Power transmission line icing state sensing device and method based on FBG annular sensing array

Abstract

The invention provides a power transmission line icing state sensing device and method based on an FBG annular sensing array, and belongs to the technical field of optical fiber sensing, the device comprises the FBG annular sensing array, a sector annular dumbbell structure and an annular lock catch, and the FBG annular sensing array is composed of a strain sensing unit and a temperature sensing unit. The strain sensing unit forms a circumference by six FBGs and is arranged on a power transmission line, the fan-shaped dumbbell structures are installed at the two ends of the strain sensing unit, the temperature sensing unit forms a circumference by six FBGs and is arranged on the power transmission line, and the strain sensing unit and the temperature sensing unit are tightly fixed on the surface of the power transmission line through an annular lock catch. According to the invention, the surface strain of the typical measuring point of the power transmission line is measured through the FBG annular array, and the icing state is represented by using the plane main strain. During icing, the icing quality and the icing shape of the power transmission line can be accurately sensed, and the icing disaster prevention and control capability of the power transmission line is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical fiber sensing, and relates to a device and method for sensing the icing state of a power transmission line based on an FBG annular sensor array. Background Art

[0002] Most of my country's overhead transmission lines are laid in a complex and changeable natural environment, and the climatic factors along the way have a great impact on their safe operation. For example, strong wind loads cause the line to bend, which will lead to wind deviation (dancing, sag); surface ice accumulation during the freezing rain period will increase the mechanical load on the line. The above extreme weather conditions can easily cause line flashover, ice shedding and jumping, and even serious accidents such as tower tilting and line breakage. This multi-directional non-uniform bending deformation caused by external loads is not only an objective reflection of the line's bearing capacity, but also an important reference for the formulation of de-icing strategies. Therefore, local and refined monitoring and early warning of external loads on transmission lines in a microclimate environment are necessary to ensure the safe operation of cross-regional transmission networks.

[0003] The Chinese invention patent "Method for Identifying Ice-Coated Shapes of Transmission Conductor Cross Sections Based on Ice Shape Modeling" (CN108229371A) uses a camera to capture images of transmission lines before and after icing. After preprocessing, segmenting, and extracting edges, the images are then used to determine the distribution of the maximum ice thickness and diameter in the cross section. Mathematical function modeling is then used to fit the irregular ice-coated shape of the conductor cross section to determine the ice-coated shape of the transmission line. This method is less efficient in harsh environments, as the lens is easily blocked and cannot measure the size, direction, or ice quality of the transmission line bends.

[0004] The Chinese invention patent, "A Multi-Parameter Monitoring Device for Transmission Line Galloping Characteristics" (CN117906671A), uses an inertial measurement module to collect transmission line acceleration and angular velocity data and feeds it into a microcontroller. The microcontroller then calculates the transmission line's galloping characteristic parameters, such as galloping speed, galloping amplitude, and galloping frequency. These galloping characteristic parameters are used to determine whether the transmission line is galloping. While this method reduces the cost of monitoring transmission line galloping, it can only be used to determine whether the transmission line is galloping horizontally and cannot monitor in real time the bending of the line in any direction caused by strong winds or other factors.

[0005] The Chinese invention patent, "A Cable Icing Detection Method Based on BOTDR" (CN117073746A), deploys BOTDR detection equipment, uses Brillouin frequency shift analysis to demodulate temperature and strain information, and inputs geographic environmental data surrounding the cable (such as temperature, humidity, and wind speed and direction sensors) into an icing detection training model to calculate the cable ice mass and, in turn, the equivalent ice thickness, enabling transmission line icing monitoring. However, this method cannot measure the bending or ice shape of the transmission line in any direction. Summary of the Invention

[0006] To address the challenges of existing technologies, this paper proposes a device and method for sensing the icing status of power transmission lines based on an FBG ring sensor array. This method uses a fiber Bragg Grating (FBG) ring array to measure surface strain at typical measurement points on the transmission line, and characterizes the icing status using plane principal strain. This method measures the magnitude and direction of arbitrary bending at typical measurement points on the transmission line when ice is not present. When ice is present, the device can effectively sense the quality and shape of ice on the transmission line, effectively improving the ability to prevent and control icing disasters on transmission lines.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A transmission line icing status sensing device based on an FBG annular sensor array comprises an FBG annular sensor array, a fan-shaped dumbbell structure, a thin-walled stainless steel tube, and an annular lock buckle. The FBG annular sensor array is composed of a strain sensor unit and a temperature sensor unit. Specifically:

[0009] The strain sensing unit is composed of six strain-sensitive fiberglass gratings (FBGs), arranged in a circle on the transmission line. The fan-shaped dumbbell structure is 3D-printed from a nylon material mixed with carbon fibers and installed at both ends of the strain sensing unit to increase the contact area of the optical fiber embedded in the ice and prevent relative sliding between the temperature sensing unit and the ice. The temperature sensing unit is composed of six temperature-sensitive fiberglass gratings (FBGs), arranged in a circle on the transmission line. Each temperature sensing unit is placed at the same horizontal position as the strain sensing unit to provide temperature compensation for the strain sensing unit. The temperature sensing unit is encapsulated in a thin-walled stainless steel tube to ensure that it is only affected by temperature. The annular lock is 3D-printed from a nylon material mixed with carbon fibers and securely fastens the strain sensing unit and temperature sensing unit to the surface of the transmission line.

[0010] Furthermore, the annular lock buckle is composed of two identical semicircular rings, each semicircular ring has small holes distributed at equal distances, and the strain sensing unit and temperature sensing unit on both sides of the semicircular ring pass through the small holes. The two semicircular rings are fixed in the holes on both sides of the semicircular ring by screws, and the angle between the 6 equidistant small holes and the line connecting the center of the circle is α.

[0011] A method for sensing the icing status of a power transmission line based on an FBG ring sensor array is provided. The method is implemented based on the above-mentioned device for sensing the icing status of a power transmission line and specifically comprises the following steps:

[0012] Step S1: collecting the strain value and temperature value of the transmission line, and collecting the strain value and temperature value of the transmission line in real time through the strain sensing unit and the temperature sensing unit to obtain the strain measurement value of the transmission line. Specifically:

[0013] Step S1.1, calculate the change in the central wavelength of each FBG in the strain sensing unit under the action of external force. The sensing model formula of each FBG is specifically:

[0014] Δλ B =K ε Δε+K T ΔT(1)

[0015] Where Δλ B is the change of FBG center wavelength, K ε is the strain sensitivity coefficient, Δε is the FBG strain change, K T is the temperature sensitivity coefficient of FBG, and ΔT is the temperature change of FBG.

[0016] Therefore, the central wavelength change collected by the strain sensing unit is removed by the central wavelength change under the influence of temperature, that is, the central wavelength change caused when the strain sensing unit is only subjected to external force, thereby ensuring that the strain sensing unit is only subjected to external force and there is no coupling with temperature.

[0017] In step S1.2, a temperature measurement value is obtained by a temperature sensing unit located at the same horizontal position as each strain sensing unit, and used to perform temperature compensation on the strain sensing unit. The change in the center wavelength caused by the temperature measurement value measured by the temperature sensing unit is used to eliminate the effect of temperature on the strain sensing unit in step S1.1. The specific formula for calculating the temperature measurement value is:

[0018]

[0019] Among them, T #i is the temperature measurement value of the i-th FBG of the temperature sensing unit, Δλ T#i is the wavelength change value of the i-th FBG of the temperature sensing unit, K T#i is the temperature sensitivity coefficient of the ith FBG of the temperature sensing unit, T #i0 is the initial temperature value of the i-th FBG of the temperature sensing unit.

[0020] Step S1.3, temperature compensation is performed on the center wavelength variation measured by the strain sensing unit in step S1.1 to obtain the strain measurement value of the transmission line. The calculation formula of the strain measurement value is specifically:

[0021]

[0022] Among them, ε #iis the strain measurement value of the i-th FBG of the strain sensing unit, Δλε #i is the wavelength change value of the i-th FBG of the strain sensing unit, is the strain sensitivity coefficient of the i-th FBG of the strain sensing unit, is the temperature sensitivity coefficient of the i-th FBG of the strain sensing unit, ΔT #i is the temperature change value obtained in step S1.2, ε #i0 is the initial strain value of the i-th FBG of the strain sensing unit.

[0023] Step S2: Based on the strain measurement value obtained in step S1, the plane principal strain value of the transmission line is further obtained to determine the complex plane strain state of the transmission line. Specifically:

[0024] In step S2.1, the six FBGs within the ring-shaped strain sensing units on the transmission line are grouped into equilateral triangles, with each group consisting of three FBGs, for a total of six groups. Each group has three measuring points, each located on the edge of the equilateral triangle. This arrangement is defined as a rosette. A strain transformation is performed on the strain values measured by each FBG group under the rosette to obtain the strain values at the three measuring points of the rosette. An XY coordinate system is established with the center of the equilateral triangle as the origin. The strain transformation formula is as follows:

[0025]

[0026] Among them, ε x , ε y and γ xy are the normal strains on the X and Y axes and the shear strain on the XY plane; and are the strain values of the three measuring points; α1, α2 and α3 are the angles between the three measuring points and the X-axis respectively.

[0027] Step S2.2, based on the strain values measured by each set of rosettes in step S2.1 and The plane principal strain values are calculated. The calculation formula for each set of plane principal strains is as follows:

[0028]

[0029] Where ε1 and ε2 are the plane principal strains, and the angle between them is 90°. When the plane deformation is uniform, ε1 and ε2 are equal, and θ is the direction of the plane principal strain. That is, the angle between the plane principal strain ε1 and the X-axis is θ plus 90°.

[0030] Step S2.3, based on the magnitude ε1 and direction θ of the plane principal strain obtained in step S2, further obtain the angle θ between ε1 and the X-axis in the XY coordinate system established in step S2.1 RCS , the calculation formula is as follows:

[0031]

[0032] Where i is 1 to 6, representing the θ of each rosette in step S2.1. RCS .

[0033] Step S3, based on the magnitude ε1 of the plane principal strain obtained in step S2, the direction θ of ε1, and the angle θ between ε1 and the X-axis in the XY coordinate system established in step S2.1 RCS , further calculate the size and direction of the bending deformation of the transmission line section, and realize the measurement of any bending direction of the transmission line. The specific calculation method is as follows:

[0034]

[0035] Where α is the bending direction of the transmission line, that is, the angle between the direction of force on the transmission line and the Y axis. A positive value indicates the left side of the Y axis, and a negative value indicates the right side of the Y axis. d is the bending size, k is the calibration constant, and θ RCS is the angle between the plane principal strain ε1 obtained in step S2.3 and the X-axis in the XY coordinate system established in step S2.1, θ #i is the plane principal strain angle calculated for each set of rosettes in step S2.2, and i ranges from 1 to 6.

[0036] In step S4, based on the plane principal strain ε1 obtained in step S2, ε1 is fitted with the ice mass to further measure the ice mass of the transmission line. The specific calculation method is as follows:

[0037]

[0038] Among them, ε #i is the plane principal strain measured by each set of rosettes obtained in step S2, and i is 1 to 6. #i 、b #i 、c #iε is the quadratic coefficient in the fitting function between the plane principal strain measured by each rosette and the ice mass. Its value varies in different application scenarios, and its specific value is obtained through calibration experiments. Objects of varying masses are applied to the FBG annular sensor array. These masses cause changes in the plane principal strain measured by the FBG annular sensor array, and the relationship between the plane principal strain magnitude ε1 and the applied mass is fitted. The ice mass to be measured is averaged for the six plane principal strain fittings. The ice mass obtained from each plane principal strain is two values, and the value that is greater than 0 and more consistent with the actual value is taken as the average.

[0039] Step S5: Based on step S2, the plane principal strain ε measured by each set of rosettes is obtained. #i , calculate the average value of the 6 sets of plane principal strains Then, with each set of plane principal strains ε #i Calculate the difference Δ, and identify whether the ice shape is round or C-shaped based on the difference under different ice shapes. Specifically:

[0040] In step S5.1, the average value of the six sets of plane principal strains is calculated as follows:

[0041]

[0042] Step S5.2, each set of plane principal strains ε #i and the average The difference is calculated as follows:

[0043]

[0044] Here, i is 1 to 6.

[0045] Step S5.3, the principal strain difference Δ of each rosette plane obtained in step S5.2 is #i Compare it with the threshold η to determine the shape of the ice. The specific method is as follows:

[0046]

[0047] Wherein, η is the threshold value, and i ranges from 1 to 6.

[0048] When the difference values of each group are less than or equal to η, the ice shape is determined to be round ice; when the difference values of each group are greater than η, the ice shape is determined to be C-shaped ice. The threshold range is 0-40με.

[0049] The beneficial effects of the present invention are:

[0050] (1) The present invention uses an FBG annular sensor array to collect the strain values of the transmission line. Furthermore, the magnitude ε1 and direction θ of the plane principal strain of the transmission line are obtained through strain rosette transformation. The magnitude d and direction α of the bending deformation of the transmission line are then calculated based on the magnitude ε1 and direction θ of the plane principal strain. This allows the measurement of the magnitude and direction of the bending of the transmission line in any direction.

[0051] (2) The present invention collects the strain value of the transmission line through the FBG annular sensor array, further obtains the size of the plane principal strain ε1 of the transmission line through the strain rosette transformation, and then obtains the size of the plane principal strain ε1 of each group of strain rosettes according to the fitting relationship between the size of the plane principal strain ε1 and the ice mass. #i The corresponding ice covering mass is obtained, and the average value of the ice covering mass obtained in six groups is calculated to obtain the stable ice covering mass.

[0052] (3) The present invention collects the strain value of the transmission line through the FBG annular sensor array, and further obtains the size of the plane principal strain ε of the transmission line through strain rosette transformation #i , and then calculate the plane principal strain ε of each rosette #i Find the average value ε, and set the average value With ε #i The difference Δ is calculated and compared with the threshold η. The difference between the two ice shapes in the difference Δ is used to determine whether the transmission line is covered with circular ice or C-shaped ice. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a schematic diagram of the packaging structure of the FBG annular sensor array in the ice state sensing device of the present invention.

[0054] Figure 2 This is a schematic diagram of the spatial structure of the FBG annular sensor array in the ice state sensing device of the present invention.

[0055] Figure 3 This is a specific layout diagram of the FBG annular sensor array in the ice state sensing device of the present invention; Figure 3 (a) is the FBG ring sensor array layout scheme; Figure 3 (b) is a side view of the layout plan.

[0056] Figure 4 Schematic diagram of the annular lock in the ice state sensing device of the present invention.

[0057] Figure 5 This is a diagram of a plane principal strain sensing model provided in an embodiment of the present invention.

[0058] Figure 6 Schematic diagram of a vertical bending load experiment of an FBG annular sensor array provided in an embodiment of the present invention.

[0059] Figure 7 This is a graph showing the strain results of a vertical bending load experiment on the FBG annular sensor array provided in an embodiment of the present invention.

[0060] Figure 8 This is a diagram showing the plane principal strain results of the vertical bending load experiment on the FBG annular sensor array provided in an embodiment of the present invention.

[0061] Figure 9 This is a diagram showing the plane principal strain direction results of the vertical bending load experiment on the FBG annular sensor array provided in an embodiment of the present invention.

[0062] Figure 10 This is a graph showing the strain results of the FBG annular sensor array provided in an embodiment of the present invention under bending loads in different directions; Figure 10 (a) is the strain measurement result of FBG ring sensor array; Figure 10 (b) in the figure is the direction of load application in the bending load test in different directions.

[0063] Figure 11 This is a diagram showing the plane principal strain results of the FBG annular sensor array provided in an embodiment of the present invention under bending load experiments in different directions; Figure 11 (a) is the plane principal strain measurement result of the FBG ring sensor array; Figure 11 (b) is the plane principal strain ε1 and θ of the X axis RCS Schematic diagram.

[0064] Figure 12 This is a diagram showing the plane principal strain direction results of the FBG annular sensor array provided in an embodiment of the present invention subjected to bending load experiments in different directions.

[0065] Figure 13 This is a graph showing the strain results of a heavy load test on the FBG annular sensor array provided in an embodiment of the present invention.

[0066] Figure 14 This is a diagram showing the plane principal strain results of a heavy load test on the FBG annular sensor array provided in an embodiment of the present invention.

[0067] Figure 15 Schematic diagram of an ice coating experimental device in an embodiment of the present invention.

[0068] Figure 16 This is a diagram showing the principal strain results of a C-shaped ice plane in an ice-covered experiment using an FBG annular sensor array provided in an embodiment of the present invention.

[0069] Figure 17 This is a diagram showing the principal strain magnitude results of the circular ice plane in the ice-covered experiment of the FBG annular sensor array provided in an embodiment of the present invention.

[0070] Figure 18 This is a flow chart of the method for determining ice-covered shape using an FBG annular sensor array provided by the present invention.

[0071] In the figure, 1 is a strain sensing unit; 2 is a temperature sensing unit; 3 is a fan-shaped dumbbell structure; 4 is a ring lock; 5 is a thin-walled stainless steel tube; 6 is an optical fiber; 7 is a fiber core; 8 is a cladding; 9 is a high and low temperature chamber; 10 is a nozzle; 11 is a bearing; 12 is a fixed pile; 13 is a heating wire. DETAILED DESCRIPTION

[0072] To facilitate understanding of the present invention, the present invention is described in more detail below with reference to the accompanying drawings and specific embodiments. The accompanying drawings provide preferred embodiments of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0073] like Figure 1 、 Figure 3 As shown, a transmission line icing status sensing device based on an FBG annular sensor array is provided. The transmission line icing status sensing device includes an FBG annular sensor array, a fan-shaped dumbbell structure 3, a thin-walled stainless steel tube 5, and an annular lock 4. The FBG annular sensor array is composed of a strain sensor unit 1 and a temperature sensor unit 2. Specifically:

[0074] The strain sensing unit 1 consists of six strain-sensitive fiber optic grids (FBGs). The length of the strain sensing FBGs is a = 10 mm. The six FBGs are arranged in a circle on the transmission line, with a spacing of e = 16.7 mm between adjacent FBGs. The fan-shaped dumbbell 3 is 3D-printed from a nylon material mixed with carbon fiber. It is installed at both ends of the strain sensing unit 1 to increase the contact area of the optical fiber embedded in the ice and prevent relative sliding between the strain sensing unit 1 and the ice. The temperature sensing unit 2 consists of six temperature-sensitive fiber optic grids (FBGs). The six FBGs are arranged in a circular pattern on the transmission line. Each temperature sensing unit 2 is placed at the same level as the strain sensing unit 1, with a spacing of d = 30 mm between them. This provides temperature compensation for the strain sensing unit 1. The temperature sensing unit 2 is encapsulated in a thin-walled stainless steel tube 5 to ensure that it is only affected by temperature. The encapsulation structure length b = 25 mm. The annular lock buckle 4 is made of nylon material mixed with carbon fiber through 3D printing. Its function is to tightly fix the strain sensing unit 1 and the temperature sensing unit 2 on the surface of the transmission line.

[0075] In this embodiment, the annular lock buckle 4 is composed of two identical semicircular rings, each with three equally spaced small holes for allowing the strain sensing unit 1 and the temperature sensing unit 2 located between the annular lock buckles to pass through the small holes. The two semicircular rings are fixed to the holes on both sides of the semicircular rings by screws. The angle between the six equally spaced small holes and the line connecting the center of the circle is 60°. Figure 3 (b) shown.

[0076] A method for sensing the icing status of a power transmission line based on an FBG ring sensor array is provided. The method is implemented based on the above-mentioned device for sensing the icing status of a power transmission line and specifically comprises the following steps:

[0077] Step S1: collecting the strain value and temperature value of the transmission line, and collecting the strain value and temperature value of the transmission line in real time through the strain sensing unit 1 and the temperature sensing unit 2 to obtain the strain measurement value of the transmission line. Specifically:

[0078] Step S1.1, calculate the change in the central wavelength of each FBG in the strain sensing unit 1 under the action of external force. The sensing model formula of each FBG is specifically as follows:

[0079] Δλ B =K ε Δε+K T ΔT(12)

[0080] Where Δλ B is the change of FBG center wavelength, K ε is the strain sensitivity coefficient, Δε is the FBG strain change, K T is the temperature sensitivity coefficient of FBG, and ΔT is the temperature change of FBG.

[0081] Therefore, the change in the central wavelength collected by the strain sensing unit 1 minus the change in the central wavelength under the influence of temperature is the change in the central wavelength caused when the strain sensing unit 1 is only subjected to external force, thereby ensuring that the strain sensing unit 1 is only subjected to external force and there is no coupling with temperature.

[0082] In step S1.2, a temperature measurement value is obtained by a temperature sensing unit located at the same horizontal position as each strain sensing unit, and used to perform temperature compensation on the strain sensing unit. The change in the center wavelength caused by the temperature measurement value measured by the temperature sensing unit is used to eliminate the effect of temperature on the strain sensing unit in step S1.1. The specific formula for calculating the temperature measurement value is:

[0083]

[0084] Among them, T #i is the temperature measurement value of the i-th FBG of temperature sensing unit 2, ΔλT#i is the wavelength change value of the i-th FBG of temperature sensing unit 2, K T#i is the temperature sensitivity coefficient of the i-th FBG of temperature sensing unit 2, T #i0 is the initial temperature value of the i-th FBG of the temperature sensing unit 2.

[0085] Step S1.3, temperature compensation is performed on the central wavelength variation measured by the strain sensing unit 1 in step S1.1 to obtain the strain measurement value of the transmission line. The calculation formula of the strain measurement value is specifically:

[0086]

[0087] Among them, ε #i is the strain measurement value of the i-th FBG of strain sensing unit 1, Δλε #i is the wavelength change value of the i-th FBG of strain sensing unit 1, is the strain sensitivity coefficient of the i-th FBG of strain sensing unit 1, is the temperature sensitivity coefficient of the i-th FBG of the strain sensing unit 1, ΔT #i is the temperature change value obtained in step S1.2, ε #i0 is the initial strain value of the i-th FBG of strain sensing unit 1.

[0088] Step S2: Based on the strain measurement value obtained in step S1, the plane principal strain value of the transmission line is further obtained to determine the complex plane strain state of the transmission line. Specifically:

[0089] In step S2.1, the six FBGs within the ring-shaped strain sensing units on the transmission line are grouped into equilateral triangles, with each group consisting of three FBGs, for a total of six groups. Each group has three measuring points, each located on the edge of the equilateral triangle. This arrangement is defined as a rosette. A strain transformation is performed on the strain values measured by each FBG group under the rosette to obtain the strain values at the three measuring points of the rosette. An XY coordinate system is established with the center of the equilateral triangle as the origin. The strain transformation formula is as follows:

[0090]

[0091] Among them, ε x , ε y and γ xy are the normal strains on the X and Y axes and the shear strain on the XY plane; and are the strain values of the three measuring points; α1, α2 and α3 are the angles between the three measuring points and the X-axis respectively.

[0092] Table 1 shows six groups of strain rosettes.

[0093]

[0094] Step S2.2, based on the strain values measured by each set of rosettes in step S2.1 and The plane principal strain value is calculated. The plane principal strain calculation formula is as follows:

[0095]

[0096] Where ε1 and ε2 are the plane principal strains, and the angle between them is 90°. When the plane deformation is uniform, ε1 and ε2 are equal. θ is the direction of the plane principal strain: the angle between ε1 and the X-axis, and the angle between ε2 and the X-axis is θ plus 90°. The calculation methods for the plane principal strain magnitude and direction are the same for the other five rosettes.

[0097] In step S2.3, based on the plane principal strain direction θ obtained in step S2.2, the angle between ε1 and the X-axis in the XY coordinate system established in step S2.1 can be further obtained. The calculation formula is as follows:

[0098]

[0099] Where i is 1 to 6, representing the θ of each rosette in step S2.1. RCS .

[0100] Step S3, based on the magnitude ε1 of the plane principal strain obtained in step S2, the direction θ of ε1, and the angle θ between ε1 and the X-axis in the XY coordinate system established in step S2.1 RCS , further calculate the size and direction of the bending deformation of the transmission line section, and realize the measurement of any bending direction of the transmission line. The specific calculation method is as follows:

[0101]

[0102] Where α is the bending direction of the transmission line, that is, the angle between the direction of force on the transmission line and the Y axis. A positive value indicates the left side of the Y axis, and a negative value indicates the right side of the Y axis. d is the bending size, k is the calibration constant, and θ RCS is the angle between the plane principal strain ε1 obtained in step S2.3 and the X-axis in the XY coordinate system established in step S2.1, θ #i is the plane principal strain angle calculated for each set of rosettes in step S2.2, and i ranges from 1 to 6.

[0103] like Figure 3The FBG ring sensor array is laid out in a way that a vertical displacement load is applied to the transmission line, causing the transmission line to bend. The direction of the displacement load points from the action position to the center of the circle. The magnitude of the displacement load is d0, ranging from 0-2mm, and the change step is 0.1mm. Assume that the top is #1, and the numbers #2 to #6 are clockwise. Among them, negative strain represents compression, and positive strain represents tension. According to step S1 and step S2, the measurement results of strain, plane principal strain magnitude and direction are obtained. Figure 7 、 Figure 8 、 Figure 9 shown. Figure 7 This is the strain result diagram of the vertical bending load experiment of the FBG ring sensor array. Figure 7 It can be seen that #1, #2, and #6 above the transmission line are in compression, and the compression strain value of #1 is the largest. #2 and #6 are symmetrically distributed on both sides of #1, and the strain magnitudes of the two are almost the same. #3, #4, and #5 below the transmission line are in tension, and the tensile strain value of #4 is the largest. #3 and #5 are symmetrically distributed on both sides of #4, and the strain magnitudes of the two are basically the same. Figure 8 This is the result diagram of the plane principal strain of the FBG ring sensor array vertical bending load test. Figure 8 It can be seen that the situation of the plane principal strain magnitude is basically the same as the strain magnitude trend. When the bending deformation magnitude d0 is 1 mm, the plane principal strain magnitude ε1 is measured to be 520.4 με. According to the calculation method of the bending deformation magnitude of the transmission line in step S3, when the plane principal strain magnitude ε1 is 515.29 με, the bending deformation magnitude is 1 mm, and the error is only 1%; Figure 9 The results of the plane principal strain direction of the FBG ring sensor array vertical bending load test are shown in Figure 2. Figure 9 Get 6 sets of plane principal strain directions According to step S2.3, the plane principal strain direction is substituted into the calculated θ RCS =0°, and then according to step S3, the bending direction of the transmission line is obtained to be α=0°, that is, the angle with the Y axis is 0°, which is consistent with the direction when the vertical load is applied.

[0104] Similarly, displacement loads in different directions are applied to the transmission line. Taking α=10° as an example, the strain, plane principal strain magnitude and direction are obtained according to step S1, step S2.1 and step S2.2. Figure 10 This is the strain result diagram of the FBG ring sensor array under bending load experiments in different directions. Figure 11 This is the result of the plane principal strain of the FBG ring sensor array under bending load experiments in different directions. Figure 10 、 Figure 11It can be seen that the change trend of strain and plane principal strain is the same as that of the vertical load test. When the bending deformation d0 is 1 mm, the measured plane principal strain ε1 is 520.4 με. According to the calculation method of the bending deformation in step S3, when the plane principal strain ε1 is 515.29 με, the bending deformation is 1 mm, and the error is 0.94%. Figure 12 The results of the plane principal strain direction of the FBG ring sensor array vertical bending load test are shown in Figure 2. Figure 12 Get 6 sets of plane principal strain directions According to step S2.3, the plane principal strain direction is substituted into the calculated θ RCS = -5, and then according to step S3, the bending direction α = 10°, that is, the angle with the Y axis is 10° and it is located to the left of the Y axis. This result is consistent with the direction of the applied vertical load. This shows that the FBG annular sensor array of the present invention can measure the magnitude and direction of the transmission line bend.

[0105] Step S4: When the transmission line is covered with ice, the plane principal strain ε1 obtained in step S2 is used to fit ε1 with the ice mass to further measure the ice mass of the transmission line. The specific calculation method is as follows:

[0106]

[0107] Among them, ε #i is the plane principal strain measured by each set of rosettes obtained in step S2, and i is 1 to 6. #i 、b #i 、c #i is the quadratic term coefficient in the fitting function between the plane principal strain magnitude measured by each set of rosettes and the ice mass. The value will vary accordingly in different application scenarios. The specific value is obtained through calibration experiments. The fitting coefficients in this embodiment are shown in Table 2. The ice mass to be measured is obtained by averaging the ice mass obtained by fitting the six sets of plane principal strain magnitudes.

[0108] Table 2, quadratic coefficient fitting table

[0109] <![CDATA[a #i ]]> <![CDATA[-1.31×10 -4 ]]> <![CDATA[-7.55×10 -6 ]]> <![CDATA[1.74×10 -5 ]]> <![CDATA[1.29×10 -4 ]]> <![CDATA[3.83×10 -5 ]]> <![CDATA[-2.42×10 -5 ]]> <![CDATA[b #i ]]> -0.051 -0.064 0.030 0.057 0.034 -0.037 <![CDATA[c #i ]]> -10.32 9.41 10.14 13.76 2.31 -8.57 <![CDATA[R 2 ]]> 0.997 0.996 0.997 0.996 0.998 0.997

[0110] The FBG ring sensor array is arranged as follows Figure 3 As shown in Figure 1, three evenly distributed weights are used to simulate ice loads for a heavy load test. Each weight is 15 cm apart, with a mass range of 0 to 500 g and a step size of 50 g. The strain and plane principal strain measurement results are obtained according to steps S1, S2.1, and S2.2. Figure 13 、 Figure 14 shown. Figure 13 This is the strain result diagram of the FBG ring sensor array heavy load test. Figure 14 This is the result diagram of the plane principal strain of the FBG ring sensor array heavy load test. Figure 13 It can be seen that ε #1 , ε #2 , ε #6 A negative value indicates that the upper part of the cable is compressed; #3 , ε #4 , ε #5 A positive value indicates that the upper part of the cable is stretched, which is consistent with the actual situation. When the load weight is 1500g, ε #1 The compression deformation is the largest at the position, with a strain of -382.7με, ε #4 The maximum tensile deformation is 391.7με at the position. Figure 14 The magnitude of the plane principal strain measured by each set of rosettes is obtained according to step S4 and the fitting coefficients in Table 2. The mass of ice at this time is 650.76 g. After the test, the mass of water melted from the ice is measured to be 602.43 g, with an error of 8.02%. This also proves that the FBG annular sensor array of the present invention is capable of measuring the mass of ice.

[0111] Step S5: When the transmission line is covered with ice, the plane principal strain ε measured by each set of rosettes is obtained based on step S2. #i , calculate the average value of the 6 sets of plane principal strains Then, the difference Δ is calculated from each set of plane principal strains, and the difference under different ice shapes is used to identify whether the ice shape is circular ice or C-shaped ice. Specifically:

[0112] In step S5.1, the average value of the six sets of plane principal strains is calculated as follows:

[0113]

[0114] Step S5.2, each set of plane principal strains ε #i and the average The difference is calculated as follows:

[0115]

[0116] Here, i is 1 to 6.

[0117] Step S5.3, the principal strain difference Δ of each rosette plane obtained in step S5.2 is #i Compare with the threshold η to determine the shape of the ice. In this embodiment, the threshold η is 30με. The specific method is as follows:

[0118]

[0119] Wherein, η is the threshold value, and i ranges from 1 to 6.

[0120] When the difference between each group is less than or equal to η, the ice shape is determined to be round ice. When the difference between each group is greater than η, the ice shape is determined to be C-shaped ice. The threshold range is 0-40 με. In this embodiment, the threshold is 30 με.

[0121] The FBG ring sensor array is arranged as follows Figure 3 As shown, proceed as Figure 15 The transmission line icing experiment shown in the figure. The first ice shape is C-shaped ice, and the second ice shape is circular ice. The rest of the experimental conditions are the same. Figure 18 The figure is a flow chart for judging the shape of ice. According to step S1, step S2.1 and step S2.2, the measurement results of the plane principal strain of C-shaped ice and circular ice are obtained, as shown in Figure 2. Figure 16 、 Figure 17 shown. Figure 16 This is the result of the principal strain of the C-shaped ice plane in the FBG ring sensor array ice coating experiment. Figure 17 This is the result of the principal strain on the circular ice plane of the FBG ring sensor array ice covering experiment. Figure 16 The plane principal strain of the C-shaped ice is calculated according to step S5.1 to calculate the average value of the six sets of plane principal strains. is 187.2με; then calculate each set of plane principal strains ε according to step S5.2 #i and the average Difference Δ #i , and get the difference value Δ for each group #i are all greater than 30με, and the ice shape is judged to be C-shaped ice, which is consistent with the experimental conditions. Figure 17 The plane principal strain of the medium circular ice is calculated according to step S5.1 to calculate the average value of the six sets of plane principal strains. is 91.25με; then calculate each set of plane principal strains ε according to step S5.2 #i and the average Difference Δ #i , and get the difference value Δ for each group #i The FBG annular sensor array in this embodiment is based on the Figure 18 The judgment method shown can identify the shape of ice cover.

[0122] Those skilled in the art will appreciate that the above-described embodiments merely represent several embodiments of the present invention, and their descriptions are relatively specific and detailed, but should not be construed as limiting the scope of the present invention. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the scope of the present invention, and these modifications and improvements fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the appended claims.

Claims

1. A transmission line ice state sensing device based on an FBG ring sensor array, characterized in that: The transmission line icing status sensing device includes an FBG annular sensor array, a fan-shaped dumbbell structure, a thin-walled stainless steel tube, and an annular lock buckle, wherein the FBG annular sensor array is composed of a strain sensor unit and a temperature sensor unit; specifically: The strain sensing unit is composed of six strain-sensitive FBGs, which are arranged in a circle on the transmission line. The fan-shaped dumbbell structure is made of nylon material mixed with carbon fiber through 3D printing and is installed at both ends of the strain sensing unit. The temperature sensing unit is composed of six temperature-sensitive FBGs, which are arranged in a circle on the transmission line, and each temperature sensing unit is placed at the same level as the strain sensing unit; The annular lock tightly fixes the strain sensing unit and the temperature sensing unit on the surface of the power transmission line.

2. The FBG ring sensor array-based transmission line ice state sensing device according to claim 1, characterized in that: The temperature sensing unit is packaged in a thin-walled stainless steel tube.

3. The FBG ring sensor array-based transmission line ice state sensing device according to claim 1, characterized in that: The annular lock buckle is made of nylon material mixed with carbon fiber through 3D printing.

4. The FBG ring sensor array-based transmission line ice state sensing device according to claim 1, characterized in that: The annular lock buckle consists of two identical semicircular rings, each with small holes distributed at equal distances. The strain sensing unit and the temperature sensing unit on both sides of the semicircular ring pass through the small holes. The two semicircular rings are fixed in the holes on both sides of the semicircular ring by screws, and the angles between the six equally spaced small holes and the line connecting the center of the circle are all α.

5. A method for sensing ice coverage on a transmission line based on an FBG ring sensor array, characterized in that: The method for sensing the icing status of a transmission line is implemented based on the device for sensing the icing status of a transmission line according to any one of claims 1 to 4, and specifically comprises the following steps: Step S1, collecting the strain value and temperature value of the transmission line, collecting the strain value and temperature value of the transmission line in real time through the strain sensing unit and the temperature sensing unit, and obtaining the strain measurement value of the transmission line; Step S2, based on the strain measurement value obtained in step S1, obtaining the plane principal strain value of the transmission line to determine the complex plane strain state of the transmission line; Step S3, based on the magnitude ε1 of the plane principal strain obtained in step S2, the direction θ of ε1, and the angle θ between ε1 and the X-axis in the XY coordinate system established in step S2.1 RCS , further calculate the size and direction of the bending deformation of the transmission line section, and realize the measurement of any bending direction of the transmission line; Step S4: Based on the plane principal strain ε1 obtained in step S2, fitting ε1 with the ice mass is performed to further measure the ice mass of the transmission line; Step S5: Based on step S2, the plane principal strain ε measured by each set of rosettes is obtained. #i , calculate the average value of the 6 sets of plane principal strains Then, with each set of plane principal strains ε #i Calculate the difference Δ and, based on the difference under different ice shapes, identify whether the ice shape is round ice or C-shaped ice.

6. The method for sensing ice coverage status of a transmission line based on an FBG ring sensor array according to claim 5, characterized in that: The step S1 is specifically as follows: Step S1.1, calculate the change in the central wavelength of each FBG in the strain sensing unit under the action of external force. The sensing model formula of each FBG is specifically: Dl B =K ε No+K T ΔT (1) Where Δλ B is the change of FBG center wavelength, K ε is the strain sensitivity coefficient, Δε is the FBG strain change, K T is the temperature sensitivity coefficient of FBG, ΔT is the temperature change of FBG; Step S1.2, the influence of temperature on the strain sensing unit in step S1.1 is eliminated by using the central wavelength change caused by the temperature measurement value measured by the temperature sensing unit; the specific calculation formula of the temperature measurement value is: Among them, T #i is the temperature measurement value of the i-th FBG of the temperature sensing unit, Δλ T#i is the wavelength change value of the i-th FBG of the temperature sensing unit, K T#i is the temperature sensitivity coefficient of the ith FBG of the temperature sensing unit, T #i0 is the initial temperature value of the i-th FBG of the temperature sensing unit; Step S1.3, temperature compensation is performed on the central wavelength variation measured by the strain sensing unit in step S1.1 to obtain a strain measurement value of the transmission line; the calculation formula of the strain measurement value is specifically: Among them, ε #i is the strain measurement value of the i-th FBG of the strain sensing unit, Δλε #i is the wavelength change value of the i-th FBG of the strain sensing unit, is the strain sensitivity coefficient of the i-th FBG of the strain sensing unit, is the temperature sensitivity coefficient of the i-th FBG of the strain sensing unit, ΔT #i is the temperature change value obtained in step S1.2, ε #i0 is the initial strain value of the i-th FBG of the strain sensing unit.

7. The method for sensing ice coverage status of a transmission line based on an FBG ring sensor array according to claim 5, characterized in that: The step S2 is specifically as follows: In step S2.1, the six FBGs within the ring-shaped strain sensing units on the transmission line are grouped into equilateral triangles, with three FBGs forming one group, for a total of six groups. Each group has three measuring points, and each measuring point is located on the edge of the equilateral triangle. This arrangement is defined as a rosette. The strain values measured by each group of FBGs under the rosette are transformed to obtain the strain values of the three measuring points of the rosette. An XY coordinate system is established with the center of the equilateral triangle as the coordinate origin. The strain transformation formula is as follows: Among them, ε x , ε y and γ xy are the normal strains on the X and Y axes and the shear strain on the XY plane; and is the strain value of the three measuring points; α1, α2 and α3 are the angles between the three measuring points and the X-axis respectively; Step S2.2, based on the strain values measured for each set of rosettes in step S2.1 and The plane principal strain values are calculated. The calculation formula for each set of plane principal strains is as follows: Where ε1 and ε2 are the magnitudes of the plane principal strains, and the angle between them is 90°. When the plane deformation is uniform, ε1 and ε2 are equal in magnitude. θ is the direction of the plane principal strain, that is, the angle between the plane principal strain ε1 and the X-axis, and the angle between ε2 and the X-axis is θ plus 90°. Step S2.3, based on the magnitude ε1 and direction θ of the plane principal strain obtained in step S2, further obtain the angle θ between ε1 and the X-axis in the XY coordinate system established in step S2.1 RCS , the calculation formula is as follows: Where i is 1 to 6, representing the θ of each rosette in step S2.

1. RCS .

8. The method for sensing ice coverage status of a transmission line based on an FBG ring sensor array according to claim 5, characterized in that: The calculation method of step S3 is specifically as follows: Where α is the bending direction of the transmission line, that is, the angle between the force direction of the transmission line and the Y axis. A positive value indicates the left side of the Y axis, and a negative value indicates the right side of the Y axis. d is the bending size, k is the calibration constant, and θ is the bending angle. RCS is the angle between the plane principal strain ε1 obtained in step S2.3 and the X-axis in the XY coordinate system established in step S2.1, θ #i is the plane principal strain angle calculated for each set of rosettes in step S2.2, and i ranges from 1 to 6.

9. The method for sensing ice coverage status of a transmission line based on an FBG ring sensor array according to claim 5, characterized in that: The calculation method of step S4 is specifically as follows: Among them, ε #i is the plane principal strain measured by each set of rosettes obtained in step S2, i is 1 to 6; a #i 、b #i 、c #i is the quadratic coefficient in the fitting function between the plane principal strain measured by each set of rosettes and the ice mass. The ice mass to be measured is obtained by averaging the ice mass obtained by fitting the 6 groups of plane principal strains.

10. The method for sensing ice coverage status of a transmission line based on an FBG ring sensor array according to claim 5, characterized in that: The step S5 is specifically as follows: In step S5.1, the average value of the six sets of plane principal strains is calculated as follows: Step S5.2, each set of plane principal strains ε #i and the average The difference is calculated as follows: Where i is 1 to 6; Step S5.3, the principal strain difference Δ of each rosette plane obtained in step S5.2 is #i Compare with the threshold η to determine the shape of the ice cover; the specific method is as follows: Where η is the threshold value, i ranges from 1 to 6; When the difference values of each group are less than or equal to η, the ice shape is judged to be round ice; when the difference values of each group are greater than η, the ice shape is judged to be C-shaped ice; the threshold range is 0-40με.

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