Cable current-carrying capacity real-time backstepping system and method based on optical fiber distributed sensing

Abstract

The invention discloses a cable current-carrying capacity real-time backstepping system and method based on optical fiber distributed sensing. The system comprises a light source module; an optical fiber distributed sensing unit; a data acquisition and preprocessing module; a physical model calculation module; a current-carrying capacity backstepping module; a safety evaluation and early warning module; and a visualization module. According to the invention, through the sensing optical fiber laid close to the cable, the Raman scattering effect is utilized to obtain the temperature distribution data of the whole cable in real time, after preprocessing, the data are input into a physical model calculation module to carry out current-carrying capacity estimation, boundary conditions are iteratively corrected, the maximum allowable current-carrying capacity is reversely deduced, and when the real-time current-carrying capacity exceeds a preset threshold value, three-level early warning response is triggered, so that the real-time early warning is realized. The temperature field, the current-carrying capacity curve and historical data are displayed in real time through the visual module, operation and maintenance decision making is assisted, the cable current-carrying capacity calculation precision and the overload prevention and control capacity under the complex working condition are remarkably improved, and an innovative solution is provided for power grid safe operation and power transmission efficiency optimization.

Description

Technical Field

[0001] This invention belongs to the field of power monitoring technology, specifically relating to a real-time reverse estimation system and method for cable current carrying capacity based on fiber optic distributed sensing. Background Technology

[0002] With the development of smart grids and new energy technologies, the capacity of power systems continues to expand, making the safe operation of cables, as the core transmission carrier, crucial. During transmission, due to conductor resistance and environmental heat dissipation limitations, temperature rise in cables directly affects insulation life. Excessive temperatures can trigger short circuits, fires, and other accidents, threatening grid stability. Traditional monitoring relies on point-based temperature sensors and fixed models, which have significant drawbacks. 1) Point sensors such as thermocouples can only obtain the temperature at a single point, which cannot cover the temperature differences along the cable. Furthermore, they have a slow response under high load and are prone to damaging the insulation during installation. 2) The thermal circuit model based on the IEC standard assumes a uniform environment and ignores dynamic factors such as seasonal changes in soil thermal resistance and cable aging, which leads to deviations in current carrying capacity calculation and makes it difficult to cope with complex operating scenarios.

[0003] Fiber optic distributed temperature sensing (DTS) technology achieves continuous temperature monitoring along cables through the Raman scattering effect, boasting advantages such as meter-level resolution, high accuracy of ±0.5℃, resistance to electromagnetic interference, and long lifespan, and has been widely used in power systems. However, existing solutions only focus on temperature monitoring and have not formed a current-carrying capacity estimation system that combines cable physical characteristics (conductor resistance, insulation thermal resistance) with real-time environmental parameters (soil thermal conductivity, wind speed). Cable current-carrying capacity is affected by multiple factors, including conductor temperature, structural parameters, and environmental conditions. Existing technologies lack dynamic models to convert massive amounts of temperature data into accurate current-carrying capacity, and there are technological gaps in real-time changes in environmental parameters, data feature extraction, and optimization of estimation algorithms. Summary of the Invention

[0004] To address the problems in the prior art, the present invention aims to provide a real-time reverse estimation system and method for cable current carrying capacity based on fiber optic distributed sensing. This system can collect temperature distribution data along the entire length of the cable in real time and, combined with the cable's thermal conductivity and current thermal effects, achieve real-time reverse estimation and safety assessment of the cable's current carrying capacity.

[0005] To achieve the above objectives and technical effects, the technical solution adopted by this invention is as follows: A real-time cable current carrying capacity estimation system based on fiber optic distributed sensing includes: Light source module; Fiber optic distributed sensing unit is used to acquire distributed temperature data along the entire cable line; The data acquisition and preprocessing module is connected to the fiber optic distributed sensing unit and is used to process the data uploaded by the fiber optic distributed sensing unit. The physical model calculation module, connected to the data acquisition and preprocessing module, is used for current carrying capacity estimation. The current carrying capacity reverse calculation module is connected to the physical model calculation module and is used to perform current carrying capacity reverse calculation. The safety assessment and early warning module, connected to the load capacity reverse calculation module, is used to generate a safety level signal based on the deviation between the real-time load capacity and the preset threshold, and to trigger multi-level alarms when the overload risk exceeds the threshold. Visualization module.

[0006] Furthermore, the light source module includes a driving circuit, a wavelength division multiplexing module, a detector, and a signal processing and acquisition module. The signal processing and acquisition module is connected to the driving circuit and the detector, respectively, and the detector is connected to the wavelength division multiplexing module.

[0007] Furthermore, the fiber optic distributed sensing unit includes several sensing optical fibers that are tightly attached to the outer surface of the cable in a spiral winding manner.

[0008] Furthermore, the cable comprises, from the inside out, a conductor, an insulation layer, an inner lining layer, a metal layer, and an outer sheath, with the maximum current carrying capacity of the cable constrained by the maximum heat resistance temperature of the insulation layer.

[0009] This invention also discloses a real-time reverse estimation method for cable current carrying capacity based on fiber optic distributed sensing, which is implemented using the real-time reverse estimation system for cable current carrying capacity based on fiber optic distributed sensing as described above, and includes the following steps: Step 1: System Deployment; Step 2: Real-time temperature data acquisition; Step 3: Data preprocessing; Step 4: Load capacity processing; Step 5: Safety assessment and early warning; Step 6: Results Display and Storage.

[0010] Furthermore, in step 1, the sensing optical fiber is laid close to the conductor along the cable axis, and the light source module, optical fiber distributed sensing unit, data acquisition and preprocessing module, physical model calculation module, current carrying capacity reverse calculation module, safety assessment and early warning module and visualization module are connected according to the connection relationship. The light source module emits a laser of a preset wavelength and sets the initial boundary conditions and initial current value.

[0011] Furthermore, in step 2, the initial temperature-position mapping relationship is calibrated using Raman scattering technology through sensing optical fibers to obtain distributed temperature data for the entire cable.

[0012] Furthermore, in step 3, the distributed temperature data of the entire cable is preprocessed through the data acquisition and preprocessing module, including denoising, outlier removal and interpolation of the temperature data, and extracting the temperature characteristic values ​​of the cable conductor.

[0013] Furthermore, in step 4, the load capacity is estimated through the physical model calculation module, the result is uploaded to the load capacity back-calculation module, the load capacity is back-calculated in real time through the load capacity back-calculation module, and the result is uploaded to the safety assessment and early warning module. Calculate the losses of the cable's insulation layer, inner lining layer, metal layer, and outer sheath. R The calculation formula is: in, l The thickness of the current calculation layer, D The inner diameter of the current calculation layer. p This represents the thermal resistance coefficient of the current calculation layer; Calculate ambient thermal resistance R env The calculation formula is: in, D 整体 The diameter of the cable as a whole. p 环境 The thermal resistivity of the environment; Calculate the Joule heat of the current conductor. Q The calculation formula is: in, R AC For conductor AC resistance, The initial current value is preset. Calculate the theoretical value of fiber optic temperature T t The calculation formula is: in, R C , R i , R m , R j The thermal resistance coefficients of the insulating layer 18, inner lining layer 17, metal layer 16, and outer sheath 15 are respectively. Next, compare with the theoretical temperature T t and measured temperature T 0 and correct the boundary conditions to obtain the actual ambient temperature. T envEnvironmental thermal resistance R env ; Actual ambient temperature to be determined T env Environmental thermal resistance R env Then, the maximum current carrying capacity is obtained by reverse-engineering the maximum current formula: Calculate conductor temperature T c The calculation formula is: Conversely, calculate the maximum allowable current carrying capacity when the conductor temperature does not exceed the allowable temperature of the insulation layer's heat resistance life under the current environmental boundary conditions. I max ,make T c = T max The formula for the maximum current can be derived by reverse calculation: in, T max The maximum temperature that the insulation layer can withstand.

[0014] Furthermore, in step 5, if the real-time load capacity... I real ≥0.8 I max At this point, a Level 1 warning is generated, with a visual load reduction suggestion; if the real-time load rate... I real ≥0.95 I max At this point, a level two warning is issued, generating an automatic load reduction and sending a rate limiting command; if the real-time load... I real ≥ I max This is an emergency response; the load is cut off and the backup line is activated.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention discloses a real-time cable current-carrying capacity estimation system and method based on fiber optic distributed sensing. By using sensing optical fibers closely attached to the cable and utilizing the Raman scattering effect, it acquires real-time temperature distribution data of the entire cable (spatial resolution ≤1m, temperature accuracy ±0.1℃). After preprocessing such as denoising and interpolation, the data is input into a physical model calculation module for current-carrying capacity estimation. Boundary conditions are iteratively corrected, and the maximum allowable current-carrying capacity is estimated. When the real-time current-carrying capacity exceeds a preset threshold, a three-level early warning response is triggered. A visualization module displays the temperature field, current-carrying capacity curve, and historical data in real time to assist in operation and maintenance decisions. This invention overcomes the spatial limitations of traditional point-based monitoring and the calculation bias of static models, significantly improving the accuracy of cable current-carrying capacity calculation and overload prevention capabilities under complex operating conditions, providing an innovative solution for power grid safe operation and transmission efficiency optimization. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the principle of the present invention; Figure 2 This is a schematic diagram showing the positions of the sensing optical fiber and cable of the present invention; Figure 3 This is a schematic diagram of the temperature acquisition process of the present invention; Figure 4 This is a schematic diagram of the cable structure of the present invention; Figure 5 This is a flowchart of the present invention. Detailed Implementation

[0017] The present invention will now be described in detail so that its advantages and features can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0018] The following provides a brief overview of one or more aspects to offer a basic understanding of them. This overview is not an exhaustive summary of all conceived aspects, nor is it intended to identify key or decisive elements of all aspects, nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form to prepare for the more detailed descriptions that follow.

[0019] like Figures 1-5 As shown, this invention discloses a real-time cable current carrying capacity estimation system based on fiber optic distributed sensing, comprising: Light source module 1; The fiber optic distributed sensing unit 2 includes several sensing optical fibers 8 that are tightly attached to the outer surface of the cable 9 in a spiral winding manner, used to acquire temperature distribution data of the entire cable. The winding pitch of the sensing optical fibers 8 can be adjusted accordingly. The data acquisition and preprocessing module 3 is connected to the fiber optic distributed sensing unit 2 and is used to denoise, remove outliers and interpolate the temperature data uploaded by the sensing fiber 8, and extract the temperature characteristic value of the cable conductor. Physical model calculation module 4 estimates current carrying capacity by combining heat transfer equations, current-thermal effect models and environmental impact models. The current carrying capacity reverse calculation module 5 is used to reverse calculate the current carrying capacity by combining the cable geometry, cable material parameters, cable operating current, ambient temperature, heat transfer coefficient, and maximum allowable conductor temperature. The safety assessment and early warning module 6 is used to generate a safety level signal based on the deviation between the real-time load and the preset threshold, and to trigger multi-level alarms when the overload risk exceeds the threshold. Visualization module 7.

[0020] In this invention, the light source module 1 includes a driving circuit 10, a wavelength division multiplexing (WF) module 12, an detector (APD) 13, and a signal processing and acquisition module 14.

[0021] Distributed temperature measurement is based on the spontaneous Raman scattering effect. A high-power, narrow-pulse laser pulse LD 11, driven by a driving circuit 10, is incident on the sensing fiber 8. The laser interacts with the fiber molecules, generating extremely weak backscattered light. This backscattered light has three wavelengths: Rayleigh, anti-Stokes, and Stokes. The anti-Stokes light is temperature-sensitive and serves as the signal light, while the Stokes light is temperature-insensitive and serves as the reference light. The backscattered signal light from the sensing fiber 8 passes through a wavelength division multiplexing (WF) module 12 to isolate the Rayleigh scattering light, allowing the temperature-sensitive anti-Stokes signal light and the temperature-insensitive Stokes reference light to pass through. This light is then received by an amplified detector (APD) 13. The temperature can be calculated based on the intensity ratio of the two light beams. Location is determined using optical time-domain reflectometry (OTDR) technology. The signal processing and acquisition module 14 measures the echo time of the scattered signal to determine the fiber position corresponding to the scattered signal. The signal processing and acquisition module 14 adjusts the driving circuit 10 based on data feedback, forming a closed-loop distributed fiber optic temperature sensing system.

[0022] Cable 9 serves as the main body, carrying the transmission of electricity or electrical signals. From the inside out, the cable includes a conductor 19, an insulation layer 18, an inner liner 17, a metal layer 16, and an outer sheath 15. The maximum current carrying capacity of the cable is constrained by the maximum heat resistance temperature of the insulation layer 18.

[0023] After a high-power, narrow-pulse laser pulse LD 11 is incident on the sensing fiber 7, the fiber-optic distributed sensing unit 1, based on DTS technology, continuously collects temperature data along the entire length of the cable, forming a raw signal transmission chain and inputting it to the data acquisition and preprocessing module 2. The data acquisition and preprocessing module 2 eliminates signal noise, removes outliers, and performs interpolation to extract the temperature characteristic values ​​of the cable conductor. The physical model calculation module 3, combined with the cable material characteristics and environmental parameters, constructs a dynamic thermal balance model to accurately calculate the transient temperature distribution of the cable conductor, providing core input for current carrying capacity estimation. The current carrying capacity estimation module 4, using the conductor temperature threshold as a constraint, estimates the maximum allowable current carrying capacity in real time. The safety assessment and early warning module 5 implements risk classification management and corresponding measures. Finally, the visualization module 6 integrates temperature maps, current carrying capacity curves, and early warning information, supporting real-time monitoring and manual intervention across multiple terminals.

[0024] Current heating effect model: describes the physical process of Joule heating generated in cable conductors due to the flow of current. The core is the energy conversion (electrical energy is converted into heat energy) when current passes through the conductor resistance.

[0025] Heat transfer equation: mainly includes the calculation of the thermal resistance of each layer and the theoretical value of the fiber temperature calculated after integrating the thermal resistance of each layer.

[0026] Environmental impact model: refers to the impact of environmental media on the overall thermal system.

[0027] This invention also discloses a method for real-time back-calculation of cable current carrying capacity based on fiber optic distributed sensing, comprising the following steps: Step 1: Deploy and initially calibrate the sensing fiber optic cables. The sensing fiber 8 is laid close to the conductor 19 along the cable axis, and a laser of a preset wavelength is emitted through the light source module 1 to set the initial boundary conditions (ambient temperature). T env Environmental thermal resistance R env (etc.) and initial current value I 0; Step 2: Real-time temperature data acquisition The sensing fiber 8 uses Raman scattering technology to conventionally calibrate the initial temperature-position mapping relationship and obtain distributed temperature data for the entire cable line. Step 3: Data Preprocessing The temperature data is preprocessed through the data acquisition and preprocessing module 2, including noise reduction, outlier removal and interpolation completion, and the temperature characteristic values ​​of the cable conductor are extracted. Step 4: Load Capacity Processing The load capacity is estimated by the physical model calculation module 3, and the result is uploaded to the load capacity back-calculation module 4. The load capacity is then back-calculated in real time by the load capacity back-calculation module 4, and the result is uploaded to the safety assessment and early warning module 5. Step 5: Perform security assessment and early warning through security assessment and early warning module 5, based on real-time traffic volume and preset thresholds. I max The deviation generates a safety level signal and triggers multi-level alarms when the overload risk exceeds the threshold. Step 6: Results Display and Storage The visualization module 6 displays and stores time-varying curves of temperature field, maximum current carrying capacity and current load current, historical alarm records, and environmental parameter change trends. It intuitively displays overload hotspots and risk trends to assist in operation and maintenance decisions.

[0028] In step 4, the losses of the cable's insulation layer 18, inner lining layer 17, metal layer 16, and outer sheath 15 need to be calculated. R The calculation formula is: in, l The thickness of the current calculation layer, D The inner diameter of the current calculation layer. p This represents the thermal resistance coefficient of the current calculation layer.

[0029] Calculate ambient thermal resistance R env The calculation formula is: in, D 整体 The diameter of the cable as a whole. p 环境 The thermal resistivity of the environment; Calculate the Joule heat of the current conductor. Q The calculation formula is: in, R AC For conductor AC resistance, This is the preset initial current value.

[0030] Calculate the theoretical value of fiber optic temperature T t The calculation formula is: in, R C , R i , R m , R j The thermal resistance coefficients are respectively those of the insulating layer 18, the inner lining layer 17, the metal layer 16, and the outer sheath 15.

[0031] Next, the theoretical temperature needs to be compared. T t and measured temperature T 0 and correct the boundary conditions to obtain the actual ambient temperature. T env Environmental thermal resistance R env .

[0032] Actual ambient temperature to be determined T env Environmental thermal resistance R env Then, the maximum current carrying capacity can be obtained by reverse-engineering the maximum current formula: Calculate conductor temperature T c The calculation formula is: Conversely, calculate the maximum allowable current carrying capacity when the conductor temperature does not exceed the allowable temperature of the insulation layer's heat resistance life under the current environmental boundary conditions. I max .make T c = T max The formula for the maximum current can be derived by reverse calculation: in, T max The maximum temperature that the insulation layer can withstand.

[0033] In step 5, after obtaining the data, traffic monitoring and early warning are performed: If real-time load capacity I real ≥0.8 I max At this point, a Level 1 warning is generated, along with a visual load reduction suggestion; If real-time load capacity I real ≥0.95 I max At this point, a level two warning is issued, generating an automatic load reduction and sending a rate limiting command; If real-time load capacity I real ≥ I max This is an emergency response; the load is cut off and the backup line is activated.

[0034] Any parts or structures not specifically described in this invention can be made using existing technologies or products, and will not be elaborated upon here.

[0035] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A real-time reverse estimation system for cable current carrying capacity based on fiber optic distributed sensing, characterized in that, include: Light source module; Fiber optic distributed sensing unit is used to acquire distributed temperature data along the entire cable line; The data acquisition and preprocessing module is connected to the fiber optic distributed sensing unit and is used to process the data uploaded by the fiber optic distributed sensing unit. The physical model calculation module, connected to the data acquisition and preprocessing module, is used for current carrying capacity estimation. The current carrying capacity reverse calculation module is connected to the physical model calculation module and is used to perform current carrying capacity reverse calculation. The safety assessment and early warning module, connected to the load capacity reverse calculation module, is used to generate a safety level signal based on the deviation between the real-time load capacity and the preset threshold, and to trigger multi-level alarms when the overload risk exceeds the threshold. Visualization module.

2. The real-time reverse estimation system for cable current carrying capacity based on fiber optic distributed sensing according to claim 1, characterized in that, The light source module includes a driving circuit, a wavelength division multiplexing module, a detector, and a signal processing and acquisition module. The signal processing and acquisition module is connected to the driving circuit and the detector, respectively, and the detector is connected to the wavelength division multiplexing module.

3. The real-time reverse estimation system for cable current carrying capacity based on fiber optic distributed sensing according to claim 1, characterized in that, The fiber optic distributed sensing unit includes several sensing optical fibers that are tightly attached to the outer surface of the cable in a spiral winding manner.

4. The real-time reverse estimation system for cable current carrying capacity based on fiber optic distributed sensing according to claim 3, characterized in that, The cable comprises, from the inside out, a conductor, an insulation layer, an inner lining, a metal layer, and an outer sheath. The maximum current carrying capacity of the cable is constrained by the maximum heat resistance temperature of the insulation layer.

5. A method for real-time back-calculation of cable current carrying capacity based on fiber optic distributed sensing, characterized in that, The real-time cable current carrying capacity back-calculation system based on fiber optic distributed sensing, as described in any one of claims 1-4, includes the following steps: Step 1: System Deployment; Step 2: Real-time temperature data acquisition; Step 3: Data preprocessing; Step 4: Load capacity processing; Step 5: Safety assessment and early warning; Step 6: Results Display and Storage.

6. The method for real-time back-calculation of cable current carrying capacity based on fiber optic distributed sensing according to claim 5, characterized in that, In step 1, the sensing optical fiber is laid close to the conductor along the cable axis. The light source module, optical fiber distributed sensing unit, data acquisition and preprocessing module, physical model calculation module, current carrying capacity reverse calculation module, safety assessment and early warning module and visualization module are connected according to the connection relationship. The light source module emits a laser of a preset wavelength and sets the initial boundary conditions and initial current value.

7. The method for real-time back-calculation of cable current carrying capacity based on fiber optic distributed sensing according to claim 5, characterized in that, In step 2, the initial temperature-position mapping relationship is calibrated using Raman scattering technology through sensing optical fibers to obtain distributed temperature data for the entire cable.

8. The method for real-time back-calculation of cable current carrying capacity based on fiber optic distributed sensing according to claim 5, characterized in that, In step 3, the distributed temperature data of the entire cable is preprocessed through the data acquisition and preprocessing module, including denoising, outlier removal and interpolation of the temperature data, and extracting the temperature characteristic values ​​of the cable conductor.

9. The method for real-time back-calculation of cable current carrying capacity based on fiber optic distributed sensing according to claim 5, characterized in that, In step 4, the load capacity is estimated through the physical model calculation module, and the result is uploaded to the load capacity back-calculation module. Then, the load capacity is back-calculated in real time through the load capacity back-calculation module, and the result is uploaded to the security assessment and early warning module. Calculate the losses of the cable's insulation layer, inner lining layer, metal layer, and outer sheath. R The calculation formula is: in, l The thickness of the current calculation layer, D The inner diameter of the current calculation layer. ρ This represents the thermal resistance coefficient of the current calculation layer; Calculate ambient thermal resistance R env The calculation formula is: in, D 整体 The diameter of the cable as a whole. ρ 环境 The thermal resistivity of the environment; Calculate the Joule heat of the current conductor Q The calculation formula is: in, R AC For conductor AC resistance, The initial current value is preset. Calculate the theoretical value of fiber optic temperature T t The calculation formula is: in, R C , R i , R m , R j The thermal resistance coefficients of the insulating layer 18, inner lining layer 17, metal layer 16, and outer sheath 15 are respectively. Next, compare with the theoretical temperature T t and measured temperature T 0 and correct the boundary conditions to obtain the actual ambient temperature. T env Environmental thermal resistance R env ; Actual ambient temperature to be determined T env Environmental thermal resistance R env Then, the maximum current carrying capacity is obtained by reverse-engineering the maximum current formula: Calculate conductor temperature T c The calculation formula is: Conversely, calculate the maximum allowable current carrying capacity when the conductor temperature does not exceed the allowable temperature of the insulation layer's heat resistance life under the current environmental boundary conditions. I max ,make T c = T max The formula for the maximum current can be derived by reverse calculation: in, T max The maximum temperature that the insulation layer can withstand.

10. The method for real-time back-calculation of cable current carrying capacity based on fiber optic distributed sensing according to claim 5, characterized in that, In step 5, if the real-time load capacity... I real ≥0.8 I max At this point, a Level 1 warning is generated, along with a visual load reduction suggestion; If real-time load capacity I real ≥0.95 I max At this point, a level two warning is issued, generating an automatic load reduction and sending a rate limiting command; if the real-time load... I real ≥ I max This is an emergency response; the load is cut off and the backup line is activated.

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