Sag measurement method for ultrahigh-voltage power transmission line robot

Abstract

The invention provides a sag measurement method for an ultrahigh-voltage power transmission line robot, and the method comprises the steps: obtaining the operation state data of the robot on a line through the cooperation of a magnetic rotor and a tilt angle sensor, obtaining the operation state data of the robot on the line through the tilt angle sensor, calculating the sag of the line through the fitting of a parabola, and solving a problem that the sag measurement is affected by the dead weight of the robot. And providing a compensation scheme.

Description

Technical Field

[0001] This invention relates to the use of robots for sag measurement in ultra-high voltage transmission lines. The goal is to enable the rapid and accurate measurement of sag by a line robot during ultra-high voltage line construction when there is no line of sight. This solves the problem that sag cannot be obtained on-site using ground observation instruments under complex construction conditions, which affects the construction progress, thereby significantly improving construction efficiency and accuracy. Background Technology

[0002] Ultra-high voltage (UHV) overhead transmission lines bear the primary responsibility for transmitting electrical energy and are a crucial component of the power system. UHV transmission lines are composed of split-type reinforced aluminum stranded wires. When erected on towers, the transmission lines are subjected to tension and gravity, exhibiting a parabolic shape. Sag refers to the vertical distance from the lowest point of the overhead line to the line connecting the two suspension points. Excessive sag increases the risk of wind-induced galloping. Galloping not only leads to fatigue damage to the conductors but can also cause phase-to-phase short circuits or conductor entanglement, severely affecting the stability and safety of power transmission and its current-carrying capacity. Insufficient sag, on the other hand, means excessive tension between the transmission conductors, increasing the risk of conductor breakage, support damage, or insulator string damage. Therefore, sag is used as a standard for line laying and a project acceptance indicator during transmission line construction, and it must meet design requirements.

[0003] Currently, four common methods for measuring sag in engineering projects are the equal-length method, the unequal-length method, the angle method, and the level-of-sight method. All four methods require ground surveyors to use a theodolite to observe and obtain the location information of specific points along the line before calculating the sag data. However, the geographical environment of the construction area is complex and variable, and is also affected by weather factors. When visibility conditions are not met, observation is impossible, severely impacting the progress of power construction. Furthermore, as power construction continues to extend to remote areas and voltage levels continue to increase, the spanning distances of towers are constantly increasing, raising the construction difficulty. Therefore, a convenient and reliable sag monitoring method is urgently needed.

[0004] To address the challenge of sag measurement under long-distance, non-line-of-sight conditions, aerial measurement solutions have become the mainstream approach. Helicopters equipped with lidar offer advantages such as large measurement range and long endurance; however, the measurement cost is prohibitively high. To effectively reduce costs, drones equipped with lidar have garnered significant attention for measurement, using 3D lidar combined with image processing methods to obtain sag values. However, such methods require acquiring video, point cloud data, or images of the transmission line, followed by complex calculations that struggle to meet real-time engineering requirements. Furthermore, they suffer from poor endurance, limited detection range, and the need for trained operators. In contrast, line robots are reliable and convenient. Equipped with various sensors and installed on overhead lines, they can effectively monitor the real-time status of the line. Therefore, this invention proposes a sag measurement method for robots used in ultra-high voltage transmission lines during overhead line construction. This method features high real-time measurement accuracy, meeting practical engineering needs.

[0005] The relevant technologies applied in this invention are as follows: (1) Kalman Filter: Kalman filtering is a recursive algorithm specifically used for state estimation of linear dynamic systems. It uses a state-space model of noise and signal, and uses the estimated value of the previous moment and the observed value of the current moment to update the estimate of the state variables and obtain the estimated value of the current moment. Its design goal is to provide an optimal estimate when the system state cannot be directly measured and the measured value is affected by noise.

[0006] (2) Least squares method: The least squares method is a mathematical method used for data fitting and parameter estimation. It finds the best parameter estimate by minimizing the sum of squares of the errors between the predicted value and the actual observed value, so that the predicted value of the model is as close as possible to the actual observed value. Summary of the Invention

[0007] This invention proposes a method for measuring the sag of robots used in ultra-high voltage transmission lines. By combining a magnetic rotor with a tilt sensor to acquire the robot's operating status data on the line, and using parabolic fitting, the line sag is calculated. A compensation scheme is provided to address the issue of the robot's own weight affecting the sag measurement. The specific method is as follows: Step 1: Data Acquisition: The robot runs on the track. The running mechanism includes a drive wheel and a pressure wheel. During operation, the pressure wheel rotates passively, with a magnetic rotor and a Hall sensor embedded in its side. The magnetic rotor and the Hall sensor work together to provide the number of rotations of the pressure wheel. (revolutions / second), given the circumference of the pressure wheel. (mm), data sampling time interval Taking 0.2 seconds, the calculation yields the pressure roller at the [number]th [time]. Within each sampling period, the distance traveled on the line is ; (1).

[0008] Step 2: Calculate the sag: Since the sampling time is 0.2 seconds, the robot's displacement in space is approximated as a straight line with a length equal to... The angle between it and the horizontal direction is The robot's horizontal displacement is obtained. and vertical displacement The values ​​are respectively (2).

[0009] in Obtained by mounting a tilt sensor on the robot, due to the measurement process Sudden changes can occur due to factors such as vibration or acceleration variations, but the actual gradient change is smooth. Therefore, it is necessary to smooth the angle data within the sampling period. This invention uses Kalman filtering for this purpose. The included angle within each sampling period is Then, the included angle data is processed using a median filter with a step size of 2, and the result is obtained according to formula (2). The robot's horizontal displacement within each sampling period and vertical displacement The values ​​are respectively (3).

[0010] In the engineering project, the precise location information of the suspension points of the overhead line on the two towers is known. Assume the robot starts from the suspension point... To the suspension point Directional movement; the linear function relationship determined by points A and B is: (4).

[0011] The first data collected by the robot on the overhead line The coordinates of each point are represented as follows: (5).

[0012] In power construction, when the ratio of the height difference between suspension points to the span is no greater than 10%, a parabolic fitting can be used for conductor mechanical calculations. Since ultra-high voltage overhead transmission lines typically meet these requirements, the coordinate data of all points collected by the robot on the overhead line are fitted into an oblique parabola using the least squares method. Its equation is: (6) The least squares method is used to obtain the coefficients of the parabola equation. a 0, a 1 and a 2 This is obtained by minimizing the sum of squared errors.

[0013] Calculate sag The relation is (7) At this time, the corresponding sag of The value is denoted as the x-coordinate. .

[0014] Step 3: Sag Compensation: Due to the robot's own gravity, the stress on the overhead ground wire will be affected, increasing the sag of the overhead transmission line. Therefore, sag compensation is needed to improve the accuracy of sag measurement. Based on the relationship between shear force and bending moment of a simply supported beam, the relationship between the sag and stress of the overhead transmission line is constructed, and the formula is as follows: (8).

[0015] In the formula It is a sag; The elevation difference angle is the angle between the straight lines defined by suspension points A and B in the horizontal direction. The horizontal distance between suspension points A and B; The horizontal stress experienced by overhead power transmission lines; The specific load caused by the weight of the overhead line itself, the self-weight specific load is in the same direction as gravity, and its calculation formula is: (9) In the formula, The unit conductor mass (kg / m); This represents the cross-sectional area of ​​the conductor (square millimeters).

[0016] When the force causing sag is decomposed into the combined action of distributed load (line self-weight) and concentrated load (weight of objects suspended on the line), then formula (8) is rewritten as follows: (10) in The horizontal stress on an overhead transmission line when only distributed loads exist; For the first in the line The weight per unit section of a concentrated load.

[0017] When using formula (10) The effect of robot gravity on sag is represented by the sag increment caused by robot gravity. It can be represented as (11) in, The robot's weight is divided by the cross-sectional area of ​​the wire.

[0018] The sag obtained in step 2 according to formula (7) The value is substituted into formula (8) to obtain the horizontal stress. The value, then Substituting the value into formula (11), the sag increment is obtained. .

[0019] The corrected sag is obtained from formulas (7) and (11). The calculation formula is: (12) This is the desired sag. Attached Figure Description

[0020] Figure 1 flow chart. Detailed Implementation

[0021] In order to verify the accuracy of sag measurement, an experimental platform was built to conduct sag measurement experiments. The cable used was LGJ-400 / 50. The experimental equipment used included a self-developed ultra-high voltage transmission line robot and a DT-02CL theodolite.

[0022] Experimental procedure: Using the theodolite measurement as the true value, the sag size measured by the method described in this invention is compared with the true value to verify the accuracy of this invention.

[0023] Place the robot on the line to be tested, press the start button, and the clamping wheel clamps the power line. The robot's active wheel runs stably at 3.5 revolutions per second. The magnetic rotor, in conjunction with the Hall sensor, provides a clamping wheel rotation rate of 8.3 revolutions per second. The circumference of the clamping wheel is known to be 125.6 mm. The data sampling time interval is... T Taking 0.2 (seconds), the distance traveled by the pressure wheel every 0.2s is calculated to be 208.496 (mm) according to formula (1).

[0024] The tilt sensor is installed inside the robot control box to measure the included angle. The output angle after Kalman filtering is According to formula (3), the robot's displacement in the horizontal direction and vertical displacement The value of .

[0025] Given the coordinates of suspension points A and B of the overhead line, the linear function relationship can be obtained according to formula (4). The angle between the straight lines defined by suspension points A and B in the horizontal direction. Horizontal distance between suspension points A and B .

[0026] A two-dimensional coordinate system is established with the suspension point A of the line under test as the zero point. The coordinates of points on the overhead line collected by the robot every 0.2 seconds are calculated according to formula (5). The collected coordinates are then fitted into a parabola as shown in formula (6) using the least squares method. The parabola was calculated. a 0 , a 1 and a 2。

[0027] Calculate the sag according to formula (7) At the same time, the corresponding .

[0028] Given the overhead line model, the result can be obtained by looking up a table. .Will Substituting the specific value into formula (8), the horizontal stress is calculated. The value of .

[0029] Given the concentrated load on the robot, the weight per unit cross section Q The sag increment caused by the robot's gravity is 0.1146 (N / mm²), which is obtained according to formula (11). .

[0030] The corrected sag is obtained according to formula (12). .

[0031] The experiment involved setting the height of four suspension points B to change the sag, and was divided into four groups. In each group, the robot ran three times to measure the sag value. By comparing the results, the average measurement error was found to be 1.3%, with a maximum relative error of 2.44%, and the error was within 2.5%. Therefore, this invention achieves accurate calculation of line sag within the allowable range of engineering errors.

[0032] This invention utilizes an ultra-high voltage transmission line robot to measure sag based on an online autonomous positioning algorithm. It proposes a method based on the tension of the transmission line to calculate the error caused by the robot's gravity. This method effectively corrects the error caused by gravity, achieves high-precision measurement of sag, and effectively reduces the workload of measurement. It is low-cost, portable, and easy to operate, allowing a single construction worker to complete the deployment and measurement.

Claims

1. A sag measurement method for an ultra-high voltage transmission line robot, characterized in that: The magnetic rotor on the robot cooperates with the inclination sensor, and the robot's operating status data on the line is obtained in combination with the inclination sensor. The line sag is calculated using parabola fitting, and a compensation solution is provided for the problem that the robot's own weight affects the sag measurement. The specific method is as follows: Step 1 Obtain data: The robot runs on the line. The operating mechanism includes a driving wheel and a clamping wheel. The clamping wheel rotates passively during operation. A magnetic rotor and a Hall sensor are embedded in its side. The magnetic rotor and the Hall sensor cooperate to provide the number of revolutions of the clamping wheel. (turns / second), given the circumference of the pressure wheel (mm), data sampling time interval Take 0.2 (seconds) and calculate the time at which the clamping wheel In a sampling period, the distance traveled on the line is ; （1) Step 2 Calculate the sag: Since the sampling time is 0.2 seconds, the displacement of the robot in space is approximated as a straight line with a length equal to , and the angle with the horizontal direction is , get the horizontal displacement of the robot and vertical displacement The values ​​are （2） in The tilt sensor is mounted on the robot. The slope of the line is affected by vibration or acceleration changes, but the actual line slope changes are smooth. Therefore, it is necessary to smooth the angle data within the sampling period. The present invention adopts Kalman filtering. The angle within a sampling period is , and then use the median filter with a step size of 2 to process the angle data, and get the first The robot's horizontal displacement in a sampling period is and vertical displacement The values ​​are （3） In the project, the exact location information of the suspension points of the overhead lines on the two towers is known. The robot is set to Towards the hanging point Direction movement; the linear function relationship determined by points A and B is （4） The robot collected the The coordinates of the points are expressed as （5） In power construction, when the ratio of the height difference between the suspension points to the span is not greater than 10%, a parabola fitting can be used to perform conductor mechanics calculations. Since ultra-high voltage overhead transmission lines usually meet the requirements, the coordinate data of all points collected by the robot on the overhead line are fitted into an oblique parabola using the least squares method, and its equation is: （6） Among them, the least squares method obtains the parabola equation coefficients ɑ 0 , ɑ 1 and ɑ 2 , obtained by minimizing the sum of squared errors; Calculate sag The relationship is （7） At this time, the corresponding sag of The value is recorded as the horizontal axis ; Step 3: Sag compensation: Due to the gravity of the robot itself, the stress of the overhead ground wire will be affected, increasing the sag of the overhead transmission line. Therefore, sag compensation is required to improve the accuracy of sag measurement. According to the relationship between the shear force and bending moment of the simply supported beam, the relationship between the sag and stress of the overhead transmission line is constructed, and the relationship is: （8） In the formula is the sag; is the height difference angle, that is, the angle between the straight line determined by the suspension points A and B in the horizontal direction; is the horizontal distance between hanging points A and B; is the horizontal stress on the overhead transmission line; It is the specific load caused by the weight of the overhead line itself. The direction of the self-weight specific load is the same as that of gravity. Its calculation formula is: （9） In the formula, is the unit conductor mass (kg / m); is the cross-sectional area of ​​the conductor (square millimeters); When the force that produces sag is solved as the combined effect of distributed load (line weight) and concentrated load (weight of suspended objects on the line), formula (8) is rewritten as: （10） in is the horizontal stress on the overhead transmission line when only distributed load exists; For the line The unit cross-sectional gravity of a concentrated load; When using formula (10) Indicates the effect of robot gravity on sag, then the sag increment caused by robot gravity It can be expressed as （11） in, is the robot's gravity divided by the wire's cross-sectional area; The sag obtained in step 2 according to formula (7) Substituting the value into formula (8) to obtain the horizontal stress , and then Substitute the value into formula (11) to obtain the sag increment ; According to formula (7) and formula (11), the corrected sag is obtained: The calculation formula is （12） This is the desired sag.

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