of the high-resistivity coating per unit length of the deep well grounding electrode. d is the volume resistivity of the high-resistivity coating, d is the thickness of the high-resistivity coating, and D is the outer diameter of the grounding conductor sheath steel pipe.

[0124] In one embodiment, the threshold is:

[0125]

[0126] in, For the threshold, The constant coefficient, The average current density of the deep well grounding electrode.

[0127] In one embodiment, inter-electrode iterative current sharing processing is performed on each sub-grounding electrode in the deep well grounding electrode until each sub-grounding electrode in the deep well grounding electrode reaches the optimal current sharing state, including:

[0128] With minimizing the maximum current dissipation density as the current sharing design objective, the current sharing resistance value of each sub-grounding electrode in the deep well grounding electrode is calculated;

[0129] Adjust the ground current of each sub-grounding electrode according to the calculated current sharing resistance value until each sub-grounding electrode in the deep well reaches the optimal current sharing state.

[0130] In one embodiment, inter-electrode iterative current sharing processing is performed on each sub-grounding electrode in the deep well grounding electrode until each sub-grounding electrode in the deep well grounding electrode reaches the optimal current sharing state, including:

[0131] A flow distribution calculation model is constructed with the goal of minimizing the maximum flow density in the flow distribution design.

[0132] A current-sharing resistor is connected in series in the feeder cable, the current shunting ratio between each sub-grounding electrode is adjusted, and the current-sharing resistance value of each sub-grounding electrode in the deep well grounding electrode is calculated according to the current dissipation calculation model.

[0133] Adjust the current sharing resistance according to the calculated current sharing resistance value to adjust the ground current of each sub-grounding electrode until each sub-grounding electrode in the deep well grounding electrode reaches the optimal current sharing state.

[0134] In one embodiment, the optimization objective of the current distribution calculation model is:

[0135]

[0136] The constraints of the diffuse flow calculation model are:

[0137]

[0138]

[0139]

[0140]

[0141]

[0142] in, Let be the current dissipation density of the k-th conductor segment of the i-th sub-grounding electrode. Let be the potential of the m-th conductor segment of the n-th sub-grounding electrode. Let be the ground current of the k-th conductor segment of the i-th sub-grounding electrode. Let be the surface area of ​​the k-th conductor segment of the i-th sub-grounding electrode. Let be the equivalent series resistance value of the i-th sub-grounding electrode, and U be an N-dimensional column vector whose elements are all u. For the reason The diagonal matrix is ​​composed of u, where u is the voltage of the busbar at the center of the grounding electrode, R is an N×N matrix of mutual resistances between sub-grounding electrodes, and I is a matrix composed of The column vector formed Let be the mutual resistance between the k-th conductor segment of the i-th sub-grounding electrode and the m-th conductor segment of the n-th sub-grounding electrode. Let be the current flowing into ground from the i-th sub-grounding electrode.

[0143] In one embodiment, adjusting the current-sharing resistance based on the calculated current-sharing resistance value to adjust the ground current of each sub-grounding electrode until each sub-grounding electrode in the deep well grounding electrode reaches the optimal current-sharing state includes:

[0144] Construct the mutual resistance matrix between each sub-grounding electrode based on the calculated current sharing resistance value;

[0145] The solution of the mutual resistance matrix between each sub-grounding electrode is made to minimize the sum of the equivalent series resistance values ​​of all grounding conductor segments in the deep well grounding electrode, so that each sub-grounding electrode in the deep well grounding electrode reaches the optimal current sharing state.

[0146] In one embodiment, based on the current dissipation density at the ends of each sub-grounding electrode in the deep well grounding electrode, current sharing processing is performed on each sub-grounding electrode in the deep well grounding electrode, including:

[0147] For sub-grounding electrode portions in deep wells where the current density exceeds a threshold, the outer diameter of the target grounding conductor sheath steel pipe is determined based on the current density and target current density of the current sub-grounding electrode portion and the current density calculation model. The outer diameter of the grounding conductor sheath steel pipe corresponding to the current sub-grounding electrode portion is then replaced with the outer diameter of the target grounding conductor sheath steel pipe, where the target current density is below the threshold.

[0148] The deep well grounding electrode current sharing configuration system provided in this invention is used to execute the deep well grounding electrode current sharing configuration method provided in this invention. Its principle and the technical effects achieved are the same as those of the deep well grounding electrode current sharing configuration method provided in this invention, and will not be repeated here.

[0149] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for uniform current distribution of a deep well grounding electrode, characterized in that, include: Current distribution detection is performed on each sub-grounding electrode in the deep well grounding electrode; If the current distribution of each sub-grounding electrode in the deep well grounding electrode is not uniform, then based on the current dissipation density at the end of each sub-grounding electrode in the deep well grounding electrode, the current equalization treatment is performed on each sub-grounding electrode in the deep well grounding electrode. When the current distribution of all sub-grounding electrodes in the deep well grounding electrode is uniform, the inter-electrode iterative current sharing process is performed on each sub-grounding electrode in the deep well grounding electrode until each sub-grounding electrode in the deep well grounding electrode reaches the optimal current sharing state. Based on the current dissipation density at the ends of each sub-grounding electrode in the deep well grounding electrode, current sharing processing is performed on each sub-grounding electrode in the deep well grounding electrode, including: A high-resistance coating with a surface resistivity of at least 10 Ωm is applied to the outer side of the grounding conductor casing steel pipe of the deep-well grounding electrode in the end portion of the sub-grounding electrode where the current density exceeds the threshold value, to suppress the region where the current density exceeds the threshold value. Inter-electrode iterative current sharing processing is performed on each sub-grounding electrode in the deep well grounding electrode until the sub-grounding electrode in the deep well grounding electrode reaches the optimal current sharing state, including: A flow distribution calculation model is constructed with the goal of minimizing the maximum flow density in the flow distribution design. A current-sharing resistor is connected in series in the feeder cable, the current shunting ratio between each sub-grounding electrode is adjusted, and the current-sharing resistance value of each sub-grounding electrode in the deep well grounding electrode is calculated according to the current dissipation calculation model. Adjust the current sharing resistance according to the calculated current sharing resistance value to adjust the ground current of each sub-grounding electrode until each sub-grounding electrode in the deep well grounding electrode reaches the optimal current sharing state.

2. The deep well grounding electrode current sharing configuration method according to claim 1, characterized in that, The formula for calculating the surface resistivity of a high-resistivity coating is: in, The resistivity of the high-resistivity coating per unit length of the deep well grounding electrode. d is the volume resistivity of the high-resistivity coating, d is the thickness of the high-resistivity coating, and D is the outer diameter of the grounding conductor sheath steel pipe.

3. The deep well grounding electrode current sharing configuration method according to claim 1, characterized in that, The threshold is: in, For the threshold, The constant coefficient, The average current density of the deep well grounding electrode.

4. The deep well grounding electrode current sharing configuration method according to claim 1, characterized in that, The optimization objective of the current distribution calculation model is: The constraints of the diffuse flow calculation model are: in, Let be the current dissipation density of the k-th conductor segment of the i-th sub-grounding electrode. Let be the potential of the m-th conductor segment of the n-th sub-grounding electrode. Let be the ground current of the k-th conductor segment of the i-th sub-grounding electrode. Let be the surface area of ​​the k-th conductor segment of the i-th sub-grounding electrode. Let be the equivalent series resistance value of the i-th sub-grounding electrode, and U be an N-dimensional column vector whose elements are all u. For the reason The diagonal matrix is ​​composed of u, where u is the voltage of the busbar at the center of the grounding electrode, R is an N×N matrix of mutual resistance between sub-grounding electrodes, and I is a matrix composed of The column vector formed Let be the mutual resistance between the k-th conductor segment of the i-th sub-grounding electrode and the m-th conductor segment of the n-th sub-grounding electrode. Let be the current flowing into ground from the i-th sub-grounding electrode.

5. The deep well grounding electrode current sharing configuration method according to claim 4, characterized in that, Adjust the current-sharing resistance based on the calculated current-sharing resistance value to adjust the ground current of each sub-grounding electrode until the sub-grounding electrode in the deep well reaches the optimal current-sharing state, including: Construct the mutual resistance matrix between each sub-grounding electrode based on the calculated current sharing resistance value; The solution of the mutual resistance matrix between each sub-grounding electrode is made to minimize the sum of the equivalent series resistance values ​​of all grounding conductor segments in the deep well grounding electrode, so that each sub-grounding electrode in the deep well grounding electrode reaches the optimal current sharing state.

6. The deep well grounding electrode current sharing configuration method according to claim 4, characterized in that, Based on the current dissipation density at the ends of each sub-grounding electrode in the deep well grounding electrode, current sharing processing is performed on each sub-grounding electrode in the deep well grounding electrode, including: For sub-grounding electrode portions in deep wells where the current density exceeds a threshold, the outer diameter of the target grounding conductor sheath steel pipe is determined based on the current density and target current density of the current sub-grounding electrode portion and the current density calculation model. The outer diameter of the grounding conductor sheath steel pipe corresponding to the current sub-grounding electrode portion is then replaced with the outer diameter of the target grounding conductor sheath steel pipe, where the target current density is below the threshold.

7. A deep well grounding electrode current sharing configuration system, characterized in that, include: The current distribution detection module is used to detect the current distribution in each sub-grounding electrode in a deep well grounding electrode. The single grounding electrode current sharing processing module is used to perform current sharing processing on each sub-grounding electrode in the deep well if the current distribution of each sub-grounding electrode in the deep well is uneven. The sub-grounding electrode current sharing processing module is used to perform inter-electrode iterative current sharing processing on each sub-grounding electrode in the deep well grounding electrode when the current distribution of all sub-grounding electrodes in the deep well grounding electrode is uniform, until each sub-grounding electrode in the deep well grounding electrode reaches the optimal current sharing state. Based on the current dissipation density at the ends of each sub-grounding electrode in the deep well grounding electrode, current sharing processing is performed on each sub-grounding electrode in the deep well grounding electrode, including: For the sub-grounding electrode portion in a deep well where the current density exceeds a threshold, the surface resistivity should be at least 10. A high-resistance coating is applied to the outside of the grounding conductor protective steel pipe of the deep well grounding electrode to suppress areas where the current density exceeds the threshold. Inter-electrode iterative current sharing processing is performed on each sub-grounding electrode in the deep well grounding electrode until the sub-grounding electrode in the deep well grounding electrode reaches the optimal current sharing state, including: A flow distribution calculation model is constructed with the goal of minimizing the maximum flow density in the flow distribution design. A current-sharing resistor is connected in series in the feeder cable, the current shunting ratio between each sub-grounding electrode is adjusted, and the current-sharing resistance value of each sub-grounding electrode in the deep well grounding electrode is calculated according to the current dissipation calculation model. Adjust the current sharing resistance according to the calculated current sharing resistance value to adjust the ground current of each sub-grounding electrode until each sub-grounding electrode in the deep well grounding electrode reaches the optimal current sharing state.

Images