Design method, device and equipment for changing alternating-current line to direct-current operation and medium

Abstract

The invention discloses a design method, device and equipment for changing an alternating-current line into direct-current operation and a medium, and belongs to the technical field of direct-current power transmission. The method comprises the following steps: replacing an alternating current insulator in a tangent tower lead suspension string with a direct current insulator, wherein the suspension string is a splayed suspension string; according to the operation voltage of the alternating current line, the direct current voltage and the insulator structure height and the air gap required value under the direct current voltage are preliminarily determined; calculating the deflection angle of the splayed suspension string and the air gap of the tower head of the tangent tower according to the structure height of the insulator and the parameters of the tangent tower; and the direct-current voltage is adjusted until the air gap of the tower head of the tangent tower does not have the problem of insufficient gap or overlarge margin. According to the design method provided by the invention, the improvement of the direct-current voltage and the power transmission capacity can be realized only by optimizing and adjusting the string type of the suspension string without large-scale transformation of an original line, and the design method has wide application prospects and important practical values.

Description

Technical Field

[0001] The invention belongs to the technical field of direct current transmission, and relates to a design method, device, equipment and medium for converting an alternating current line into a direct current line. Background Art

[0002] With the rapid development of smart grids, the conversion of AC lines to DC operation (abbreviated as "AC to DC") has become an important means to solve the bottleneck of power transmission and improve energy efficiency. The AC to DC technology has greatly reduced the cost of building new transmission lines by effectively utilizing the resources of existing transmission corridors, especially in areas where the contradiction between power supply and demand is prominent, effectively tapping the transmission potential and ensuring the stability and reliability of power supply. In addition, AC to DC eliminates the skin effect and capacitor charging current of AC power, significantly reduces the loss of power transmission, and improves energy efficiency. At the same time, the DC transmission system, with its unique flexibility and the characteristics of not relying on the synchronous operation of the AC system, can respond to load fluctuations and new energy access needs more quickly and accurately, providing strong support for the flexible construction and efficient operation of smart grids. How to improve the transmission capacity of the DC system, increase the transmission capacity of the AC to DC line, and efficiently utilize the existing transmission equipment resources, especially infrastructure such as poles and towers, has become an urgent problem to be solved in the power system. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a design method, device, equipment and medium for converting AC lines to DC operation, so as to effectively increase the DC voltage after the AC-to-DC conversion.

[0004] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0005] In a first aspect, the present invention provides a design method for converting AC lines to DC operation, comprising:

[0006] The AC insulators in the suspension string of the straight tower conductor are replaced with DC insulators, wherein the suspension string is an eight-shaped suspension string;

[0007] Based on the operating voltage of the AC line, preliminarily determine the DC voltage and the required values ​​of the insulator structure height and air gap under the DC voltage;

[0008] According to the insulator structure height and the straight tower parameters, the deflection angle of the figure eight suspension string and the air gap of the tower head of the straight tower are calculated;

[0009] Compared with the required air gap value, if the air gap of the straight tower head has a problem of insufficient gap or excessive margin, adjust the DC voltage, redetermine the insulator structure height and the required air gap value, and calculate the deflection angle of the figure-eight suspension string and the air gap of the straight tower head until the air gap of the straight tower head has a problem of insufficient gap or excessive margin.

[0010] Furthermore, the deflection angle of the figure eight suspension string is calculated, including:

[0011] Calculate the maximum required deflection angle and the maximum allowable deflection angle of the figure eight suspension string;

[0012] The deflection angle of the figure-eight suspension string is the smaller value between the maximum required deflection angle and the maximum allowed deflection angle.

[0013] Furthermore, the maximum required deflection angle of the figure eight suspension string The calculation formula is:

[0014] ,

[0015] in, is the downward inclination angle of the conductor at the suspension clamp; It is the vertical distance between the wire hanging point and the electrical control surface; is the width of the electrical control surface; It is the distance between the double hanging points of the figure eight suspension string; is the length of the branch string of the figure eight suspension string, The insulator structure height is obtained based on the insulator.

[0016] Furthermore, the maximum allowable deflection angle of the figure eight suspension string is The calculation formula is:

[0017] ,

[0018] in, is the permissible gripping force of the suspension wire clamp; is the wire tension at the suspension point.

[0019] Furthermore, the air gap of the straight tower head The calculation formula is:

[0020] ,

[0021] in, It is the deflection angle of the figure eight suspension string.

[0022] Further, it also includes: evaluating the improvement effect of using a figure-eight suspension string on the air gap;

[0023] Air gap between conductors and electrical control surface when using a single suspension string for:

[0024] ,

[0025] When using the figure eight suspension string, the air gap between the conductor and the electrical control surface is , the improvement effect of using figure eight suspension string on the air gap is:

[0026] .

[0027] Further, if the air gap of the tower head of the straight tower has a problem of insufficient gap or excessive margin, the DC voltage is adjusted, the insulator structure height and the required air gap value are re-determined, and the deflection angle of the figure-eight suspension string and the air gap of the tower head of the straight tower are calculated until the air gap of the tower head of the straight tower has no problem of insufficient gap or excessive margin, including:

[0028] If the air gap of the tower head of the linear tower exceeds the required air gap value by more than 2% of the required air gap value, the DC voltage is increased by a preset gradient value;

[0029] Based on the increased DC voltage, the insulator structure height and air gap requirement are re-determined, and the corresponding figure-eight suspension string deflection angle and the air gap of the tower head of the straight tower are calculated, until the part of the air gap of the tower head of the straight tower that exceeds the air gap requirement value does not exceed 2% of the air gap requirement value;

[0030] The current DC voltage is reduced by the gradient value as the final DC voltage.

[0031] In a second aspect, the present invention further provides a design device for converting an AC line to a DC line, the device comprising:

[0032] A suspension string structure determination module, used for replacing AC insulators in a straight tower conductor suspension string with DC insulators, wherein the suspension string adopts a figure-eight suspension string;

[0033] A DC voltage preliminary determination module is used to preliminarily determine the DC voltage and the required values ​​of the insulator structure height and air gap under the DC voltage according to the operating voltage of the AC line;

[0034] A suspension string deflection angle and air gap calculation module is used to calculate the deflection angle of the figure eight suspension string and the air gap of the tower head of the straight tower according to the insulator structure height and the parameters of the straight tower;

[0035] The DC voltage and suspension string deflection adjustment module is used to compare with the required air gap value. If the air gap of the straight tower head is insufficient or the margin is too large, the DC voltage is adjusted, the insulator structure height and the required air gap value are re-determined, and the deflection angle of the figure-eight suspension string and the air gap of the straight tower head are calculated until the air gap of the straight tower head is no longer insufficient or has no longer margin.

[0036] In a third aspect, the present invention further provides a computer device, comprising:

[0037] Memory for storing computer programs;

[0038] A processor is used to execute the computer program to implement the steps of the above-mentioned design method for converting AC line to DC operation.

[0039] In a fourth aspect, the present invention further provides a computer-readable storage medium having a computer program stored thereon, the program being executed by a processor to implement the steps of the above-mentioned design method for converting AC line to DC operation

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The design method for converting AC lines to DC operation provided by the present invention can make full use of existing transmission equipment resources such as poles and towers without increasing additional transmission corridor resources, making power transmission more economical and efficient while reducing the impact on the environment; the present invention optimizes the string arrangement of the suspension strings, adopts a double independent figure-eight structure, and scientifically and reasonably configures the deflection angle of the figure-eight suspension strings, effectively reducing the impact of the conductor downward tilt on the electrical distance, improving the safety performance of the line, not only helping to ensure the stability of power transmission, but also further improving energy utilization efficiency; after the AC line is converted to DC operation, the DC voltage can be further increased by gradually adjusting and optimizing the DC voltage, thereby achieving a significant improvement in the line transmission capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic diagram of the structure of a DC tower in an embodiment of the present invention

[0043] Figure 2 A schematic flow chart of a design method for converting AC lines to DC operation provided by an embodiment of the present invention;

[0044] Figure 3 It is a schematic diagram of the structure of the figure eight suspension string in an embodiment of the present invention;

[0045] Figure 4 A schematic diagram of the structure of a design device for converting an AC line to a DC line according to an embodiment of the present invention;

[0046] Figure 5 An internal structure diagram of a computer device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is described in detail below through the accompanying drawings and specific embodiments. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. The embodiments of the present application and the specific features in the embodiments are detailed descriptions of the technical solution of the present application, rather than limitations on the technical solution of the present application. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments can be combined with each other.

[0048] The term "and / or" in this article is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0049] Embodiment 1:

[0050] like Figure 1 As shown, the straight tower is the most commonly used tower type for power transmission lines, and is used to bear the gravity of the conductor. The straight tower includes an upper cross arm, a middle cross arm and a lower cross arm of the conductor, and a conductor suspension string on each cross arm. The suspension string is installed on the conductor cross arm through a suspension wire clamp. The conductor cross arm is used to support and suspend the wire. The suspension string isolates the wire from the tower to prevent the current from directly flowing into the tower, thereby ensuring the safe operation of the wire. In order to make full use of the existing power transmission equipment, the present invention converts the AC transmission line into a DC transmission line without modifying the existing straight tower and conductor of the AC line.

[0051] The embodiment of the present invention is Figure 1 The upper cross arm shown is taken as an example to explain the design method of the present invention.

[0052] like Figure 2 and Figure 3 As shown, an embodiment of the present invention provides a design method for converting an AC line to DC operation. Figure 2 The flowchart is a schematic diagram of the design method for converting the AC line to DC operation. This flowchart only shows the logical sequence of the method described in this embodiment. Under the premise of no conflict, in other possible embodiments of the present invention, different Figure 2 The steps shown or described are accomplished in the order shown.

[0053] The design method for converting an AC line to DC operation provided in this embodiment can be applied to a terminal, and can be executed by a design device for converting an AC line to DC operation, which can be implemented by software and / or hardware, and can be integrated in a terminal.

[0054] See also Figure 2 The method of the embodiment of the present invention specifically includes the following steps 1 to 4. Among them:

[0055] Step 1: Replace the AC insulators in the straight tower conductor suspension string with DC insulators, wherein the suspension string is a figure-eight suspension string.

[0056] Unlike AC transmission lines, high-voltage DC lines are more susceptible to electrochemical corrosion in humid environments than AC voltages. The electrochemical corrosion of insulators affects the electrical insulation strength and mechanical tolerance of the insulator string, resulting in a decrease in the pollution withstand voltage and mechanical damage load. The original AC insulators are difficult to meet the long-term safe and stable operation of DC lines. Therefore, the AC insulators in the suspension string of the straight tower conductor need to be replaced with DC insulators.

[0057] like Figure 3 As shown, the present invention adopts an eight-shaped suspension string, two branches of the eight-shaped suspension string are respectively composed of suspension strings, and the same electric wire is hung at the bottom of the two suspension strings.

[0058] Step 2: Based on the operating voltage of the AC line, preliminarily determine the DC voltage and the required insulator structure height and air gap under this DC voltage.

[0059] In order to maximize the use of existing power transmission line resources, we hope that the DC operating voltage after "AC to DC" is as large as possible. Therefore, the DC voltage of the present invention represents the maximum voltage that can be transmitted by the DC line.

[0060] According to the operating voltage of the AC line, the maximum voltage level that the DC line can transmit can be preliminarily determined. The specific calculation formula is as follows:

[0061] ,

[0062] in, is the maximum voltage level of the DC line, is the operating voltage of the AC line.

[0063] The embodiment of the present invention adopts the creepage distance method to calculate the configuration of the DC insulator string:

[0064] Define the DC nominal voltage as U, the equivalent salt density as ESDD, and the DC line creepage distance as ;

[0065] For the DC composite insulator used in the present invention, the creepage distance per unit length is When the dry arc distance is The height of the insulator structure can be determined based on the dry arc distance.

[0066] The air gap includes the air gap of the DC line under working voltage, operation, lightning and live working conditions, which is generally obtained based on the DC discharge test.

[0067] Step 3: Calculate the deflection angle of the figure-eight suspension string and the air gap of the tower head of the straight tower according to the height of the insulator structure and the parameters of the straight tower.

[0068] Among them, in the embodiment of the present invention, the straight tower parameters include: the vertical distance between the wire hanging point and the electrical control surface , width of electrical control surface , the distance between the double hanging points of the figure eight suspension string , the length of the branch string of the figure eight suspension string , allowable gripping force of suspension wire clamp , the wire tension at the hanging point wait.

[0069] like Figure 1 As shown, in the embodiment of the present invention, the electrical control surface is the plane formed by the middle cross arm, and the width of the electrical control surface is the width of the middle cross arm.

[0070] The suspension string is composed of suspension wire clamps, connecting hardware, insulators and other components. Therefore, the length of the suspension string is It consists of the height of the insulator structure plus the fixed length of the suspension wire clamp and connecting hardware.

[0071] In order to lift the lower conductor away from the lower cross arm electrical control surface, the maximum required deflection angle of the figure eight suspension string The calculation formula is:

[0072] ,

[0073] in, It is the downward inclination angle of the conductor at the suspension clamp.

[0074] In order to ensure that the longitudinal unbalanced tension of the conductor on the suspension clamp does not exceed the allowable gripping force of the suspension clamp, the maximum allowable deflection angle of the figure-eight suspension string is The calculation formula is:

[0075] ,

[0076] The deflection angle of the figure eight suspension string The smaller value of the maximum required deflection angle and the maximum allowable deflection angle of the figure-eight suspension string. .

[0077] The air gap of the straight tower head , which is the air gap between the conductor and the electrical control surface, and its calculation formula is:

[0078] ,

[0079] in, It is the deflection angle of the figure eight suspension string.

[0080] By comparing the air gap between the conductor and the electrical control surface in a single suspension string, the improvement effect of the figure-eight suspension string on the air gap in the present invention can be evaluated.

[0081] Air gap between conductors and electrical control surface when using a single suspension string for:

[0082] ,

[0083] When using the figure eight suspension string, the air gap between the conductor and the electrical control surface is , then the improvement effect of the air gap by using the figure-eight suspension string in the present invention is:

[0084] .

[0085] The present invention optimizes the suspension string arrangement through the suspension strings of double independent figure-eight structures and scientifically and reasonably configures the deflection angle of the figure-eight suspension strings, thereby effectively reducing the influence of the downward tilt of the conductor on the electrical distance and improving the safety performance of the line. It not only helps to ensure the stability of power transmission, but also further improves the energy utilization efficiency.

[0086] Step 4: Compare with the required air gap value. If the air gap of the straight tower head is insufficient or has too much margin, adjust the DC voltage, redetermine the insulator structure height and the required air gap value, and calculate the deflection angle of the figure-eight suspension string and the air gap of the straight tower head until the air gap of the straight tower head is no longer insufficient or has too much margin.

[0087] The deflection angle of the figure-eight suspension string adjusted by the preliminarily determined DC voltage and the air gap of the tower head of the straight tower calculated therefrom often have a problem of excessive margin. Therefore, in the embodiment of the present invention, if the portion of the air gap of the tower head of the straight tower exceeds the required air gap value by more than 2% of the required air gap value, the DC voltage is increased by a preset gradient value. Based on the increased DC voltage, the insulator structure height and the required air gap value are re-determined, and the corresponding deflection angle of the figure-eight suspension string and the air gap of the tower head of the straight tower are calculated until the portion of the air gap of the tower head of the straight tower exceeds the required air gap value by no more than 2% of the required air gap value. At this time, the current DC voltage is reduced by a gradient value as the final DC voltage.

[0088] The gradient value is generally set to 5kV or 10kV.

[0089] Obtain the final DC voltage, as well as the insulator structure height, air gap requirement, figure-eight-shaped suspension string deflection angle and straight tower head air gap under the DC voltage, and set the suspension string according to the obtained insulator structure height and figure-eight-shaped suspension string deflection angle.

[0090] Taking a 500kV AC line straight tower as an example to explain the design method of the present invention, the parameters of the straight tower include: the vertical distance between the conductor hanging point and the electrical control surface The width of the electrical control surface is 9.5m 3.4m, the distance between the double hanging points of the figure eight suspension string 0.6m, the length of the branch string of the figure eight suspension string The allowable gripping force of the suspension wire clamp is 5.9m. The wire tension at the hanging point is 28585N. 57171N, the conductor downward inclination angle at the suspension clamp The angle is 15°, and the standard DC voltage determined by the AC to DC conversion is 360kV.

[0091] The maximum required deflection angle of the figure eight suspension string calculated initially by the above formula The maximum allowable deflection angle is 25.2° is 61.0°, and then the deflection angle of the figure eight suspension string is determined The air gap improvement effect after using the figure eight suspension string is calculated. It is 1.39m.

[0092] At this time, the calculated air gap of the tower head is 4.91, which is too large compared with the required air gap value of 3.42. It needs to be adjusted by increasing the DC voltage by 10kV as a gradient for iterative calculation. The AC DC voltage level and iterative calculation results under different calculation steps are shown in the following table:

[0093]

[0094] The air gap of the tower head of the straight tower obtained by the 8th calculation is 3.78. Compared with the required air gap value of 3.81, there is no problem of excessive margin. Therefore, the DC voltage is restored to the value before the 8th calculation, that is, the values ​​obtained by the 7th calculation are the final results. It can be seen that the maximum voltage of the AC-to-DC conversion after the use of the figure-eight suspension string can be increased from 360kV to 420kV. Under the premise of basically no increase in investment, the transmission voltage and transmission capacity increase by 16.7%. At this time, the figure-eight string deflection angle is 21.3°.

[0095] Embodiment 2:

[0096] Based on the same inventive concept as in Example 1, the embodiment of the present invention further provides a design device for converting AC line to DC operation for implementing the design method for converting AC line to DC operation. The implementation scheme for solving the problem provided by the device is similar to the implementation scheme recorded in the above method, so the specific limitations in the embodiment of the design device for converting AC line to DC operation provided below can refer to the limitations of the design method for converting AC line to DC operation above, and will not be repeated here.

[0097] like Figure 4 As shown, an embodiment of the present invention provides a design device for converting AC line to DC operation, comprising:

[0098] A suspension string structure determination module, used for replacing AC insulators in a straight tower conductor suspension string with DC insulators, wherein the suspension string adopts a figure-eight suspension string;

[0099] A DC voltage preliminary determination module is used to preliminarily determine the DC voltage and the required values ​​of the insulator structure height and air gap under the DC voltage according to the operating voltage of the AC line;

[0100] A suspension string deflection angle and air gap calculation module is used to calculate the deflection angle of the figure eight suspension string and the air gap of the tower head of the straight tower according to the insulator structure height and the parameters of the straight tower;

[0101] The DC voltage and suspension string deflection adjustment module is used to compare with the required air gap value. If the air gap of the straight tower head is insufficient or the margin is too large, the DC voltage is adjusted, the insulator structure height and the required air gap value are re-determined, and the deflection angle of the figure-eight suspension string and the air gap of the straight tower head are calculated until the air gap of the straight tower head is no longer insufficient or has no longer margin.

[0102] Embodiment 3:

[0103] The embodiment of the present invention further provides a computer device, which may be a server, and its internal structure diagram may be as shown in FIG. Figure 5 As shown. The computer device includes a processor, a memory, an input / output interface (Input / Output, referred to as I / O) and a communication interface. The processor, the memory and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, the design method of converting the AC line to DC operation in the aforementioned embodiment is implemented.

[0104] Those skilled in the art will understand that Figure 5 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0105] Embodiment 4:

[0106] The embodiment of the present invention further provides a computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, the steps of the following method are implemented:

[0107] The AC insulators in the suspension string of the straight tower conductor are replaced with DC insulators, wherein the suspension string is an eight-shaped suspension string;

[0108] Based on the operating voltage of the AC line, preliminarily determine the DC voltage and the required values ​​of the insulator structure height and air gap under the DC voltage;

[0109] According to the insulator structure height and the straight tower parameters, the deflection angle of the figure eight suspension string and the air gap of the tower head of the straight tower are calculated;

[0110] Compared with the required air gap value, if the air gap of the straight tower head has a problem of insufficient gap or excessive margin, adjust the DC voltage, redetermine the insulator structure height and the required air gap value, and calculate the deflection angle of the figure-eight suspension string and the air gap of the straight tower head until the air gap of the straight tower head has a problem of insufficient gap or excessive margin.

[0111] It should be understood by those skilled in the art that the embodiments of the present invention may be provided as methods, systems, or computer program products, and therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0112] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0113] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0114] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0115] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which all fall within the protection of the present invention.

Claims

1. A design method for converting AC lines to DC operation, characterized in that: include: The AC insulators in the suspension string of the straight tower conductor are replaced with DC insulators, wherein the suspension string is an eight-shaped suspension string; Based on the operating voltage of the AC line, preliminarily determine the DC voltage and the required values ​​of the insulator structure height and air gap under the DC voltage; According to the insulator structure height and the straight tower parameters, the deflection angle of the figure eight suspension string and the air gap of the tower head of the straight tower are calculated; Compared with the required air gap value, if the air gap of the straight tower head has a problem of insufficient gap or excessive margin, adjust the DC voltage, redetermine the insulator structure height and the required air gap value, and calculate the deflection angle of the figure-eight suspension string and the air gap of the straight tower head until the air gap of the straight tower head has a problem of insufficient gap or excessive margin.

2. The design method for converting AC lines to DC operation according to claim 1, characterized in that: Calculate the deflection angle of the figure eight suspension string, including: Calculate the maximum required deflection angle and the maximum allowable deflection angle of the figure eight suspension string; The deflection angle of the figure-eight suspension string is the smaller value between the maximum required deflection angle and the maximum allowed deflection angle.

3. The design method for converting AC lines to DC operation according to claim 2, characterized in that: The maximum required deflection angle of the figure eight suspension string The calculation formula is: ， in, is the downward inclination angle of the conductor at the suspension clamp; It is the vertical distance between the wire hanging point and the electrical control surface; is the width of the electrical control surface; It is the distance between the double hanging points of the figure eight suspension string; is the length of the branch string of the figure eight suspension string, The insulator structure height is obtained based on the insulator.

4. The design method for converting AC lines to DC operation according to claim 3 is characterized in that: The maximum allowable deflection angle of the figure eight suspension string The calculation formula is: ， in, is the permissible gripping force of the suspension wire clamp; is the wire tension at the suspension point.

5. The design method for converting AC lines to DC operation according to claim 4, characterized in that: The air gap of the straight tower head The calculation formula is: ， in, It is the deflection angle of the figure eight suspension string.

6. The design method for converting AC lines to DC operation according to claim 5, characterized in that: Also includes: Evaluate the improvement effect of using figure eight suspension strings on air gap; Air gap between conductors and electrical control surface when using a single suspension string for: ， When using the figure eight suspension string, the air gap between the conductor and the electrical control surface is , the improvement effect of using figure eight suspension string on the air gap is: 。 7. The design method for converting AC lines to DC operation according to claim 1, characterized in that: If the air gap of the tower head of the straight tower is insufficient or has too much margin, adjust the DC voltage, redefine the insulator structure height and the required air gap value, and calculate the deflection angle of the figure-eight suspension string and the air gap of the tower head of the straight tower until the air gap of the tower head of the straight tower is not insufficient or has too much margin, including: If the air gap of the tower head of the linear tower exceeds the required air gap value by more than 2% of the required air gap value, the DC voltage is increased by a preset gradient value; Based on the increased DC voltage, the insulator structure height and air gap requirement are re-determined, and the corresponding figure-eight suspension string deflection angle and the air gap of the tower head of the straight tower are calculated, until the part of the air gap of the tower head of the straight tower that exceeds the air gap requirement value does not exceed 2% of the air gap requirement value; The current DC voltage is reduced by the gradient value as the final DC voltage.

8. A design device for converting AC lines to DC operation, characterized in that: include: A suspension string structure determination module, used for replacing AC insulators in a straight tower conductor suspension string with DC insulators, wherein the suspension string adopts a figure-eight suspension string; A DC voltage preliminary determination module is used to preliminarily determine the DC voltage and the required values ​​of the insulator structure height and air gap under the DC voltage according to the operating voltage of the AC line; A suspension string deflection angle and air gap calculation module is used to calculate the deflection angle of the figure eight suspension string and the air gap of the tower head of the straight tower according to the insulator structure height and the parameters of the straight tower; The DC voltage and suspension string deflection adjustment module is used to compare with the required air gap value. If the air gap of the straight tower head is insufficient or the margin is too large, the DC voltage is adjusted, the insulator structure height and the required air gap value are re-determined, and the deflection angle of the figure-eight suspension string and the air gap of the straight tower head are calculated until the air gap of the straight tower head is no longer insufficient or has no longer margin.

9. A computer device, characterized in that: include: Memory for storing computer programs; A processor is used to execute the computer program to implement the steps of the design method for converting AC line to DC operation according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the design method for converting an AC line to DC operation according to any one of claims 1 to 7 are implemented.

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