A method and system for detecting ice thickness on overhead power lines

Abstract

This invention relates to the field of intelligent sensing system technology, specifically to a method and system for detecting the icing thickness of overhead power lines. The invention solves for the central tension vector based on the tension vector of the conductor under test within the monitoring period, eliminating wind-induced sensor oscillations and accurately assessing the stable force field of the conductor. Furthermore, utilizing the unique physical length of the conductor, the length is calculated from both the catenary angle and material thermodynamics perspectives. By comparing the deviations in the conductor length, the icing weight is inverted through iterative approximation, thereby accurately determining the icing thickness. This effectively solves the measurement errors caused by wind-induced galloping and sensor attitude deviations in traditional methods, significantly improving the accuracy and robustness of icing monitoring under severe weather conditions.

Description

Technical Field

[0001] This invention relates to the field of intelligent sensing system technology, specifically to a method and system for detecting the icing thickness of overhead power lines. Background Technology

[0002] Overhead power lines are susceptible to icing due to microclimates such as freezing rain and wet snow in winter. If the icing is severe and de-icing measures are not taken in time, severe icing may cause conductors to gallop, break, or even towers to collapse, directly threatening the safe operation of the power grid. Therefore, it is essential to accurately detect the thickness of icing on overhead power lines.

[0003] Currently, online monitoring systems based on intelligent sensors are mainly used to detect ice thickness. These systems collect the combined tension and tilt angle of the conductors using tension sensors installed at the pole suspension points and tilt sensors on the insulator strings, and then use a mechanical equilibrium model to calculate the weight of the ice. However, conductor tension is greatly affected by thermal expansion and contraction and strong winds: low temperatures can cause the conductors to contract and tighten, easily leading to false alarms; strong winds not only change the suspension geometry of the conductors but also cause fluctuations in sensor readings, making it impossible to accurately determine the true stress on the conductors; thus affecting the accuracy of ice thickness detection for overhead power lines. Summary of the Invention

[0004] To address the low accuracy of existing methods for detecting the icing thickness of overhead power lines, this invention aims to provide a method and system for detecting the icing thickness of overhead power lines. The specific technical solution adopted is as follows: A method for detecting the icing thickness of overhead power lines, the method comprising: The tensile force of the conductor under test, the tilt angle of the insulator string, and the conductor temperature are obtained during the monitoring period; based on the tilt angle, the tensile force at each moment is decomposed into a tensile force vector in three-dimensional space to construct a time-series tensile force vector set. Obtain the central tension vector of the tension vector set, decompose the central tension vector to obtain the stable horizontal tension and stable wind deflection angle; based on the assumed ice weight and conductor self-weight per unit length of conductor, and combined with the stable wind deflection angle, obtain the unit composite line load under each assumed ice weight. Based on the stable horizontal tension and the unit composite line load, as well as the span of the conductor under test, the catenary arc length of the conductor under test under each assumed ice weight is obtained; based on the central tension vector, the conductor temperature, and the zero-stress reference length of the conductor under test, the theoretical material length of the conductor under test is calculated. The assumed ice weight is iteratively adjusted until the difference between the catenary arc length and the theoretical length of the material is less than a preset threshold. Based on the assumed ice weight at convergence, the ice thickness per unit length of the conductor under test is calculated.

[0005] Furthermore, a three-dimensional spatial coordinate system is constructed with the hanging point of the conductor to be measured as the origin, the horizontal direction of the conductor to be measured as the x-axis, the direction of gravity as the z-axis, and the axis perpendicular to the xoz plane as the y-axis. The tilt angle includes a horizontal tilt angle and a lateral tilt angle; wherein, the horizontal tilt angle is the deflection angle of the insulator string in the xoz plane relative to the z-axis, and the lateral tilt angle is the deflection angle of the insulator string in the yoz plane relative to the z-axis.

[0006] Furthermore, the method for obtaining the set of tension vectors includes: At each moment, based on the horizontal tilt angle decomposition, the horizontal tension component on the x-axis and the intermediate projection component located in the xoz plane are obtained; based on the lateral tilt angle decomposition, the lateral tension component on the y-axis and the vertical tension component on the z-axis of the intermediate projection component are obtained; the horizontal tension component, the lateral tension component, and the vertical tension component are used as instantaneous tension vectors; the instantaneous tension vectors within the monitoring period are sorted in time sequence, and the sorting result is used as a set of tension vectors.

[0007] Furthermore, the method for obtaining the central tension vector includes: The central tension vector of the tension vector set is solved using the minimum volume closed ellipsoid algorithm.

[0008] Furthermore, the method for obtaining the stable horizontal tension and stable wind deflection angle includes: The modulus of the horizontal component of the central tension vector on the x-axis is taken as the stable horizontal tension; the arctangent of the lateral component of the central tension vector on the y-axis and the vertical component on the z-axis is taken as the stable wind deflection angle.

[0009] Furthermore, the method for obtaining the unit synthetic line load includes: Under each assumed ice weight, the sum of the assumed ice weight per unit length of conductor and the conductor's own weight is taken as the unit composite gravity; combined with the stable wind deflection angle, the unit lateral wind load is solved based on the tangent relationship between the lateral wind load and the unit composite gravity; the combined result of the unit composite gravity and the unit lateral wind load is taken as the unit composite line load.

[0010] Furthermore, the method for obtaining the catenary arc length includes: Under each assumed ice weight, the ratio of the stable horizontal tension to the unit synthetic line load is used as the catenary coefficient. The catenary coefficient and the line span are substituted into the preset catenary equation to obtain the catenary arc length.

[0011] Furthermore, the method for obtaining the theoretical length of the material includes: Based on the average conductor temperature during the monitoring period and the zero-stress reference length of the conductor under test, the theoretical expansion length of the conductor under test is calculated using the linear thermal expansion formula; based on the modulus of the central tension vector and the zero-stress reference length of the conductor under test, the theoretical tensile length of the conductor under test is calculated using the mechanical tensile deformation formula; the sum of the zero-stress reference length, the theoretical expansion length, and the theoretical tensile length is taken as the theoretical length of the material.

[0012] Furthermore, the method for obtaining the zero-stress reference length includes: Calculate the ice-free catenary arc length of the conductor under test in the most recent ice-free monitoring cycle; take the zero-stress reference length as the unknown independent variable and the ice-free catenary arc length as the known dependent variable, and construct the length equation based on the average conductor temperature and the average tension of the conductor under test in the most recent ice-free monitoring cycle, using the linear thermal expansion formula and the mechanical tensile deformation formula, and solve for the zero-stress reference length.

[0013] An overhead power line icing thickness detection system is provided. The system includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the overhead power line icing thickness detection method.

[0014] The present invention has the following beneficial effects: This invention first obtains the tension of the conductor under test, the tilt angle of the insulator string, and the conductor temperature during the monitoring period. Then, based on the tilt angle, the tension at each moment is decomposed into a tension vector in three-dimensional space, constructing a time-series set of tension vectors. This provides a data foundation for subsequently capturing the spatial envelope characteristics of gust disturbances and solving for the central tension vector. The central tension vector, characterizing the steady-state stress characteristics of the conductor under test under the combined action of average wind load and gravity, is decomposed to determine the stable horizontal tension and stable wind deflection angle of the conductor under test. Then, based on the assumed ice weight per unit length of conductor and the conductor's own weight, combined with the stable wind deflection angle, the temperature of the conductor under test in the wind deflection plane is obtained. The unit composite line load under each assumed ice weight is determined, and then the catenary arc length of the conductor under test is obtained based on the stable horizontal tension, the unit composite line load, and the span of the conductor under test. The theoretical material length of the conductor under test is calculated based on the central tension vector, conductor temperature, and zero-stress reference length of the conductor under test. Utilizing the uniqueness of the physical length of the conductor under test, the assumed ice weight is iteratively adjusted until the difference between the catenary arc length and the theoretical material length is less than a preset threshold, in order to invert the icing weight per unit conductor. Finally, the icing thickness per unit length of the conductor under test is calculated based on the assumed ice weight at convergence. This invention solves for the central tension vector based on the tension vector of the conductor under test during the monitoring period, eliminating wind-induced sensor oscillations and accurately assessing the stable force field of the conductor under test. Furthermore, it utilizes the unique physical length of the conductor under test to calculate the length from both the catenary angle and the thermodynamics of the material. By comparing the deviation of the conductor length, it achieves the inversion of icing weight through iterative approximation, thereby accurately solving the icing thickness. This effectively solves the measurement errors caused by wind-induced galloping and sensor attitude deviations in traditional methods, and significantly improves the accuracy and robustness of icing monitoring under severe weather conditions. Attached Figure Description

[0015] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a flowchart of a method for detecting the icing thickness of overhead power lines, provided as an embodiment of the present invention. Detailed Implementation

[0017] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a method and system for detecting ice thickness on overhead power lines according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0019] The following description, in conjunction with the accompanying drawings, details the specific scheme of the method and system for detecting the icing thickness of overhead power lines provided by the present invention.

[0020] Please see Figure 1 The diagram illustrates a flowchart of a method for detecting the icing thickness of overhead power lines according to an embodiment of the present invention, specifically including: Step S1: Obtain the tension of the conductor under test, the tilt angle of the insulator string, and the conductor temperature within the monitoring period; based on the tilt angle, decompose the tension at each moment into a tension vector in three-dimensional space, and construct a time-series set of tension vectors.

[0021] In one embodiment of the present invention, a section of conductor to be tested (such as the power line between two towers) is first determined in the overhead power line, and the ice thickness is analyzed using the conductor to be tested as an example.

[0022] At the pole suspension point of the conductor to be tested, a tension sensor (such as a resistance strain gauge load cell) is installed in series to measure the tension (horizontal or along the line) of the conductor to be tested on the suspension point. A biaxial tilt sensor (such as a MEMS-based accelerometer) is rigidly fixed on the extension rod or fittings of the insulator string to measure the tilt angle, i.e., the angle of deflection of the insulator string axis relative to the vertical line of gravity. A temperature sensor is installed on the tower or near the conductor to be tested. The sensor should be placed in a Stevenson screen or have a radiation shield to obtain an ambient temperature that can represent the temperature around the conductor and approximate the conductor temperature.

[0023] To facilitate understanding, we first construct the three-dimensional space in which the conductor to be tested is located; in the implementation scenario targeted by this embodiment, the hanging points are at the same height.

[0024] Specifically, a three-dimensional spatial coordinate system is constructed with any hanging point of the conductor to be tested as the origin, the horizontal direction of the conductor to be tested as the x-axis, the direction of gravity as the z-axis, and the axis perpendicular to the xoz plane as the y-axis. The construction of the three-dimensional spatial coordinate system is a well-known technology and will not be elaborated further.

[0025] It should be noted that the horizontal direction specifically refers to the direction of the conductor under ideal straightening conditions, and also refers to the direction of the horizontal connection between two towers. The x-axis extends horizontally under ideal conditions; the direction of gravity refers to the vertical direction; and the z-axis is parallel to the tower under ideal conditions. Then, the third axis, namely the y-axis, can be determined. The y-axis is perpendicular to both the x-axis and the z-axis, and is usually the direction of the lateral galloping or swaying of the conductor under test.

[0026] In a preferred embodiment of the present invention, the tilt angle includes a horizontal tilt angle and a lateral tilt angle; the horizontal tilt angle is the deflection angle of the insulator string in the xoz plane relative to the z-axis, and the lateral tilt angle is the deflection angle of the insulator string in the yoz plane relative to the z-axis.

[0027] The horizontal tilt angle characterizes the deflection of the insulator string towards the x-axis under combined loads (including conductor tension and gravity, wind force, ice weight, etc.), preparing for the subsequent decomposition and evaluation of the horizontal load components of the x-axis; the lateral tilt angle characterizes the deviation of the insulator string from the y-axis under combined loads, preparing for the subsequent decomposition and evaluation of the lateral load components of the y-axis.

[0028] Then, the time window for a single icing analysis, i.e. the monitoring period, is determined. The length of the monitoring period needs to cover several complete swing cycles of the conductor under the action of gusts in order to collect enough data to analyze the wind-driven swaying information of the conductor under test. The recommended length of the monitoring period is 5-10 minutes. In this embodiment, it is set to 10 minutes. The implementer can also adjust it according to the actual situation.

[0029] During the monitoring period, the tension sensor, dual-axis tilt sensor and conductor temperature sensor are triggered simultaneously to collect tension, tilt angle and conductor temperature at the same sampling frequency (1Hz~10Hz recommended, 1Hz in this example); There is a possibility that some data may be missing or abnormal at certain sampling times. Therefore, it is necessary to further clean the sampled data. The known technical means are briefly described here: interpolation is performed on the missing data based on the timestamp to remove sudden noise caused by electromagnetic interference (such as the value instantly returning to zero or exceeding the range).

[0030] After collecting the tension of the conductor under test, the insulator string tilt angle, and the conductor temperature at each (sampling) moment during the monitoring period, the tension at each moment can be further decomposed based on the tilt angle. The specific manifestation of the tension is affected by complex loads (including conductor tension and gravity, wind force, ice weight, etc.). Decomposing the tension to determine the tension vector in three-dimensional space can help decompose the influence of conductor, wind force, and ice weight, and further construct a temporal set of tension vectors.

[0031] Considering the main characteristics of the tension along the line, the horizontal projection of the tension on the x-axis can be decomposed by the horizontal inclination angle to determine the horizontal tension component. The horizontal tension component is mainly determined by the tension of the conductor and is less affected by lateral wind. At the same time, the component of the tension at non-line angles can be determined, that is, the intermediate projection component located in the xoz plane. The intermediate projection component represents the contribution of other factors such as conductor weight, wind force and icing to the tension, in addition to conductor tension. The intermediate projection component is further decomposed on the y-axis and z-axis by using the lateral tilt angle to determine the lateral tension component and the vertical tension component. The lateral tension component is greatly affected by wind load and mainly represents the lateral load of wind on the conductor. The vertical tension component is greatly affected by the weight of the conductor and the weight of ice and represents the gravitational load of the conductor and ice. Based on this, in a preferred embodiment of the present invention, the method for obtaining the set of tension vectors includes: At each moment, the horizontal tensile force component on the x-axis and the intermediate projection component in the xoz plane are obtained based on the horizontal tilt angle decomposition; the lateral tensile force component on the y-axis and the vertical tensile force component on the z-axis are obtained based on the lateral tilt angle decomposition; the horizontal tensile force component, the lateral tensile force component, and the vertical tensile force component are used as instantaneous tensile force vectors; the instantaneous tensile force vectors within the monitoring period are sorted in time sequence, and the sorting results are used as a set of tensile force vectors.

[0032] As an example, taking any (sampling) moment within the monitoring period as an example, the instantaneous tension vector The expression is: ;in, For tension; It is the horizontal tilt angle; It is the lateral tilt angle; This is the horizontal tensile force component; This is the lateral tensile force component; This is the vertical tensile force component; This is the intermediate projection component.

[0033] Further construct the set of tension vectors The set of tension vectors contains the dynamic swing range and distribution characteristics of the conductor under test under wind load, providing a data basis for subsequent capture of the spatial envelope characteristics of gust disturbances and solving the central tension vector.

[0034] Step S2: Obtain the central tension vector of the tension vector set, decompose the central tension vector to obtain the stable horizontal tension and stable wind deflection angle; based on the assumed ice weight per unit length of conductor and the conductor's own weight, combined with the stable wind deflection angle, obtain the unit composite line load under each assumed ice weight.

[0035] Considering that the set of tension vectors represents a three-dimensional force space, which can help evaluate the spatial envelope characteristics of the conductor under test under wind load, by determining the steady-state force equilibrium point in the three-dimensional force space, it can help extract the steady-state force characteristics of the conductor under the combined action of average wind load and gravity. Therefore, in this embodiment of the invention, the central tension vector of the set of tension vectors is obtained; the central tension vector is the steady-state force vector in the three-dimensional force space.

[0036] In natural wind fields, conductors are affected not only by average wind but also by random disturbances from gusts. These disturbances cause the readings of tension and tilt sensors to fluctuate wildly, forming discrete three-dimensional force "point cloud" data, which cannot directly reflect the true stress state of the conductor. Furthermore, simple time-domain averaging is easily affected by extreme values ​​(such as instantaneous strong winds), making it difficult to assess the steady-state force vector. The dynamic response of the conductor under wind load is essentially a multi-degree-of-freedom nonlinear vibration system. On the x-axis, constrained by conductor tension, the oscillation along the line is limited, and the fluctuation range of the horizontal tension component is small, which can be regarded as the minor axis of the ellipsoid. On the y-axis, it is easily swayed by lateral wind, and the fluctuation range of the lateral tension component is large, which can be regarded as the major axis of the ellipsoid. On the z-axis, constrained by gravity, the fluctuation range of the vertical tension component is moderate, which can be regarded as the central axis of the ellipsoid. Furthermore, based on the anisotropy of the tension components, the distribution of the instantaneous tension vector statistically presents an ellipsoid shape with unequal lengths along the three axes. The Minimum Volume Enclosing Ellipsoid (MVEE) algorithm is used to find the geometric center. Essentially, it utilizes the law of large numbers and geometric symmetry: although a single gust is random, over a long period of time, the gust disturbance exhibits a certain symmetrical distribution (ellipsoidal distribution) around the steady-state center. MVEE can find this symmetric center better and is more robust than the arithmetic mean. Based on this, in a preferred embodiment of the present invention, the method for obtaining the central tension vector includes: The central tension vector of the tension vector set is solved using the minimum volume closed ellipsoid algorithm.

[0037] It should be noted that the method of solving for the central tension vector of the tension vector set based on the minimum volume closed ellipsoid algorithm is a well-known technique, which will be briefly described here: Optimization objective: Find a positive definite matrix Q and a central tension vector. This minimizes the volume of the ellipsoid G; to ensure the ellipsoid can encompass all instantaneous tension vectors, the following constraints are set: The solution is obtained using the Khachiyan coordinate descent method or the Frank-Wolfe iterative algorithm. The solution process is as follows: Initialization: Set the initial center vector 0 represents the arithmetic mean of the instantaneous tension vector, and the initial positive definite matrix Q0 is set as the identity matrix; Iterative optimization: In each iteration, find the instantaneous tension vector that is farthest from the current center vector, and adjust the shape and center position of the ellipsoid according to the farthest instantaneous tension vector so that its volume is reduced while still enclosing all instantaneous tension vectors; Convergence criterion: When the rate of change of the ellipsoid volume is less than a preset threshold (e.g., ... Stop iterating when ().

[0038] The final solution yields the central tension vector. Its component form is: .

[0039] The central tension vector represents the equivalent stable characteristic vector of the conductor under test after eliminating random disturbances from gusts, under the combined action of mean wind load and gravity; it is not the tension in a windless state, but rather the steady-state force characteristic that includes the mean wind effect.

[0040] After determining the central tension vector, the central tension vector is further decomposed to obtain the stable horizontal tension and stable wind deflection angle. The stable horizontal tension represents the constant horizontal tension maintained by the conductor across the span after eliminating tension fluctuations caused by gusts. The stable wind deflection angle represents the stable tilt posture maintained by the conductor under the combined action of gravity and average wind force after eliminating random disturbances caused by gusts, that is, the lateral deflection angle or galloping angle of the conductor, which provides a basis for subsequent analysis of wind loads.

[0041] Preferably, in one embodiment of the present invention, the method for obtaining stable horizontal tension and stable wind deflection angle includes: The modulus of the horizontal component of the central tension vector along the x-axis is taken as the stable horizontal tension; the arctangent of the lateral component of the central tension vector along the y-axis and the vertical component along the z-axis is taken as the stable wind deflection angle.

[0042] The stable horizontal tension is the horizontal component of the central tension vector along the x-axis. The modulus; the arctangent of the lateral component of the central tension vector on the y-axis and the vertical component on the z-axis is... The angle between the conductor and the vertical direction in the yoz plane represents the lateral deflection angle or galloping angle of the conductor. When the steady wind deflection angle is close to 0, it indicates that there is no lateral wind load. The larger the steady wind deflection angle, the greater the degree of lateral galloping of the conductor.

[0043] Once the stable wind deflection angle is determined, the equivalent unit resultant force (unit resultant load, referring to the combined effect of gravity and average wind force) of the unit self-weight of the conductor under test and the assumed (covered) ice weight can be further analyzed in the wind deflection plane by combining the self-weight of the conductor under test and the ice weight. The unit resultant line load under each assumed ice weight is obtained. The unit resultant line load characterizes the equivalent line load borne by the unit conductor under the premise of maintaining the current stable wind deflection angle, which prepares for the subsequent measurement of the catenary length of the conductor under test.

[0044] Preferably, in one embodiment of the present invention, considering that the unit conductor under test is subject not only to its own gravity but also to the gravity of ice covering the conductor surface, and that the two are in the same direction, the sum of which can characterize the unit resultant gravity in the z-axis gravity direction; and that the stable wind deflection angle of the unit conductor under test is mainly affected by the lateral wind load on the y-axis, and that the equivalent unit resultant force of the unit conductor under test is formed in the wind deflection plane under the combined action of the lateral wind load and the unit resultant gravity, the tangent relationship between the lateral wind load and the unit resultant gravity can first be analyzed by using the stable wind deflection angle to solve for the unit lateral wind load, and then the unit resultant line load can be determined by combining the unit resultant gravity; therefore, the method for obtaining the unit resultant line load includes: Under each assumed ice weight, the sum of the assumed ice weight per unit length of conductor and the conductor's own weight is taken as the unit composite gravity; combined with the stable wind deflection angle, the unit lateral wind load is solved based on the tangent relationship between the lateral wind load and the unit composite gravity; the combined result of the unit composite gravity and the unit lateral wind load is taken as the unit composite line load.

[0045] As an example, first, set the unit length to 1m, and define the unknown variable to be solved—the assumed ice weight w, in N / m; under each assumed ice weight, use the sum of the assumed ice weight per unit length of conductor and the conductor's own weight as the composite gravity W, in N / m; As a unit lateral wind load, among which To stabilize the wind deflection angle, the combined result of the unit composite gravity and the unit lateral wind load is further used as the unit composite line load. This is a well-known technical method and will not be elaborated further.

[0046] In another embodiment of the invention, the cosine relationship between unit composite gravity and unit composite line load can also be directly used to directly... As the unit composite line load; where, to prevent calculation overflow (e.g., in extreme strong winds with a downslope angle close to 90°), when At that time, a mandatory order .

[0047] Step S3: Based on the stable horizontal tension and unit composite line load, as well as the span of the conductor under test, obtain the catenary arc length of the conductor under test under each assumed ice weight; calculate the theoretical material length of the conductor under test based on the central tension vector, conductor temperature, and zero-stress reference length of the conductor under test.

[0048] To determine the weight of ice on a unit length of the conductor to be tested, i.e., the assumed ice weight, this embodiment of the invention utilizes the uniqueness of the physical length of the conductor to be tested, calculates the length of the conductor to be tested from both the catenary angle and the thermodynamics of the material, and compares the deviations of the length of the conductor to be tested to make the deviations converge, thereby uniquely determining the assumed ice weight. Based on this, the embodiments of the present invention first obtain the catenary arc length of the conductor under each assumed ice weight according to the stable horizontal tension, the unit synthetic line load, and the line span of the conductor under test.

[0049] Preferably, in one embodiment of the present invention, the method for obtaining the catenary arc length includes: Under each assumed ice weight, the ratio of stable horizontal tension to unit synthetic line load is used as the catenary coefficient. The catenary coefficient and the line span are substituted into the preset catenary equation to obtain the catenary arc length.

[0050] Specifically, taking any assumed ice weight as an example, the standard catenary equation described by the hyperbolic sine function in a two-dimensional plane is: Where L is the arc length of the catenary between point 0 and point x; a is the catenary coefficient, usually the tangent angle at point x. H represents the horizontal tension of the conductor, and q represents the vertical load that is uniformly distributed along the arc length. This is the hyperbolic tangent function; it is a well-known technique and will not be elaborated further. Since the standard catenary equation usually takes the lowest point of the catenary as the origin, while this embodiment takes the suspension point of the conductor under test as the origin and performs catenary analysis in the wind deflection plane, the standard catenary equation is transformed to determine the preset catenary equation: Where D is the line span, which is the distance from the first anchor point to the next anchor point, usually the straight-line distance between two towers; denoted as , where is the catenary arc length of the conductor to be measured between the two towers; b is the catenary coefficient in the wind deflection plane. The unit composite line load is the equivalent q in the wind deflection plane; It is the hyperbolic tangent function.

[0051] Furthermore, by utilizing the linear thermal expansion law and Huke's theorem, the theoretical material length of the conductor under test is analyzed, which prepares for subsequent comparison of the length deviation of the conductor under test and solving the assumed ice weight when the deviation converges.

[0052] Considering that the central tension vector represents the steady-state force vector of the conductor under test in three-dimensional force space, the tensile length of the conductor under test can be calculated by using Huke's theorem. Considering that the conductor under test will also undergo thermal expansion and contraction, the conductor temperature and the zero-stress reference length of the conductor under test can be combined, and the expansion length of the conductor under test can be calculated by using the linear thermal expansion law, so as to comprehensively evaluate the theoretical material length of the conductor under test in the current monitoring environment.

[0053] In a preferred embodiment of the present invention, the method for obtaining the theoretical length of the material includes: Based on the average conductor temperature during the monitoring period and the zero-stress reference length of the conductor under test, the theoretical expansion length of the conductor under test is calculated using the linear thermal expansion formula; based on the modulus of the central tension vector and the zero-stress reference length of the conductor under test, the theoretical tensile length of the conductor under test is calculated using the mechanical tensile deformation formula; the sum of the zero-stress reference length, the theoretical expansion length, and the theoretical tensile length is taken as the theoretical length of the material.

[0054] As an example, the average conductor temperature during the monitoring period is first calculated. Since the conductor under test may undergo irreversible plastic stretching (i.e. creep) over a long period of time, the actual length may deviate from the initial zero-stress reference length at the time of manufacture. Therefore, the actual zero-stress reference length of the conductor under test during the current monitoring period is initially estimated. In a preferred embodiment of the present invention, the method for obtaining the zero-stress reference length includes: Calculate the ice-free catenary arc length of the conductor under test in the most recent ice-free monitoring cycle; take the zero-stress reference length as the unknown independent variable and the ice-free catenary arc length as the known dependent variable, and construct the length equation based on the average conductor temperature and the average tension of the conductor under test in the most recent ice-free monitoring cycle, using the linear thermal expansion formula and the mechanical tensile deformation formula, and solve for the zero-stress reference length.

[0055] Specifically, the analysis and calculation need to be performed under the condition that the conductor under test is free of ice. First, based on the previous ice monitoring results of the historical monitoring cycle, determine the most recent ice-free monitoring cycle and calculate the catenary arc length. The calculation method is as follows: assume the ice weight = 0, solve the ratio of stable horizontal tension to unit synthetic line load, determine the catenary coefficient, and combine the line span with the preset catenary equation to obtain the catenary arc length L1, which will not be elaborated further. In other examples, the monitoring period when the average conductor temperature is higher than a preset temperature threshold, such as 5°C, can be directly used as the ice-free monitoring period. If there is no ice-free monitoring period, the solution is combined with the ice weight calculation. The solution steps are the same as the analysis steps when there is no ice, and will not be repeated here. If it is the first installation, the zero-stress reference length is directly equal to the initial zero-stress reference length at the factory.

[0056] Then, taking advantage of the unique physical length of the conductor to be tested, the length of the conductor to be tested is calculated from the perspectives of catenary angle and material thermodynamics, respectively, and the zero-stress reference length is solved.

[0057] Using the zero-stress reference length as the unknown independent variable m, and substituting the average conductor temperature T1 into the linear thermal expansion formula during the most recent ice-free monitoring period. ,in, The thermal expansion length of the conductor under test during the most recent ice-free monitoring period; The initial zero-stress reference length of the conductor under test at the time of manufacture refers to its natural length under reference temperature and without any external force. is the coefficient of linear expansion, which characterizes the thermal expansion and contraction properties of a conductor as temperature changes; The reference temperature is the temperature at which the initial zero-stress reference length is measured. Taking the zero-stress reference length as the unknown independent variable m, and substituting the average tension F1 of the conductor under test during the most recent ice-free monitoring period into the mechanical tensile deformation formula... ,in, The tensile length of the conductor under test during the most recent ice-free monitoring period; Elastic modulus, characterizing the ability of a conductor material to resist elastic deformation; Let be the cross-sectional area of ​​the conductor to be tested; Further construct the length equation: Solving for m is a well-known technique and will not be elaborated further; the solved m is the zero-stress reference length.

[0058] It should be noted that the initial zero-stress reference length Coefficient of linear expansion Elastic modulus Line span D, reference temperature These are all inherent parameters of the conductor under test, which can be obtained by consulting the circuit design data.

[0059] After determining the zero-stress reference length, the average conductor temperature T2 during the monitoring period and the zero-stress reference length m of the conductor under test are substituted back into the calculation formula of L21 above to calculate the theoretical expansion length L21' of the conductor under test; the modulus F2 of the central tension vector and the zero-stress reference length m of the conductor under test are substituted back into the calculation formula of L22 above to calculate the theoretical tensile length L22' of the conductor under test; the sum of the zero-stress reference length, the theoretical expansion length, and the theoretical tensile length is taken as the theoretical length Lc of the material.

[0060] Step S4: Iteratively adjust the assumed ice weight until the difference between the catenary arc length and the theoretical length of the material is less than a preset threshold. Calculate the ice thickness per unit length of the conductor under test based on the assumed ice weight at convergence.

[0061] Once the theoretical material length Lc of the conductor under test and the catenary arc length Lx under each assumed ice weight are determined within the monitoring period, the assumed ice weight can be continuously adjusted, and the deviation of the catenary arc length relative to the theoretical material length can be analyzed. Thus, by utilizing the uniqueness of the physical length of the conductor under test, the assumed ice weight at convergence can be solved.

[0062] In one embodiment of the present invention, assuming an initial ice weight of 0, the absolute value of the difference between the catenary arc length Lx and the theoretical material length Lc under each assumed ice weight is calculated; a preset threshold is set. When the absolute value of the difference is less than the preset threshold for the first time, convergence is determined, and the assumed ice weight at this time is taken as the estimated ice weight of the conductor to be tested. Further, by combining the relevant parameters of the conductor under test and the density of ice, the ice thickness can be calculated. That is, given the weight of ice per unit length and the density of ice, the ice volume can be calculated, and then the cross-sectional area of ​​ice can be calculated. Then, the diameter of the ice cross-section can be calculated. The ice thickness is obtained by subtracting the diameter of the conductor cross-section from the ice cross-section diameter and dividing by 2. Calculating the ice thickness is a common physical analysis method and a well-known technique, so it will not be elaborated further.

[0063] In this embodiment, the maximum number of iterations is set to 100. In other embodiments, the implementer can also adjust the assumed ice weight by combining the adjustment step size of the assumed ice weight. The assumed ice weight is the weight of ice covering a unit length of the conductor to be tested. The adjustment step size can adopt an adaptive adjustment method, such as calculating the ice weight derivative of each adjustment of the assumed ice weight, dividing the absolute value of the length difference calculated after each adjustment of the assumed ice weight by the ice weight derivative to obtain the ice weight increment. Alternatively, the assumed ice weight can be adjusted by a fixed step size method, which will not be elaborated further.

[0064] Based on the same inventive concept, the present invention also proposes an overhead power line icing thickness detection system. The system includes a memory, a processor, and a computer program stored in the memory and capable of running on the processor. When the processor executes the computer program, it implements an overhead power line icing thickness detection method as described in steps S1-S4 above.

[0065] In summary, this invention first constructs a set of tension vectors within the monitoring period, then solves for the central tension vector to obtain stable horizontal tension and stable wind deflection angle. Next, based on the assumed ice weight per unit length of the conductor and the conductor's own weight, combined with the stable wind deflection angle, the unit composite line load under each assumed ice weight is determined, and the catenary arc length of the conductor under test under each assumed ice weight is obtained in the wind deflection plane. Then, based on the central tension vector, conductor temperature, and the zero-stress reference length of the conductor under test, the theoretical material length of the conductor under test is calculated. The assumed ice weight is iteratively adjusted until the difference between the catenary arc length and the theoretical material length is less than a preset threshold. Finally, based on the assumed ice weight at convergence, the ice thickness per unit length of the conductor under test is calculated. This invention solves for the central tension vector based on the tension vector of the conductor under test, eliminates wind-induced sensor oscillations, accurately assesses the stable force field of the conductor under test, and further utilizes the unique physical length of the conductor under test to iteratively approximate and invert the icing weight, thereby accurately solving the icing thickness. This effectively solves the measurement errors caused by wind-induced galloping and sensor attitude deviations in traditional methods, and significantly improves the accuracy and robustness of icing monitoring under severe weather conditions.

[0066] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0067] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A method for detecting the icing thickness of overhead power lines, characterized in that, The method includes: The tensile force of the conductor under test, the tilt angle of the insulator string, and the conductor temperature are obtained during the monitoring period; based on the tilt angle, the tensile force at each moment is decomposed into a tensile force vector in three-dimensional space to construct a time-series tensile force vector set. Obtain the central tension vector of the tension vector set, decompose the central tension vector to obtain the stable horizontal tension and stable wind deflection angle; based on the assumed ice weight and conductor self-weight per unit length of conductor, and combined with the stable wind deflection angle, obtain the unit composite line load under each assumed ice weight. Based on the stable horizontal tension and the unit composite line load, as well as the span of the conductor under test, the catenary arc length of the conductor under test under each assumed ice weight is obtained; based on the central tension vector, the conductor temperature, and the zero-stress reference length of the conductor under test, the theoretical material length of the conductor under test is calculated. The assumed ice weight is iteratively adjusted until the difference between the catenary arc length and the theoretical length of the material is less than a preset threshold. Based on the assumed ice weight at convergence, the ice thickness per unit length of the conductor under test is calculated.

2. The method for detecting the icing thickness of overhead power lines according to claim 1, characterized in that, A three-dimensional coordinate system is constructed with the hanging point of the conductor to be measured as the origin, the horizontal direction of the conductor to be measured as the x-axis, the direction of gravity as the z-axis, and the axis perpendicular to the xoz plane as the y-axis. The tilt angle includes a horizontal tilt angle and a lateral tilt angle; wherein, the horizontal tilt angle is the deflection angle of the insulator string in the xoz plane relative to the z-axis, and the lateral tilt angle is the deflection angle of the insulator string in the yoz plane relative to the z-axis.

3. The method for detecting the icing thickness of overhead power lines according to claim 2, characterized in that, The method for obtaining the set of tension vectors includes: At each moment, based on the horizontal tilt angle decomposition, the horizontal tension component on the x-axis and the intermediate projection component located in the xoz plane are obtained; based on the lateral tilt angle decomposition, the lateral tension component on the y-axis and the vertical tension component on the z-axis of the intermediate projection component are obtained; the horizontal tension component, the lateral tension component, and the vertical tension component are used as instantaneous tension vectors; the instantaneous tension vectors within the monitoring period are sorted in time sequence, and the sorting result is used as a set of tension vectors.

4. The method for detecting the icing thickness of overhead power lines according to claim 1, characterized in that, The method for obtaining the central tension vector includes: The central tension vector of the tension vector set is solved using the minimum volume closed ellipsoid algorithm.

5. The method for detecting the icing thickness of overhead power lines according to claim 3, characterized in that, The methods for obtaining the stable horizontal tension and stable wind deflection angle include: The modulus of the horizontal component of the central tension vector on the x-axis is taken as the stable horizontal tension; the arctangent of the lateral component of the central tension vector on the y-axis and the vertical component on the z-axis is taken as the stable wind deflection angle.

6. The method for detecting the icing thickness of overhead power lines according to claim 1, characterized in that, The method for obtaining the unit synthetic line load includes: Under each assumed ice weight, the sum of the assumed ice weight per unit length of conductor and the conductor's own weight is taken as the unit composite gravity; combined with the stable wind deflection angle, the unit lateral wind load is solved based on the tangent relationship between the lateral wind load and the unit composite gravity; the combined result of the unit composite gravity and the unit lateral wind load is taken as the unit composite line load.

7. The method for detecting the icing thickness of overhead power lines according to claim 1, characterized in that, The method for obtaining the catenary arc length includes: Under each assumed ice weight, the ratio of the stable horizontal tension to the unit synthetic line load is used as the catenary coefficient. The catenary coefficient and the line span are substituted into the preset catenary equation to obtain the catenary arc length.

8. The method for detecting the icing thickness of overhead power lines according to claim 1, characterized in that, The method for obtaining the theoretical length of the material includes: Based on the average conductor temperature during the monitoring period and the zero-stress reference length of the conductor under test, the theoretical expansion length of the conductor under test is calculated using the linear thermal expansion formula; based on the modulus of the central tension vector and the zero-stress reference length of the conductor under test, the theoretical tensile length of the conductor under test is calculated using the mechanical tensile deformation formula; the sum of the zero-stress reference length, the theoretical expansion length, and the theoretical tensile length is taken as the theoretical length of the material.

9. A method for detecting the icing thickness of overhead power lines according to claim 1 or 8, characterized in that, The method for obtaining the zero-stress reference length includes: Calculate the ice-free catenary arc length of the conductor under test in the most recent ice-free monitoring cycle; take the zero-stress reference length as the unknown independent variable and the ice-free catenary arc length as the known dependent variable, and construct the length equation based on the average conductor temperature and the average tension of the conductor under test in the most recent ice-free monitoring cycle, using the linear thermal expansion formula and the mechanical tensile deformation formula, and solve for the zero-stress reference length.

10. A system for detecting the icing thickness of overhead power lines, the system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method for detecting the icing thickness of overhead power lines as described in any one of claims 1 to 9.

Images