CN108645372B - Large-span transmission conductor suspension point dynamic bending strain measurement method - Google Patents

Abstract

The invention discloses a method for measuring the jogging bending strain of a large-span power transmission wire, comprising the following steps: S1, monitoring the breeze vibration state of the wire, and using a tension sensor to continuously measure the horizontal tension of the wire; S2, monitoring the environmental condition of the overhead transmission line, using the wind speed The measuring instrument continuously measures the wind speed when the wire is running; S3. According to the measured wind speed, use the energy balance method to calculate the characteristic parameters of the wire breeze vibration; S4. Use the amplitude and frequency of the obtained wire breeze vibration to substitute the known inertial force of the wire vibration Solve to obtain the inertial force F when the wire is vibrating stable, replace the inertial force F with the static fulcrum reaction force in the static bending stress relationship at the suspension point considering the wire stiffness, and obtain the dynamic bending stress at the suspension point when the wire vibrates in the breeze. The method estimates the dynamic bending strain of the suspension point by measuring the horizontal tension and wind speed of the running wire, and can measure the dynamic bending strain value of the large-span transmission wire more accurately, thereby avoiding the occurrence of accidents.

Description

A method for measuring long-span transmission wire suspension point-bending strain

technical field

The invention relates to the technical field of on-line monitoring of breeze vibration of overhead wires in the field of electric power, in particular to a method for measuring the bending strain of a large-span power transmission wire by hanging point motion.

Background technique

The breeze vibration of the transmission line is also known as the vortex-induced vibration. When the stable wind with a wind speed of about 0.5m/s ~ 10m/s blows to the transmission line, alternating up and down Karman vortices are generated on the leeward side of the conductor/ground wire, causing up and down crossovers. The variable force acts on the transmission line, causing it to have a regular wave-like reciprocating motion up and down in the vertical plane. The frequency of breeze vibration is between 3Hz and 150Hz, the maximum amplitude is generally not greater than 1 to 2 times the diameter of the transmission line, and the duration of vibration is generally several hours, sometimes more than several days. In engineering, the cross-sectional strain value, that is, the dynamic bending strain value, is often used to evaluate the strength of the breeze vibration due to the bending of the wire when it vibrates. The vibration wave forms a wave node at the suspension point, and the node cannot rotate freely due to the constraint of the suspension clamp, so a larger dynamic bending strain value than the span often occurs, and the fatigue strand of the wire often occurs here.

"Wire Vibration Measurement Standardization" considers that the relative displacement A89 of the wire to the wire clamp at the outlet of the wire clamp at _89mm and the dynamic bending strain at the suspension point of the wire become a linear relationship, and it is related to the vibration frequency, wavelength, tension, span and wire. Factors such as clamping and non-rotation are basically irrelevant. According to this, cantilever beam sensors with simple structure, convenient processing and installation, and good electromechanical coupling characteristics are generally used at present to calculate the dynamic bending strain at the suspension point by measuring the bending amplitude at 89mm of the outlet of the wire clamp. However, according to the comparison of the measured data, the linear relationship is affected by factors such as vibration frequency, amplitude, wire tension and stiffness, and there may be an error of ±50%. For the special conductors used in large spans, the impact is greater, especially when the large span transmission conductors vibrate in the breeze, the horizontal tension of the conductors cannot be considered to remain unchanged, so the dynamic bending at the suspension points of the large span transmission conductors cannot be accurately estimated. strain.

SUMMARY OF THE INVENTION

The object of the present invention is to overcome the deficiencies of the above-mentioned prior art, and for the breeze vibration of the large-span transmission wire, considering the influence of vibration frequency, wavelength, tension, span and wire stiffness, a large-span transmission wire suspension jog bend is provided. A strain measurement method, the method estimates the dynamic bending strain of the suspension point by measuring the horizontal tension and wind speed of the running wire, and can more accurately measure the dynamic bending strain value of the large-span transmission wire, so as to more accurately evaluate the dynamic bending strain of the transmission wire. operating conditions to avoid accidents.

The purpose of the present invention can be realized by following technical scheme:

A method for measuring long-span transmission wire suspension point-bending strain, the method comprises the following steps:

S1. Monitor the breeze vibration state of the wire, use the tension sensor to continuously measure the horizontal tension of the wire, and record the change of the horizontal tension of the wire;

S2. Monitor the environmental condition of the overhead transmission line, and use an anemometer to continuously measure the wind speed when the wire is running;

S3. According to the wind speed measured in step S2, use the energy balance method to calculate the characteristic parameters of the wire breeze vibration, that is, when the breeze vibration is stable, the power of the wind input wire is equal to the self-damping power of the wire, and the relationship between the wind speed and the wire amplitude and frequency is used. Obtain the characteristic parameters of the wire breeze vibration, that is, the amplitude and frequency of the wire breeze vibration;

S4. Estimate the dynamic bending strain at the suspension point of the wire according to step S1 and step S3, that is, use the amplitude A ₀ and frequency f of the obtained wire breeze vibration to substitute the inertial force of the known wire vibration to obtain the inertia when the wire vibration is stable. Force F, the inertial force F is replaced by the static fulcrum reaction force in the static bending stress relationship at the suspension point considering the stiffness of the wire, and the dynamic bending stress at the suspension point when the wire vibrates in the breeze is obtained.

Further, in step S1, it is specifically realized by arranging the tension sensor at the outlet of the wire clamp, and continuously measuring the change of the horizontal tension of the wire through the tension sensor.

Further, the tensile force sensor adopts a fiber grating strain sensor.

Further, in step S2, it is specifically realized by installing the anemometer at the clip of the hanging wire, and continuously measuring the wind speed of the environment where the wire is located by the anemometer.

Further, the specific process of step S3 is:

First, calculate the power P _W of the wind input wire with the following formula:

表示动态升力系数，与风速有关；ρ表示空气密度，单位为kg/m³；V表示风速，单位为m/s；D表示导线外径，单位为m；f表示导线微风振动的频率，单位为Hz；A₀表示导线微风振动的振幅，单位为m；其中动态升力系数

的求解公式如下：In the formula,

Represents the dynamic lift coefficient, which is related to the wind speed; ρ represents the air density, the unit is kg/m ³ ; V represents the wind speed, the unit is m/s; D represents the outer diameter of the wire, the unit is m; f represents the frequency of the wind vibration of the wire, the unit is Hz; A ₀ represents the amplitude of the breeze vibration of the wire, the unit is m; where the dynamic lift coefficient

The solution formula is as follows:

In the formula, s represents the Sterloha number, which is related to the Reynolds number of the cylinder, and is 0.185 to 0.2 in the practical range, and 0.2 is used here;

Then, calculate the self-damping power P _c of the wire. The self-damping of the wire represents the ability of the wire to consume or absorb energy when it vibrates. It is the power consumed by the unit length of the wire. The formula is as follows:

In the formula, y ₀ represents the maximum double amplitude of the wire, and the three coefficients K, β, and α vary with the wire specifications, and can be obtained through the wire self-damping test; such as AACSR-400 steel-cored aluminum alloy stranded wire, K=5.428×10 ^-5 , α=2.967-4.174f×10 ^-3 , β=5.0.

Finally, calculate the amplitude A ₀ of the wire breeze vibration: when other parameters are known, take the frequency f of the wire breeze vibration as the parameter coordinate, and use the maximum double amplitude y ₀ of the wire as the independent variable to draw the wind input power P of the wire The relationship between _W and the self-damping power P _c of the wire, the amplitude y ₀ corresponding to the intersection of the P _W and P _c curves of the same frequency is the stable amplitude of the power balance point, that is, the amplitude A ₀ of the wire breeze vibration; the wire breeze vibration When stable, the vibration frequency f can be expressed as a single function of the wind speed V:

In the formula, s represents the Sterloha number, which is related to the Reynolds number of the cylinder.

Further, the step S4 specifically includes the following process:

S4.1. Calculate the inertial force F when the vibration of the wire is stable within half-wavelength according to the following formula:

Theoretically, when the breeze vibration is stable, f in the formula should be the natural frequency considering the stiffness of the wire, and the present invention considers the transmission wire to be a tensioned beam with small stiffness, and the actual span can reach hundreds of meters, ignoring its own bending stiffness. The inertial force F error for wire vibration is generally not more than 5%, so the calculation of the inertial force is relatively safe;

In the formula, m represents the mass of the wire per unit length, λ represents the wavelength of the vibration of the wire in the gear, the unit is m, and the vibration is stable by the following formula:

In the formula, T ₀ represents the horizontal tension of the wire;

S4.2. Calculate the static bending stress σ at the suspension point considering the stiffness of the wire according to the following formula:

为静态支点反力；In the formula, E represents the elastic coefficient of the wire, refer to the parameters of the wire, for example, the elastic coefficient of the LGJ-800/100 wire is 67000N/mm ² ; J represents the moment of inertia of the wire section, and for a single-strand wire with a diameter of d, J=πd ⁴ /64; C represents the distance from the point of maximum bending stress on the conductor section to the bending neutral layer, where the radius r of the strand refers to the conductor parameters; p ₀ represents the concentrated load applied in the center of the test file, the unit is N ; l represents the gear distance, h represents the height difference of the suspension point,

is the static fulcrum reaction force;

S4.3. Substitute the inertial force F of the wire vibration for the static fulcrum reaction force in the static bending stress relationship at the suspension point considering the wire stiffness, and obtain the dynamic bending stress σ _c at the suspension point when the wire vibrates in the breeze:

The unit of dynamic bending stress σ _c at the suspension point when the wire vibrates in breeze is N/mm ² . According to the relationship between dynamic bending stress and dynamic bending strain, the dynamic bending strain ε _c at the clamp when the wire vibrates in breeze is obtained:

The unit of dynamic bending strain ε _c at the clip is μ _ε when the wire vibrates in breeze.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

The method for measuring the jogging bending strain of a large-span transmission wire provided by the present invention estimates the jogging bending strain of the suspension by measuring the horizontal tension and wind speed of the running wire. On the one hand, it is believed that the horizontal tension of large-span conductors changes at any time under breeze vibration, and the dynamic bending strain value of large-span transmission conductors can be measured more accurately, so as to more accurately evaluate the operation of transmission conductors and avoid accidents. .

Description of drawings

FIG. 1 is a flow chart of a method for measuring the bending strain of a large-span transmission wire suspension point according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of the installation of a related measuring device in the method for measuring the bending strain of a suspension point of a large-span transmission wire according to an embodiment of the present invention.

Among them, 1- pole tower cross arm, 2- pendant insulator string, 3- fiber grating tension sensor, 4- wind speed measuring instrument, 5- overhead transmission line conductor.

Detailed ways

The present invention will be described in further detail below with reference to the embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Example:

Figure 2 shows a schematic diagram of the installation of a related measuring device in the method for measuring long-span transmission wire suspension point-bending strain provided by this embodiment, including a pole tower cross arm (1), a suspension insulator string (2), and a fiber grating tension sensor (3). ), an anemometer (4) and an overhead transmission line wire (5), the flow chart of the method is shown in Figure 1 and includes the following steps:

S1. Monitor the breeze vibration state of the wire, use the tension sensor to continuously measure the horizontal tension of the wire, and record the change of the horizontal tension of the wire; specifically, by arranging the fiber grating tension sensor (3) at the outlet of the wire clamp, and continuously through the fiber grating tension sensor (3) It is realized by measuring the change of the horizontal tension of the wire.

S2. Monitor the environmental condition of the overhead transmission line, and use an anemometer to continuously measure the wind speed when the wire is running; specifically, by installing the anemometer (4) at the clip of the hanging wire, and continuously measuring the wind speed by the anemometer (4) wind speed in the environment.

S3. According to the wind speed measured in step S2, use the energy balance method to calculate the characteristic parameters of the wire breeze vibration, that is, when the breeze vibration is stable, the power of the wind input wire is equal to the self-damping power of the wire, and the relationship between the wind speed and the wire amplitude and frequency is used. Obtain the characteristic parameters of the wire breeze vibration, that is, the amplitude and frequency of the wire breeze vibration; the specific process is: first, calculate the power P _W of the wind input to the wire, the formula is as follows:

表示动态升力系数，与风速有关；ρ表示空气密度，单位为kg/m³；V表示风速，单位为m/s；D表示导线外径，单位为m；f表示导线微风振动的频率，单位为Hz；A₀表示导线微风振动的振幅，单位为m；其中动态升力系数

的求解公式如下：In the formula,

Represents the dynamic lift coefficient, which is related to the wind speed; ρ represents the air density, the unit is kg/m ³ ; V represents the wind speed, the unit is m/s; D represents the outer diameter of the wire, the unit is m; f represents the frequency of the wind vibration of the wire, the unit is Hz; A ₀ represents the amplitude of the breeze vibration of the wire, the unit is m; where the dynamic lift coefficient

The solution formula is as follows:

In the formula, s represents the Sterloha number, which is related to the Reynolds number of the cylinder, and is 0.185 to 0.2 in the practical range, and 0.2 is used here;

Then, calculate the self-damping power P _c of the wire. The self-damping of the wire represents the ability of the wire to consume or absorb energy when it vibrates. It is the power consumed by the unit length of the wire. The formula is as follows:

In the formula, y ₀ represents the maximum double amplitude of the wire, and the three coefficients K, β, and α vary with the wire specifications, and can be obtained through the wire self-damping test; such as AACSR-400 steel-cored aluminum alloy stranded wire, K=5.428×10 ^-5 , α=2.967-4.174f×10 ^-3 , β=5.0.

Finally, calculate the amplitude A ₀ of the wire breeze vibration: when other parameters are known, take the frequency f of the wire breeze vibration as the parameter coordinate, and use the maximum double amplitude y ₀ of the wire as the independent variable to draw the wind input power P of the wire The relationship between _W and the self-damping power P _c of the wire, the amplitude y ₀ corresponding to the intersection of the P _W and P _c curves of the same frequency is the stable amplitude of the power balance point, that is, the amplitude A ₀ of the wire breeze vibration; the wire breeze vibration When stable, the vibration frequency f can be expressed as a single function of the wind speed V:

In the formula, s represents the Sterloha number, which is related to the Reynolds number of the cylinder.

S4. Estimate the dynamic bending strain at the suspension point of the wire according to step S1 and step S3, that is, use the amplitude A ₀ and frequency f of the obtained wire breeze vibration to substitute the inertial force of the known wire vibration to obtain the inertia when the wire vibration is stable. Force F, the inertial force F is replaced by the static fulcrum reaction force in the static bending stress relationship at the suspension point considering the stiffness of the wire, and the dynamic bending stress at the suspension point when the wire vibrates in the breeze is obtained. Specifically, it includes the following processes:

S4.1. Calculate the inertial force F when the vibration of the wire is stable within half-wavelength according to the following formula:

Theoretically, when the breeze vibration is stable, f in the formula should be the natural frequency considering the stiffness of the wire, and the present invention considers the transmission wire to be a tensioned beam with small stiffness, and the actual span can reach hundreds of meters, ignoring its own bending stiffness. The inertial force F error for wire vibration is generally not more than 5%, so the calculation of the inertial force is relatively safe;

In the formula, m represents the mass of the wire per unit length, λ represents the wavelength of the vibration of the wire in the gear, the unit is m, and the vibration is stable by the following formula:

In the formula, T ₀ represents the horizontal tension of the wire;

S4.2. Calculate the static bending stress σ at the suspension point considering the stiffness of the wire according to the following formula:

为静态支点反力；In the formula, E represents the elastic coefficient of the wire, refer to the parameters of the wire, for example, the elastic coefficient of the LGJ-800/100 wire is 67000N/mm ² ; J represents the moment of inertia of the wire section, and for a single-strand wire with a diameter of d, J=πd ⁴ /64; C represents the distance from the point of maximum bending stress on the conductor section to the bending neutral layer, where the radius r of the strand refers to the conductor parameters; p ₀ represents the concentrated load applied in the center of the test file, the unit is N ; l represents the gear distance, h represents the height difference of the suspension point,

is the static fulcrum reaction force;

S4.3. Substitute the inertial force F of the wire vibration for the static fulcrum reaction force in the static bending stress relationship at the suspension point considering the wire stiffness, and obtain the dynamic bending stress σ _c at the suspension point when the wire vibrates in the breeze:

The unit of dynamic bending stress σ _c at the suspension point when the wire vibrates in breeze is N/mm ² . According to the relationship between dynamic bending stress and dynamic bending strain, the dynamic bending strain ε _c at the clamp when the wire vibrates in breeze is obtained:

The unit of dynamic bending strain ε _c at the clip is μ _ε when the wire vibrates in breeze.

The above is only a preferred embodiment of the patent of the present invention, but the protection scope of the patent of the present invention is not limited to this. The technical solution and the invention patent concept of the invention are equivalently replaced or changed, all belong to the protection scope of the invention patent.

Claims (4)

1. a large-span power transmission wire suspension point-motion bending strain measurement method, is characterized in that, described method comprises the following steps: S1. Monitor the breeze vibration state of the wire, use the tension sensor to continuously measure the horizontal tension of the wire, and record the change of the horizontal tension of the wire. Specifically, the tension sensor is arranged at the outlet of the wire clamp, and the tension sensor is used to continuously measure the change of the horizontal tension of the wire. S2. Monitor the environmental conditions of the overhead transmission line, and use an anemometer to continuously measure the wind speed when the wire is running; specifically, install the anemometer at the clip of the hanging wire, and use the anemometer to continuously measure the wind speed of the environment where the wire is located. ; S3. According to the wind speed measured in step S2, use the energy balance method to calculate the characteristic parameters of the wire breeze vibration, that is, when the breeze vibration is stable, the power of the wind input wire is equal to the self-damping power of the wire, and the relationship between the wind speed and the wire amplitude and frequency is used. Obtain the characteristic parameters of the wire breeze vibration, that is, the amplitude and frequency of the wire breeze vibration; S4. Estimate the dynamic bending strain at the suspension point of the wire according to step S1 and step S3, that is, use the amplitude A ₀ and frequency f of the obtained wire breeze vibration to substitute the inertial force of the known wire vibration to obtain the inertia when the wire vibration is stable. Force F, the inertial force F is replaced by the static fulcrum reaction force in the static bending stress relationship at the suspension point considering the stiffness of the wire, and the dynamic bending stress at the suspension point when the wire vibrates in the breeze is obtained. 2 . The method for measuring long-span power transmission wire suspension point-bending strain according to claim 1 , wherein the tension sensor is a fiber grating strain sensor. 3 . 3. a kind of large-span transmission wire suspension point-motion bending strain measurement method according to claim 1, is characterized in that, the concrete process of step S3 is: First, calculate the power P _W of the wind input wire with the following formula:

In the formula,

Represents the dynamic lift coefficient, which is related to the wind speed; ρ represents the air density, the unit is kg/m ³ ; V represents the wind speed, the unit is m/s; D represents the outer diameter of the wire, the unit is m; f represents the frequency of the wind vibration of the wire, the unit is Hz; A ₀ represents the amplitude of the breeze vibration of the wire, the unit is m; where the dynamic lift coefficient

The solution formula is as follows:

In the formula, s represents the Sterloha number, which is related to the Reynolds number of the cylinder, and is 0.185 to 0.2 in the practical range, and 0.2 is used here; Then, calculate the self-damping power P _c of the wire, the formula is as follows:

In the formula, y ₀ represents the maximum double amplitude of the wire, and the three coefficients K, β, and α vary with the wire specifications, and can be obtained through the wire self-damping test; Finally, calculate the amplitude A ₀ of the wire breeze vibration: when other parameters are known, take the frequency f of the wire breeze vibration as the parameter coordinate, and use the maximum double amplitude y ₀ of the wire as the independent variable to draw the wind input power P of the wire The relationship between _W and the self-damping power P _c of the wire, the amplitude y ₀ corresponding to the intersection of the P _W and P _c curves of the same frequency is the stable amplitude of the power balance point, that is, the amplitude A ₀ of the wire breeze vibration; the wire breeze vibration When stable, the vibration frequency f can be expressed as a single function of the wind speed V:

In the formula, s represents the Sterloha number, which is related to the Reynolds number of the cylinder. 4. a kind of large-span transmission wire suspension point-motion bending strain measurement method according to claim 3, is characterized in that, described step S4 specifically comprises following process: S4.1. Calculate the inertial force F when the vibration of the wire is stable within half-wavelength according to the following formula:

In the formula, dx is any micro-segment wire, x is the length direction of the wire, m is the mass of the wire per unit length, λ is the wavelength of the wire vibration in the gear, the unit is m, and the vibration is stable by the following formula:

In the formula, T ₀ represents the horizontal tension of the wire; s represents the Sterloha number; S4.2. Calculate the static bending stress σ at the suspension point considering the stiffness of the wire according to the following formula:

In the formula, E represents the elastic coefficient of the wire; J represents the moment of inertia of the wire section, and for a single-strand wire with an outer diameter of D, J=πD ⁴ /64; C represents the maximum bending stress point on the wire section to the bending neutrality The distance between layers, here refers to the radius r of the strands; p ₀ represents the concentrated load applied in the center of the test gear, the unit is N; l represents the gear distance, h represents the height difference of the suspension point,

is the static fulcrum reaction force; S4.3. Substitute the inertial force F of the wire vibration for the static fulcrum reaction force in the static bending stress relationship at the suspension point considering the wire stiffness, and obtain the dynamic bending stress σ _c at the suspension point when the wire vibrates in the breeze:

The unit of dynamic bending stress σ _c at the suspension point when the wire vibrates in breeze is N/mm ² . According to the relationship between dynamic bending stress and dynamic bending strain, the dynamic bending strain ε _c at the clamp when the wire vibrates in breeze is obtained:

The unit of dynamic bending strain ε _c at the clip is μ _ε when the wire vibrates in breeze.

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