CN206313414U - Power transmission line wind side spin tower based on flexible composite - Google Patents

Abstract

The utility model discloses a windproof deflection pole tower of a power transmission line based on a flexible composite material, and specifically designs a structure of a windproof deflection pole tower of a power transmission line. It includes the tower body, the two ends of the top of the tower body are connected with cross-arms, and also includes a flexible arresting cable, which is composed of joint tower fittings connected in sequence from top to bottom, the first flexible composite insulator with umbrella skirt , the flexible composite insulator without shed, the second flexible composite insulator with shed, the first connecting fitting, the cable, the second connecting fitting, the spring and the third connecting fitting, the free end of each conductor cross-arm is connected with The middle parts of the tower body are connected with the flexible arresting cable, the connecting tower extension fittings are connected with the spare end of the wire cross arm, and the third connecting fittings are connected with the middle part of the tower body. The utility model avoids the wind deflection flashover problem of the wire to the pole tower in previous projects, and improves the safety and reliability of the power transmission line.

Description

Windproof towers for transmission lines based on flexible composite materials

technical field

The utility model relates to a structure of a windproof deflection pole tower for a power transmission line, in particular to a windproof deflection pole tower for a power transmission line based on flexible composite materials.

Background technique

The single-circuit straight poles and towers of UHV/EHV overhead transmission lines in my country mostly adopt wine glass or cat head structure, and the side conductors mostly use I-type insulator strings. Under extreme windy conditions, the above-mentioned existing I-type insulator strings are prone to deflection, which makes the existing UHV/UHV overhead transmission line straight poles vulnerable to extreme weather, so that the side of the UHV/UHV overhead transmission line Wind deflection flashover accidents of phase conductors show a high incidence trend.

In the power network, the use of suspension insulator strings is very large, and its wind deflection under wind load has a great impact on the safe operation of transmission lines. Overhead transmission lines are an important part of the power grid. They are distributed in open fields, valleys and hills, and river networks. Overhead transmission lines are mainly composed of poles (poles and iron towers), conductors, ground wires, insulators and fittings. When there is a horizontal wind load or a horizontal component force of the wire acting on the suspension insulator string, the suspension insulator string will produce lateral deflection. This deflection may make the live part at the lower end of the suspension insulator string close to the tower component. When the distance between the charged body and the tower is less than the required air gap, wind deflection discharge will occur, resulting in energy loss and power failure.

Because overhead transmission lines are exposed to the atmosphere all year round, they are directly affected by climate changes such as strong winds, icing, and sudden cooling and sudden heating, as well as environmental conditions such as strong electromagnetic fields, strong mechanical forces, and severe external erosion, which can easily lead to damage to the conductors in the lines. Damage and broken strands; joint heating caused by poor contact due to oxidation, corrosion, etc.; one-phase disconnection; . Among them, the wind deflection flashover of hanging insulator strings is a more prominent category in power grid faults in recent years. According to relevant literature, during the five years from 1999 to 2003, there were more than 260 wind-biased discharges on lines greater than 110kV in the State Grid system, including 33 cases of wind-biased discharges on 500kV lines, involving Jiangsu, Zhejiang, Anhui, Hubei, Henan, Shandong, Shanxi, Beijing, Hebei, Inner Mongolia, Heilongjiang, Liaoning and other provinces and municipalities. Since 2004, the wind-biased discharge of 500kV lines has increased significantly. From January to July, there were 21 cases, of which 19 were wind-biased flashovers of straight-line towers, involving areas including Henan, Jiangsu, Shanxi, Shandong, Hunan, Hubei, Beijing and other regions . At the same time, the 500kV line of China Southern Power Grid Corporation also had multiple wind-biased flashover accidents; the Tiandu-Longpo 110kV line and Linwang-Longpo 110kV line of a naval force in Sanya had frequent wind-biased line trip failures. Because the line is not easy to reclose after being discharged due to wind deflection, it seriously affects and threatens the safe operation of the power grid system, and at the same time causes huge economic losses. For example, at 4 pm on August 14, 2013 (local time in the United States), a large-scale blackout occurred in Manhattan, New York City, and then affected parts of the eastern United States and Canada, paralyzing industrial production, commercial activities and transportation. In view of the importance of EHV/UHV transmission lines, in order to ensure the safe operation of HV transmission lines, it is necessary to conduct in-depth research on EH/UHV transmission line anti-wind deviation measures and improve the reliability and economy of transmission lines.

With the increase of the voltage level of EHV/UHV lines, the length of insulator strings increases accordingly. The use of V-shaped insulator strings puts forward very high requirements on the length of straight tower cross arms and tension tower jumper brackets, which causes tower weight increase; while using conventional I-type insulator strings, the length of the cross-arm of the tower is mainly controlled by the wind deflection gap, resulting in an increase in the horizontal spacing of lines and an increase in the width of the corridor. Significantly reduced, the advantage is not obvious, and the wind deflection of wind deflection flashover is increased at the same time.

In recent years, due to the frequent occurrence of wind flashovers, it has remained high. In order to build a stronger power grid, it is imminent to study the wind deflection optimization of transmission line towers.

Therefore, it is necessary to analyze and study the wind deflection protection technology of EHV/UHV transmission lines, and put forward the technical idea of wind deflection design for high voltage lines, reduce the failure rate of power grid, improve the reliability and safety of wind deflection protection lines, and provide stable production and life for the society. Provide a strong guarantee for smooth development.

At present, the existing technology usually adopts one of the following two methods to solve the above-mentioned side-phase conductor wind deflection flashover problem: the first is to increase the length of the conductor cross-arm or to use V-shaped insulator strings; Measures to install windproof stay wires or additional support insulators. However, the above-mentioned first technical solution has the problem that the cost of the transmission line and the width of the corridor will be greatly increased. The existence of the above-mentioned second method will restrict the movement of conductors and fittings. Under the influence of long-term wind vibration, the activities of conductors and fittings are susceptible to fatigue damage.

Utility model content

The purpose of the utility model is to provide a windproof tower for transmission lines based on flexible composite materials, so as to solve the problem that the current straight towers of UHV/UHV overhead transmission lines are easily affected by extreme weather, and wind deflection flashover accidents frequently occur.

In order to achieve the above purpose, the technical solution of the present utility model is: a windproof pole tower for transmission lines based on flexible composite materials, including a tower body, and both ends of the top of the tower body are connected with cross-arms of wires, and it is characterized in that: it also includes flexible arresting cables , the flexible arresting cable is sequentially connected from top to bottom by the joint tower extension fittings, the first flexible composite insulator with shed, the flexible composite insulator without shed, the second flexible composite insulator with shed, the first connection Fittings, pull cables, second connecting fittings, springs and third connecting fittings are formed by connecting the flexible arresting cable between the free end of each conductor cross-arm and the middle part of the tower body, and the connecting tower extension fittings and The spare ends of the conductor cross-arms are connected at the ends, and the third connection fittings are connected with the middle part of the tower body.

The utility model is mainly used for straight pole towers in super/ultra-high voltage transmission lines. Based on the flexible composite material arresting cable on the tower body, the wind deflection of the transmission line insulator strings is prevented, and the wind deflection flashover problem of the wire to the tower occurs in previous projects. , improve the safety and reliability of transmission lines, and at the same time reduce the width of transmission line corridors in windy areas, which has good practical value.

Description of drawings

Fig. 1 is the structural representation of the utility model.

Figure 2 is a schematic structural view of the flexible arresting cable.

Fig. 3 is a schematic diagram of force analysis of the utility model.

Fig. 4 is a schematic diagram of force analysis of the utility model.

In the figure, 1-tower body, 2-conductor cross arm, 3-flexible arresting cable, 31-tower extension fittings, 32-flexible composite insulator with shed, 33-flexible composite insulator without shed, 34-second Flexible composite insulator with shed, 35-the first connecting fitting, 36-the cable, 37-the second connecting fitting, 38-the spring, 39-the third connecting fitting.

detailed description

The implementation of the utility model will be described in detail below in conjunction with the accompanying drawings, but they do not constitute a limitation of the utility model, and are only examples. At the same time, the advantages of the utility model are made clearer and easier to understand through description.

Referring to the accompanying drawings, it can be seen that the windproof deflection pole tower of transmission lines based on flexible composite materials includes a tower body 1, and the top ends of the tower body 1 are connected with conductor cross arms 2, and is characterized in that it also includes flexible arresting cables 3, the flexible The arresting cable 3 is composed of connecting tower extension fittings 31 sequentially connected from top to bottom, the first flexible composite insulator with shed 32, the flexible composite insulator without shed 33, the second flexible composite insulator with shed 34, the first Connecting fittings 35, pull cables 36, second connecting fittings 37, springs 38 and third connecting fittings 39, the flexible arresting cables 3 are connected between the spare end of each conductor cross arm 2 and the middle part of the tower body 1 In this configuration, the connecting tower extension fitting 31 is connected to the free end of the wire cross arm 2 , and the third connecting fitting 39 is connected to the middle part of the tower body 1 .

During actual work, the construction steps of the present utility model are as follows:

1. Determine the tower planning and tower use conditions according to the actual engineering conditions. The actual engineering conditions include the allowable horizontal span, vertical span, vertical coefficient, number of rotation angles, altitude, meteorological conditions, terrain, ground wire parameters and actual ranking status;

Specifically: according to the altitude of the project, meteorological conditions, terrain, ground wire parameters, actual alignment, etc., determine the tower planning and tower use conditions. For example, within an altitude of 1500m, the design wind speed is 31m/s, the conductor adopts a 6-split LGJ-400/50 single-circuit line, and the terrain is flat. According to the economic and technical comparison of the ranking results, engineering experience and typical design, the type 1 linear tower The operating conditions are horizontal span of 450m, vertical span of 600m, rotation angle of 0°, calculated height of 48m, etc.

2. Determine the length of the wire suspension string through the insulation coordination requirements. The insulation coordination requirements include the selection of insulators and tower head air gaps that meet the electrical insulation requirements.

In actual work, specifically:

(1) Insulation configuration principle (select appropriate insulator type)

The following aspects should be paid attention to in the process of selecting the appropriate insulator type:

1) Pay attention to the forward-looking principle of insulation allocation. Insulation allocation should not only consider the current pollution situation, but also combine the local economic and environmental development conditions to reasonably determine the insulation allocation principle.

2) Under the current conditions, for newly-built 500kV (including 330kV) and above power transmission and transformation projects, in principle, the level 0 and level 1 pollution areas should be equipped with the first-level insulation configuration, and the level Ⅱ, Ⅲ and Ⅳ pollution areas should be configured according to the upper limit.

(2) Classification of pollution levels

a Principle of pollution area division

According to the provisions of GB/T16434-1996 "High Voltage Overhead Lines, Power Plants, Substations Environmental Pollution Classification and External Insulation Selection Standard" and Q/GDW152-2006 "Power System Pollution Classification and External Insulation Selection Standard".

b Contaminated area division

According to the polluted area distribution map and on-site pollution source investigation, determine which category of polluted area along the line is a, b, c, d, e in Table 1.

Table 1 Creepage specific distance for each pollution level

In the engineering insulation configuration, the creepage specific distance of all levels of polluted areas shall be taken as the upper limit, for example, the uniform creepage specific distance of the d-level polluted area shall be determined as 50.4mm/kV, and the unified creepage specific distance of the e-level polluted area shall be determined as 59.8mm/kV .

(3) Selection of insulators

According to the design principle of external insulation of transmission lines, the selection of insulators should meet the requirements of power frequency voltage, operating overvoltage and lightning overvoltage at the same time. Since the selection of the number of line insulators mainly depends on the pollution withstand voltage characteristics under power frequency voltage, the number of insulators is generally selected according to the pollution performance, and then the operation and lightning impulse performance are checked.

For the selection of composite insulators, the creepage distance and structural height of the composite insulators are generally determined according to the requirements of the regulations after selecting the number of pieces according to the porcelain insulators.

Calculate the number of insulators according to the leakage ratio method recommended by "Code for Design of 110kV～750kV Overhead Transmission Lines" (GB50545-2010), and correct for altitude.

(1) The number of insulators per string of lines determined by the power frequency voltage creepage distance shall meet the requirements of the following formula:

In the formula:

m—number of insulators per string;

U _m —system rated voltage, kV;

λ—creepage specific distance, cm/kV;

L0—geometric creepage distance of each suspension insulator, cm;

Ke—the effective coefficient of insulator creepage distance, mainly determined by the effectiveness of various insulator creepage distances in testing and operation to improve the pollution withstand voltage.

(2) In high-altitude areas, as the altitude increases or the air pressure decreases, the flashover voltage of dirty insulators decreases. The number of pieces of suspension insulator strings in high-altitude areas should be calculated according to the following formula:

In the formula:

n _H ——Number of insulators required for each string of insulators in high-altitude areas;

H——altitude above sea level (km);

m ₁ —— characteristic index, which reflects the degree of influence of air pressure on pollution flashover voltage, determined by experiment.

According to the consideration of d and e-level pollution areas, the corresponding number of insulators for 750kV transmission lines is shown in Table 2:

Table 2 Number of Disc Insulators after Altitude Correction

b Check the number of insulators according to the operating overvoltage

For example: 50% discharge voltage U _50% of positive polarity operating impulse voltage wave 50% of 750kV side-phase wire (using I string) wind deflection line wire to tower air gap shall meet the requirements of the following formula:

U _50% ≥K ₃ U _S ＝1.27×1.8×800/√3/2＝1493kV

In the calculation, take the insulation coordination coefficient—k3=1.27, Us——operating overvoltage (kV);

After calculation, the 50% discharge voltage U ₅₀ of the positive polarity operation impulse voltage wave is 1493kV.

Correct the 50% discharge voltage U ₅₀ of the impulse voltage wave of positive polarity operation at high altitude, as shown in Table 3.

Table 3 High altitude positive polarity operation impulse voltage wave 50% discharge voltage U ₅₀

altitude 1000m 2000m 50% discharge voltage 1587 1688

According to the conclusions of relevant research institutes at home and abroad, the insulator string length corresponding to the 50% discharge voltage of the impulse voltage wave at an altitude of 1000-2000m is between 4-5m, which is much smaller than the structural height corresponding to the number of insulators selected according to the pollution withstand voltage. The number of insulator pieces determined by the power frequency creepage ratio meets the requirements under the condition of operating overvoltage.

c Check the insulator sheet according to the lightning overvoltage

Considering the insulation length of the shortest insulator string configured above, the lightning discharge voltage is 3600-3800kV. When the line span is 450m, the nominal height of the tower is 48m, the protection angle of the lightning protection line is 10°, the impact grounding resistance is 7-15Ω, and the annual average thunderstorm day is 40 days, the lightning withstand level when the lightning strikes the top of the tower is about 178-222kA, The lightning trip rate is about 0.101-0.168 times/100km·y, which can meet the requirements of lightning overvoltage.

d recommended insulators

The polluted area shall be in accordance with the d and e class polluted areas, and according to the selection results of the number of disc insulators, according to the "Code for Design of 110kV ~ 750kV Overhead Transmission Lines", the creepage distance of composite insulators in heavily polluted areas shall not be less than 3 times the minimum required value of disc insulators /4 and not less than 2.8cm/kV, and the structure height is not less than 80%. Composite insulators in class e polluted area shall be adjusted according to the parameters of synthetic insulators in class d polluted area, without increasing the structure height.

According to the configuration principle, the parameters of the synthetic insulator of the suspension insulator string can be selected as shown in 4:

Table 4 Suspended insulator (synthetic) parameter list

(4) Determination of the air gap at the tower head

According to the "Code for Design of 110kV～750kV Overhead Transmission Lines" and combined with the design experience of other 750kV lines, the air gap of 750kV single-circuit lines is shown in Table 5.

Table 5 recommended air gap (m)

According to the strength of insulators, the number of connections, the safety factor requirements of fittings, the type of pole and tower hanging points, the connection of fittings and other factors, the length of fittings for the suspension insulator strings is used to comprehensively determine the length of the suspension insulators.

Through the above analysis, the flexible composite insulator with shed is consistent with the parameters in Table 4, the structure height is 7150mm, and the air gap under each working condition is consistent with Table 5.

c) Line corridor:

The determination of the corridor width of the 750kV transmission line mainly considers the following factors:

1) The horizontal distance from the wire projection to the house should not be less than 6m, that is, all houses within 6m from the side wire must be demolished;

2) For houses that are more than 6m away from the side conductors, the maximum undistorted electric field intensity at a height of 1.5m above the ground where the house is located should not exceed 4kV/m when there is no wind, and the clearance distance should be guaranteed to be 11.0m when the maximum wind deflection occurs; otherwise, they should be demolished;

Generally, the side conductor + safety distance (for example: 500kV side conductor 5m, 750kV side conductor 6m, 1000kV side conductor 7m) is used as the boundary range of the line corridor width.

4. Determine the size of the tower window according to the requirements of electrical clearance and windage blocking angle;

By setting the maximum wind angle limit (θ1), according to the requirements of the electrical insulation length of the flexible arresting insulator, combined with the layout of the tower, the overall length of the arresting cable is determined, and then the size of the tower head is determined.

The stop spring is designed in the arresting cable to ensure that when the wire is at extreme wind speed, the arresting device will release the wind load of the insulator string through the action of the stop spring and the bending of the flexible arresting net (cable), and limit the maximum wind deflection angle of the insulator string to θ1 within.

Since the windage prevention device controls the maximum windage angle of the insulator string within θ1, the conductor gap is controlled by the following conditions:

1. Lightning overvoltage gap;

2. Operating overvoltage gap;

3. The live working gap;

4. The power frequency voltage gap under the condition of θ1 wind deviation (special requirements of this application).

As shown in Fig. 2, Fig. 3, and Fig. 4, the arresting cable’s ultimate force analysis schematic diagram, according to the parallelogram law, the arresting cable’s static force is: F5=F3/sin(θ3-θ4)

θ3 is the arresting limit angle of the arresting cable, and the specific value is set according to the needs, such as 35°;

θ4 is the limit angle between the lower part of the arresting cable and the vertical.

Among them, θ4=θ1-θ5

θ5＝arccos((x2+c2-L2)/2/x/c)

c=(x2+L2-2*x*L*cos(θ3-θ1))0.5

x is the initial total length of the arresting device;

L is the length of the insulator string.

F4＝F5*sin(θ5+θ3-θ1)

5. Determine the length and height of the ground wire support according to the requirements of lightning protection and horizontal offset of the ground wire;

6. Calculate and determine the mechanical strength of the arresting cable and the length and parameters of each component according to the tower head size, insulation coordination requirements, suspension string length and other parameters.

The key of the flexible composite arresting cable is the flexible arresting composite material. Flexible interphase spacer composite insulators for transmission lines have good bending performance and electrical performance, and flexible barrier composite materials can be developed on the basis of flexible interphase spacer composite insulators.

In order to ensure the safety of the line operation and the service life of the arresting cable, the conductor should not collide with the arresting cable under normal wind speed conditions, and the probability of the conductor colliding with the arresting cable can be set to be less than 20%. For example: after calculation, taking the distribution characteristics of strong winds near Urumqi as an example, the probability of wind speed above 21.3m/s is less than 20%, and the calculated swing angle of the insulator string is 39.6 degrees. According to the structure of the 7A5-ZB1 tower and the wind speed control value, the angle between the arresting cable and the vertical direction is set at 40.4 degrees, and the total length of the arresting cable is determined to be 25.6m.

The arresting device is selected to use 2 arresting cables, and the distance between the arresting cables is determined to be 1600mm according to the tower structure. The hanging point at one end is suspended near the hanging point of the insulator string, and the hanging point at the other end is hung at the tower body.

In order to ensure the strength and insulation performance of the flexible composite material, the core rod of the flexible insulator is integrally formed. The outer structure adopts a three-stage structure, and flexible composite insulators with sheds are used at both ends to increase the creepage distance and ensure the insulation coordination requirements. The position where the middle collides with the wire adopts a shedless structure.

According to the insulation configuration requirements, from the point of collision between the composite material and the conductor, the contact point between the flexible composite insulator and the cross arm and the flexible insulator and the cable in the direction of the tower body need to consider the composite insulator with shed, and the dry arc distance is considered as 6600mm.

The dry arc distance of the insulators with sheds at both ends is 6600mm, and the structure height is 7150mm.

Considering that the radius of the protective fittings is 500mm, the contact length after the arresting cable is bent is less than 785mm, and at the same time, the length of the lead wire at the installation position of the arresting cable is 100-300mm. The length of the composite insulator is determined to be greater than 1500mm.

Based on the above, the length of the flexible composite material can be considered as 15800mm.

The type I suspension insulator string is considered to be 8603mm, the length from the hanging point to the center of the split conductor is 8257mm, and the wire inclination is considered to be 100-300mm relative to the installation position of the arresting cable (that is, about 800mm from the center line of the suspension string). In order to ensure that the wire collides with the middle of the shedless flexible composite material, the length of the metal fitting connecting the cross arm is 450mm.

The rated load of the cable should be at least equal to the rated mechanical load of the flexible insulator.

Adjustable fittings such as DB hanging plate and PT hanging plate are added to the connecting fittings to flexibly adjust the length of the flexible arresting cable locally.

According to the structure of the 7A5-ZB1 tower and the wind speed control value, the angle between the arresting cable and the vertical direction is initially determined to be 40.4 degrees, and the total length is initially determined to be 25.6m.

7. Calculate the tower load and complete the tower structure design.

The load acting on the tower can be divided into permanent load, variable load and special load according to its nature.

1. Permanent load: including the self-gravity of the tower, the gravity of wires, insulators, fittings and other fixed equipment.

2. Variable load: including wind load, ice load on wires and insulators, tension of wires and stay wires, temporary loads during construction and maintenance, secondary loads caused by structural deformation, and various vibration dynamic loads.

3. Special loads: including loads caused by broken wires and earthquakes, as well as loads such as unbalanced tension caused by uneven icing in mountainous areas or special terrain areas.

The above loads can be decomposed into lateral loads, longitudinal loads and vertical loads acting on the tower according to the calculation needs.

The calculation of tower load refers to the calculation of the load acting on the tower under different meteorological conditions and external conditions, which is used to determine the material selection, composition, specification, connection method, etc. of the tower components.

During actual work, the novel pole tower is composed of two parts, a flexible arresting cable and an iron tower. The flexible arresting cable is composed of joint towers and extension fittings, flexible composite insulators, springs, cables and connecting fittings and other components. The tower head type of the iron tower can be determined through technical and economic comparison according to the requirements of the phase spacing of the conductors, the electromagnetic environment, and the corridor of the line. The arresting cable is respectively connected to the tower body near the hanging point of the cross-arm wire through the joint tower fittings.

Under extreme windy weather conditions, because the arresting cable physically limits the wind deflection angle of the line to the limit allowable angle, it avoids the flashover discharge accident of the live part to the tower body caused by the strong wind, which can improve the safety and reliability of the line and reduce the line corridor beneficial effect.

The length of the conductor cross-arm and the arrangement angle of the arresting cable shall be designed in accordance with the actual engineering wind distribution law, electrical clearance requirements, and the proposed arresting wind speed. Calculate and determine the mechanical strength of the arresting cable and the length and parameters of each component according to the tower head size, insulation coordination requirements, suspension string length and other parameters. According to the load of the tower and the load of the arresting cable, the structural design of the tower is completed.

Other unspecified parts belong to the prior art.

Claims (1)

1. A transmission line windproof pole tower based on flexible composite materials, including a tower body (1), and the top ends of the tower body (1) are connected with wire cross arms (2), which are characterized in that: each wire cross arm (2 ) and the middle part of the tower body (1) are connected with a flexible arresting cable (3), and the flexible arresting cable (3) is connected successively from top to bottom by joint tower extension fittings (31), The first flexible composite insulator with shed (32), the flexible composite insulator without shed (33), the second flexible composite insulator with shed (34), the first connecting hardware (35), the cable (36) , second connecting fittings (37), springs (38) and third connecting fittings (39), the joint tower extension fittings (31) are connected to the free ends of the wire cross-arms (2), and the third connecting fittings (39) is connected with the middle part of tower body (1).