High-density ultra-weak grating dynamic sensing array sensor for OPGW and intelligent connector box and sag monitoring method

Abstract

The invention discloses a high-density ultra-weak grating dynamic sensing array sensor for an OPGW (Optical Fiber Composite Overhead Ground Wire) and an intelligent connector box and a sag monitoring method, and belongs to the technical field of on-line detection of high-voltage transmission lines, the high-density ultra-weak grating dynamic sensing array sensor comprises an optical fiber, and a plurality of periodic grating arrays are engraved on the optical fiber; the optical fiber is sequentially coated with a gradient refractive index cladding, a mechanical enhancement layer and an outer sheath. According to the invention, through the design of the ultra-weak grating array, the gradient refractive index cladding and the composite enhancement layer, the problems of low spatial resolution and poor strain transmission efficiency in the prior art are solved; and the TLS-ESPRIT high-precision demodulation and dynamic compensation model is combined on sag monitoring, so that the sag calculation precision of dynamic working condition monitoring is improved.

Description

Technical Field

[0001] This invention relates to the field of online detection technology for high-voltage transmission lines, and more specifically to a high-density ultra-weak grating dynamic sensing array sensor and sag monitoring method for OPGW and smart junction boxes. Background Technology

[0002] Currently, the mainstream technology for OPGW (Optical Fiber Composite Overhead Ground Wire) sag monitoring is distributed fiber optic sensing technology based on BOTDR (Brillouin Optical Time Domain Reflectometry). Its core structure includes an optical demodulation module (composed of a laser, electro-optic modulator, erbium-doped fiber amplifier, and fiber coupler), a sensing unit (using the internal communication fiber of the OPGW as the sensing medium), a data acquisition system (including a circulator, fiber Bragg grating filter, balanced detector, and acquisition card), and an algorithm processing unit (converting fiber strain into sag values ​​using the catenary equation and temperature compensation algorithm). The component connections are as follows: the laser output is split into pump light and probe light, which are modulated and amplified before being injected into the OPGW fiber. The reflected Brillouin scattered light is filtered and mixed with the local reference light. Finally, the strain distribution is obtained through photoelectric conversion and algorithm demodulation. This technology acquires the Brillouin frequency shift spectrum of the fiber at fixed time intervals (typically 5-10 minutes), and the spatial resolution depends on the pulse width (typically 1-5 meters). However, this technology has the following drawbacks: insufficient spatial resolution (1-5 meters), making it difficult to capture local sag abrupt changes; severe temperature cross-sensitivity, with existing single-point temperature compensation unable to adapt to complex temperature gradients; strain transfer efficiency between the optical fiber and the OPGW aluminum-clad steel layer is only 60-70%, and the creep effect of the sheath material is not considered; poor real-time performance, with a single scan taking about 2 minutes, which cannot meet the requirements of dynamic operating conditions; and high installation and maintenance costs, requiring the deployment of large demodulation equipment and regular calibration of fiber Bragg grating filters.

[0003] Therefore, how to provide a high-density ultra-weak grating dynamic sensing array sensor and sag monitoring method with high spatial resolution and high strain transfer efficiency for OPGW and smart junction boxes is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the present invention provides a high-density ultra-weak grating dynamic sensing array sensor and sag monitoring method for OPGW and smart junction boxes. Through the design of ultra-weak grating array, graded refractive index cladding and composite reinforcement layer, the invention solves the problems of low spatial resolution and poor strain transfer efficiency of traditional technology. In terms of algorithm, the invention combines TLS-ESPRIT high-precision demodulation and dynamic compensation model to improve the sag calculation accuracy of dynamic working condition monitoring.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: On one hand, the present invention provides a high-density ultra-weak grating dynamic sensing array sensor for OPGW and smart junction boxes, comprising: an optical fiber, wherein a plurality of periodic grating arrays are etched on the optical fiber; the optical fiber is sequentially covered with a graded refractive index cladding, a mechanical reinforcement layer, and an outer sheath.

[0006] Preferably, the grating array comprises 5 gratings.

[0007] Preferably, the graded refractive index cladding is made of a self-made graded refractive index polyurethane material, which is extruded over the optical fiber.

[0008] Preferably, the mechanical reinforcement layer is made of a mixture of borosilicate glass fiber and epoxy resin, and is coated on the outside of the gradient refractive index cladding through a two-layer gradient curing process.

[0009] Preferably, the outer sheath is made of a polymer material and is extruded over the mechanical reinforcement layer.

[0010] On the other hand, the present invention provides an OPGW sag monitoring method, utilizing the above-mentioned high-density ultra-weak grating dynamic sensing array sensor for OPGW and smart junction boxes, comprising the following steps: A high-density ultra-weak grating dynamic sensing array sensor is connected to a demodulation system. The high-density ultra-weak grating dynamic sensing array sensor is used to sense the wavelength information of the OPGW in real time, and the wavelength information is transmitted to the demodulation system for processing to obtain data. The strain transfer compensation algorithm is used, and the compensation coefficient is dynamically adjusted based on the real-time monitored wavelength data through a Kalman filter; The collected wavelength data is compensated in real time based on the dynamically adjusted compensation coefficient. The compensated wavelength data is processed using a quadratic integral algorithm to calculate the sag value of the OPGW.

[0011] Preferably, the compensated strain data is processed using a quadratic integral algorithm to calculate the sag value of the OPGW, including: Calculate a certain moment based on the wavelength data. t Dependent variables: ; in For the demodulation system to acquire the i-th sensing grating point in t The change in wavelength at any given time. For strain sensitivity; Calculate the dynamic acceleration based on the strain: ; Where g is the acceleration due to gravity, E is Young's modulus, and m is the linear density. This refers to the local tilt angle of the conductor; The displacement is obtained by performing a second integral on the dynamic acceleration: speed ; Sag change ; Where Δt is the time step, k is the kth time interval, and n is the total number of time intervals, satisfying the following relationship: ; Superimpose the sag change onto the initial sag To obtain real-time sag .

[0012] As can be seen from the above technical solution, compared with the prior art, this invention discloses a high-density ultra-weak grating dynamic sensing array sensor and sag monitoring method for OPGW and smart junction boxes. Structurally, through the design of an ultra-weak grating array, a graded refractive index cladding, and a composite reinforcement layer, it solves the problems of low spatial resolution and poor strain transfer efficiency in traditional technologies. In sag monitoring, the strain transfer compensation algorithm and Kalman filter compensate for the difference in strain transfer efficiency in real time, eliminating the strain transfer error between the optical fiber and the optical cable sheath, improving the accuracy of strain data, and thus improving the accuracy of OPGW sag monitoring. By dynamically adjusting the compensation coefficient in real time through the Kalman filter, real-time strain transfer compensation is achieved, enabling the monitoring system to reflect the changes in OPGW sag in a timely manner. Furthermore, a quadratic integral algorithm is used to solve the strain data into sag values, which has high reliability and stability. Attached Figure Description

[0013] To more clearly illustrate the technical solutions 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of a high-density, ultra-weak grating dynamic sensing array sensor structure.

[0015] Figure 2 This is a schematic diagram illustrating the engineering application of a high-density, ultra-weak grating dynamic sensing array.

[0016] Figure 3 This is a sag curve diagram for OPGW cables.

[0017] Figure 4 This is a dynamic strain response curve.

[0018] Figure 5This is a schematic diagram of a high-density, ultra-weak grating dynamic sensing array combined with a smart junction box. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] This invention discloses a high-density ultra-weak grating dynamic sensing array sensor for OPGW and smart junction boxes, such as... Figure 1 As shown, it includes: optical fiber 1, with a grating array 2 etched on the optical fiber 1 having several periods; the optical fiber is sequentially covered with a graded refractive index cladding 3, a mechanical reinforcement layer 4, and an outer sheath 5. The optical fiber is a G.652D single-mode fiber with a mode field diameter of 9.2 μm and a cutoff wavelength of 1260 nm, exhibiting excellent low-loss and high-bandwidth characteristics, making it suitable for long-distance sensing applications.

[0021] Furthermore, grating array 2 comprises 5 gratings. Specifically, ultra-weak gratings are written into G.652 fiber using a femtosecond laser or ultraviolet mask exposure, with a scanning speed of 0.5 mm / s and 5 gratings written per cycle. The femtosecond laser processing system uses a laser with a wavelength of 1030 nm, a pulse width of 290 fs, and a repetition frequency of 250 kHz for high-precision direct writing of grating 2.

[0022] The specific writing process is as follows: G.652 fiber 1 is fixed on a three-dimensional translation stage, and the laser is focused to a depth of 15μm outside the fiber core (error ±3μm) to ensure accurate grating writing position. Laser parameters are set as follows: pulse energy 1.0μJ±0.2μJ, scanning speed 0.5mm / s, and 5 gratings 2 (20cm spacing) are written per cycle. The wavelength interval between adjacent gratings is ≥0.8nm by adjusting the grating period Λ=530-535nm. The grating reflectivity is controlled to -55dB±5dB to ensure good reflectivity and low crosstalk in the high-density array.

[0023] After the inscription is completed, the optical fiber undergoes performance testing, which includes: Grating performance testing: The survival rate of the grating was detected using an optical time-domain reflectometer: Under a tensile force of 1.8 GPa, the survival rate of the grating reached 99.3%, verifying the stability of the grating under high stress conditions.

[0024] Wavelength stability test: Cycled 100 times within a temperature range of -40℃ to 80℃, wavelength drift is less than 5pm, ensuring the wavelength stability of the grating under extreme temperature conditions.

[0025] Specifically, the graded refractive index cladding 3 is made of graded refractive index polyurethane material and is extruded onto the outer surface of optical fiber 1 using an extruder (45mm screw diameter). The graded refractive index polyurethane cladding has a refractive index gradient of 0.02 / mm and a Shore hardness of 85A, providing excellent bending and aging resistance. Furthermore, the refractive index distribution is controlled to... (r is the radial distance in mm), with a thickness of 1.2 mm ± 0.1 mm, ensuring low-loss transmission of the optical cable under bending and stretching conditions.

[0026] Furthermore, the mechanical reinforcement layer 4 is made of a mixture of borosilicate glass fiber and epoxy resin, and is coated on the outside of the gradient refractive index cladding layer 3 through a two-layer gradient curing process. Specifically, borosilicate glass fiber and epoxy resin are mixed at a volume ratio of 7:3, pre-impregnated, and then wrapped around the outside of the cladding layer 3 to form the mechanical reinforcement layer 4. The specific parameters of the two-layer gradient curing process are: the UV intensity of the first layer is 20mW / cm² (baked at 80℃ for 10 minutes), and the second layer is increased to 50mW / cm² (baked at 120℃ for 15 minutes), ensuring uniform curing and high mechanical strength of the reinforcement layer.

[0027] Furthermore, the outer sheath 5 is made of high molecular polymer material (polyolefin, high-density polyethylene, etc.) and is extruded over the mechanical reinforcement layer 4.

[0028] On the other hand, the present invention provides an OPGW sag monitoring method, utilizing the above-mentioned high-density ultra-weak grating dynamic sensing array sensor for OPGW and smart junction boxes, comprising the following steps: like Figure 2 As shown, the high-density ultra-weak grating dynamic sensing array sensor is connected to the demodulation system 8. The high-density ultra-weak grating dynamic sensing array sensor is used to sense the wavelength information of the OPGW in real time, and the wavelength information is transmitted to the demodulation system for processing to obtain data. The strain transfer compensation algorithm is used, and the compensation coefficient is dynamically adjusted based on the real-time monitored wavelength data through a Kalman filter; The collected wavelength data is compensated in real time based on the dynamically adjusted compensation coefficient. The compensated wavelength data is processed using a quadratic integral algorithm to calculate the sag value of the OPGW, such as... Figure 3 As shown.

[0029] Specifically, the compensated strain data is processed using a quadratic integral algorithm to calculate the sag value of the OPGW, including: Calculate a certain moment based on the wavelength data. t Dependent variables: ; in, For the i-th sensing grating point acquired by demodulation system 8 t Wavelength change at time, strain sensitivity , The unit is strain, and pm is the unit of wavelength. Calculate the dynamic acceleration based on the strain: ; Where g is the acceleration due to gravity, E is Young's modulus, and m is the linear density. This refers to the local tilt angle of the conductor; The displacement is obtained by performing a second integral on the dynamic acceleration: speed ; Sag change ; Where Δt is the time step, k is the kth time interval, and n is the total number of time intervals, satisfying the following relationship: ; Superimpose the sag change onto the initial sag To obtain real-time sag .

[0030] Through the above embodiments, a high-density grating sensing array for UHV lines achieves high spatial resolution (20cm), high precision (strain resolution ±5με), and real-time dynamic monitoring capabilities, solving the problems of insufficient spatial resolution, temperature cross-sensitivity, and poor real-time performance of traditional BOTDR technology. It is suitable for UHV line sag monitoring in complex environments. This invention achieves strain measurement deviation <0.8% and sag measurement error <2% under ±45° torsional conditions; a sensor point density of 5 points / m achieves a maximum spatial resolution of 0.2m; and a sampling frequency >1Hz, enabling real-time monitoring under complex conditions of low-frequency galloping. Under simulated strong wind and galloping conditions, the system response time is <5 seconds. Figure 4 As shown, it basically meets the real-time monitoring requirements.

[0031] In addition to the examples described above, when using smart junction boxes in OPGW lines, the fiber optic cable tray of the junction box can be seamlessly connected, such as... Figure 5 As shown, this serves as an additional monitoring module to expand the monitoring indicators of the smart junction box.

[0032] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0033] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-density ultra-weak grating dynamic sensing array sensor for OPGW and smart junction boxes, characterized in that, include: Optical fiber (1), on which a number of periodic grating arrays (2) are etched; the optical fiber is sequentially covered with a graded refractive index cladding (3), a mechanical reinforcement layer (4), and an outer sheath (5).

2. The high-density ultra-weak grating dynamic sensing array sensor for OPGW and smart junction boxes according to claim 1, characterized in that, The grating array (2) includes 5 gratings.

3. A high-density ultra-weak grating dynamic sensing array sensor for OPGW and smart junction boxes according to claim 1, characterized in that, The gradient refractive index cladding (3) is made of self-made gradient refractive index polyurethane material and is wrapped around the optical fiber (1) by an extruder.

4. A high-density ultra-weak grating dynamic sensing array sensor for OPGW and smart junction boxes according to claim 1, characterized in that, The mechanical reinforcement layer (4) is made of a mixture of borosilicate glass fiber and epoxy resin, and is coated on the outside of the gradient refractive index cladding layer (3) by a double-layer gradient curing process.

5. A high-density ultra-weak grating dynamic sensing array sensor for OPGW and smart junction boxes according to claim 1, characterized in that, The outer sheath (5) is made of a polymer material and is extruded over the mechanical reinforcement layer (4).

6. A method for monitoring the sag of OPGW, characterized in that, The high-density ultra-weak grating dynamic sensing array sensor for OPGW and smart junction boxes as described in any one of claims 1-5 includes the following steps: The high-density ultra-weak grating dynamic sensing array sensor is connected to the demodulation system (8). The high-density ultra-weak grating dynamic sensing array sensor is used to sense the wavelength information of the OPGW in real time, and the wavelength information is transmitted to the demodulation system for processing to obtain data. The strain transfer compensation algorithm is used, and the compensation coefficient is dynamically adjusted based on the real-time monitored wavelength data through a Kalman filter; The collected wavelength data is compensated in real time based on the dynamically adjusted compensation coefficient. The compensated wavelength data is processed using a quadratic integral algorithm to calculate the sag value of the OPGW.

7. The OPGW sag monitoring method according to claim 6, characterized in that, The compensated strain data is processed using a quadratic integral algorithm to calculate the sag value of the OPGW, including: Calculate a certain moment based on the wavelength data. t Dependent variables: ； in For the demodulation system (8), the i-th sensing grating point is acquired in t The change in wavelength at any given time. For strain sensitivity; Calculate the dynamic acceleration based on the strain: ； Where g is the acceleration due to gravity, E is Young's modulus, and m is the linear density. This refers to the local tilt angle of the conductor; The displacement is obtained by performing a second integral on the dynamic acceleration: speed ; Sag change ; Where Δt is the time step, k is the kth time interval, and n is the total number of time intervals, satisfying the following relationship: ; Superimpose the sag change onto the initial sag To obtain real-time sag .

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