High-voltage cable buffer layer online monitoring method and system based on hydrogen sensitive probe

Abstract

The invention discloses a high-voltage cable buffer layer on-line monitoring method and system based on a hydrogen sensitive probe, and the method comprises the steps: forming a sensitive film layer with a response characteristic to hydrogen on the surface of an optical fiber, arranging a hydrogen sensitive optical fiber in a high-voltage cable buffer layer region, injecting an optical signal into the optical fiber, and carrying out the detection of the hydrogen sensitive optical fiber. And collecting an optical response signal generated in the propagation process of the optical signal in the optical fiber, analyzing the optical response signal, and judging the operation state of the buffer layer according to the optical parameter change caused by the hydrogen action. The system comprises a sensing unit, a signal acquisition unit and a data processing unit, all the units work cooperatively, and online monitoring and abnormity positioning of the early degradation state of the high-voltage cable buffer layer are achieved. The device can stably operate in a strong electromagnetic environment, and is suitable for continuous monitoring and state evaluation of the high-voltage cable buffer layer.

Description

Technical Field

[0001] This invention relates to the field of high-voltage cable condition monitoring technology, specifically to a method and system for online monitoring of high-voltage cable buffer layers based on hydrogen-sensitive probes. Background Technology

[0002] High-voltage cables are crucial equipment for power transmission in power systems, and their operational safety and reliability directly affect the stable operation of the power grid. During long-term operation, the cable insulation structure may age, experience partial discharge, or chemical degradation due to the combined effects of electric fields, thermal fields, and environmental factors. Among these factors, the buffer layer, as a vital functional layer connecting the insulation layer and the metal sheath, has a significant impact on the overall lifespan of the cable.

[0003] Existing research indicates that trace amounts of gas, particularly hydrogen, are often generated during the early stages of cable insulation or buffer layer degradation. Hydrogen, with its small molecular size and strong diffusion capacity, can appear early within the cable structure, and its concentration changes can serve as an important early warning signal reflecting the degradation state of the buffer layer and insulation materials. Therefore, real-time monitoring of hydrogen generation and distribution in the buffer layer of high-voltage cables is crucial for early fault warning and condition assessment.

[0004] Currently, monitoring methods for cable operation mainly include partial discharge detection, temperature monitoring, dielectric loss measurement, and comprehensive online monitoring methods based on electrical parameters. These methods primarily focus on monitoring the overall operating status or electrical characteristics of the cable, and are difficult to directly reflect gas changes within the buffer layer. Furthermore, some gas detection schemes typically rely on electrochemical sensors or semiconductor gas-sensitive elements, which have limited long-term stability and anti-interference capabilities under high voltage and strong electromagnetic environments, and are difficult to implement for continuous distributed monitoring along the cable length.

[0005] With the development of fiber optic sensing technology, fiber optics, due to their strong resistance to electromagnetic interference and suitability for long-distance deployment, have been gradually introduced into the field of power equipment condition monitoring. However, existing fiber optic monitoring technologies are mostly focused on detecting physical quantities such as temperature and strain, lacking the ability to directly sense chemical information such as hydrogen gas inside the buffer layer. Furthermore, some monitoring schemes can only achieve point-based detection, making it difficult to balance monitoring accuracy and positioning capabilities, thus failing to meet the needs for continuous online monitoring and precise positioning of buffer layers in long-distance high-voltage cables. Therefore, there is an urgent need for a monitoring method and system that can adapt to the operating environment of high-voltage cables, has a high sensitivity to changes in hydrogen gas in the buffer layer, and combines online monitoring and positioning functions, in order to effectively perceive and assess the early deterioration state of high-voltage cable buffer layers. Summary of the Invention

[0006] The purpose of this invention is to provide an online monitoring method and system for high-voltage cable buffer layers based on hydrogen-sensitive probes, so as to solve the problems mentioned in the background art.

[0007] To address the aforementioned technical problems, this invention provides the following technical solution: an online monitoring method for high-voltage cable buffer layers based on a hydrogen-sensitive probe, comprising the following steps: S1. A sensitive film layer with hydrogen-responsive characteristics is formed on the surface of an optical fiber to obtain a hydrogen-sensitive optical fiber, and the hydrogen-sensitive optical fiber is arranged in the buffer layer area of ​​a high-voltage cable. S2. Inject an optical signal into the hydrogen-sensitive optical fiber and collect the optical response signal generated during the propagation of the optical signal in the optical fiber; S3. Analyze the optical response signal and obtain the corresponding change characteristics when hydrogen gas acts on the sensitive film layer and causes changes in optical parameters. S4. Based on the aforementioned change characteristics, determine the operating status of the high-voltage cable buffer layer to achieve online monitoring of the early deterioration state of the buffer layer.

[0008] According to the above technical solution, the hydrogen-sensitive optical fiber is a fiber grating with the sensitive film layer formed on the surface of the fiber grating. When hydrogen gas acts on the sensitive film layer, it causes a change in the reflection center wavelength of the fiber grating.

[0009] According to the above technical solution, in step S4, the reference center wavelength of the fiber optic grating under conditions of no hydrogen or stable hydrogen is obtained, and the real-time acquired center wavelength is compared with the reference center wavelength. The state of the buffer layer is determined based on the drift of the center wavelength.

[0010] According to the above technical solution, the optical response signal is a backscattered light signal distributed along the length direction of the hydrogen-sensitive optical fiber, obtained by optical time-domain reflectometry.

[0011] According to the above technical solution, in step S3, the real-time acquired backscattered light signal is compared with the pre-acquired reference backscattered light signal to obtain a differential signal reflecting the change in the state of the optical fiber.

[0012] According to the above technical solution, the differential signal is subjected to frequency domain processing to suppress noise components and enhance the abnormal characteristics caused by hydrogen.

[0013] According to the above technical solution, when an abnormal feature is detected in the differential signal, the corresponding abnormal position of the buffer layer is determined based on the time information of the abnormal feature in the backscattered light signal.

[0014] According to the above technical solution, the hydrogen-sensitive optical fiber is continuously arranged along the length of the high-voltage cable between the cable's metal sheath and the buffer layer to achieve fully distributed monitoring of the buffer layer.

[0015] The online monitoring system for the buffer layer of a high-voltage cable based on a hydrogen-sensitive probe includes: a sensing unit, including a hydrogen-sensitive optical fiber with a sensitive film layer formed on the surface of the optical fiber that has a hydrogen-responsive characteristic, the hydrogen-sensitive optical fiber being arranged in the buffer layer region of the high-voltage cable. A signal acquisition unit, connected to the sensing unit, is used to inject an optical signal into the hydrogen-sensitive optical fiber and acquire the optical response signal generated during the propagation of the optical signal in the optical fiber. The data processing unit is communicatively connected to the signal acquisition unit and is used to analyze the optical response signal and determine the operating status of the high-voltage cable buffer layer based on the analysis results, so as to realize online monitoring of the early deterioration state of the buffer layer.

[0016] According to the above technical solution, the data processing unit is configured to compare the real-time acquired optical response signal with the pre-acquired reference optical response signal to obtain differential features reflecting the changes in the state of the buffer layer, and to determine the corresponding abnormal position of the buffer layer when the abnormality of the differential features is detected.

[0017] Compared with existing technologies, the beneficial effects achieved by this invention are as follows: This invention, by setting a sensitive film layer on the surface of an optical fiber that responds to hydrogen, and arranging the hydrogen-sensitive optical fiber in the buffer layer region of a high-voltage cable, enables real-time sensing of hydrogen generated during the early degradation process of the buffer layer, thereby achieving front-end monitoring of the buffer layer's condition. By injecting optical signals into the hydrogen-sensitive optical fiber and collecting the resulting optical response signals, the changes in optical parameters reflect the effect of hydrogen, avoiding the problem of traditional electrical sensors being susceptible to interference in high-voltage, strong electromagnetic environments, thus improving the operational stability and reliability of the monitoring system. By analyzing the optical response signals and introducing a benchmark comparison and differential processing mechanism, the abnormal characteristics caused by buffer layer degradation are made more prominent, reducing the impact of background noise on the monitoring results. Simultaneously, by employing a distributed optical fiber arrangement and combining time information for location determination, accurate positioning of abnormal locations in the high-voltage cable buffer layer can be achieved, meeting the application requirements for online monitoring and condition assessment of long-distance cables. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1This is a flowchart illustrating the online monitoring method for high-voltage cable buffer layer based on a hydrogen-sensitive probe in an embodiment of the present invention. Figure 2 This is a schematic diagram of the FBG hydrogen concentration detection sensing system in an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the relationship between the change in the center wavelength of a fiber optic grating and the hydrogen concentration under the influence of hydrogen in an embodiment of the present invention. Figure 4 This is a schematic diagram of the cross-section of an optical fiber in which a palladium-tungsten sensitive film layer is formed on the surface of the optical fiber in an embodiment of the present invention. 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] Example 1: This embodiment aims to explain in detail the specific implementation of the core sensing element used in this invention—the hydrogen-sensitive probe, namely, the fiber grating (FBG) hydrogen concentration detection sensor based on a palladium-based sensitive film.

[0021] Step 1: Fabrication of hydrogen-sensitive fiber optic sensing unit; In this embodiment, a fiber segment on which a fiber grating has been written onto a single-mode communication fiber is selected as the sensing substrate, and the initial Bragg center wavelength of the fiber grating is 1552 nm. To improve the bonding stability between the subsequent sensitive film layer and the fiber surface, the fiber segment is first subjected to surface cleaning and activation treatment.

[0022] Specifically, the fiber segment with the fiber grating inscribed on it is sequentially placed in analytical grade acetone and ethanol solutions for ultrasonic cleaning. The acetone has a purity of not less than 99.5%, and the ethanol has a purity of not less than 99.8%. The ultrasonic cleaning time in each solution is 10 minutes to remove residual oil, organic contaminants, and particulate impurities from the fiber surface. After cleaning, the fiber surface is dried using nitrogen gas.

[0023] For example, the cleaned fiber segment is then placed in a plasma cleaning device for surface activation treatment. The plasma cleaning process uses radio frequency plasma, with a radio frequency power of 100W, and the working gas is a mixture of oxygen and argon in a 1:1 volume ratio. The vacuum level in the cleaning chamber is controlled at 30 Pa, and the processing time is 5 minutes. Through plasma bombardment, the surface energy and the number of active groups on the fiber surface are increased, thereby enhancing the adhesion of the subsequent metal-sensitive film layer to the fiber surface.

[0024] For example, after surface activation treatment, the optical fiber is fixed on the sample stage of the thin film deposition equipment, with the grating region of the fiber optic grating facing the target. Metal film deposition is then performed under a high vacuum condition in the cavity, where the deposition vacuum degree is less than 5 × 10⁻⁻⁻⁴. 4 Pa. A palladium-tungsten alloy target with a tungsten content of 5% was used for magnetron sputtering deposition. By controlling the sputtering time to 50 seconds and the sputtering rate to approximately 2 nm / min, a uniform palladium-tungsten alloy sensitive film was formed on the surface of the fiber grating. During the deposition process, the film thickness was monitored in real time using an ellipsometer to ensure that the film thickness uniformity error was controlled within ±3%.

[0025] For example, after the sensitive film deposition is completed, the coated fiber optic sensor undergoes low-temperature annealing. The annealing process is carried out under a nitrogen protective atmosphere at a temperature of 150°C for 2 hours to eliminate the internal stress generated in the palladium-tungsten alloy sensitive film during deposition, stabilize the film microstructure, and thereby improve the performance consistency and stability of the hydrogen-sensitive fiber optic grating sensing unit during long-term online monitoring.

[0026] Step Two: Setting up the monitoring system and acquiring optical signals; In this embodiment, after the hydrogen-sensitive fiber Bragg grating sensing unit is fabricated, it is connected to a signal acquisition and processing system to construct a monitoring system for optical signal acquisition and demodulation. The signal acquisition and processing system includes a broadband light source, a 1×2 fiber coupler, a tunable Fabry-Perot (FP) filter, a photodetector, and a host computer.

[0027] Specifically, the broadband light source is selected with a wavelength coverage of 1520nm to 1570nm to output a broadband optical signal with a flat spectrum and stable power. The output end of the broadband light source is connected to the other optical paths of the system through the 1×2 fiber optic coupler. One output end of the 1×2 fiber optic coupler is connected to a sensing fiber with a hydrogen-sensitive fiber Bragg grating sensing unit to inject a probe optical signal into the fiber. The other output end of the 1×2 fiber optic coupler serves as a reference optical path for system calibration or monitoring of light source power fluctuations.

[0028] For example, during monitoring, broadband light injected into the sensing fiber undergoes selective reflection at the fiber optic grating. The reflected light signal returns along the fiber and is extracted via the fiber coupler, then fed into the tunable FP filter. The tunable FP filter, acting as a wavelength selection and scanning device, performs high-speed, linear scanning of the reflected light signal, thereby achieving wavelength-by-wavelength resolution of the fiber optic grating's reflection spectrum. The light signal scanned by the tunable FP filter is received by a photodetector and converted into a corresponding electrical signal. This electrical signal is transmitted to a host computer for real-time acquisition and processing. The host computer analyzes the output signal from the photodetector to obtain the reflection spectrum information of each fiber optic grating and its center wavelength variation, providing a data foundation for subsequent hydrogen response determination and state analysis.

[0029] Step 3: Detection of optical response under the action of hydrogen gas; In this embodiment, during system monitoring, when hydrogen gas is generated in the high-voltage cable buffer layer due to local overheating, partial discharge, or material degradation, the hydrogen gas diffuses along the buffer layer and its adjacent structures, entering the area where the hydrogen-sensitive fiber Bragg grating sensing unit is located. When hydrogen molecules contact and act on the metal sensitive film layer formed on the surface of the fiber Bragg grating, the hydrogen gas is adsorbed by the sensitive film layer and reacts, causing changes in the physical properties of the sensitive film layer.

[0030] Specifically, in this embodiment, the sensitive film is a palladium-tungsten alloy thin film. When hydrogen molecules enter the film, they cause a change in the film's lattice structure, resulting in a slight expansion of the film's volume and a change in its equivalent refractive index. This volume change and refractive index change together affect the effective refractive index and periodic parameters of the fiber grating, thereby causing a shift in the reflection center wavelength of the fiber grating relative to its initial state.

[0031] For example, during the monitoring process, the signal acquisition and processing system described in step two continuously scans and analyzes the reflection spectrum of each fiber Bragg grating in real time to obtain the reflection spectrum curves of each fiber Bragg grating at different times. By analyzing the reflection spectrum curves, the reflection center wavelength of each fiber Bragg grating is extracted, and its wavelength data changing over time is recorded in real time, thereby obtaining the fiber Bragg grating center wavelength drift caused by the action of hydrogen.

[0032] Step 4: Wavelength variation analysis and buffer layer status determination; In this embodiment, before the monitoring system is put into online operation, the hydrogen-sensitive fiber Bragg grating sensing unit is calibrated to a reference state. Specifically, under conditions of no hydrogen or a stable background hydrogen concentration, the reflection spectrum of each fiber Bragg grating is continuously acquired by the signal acquisition and processing system. After the change of its reflection center wavelength tends to stabilize, the corresponding stable center wavelength value is determined as the reference wavelength of the fiber Bragg grating and used as a reference value for subsequent online monitoring.

[0033] For example, during online monitoring, the signal acquisition and processing system continuously analyzes the reflection spectrum of each fiber grating in real time to obtain the corresponding real-time center wavelength, and compares the real-time center wavelength with its corresponding reference wavelength to calculate the center wavelength drift of each fiber grating. The center wavelength drift is used to characterize the changes in the hydrogen environment at the location of the fiber grating.

[0034] Furthermore, the operating status of the buffer layer within the monitoring area is determined based on the magnitude of the center wavelength drift and its characteristics over time. When the center wavelength drift of a certain fiber grating exceeds a preset threshold, it is determined that there is an abnormal hydrogen generation phenomenon near the location of the fiber grating, and this location is marked as a potential early degradation area of ​​the high-voltage cable buffer layer, thereby achieving online monitoring and determination of the buffer layer degradation status. The preset threshold and the correspondence between the center wavelength drift and hydrogen concentration can be obtained through calibration and performance verification of the sensing system.

[0035] Step 5: Verify the effect.

[0036] In this embodiment, in order to obtain the correspondence between the center wavelength drift and the hydrogen concentration in step four, and to verify the response characteristics of the hydrogen-sensitive fiber Bragg grating sensing unit and monitoring method to hydrogen, this embodiment verifies the effectiveness of the sensing system. Specifically, the prepared hydrogen-sensitive fiber Bragg grating sensing system is fixedly installed in a sealed, transparent gas chamber with an internal volume of 500 mL and equipped with a gas inlet and a gas outlet. During verification, a standard hydrogen cylinder and a high-purity nitrogen cylinder are used as gas sources. Two high-precision mass flow controllers are used to independently control the flow rates of hydrogen and nitrogen, thereby dynamically mixing them to form hydrogen / nitrogen mixtures with different volume fractions. The mixed gas is introduced into the gas chamber at a constant total flow rate of 500 mL / min to simulate the working environment under different hydrogen concentration conditions.

[0037] For example, in the initial verification phase, the fiber optic pigtail of the sensing system is connected to a fiber Bragg grating demodulator. High-purity nitrogen gas is continuously introduced into the gas chamber for at least 30 minutes until the reflection center wavelength of the fiber Bragg grating stabilizes. The center wavelength value in this stable state is then determined as the reference wavelength of the fiber Bragg grating. Subsequently, hydrogen / nitrogen mixed gases with different volume fractions are sequentially introduced into the gas chamber, with hydrogen fractions of 0.5%, 1.0%, 2.0%, and 4.0%. Under each hydrogen concentration condition, the mixed gas is introduced for approximately 15 minutes until the center wavelength drift of the fiber Bragg grating reaches a stable state, and the corresponding stable center wavelength value is recorded.

[0038] For example, to reduce the impact of measurement noise on the verification results, the raw center wavelength data acquired by the fiber Bragg grating demodulator is subjected to a moving average filter with a filter window of 10 data points. The corresponding center wavelength drift is calculated by comparing the stable center wavelength measured under each operating condition with the reference wavelength. Furthermore, the center wavelength drift is fitted and analyzed with the hydrogen gas integral, yielding the following relationship: Δλ = 5.89C + 1.02; Where Δλ is the center wavelength shift of the fiber grating, and C is the hydrogen gas integral. The correlation coefficient of the fitting results... The value of 0.97 indicates a good linear relationship between the center wavelength shift of the fiber grating and the hydrogen concentration.

[0039] The verification results show that by monitoring the change in the center wavelength of the fiber optic grating, the change characteristics of hydrogen concentration can be effectively reflected, thus verifying the feasibility and effectiveness of the online monitoring and judgment method for the early deterioration state of the high-voltage cable buffer layer based on the center wavelength drift described in step four.

[0040] Example 2: This embodiment provides a distributed positioning and monitoring system that combines optical time-domain reflectometry technology with signal frequency-domain processing algorithms to achieve fully distributed, blind-spot-free monitoring and high-precision positioning of the hydrogen generation location in the buffer layer of high-voltage cables.

[0041] This system is based on the sensing optical fiber prepared in Example 1, which has a hydrogen-sensitive film coated on its surface. By analyzing the changes and time delay characteristics of the backscattered light signal in the optical fiber, it can locate and identify the position of the hydrogen anomaly in the buffer layer. To improve the detection capability and positioning accuracy under weak signal conditions, this embodiment introduces a frequency domain analysis method during signal processing to process the acquired signal and improve the signal-to-noise ratio.

[0042] The distributed positioning monitoring system includes a sensing unit, a signal acquisition unit, and a positioning calculation unit.

[0043] Step 1: Deployment of distributed hydrogen-sensitive optical fibers; In this embodiment, an optical fiber coated with a hydrogen-sensitive film on the surface of a single-mode communication optical fiber is selected as the distributed sensing unit. The hydrogen-sensitive film is a palladium-tungsten alloy thin film, and its preparation method is the same as that described in step one of Embodiment 1. By forming a sensitive film with adsorption and response characteristics to hydrogen on the surface of the optical fiber, the optical fiber can generate an optical response to changes in the hydrogen environment at any position along the fiber.

[0044] For example, the distributed hydrogen-sensitive optical fiber is laid along the length of the high-voltage cable between the cable's metal sheath and the buffer layer, ensuring continuous contact or close coupling between the sensing optical fiber and the buffer layer area. This enables fully distributed sensing of hydrogen generation along the buffer layer. During installation, the sensing optical fiber can be continuously arranged axially according to the cable structure to cover the entire monitoring area and avoid blind spots.

[0045] With the above arrangement, the distributed hydrogen-sensitive optical fiber, as a continuous sensing medium, can respond to the generation of hydrogen at different locations during cable operation, providing a foundation for subsequent signal acquisition, anomaly identification, and location analysis based on optical time-domain reflectometry.

[0046] Step 2: OTDR-based optical signal injection and echo acquisition; In this embodiment, after the distributed hydrogen-sensitive optical fiber is laid, it is connected to an optical time-domain reflectometry (OTDR) device for distributed monitoring of the hydrogen response along the fiber's length. The OTD device injects pulsed light signals into the sensing fiber and receives backscattered light signals generated at various locations during the fiber's propagation.

[0047] For example, the backscattered light signal mainly includes Rayleigh scattering signals caused by the non-uniformity of the optical fiber material. When the pulsed light propagates along the sensing optical fiber, the scattered signals at different locations return to the optical time-domain reflectometry device sequentially according to their propagation delay. By synchronously acquiring the returned backscattered light signals, echo signal distribution data corresponding one-to-one with the fiber length direction can be obtained.

[0048] In one specific embodiment, the optical time-domain reflectometry (OTDR) device can employ a multi-pulse measurement mode to balance spatial resolution and measurement distance. For example, short pulses can be used for high-resolution measurement to improve the ability to identify minute local loss changes; simultaneously, longer pulses can be used to improve the dynamic range of the system and enhance signal strength under long-distance measurement conditions. In this embodiment, the dynamic range of the ODR device can reach over 35 dB, thereby meeting the distributed monitoring requirements for long-distance high-voltage cable lines.

[0049] By acquiring and storing echo signals obtained under different pulse conditions, an echo data sequence along the length of the optical fiber is formed, providing basic data support for subsequent anomaly identification, signal processing, and location analysis based on the characteristics of echo signal changes.

[0050] Step 3: Echo signal processing and anomaly feature enhancement; After obtaining the echo signal distribution data along the fiber length direction as described in step two, the positioning calculation unit processes the echo signal to enhance the abnormal features caused by hydrogen and suppress background noise interference.

[0051] When the system is initialized or the cable is operating normally, the optical time-domain reflectometry device is controlled to perform multiple echo measurements on the distributed hydrogen-sensitive optical fiber, and the measurement results are averaged to obtain a stable backscattering echo curve, which is stored as a reference echo curve to characterize the reference scattering characteristics along the optical fiber under the condition of no hydrogen gas anomaly.

[0052] During online monitoring, real-time echo curves are continuously acquired and compared with reference echo curves to obtain differential echo signals that reflect changes in the optical fiber state, thereby reducing the impact of background factors such as inherent optical fiber attenuation and reflections at fixed connection points on the monitoring results.

[0053] In one specific embodiment, to further improve the anomaly detection capability under weak signal conditions, the differential echo signal is processed in the frequency domain. Specifically, a Fast Fourier Transform (FFT) is performed on the differential echo signal to convert it to the frequency domain. By analyzing and filtering the spectral components, low-frequency noise caused by slowly varying factors such as temperature drift and fiber aging is suppressed, while high-frequency interference caused by system noise and random scattering is also suppressed, thereby retaining the effective frequency components related to local reflection events. Subsequently, an inverse transform is performed on the processed frequency domain signal to restore the enhanced time-domain echo signal.

[0054] The above processing makes the local scattering changes caused by hydrogen gas more prominent in the echo signal, providing a reliable basis for subsequent anomaly detection and location.

[0055] Step 4: Time-domain analysis and determination of buffer layer degradation location; After completing the echo signal enhancement process described in step three, the enhanced time-domain echo signal is analyzed to determine the abnormal reflection event caused by hydrogen and its corresponding location on the optical fiber.

[0056] The positioning calculation unit scans the enhanced echo signal. When it detects a significant change in the echo amplitude at a certain location that exceeds a preset judgment threshold, it determines that there is an abnormal reflection event caused by hydrogen gas at that location and marks the abnormal event as a target to be located.

[0057] In one specific implementation, the positioning calculation unit analyzes the time delay of the abnormal reflection event in the echo signal based on the principle of optical time-domain reflectometry. Then, according to the propagation characteristics of the optical signal in the optical fiber, the time delay is converted into a corresponding physical distance, thereby determining the location of the abnormal event on the optical fiber. This location is then correlated with the laying position of the distributed hydrogen-sensitive optical fiber in the high-voltage cable to determine the specific location where the hydrogen anomaly occurred in the buffer layer.

[0058] In the above implementation, the location corresponding to the abnormal event can be calculated according to the following formula: ; Where c is the speed of light in a vacuum, and Δt is the echo delay corresponding to the anomalous reflection event. The effective refractive index of the sensing fiber.

[0059] Furthermore, in one embodiment, the positioning accuracy is related to the pulse width used by the optical time-domain reflectometry device, and its positioning accuracy can be approximately expressed as: ; Wherein, W is the pulse width of the pulsed optical signal. In this embodiment, by selecting a smaller pulse width, the positioning accuracy of abnormal events can be improved.

[0060] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0061] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for online monitoring of high-voltage cable buffer layers based on hydrogen-sensitive probes, characterized in that, Includes the following steps: S1. A sensitive film layer with hydrogen-responsive characteristics is formed on the surface of an optical fiber to obtain a hydrogen-sensitive optical fiber, and the hydrogen-sensitive optical fiber is arranged in the buffer layer area of ​​a high-voltage cable. S2. Inject an optical signal into the hydrogen-sensitive optical fiber and collect the optical response signal generated during the propagation of the optical signal in the optical fiber; S3. Analyze the optical response signal and obtain the corresponding change characteristics when hydrogen gas acts on the sensitive film layer and causes changes in optical parameters. S4. Based on the aforementioned change characteristics, determine the operating status of the high-voltage cable buffer layer to achieve online monitoring of the early deterioration state of the buffer layer.

2. The online monitoring method for high-voltage cable buffer layer based on hydrogen-sensitive probe according to claim 1, characterized in that, The hydrogen-sensitive optical fiber is a fiber grating with the sensitive film layer formed on the surface of the fiber grating. When hydrogen gas acts on the sensitive film layer, it causes a change in the reflection center wavelength of the fiber grating.

3. The online monitoring method for high-voltage cable buffer layer based on hydrogen-sensitive probe according to claim 2, characterized in that, In step S4, the reference center wavelength of the fiber optic grating under conditions of no hydrogen or stable hydrogen is obtained, and the real-time acquired center wavelength is compared with the reference center wavelength. The state of the buffer layer is determined based on the drift of the center wavelength.

4. The online monitoring method for high-voltage cable buffer layer based on hydrogen-sensitive probe according to claim 1, characterized in that, The optical response signal is a backscattered light signal distributed along the length of the hydrogen-sensitive optical fiber, obtained by optical time-domain reflectometry.

5. The online monitoring method for high-voltage cable buffer layer based on hydrogen-sensitive probe according to claim 4, characterized in that, In step S3, the real-time acquired backscattered light signal is compared with the pre-acquired reference backscattered light signal to obtain a differential signal reflecting the change in the state of the optical fiber.

6. The online monitoring method for high-voltage cable buffer layer based on hydrogen-sensitive probe according to claim 5, characterized in that, The differential signal is processed in the frequency domain to suppress noise components and enhance the anomalous features caused by the action of hydrogen.

7. The online monitoring method for high-voltage cable buffer layer based on hydrogen-sensitive probe according to claim 6, characterized in that, When an abnormal feature is detected in the differential signal, the corresponding abnormal position of the buffer layer is determined based on the time information of the abnormal feature in the backscattered light signal.

8. The online monitoring method for high-voltage cable buffer layer based on hydrogen-sensitive probe according to claim 1, characterized in that, The hydrogen-sensitive optical fiber is continuously arranged along the length of the high-voltage cable between the cable's metal sheath and the buffer layer to achieve fully distributed monitoring of the buffer layer.

9. A high-voltage cable buffer layer online monitoring system based on a hydrogen-sensitive probe, characterized in that, include: The sensing unit includes a hydrogen-sensitive optical fiber with a sensitive film layer formed on the surface of the optical fiber that has a hydrogen-responsive characteristic, and the hydrogen-sensitive optical fiber is arranged in the buffer layer region of the high-voltage cable. A signal acquisition unit, connected to the sensing unit, is used to inject an optical signal into the hydrogen-sensitive optical fiber and acquire the optical response signal generated during the propagation of the optical signal in the optical fiber. The data processing unit is communicatively connected to the signal acquisition unit and is used to analyze the optical response signal and determine the operating status of the high-voltage cable buffer layer based on the analysis results, so as to realize online monitoring of the early deterioration state of the buffer layer.

10. The online monitoring system for high-voltage cable buffer layer based on a hydrogen-sensitive probe according to claim 9, characterized in that, The data processing unit is configured to compare the real-time acquired optical response signal with the pre-acquired reference optical response signal to obtain differential features reflecting changes in the state of the buffer layer, and to determine the corresponding abnormal location of the buffer layer when an abnormality is detected in the differential features.

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