A multi-bundled conductor icing characteristic test device and a torsional stiffness design method thereof

Abstract

The application discloses a kind of multi-split conductor icing characteristic test device and its torsional rigidity design method, the device includes two support frames and is arranged between two support frames multiple multi-split conductor sections;Through the transmission direction of thin rope change horizontal spring tension, the torsional rigidity of the multi-split conductor icing characteristic test device remains constant when large angle torsion, can be used for multi-split conductor large angle torsion icing characteristic test;The torsional rigidity design method of the application, based on modal superposition method and dynamic similarity criterion, obtains each physical parameter of the multi-split conductor icing characteristic test device, by using different horizontal spring stiffness and torque loading disc radius combination, realize the accurate design of the torsional rigidity of the multi-split conductor icing characteristic test device, accurately simulate the icing characteristic of any real multi-split conductor at any position.

Description

Technical Field

[0001] This invention belongs to the field of power technology and relates to a test device for the icing characteristics of multi-split conductors, and in particular to a test device for the icing characteristics of multi-split conductors that considers the dynamic torsion of icing conductors and its torsional stiffness design method. Background Technology

[0002] Icing significantly increases the tension on transmission lines, potentially causing accidents such as line breaks, hardware damage, and even tower collapse. Furthermore, the shape of the icing on transmission lines severely alters aerodynamic parameters such as the three-part force coefficient and aerodynamic derivative of conductor segments, thus affecting conductor galloping and wind deflection characteristics. Therefore, researching the icing characteristics of transmission lines to obtain information on the shape, quality, and density of icing on multi-segmented conductors is of practical significance for early warning and prevention of transmission line disasters.

[0003] Currently, research on the icing characteristics of transmission lines mainly includes field measurements and artificial simulation experiments. Real-world transmission lines need to traverse complex terrain and operate at high altitudes, making on-site ice observation difficult, and the accuracy of the acquired data is hard to guarantee. Breakthroughs in electrical testing technology have enabled the acquisition of transmission line icing characteristics through indoor tests; however, existing testing equipment is mostly rigid segment models. In reality, transmission lines have large spanwise dimensions and high flexibility. After icing, especially after uneven icing of multi-segment conductors, twisting is inevitable, affecting the icing process. Using rigid segment models will lead to significant differences between the experimental results of multi-segment conductor icing characteristics and the actual icing characteristics of transmission lines. Summary of the Invention

[0004] To address the shortcomings of existing multi-split conductor icing characteristic testing devices that fail to consider the torsion caused by uneven icing of the split conductors, resulting in significant errors in test results, this invention proposes a multi-split conductor icing characteristic testing device capable of large-angle torsion and with constant torsional stiffness. Based on the modal superposition method and dynamic similarity criterion, a torsional stiffness design method for this device is given, which can simulate the icing characteristics of any real multi-split conductor at any location.

[0005] Therefore, the above-mentioned objective of the present invention is achieved by the following technical solution: a multi-split conductor icing characteristic test device, which includes two support frames and multiple multi-split conductor segments disposed between the two support frames;

[0006] The top of the support frame is connected to a rolling bearing with a support, and a connecting shaft is fitted onto the rolling bearing; the inner end of the connecting shaft is connected to a connecting disc located inside the support frame, and the outer end of the connecting shaft is connected to a torque loading disc with an angle scale, located outside the support frame; the outer side of the connecting disc is connected to an end plate located inside the support frame, so that two symmetrically arranged end plates are formed on the connecting discs of the two support frames, and the end plates are provided with wire holes for multi-split wire segments to pass through;

[0007] One end of the multi-split conductor segment is connected to the end plate of a connecting disk, and the other end is connected to the end plate of another connecting disk.

[0008] Each side of the torque loading disk has a spring support groove and a positioning plate. A horizontal spring is placed in the spring support groove. One end of the horizontal spring is connected to the corresponding positioning plate, and the other end is connected to a first thin rope. The other end of the first thin rope passes under the torque loading disk and is wound around a winding groove on the end face of the torque loading disk. One end of the other horizontal spring is connected to the corresponding positioning plate, and the other end is connected to a second thin rope. The other end of the second thin rope passes under the torque loading disk and is wound around another winding groove on the end face of the torque loading disk.

[0009] When the horizontal spring is relaxed, the spring support groove overcomes the weight of the horizontal spring, avoiding the generation of additional torque, thus fully ensuring the stability and accuracy of the stiffness provided by the horizontal spring. The torque loading disk has angle markings on its surface, allowing for the reading of the torsional angle of the multi-split conductor icing characteristic test device. Both the first and second thin ropes can change the transmission direction of the horizontal spring tension, ensuring the horizontal spring remains horizontal when the torque loading disk undergoes large-angle torsion. This prevents the torsional stiffness of the multi-split conductor icing characteristic test device from changing during the test, making it suitable for testing the icing characteristics of multi-split conductors under large-angle torsion. The supported rolling bearing can withstand the weight load of the multi-split conductor segments, limiting the horizontal and vertical displacement of the multi-split conductor icing characteristic test device and accurately transmitting the icing torque of the multi-split conductor segments to the torque loading disk.

[0010] Furthermore, the connecting disc has an outer ring of threaded holes, and the end plate has fewer threaded holes than the outer ring of threaded holes. The connecting disc and the end plate are connected by fasteners for easy assembly and disassembly. The end plate is connected to the connecting disc through outer ring screw holes at different positions to adjust the initial wind angle of attack of the multi-split conductor icing characteristic test device.

[0011] Furthermore, the end plate is in the shape of a straight line, a cross, a *, or a star, corresponding to the installation of two-split, four-split, six-split, and eight-split wires, respectively.

[0012] Furthermore, the support frame includes a crossbeam and a column; one end of the crossbeam is fixed to a column by bolts, and the other end is fixed to another column by bolts; the top surface of the middle part of the crossbeam is connected to the rolling bearing with a support.

[0013] Furthermore, the column is provided with positioning plates and spring support grooves. The positioning plates are perforated positioning plates, and the horizontal springs are connected to the corresponding holes on the positioning plates by hooks. The column feet located at the bottom of the column are vertically fixed to the ground by bolts.

[0014] Furthermore, the angle scale engraved on the torque loading disk is 360 degrees.

[0015] Furthermore, by controlling the length of the thin rope, the two horizontal springs are kept at their original lengths before the torque loading disk is twisted. When the torque loading disk is twisted to one side, one horizontal spring is tensioned to provide stiffness, while the other horizontal spring is relaxed and does not provide stiffness, thus avoiding the springs being in a compressed state and ensuring the normal conduct of the multi-split conductor icing test.

[0016] Furthermore, by using combinations of different horizontal spring stiffness and torque-loaded disk radii, the torsional stiffness of any real multi-split conductor at any position can be simulated.

[0017] Another objective of this invention is to address the shortcomings of existing multi-split conductor icing characteristic testing devices, which fail to consider the torsion caused by uneven icing of the split conductors, resulting in significant errors in test results. This invention provides a torsional stiffness design method for a multi-split conductor icing characteristic testing device based on the modal superposition method, comprising the following steps:

[0018] S1. Establish the torsional motion equation of the prototype multi-split conductor under uneven ice load;

[0019] S2. Based on the principle of modal decomposition, establish the torsional response expression of the prototype multi-split conductor, and based on the assumption of orthogonal damping matrix, decouple the torsional motion equation of the multi-degree-of-freedom system by utilizing the orthogonality of modes to obtain the torsional motion equation of a single degree-of-freedom system.

[0020] S3. By adjusting the generalized torque to simulate different non-uniform icing forms, calculate the generalized parameters of the nth mode of the prototype multi-split conductor.

[0021] S4. Based on dynamic similarity and dimensional principles, the torsion angle scaling ratio γ between the multi-split conductor icing characteristic test device and the prototype multi-split conductor is determined in advance. θ and dimensional scaling ratio γ LThen, the similarity ratio coefficients of the remaining parameters are determined in sequence, including the scale ratio of angular acceleration, gravity, torsional circular frequency, torque, moment of inertia and torsional stiffness between the multi-split conductor icing characteristic test device and the prototype multi-split conductor; based on the aforementioned scale ratio of torsional circular frequency and moment of inertia and the torsional circular frequency and moment of inertia of the prototype conductor, the torsional circular frequency and moment of inertia of the multi-split conductor icing characteristic test device are determined.

[0022] S5. Based on the torsional circular frequency and moment of inertia of the multi-split conductor icing characteristic test device determined in step S4, a suitable horizontal spring stiffness K is selected. x The radius R of the torque loading disk is adjusted to match the torsional circular frequency of the multi-split conductor icing characteristic test device with that of the prototype multi-split conductor, thereby simulating the torsion characteristics of the prototype multi-split conductor caused by uneven icing.

[0023] The beneficial effects of this invention are as follows: This invention changes the transmission direction of the horizontal spring tension by using a thin rope, so that the torsional stiffness of the multi-split conductor icing characteristic test device remains constant during large-angle torsion, and can be used for large-angle torsional icing characteristic tests of multi-split conductors; The torsional stiffness design method of this invention for the multi-split conductor icing characteristic test device is based on the modal superposition method and dynamic similarity criterion to obtain various physical parameters of the multi-split conductor icing characteristic test device. By using different combinations of horizontal spring stiffness and torque loading disk radius, the torsional stiffness of the multi-split conductor icing characteristic test device can be accurately designed, and the icing characteristics of any real multi-split transmission conductor at any position can be accurately simulated. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the multi-split conductor icing characteristic test device of the present invention;

[0025] Figure 2 for Figure 1 Left side view;

[0026] Figure 3 This is a schematic diagram of the geometric parameters of a 500kV two-stage four-split true-type transmission line in a specific embodiment of the present invention;

[0027] Figure 4 This is a diagram of the first-order torsional vibration mode of a true four-split transmission conductor in a specific embodiment of the present invention;

[0028] Figure 5 This is a schematic diagram of the torsion of a multi-segment conductor model in a specific embodiment of the present invention;

[0029] In the diagram: 1-Torque loading disk; 2-Rolling bearing with support; 3-Connecting shaft; 4-Connecting disk; 5-End plate; 6-Multi-split conductor segment; 7-Crossbeam; 8-Column; 9-Spring support groove; 10-Horizontal spring; 11-First thin rope; 12-Positioning plate; 13-Second thin rope. Detailed Implementation

[0030] The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

[0031] This embodiment provides a test apparatus for the icing characteristics of multi-split conductors, referring to... Figure 1-2 It consists of two support frames and multiple multi-split conductor segments 6 positioned between the two support frames. Each support frame consists of a crossbeam 7 and two columns 8; one end of the crossbeam 7 is fixed to one column by bolts, and the other end is fixed to the other column by bolts; the top surface of the middle part of the crossbeam is connected to a rolling bearing 2 with a support. Positioning plates 12 and spring support grooves 9 are welded onto the columns 8. The positioning plates 12 are perforated positioning plates, and the column feet at the bottom of the columns are vertically fixed to the ground by bolts.

[0032] The rolling bearing 2 with support is fitted onto the connecting shaft 3. The inner end of the connecting shaft 3 is connected to a connecting disc 4 located inside the support frame by four bolts, and the outer end of the connecting shaft 3 is connected to a torque loading disc 1 with 360-degree angle markings. The torque loading disc 1 is located outside the support frame and is made of high-strength acrylic material. Two screw holes are opened on the disc surface, and it is fixed to the connecting shaft 3 by bolts. The outer side of the connecting disc 4 is connected to an end plate 5 located inside the support frame, thus forming two symmetrically arranged end plates on the connecting discs of the two support frames. The end plates are cross-shaped and have four screw holes and four wire holes for multi-split conductor segments 6 to pass through. The end plates 5 are connected to the connecting disc 4 through the four screw holes and to the multi-split conductor segments 6 through the four wire holes. One end of each multi-split conductor segment is connected to the end plate of one connecting disc, and the other end is connected to the end plate of the other connecting disc.

[0033] Each side of the torque loading disk 1 has a spring support groove 9 and a positioning piece 12. A horizontal spring 10 is placed in the spring support groove 9. One end of the horizontal spring is connected to the corresponding positioning piece, and the other end is connected to a first thin rope 11. The other end of the first thin rope 11 passes under the torque loading disk and is wound around a winding groove on the end face of the torque loading disk. One end of the other horizontal spring is connected to a hole on the corresponding positioning piece by a hook, and the other end is connected to a second thin rope 13. The other end of the second thin rope 13 passes under the torque loading disk and is wound around another winding groove on the end face of the torque loading disk.

[0034] By controlling the length of the thin rope, the two horizontal springs are positioned exactly at their original lengths before the torque-loading disk twists. When the torque-loading disk twists to one side, one horizontal spring is tensioned to provide stiffness, while the other horizontal spring is relaxed and provides no stiffness. This invention uses different combinations of horizontal spring stiffness and torque-loading disk radius to simulate the torsional stiffness of any real multi-split conductor at any position.

[0035] The connecting disc is made of high-strength acrylic material. The disc surface has four inner ring screw holes and twenty-four outer ring screw holes. Four bolts are used to connect it to the connecting shaft 3 through the inner ring screw holes, and four bolts are used to connect it to the end plate 5 through the outer ring screw holes. The end plate has fewer threaded holes than the outer ring screw holes. The end plate is connected to the connecting disc through the outer ring screw holes at different positions, used to adjust the initial wind attack angle of the multi-split conductor icing characteristic test device.

[0036] To accommodate different test conditions and site requirements, the present invention allows for flexible adjustment of the size of the multi-split conductor icing characteristic test device and the material selection of the horizontal spring.

[0037] In this embodiment, the multi-split conductor segment 6 is four-split. Of course, in other embodiments, it can also be two-split, six-split, eight-split, etc., and all of them fall within the protection scope of this invention.

[0038] This embodiment also provides a method for designing the torsional stiffness of the above-mentioned multi-split conductor icing characteristic test device, the steps of which are as follows:

[0039] S1. Establish the torsional motion equation of the prototype multi-split conductor under uneven icing load.

[0040] In step S1, the equation of torsional motion is:

[0041] [J]{θ”}+[C θ ]{θ'}+[K θ ]{θ}={T} (1)

[0042] In the formula, [J] and [K] θ ] and [C θ These are the moment of inertia, torsional stiffness, and torsional damping matrix of the prototype multi-split conductor, respectively.

[0043] {T} is the torque generated by the non-uniform icing of the prototype multi-split conductor, representing the non-uniform icing at any position of the prototype multi-split conductor; {θ} is the torsional angular response vector of the prototype multi-split conductor; {θ'} is the angular velocity vector of the prototype multi-split conductor.

[0044] {θ”} is the angular acceleration vector of the prototype multi-split conductor.

[0045] S2. Based on the principle of modal decomposition, establish the torsional response expression of the prototype multi-split conductor. Based on the assumption of orthogonal damping matrix, decouple the torsional motion equation of the multi-degree-of-freedom system by utilizing the orthogonality of modes to obtain the torsional motion equation of a single degree-of-freedom system.

[0046] In step S2, the torsional response expression of the prototype multi-split conductor is:

[0047]

[0048] The equation of motion for the single-degree-of-freedom torsional motion is:

[0049]

[0050] In the formula, θ(t) is the torsion angle matrix of the prototype multi-split conductor at time t; φ n The nth torsional vibration mode of the prototype multi-split conductor; q n (t) represents the generalized coordinates corresponding to the nth torsional mode of the prototype multi-split conductor; These represent the torsional damping ratio and torsional vibration circular frequency of the nth mode of the prototype multi-split conductor, respectively; q n '(t) represents the first derivative of the generalized coordinates of the nth mode of the prototype multi-split conductor with respect to time; q n "(t) is the second derivative of the generalized coordinate of the nth mode of the prototype multi-split conductor with respect to time, and T(t) is the torque vector of the transmission conductor due to uneven icing.

[0051] S3. By adjusting the generalized torque to simulate different non-uniform icing forms, calculate the generalized parameters of the nth mode of the prototype multi-split conductor.

[0052] In step S3, the generalized parameters for calculating the nth mode shape of the prototype multi-split conductor are calculated using the following formula:

[0053] J n ={φ n} T [J]{φ n} (3a)

[0054] K θn ={φ n} T [K θ ]{φ n} (3b)

[0055]

[0056] In the formula, J n The nth order generalized moment of inertia of the prototype multi-split wire. The nth order generalized torsional stiffness of the prototype multi-split conductor, C nIt is the nth-order generalized damping matrix of the prototype multi-split conductor.

[0057] S4. Based on dynamic similarity and dimensional principles, the torsion angle scaling ratio γ between the multi-split conductor icing characteristic test device and the prototype multi-split conductor is determined in advance. θ and dimensional scaling ratio γ L Then, determine the similarity ratio coefficients of the remaining parameters in turn.

[0058] In step S4, the formula used to determine the similarity ratio coefficients of the remaining parameters is as follows:

[0059]

[0060]

[0061] In the formula, γ θ” γ g , γ T γ J and The scale ratios are angular acceleration, gravity, torsional circular frequency, torque, moment of inertia, and torsional stiffness of the test device and the prototype multi-split conductor icing characteristics test device.

[0062] The torsional circular frequency and rotational inertia of the multi-split conductor icing characteristic test device are determined based on the torsional circular frequency scaling ratio, rotational inertia scaling ratio, and the torsional circular frequency and rotational inertia of the prototype conductor.

[0063] S5. Based on the torsional circular frequency and moment of inertia of the multi-split conductor icing characteristic test device determined in step S4, a suitable horizontal spring stiffness K is selected. x The radius R of the torque loading disk is adjusted to match the torsional circular frequency of the multi-split conductor icing characteristic test device with that of the prototype multi-split conductor, thereby simulating the torsion characteristics of the prototype multi-split conductor caused by uneven icing.

[0064] In step S5, the stiffness K of the horizontal spring x The radius R of the torque-loaded disk is calculated using the following formula:

[0065]

[0066] In the formula, J m The moment of inertia of the test apparatus for the icing characteristics of multi-split conductors. The torsional vibration angular frequency of the prototype multi-split conductor.

[0067] The following application examples illustrate the specific application of the above-mentioned multi-split conductor icing characteristic test device in the torsional stiffness design method based on modal superposition:

[0068] (1) Obtaining the torsional circular frequency of the prototype multi-split conductor

[0069] A finite element model of a 500kV two-span, four-split, large-elevation-difference transmission line was established, see [link / reference]. Figure 3 The physical parameters of the multi-split conductors are shown in Table 1.

[0070] Table 1

[0071] model outer diameter / mm Line quality / Kg / m Elastic modulus / MPa Poisson's ratio LGJ-630 / 55 34.32 2.209 65 0.3

[0072] Modal analysis of the prototype multi-split conductor was performed using finite element method software, such as... Figure 4 As shown, its torsional circular frequency is 0.14885Hz.

[0073] (2) Determination of physical parameters of the test device for icing characteristics of multi-split conductors

[0074] The diameter of the sub-conductors and the spacing between them significantly affect the icing characteristics of multi-split conductors. Therefore, it is necessary to ensure that the experimental setup for the icing characteristics of multi-split conductors is scaled down to the prototype multi-split conductor by a ratio γ. L =1, and after selecting suitable materials, the moment of inertia of the multi-split conductor icing characteristic test device can be calculated as J. m =2.65 kgm 2 .

[0075] Uneven icing occurs due to the shielding effect between multi-split conductors, causing overall twisting of the multi-split conductor and thus affecting the shielding effect between sub-conductors. Therefore, to accurately simulate the icing characteristics of multi-split conductors, it is necessary to ensure that the torsion angle scale γ between the multi-split conductor icing characteristic test apparatus and the prototype multi-split conductor is maintained. θ =1. According to equation (4a), the required similarity ratio of the torsional circular frequency of the multi-split conductor icing characteristic test device to the prototype multi-split conductor is 1.

[0076] like Figure 5 As shown, the torsional stiffness of the multi-split conductor icing characteristic test device is provided by a horizontal spring and a thin rope. Assume that when the test device rotates clockwise by an angle θ, the left horizontal spring is in a relaxed state and provides no tension, while the right horizontal spring is in a stretched state, and the deformation of the right horizontal spring is θR. If the stiffness of the horizontal spring is K... x Under the action of two horizontal springs, the restoring torsional moment and torsional stiffness of the multi-split conductor icing characteristic test device are as follows:

[0077] M θ =2K x ·θR·R=2K x θR2 (7a)

[0078]

[0079] In the formula, M θ To restore the torsional moment and K of the test device for the icing characteristics of multi-split conductors θ R represents the torsional stiffness of the test device for the icing characteristics of multi-split conductors, and R represents the radius of the torque loading disk.

[0080] The radius of the torque loading disk is determined to be R = 0.15m, and the moment of inertia of the multi-split conductor icing characteristic test device is J. m = 2.65 kg·m 2 The test apparatus for testing the icing characteristics of multi-split conductors and the torsional circular frequency ω θ Substituting 0.14485Hz into equation (7b) yields the stiffness K of the horizontal spring. x =52N / m.

[0081] The above specific embodiments are used to explain and illustrate the present invention, and are only preferred embodiments of the present invention, not intended to limit the present invention. Any modifications and alterations made to the present invention within the spirit and scope of the claims fall within the protection scope of the present invention.

[0082] In this embodiment, the test site is an artificial climate chamber. Of course, in other embodiments, the device can also be installed in outdoor natural conditions and in environments such as ice caves, and all of these fall within the protection scope of this invention.

Claims

1. A multi-bundled conductor icing characteristic test device characterized by comprising: The support frame comprises two support frames and a plurality of multi-split conductor segments (6) arranged between the two support frames. The top of the support frame is connected with a rolling bearing (2) with a support, the rolling bearing (2) is sleeved with a connecting shaft (3); the inner end of the connecting shaft (3) is connected with a connecting disc (4) located on the inner side of the support frame, and the outer end of the connecting shaft (3) is connected with a torque loading disc (1) with an angle scale, which is located on the outer side of the support frame; the outer side of the connecting disc (4) is connected with an end plate (5) located on the inner side of the support frame, so that two end plates arranged symmetrically are formed on the connecting discs of the two support frames, and the end plates are provided with conductor holes for the multi-split conductor segments to pass through. One end of the multi-split conductor segment (6) is connected with the end plate of one connecting disc, and the other end is connected with the end plate of the other connecting disc. The torque loading disc (1) is provided with a spring supporting groove (9) and a positioning sheet (12) on each side, and a horizontal spring (10) is arranged in the spring supporting groove (9); one end of the horizontal spring is connected with the corresponding positioning sheet, and the other end is connected with a first thin rope (11), and the other end of the first thin rope passes below the torque loading disc and is wound on a winding groove on the end face of the torque loading disc; one end of the other horizontal spring is connected with the corresponding positioning sheet, and the other end is connected with a second thin rope (13), and the other end of the second thin rope passes below the torque loading disc and is wound on another winding groove on the end face of the torque loading disc.

2. The device of claim 1, wherein the device is characterized by: A plurality of outer thread holes are arranged on the connecting disc (4), a plurality of thread holes are arranged on the end plate, the number of the thread holes is less than that of the outer thread holes, and the connecting disc and the end plate are connected through fasteners; the end plate is connected with the connecting disc through the outer thread holes at different positions, and the initial wind attack angle of the multi-split conductor icing characteristic test device is adjusted.

3. The device of claim 1, wherein the device is characterized by: The end plate (5) is in the shape of a straight line, a cross, a star or a rice character.

4. The device of claim 1, wherein The support frame comprises a crossbeam (7) and a column (8); one end of the crossbeam is fixed on one column through a bolt, and the other end is fixed on another column through a bolt; the top surface of the middle part of the crossbeam is connected with the rolling bearing with a support.

5. The device of claim 4, wherein the device is characterized by: The column (8) is provided with the positioning sheet and the spring supporting groove, the positioning sheet is a hole positioning sheet, and the horizontal spring is connected with the hole on the corresponding positioning sheet through a hook; the column foot located at the bottom of the column is vertically fixed on the ground through a bolt.

6. The device of claim 1, wherein the device is configured to: The angle scale engraved on the torque loading disc is 360 degrees.

7. The device of claim 1, wherein the device is a multi-bundle ice accretion characteristic test device. By controlling the length of the thin rope, the two horizontal springs are just in the original length before the torque loading disc is twisted, when the torque loading disc is twisted to one side, one horizontal spring is tensioned to provide stiffness, and the other horizontal spring is relaxed to not provide stiffness.

8. The device of claim 1, wherein the device is configured to simulate the ice accretion on the multi-bundled conductor by spraying water on the multi-bundled conductor. Different combinations of horizontal spring stiffness and torque loading disc radius are adopted to realize the simulation of the torsional stiffness of any real multi-split conductor at any position.

9. The method of claim 1-8, wherein the torsional stiffness of the multi-split conductor icing characteristics test device is designed such that the torsional stiffness of the multi-split conductor icing characteristics test device is less than the torsional stiffness of the multi-split conductor. The method comprises the following steps: S1. establishing a torsional motion equation of a prototype multi-split conductor under the action of uneven icing load; S2. Establishing the expression of the prototype multi-bundled conductor torsional response according to the principle of mode decomposition method, and decoupling the torsional motion equation of the multi-degree-of-freedom system based on the assumption of orthogonal damping matrix and the orthogonality of modes to obtain the single-degree-of-freedom torsional motion equation; S3. Simulating different uneven ice accretion forms by adjusting the generalized torque, and calculating the generalized parameters of the nth mode of the prototype multi-bundled conductor; S4. Determine the torsion angle scale ratio γ of the multi-bundled conductor icing characteristic test device and the prototype multi-bundled conductor based on the dynamic similarity relationship and the dimensional principle θ and the size scale ratio γ L , and then determine the rest of the parameter similarity ratio coefficients in sequence, including the angular acceleration scale ratio, the gravity scale ratio, the torsional circular frequency scale ratio, the torque scale ratio, the moment of inertia scale ratio and the torsional stiffness scale ratio of the multi-bundled conductor icing characteristic test device and the prototype multi-bundled conductor; determine the torsional circular frequency and the moment of inertia of the multi-bundled conductor icing characteristic test device according to the torsional circular frequency scale ratio, the moment of inertia scale ratio and the torsional circular frequency and the moment of inertia of the prototype conductor; S5. Based on the torsional circular frequency and the moment of inertia of the multi-bundled conductor icing characteristic test device determined in step S4, the torsional circular frequency of the multi-bundled conductor icing characteristic test device is adjusted to be consistent with the torsional circular frequency of the prototype multi-bundled conductor by selecting a suitable horizontal spring stiffness K x and the torque loading disc radius R, and the torsional circular frequency of the multi-bundled conductor icing characteristic test device is adjusted to be consistent with the torsional circular frequency of the prototype multi-bundled conductor, thereby simulating the characteristics of the torsion of the prototype multi-bundled conductor due to uneven icing.

10. The torsional stiffness design method of claim 9, wherein In step S1, the torsional motion equation is: [J]{θ''} + [C θ ]{θ'} + [K θ ]{θ} = {T} (1) where [J], [K θ ] and [C θ ] are the rotational inertia, the torsional stiffness and the torsional damping matrices of the prototype multi-bundled conductor, respectively; {T} is the torque of the prototype multi-bundled conductor due to the non-uniform icing, which represents the non-uniform icing at any position of the prototype multi-bundled conductor; {θ} is the torsional angular response vector of the prototype multi-bundled conductor; {θ'} is the angular velocity vector of the prototype multi-bundled conductor; {θ''} is the angular acceleration vector of the prototype multi-bundled conductor; In step S2, the expression of the torsional response of the prototype multi-bundled conductor is: The single-degree-of-freedom torsional motion equation is: where θ(t) is the torsional angle matrix of the prototype multi-bundled conductor at time t; φ n is the n-th torsional mode shape of the prototype multi-bundled conductor; q n (t) is the generalized coordinate corresponding to the n-th torsional mode shape of the prototype multi-bundled conductor; respectively are the torsional damping ratio and the torsional circular frequency of the n-th mode of the prototype multi-bundled conductor; q n '(t) is the first-order derivative of the n-th mode generalized coordinate of the prototype multi-bundled conductor with respect to time; q n "(t) is the second-order derivative of the n-th mode generalized coordinate of the prototype multi-bundled conductor with respect to time, and T(t) is the torque vector on the power transmission conductor due to uneven icing. In step S3, the formula used to calculate the generalized parameters of the nth mode of the prototype multi-bundled conductor is as follows: J n = {φ n} T [J]{φ n}(3a) K θn = {φ n} T [K θ ]{φ n}(3b) where J n is the generalized moment of inertia of the prototype multi-bundled conductor of order n, is the generalized torsional stiffness of the prototype multi-bundled conductor of order n, C n is the generalized damping matrix of the prototype multi-bundled conductor of order n; In step S4, the formula used to determine the similar ratio coefficients of the remaining parameters is as follows: where γ θ” , γ g , γ T , γ J and are the angular acceleration scale ratio, the gravity scale ratio, the torsional circular frequency scale ratio, the torque scale ratio, the moment of inertia scale ratio and the torsional stiffness scale ratio of the multi-bundled conductor icing characteristic test device and the prototype multi-bundled conductor, respectively. In step S5, the horizontal spring stiffness K x and the torque loading disc radius R are calculated using the following equations: In the formula, J m is the moment of inertia of the multi-bundled conductor icing characteristic test device, is the torsional vibration circular frequency of the prototype multi-bundled conductor.

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