Planning and design method of mixed-voltage DC T-shaped branch terminal tower

Abstract

The application provides a mixed-voltage DC T-shaped branch terminal tower planning and design method, the mixed-voltage DC T-shaped branch terminal tower comprising a tower structure main body, a first conductor cross arm for bearing a first voltage grade line conductor, a second conductor cross arm for bearing a second voltage grade line conductor and a ground wire support arranged at the top of the tower structure main body. The ground wire support comprises a first ground wire support and a second ground wire support, the first ground wire support is arranged along the X-axis direction of the tower structure main body, and the second ground wire support is arranged along the Y-axis direction of the tower structure main body. The design method realizes a new terminal tower lightning protection planning scheme through the above structure, and the size design of the first ground wire support and the second ground wire support makes the lightning protection angle of the ground wire support to the line conductor meet the actual needs. The application can meet the lightning protection design requirements of the terminal tower under the extremely complex conditions of ±800kV+±400kV mixed voltage and branch terminal, and has high reliability and economy.

Description

Technical Field

[0001] This invention relates to the field of power transmission line technology, and more specifically, to a planning and design method for mixed-voltage DC T-shaped branch terminal towers. Background Technology

[0002] With the rapid development of the energy industry in Southwest China, ultra-high voltage direct current (UHVDC) transmission technology is usually required to achieve ultra-long-distance power transmission such as the West-to-East Power Transmission Project. As the transmission line industry has developed in recent years, UHVDC transmission technology has gradually matured. Due to the needs of system planning, the same substation often needs to output DC current of multiple voltage levels. However, due to the scarcity of land in high-altitude areas, there is usually only enough land for the construction of one converter station, which cannot take into account the tower foundation land occupied by the transmission line. Multiple DC lines are usually output from the same tower, which will greatly increase the land acquisition and construction costs, resulting in an increase of tens of millions of yuan in investment and poor economic benefits. Therefore, there is an urgent need to propose a multi-circuit mixed voltage branch terminal tower type.

[0003] However, unlike conventional multi-circuit mixed-voltage straight-line towers, tension towers, and terminal towers, mixed-voltage branch terminal towers have different structural requirements due to unilateral loading and branching. This multi-factor combination of mixed-voltage branch terminals has not been studied domestically or internationally, posing a significant challenge in engineering design. Especially when the outgoing lines of multiple levels have different directions, new challenges are presented to the lightning protection design of branch terminal towers. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems in the prior art: the lack of a design scheme for existing terminal towers that can meet the lightning protection requirements under DC mixed voltage conditions; the lightning protection design of existing terminal towers only takes into account the outgoing line level and lacks consideration of the actual operation of the line; when the design margin is small, it is difficult to meet the actual lightning protection requirements; when the design margin is too large, it will increase huge investments and cause waste of resources.

[0005] Therefore, the present invention provides a planning and design method for mixed-voltage DC T-shaped branch terminal towers.

[0006] This invention provides a planning and design method for a mixed-voltage DC T-shaped branch terminal tower, wherein the mixed-voltage DC T-shaped branch terminal tower includes:

[0007] The main tower structure is divided into an outgoing line side and a portal frame side based on the direction of outgoing lines.

[0008] The first conductor crossarm is installed on the main body of the tower structure to carry the conductors of the first voltage level line;

[0009] The second conductor crossarm is installed on the main body of the tower structure to carry the conductors of the second voltage level line. The first conductor crossarm and the second conductor crossarm are arranged along the Z-axis direction of the main body of the tower structure.

[0010] A grounding support is installed at the top of the main tower structure, including a first grounding support and a second grounding support. The first grounding support is arranged along the X-axis of the main tower structure, and the second grounding support is arranged along the Y-axis of the main tower structure. The two grounding wires of the first voltage level line on the outgoing side are respectively introduced to the portal frame side through the first grounding support and the second grounding support. The two grounding wires of the second voltage level line on the outgoing side are respectively introduced to the portal frame side through the first grounding support and the second grounding support.

[0011] Wherein, the first voltage level line has an outgoing line turning angle α1 relative to the main tower structure, and the second voltage level line has an outgoing line turning angle α2 relative to the main tower structure. The outgoing line turning angle is the angle between the line conductor and the plane perpendicular to the conductor crossarm.

[0012] The position where the ground wire on the outgoing side is hung on the second ground wire bracket is at a first distance LDY1 from the center of the main tower structure in the Y-axis direction. The first distance LDY1 is designed according to the following principles:

[0013]

[0014]

[0015] Wherein, LH1 represents the distance between the farthest connection point of the first voltage level line on the first conductor crossarm from the main body of the tower structure and the center of the main body of the tower structure; H1 represents the conductor-to-ground wire layer height, i.e., the vertical distance between the first conductor crossarm and the ground wire support; LH4 represents the vertical distance between the farthest connection point of the second voltage level line on the second conductor crossarm from the main body of the tower structure and the center of the main body of the tower structure; H2 represents the conductor layer height, i.e., the vertical distance between the first and second conductor crossarms; β is the lightning protection angle, i.e., the protection angle of the ground wire against the direction parallel to the conductor's outgoing line. In some embodiments, the tower height H0, i.e., the distance between the second conductor crossarm and the ground, can be determined according to actual usage conditions.

[0016] The hybrid DC T-shaped branch terminal tower planning and design method according to the above-described technical solution of the present invention may also have the following additional technical features:

[0017] In the above technical solution, the first conductor crossarm has a first and a second connection position for respectively connecting two conductors of a first voltage level line, and the second conductor crossarm has a third and a fourth connection position for respectively connecting two conductors of a second voltage level line; the first and second connection positions are located on both sides of the center of the main tower structure, and the third and fourth connection positions are located on both sides of the center of the main tower structure; there is a first pole spacing J1 between the first and second connection positions, and a second pole spacing J2 between the third and fourth connection positions;

[0018] The distance between the first attachment point and the center of the main tower structure in the X-axis direction is defined as the first attachment point distance LH1;

[0019] The distance between the second attachment point and the center of the main tower structure in the X-axis direction is defined as the second attachment point distance LH2;

[0020] The distance between the third attachment point and the center of the main tower structure in the X-axis direction is defined as the third attachment point distance LH3;

[0021] The distance between the fourth attachment point and the center of the main tower structure in the X-axis direction is defined as the fourth attachment point distance LH4;

[0022] Where J1 = LH1 + LH2, J2 = LH3 + LH4;

[0023] The design principles for the first pole spacing J1 and the second pole spacing J2 include: determining the lengths of the first pole spacing J1 and the second pole spacing J2 based at least on the line voltage level, altitude, and outgoing line turning angle.

[0024] In the above technical solution, the conductor on the outgoing side that tends to move away from the center of the main tower structure is defined as the outer corner conductor, and the conductor on the outgoing side that tends to move closer to the center of the main tower structure is defined as the inner corner conductor; the hanging position for hanging the inner corner conductor is the hanging position farthest from the center of the main tower structure.

[0025] The design principles for the distances from the first anchor point to LH1, the second anchor point to LH2, the third anchor point to LH3, and the fourth anchor point to LH4 include:

[0026]

[0027] LH2=J1-LH1≥Δd

[0028]

[0029] LH3=J2-LH4≥Δd

[0030] Where Δd is the minimum electrical clearance value.

[0031] In the above technical solution, the position of the first ground wire bracket connecting the ground wire of the second voltage level line and the center of the tower structure body in the X-axis direction has a first lightning protection distance LDX1, and the position of the first ground wire bracket connecting the ground wire of the first voltage level line and the center of the tower structure body in the X-axis direction has a second lightning protection distance LDX2; the first lightning protection distance LDX1 and the second lightning protection distance LDX2 are respectively located on both sides of the center of the tower structure body.

[0032] The design principles for the first lightning protection distance LDX1 and the second lightning protection distance LDX2 include:

[0033] LDX1≥LH3+(H1+H2)·tanβ

[0034] LDX2≥LH2+H1·tanβ.

[0035] In the above technical solution, each hanging position has at least two hanging points, and the distance between the two hanging points is defined as the hanging point spacing.

[0036] The design principles for hanging point spacing include:

[0037]

[0038]

[0039] Wherein, D1 represents the design value of the hanging point spacing at the corresponding hanging position of the first voltage level line; D2 represents the design value of the hanging point spacing at the corresponding hanging position of the first voltage level line; and D3 represents the reference value of the hanging point spacing at the corresponding hanging position of the second voltage level line.

[0040] In the above technical solution, the horizontal distance between any ground wire and the conductor of the first voltage level line is defined as the first horizontal offset value S0, and the horizontal distance between any ground wire and the conductor of the second voltage level line is defined as the second horizontal offset value S1. The design principles of the first horizontal offset value S0 and the second horizontal offset value S1 include:

[0041]

[0042]

[0043] Wherein, S0 represents the minimum permissible horizontal distance between the ground wire and the conductor of the first voltage level line, and S1 represents the minimum permissible horizontal distance between the ground wire and the conductor of the second voltage level line.

[0044] In the above technical solution, the design principles of the first electrode spacing J1 and the second electrode spacing J2 include:

[0045]

[0046]

[0047] Wherein, J1 represents the minimum allowable pole spacing determined by the line voltage level and altitude for the first voltage level line, and J2 represents the minimum allowable pole spacing determined by the line voltage level and altitude for the second voltage level line.

[0048] In the above technical solution, when the voltage level of the first voltage level line is higher than that of the second voltage level line, the first conductor crossarm is arranged above the second conductor crossarm.

[0049] In the above technical solution, the main body of the tower structure includes the tower body and the tower legs. The quasi-permanent deformation of the top of the branch terminal tower body in the X, Y, and Z directions is no greater than 7 / 1000 of the total height. The quasi-permanent deformation of the ends of the ground wire support, the first conductor crossarm, and the second conductor crossarm in the X, Y, and Z directions is no greater than 1 / 400 of the cantilever length.

[0050] In the above technical solution, the design principles for the minimum length of the first conductor crossarm and the second conductor crossarm include:

[0051] L H ≥2L1·sinθ / 2

[0052] Among them, L H L1 represents the minimum length of the conductor crossarm; L1 represents the length of the jumper V string on the conductor crossarm; θ represents the included angle of the V string.

[0053] In summary, due to the adoption of the above-mentioned technical features, the beneficial effects of the present invention are:

[0054] A planning and design method for mixed-voltage DC T-shaped branch terminal towers is provided. Through the newly designed terminal tower structure and the dimensional planning of each component in the terminal tower structure, the lightning protection design requirements of the terminal tower under the extremely complex conditions of ±800kV + ±400kV mixed voltage and branch terminals can be met. It has high reliability and economy, meets the actual needs of engineering, and has good economic and social benefits.

[0055] Additional aspects and advantages of the invention will become apparent in the following description or may be learned by practice of the invention. Attached Figure Description

[0056] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0057] Figure 1 This is a three-dimensional structural schematic diagram of a hybrid DC T-shaped branch terminal tower planning and design method according to an embodiment of the present invention;

[0058] Figure 2 This is a schematic diagram of the mixed-voltage branch line of a mixed-voltage DC T-shaped branch terminal tower planning and design method according to an embodiment of the present invention;

[0059] Figure 3 This is a schematic diagram showing the dimensions of a hybrid DC T-shaped branch terminal tower planning and design method according to an embodiment of the present invention.

[0060] in, Figures 1 to 3 The correspondence between the reference numerals and component names in the attached drawings is as follows:

[0061] 1. Tower body; 2. Tower leg; 3. First conductor crossarm; 4. Second conductor crossarm; 5. First ground wire bracket; 6. Second ground wire bracket; 7. Jumper V string. Detailed Implementation

[0062] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0063] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0064] The following reference Figures 1 to 3 This describes a mixed-voltage DC T-shaped branch terminal tower planning and design method provided according to some embodiments of the present invention.

[0065] Some embodiments of this application provide a method for planning and designing a mixed-voltage DC T-shaped branch terminal tower.

[0066] like Figures 1 to 3 As shown, the first embodiment of the present invention proposes a planning and design method for a mixed-voltage DC T-shaped branch terminal tower. The mixed-voltage DC T-shaped branch terminal tower includes: a tower structure body, a first conductor crossarm 3, a second conductor crossarm 4, and a ground wire support.

[0067] The main tower structure is divided into two sides: the outgoing line side and the portal frame side, based on the direction of the outgoing lines. It can be understood that the terminal tower, as the starting or ending point of the transmission line, is usually located near a power station or substation. The side of the terminal tower closer to the power station or substation is the portal frame side, used to bring the line into the station, while the side closer to the transmission line is the outgoing line side, used to lead the line out to the transmission line. An XYZ coordinate system is established based on the main tower structure.

[0068] The first conductor crossarm 3 is installed on the main body of the tower structure and is perpendicular to the main body of the tower structure, used to carry the conductors of the first voltage level line; the second conductor crossarm 4 is installed on the main body of the tower structure and is perpendicular to the main body of the tower structure, used to carry the conductors of the second voltage level line, and the first conductor crossarm 3 and the second conductor crossarm 4 are arranged along the Z-axis direction of the main body of the tower structure. Figure 1 The illustrated embodiment is used as an example for explanation. The first voltage level line is a ±800kV DC line, and the second voltage level line is a ±400kV DC line. It should be noted that each of these DC lines has two conductors and two ground wires. The two conductors of each line are respectively connected to both sides of the main tower structure. Specifically, the first conductor crossarm 3 is arranged above the second conductor crossarm 4 and is parallel to it.

[0069] The grounding bracket is located at the top of the main tower structure, at the very top of the terminal tower. It includes a first grounding bracket 5 and a second grounding bracket 6. The first grounding bracket 5 is arranged along the X-axis of the main tower structure, and the second grounding bracket 6 is arranged along the Y-axis of the main tower structure, meaning the first grounding bracket 5 and the second grounding bracket 6 are perpendicular to each other. Figure 2 As shown, the two ground wires on the outgoing side of the first voltage level line are introduced to the gantry side through the first ground wire bracket 5 and the second ground wire bracket 6, respectively; the two ground wires on the outgoing side of the second voltage level line are introduced to the gantry side through the first ground wire bracket 5 and the second ground wire bracket 6, respectively. Lightning protection for the branch terminal is achieved by adding a second ground wire bracket 6 in the Y-axis direction.

[0070] Wherein, the first voltage level line has an outgoing line angle α1 relative to the main tower structure, and the second voltage level line has an outgoing line angle α2 relative to the main tower structure. The outgoing line angle is the angle between the line conductor and the plane perpendicular to the conductor crossarm, i.e., the YOZ plane. It can be understood that the two conductors of the same line have the same outgoing line angle. The outgoing line angle varies with the orientation requirements of the line. In some embodiments, the outgoing line angle should not be greater than 45 degrees.

[0071] The position where the outgoing side ground wire is hung on the second ground wire bracket 6 is at a first distance LDY1 from the center of the main tower structure in the Y-axis direction. In a specific implementation, the position where the outgoing side ground wire is hung on the second ground wire bracket 6 is located at the end of the second ground wire bracket 6, and the first distance LDY1 represents the length of the second ground wire bracket 6.

[0072] Considering spatial projection relationships, the first distance LDY1 has the following design principles:

[0073]

[0074]

[0075] Wherein, LH1 represents the distance between the farthest connection point of the first voltage level line on the first conductor crossarm 3 and the center of the tower structure. When the first distance LDY1 can meet the lightning protection requirements of the farthest connection point of the first voltage level line, the other connection point of the first voltage level line can also meet the requirements; H1 represents the conductor-to-ground wire height, that is, the vertical distance between the first conductor crossarm 3 and the ground wire support. It can be understood that the first ground wire support 5 and the second ground wire support 6 can be located on the same horizontal plane or on different horizontal planes, but the value of H1 should be the distance between the first conductor crossarm 3 and the ground wire support 6. The minimum vertical distance between grounding wire supports is generally not less than 20m; LH4 represents the vertical distance between the farthest connection position of the second voltage level line on the second conductor crossarm 4 and the center of the tower structure. When the first distance LDY1 can meet the lightning protection requirements of the farthest connection position of the second voltage level line, the other connection position of the second voltage level line can also meet the requirements; H2 represents the conductor layer height, that is, the vertical distance between the first conductor crossarm 3 and the second conductor crossarm 4. The conductor layer height is controlled by the gap requirements between conductors of different voltage levels, and a margin of 2m needs to be considered. β is the lightning protection angle, that is, the protection angle of the grounding wire to the direction parallel to the conductor's outgoing line. It is understandable that the lightning protection angle does not refer to a specific actual angle, but rather a set value. The ground wires connected to the first ground wire bracket 5 and the second ground wire bracket 6, along with their corresponding line conductors, should all meet the requirements of the lightning protection angle. When only the first ground wire bracket 5 exists, a larger lightning protection angle is required. When there is a turning point in the line, the design requirements for the lightning protection angle will be further increased. In some cases, such as when the directions of two DC conductors are significantly different, the first ground wire bracket 5 in the X direction alone cannot provide lightning protection for conductors in both directions. Moreover, even if the directions of the two DC conductors are relatively similar, it can easily lead to the first ground wire bracket 5 being too long or the conductor crossarm being too long. Furthermore, under the constraint of the pole spacing (the distance between two conductors), the design margin can only be increased as much as possible to meet the lightning protection requirements, making it difficult to meet the needs of refined design. In this embodiment, by designing the second ground wire bracket 6, the lightning protection range of the ground wire bracket is increased, thereby reducing the requirement for the lightning protection angle, which makes the size design of the first ground wire bracket 5 and the second ground wire bracket 6 more reasonable. In one specific embodiment, the lightning protection angle β ≥ 10°. When the lightning protection requirements are higher, it can also be controlled at 15°, thereby obtaining the design length of the second grounding bracket 6. That is, the first distance LDY1 is designed according to the length that can simultaneously meet the lightning protection requirements of the first voltage level line and the second voltage level line.

[0076] The second embodiment of the present invention proposes a planning and design method for a mixed-voltage DC T-shaped branch terminal tower, and based on the first embodiment, as follows: Figure 3As shown, the first conductor crossarm 3 has a first connection position and a second connection position for respectively connecting two conductors of the first voltage level line, and the second conductor crossarm 4 has a third connection position and a fourth connection position for respectively connecting two conductors of the second voltage level line; the first connection position and the second connection position are respectively located on both sides of the center of the main body of the tower structure, and the third connection position and the fourth connection position are respectively located on both sides of the center of the main body of the tower structure; there is a first pole spacing J1 between the first connection position and the second connection position, and there is a second pole spacing J2 between the third connection position and the fourth connection position.

[0077] The distance between the first connection position and the center of the tower structure in the X-axis direction is defined as the first connection point distance LH1, which is the same as the distance LH1 between the connection position of the first voltage level line on the first conductor crossarm 3 farthest from the center of the tower structure and the center of the tower structure in the above embodiment; the distance between the second connection position and the center of the tower structure in the X-axis direction is defined as the second connection point distance LH2; the distance between the third connection position and the center of the tower structure in the X-axis direction is defined as the third connection point distance LH3; the distance between the fourth connection position and the center of the tower structure in the X-axis direction is defined as the fourth connection point distance LH4, which is the same as the distance LH4 between the connection position of the second voltage level line on the second conductor crossarm 4 farthest from the center of the tower structure and the center of the tower structure in the above embodiment;

[0078] Where J1 = LH1 + LH2, J2 = LH3 + LH4;

[0079] The design principles for the first pole spacing J1 and the second pole spacing J2 include: determining the lengths of the first pole spacing J1 and the second pole spacing J2 based at least on the line voltage level, altitude, and outgoing line turning angle.

[0080] In a specific implementation, the required pole spacing for an 800kV DC line is:

[0081] Below 1000m altitude, J1 ≥ 16m;

[0082] Altitude 1000m~2000m, J1≥18m;

[0083] Altitude 2000m~3000m, J1≥20m;

[0084] Altitude 3000m~4000m, J1≥22m;

[0085] Altitude 4000m~5000m, J1≥24m.

[0086] The required pole spacing for a 400kV DC line is:

[0087] Below 1000m altitude, J2 ≥ 14m;

[0088] Altitude 1000m~2000m, J2≥16m;

[0089] Altitude 2000m~3000m, J2≥18m;

[0090] Altitude 3000m~4000m, J2≥20m;

[0091] Altitude 4000m~5000m, J2≥22m;

[0092] However, due to the outgoing line angle, the actual first pole spacing J1 and second pole spacing J2 need to be adjusted according to the outgoing line angle, specifically:

[0093]

[0094]

[0095] Wherein, J1 represents the minimum allowable pole spacing determined by the line voltage level and altitude for the first voltage level line, and J2 represents the minimum allowable pole spacing determined by the line voltage level and altitude for the second voltage level line.

[0096] See again Figure 2 The conductor on the outgoing side that tends to move away from the center of the tower structure is defined as the outer corner conductor, such as... Figure 2 The 400kV conductor located to the left of the center of the main tower structure and the 800kV conductor located to the right of the center of the main tower structure are defined as the inner corner conductors, with the conductor on the outgoing side tending to be closer to the center of the main tower structure. Figure 2 The design includes a 400kV conductor located to the right of the tower structure's center and an 800kV conductor located to the left of the tower structure's center. The distance between the conductors and the tower structure is limited by the minimum electrical clearance value; that is, the distance between any point on the conductor and the tower structure must be greater than the minimum electrical clearance value. However, in traditional designs, only the horizontal direction of the conductor is considered, and the distance between the hanging point and the tower structure's center is configured to meet the minimum electrical clearance requirement. But for conductors with outgoing corners, on the outgoing side, the distance between the corresponding hanging point on the outer corner conductor and the tower structure's center meets the minimum electrical clearance requirement, and any point on the conductor also meets the requirement. However, while the distance between the corresponding hanging point on the inner corner conductor and the tower structure's center meets the minimum electrical clearance requirement, other points on the conductor may not. Therefore, the distance between the corresponding hanging point on the inner corner conductor and the tower structure's center should be greater. Thus, the hanging position for the inner corner conductor is the hanging position furthest from the tower structure's center.

[0097] Specifically, the design principles for the distances between the first attachment point and LH1, the second attachment point and LH2, the third attachment point and LH3, and the fourth attachment point and LH4 include:

[0098]

[0099] LH2=J1-LH1≥Δd

[0100]

[0101] LH3=J2-LH4≥Δd

[0102] Wherein, Δd is the minimum electrical clearance value. Through the above design, it can be ensured that, under the constraints of the distances between the four hanging points, the minimum electrical clearance value can be met at any point on either of the two conductors on the outgoing side.

[0103] In some embodiments, the dimensions of the first grounding bracket 5 are also designed. The position of the first grounding bracket 5 where the grounding wire of the second voltage level line is connected to the center of the tower structure body in the X-axis direction has a first lightning protection distance LDX1, and the position of the first grounding bracket 5 where the grounding wire of the first voltage level line is connected to the center of the tower structure body in the X-axis direction has a second lightning protection distance LDX2; the first lightning protection distance LDX1 and the second lightning protection distance LDX2 are respectively located on both sides of the center of the tower structure body; specifically, as shown... Figure 1 and Figure 3 As shown, when the ground wires of the two lines are directly connected to the two ends of the first ground wire bracket 5, the first lightning protection distance LDX1 can be regarded as the design length of the left side of the first ground wire bracket 5, and the second lightning protection distance LDX1 can be regarded as the design length of the right side of the second ground wire bracket 6.

[0104] Similarly, the two sides of the first grounding bracket 5 should respectively meet the requirements of the lightning protection angle limit. Therefore, the design principles of the first lightning protection distance LDX1 and the second lightning protection distance LDX2 include:

[0105] LDX1≥LH3+(H1+H2)·tanβ

[0106] LDX2≥LH2+H1·tanβ.

[0107] In some embodiments, the spacing between the hanging points of each conductor is also designed. The spacing between the hanging points of the conductors is affected by the type of electrical fittings and also by the bends in the line. Specifically, each hanging position has at least two hanging points, and the distance between the two hanging points is defined as the hanging point spacing.

[0108] After considering the impact of the outgoing cable angle, the design principles for the spacing between hanging points include:

[0109]

[0110]

[0111] Wherein, D1 represents the design value of the hanging point spacing for the corresponding connection position of the first voltage level line; D2 represents the reference value of the hanging point spacing for the corresponding connection position of the first voltage level line, that is, the hanging point spacing that should be used when the corresponding electrical fitting type is parallel to the line; D2 represents the design value of the hanging point spacing for the corresponding connection position of the second voltage level line; D2 represents the reference value of the hanging point spacing for the corresponding connection position of the second voltage level line, that is, the hanging point spacing that should be used when the corresponding electrical fitting type is parallel to the line.

[0112] In the above technical solution, the horizontal distance between any ground wire and the conductor of the first voltage level line is defined as the first horizontal offset value S0, and the horizontal distance between any ground wire and the conductor of the second voltage level line is defined as the second horizontal offset value S1. The design principles of the first horizontal offset value S0 and the second horizontal offset value S1 include:

[0113]

[0114]

[0115] Wherein, S0 represents the minimum permissible horizontal distance between the ground wire and the conductor of the first voltage level line. In a specific embodiment, the horizontal offset S0 between the ground wire and the ±800kV conductor should not be less than 1.75m; S1 represents the minimum permissible horizontal distance between the ground wire and the conductor of the second voltage level line. In a specific embodiment, the horizontal offset S0 between the ground wire and the ±400kV conductor should not be less than 2.25m.

[0116] Based on the above structure and planning, the design of the T-shaped mixed-voltage branch terminal structure can be completed, and the converter station outgoing line can be realized under narrow channel conditions.

[0117] The third embodiment of the present invention proposes a planning and design method for a mixed-voltage DC T-shaped branch terminal tower, and based on any of the above embodiments, such as... Figures 1 to 3 As shown, the main structure of the tower includes a tower body 1 and tower legs 2. The tower legs 2 can be either flat or of varying lengths to accommodate different terrains. The tower body 1 generally adopts a narrow-base tower design to reduce the floor space required and adapt to congested access routes. When using a narrow-base tower design, its deformation needs to be verified under wind speeds of 5 m / s, temperatures of 0°C, and icing thickness of 0 mm. The quasi-permanent deformation in the X, Y, and Z directions at the top of the branch terminal tower body 1 should not exceed 7 / 1000 of the total height, and the quasi-permanent deformation in the X, Y, and Z directions at the ends of the ground wire support, the first conductor crossarm 3, and the second conductor crossarm 4 should not exceed 1 / 400 of the cantilever length. Specifically:

[0118]

[0119]

[0120] Where, Δu X0 ,Δu Y0 ,Δu Z0 The X, Y, and Z quasi-permanent deformations at the top of branch terminal tower 1; H0 is the total height of the branch terminal tower; Δu X1 ,Δu Y1 ,Δu Z1 L0 represents the quasi-permanent deformation in the X, Y, and Z directions at the end of the grounding wire support and crossarm; L0 represents the cantilever length at the end of the grounding wire support and crossarm.

[0121] In some embodiments, the conductor crossarm should also meet the minimum string length requirement of the jumper V string 7. Therefore, the design principles for the minimum lengths of the first conductor crossarm 3 and the second conductor crossarm 4 also include:

[0122] L H ≥2L1·sinθ / 2

[0123] Among them, L H L1 represents the minimum length of the conductor crossarm; L1 represents the length of the jumper V string 7 on the conductor crossarm; θ represents the included angle of the V string.

[0124] In this specification, the illustrative expressions of the terms used do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0125] Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention shall be included within the scope of protection of this invention.

Claims

1. A method for planning and designing a mixed-voltage DC T-shaped branch terminal tower, characterized in that, The mixed-voltage DC T-shaped branch terminal tower includes: The main tower structure is divided into an outgoing line side and a portal frame side based on the direction of outgoing lines. The first conductor crossarm is installed on the main body of the tower structure to carry the conductors of the first voltage level line; The second conductor crossarm is installed on the main body of the tower structure to carry the conductors of the second voltage level line. The first conductor crossarm and the second conductor crossarm are arranged along the Z-axis direction of the main body of the tower structure. A grounding support is installed at the top of the main tower structure, including a first grounding support and a second grounding support. The first grounding support is arranged along the X-axis of the main tower structure, and the second grounding support is arranged along the Y-axis of the main tower structure. The two grounding wires of the first voltage level line on the outgoing side are respectively introduced to the portal frame side through the first grounding support and the second grounding support. The two grounding wires of the second voltage level line on the outgoing side are respectively introduced to the portal frame side through the first grounding support and the second grounding support. Wherein, the first voltage level line has an outgoing line angle α1 relative to the main tower structure, and the second voltage level line has an outgoing line angle α2 relative to the main tower structure. The outgoing line angle is the angle between the line conductor and the plane perpendicular to the conductor crossarm. The position where the ground wire on the outgoing side is hung on the second ground wire bracket is at a first distance LDY1 from the center of the main tower structure in the Y-axis direction. The first distance LDY1 is designed according to the following principles: Wherein, LH1 represents the distance between the farthest connection point on the first conductor crossarm of the first voltage level line from the main body of the tower structure and the center of the main body of the tower structure; H1 represents the conductor-ground wire layer height, i.e., the vertical distance between the first conductor crossarm and the ground wire support; LH4 represents the vertical distance between the farthest connection point on the second conductor crossarm of the second voltage level line from the main body of the tower structure and the center of the main body of the tower structure; H2 represents the conductor layer height, i.e., the vertical distance between the first conductor crossarm and the second conductor crossarm; β is the lightning protection angle, i.e., the protection angle of the ground wire to the direction parallel to the conductor's outgoing line.

2. The planning and design method for a mixed-voltage DC T-shaped branch terminal tower according to claim 1, characterized in that, The first conductor crossarm has a first and a second connection position for respectively connecting two conductors of a first voltage level line, and the second conductor crossarm has a third and a fourth connection position for respectively connecting two conductors of a second voltage level line; the first and second connection positions are located on both sides of the center of the main tower structure, and the third and fourth connection positions are located on both sides of the center of the main tower structure; there is a first pole spacing J1 between the first and second connection positions, and a second pole spacing J2 between the third and fourth connection positions; The distance between the first attachment point and the center of the main tower structure in the X-axis direction is defined as the first attachment point distance LH1; The distance between the second attachment point and the center of the main tower structure in the X-axis direction is defined as the second attachment point distance LH2; The distance between the third attachment point and the center of the main tower structure in the X-axis direction is defined as the third attachment point distance LH3; The distance between the fourth attachment point and the center of the main tower structure in the X-axis direction is defined as the fourth attachment point distance LH4; Where J1 = LH1 + LH2, J2 = LH3 + LH4; The design principles for the first pole spacing J1 and the second pole spacing J2 include: determining the lengths of the first pole spacing J1 and the second pole spacing J2 based at least on the line voltage level, altitude, and outgoing line turning angle.

3. The planning and design method for a mixed-voltage DC T-shaped branch terminal tower according to claim 2, characterized in that, The conductors on the outgoing side that tend to move away from the center of the main tower structure are defined as outer corner conductors, and the conductors on the outgoing side that tend to move closer to the center of the main tower structure are defined as inner corner conductors. The hanging position for hanging the inner corner side conductor is the hanging position farthest from the center of the main tower structure. The design principles for the distances from the first anchor point to LH1, the second anchor point to LH2, the third anchor point to LH3, and the fourth anchor point to LH4 include: LH2=J1-LH1≥Δd LH3=J2-LH4≥Δd Where Δd is the minimum electrical clearance value.

4. The planning and design method for a mixed-voltage DC T-shaped branch terminal tower according to claim 3, characterized in that, The position of the ground wire of the second voltage level line connected to the first ground wire bracket has a first lightning protection distance LDX1 in the X-axis direction between the center of the tower structure and the ground wire of the first voltage level line connected to the first ground wire bracket has a second lightning protection distance LDX2 in the X-axis direction between the center of the tower structure and the ground wire of the first voltage level line connected to the first ground wire bracket; the first lightning protection distance LDX1 and the second lightning protection distance LDX2 are located on both sides of the center of the tower structure, respectively. The design principles for the first lightning protection distance LDX1 and the second lightning protection distance LDX2 include: LDX1≥LH3+(H1+H2)·tanβ LDX2≥LH2+H1·tanβ.

5. The planning and design method for a mixed-voltage DC T-shaped branch terminal tower according to claim 2, characterized in that, Each attachment position has at least two attachment points, and the distance between the two attachment points is defined as the attachment point spacing. The design principles for hanging point spacing include: Wherein, D1 represents the design value of the hanging point spacing at the corresponding hanging position of the first voltage level line; D2 represents the design value of the hanging point spacing at the corresponding hanging position of the first voltage level line; and D3 represents the reference value of the hanging point spacing at the corresponding hanging position of the second voltage level line.

6. The planning and design method for a mixed-voltage DC T-shaped branch terminal tower according to claim 1, characterized in that, The horizontal distance between any ground wire and the conductor of the first voltage level line is defined as the first horizontal offset value S0, and the horizontal distance between any ground wire and the conductor of the second voltage level line is defined as the second horizontal offset value S1. The design principles for the first horizontal offset value S0 and the second horizontal offset value S1 include: Wherein, S0 represents the minimum permissible horizontal distance between the ground wire and the conductor of the first voltage level line, and S1 represents the minimum permissible horizontal distance between the ground wire and the conductor of the second voltage level line.

7. The planning and design method for a mixed-voltage DC T-shaped branch terminal tower according to claim 2, characterized in that, The design principles for the first electrode spacing J1 and the second electrode spacing J2 include: Wherein, J1 represents the minimum allowable pole spacing determined by the line voltage level and altitude for the first voltage level line, and J2 represents the minimum allowable pole spacing determined by the line voltage level and altitude for the second voltage level line.

8. The planning and design method for a mixed-voltage DC T-shaped branch terminal tower according to claim 1, characterized in that, When the voltage level of the first voltage level line is higher than that of the second voltage level line, the first conductor crossarm is arranged above the second conductor crossarm.

9. The planning and design method for a mixed-voltage DC T-shaped branch terminal tower according to claim 1, characterized in that, The main structure of the tower includes the tower body and tower legs. The quasi-permanent deformation in the X, Y, and Z directions at the top of the branch terminal tower body is no greater than 7 / 1000 of the total height. The quasi-permanent deformation in the X, Y, and Z directions at the ends of the ground wire support, the first conductor crossarm, and the second conductor crossarm is no greater than 1 / 400 of the cantilever length.

10. The planning and design method for a mixed-voltage DC T-shaped branch terminal tower according to claim 1, characterized in that, The design principles for the minimum lengths of the first and second conductor crossarms include: L H ≥2L1·sinθ2 Among them, L H L1 represents the minimum length of the conductor crossarm; L1 represents the length of the jumper V string on the conductor crossarm; θ represents the included angle of the V string.

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