Method for rebuilding cable terminal leading-down structure based on built overhead transmission line

Abstract

The invention relates to the technical field of high-voltage power transmission lines, in particular to a method for reconstructing a cable terminal leading-down structure based on a built overhead power transmission line, which comprises the following steps of: removing redundant wire cross arms on a main rod of a built steel pipe rod, newly adding an upper wire leading-down cross arm, a middle wire leading-down cross arm and a cable terminal equipment cross arm; newly adding a platform plate, a first cable clamp cross arm and a second cable clamp cross arm; an upper wire is led to an inverted hanging insulator string on a cable terminal equipment cross arm through a bare wire via the upper wire leading-down cross arm, a middle wire is led to the inverted hanging insulator string through the middle wire leading-down cross arm, and a lower wire is directly led to the inverted hanging insulator string and is connected to a cable terminal and a lightning arrester; the underground cable is led to the cable terminal; and the ladder stand is replaced by a movable ladder stand. According to the method, the old tower does not need to be dismantled, a new tower does not need to be newly built, the occupied area does not need to be increased, the construction cost is greatly reduced, and the problems that urban corridors are narrow, underground pipelines are numerous and cable terminal towers are difficult to newly build are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of high - voltage transmission lines, and particularly to a method for reconstructing a cable terminal lead - down structure based on an existing overhead transmission line. Background Art

[0002] When reconstructing an existing overhead transmission line terminal steel pipe pole into a cable terminal pole, generally, a new tower replacement method or a method of adding a cable platform on the ground is adopted. The first method requires the construction of a new pole tower, with a long reconstruction period and high costs; the second method requires a large additional land area, and it is very difficult to meet the operation requirements in the limited areas such as urban roadside or green belts. Moreover, there are many underground pipelines in the urban area, involving pipeline relocation, with high implementation costs and a long construction period.

[0003] In summary, there is an urgent need to provide a method for reconstructing a cable terminal lead - down structure based on an existing overhead transmission line to solve the technical problems existing in the prior art. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for reconstructing a cable terminal lead - down structure based on an existing overhead transmission line to solve the technical problems existing in the prior art. The specific technical solutions are as follows:

[0005] A method for reconstructing a cable terminal lead - down structure based on an existing overhead transmission line includes the following steps:

[0006] Step S1: Remove the redundant conductor cross - arms on the main pole of the existing steel pipe pole;

[0007] Step S2: Add an upper conductor lead - down cross - arm at the end of the upper conductor cross - arm and add a middle conductor lead - down cross - arm at the end of the middle conductor cross - arm;

[0008] Step S3: Add a cable terminal equipment cross - arm, and the cable terminal equipment cross - arm is connected to the main pole of the existing steel pipe pole through a locking component; a cable terminal base, a lightning arrester base and an inverted insulator string hanging plate are installed on the cable terminal equipment cross - arm;

[0009] Calculate the contact height of the locking component according to the equipment weight on the cable terminal equipment cross - arm and the self - weight of the cable terminal equipment cross - arm;

[0010] Step S4: Install a first cable clamp cross - arm and a second cable clamp cross - arm on the main pole of the existing steel pipe pole along the height direction in sequence through the locking component. The first cable clamp cross - arm and the second cable clamp cross - arm are located below the cable terminal equipment cross - arm; a clamp base is provided at the end of the first cable clamp cross - arm, and a clamp base is provided on the pole body of the second cable clamp cross - arm; a cable clamp is installed on the clamp base;

[0011] Step S5: Lead the upper conductor through the upper conductor downcross arm, and then lead it to the inverted insulator string on the cross arm of the cable terminal equipment through a bare conductor. Lead the middle conductor through the middle conductor downcross arm to the inverted insulator string, and directly lead the lower conductor to the inverted insulator string, and connect it to the cable terminal and the lightning arrester.

[0012] Step S6: Vertically lead the underground cable up to the cable terminal base through the cable clamps on the first cable clamp cross arm and the second cable clamp cross arm.

[0013] Step S7: Remove the ladder that interferes with the locking assembly and replace it with a movable ladder. The movable ladder is connected to the main pole of the existing steel pipe pole through an adjustable connecting piece.

[0014] Furthermore, the projections of the upper conductor downcross arm and the middle conductor downcross arm on the horizontal plane are perpendicular to each other.

[0015] Furthermore, there are multiple cross arms of the cable terminal equipment, and the multiple cross arms of the cable terminal equipment are arranged circumferentially along the main pole of the existing steel pipe pole. The included angle between two adjacent cross arms of the cable terminal equipment is 40° - 50°.

[0016] Furthermore, a platform plate is arranged between two adjacent cross arms of the cable terminal equipment, and the platform plate forms an independent maintenance platform.

[0017] Furthermore, there are multiple first cable clamp cross arms, and the multiple first cable clamp cross arms are arranged circumferentially along the main pole of the existing steel pipe pole. The multiple first cable clamp cross arms correspond to the cross arms of the cable terminal equipment one by one;

[0018] There are multiple second cable clamp cross arms, and the multiple second cable clamp cross arms are arranged circumferentially along the main pole of the existing steel pipe pole. The multiple second cable clamp cross arms correspond to the multiple first cable clamp cross arms one by one.

[0019] Furthermore, at least one of the cross arm of the cable terminal equipment, the first cable clamp cross arm, and the second cable clamp cross arm is in the same direction as the upper conductor cross arm / middle conductor cross arm.

[0020] Furthermore, the locking assembly includes a first hoop assembly. The first hoop assembly includes two polygonal hoops. The inner surface of the polygonal hoop matches the polygonal cross section of the main pole of the existing steel pipe pole. The two polygonal hoops are locked by bolts to form an encircling structure.

[0021] Furthermore, multiple mounting grooves are arranged on the first hoop assembly, and the mounting grooves match the cross arm of the cable terminal equipment, the first cable clamp cross arm, or the second cable clamp cross arm.

[0022] Furthermore, in step S3, the contact height of the locking assembly is H1.

[0023] G1*L1 + G2*L2 = F1*H1 (Formula 1);

[0024] G1 + G2 = F1*H1*a*μ (Formula 2);

[0025] Wherein, L1 and L2 are respectively the lever arms from the equipment on the cross arm of the cable terminal device and the center of gravity of the cross arm to the main pole of the existing steel pipe pole, a is the side length of the contact surface between the polygonal hoop and the main pole of the existing steel pipe pole, and μ is the static friction coefficient.

[0026] Further, in step S7, the adjustable connecting member includes a U-shaped fixture and a long bolt. The U-shaped fixture is tightly connected to the movable ladder through the long bolt; the U-shaped fixture is fixedly connected to the main pole of the existing steel pipe pole.

[0027] Applying the technical solution of the present invention has the following beneficial effects:

[0028] (1) The present invention provides a method for reconstructing a cable terminal lead-down structure based on an existing overhead transmission line. This method is reconstructed based on the existing overhead transmission line, without the need to demolish the old tower and build a new tower, without increasing the floor area, and greatly reducing the construction cost, solving the problems of narrow urban corridors, numerous underground pipelines, and difficulties in building new cable terminal towers.

[0029] (2) In the present invention, a platform plate is provided between the cross arms of two adjacent cable terminal devices. The platform plate forms an independent maintenance platform, which is convenient for later maintenance operations.

[0030] (3) In the present invention, by calculating the contact height of the locking assembly, the contact area between the polygonal hoop and the main pole of the existing steel pipe pole is ensured, thereby ensuring the reliability of the installation of the cable terminal device cross arm and meeting the actual operation requirements.

[0031] In addition to the purposes, features, and advantages described above, the present invention has other purposes, features, and advantages. The following will refer to the drawings for a further detailed description of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0033] Figure 1 is a flowchart of the method of the present invention;

[0034] Figure 2 is a schematic diagram of the cable terminal lead-down structure reconstructed based on the existing overhead transmission line in the present invention;

[0035] Figure 3 is Figure 2Side view;

[0036] Figure 4 is Figure 2 Schematic diagram of the A-A cross-section in;

[0037] Figure 5 is Figure 2 Schematic diagram of the B-B cross-section in;

[0038] Figure 6 is Figure 2 Schematic diagram of the C-C cross-section in;

[0039] Figure 7 is Figure 2 Schematic diagram of the D-D cross-section in;

[0040] Figure 8 is Figure 2 Schematic diagram of the E-E cross-section in;

[0041] Figure 9 Top view schematic diagram of the connection between the cross arm of the cable terminal equipment and the main pole of the existing steel pipe pole;

[0042] Figure 10 is Figure 9 Front view of;

[0043] Figure 11 Top view schematic diagram of the connection between the end of the upper conductor cross arm and the upper conductor leading-down cross arm;

[0044] Figure 12 is Figure 11 Cross-section schematic diagram of;

[0045] Figure 13 Structural schematic diagram of the movable ladder;

[0046] Figure 14 Schematic diagram of the connection between the movable ladder and the main pole of the existing steel pipe pole;

[0047] Figure 15 Structural schematic diagram of the adjustable connecting piece;

[0048] Wherein, 1. Main pole of the existing steel pipe pole, 1.1. Upper conductor cross arm, 1.2. Middle conductor cross arm, 1.3. Lower conductor cross arm, 1.4. Surplus conductor cross arm, 2. Upper conductor leading-down cross arm, 3. Middle conductor leading-down cross arm, 4. Cross arm of the cable terminal equipment, 4.1. Cable terminal base, 4.2. Lightning arrester base, 5. Locking assembly, 5.1. Polygonal hoop one, 5.2. Polygonal hoop two, 6. First cable clamp cross arm, 7. Second cable clamp cross arm, 8. Clamp base, 9. Movable ladder, 9.1. Central circular tube, 9.2. Horizontal tube, 10. Adjustable connecting piece, 10.1. U-shaped clamp, 10.2. Long bolt, 11. Platform plate, 12. Hoop assembly two. Detailed implementation manners

[0049] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in various different ways as defined and covered.

[0050] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", "front", "rear", "lateral", "longitudinal", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0051] In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0052] Embodiment:

[0053] Refer to Figure 1 , this embodiment provides a method for reconstructing the cable terminal lead-down structure based on the existing overhead transmission line, including the following steps:

[0054] Step S1, remove the redundant conductor cross-arm 1.4 on the main pole 1 of the existing steel pipe pole; in this embodiment, refer to Figure 2 , the main pole 1 of the existing steel pipe pole includes a plurality of parallel conductor cross-arms, namely the upper conductor cross-arm 1.1, the middle conductor cross-arm 1.2, the lower conductor cross-arm 1.3 and the redundant conductor cross-arm 1.4 located below the lower conductor cross-arm.

[0055] Step S2, refer to Figure 2 and Figure 3 , add an upper conductor lead-down cross-arm 2 at the end of the upper conductor cross-arm 1.1, and add a middle conductor lead-down cross-arm 3 at the end of the middle conductor cross-arm 1.2; in this embodiment, the upper conductor lead-down cross-arm 2 and the middle conductor lead-down cross-arm 3 are arranged horizontally. Preferably, the projections of the upper conductor lead-down cross-arm 2 and the middle conductor lead-down cross-arm 3 on the horizontal plane are perpendicular to each other; in this embodiment, refer to Figure 7 and Figure 8 , the upper conductor lead-down cross-arm 2 is vertically arranged with the upper conductor cross-arm 1.1 in the horizontal plane, and the middle conductor lead-down cross-arm 3 is arranged along the extension direction of the middle conductor cross-arm 1.2 to prevent the upper conductor and the lower conductor from affecting each other in the lead-down path.

[0056] In this embodiment, the upper conductor cross arm 1.1 and the upper conductor leading-down cross arm 2, as well as the middle conductor cross arm 1.2 and the middle conductor leading-down cross arm 3 are all connected by the second hoop assembly 12. The second hoop assembly 12 is respectively arranged on the upper conductor cross arm 1.1 and the middle conductor cross arm 1.2. A connecting flange is arranged on the second hoop assembly 12, and the connecting flange is connected to the upper conductor leading-down cross arm 2 / the middle conductor leading-down cross arm 3 by bolts. Refer to Figure 11 and Figure 12 .

[0057] Step S3: Add a cross arm 4 for cable terminal equipment. Refer to Figures 2 - 4 and Figure 9 and Figure 10 , the cross arm 4 for cable terminal equipment is connected to the existing steel pipe pole main pole 1 through a locking assembly 5; a cable terminal base 4.1, a lightning arrester base 4.2 and an inverted insulator string hanging plate are installed on the cross arm 4 for cable terminal equipment. Correspondingly, a cable terminal is arranged on the cable terminal base 4.1, a lightning arrester is installed on the lightning arrester base 4.2, and an inverted insulator string is installed on the inverted insulator string hanging plate; in this embodiment, there are 3 cross arms 4 for cable terminal equipment, and the 3 cross arms 4 for cable terminal equipment are arranged circumferentially along the existing steel pipe pole main pole 1, and the included angle between two adjacent cross arms 4 for cable terminal equipment is 40° - 50°, preferably 45°; the cable terminal base 4.1, the lightning arrester base 4.2 and the inverted insulator string hanging plate are symmetrically arranged on two adjacent cross arms 4 for cable terminal equipment respectively.

[0058] As a preferred technical solution, the middle one of the cross arms 4 for cable terminal equipment is arranged in the same direction as the conductor cross arm.

[0059] In this embodiment, refer to Figure 4 , a platform plate 11 is arranged between two adjacent cross arms 4 for cable terminal equipment, and the platform plate 11 forms an independent maintenance platform, which is convenient for later maintenance operations.

[0060] In this embodiment, refer to Figure 9 and Figure 10 , the locking assembly 5 includes a first hoop assembly, and the first hoop assembly includes a polygonal hoop one 5.1 and a polygonal hoop two 5.2. The inner surfaces of the polygonal hoop one 5.1 and the polygonal hoop two 5.2 match the polygonal cross-section of the existing steel pipe pole main pole 1, and the two polygonal hoops are locked by bolts to form a surrounding structure.

[0061] Under the action of the weight G1 of the equipment on the cross arm 4 of the cable terminal equipment and the self-weight G2 of the cross arm 4 of the cable terminal equipment, a squeezing force F1 will be generated on the upper end of the polygonal hoop 1 5.1 and the lower end of the polygonal hoop 2 5.2 respectively. The polygonal hoop 1 5.1 and the polygonal hoop 2 5.2 are in full contact with the main pole 1 of the existing steel pipe pole, and the contact area is H1*a, where H1 is the contact height of the locking component, and a is the side length of the contact surface between the polygonal hoop and the main pole of the existing steel pipe pole. The value of H1 is calculated by the following formula:

[0062] G1*L1 + G2*L2 = F1*H1 (Formula 1);

[0063] G1 + G2 = F1*H1*a*μ (Formula 2);

[0064] Wherein, L1 and L2 are respectively the force arms from the center of gravity of the equipment and the cross arm on the cross arm of the cable terminal equipment to the main pole of the existing steel pipe pole, a is the side length of the contact surface between the polygonal hoop and the main pole of the existing steel pipe pole, and μ is the static friction coefficient.

[0065] The contact height of the locking component 5 is calculated by the above method to ensure the contact area between the polygonal hoop and the main pole of the existing steel pipe pole, and further ensure the reliability of the installation of the cross arm 4 of the cable terminal equipment, meeting the actual operation requirements.

[0066] Step S4. Refer to Figure 2 and Figure 3 , the first cable clamp cross arm 6 and the second cable clamp cross arm 7 are sequentially installed on the main pole 1 of the existing steel pipe pole along the height direction through the locking component 5. The first cable clamp cross arm 6 and the second cable clamp cross arm 7 are located below the cross arm 4 of the cable terminal equipment; in this embodiment, refer to Figure 5 and Figure 6 , there are 3 first cable clamp cross arms 6, and the 3 first cable clamp cross arms 6 are arranged circumferentially along the main pole 1 of the existing steel pipe pole. The 3 first cable clamp cross arms 6 are vertically corresponding to the cross arm 4 of the cable terminal equipment one by one; the middle first cable clamp cross arm 6 is in the same direction as the conductor cross arm;

[0067] There are 3 second cable clamp cross arms 7, and the 3 second cable clamp cross arms 7 are arranged circumferentially along the main pole 1 of the existing steel pipe pole. The multiple second cable clamp cross arms 7 are vertically corresponding to the multiple first cable clamp cross arms 6 one by one; the middle second cable clamp cross arm 7 is in the same direction as the conductor cross arm;

[0068] In this embodiment, refer to Figure 5 and Figure 6The ends of the plurality of first cable clamp cross arms 6 are all provided with clamp bases 8, and the rods of the plurality of second cable clamp cross arms 7 are symmetrically provided with clamp bases 8; the clamp bases 8 are provided with cable clamps for fixing the cables.

[0069] In this embodiment, see Figure 9 and Figure 10 The polygonal clamp 2 5.2 is provided with a plurality of mounting grooves, and the mounting grooves match the cross arm 4 of the cable terminal equipment, the first cable clamp cross arm 6 or the second cable clamp cross arm 7.

[0070] Step S5, lead the upper conductor through the upper conductor lower cross arm 2 and the bare conductor to the inverted insulator string on the cable terminal equipment cross arm 4, lead the middle conductor through the middle conductor lower cross arm 3 to the inverted insulator string, and directly lead the lower conductor to the inverted insulator string, and connect to the cable terminal and the lightning arrester.

[0071] Step S6: vertically lead the underground cable to the cable terminal base 4.1 through the cable clamps on the first cable clamp cross arm 6 and the second cable clamp cross arm 7.

[0072] Step S7, remove the ladder that interferes with the locking assembly 5 and replace it with a movable ladder 9, wherein the movable ladder 9 is connected to the existing steel pipe rod main rod 1 through a plurality of adjustable connecting parts 10.

[0073] In this embodiment, see Figures 13 - 15 , the movable ladder 9 includes a central circular tube 9.1 and transverse tubes 9.2 staggered on opposite sides of the central circular tube 9.1; the adjustable connector 10 includes a U-shaped clamp 10.1 and a long bolt 10.2, the U-shaped clamp 10.1 cooperates with the central circular tube 9.1 and is locked by the long bolt 10.2; the U-shaped clamp 10.1 is fixedly connected to the connecting plate of the existing steel pipe rod main rod 1 by bolts; by setting the adjustable connector 10, the installation position of the movable ladder 9 can be adjusted to meet actual operation requirements. In addition, the U-shaped clamp 10.1 is first locked and connected with the central circular tube 9.1, and then connected with the existing steel pipe rod main rod 1, which can solve the problem of installation difficulties caused by inaccurate measurement of rod size and insufficient processing and welding accuracy, reduce the requirements for processing accuracy, and improve installation efficiency.

[0074] The present invention is based on the transformation of existing overhead transmission line steel pipe poles into cable terminal downlead structures. There is no need to dismantle old towers and build new towers, and there is no need to increase the floor area, which greatly reduces construction costs and solves the problems of narrow corridors in urban areas, numerous underground pipelines, and difficulty in building new cable terminal towers.

[0075] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for reconstructing a cable terminal downlead structure based on an existing overhead transmission line, characterized in that: The following steps are involved: Step S1, removing the redundant conductor crossarms on the main pole of the built steel pipe pole; Step S2, adding an upper conductor lower cross arm at the end of the upper conductor cross arm, and adding a middle conductor lower cross arm at the end of the middle conductor cross arm; Step S3, adding a cross arm of a cable terminal equipment, wherein the cross arm of the cable terminal equipment is connected to the main pole of the existing steel pipe pole through a locking assembly; a cable terminal base, a lightning arrester base and an inverted insulator string hanging plate are installed on the cross arm of the cable terminal equipment; Calculate the contact height of the locking assembly according to the weight of the equipment on the cross arm of the cable terminal equipment and the deadweight of the cross arm of the cable terminal equipment; Step S4, installing the first cable clamp cross arm and the second cable clamp cross arm on the main pole of the built steel pipe pole in the height direction in sequence through the locking assembly, the first cable clamp cross arm and the second cable clamp cross arm are located below the cross arm of the cable terminal device; the end of the first cable clamp cross arm is provided with a clamp base, and the rod body of the second cable clamp cross arm is provided with a clamp base; the clamp base is installed with a cable clamp; Step S5, lead the upper conductor through the upper conductor lower cross arm and the bare conductor to the inverted insulator string on the cross arm of the cable terminal equipment, lead the middle conductor through the middle conductor lower cross arm to the inverted insulator string, and directly lead the lower conductor to the inverted insulator string, and connect to the cable terminal and the lightning arrester; Step S6, vertically lead the underground cable to the cable terminal base through the cable clamps on the first cable clamp cross arm and the second cable clamp cross arm; Step S7, remove the ladder that interferes with the locking assembly and replace it with a movable ladder, wherein the movable ladder is connected to the existing steel pipe rod main rod through an adjustable connecting piece.

2. The method for reconstructing a cable terminal downlead structure based on an existing overhead transmission line according to claim 1, characterized in that: The projections of the upper conductor down-leading cross arm and the middle conductor down-leading cross arm on the horizontal plane are perpendicular to each other.

3. The method for reconstructing a cable terminal downlead structure based on an existing overhead transmission line according to claim 1, characterized in that: There are multiple cross arms for the cable terminal equipment, and the multiple cross arms for the cable terminal equipment are arranged along the circumference of the main pole of the built steel pipe pole, and the angle between two adjacent cross arms of the cable terminal equipment is 40°-50°.

4. The method for reconstructing a cable terminal downlead structure based on an existing overhead transmission line according to claim 3, characterized in that: A platform plate is arranged between the cross arms of two adjacent cable terminal devices, and the platform plate forms an independent maintenance platform.

5. The method for reconstructing a cable terminal downlead structure based on an existing overhead transmission line according to claim 3, characterized in that: There are multiple first cable clamp cross arms, and the multiple first cable clamp cross arms are arranged along the circumference of the main pole of the built steel pipe pole, and the multiple first cable clamp cross arms correspond to the cross arms of the cable terminal equipment one by one; There are multiple second cable clamp cross arms, and the multiple second cable clamp cross arms are arranged along the circumference of the main pole of the built steel pipe pole. The multiple second cable clamp cross arms correspond one-to-one to the multiple first cable clamp cross arms.

6. The method for reconstructing a cable terminal downlead structure based on an existing overhead transmission line according to claim 5, characterized in that: At least one of the cable terminal equipment cross arm, the first cable clamp cross arm and the second cable clamp cross arm is in the same direction as the upper conductor cross arm / middle conductor cross arm.

7. The method for reconstructing a cable terminal downlead structure based on an existing overhead transmission line according to claim 1, characterized in that: The locking assembly includes a clamp assembly 1, and the clamp assembly 1 includes two polygonal clamps. The inner surface of the polygonal clamp matches the polygonal cross-section of the main rod of the built steel pipe rod. The two polygonal clamps are locked by bolts to form an embracing structure.

8. The method for reconstructing a cable terminal downlead structure based on an existing overhead power transmission line according to claim 7, characterized in that: The clamp assembly is provided with a plurality of mounting grooves, and the mounting grooves match the cross arm of the cable terminal equipment, the first cable clamp cross arm or the second cable clamp cross arm.

9. The method for reconstructing a cable terminal downlead structure based on an existing overhead power transmission line according to claim 1, characterized in that: In step S3, the contact height of the locking assembly is H1, G1*L1+G2*L2=F1*H1 (Formula 1); G1+G2=F1*H1*a*μ (Formula 2); Among them, L1 and L2 are the equipment on the crossarm of the cable terminal equipment and the force arm from the center of gravity of the crossarm to the main pole of the built steel pipe pole, a is the side length of the contact surface between the polygonal clamp and the main pole of the built steel pipe pole, and μ is the static friction coefficient.

10. The method for reconstructing a cable terminal downlead structure based on an existing overhead transmission line according to any one of claims 1 to 9, characterized in that: In step S7, the adjustable connecting member includes a U-shaped clamp and a long bolt, and the U-shaped clamp is locked and connected to the movable ladder through the long bolt; the U-shaped clamp is fixedly connected to the main rod of the built steel pipe rod.

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