CN106711905B - Flexible composite material-based wind deflection prevention pole tower for power transmission line and construction method thereof - Google Patents
Flexible composite material-based wind deflection prevention pole tower for power transmission line and construction method thereof Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02G—INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES
- H02G7/00—Overhead installations of electric lines or cables
- H02G7/14—Arrangements or devices for damping mechanical oscillations of lines, e.g. for reducing production of sound
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02G—INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES
- H02G7/00—Overhead installations of electric lines or cables
- H02G7/20—Spatial arrangements or dispositions of lines or cables on poles, posts or towers
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Abstract
The invention discloses a wind deflection prevention tower of a power transmission line based on a flexible composite material, and particularly designs a structure of the wind deflection prevention tower of the power transmission line. The flexible blocking cable is characterized by comprising a tower body, wherein two ends of the top of the tower body are connected with wire cross arms, the flexible blocking cable is connected with the wire cross arms from top to bottom in sequence, the flexible blocking cable is connected with the wire cross arms through a tower connecting extension fitting, a first flexible composite insulator with an umbrella skirt, a flexible composite insulator without an umbrella skirt, a second flexible composite insulator with an umbrella skirt, a first connecting fitting, a inhaul cable, a second connecting fitting, a spring and a third connecting fitting, the flexible blocking cable is connected between the free end part of each wire cross arm and the middle part of the tower body, the tower connecting extension fitting is connected with the free end part of the wire cross arm, and the third connecting fitting is connected with the middle part of the tower body. The invention avoids the wind deflection flashover problem of the wire to the pole tower in the past engineering and provides the safety and reliability of the power transmission line.
Description
Technical Field
The invention relates to a structure of a wind deflection prevention tower of a power transmission line, in particular to a wind deflection prevention tower of a power transmission line based on a flexible composite material. The invention also relates to a construction method of the wind deflection prevention pole tower of the power transmission line based on the flexible composite material.
Background
The single-loop straight line tower of the ultra-high voltage overhead transmission line in China adopts a wine glass type or cat head type structure, and the side wires adopt I-shaped insulator strings. Under extremely high wind conditions, the existing I-shaped insulator string is easy to deviate, so that the existing linear tower of the ultra/ultra-high voltage overhead transmission line is easy to be influenced by extreme weather, and the wind deviation flashover accidents of the side phase conductors of the ultra/ultra-high voltage overhead transmission line are high in incidence.
In the power network, the use amount of the suspension insulator string is large, and the wind deflection of the suspension insulator string under wind load has great influence on the safe operation of the power transmission line. The overhead transmission line is an important part of a power grid, has wide quantity and multiple faces, and is distributed in open fields, hills and river network areas. The overhead transmission line mainly comprises a pole tower (electric pole and iron tower), a wire, a ground wire, an insulator, hardware fittings and the like. When a horizontal wind load or a horizontal component of the wire acts on the string, the string will deflect laterally. Such deflection may cause the live portion at the lower end of the string to approach the tower member, and when the distance of the live body from the tower is less than the desired air gap, wind deflection discharge may occur, resulting in energy loss and power failure.
Because the overhead transmission line is exposed to the atmosphere all the year round, the overhead transmission line is directly influenced by strong wind, icing, quenching and other climate changes, strong electromagnetic field, strong mechanical force, serious external erosion and other environmental conditions, and the damage and strand breakage of the wires in the line are easily caused; the heat of the joint caused by poor contact due to oxidation, corrosion and the like; a phase break; wind deflects the brake; potential safety hazards such as pollution flashover and rain flashover of the insulators bring influence to safe and stable operation of the power grid. Wind deflection flashover of a suspension insulator string is a type that is prominent in recent years in grid faults. According to the related literature, since 2004, wind deflection discharge of a 500kV line is obviously increased, and 21 wind deflection flashovers of a tangent tower are formed in 1-7 months. Because reclosing of the circuit after wind deflection discharge is not easy to succeed, the safe operation of the power grid system is seriously influenced and threatened, and meanwhile, huge economic loss is caused. In view of the importance of the ultra/extra-high voltage transmission line, in order to ensure the safe operation of the high voltage transmission line, it is necessary to further research the wind deflection prevention measures of the ultra/extra-high voltage transmission line and improve the reliability and the economy of the transmission line.
Along with the increase of the voltage class of the ultra/extra-high voltage line, the length of the insulator string is increased along with the increase, and a V-shaped insulator string is adopted, so that very high requirements are put on the lengths of the cross arm of the tangent tower and the jumper bracket of the tension tower, and the weight of the tower is increased; when the conventional I-shaped insulator string is adopted, the length of the cross arm of the tower is mainly controlled by the windage yaw gap, so that the horizontal distance of a line is increased, the width of a corridor is increased, when the conventional I-shaped insulator string is adopted, the length of the cross arm cannot be greatly reduced compared with that of a V-shaped string, the advantages are not obvious, and meanwhile, the windage yaw of windage yaw flashover is increased.
In recent years, windage flashover frequently occurs, and the situation is high. In order to build a stronger power grid, the wind deflection prevention optimization research of the power transmission line tower is urgent.
Therefore, analysis and research on the wind deflection prevention technology of the ultra/extra-high voltage transmission line are necessary, the technical thought of the wind deflection prevention design of the high voltage transmission line is provided, the power grid fault rate is reduced, the wind deflection prevention reliability and safety of the line are improved, and powerful guarantee is provided for stable and smooth development of social production and life.
Currently, the prior art generally adopts one of the following two ways to solve the problem of wind deflection flashover of the side phase conductor: the first is to increase the length of the cross arm of the wire or to use a V-shaped insulator string, and the second is to add a windproof stay wire or a supporting insulator. However, the first technical solution has the problem that the manufacturing cost of the power transmission line and the width of the corridor are greatly increased. The second mode can limit the movement of the wire and the hardware fitting, and the wire and the hardware fitting are easy to be damaged by fatigue under the influence of long-term wind vibration, so that the second mode has engineering allowance potential safety hazard for the operation of the wire.
Disclosure of Invention
The invention aims to provide a wind deflection prevention pole tower of a power transmission line based on a flexible composite material, which solves the problem that the existing single-circuit pole tower of a special/ultra-high voltage overhead power transmission line is easily affected by extreme weather and reduces wind deflection flashover accidents of side phase wires of the single-circuit pole tower of the special/ultra-high voltage overhead power transmission line.
The invention provides a construction method of a wind deflection prevention pole tower of a power transmission line based on a flexible composite material, which solves the problem that the existing special/ultra-high voltage overhead power transmission line pole tower is easily affected by extreme weather, and reduces the wind deflection flashover accidents of wires of the special/ultra-high voltage overhead power transmission line pole tower.
In order to achieve the above purpose, the technical scheme of the invention is as follows: power transmission line wind deflection prevention pole tower based on flexible composite material, including the body of the tower, the top both ends of body of the tower all are connected with wire cross arm, its characterized in that: the flexible blocking cable is formed by sequentially connecting a tower-connecting extension fitting, a first flexible composite insulator with an umbrella skirt, a flexible composite insulator without an umbrella skirt, a second flexible composite insulator with an umbrella skirt, a first connecting fitting, a guy cable, a second connecting fitting, a spring and a third connecting fitting from top to bottom, wherein the flexible blocking cable is connected between the free end part of each wire cross arm and the middle part of the tower body, the tower-connecting extension fitting is connected with the free end part of the wire cross arm, and the third connecting fitting is connected with the middle part of the tower body.
In order to achieve the second object of the present invention, the technical solution of the present invention is: the construction method of the wind deflection prevention pole tower of the power transmission line based on the flexible composite material is characterized by comprising the following steps of: the method comprises the following steps: determining a tower planning and tower use condition according to actual engineering conditions, wherein the actual engineering conditions comprise allowable horizontal span, vertical coefficient, rotation angle degree, altitude, meteorological conditions, topography, ground lead parameters and actual arrangement conditions; step two: determining the length of a wire suspension string through insulation fit requirements, wherein the insulation fit requirements comprise selecting proper insulator types, determining the number of pieces of the insulator strings and the air gap of a tower head, and simultaneously meeting the requirements of working voltage, operation overvoltage and lightning overvoltage; step three: determining the tower head type through technical and economic comparison according to the mutual distance of the wires, the electromagnetic environment and the requirements of a line corridor; the spacing of the wires comprises horizontal lines, horizontal distances or vertical distances between different wires of different loops of the double loops, vertical distances between upper and lower layers of wires and minimum horizontal offset between adjacent wires of the upper and lower layers, wherein the horizontal distances between the wires are calculated according to a first calculation formula, the horizontal distances or the vertical distances between the different wires of the different loops of the double loops are calculated by increasing each parameter by 0.5m according to the first calculation formula, the vertical distances between the upper and lower layers of wires are not less than 75% of the horizontal distances, and the minimum horizontal offset between the adjacent wires of the upper and lower layers is not less than 1.75m; wherein, the first calculation formula is: K i is the coefficient of the suspension insulator string, D is the distance between the horizontal wires, L k is the length of the suspension insulator string, U is the nominal voltage of the system, and f c is the maximum sag of the wires; the electromagnetic environment comprises audible noise check and radio interference check, wherein the requirements of the audible noise check are as follows: when the altitude is not more than 1000m, the audible noise limit value under the wet wire condition is 20m away from the projection of the power transmission line roadside wire, and the audible noise limit value meets the limit value requirement of not more than 55dB; the radio interference check requirements are as follows: when the nominal voltage is 750kV, the radio interference is not greater than 58dB; when the nominal voltage is 500kV, the radio interference is not more than 55dB; when the nominal voltage is 220-330 kV, the radio interference is not more than 53dB; when the nominal voltage is 110kV, the radio interference is not greater than 46dB; the line corridor should meet the following requirements: a) The horizontal distance from the projection of the wire to the house should be not less than 6m, i.e. all houses within 6m from the side wire need to be removed; b) The maximum undistorted electric field strength of the house, which is located at the position 1.5m higher than the ground of the house, of the house except for 6m from the side wires should not be larger than 4kV/m when no wind exists, and the clearance distance is ensured to be 11.0m when the wind deviates maximally, otherwise, the house should be removed. c) Determining the size of a tower window, the length of a wire cross arm and the arrangement angle of a blocking rope according to the electric gap requirement, the windage yaw blocking angle requirement and the like; through designing the related parameters of the limiting spring, the arresting device releases the windage load of the insulator string through the action of the limiting spring and the bending of the flexible arresting rope when the wire is at extreme wind speed, and limits the maximum windage angle of the insulator string within theta 1; step four: determining the size of a tower window, the length of a wire cross arm and the arrangement angle of a blocking rope according to the electric gap requirement, the windage yaw blocking angle requirement and the like; step five: determining the length and the height of a ground wire bracket according to the requirements of lightning protection, horizontal deviation of a ground wire and the like; step six: according to parameters such as tower head size, insulation fit requirement, suspension string length and the like, calculating and determining mechanical strength of the arresting cable and length and parameters of each component part; step seven: and calculating the load condition of the pole tower, and finishing the construction of the pole tower structure.
The invention is mainly used for a straight line tower in an ultra/extra-high voltage transmission line, and based on a flexible composite material blocking rope on the tower body, the wind deflection of the transmission line insulator string is blocked, so that the problem of wind deflection flashover of the transmission line tower by a wire in the past engineering is avoided, the safety and reliability of the transmission line are improved, and meanwhile, the width of a transmission line corridor in a high wind area can be reduced, so that the invention has good practical value.
Meanwhile, the design and production processing technical level of the composite material of the flexible blocking cable can meet engineering application requirements, and the novel wind deflection prevention design scheme based on the rigid support and the flexible blocking composite material has great economic advantages and safety and reliability. The invention is based on domestic composite materials, develops a novel windage yaw prevention design scheme which has independent intellectual property rights and can be applied to ultra/extra-high voltage transmission line engineering, researches and tests and verifies material characteristics, structural types, connection modes, electrical properties, mechanical properties and the like, and is finally applied to practical engineering.
Drawings
Fig. 1 is a schematic structural view of the present invention.
Fig. 2 is a schematic structural view of a flexible barrier cable.
FIG. 3 is a schematic diagram of the force analysis of the present invention.
FIG. 4 is a schematic diagram of a force analysis according to the present invention.
In the figure, the structure comprises a 1-tower body, a 2-wire cross arm, a 3-flexible blocking rope, a 31-tower connecting extension fitting, a 32-flexible composite insulator with an umbrella skirt, a 33-flexible composite insulator without an umbrella skirt, a 34-second flexible composite insulator with an umbrella skirt, a 35-first connecting fitting, a 36-inhaul cable, a 37-second connecting fitting, a 38-spring and a 39-third connecting fitting.
Detailed Description
The following detailed description of the invention is, therefore, not to be taken in a limiting sense, but is made merely by way of example. While making the advantages of the present invention clearer and more readily understood by way of illustration.
As can be seen with reference to the accompanying drawings: power transmission line wind deflection prevention pole tower based on flexible composite material, including tower body 1, the top both ends of tower body 1 all are connected with wire cross arm 2, its characterized in that: the flexible blocking cable 3 is formed by sequentially connecting a tower connecting extension fitting 31, a first flexible composite insulator 32 with an umbrella skirt, a flexible composite insulator 33 without an umbrella skirt, a second flexible composite insulator 34 with an umbrella skirt, a first connecting fitting 35, a guy cable 36, a second connecting fitting 37, a spring 38 and a third connecting fitting 39 from top to bottom, wherein the flexible blocking cable 3 is connected between the free end part of each wire cross arm 2 and the middle part of the tower body 1, the tower connecting extension fitting 31 is connected with the free end part of the wire cross arm 2, and the third connecting fitting 39 is connected with the middle part of the tower body 1.
In actual operation, the construction steps of the invention are as follows:
1. determining a tower planning and tower use condition according to actual engineering conditions, wherein the actual engineering conditions comprise allowable horizontal span, vertical coefficient, rotation angle degree, altitude, meteorological conditions, topography, ground lead parameters and actual arrangement conditions;
Further, pole tower planning and pole tower use conditions are determined according to the altitude, meteorological conditions, terrain, ground wire parameters, actual arrangement conditions and the like of the engineering. For example, within the altitude of 1500m, the wind speed of 31m/s is designed, a 6-split LGJ-400/50 single-loop line is adopted for the wire, the land is flattened, and a 4-type tangent tower and a 4-type tension tower are planned according to economic and technical comparison of arrangement results, engineering experience and typical design, wherein the use condition of the 1-type tangent tower is that the horizontal span is 450m, the vertical span is 600m, the angle degree is 0 degrees, the calling height is 48m and the like.
2. The wire overhang string length is determined by insulation fit requirements including selecting insulators and tower head air gaps that meet electrical insulation requirements.
The actual working process is as follows:
(1) Principle of insulation arrangement (selection of appropriate insulator types)
The following should be noted in selecting the appropriate insulator pattern:
1) Focusing on the prospective of the insulation configuration principle, the insulation configuration not only needs to consider the current pollution condition, but also reasonably determines the insulation configuration principle by combining the local economic and environmental development conditions.
2) Under the current condition, the first-level insulation configuration is improved for the 0-level and I-level pollution areas in the newly built 500kV (including 330 kV) power transmission and transformation engineering and above in principle, and the II-level, III-level and IV-level pollution areas are configured according to the upper limit.
(2) Pollution grading
A dirty region dividing principle
The method is implemented according to the specification of GB/T16434-1996 'high-voltage overhead lines and power plants, substation environment pollution area classification and external insulation selection standard', and Q/GDW152-2006 'electric power system pollution area classification and external insulation selection standard'.
B dirty region division
And determining which of the classes a, b, c, d and e in the table 1 is the level of the pollution area along the line according to the pollution area distribution diagram and the on-site pollution source investigation.
Table 1 creepage distance for each contamination level
The creepage ratio distance of each stage of pollution area is the upper limit value when the engineering insulation configuration is carried out, for example: the uniform creepage distance of the d-level sewage area is determined to be 50.4mm/kV, and the uniform creepage distance of the e-level sewage area is determined to be 59.8mm/kV.
(3) Insulator selection
According to the design principle of external insulation of the transmission line, the selection of the number of the insulators simultaneously meets the requirements of power frequency voltage, operation overvoltage and lightning overvoltage. The number of the insulators of the 750kV line is mainly selected according to the pollution withstand voltage characteristic under the power frequency voltage, so that the number of the insulators is generally selected according to the pollution performance, and the operation and the lightning impulse performance are checked.
For composite insulator selection, the creepage distance and the structure height of the composite insulator are generally determined according to the rule requirements after the number of the porcelain insulators is selected.
And calculating the number of the insulators according to a leakage ratio distance method recommended by 110 kV-750 kV overhead transmission line design specifications (GB 5045-2010), and carrying out altitude correction.
(1) The number of insulator sheets in each string of a line determined by the power frequency voltage creepage distance meets the following formula requirement:
Wherein:
m-the number of insulator sheets in each string;
U m -rated voltage of system, kV;
Lambda-creepage ratio distance, cm/kV;
l0-geometric creepage distance of each suspension insulator, cm;
the effective coefficient of Ke-insulator creepage distance is mainly determined by the effectiveness of various insulator creepage distances in improving pollution withstand voltage in test and operation.
(2) In high altitude areas, as altitude increases or barometric pressure decreases, flashover voltage of the dirty insulator decreases. The number of pieces of the suspension insulator string in the high altitude area is preferably calculated according to the following formula:
Wherein:
n H -the number of pieces required by each string of insulators in the high-altitude area;
H—altitude (km);
m 1 -a characteristic index which reflects the extent to which air pressure affects the pollution flashover voltage, as determined by experimentation.
According to d, e-class pollution areas, the corresponding number of the insulator sheets of the 750kV power transmission line is shown in table 2:
TABLE 2 configuration of disc insulator counts after altitude correction
B checking the number of insulator sheets according to the operation overvoltage
Such as: the positive polarity operation impulse voltage wave 50% discharge voltage U 50％ of the line wire to the tower air gap after the 750kV side phase wire (I string) is winded should meet the following formula requirement:
Taking insulation coordination coefficient-k3=1.27 in calculation, us-operation overvoltage (kV);
The positive polarity operating shock voltage wave 50% discharge voltage U 50 was calculated to be 1493kV.
The high altitude positive polarity operating shock voltage wave 50% discharge voltage U 50 was corrected as shown in table 3.
TABLE 3 high altitude positive polarity operating shock voltage wave 50% discharge voltage U50
| Elevation of the sea | 1000m | 2000m |
| 50% Discharge voltage | 1587 | 1688 |
According to the conclusion of relevant research units at home and abroad, the insulator string length corresponding to 50% discharge voltage of the operating impact voltage wave at the altitude of 1000-2000 m is between 4-5m, the corresponding structure height is determined according to the power frequency creepage ratio distance, and the requirements under the condition of operating overvoltage are met.
C checking insulator sheet according to lightning overvoltage
The lightning discharge voltage is 3600 to 3800kV in consideration of the insulation length of the shortest insulator string configured as described above. When the line span is 450m, the tower calling height is 48m, the lightning protection angle is 10 degrees, the impulse grounding resistance is 7-15 omega, and the annual average thunderstorm day is 40 days, the lightning-resisting level at the top of the lightning stroke is about 178-222 kA, the lightning stroke tripping rate is about 0.101-0.168 times/100 km.y, and the lightning overvoltage requirement can be met.
D recommended number of insulator sheets
The creepage distance of the composite insulator in the heavy pollution area is not less than 3/4 and not less than 2.8cm/kV of the minimum required value of the disc type insulator, and the structural height is not less than 80 percent according to the design specification of the overhead transmission line of 110 kV-750 kV and the selection result of the number of the disc type insulators in the pollution area according to the d and e grade pollution area. The e-stage pollution area composite insulator is adjusted and climbed according to the parameters of the d-stage pollution area composite insulator, and the structural height is not increased.
According to the configuration principle, the parameters of the suspension insulator string composite insulator can be selected as shown in 4:
TABLE 4 suspension insulator (composite) parameter table (altitude 1000 m)
By the analysis, taking a 750kV line as an example, the flexible composite insulator with the umbrella skirt is consistent with the parameters of the table 4, the structural height is 7150mm, and the air gap under each working condition is consistent with the table 5.
(4) Determination of tower head air gap
According to 110 kV-750 kV overhead transmission line design specifications and combining with design experience of other 750kV lines, the air gap of the 750kV single-circuit line is shown in table 5.
Table 5 recommends air gap (m)
According to the factors of the strength, the number of the joints, the safety coefficient requirement of the hardware fittings, the hanging point type of the pole tower, the hardware fitting connection and the like of the insulator, the length of the hardware fitting matched with the suspension insulator string is determined comprehensively.
3. Determining the tower head type through technical and economic comparison according to the requirements of the mutual distance, the electromagnetic environment and the line corridor;
a) Phase interval requirement:
the horizontal line-to-line distance of the wire is preferably calculated according to the following formula:
Wherein:
ki: the coefficient of the suspension insulator string preferably meets the specifications of Table 6
D: distance between horizontal wires (m)
Lk: suspension insulator string length (m)
U: system nominal voltage (kV)
Fc: maximum sag (m) of wire
TABLE 6 ki coefficients
| Suspension insulator string pattern | I-I string | I-V string | V-V string |
| ki | 0.4 | 0.4 | 0 |
The horizontal or vertical distance between the different phase conductors of the different loops of the dual loop should be increased by 0.5m as specified above. The vertical distance between the upper and lower layer wires should be not less than 75% of the horizontal distance. The minimum horizontal offset between adjacent wires of the upper and lower layers should not be less than 1.75m.
B) Electromagnetic environment requirements:
(1) Audible noise check
At altitudes not exceeding 1000m, the audible noise limit under wet wire conditions meets the limit requirement of not more than 55dB at 20m from the outside of the projection of the power line roadside wire.
For audible noise in high altitude areas, the audible noise level is modified by 1dB per 300m of elevation.
(2) Radio interference check
At altitudes not exceeding 1000m, the radio interference limits at 20m outside the projection of the power line roadside conductor and 2m high from ground and at a frequency of 0.5MHz should meet the following table:
c) Line corridor:
The determination of the corridor width of the power transmission line mainly takes the following factors into consideration:
1) Ensuring the electric clearance requirement when the wire is maximally winded;
2) Ensuring that the radio interference and audible noise level does not exceed a prescribed value;
The control of the line corridor is mainly the control of radio interference, audible noise level and electric field. Through optimization of conductor selection and tower size, the radio interference and audible noise level can meet the requirements of 110-750kV overhead transmission line design Specification (GB 5045-2010). The limit of the influence of the high-voltage power line electric field on the environment around the line in China is that the maximum undistorted field intensity at the high position of 1.5 meters away from the ground outside the side phase conductor is not more than 4kV/m.
From the above analysis, the present project makes specific assumptions about determining corridor width as follows:
1) The projection of the wire to the horizontal distance engineering allowance of the house (e.g.: 500kV side lead 5m,750kV side lead 6m and 1000kV side lead 7 m), and all houses need to be removed;
2) The allowable range of the distance wire engineering (such as: the maximum undistorted electric field intensity of the house except the 500kV side lead 5m, the 750kV side lead 6m and the 1000kV side lead 7 m) at the high position of the ground of the house is not more than 4kV/m when no wind exists, otherwise, the house is removed;
the boundary range of the line corridor width is generally defined by the edge conductor + the safety distance (e.g., 500kV edge conductor 5m,750kV edge conductor 6m,1000kV edge conductor 7 m).
4. Determining the size of a tower window, the length of a wire cross arm and the arrangement angle of a blocking rope according to the electric gap requirement, the windage yaw blocking angle requirement and the like;
And setting the maximum windage yaw limit (theta 1), and determining the overall length of the arresting cable according to the electrical insulation length requirement of the flexible arresting insulator and the arrangement of the pole tower, thereby determining the size of the tower head.
Through designing the relevant parameter of the limiting spring, the arresting device releases the windage load of the insulator string through the action of the limiting spring and the bending of the flexible arresting rope when the wire is in extreme wind speed, and limits the maximum windage angle of the insulator string within theta 1.
Because the windage yaw device controls the maximum windage yaw angle of the insulator string to be theta 1, the wire gap is controlled by the following conditions:
1. A lightning overvoltage gap;
2. operating the overvoltage gap;
3. Live working gap;
4. Power frequency voltage gap under the condition of theta 1 windage yaw (special requirement of the application).
As described in the limit stress analysis of the arresting cable in fig. 2, 3 and 4, according to the parallelogram rule, the arresting cable is subjected to static stress: f5 =f3/sin (θ3- θ4)
Θ3 is the limiting angle of the arresting rope, and the specific value is set according to the requirement, such as 35 degrees;
θ4 is the limit angle between the lower part of the arresting rope and the vertical line.
Wherein 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. Determining the length and the height of a ground wire bracket according to the requirements of lightning protection, horizontal deviation of a ground wire and the like;
6. And calculating and determining the mechanical strength of the arresting cable and the length and parameters of each component part according to the parameters such as the size of the tower head, the insulation fit requirement, the suspension string length and the like.
The key point of the flexible composite arresting rope is the flexible arresting composite material. The flexible inter-phase spacer composite insulator for the power transmission line has good bending performance and electrical performance, and the flexible blocking composite material can be developed based on the flexible inter-phase spacer composite insulator.
In order to ensure the running safety of the line and the service life of the arresting rope, the wire should not collide with the arresting rope under the common wind speed condition, and the probability of the wire colliding with the arresting rope can be set to be less than 20%. By calculation, taking the strong wind distribution characteristic near the Uruff as an example, the probability of occurrence 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 included angle between the blocking rope and the vertical direction is set to be 40.4 degrees, and the total length of the blocking rope is preliminarily determined to be 25.6m.
The arresting device adopts 2 arresting ropes, and the interval of the arresting ropes is 1600mm according to the tower structure. One end hanging point is hung near the hanging point of the insulator string, and the other end hanging point is hung at the tower body.
In order to ensure the strength and the insulation performance of the flexible composite material, the flexible insulator core rod is integrally formed. The outer layer structure adopts a three-section structure, and two ends adopt flexible composite insulators with umbrella skirts to increase the creepage distance and ensure the insulation fit requirement. The collision position between the middle part and the lead adopts a structure without umbrella skirt.
According to the insulation configuration requirement, from the collision point of the composite material and the lead, the contact point of the flexible composite insulator and the cross arm and the inhaul cable of the flexible insulator and the tower body direction are considered, and the dry arc distance is considered according to 6600 mm.
The dry arc distance of the insulators with umbrella skirts at the two ends is 6600mm, and the structural heights are 7150mm.
The radius of the protective fitting is considered to be 500mm, the contact length of the arresting rope after bending is less than 785mm, and meanwhile, the allowance length of 100-300mm of the wire declining at the installation position of the arresting rope is considered, so that the length of the flexible composite insulator without the umbrella skirt is determined to be more than 1500mm in order to ensure that the wire collides with the flexible composite material without the umbrella skirt.
In combination with the above, the length of the flexible composite material can be considered as 15800 mm.
The I-type suspension insulator string is considered according to 8603mm, the length from the suspension point to the center of the split conductor is 8257mm, and the conductor is considered according to 100-300mm in a downward inclination relative to the installation position of the arresting cable (namely about 800mm from the center line of the suspension string). In order to ensure that the wires collide with the middle part of the umbrella-skirt-free flexible composite material, the length of a fitting at the connecting part of the cross arm is 450mm.
The rated load of the inhaul cable is at least equal to or more than the rated mechanical load of the flexible insulator.
And an adjustable hardware fitting such as a DB hanging plate and a PT hanging plate is added in the connecting hardware fitting so as to locally and flexibly adjust the length of the flexible arresting cable.
According to the structure of the 7A5-ZB1 tower and the wind speed control value, the included angle between the blocking rope and the vertical direction is initially set to be 40.4 degrees, and the total length is initially determined to be 25.6m.
7. And calculating the load condition of the pole tower, and finishing the construction of the pole tower structure.
The load acting on the tower can be classified into a permanent load, a variable load and a special load according to its properties.
1. Permanent load: the self-gravity of the pole tower, the gravity of the electric wire, the insulator and the hardware fitting and the gravity of other fixing equipment are included.
2. Variable load: the device comprises wind load, ice coating load on the electric wire and the insulator, tension of the electric wire and the pull wire, temporary load during construction and maintenance, secondary load caused by structural deformation and various vibration dynamic loads.
3. Special load: including loads caused by wire breakage and loads caused by earthquakes, and loads such as unbalanced tension caused by uneven icing in mountainous areas or special terrain.
All the loads can be decomposed into transverse loads, longitudinal loads and vertical loads acting on the tower according to the calculation requirement.
The calculation of the tower load refers to calculating the load acting on the tower under different meteorological conditions and external conditions, and is used for determining the material selection, composition, specification, connection mode and the like of the tower parts.
When in actual work, the novel tower consists of two parts, namely a flexible arresting rope and an iron tower. The flexible arresting cable consists of a connecting tower, an extension fitting, a flexible composite insulator, a spring, a inhaul cable, a connecting fitting and other parts. The tower head type of the iron tower can be determined by technical and economic comparison according to the requirements of the wire phase spacing, the electromagnetic environment, the line corridor and the like. The blocking ropes are respectively connected with the tower body near the hanging points of the cross arm wires through the tower connecting hardware fittings.
Under the extreme meteorological conditions of strong wind, the blocking rope physically limits the wind deflection angle of the line within the limit allowable angle, so that the accident of flashover discharge of the tower body caused by strong wind in the electrified part is avoided, and the method has the beneficial effects of improving the safety and reliability of the line and reducing the corridor of the line.
The length of the wire cross arm and the arrangement angle of the blocking rope are required to be matched and designed according to the requirements of actual engineering strong wind distribution law, electric clearance requirements, planned blocking wind speed and the like. And calculating and determining the mechanical strength of the arresting cable and the length and parameters of each component part according to the parameters such as the size of the tower head, the insulation fit requirement, the suspension string length and the like. And finishing the construction of the tower structure according to the tower load and the blocking rope load.
Other non-illustrated parts are known in the art.
Claims (1)
1. The utility model provides a construction method of transmission line prevent wind and deviate shaft tower based on flexible combined material, transmission line prevent wind and deviate shaft tower based on flexible combined material includes body of the tower (1), and the top both ends of body of the tower (1) all are connected with wire cross arm (2), its characterized in that: a flexible blocking cable (3) is connected between the free end part of each wire cross arm (2) and the middle part of the tower body (1), the flexible blocking cable (3) is composed of a tower connecting extension fitting (31), a first flexible composite insulator (32) with an umbrella skirt, a flexible composite insulator (33) without an umbrella skirt, a second flexible composite insulator (34) with an umbrella skirt, a first connecting fitting (35), a guy cable (36), a second connecting fitting (37), a spring (38) and a third connecting fitting (39), which are sequentially connected from top to bottom, the tower connecting extension fitting (31) is connected with the free end part of the wire cross arm (2), and the third connecting fitting (39) is connected with the middle part of the tower body (1);
the construction method comprises the following steps,
Step one: determining a tower planning and tower use condition according to actual engineering conditions, wherein the actual engineering conditions comprise allowable horizontal span, vertical coefficient, rotation angle degree, altitude, meteorological conditions, topography, ground lead parameters and actual arrangement conditions;
Step two: determining the length of a wire suspension string through insulation fit requirements, wherein the insulation fit requirements comprise selecting proper insulator types, determining the number of pieces of the insulator strings and the air gap of a tower head, and simultaneously meeting the requirements of working voltage, operation overvoltage and lightning overvoltage;
Step three: determining the tower head type through technical and economic comparison according to the mutual distance of the wires, the electromagnetic environment and the requirements of a line corridor;
The spacing of the wires comprises horizontal wires, horizontal distances or vertical distances between the phase wires, vertical distances between the wires at the upper layer and the lower layer, and minimum horizontal offset between the wires at the upper layer and the lower layer, wherein the horizontal distances between the wires are calculated according to a first calculation formula, the horizontal distances or the vertical distances between the wires at different phases of the double loops are calculated according to the increase of each parameter in the first calculation formula by 0.5m, the vertical distances between the wires at the upper layer and the lower layer are not less than 75% of the horizontal distances, and the minimum horizontal offset between the wires at the upper layer and the lower layer is not less than 1.75m;
wherein, the first calculation formula is:
k i is the coefficient of the suspension insulator string, D is the distance between the horizontal wires of the wires,
L k is the length of the suspension insulator string, U is the nominal voltage of the system,
F c is the maximum sag of the wire;
The electromagnetic environment comprises audible noise check and radio interference check, wherein the requirements of the audible noise check are as follows: when the altitude is not more than 1000m, the audible noise limit value under the wet wire condition is 20m away from the projection of the power transmission line roadside wire, and the audible noise limit value meets the limit value requirement of not more than 55dB; the radio interference check requirements are as follows: when the nominal voltage is 750kV, the radio interference is not greater than 58dB; when the nominal voltage is 500kV, the radio interference is not more than 55dB; when the nominal voltage is 220-330 kV, the radio interference is not more than 53dB; when the nominal voltage is 110kV, the radio interference is not greater than 46dB;
the line corridor meets the following requirements:
a) Projecting wires to the horizontal distance engineering allowable range of the house, wherein all houses need to be removed;
b) The maximum undistorted electric field strength of the house which is beyond the allowable range of the wire engineering at the distance from the edge is not more than 4kV/m at the height of 1.5m of the ground where the house is located when no wind exists, otherwise, the house is removed;
step four: determining the size of a tower window, the length of a wire cross arm and the arrangement angle of a flexible blocking rope according to the electric gap requirement and the windage yaw blocking angle requirement;
Setting the maximum wind deflection angle limit theta 1, and determining the overall length of the flexible blocking cable according to the electrical insulation length requirement of the flexible blocking insulator and the arrangement of the pole tower, thereby determining the size of the tower head;
Through designing the related parameters of the limiting spring, the blocking device releases the windage yaw load of the insulator string through the action of the limiting spring and the bending of the flexible blocking cable when the wire is at extreme wind speed, and limits the maximum windage yaw angle of the insulator string within theta 1;
The arresting device adopts two flexible arresting ropes, the distance between the flexible arresting ropes is 1600mm according to the structure of the tower, one end hanging point is hung near the hanging point of the insulator string, and the other end hanging point is hung at the tower body;
step five: determining the length and the height of a ground wire bracket according to lightning protection and the horizontal deviation requirement of the ground wire;
Step six: determining the mechanical strength of the flexible barrier cable and the length and parameters of each component part according to the size of the tower head, the insulation fit requirement and the suspension string length parameter;
Step seven: and calculating the load condition of the pole tower, and finishing the construction of the pole tower structure.
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| CN112100830A (en) * | 2020-08-31 | 2020-12-18 | 季龙三 | Method for calculating tension of iron tower of power transmission line |
| CN116109210B (en) * | 2023-04-11 | 2023-06-30 | 国网浙江省电力有限公司温州供电公司 | Wind resistance evaluation method, device, medium and equipment for transmission line tower |
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