A Safety Assessment Method for Icing Jumping of Transmission Towers in Repeated Icing Zones

Abstract

This invention provides a method for assessing the safety of de-icing jumps in transmission towers in icy zones, comprising the following steps: obtaining the X-direction wind load of the line under icing and 90-degree wind conditions, the X-direction wind load of the line under uneven icing and 90-degree wind conditions, the Z-direction self-weight vertical load of the line, the unbalanced tension generated in the Y-direction of the line under uneven icing, the Z-direction vertical load of the line under icing, the Z-direction vertical load of the line under uneven icing, and the uplift load generated by de-icing in the Z-direction of the line; calculating the tower node loads of the lines in the icing phase, the uneven icing phase, and the de-icing phase; selecting several working conditions that may cause the tower structural components to bear the most unfavorable internal forces as design working conditions; comparing the internal forces of the tower structural components under each design working condition, and selecting the largest internal force as the most unfavorable internal force of the tower structural components; and evaluating the bearing capacity of the components and the deformation of the tower structure based on the most unfavorable internal forces of the tower structural components to obtain quantitative safety assessment results.

Description

Technical Field

[0001] This invention relates to the field of safety assessment technology for de-icing jumps on power transmission towers, and more specifically, to a method for assessing the safety of de-icing jumps on power transmission towers in areas with repeated icing. Background Technology

[0002] With the rapid development of DC transmission lines, the areas they cross are becoming increasingly complex, often traversing frigid regions. In these frigid areas, the ground wires and conductors of the transmission towers are often covered with severe ice due to the characteristics of their circular cross-sections. The ice thickness is generally between 20mm and 80mm. This icing acts as an additional downward load, causing the sag of the lines to increase dramatically and subjecting them to greater effects than under normal operating conditions.

[0003] However, because current is constantly being transmitted through the lines, the internal temperature of the lines is high, while the temperature around the lines is very low. Under this cold-heat coupling environment, the outer layer of ice often experiences sudden de-icing. After the ice is removed, the sag of the lines will suddenly jump upwards, thus applying a jump-up load to the tower structure. This upward effect has not been effectively considered in the design, so it has a significant impact on the safety of the suspension tower and seriously reduces the operational reliability of the transmission tower. According to research, DC suspension towers in heavy icing areas often suffer damage due to de-icing. Currently, there is no systematic evaluation method for the de-icing jump of the tower lines. The lack of a method to assess the impact of the de-icing upward effect on the safety of the tower in heavy icing areas will seriously affect the safety and stability of the transmission system. Summary of the Invention

[0004] The present invention aims to at least address one of the technical problems in the prior art that the design of transmission towers does not take into account the upward pull effect caused by de-icing jumps, and lacks a method to assess the impact of the de-icing upward pull effect in repeated icing areas on the safety of the towers, thus affecting the safe and stable operation of the power transmission system.

[0005] Therefore, the present invention provides a method for assessing the safety of de-icing jumps in lines of transmission towers in overlapping icing zones.

[0006] This invention provides a method for assessing the safety of de-icing jumps in transmission towers operating in overlapping icing zones, comprising the following steps:

[0007] S1. Obtain the X-direction wind load of the line under icing and 90-degree wind, the X-direction wind load of the line under uneven icing and 90-degree wind, the Z-direction self-weight vertical load of the line, the unbalanced tension generated by the line in the Y direction under uneven icing, the Z-direction vertical load of the line under icing, the Z-direction vertical load of the line under uneven icing, and the upward pull load generated by the line under ice removal in the Z direction.

[0008] S2. Calculate the nodal loads of the towers for the ice-covered phase, the uneven ice-covered phase, and the de-icing phase.

[0009] S3. Select several working conditions that may cause the tower structure components to bear the most unfavorable internal forces as design working conditions, and calculate the internal forces of the tower structure components under each design working condition.

[0010] S4. Compare the internal forces of the tower structure components under each design condition, and select the largest internal force as the most unfavorable internal force of the tower structure components.

[0011] S5. Based on the most unfavorable internal forces of the tower structure components, the load-bearing capacity of the components and the deformation of the tower structure are evaluated to obtain quantitative safety assessment results.

[0012] The method for assessing the safety of de-icing jumps in overlapping icing zones of transmission towers according to the above-described technical solution of the present invention may further include the following additional technical features:

[0013] In the above technical solution, S3 includes the following four design conditions:

[0014] First working condition: Under a 90-degree wind load, the right ground wire and right conductor are covered with the design ice thickness, while the left ground wire and left conductor are de-iced;

[0015] The second working condition: Under a 90-degree wind load, the right ground wire and the right conductor are unevenly covered with ice, while the left ground wire and the left conductor are de-iced.

[0016] The third working condition: Under a 90-degree wind load, the right ground wire and the right conductor de-iced, while the left ground wire and the left conductor were unevenly covered with ice.

[0017] The fourth operating condition: Under a 90-degree wind load, the right ground wire and the right conductor de-iced, and the left ground wire and the left conductor de-iced.

[0018] In the above technical solution, during de-icing, the conductor and ground wire are only considered for the pull-out force caused by de-icing and the wind load caused by wind load.

[0019] In the above technical solution, the designed ice thickness is between 20mm and 80mm.

[0020] In any of the above technical solutions, in step S2, the calculation method for the tower node loads in the three directions of the icing phase line is as follows:

[0021] F X =γ0×γ Q ×ψ×W I

[0022] F Y =0

[0023] F Z =γ0×(γ G ×G0+γ Q ×ψ×(G I -G0))

[0024] Where γ0 is the structural importance coefficient; γ G For permanent loads, γ is the partial factor. Q ψ is the variable load combination factor; W is the de-icing variable load combination factor; I G represents the X-direction wind load on the line under icing and 90-degree wind conditions; G0 represents the Z-direction self-weight vertical load on the line; G I The vertical load is oriented Z-direction on the line under the ice cover.

[0025] In the above technical solution, in step S2, the calculation method for the tower node load in the three directions of the non-uniform icing phase line is as follows:

[0026] F X =γ0×γ Q ×ψ×W UI

[0027] F Y =γ0×γ Q ×ψ×ΔT UI

[0028] F Z =γ0×(γ G ×G0+γ Q ×ψ×(G UI -G0))

[0029] Among them, W UI For uneven icing and X-direction wind load under 90-degree wind conditions; ΔT UI The unbalanced tension in the Y direction generated by the line under uneven icing; G UI The Z-direction vertical load is applied to the line under uneven icing.

[0030] In the above technical solution, in step S2, the calculation method for the tower node loads in the three directions of the de-icing phase line is as follows:

[0031] F X =γ0×γ Q ×ψ×W TI

[0032] F Y =0

[0033] F Z =γ0×γ Q ×ψ×G TI

[0034] Among them, W TI For de-icing and X-direction wind loads under 90-degree wind conditions; G TI The upward load generated by the de-icing of the line in the Z direction.

[0035] In the above technical solution, the de-icing and the X-direction wind load W under a 90-degree wind direction are... TI The value can be obtained in the following ways:

[0036] W TI =max(W I W UI );

[0037] When the line is the ground line, the uplift load G generated by the ice removal in the Z direction of the line is... TI for:

[0038] G TI =0.05T Eu

[0039] When the line is a conductor, the uplift load G generated by the ice removal in the Z direction of the line is... TI for:

[0040] G TI =0.1T Cu

[0041] Among them, T Eu T represents the maximum operating tension of the grounding wire. Cu This represents the maximum operating tension of the conductor.

[0042] In any of the above technical solutions, in S3, based on the tower node loads calculated in S2 for the icing phase, uneven icing phase, and de-icing phase, the internal forces of the tower structural members under the corresponding design conditions are calculated using the statically indeterminate structural calculation theory.

[0043] In any of the above technical solutions, in S5, the most unfavorable internal forces of the tower structure components obtained in S4 are compared with the design bearing capacity of the components:

[0044] N max ≤N d

[0045] Where, N d N represents the design load-bearing capacity of the component. max This represents the most unfavorable internal force of the tower structure components under several design conditions.

[0046] In summary, due to the adoption of the above-mentioned technical features, the beneficial effects of the present invention are:

[0047] This paper presents a systematic method for assessing the safety of de-icing jumps of transmission tower lines. It fully considers the impact of the uplift effect caused by de-icing jumps on the safety performance of transmission towers. It is applicable to the safety assessment of DC transmission towers traversing frigid regions. Introducing the de-icing jump safety assessment method of transmission tower lines in heavy icing areas into the design of transmission tower structural components can improve the reliability of transmission tower structural components and prevent damage to DC suspension towers in heavy icing areas.

[0048] The proposed design conditions fully consider the worst-case scenarios faced by the line during operation, and the resulting most unfavorable internal forces of the tower structural components can meet the application scenarios, ensuring the effectiveness of the safety assessment of the tower structural components.

[0049] 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

[0050] 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:

[0051] Figure 1 This is a flowchart of a method for assessing the safety of de-icing and jumping of transmission tower lines in overlapping icing zones, according to an embodiment of the present invention.

[0052] Figure 2 This is a spatial axis view of a DC suspension tower. Detailed Implementation

[0053] 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.

[0054] 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.

[0055] The following reference Figures 1 to 2 This invention describes a method for assessing the safety of de-icing jumps in overlapping icing zones of transmission towers, provided by some embodiments of the present invention.

[0056] Some embodiments of this application provide a method for assessing the safety of de-icing jumps in lines of transmission towers in overlapping icing zones.

[0057] like Figures 1 to 2 As shown, the first embodiment of the present invention proposes a method for assessing the safety of de-icing jumps in transmission towers in overlapping icing zones, comprising the following steps:

[0058] S1. Obtain the X-direction wind load of the line under icing and 90-degree wind, the X-direction wind load of the line under uneven icing and 90-degree wind, the Z-direction self-weight vertical load of the line, the unbalanced tension generated by the line in the Y direction under uneven icing, the Z-direction vertical load of the line under icing, the Z-direction vertical load of the line under uneven icing, and the upward pull load generated by the line under ice removal in the Z direction.

[0059] S2. Calculate the nodal loads of the towers for the ice-covered phase, the uneven ice-covered phase, and the de-icing phase.

[0060] S3. Select several working conditions that may cause the tower structure components to bear the most unfavorable internal forces as design working conditions, and calculate the internal forces of the tower structure components under each design working condition;

[0061] S4. Compare the internal forces of the tower structure components under each design condition, and select the largest internal force as the most unfavorable internal force of the tower structure components.

[0062] S5. Based on the most unfavorable internal forces of the tower structure components, the load-bearing capacity of the components and the deformation of the tower structure are evaluated to obtain quantitative safety assessment results.

[0063] The second embodiment of this invention proposes a method for assessing the safety of de-icing jumps in transmission tower lines in overlapping icing zones, and, based on the first embodiment, such as... Figure 2 The diagram shows a spatial axis view of a DC suspension tower, which comprises five parts: the tower body, ground wire crossarm, conductor crossarm, front and rear ground wires, and front and rear conductors. 前 For the left front of the ground line; EL 后 Behind the left ground line; ER 前 The front side of the right ground line; ER 前 Behind the right ground line; CL 前 For the front side of the left conductor; CL 后 Behind the left conductor; CR 前 The front side of the right conductor; CR 前 It is the rear side of the right conductor.

[0064] The security assessment method includes the following steps:

[0065] S1. Obtain the X-direction wind load W for icing and 90-degree wind lines. I Uneven icing and X-direction wind load W under 90-degree wind conditions UI The self-weight load G0 in the Z-direction of the line, and the unbalanced tension ΔT generated in the Y-direction of the line under uneven icing. UI Under the icing line, Z-direction vertical load G I Uneven icing under Z-direction vertical load G UI The uplift load G generated by the de-icing of the Z-axis line TI ;

[0066] S2. Calculate the tower node loads for ice-covered phase, uneven ice-covered phase, and de-icing phase lines; the lines are divided into ground wires and conductors;

[0067] For icing phase lines, the calculation methods for the tower node loads in the three directions are as follows:

[0068] FX =γ0×γ Q ×ψ×W I

[0069] F Y =0

[0070] F Z =γ0×(γ G ×G0+γ Q ×ψ×(G I -G0))

[0071] Where γ0 is the structural importance coefficient, which is 1.1 for UHV lines and 1.0 for general lines; γ G For permanent loads, the partial factor is taken as 1.2; γ Q ψ is the variable load combination factor, taken as 1.4; ψ is the de-icing variable load combination factor, taken as 0.75; W I G represents the X-direction wind load on the line under icing and 90-degree wind conditions; G0 represents the Z-direction self-weight vertical load on the line; G I The vertical load is oriented Z-direction on the line under the ice cover.

[0072] For lines with uneven icing phases, the calculation methods for the tower node loads in the three directions are as follows:

[0073] F X =γ0×γ Q ×ψ×W UI

[0074] F Y =γ0×γ Q ×ψ×ΔT UI

[0075] F Z =γ0×(γ G ×G0+γ Q ×ψ×(G UI -G0))

[0076] Among them, W UI For uneven icing and X-direction wind load under 90-degree wind conditions; ΔT UI The unbalanced tension in the Y direction generated by the line under uneven icing; G UI The Z-direction vertical load is applied to the line under uneven icing.

[0077] For the de-icing phase line, the calculation method for the tower node loads in the three directions is as follows:

[0078] F X =γ0×γ Q ×ψ×W TI

[0079] F Y =0

[0080] F Z =γ0×γ Q ×ψ×G TI

[0081] Among them, W TI For de-icing and X-direction wind loads under 90-degree wind conditions; G TI The upward load generated by the de-icing of the line in the Z direction.

[0082] De-icing and X-direction wind load W under 90-degree wind conditions TI The values ​​are determined as follows:

[0083] W TI =max(W I W UI );

[0084] When the line is the ground line, the uplift load G generated by the ice removal in the Z direction of the line is... TI for:

[0085] G TI =0.05T Eu

[0086] When the line is a conductor, the uplift load G generated by the ice removal in the Z direction of the line is... TI for:

[0087] G TI =0.1T Cu

[0088] Among them, T Eu T represents the maximum operating tension of the grounding wire. Cu This represents the maximum operating tension of the conductor.

[0089] In W I W UI G0, ΔT UI G UI G TI Under known conditions, the nodal loads on the DC suspension tower in various directions on the front and back sides under the conditions of icing, uneven icing, and de-icing can be calculated using the above methods.

[0090] S3. Select several working conditions that may cause the tower structure components to bear the most unfavorable internal forces as design working conditions, and calculate the internal forces of the tower structure components under each design working condition.

[0091] The design conditions include the following four types:

[0092] First operating condition: Under a 90-degree wind load (parallel to the crossarm direction), the right ground wire (ER) 前 ER 后 ) and right conductor (CR)前 CR 后 ) Covered with thick ice, left ground line (EL) 前 EL 后 ) and left conductor (CL) 前 CL 后 De-icing;

[0093] The second operating condition: Under a 90-degree wind load (parallel to the crossarm direction), the right ground wire (ER) 前 ER 后 ) and right conductor (CR) 前 CR 后 Uneven icing, left ground line (EL) 前 EL 后 ) and left conductor (CL) 前 CL 后 De-icing;

[0094] The third operating condition: Under a 90-degree wind load (parallel to the crossarm direction), the right ground wire (ER) 前 ER 后 ) and right conductor (CR) 前 CR 后 De-icing, left ground line (EL) 前 EL 后 ) and left conductor (CL) 前 CL 后 Uneven icing;

[0095] Fourth operating condition: Under a 90-degree wind load (parallel to the crossarm direction), the right ground wire (ER) 前 ER 后 ) and right conductor (CR) 前 CR 后 De-icing, left ground line (EL) 前 EL 后 ) and left conductor (CL) 前 CL 后 De-icing.

[0096] When removing ice, only the pull-out force caused by ice removal and the wind load caused by wind load are considered for the conductor and ground wire.

[0097] The designed ice thickness is between 20mm and 80mm.

[0098] The tower nodal loads calculated in S2 for the icing phase, uneven icing phase, and de-icing phase are respectively substituted into the above four design conditions. Based on the statically indeterminate structural calculation theory, the internal forces of the tower structural members under the above four de-icing conditions are calculated. N1 is the internal force of the member under the first condition; N2 is the internal force of the member under the second condition; N3 is the internal force of the member under the third condition; and N4 is the internal force of the member under the fourth condition.

[0099] Calculating the internal forces of iron tower structural members using the theory of statically indeterminate structures is a common method in the existing technology for analyzing the stress state of iron tower structural members, and will not be elaborated here.

[0100] S4. Compare the internal forces of the tower structure components under each design condition, and select the largest internal force as the most unfavorable internal force of the tower structure components.

[0101] N max =max(N1,N2,N3,N4)

[0102] S5. Based on the most unfavorable internal forces of the tower structure components, the load-bearing capacity of the components and the deformation of the tower structure are evaluated to obtain quantitative safety assessment results.

[0103] Compare the most unfavorable internal forces of the tower structural members obtained from S4 with the design bearing capacity of the members:

[0104] N max ≤N d

[0105] Where, N d N represents the design load-bearing capacity of the component. max This represents the most unfavorable internal force of the tower structure components under several design conditions.

[0106] Based on the most unfavorable internal forces of the tower's structural components, the deformation of the tower structure can also be assessed. The maximum deformation values ​​in the X, Y, and Z directions are derived from these maximum internal forces, and compared with the deformation limits of the components, thus enabling an assessment of the tower structure's deformation.

[0107] f max ≤f lim

[0108] Among them, f max f represents the maximum deformation (standard value) of the tower in the X, Y, and Z directions; lim The deformation limit for the component is 3 / 1000 of the height for a suspended tower.

[0109] When N max and f max If the above requirements are met, the tower structure is considered to meet the de-icing design requirements and its safety is good. If the requirements are not met, the tower structure is considered to be unsafe and the load-bearing capacity of the tower structure needs to be improved.

[0110] 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.

[0111] Any modifications, equivalent substitutions, improvements, etc., 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 assessing the safety of de-icing jumps in overlapping icing zones of transmission towers, characterized in that, Includes the following steps: S1. Obtain the X-direction wind load of the line under icing and 90-degree wind, the X-direction wind load of the line under uneven icing and 90-degree wind, the Z-direction self-weight vertical load of the line, the unbalanced tension generated by the line in the Y direction under uneven icing, the Z-direction vertical load of the line under icing, the Z-direction vertical load of the line under uneven icing, and the upward pull load generated by the line under ice removal in the Z direction. S2. Calculate the nodal loads of the towers for the ice-covered phase, the uneven ice-covered phase, and the de-icing phase. S3. Select several working conditions that may cause the tower structure components to bear the most unfavorable internal forces as design working conditions, and calculate the internal forces of the tower structure components under each design working condition. S4. Compare the internal forces of the tower structure components under each design condition, and select the largest internal force as the most unfavorable internal force of the tower structure components. S5. Based on the most unfavorable internal forces of the tower structure components, the bearing capacity of the components and the deformation of the tower structure are evaluated to obtain the safety assessment results. In S3, the design conditions include the following four types: First working condition: Under a 90-degree wind load, the right ground wire and right conductor are covered with the design ice thickness, while the left ground wire and left conductor are de-iced; The second working condition: Under a 90-degree wind load, the right ground wire and the right conductor are unevenly covered with ice, while the left ground wire and the left conductor are de-iced. The third working condition: Under a 90-degree wind load, the right ground wire and the right conductor de-iced, while the left ground wire and the left conductor were unevenly covered with ice. The fourth operating condition: Under a 90-degree wind load, the right ground wire and the right conductor de-iced, and the left ground wire and the left conductor de-iced; In step S2, for the de-icing phase line, the calculation method for the tower node loads in the three directions is as follows: in, This is the structural importance coefficient; For variable load combination factors; The variable load combination factor for de-icing; For de-icing and X-direction wind loads under 90-degree wind conditions; The upward load generated by the de-icing of the line in the Z direction.

2. The method for assessing the safety of de-icing jumps in overlapping icing zones of transmission towers according to claim 1, characterized in that, When removing ice, only the pull-out force caused by ice removal and the wind load caused by wind load are considered for the conductor and ground wire.

3. The method for assessing the safety of de-icing jumps in overlapping icing zones of transmission towers according to claim 2, characterized in that, The designed ice thickness is between 20mm and 80mm.

4. A method for assessing the safety of de-icing jumps in overlapping icing zones of transmission towers according to any one of claims 1 to 3, characterized in that, In step S2, for the icing phase line, the calculation method for the tower node loads in the three directions is as follows: in, For permanent load partial factors; For icing and 90-degree wind conditions, the X-direction wind load is considered. The Z-axis self-weight load of the line; The vertical load is oriented Z-direction on the line under the ice cover.

5. The method for assessing the safety of de-icing jumps in overlapping icing zones of transmission towers according to claim 4, characterized in that, In step S2, for lines with uneven icing phases, the calculation method for the tower node loads in the three directions is as follows: in, For uneven icing and X-direction wind load under 90-degree wind conditions; The unbalanced tension in the Y direction generated by the line under uneven icing; The Z-direction vertical load is applied to the line under uneven icing.

6. The method for assessing the safety of de-icing jumps in overlapping icing zones of transmission towers according to claim 5, characterized in that, De-icing and X-direction wind load under 90-degree wind conditions The values ​​are determined as follows: ； When the line is the ground line, the uplift load generated by the ice removal in the Z direction of the line is... for: When the line is a conductor, the uplift load generated by the ice removal in the Z-direction of the line is... for: in, This is the maximum operating tension of the grounding wire; This is the maximum operating tension of the conductor.

7. A method for assessing the safety of de-icing jumps in overlapping icing zones of transmission towers according to any one of claims 1 to 3, characterized in that, In S3, based on the tower node loads calculated in S2 for the icing phase, uneven icing phase, and de-icing phase, the internal forces of the tower structural members under the corresponding design conditions are calculated using the statically indeterminate structural calculation theory.

8. A method for assessing the safety of de-icing jumps in overlapping icing zones of transmission towers according to any one of claims 1 to 3, characterized in that, In S5, the most unfavorable internal forces of the tower structure components obtained from S4 are compared with the design bearing capacity of the components: in, For the design load-bearing capacity of the component, This represents the most unfavorable internal force of the tower structure components under several design conditions.

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