Functional film transfer method and packaging structure of Fabry-Perot optical sensor for measuring hydrogen content based on cavity length change

Abstract

The invention relates to a functional film transfer method and a packaging structure of a Fabry-Perot optical sensor for measuring hydrogen content based on cavity length change, belongs to the field of optical sensing, and comprises a functional film transfer method and a sensor packaging method. According to the invention, the polymethyl methacrylate is used for transferring the functional film, so that the problem that the functional film is difficult to transfer is solved; a ceramic ferrule packaging method is designed, and the problems that a probe is easy to damage and a functional film is easy to fall off are solved by packaging a manufactured sensor probe into a ferrule; aiming at the sensitivity problem of the hydrogen sensor, multilayer graphene is used as a base material of a diaphragm, and palladium alloy is attached to a graphene film to form a functional film, so that the sensitivity of the sensor is increased, and the resolution ratio of the sensor to different hydrogen concentrations is improved.

Description

Technical Field

[0001] The invention relates to a functional film transfer method and a packaging structure of a Fabry-Perot optical sensor for measuring hydrogen content based on cavity length change, and belongs to the field of optical sensing. Background Art

[0002] As the operation hub equipment of power transmission and distribution in the power system, the transformer is one of the most important components of the power system. Once a fault occurs, it will pose a great threat to the stable operation of the power system and social production. In the long-term operation of the transformer, partial discharge, oil fault, arc discharge, overheating or other complex faults may occur, which will cause the cracking of the insulating material in the transformer oil and produce characteristic gases such as CH4, C2H2, H2, CO, CO2, etc. These gases are dissolved in the insulating oil. By analyzing the composition and proportion of the dissolved gas in the oil, the type, severity and development trend of the latent fault can be judged in time. The analysis of dissolved gas in oil is one of the most efficient methods to identify potential faults of transformers, and in the process of detecting the status of the transformer, it will not affect the normal working state of the transformer. Therefore, the safe and stable operation state of the transformer is of far-reaching significance for ensuring the safety of the power grid. Realizing online detection of hydrogen can make the operation of the power system safer and more reliable.

[0003] The detection of hydrogen content in transformer oil is an important part of transformer fault diagnosis. At present, there are two main types of optical sensors for online detection of transformer hydrogen content. The first is the evanescent field type fiber evanescent field hydrogen sensor, which usually attaches a palladium film to the surface of the optical fiber. When hydrogen reacts with the palladium film, the change in the intensity of the evanescent field of the optical fiber coupled to the palladium film can be detected; the second is the fiber grating sensor. The hydrogen sensor based on the fiber grating monitors the central wavelength deviation of the reflected Bragg spectrum, thereby monitoring the hydrogen concentration in the environment where the fiber grating is located.

[0004] Transformer gas protection technology (Gas-Relay Protection) is a protection technology based on the change of gas concentration in the transformer oil tank, which is widely used in the protection and monitoring of transformers in power systems. Gas protection technology mainly detects the gas in the oil inside the transformer, especially the type and concentration change of the gas, to determine whether the transformer has internal faults, such as partial discharge, overheating, short circuit, etc. Gas protection is a very effective means of early fault diagnosis. It can detect potential problems of the transformer in time, thereby avoiding serious accidents.

[0005] For the dissolved gas analysis technology (DGA), it is necessary to take transformer oil samples from the oil tapping port, degas them, and analyze the components of the generated gas. The detection time is long, and it is difficult to quickly and timely respond to abnormal conditions in the transformer. In addition, it is impossible to monitor the specific location of the fault.

[0006] Traditional electrical hydrogen sensors may generate sparks during operation. Considering the high flammability of hydrogen, this increases the safety risk when using these sensors and safety cannot be guaranteed. New optical sensors generally have problems such as low mechanical strength of sensor probes, difficulty in transferring functional membranes, and the demodulation instruments require expensive instruments such as broadband light sources and broadband oscilloscopes.

[0007] To solve the above problems, the present invention proposes a functional film transfer method and packaging structure of a Fabry-Perot optical sensor for measuring hydrogen content based on cavity length change, and uses polymethyl methacrylate (PMMA) to transfer the functional film, thereby solving the problem of difficulty in transferring the functional film; a ceramic ferrule packaging method is designed, and the problem of easy damage to the probe and easy falling off of the functional film is solved by packaging the manufactured sensor probe into the ferrule; in response to the sensitivity problem of the hydrogen sensor, multilayer graphene is used as the basic material of the diaphragm, and palladium alloy is attached to the graphene film to form a functional film, so that the sensitivity of the sensor is increased, and the resolution of the sensor for different hydrogen concentrations is improved. Summary of the invention

[0008] The present invention proposes a functional film transfer method of a Fabry-Perot optical sensor for measuring hydrogen content based on cavity length change and its packaging structure, which comprises two parts: a functional film transfer method and a sensor packaging method.

[0009] Figure 1 A schematic diagram of a method for transferring a functional film based on copper-based deposition coating and using PMMA provided by the present invention; Figure 2 A schematic diagram of a sensor probe packaging method based on a ceramic ferrule provided by the present invention.

[0010] Figure 1 The functional film transfer method is shown in the figure, which includes single-mode optical fiber 101, hollow-core optical fiber 102, PMMA 103, multilayer graphene film 104, palladium alloy 105, and copper base 106. The sensor probe packaging method based on ceramic ferrule is as follows Figure 2As shown, it includes 201 functional film, 202 hollow core optical fiber, 203 ceramic ferrule, 204 single mode optical fiber and 205 ultraviolet glue. The preparation and transfer process of the functional film is as follows: the single mode optical fiber 101 and the hollow core optical fiber 102 are fused together at their end faces by a fusion splicer to form a pure quartz probe. Then, magnetron sputtering and physical deposition are used on the copper base 106 to attach the palladium alloy functional film 105 and the multilayer graphene film 104 to the copper base 106. The thickness of graphene is optimal at about 30. Compared with the quartz diaphragms in other patents, the sensitivity of the sensor is greatly improved while ensuring that the diaphragm will not break. In the process of making the palladium alloy functional film, a layer of silver is deposited on the side of the palladium alloy that is biased towards graphene. Silver can increase the absorption rate of hydrogen and reduce the hydrogen embrittlement problem of palladium metal. Finally, PMMA is spin-coated on the multilayer graphene film 104, and then the probe composed of the single-mode optical fiber 101 and the hollow-core optical fiber 102 is picked up by hand and vertically bonded to the functional film. After heating and drying, PMMA can be firmly bonded to the hollow-core optical fiber 102 made of quartz. After bonding with PMMA, the copper base 106 at the port of the sensor probe is placed in the FeCl3 solution, and the copper base is corroded. After air drying, a complete hydrogen sensor probe can be obtained.

[0012] The sensor probe packaging method based on the ceramic ferrule is as follows Figure 2 First, before the functional film is transferred and the probe is made, a ceramic ferrule 203 with an inner diameter of 126 is inserted from the head of the single-mode optical fiber 204, and then Figure 1 The method described above sequentially fuses the hollow core optical fiber 202 onto the single mode optical fiber 204 and transfers the functional film. After completing the above steps, the sensor probe composed of the functional film 201, the hollow core optical fiber 202 and the single mode optical fiber 204 needs to be pulled by a micro-motion platform until it is completely retracted into the ceramic ferrule 203. The distance that the functional film 201 of the probe is retracted into the ferrule 203 is about 100. If this distance is too short, the functional film will be affected by the oil flow in the transformer and will not achieve the protective effect; if the distance is too long, the hydrogen diffusion time will be longer, affecting the response time of the sensor.

[0013] The optical fiber fixing method is as follows Figure 3 After the sensor probe is retracted, the bottom of the ceramic ferrule is sealed with ultraviolet glue 301 to fix the position of the sensor probe in the ceramic ferrule 203 and prevent the sensor from being damaged due to slipping in subsequent use. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of a method for copper-based deposition coating and functional film transfer using PMMA.

[0015] Figure 2A schematic diagram of a sensor probe packaging method based on a ceramic ferrule.

[0016] Figure 3 Schematic diagram of the packaged hydrogen sensor. Specific implementation plan The embodiments are described in detail below in conjunction with the accompanying drawings.

[0017] In order to more clearly explain the objectives, technical solutions and advantages of this patent application, the following content will describe this application in detail with reference to the accompanying drawings and examples. It should be noted that the embodiments described herein are only used to explain the contents of this application and do not constitute any limitation to this application. Any other implementation methods obtained by any person skilled in the art according to this application without performing creative work shall be deemed as the scope of protection covered by this application.

[0018] The drawings mentioned in the patent only show some examples or implementations of the present patent application. For those of ordinary skill in the art, they can apply the principles of the present application to other similar situations based on these drawings without performing creative work. At the same time, it should also be recognized that although complex efforts may be required during the development process, for those of ordinary skill in the art, the adjustments and changes in design, manufacturing or production based on the technical content disclosed in the present application are merely routine technical operations and should not be regarded as incompleteness of the disclosure of the present application.

[0019] Figure 1 Schematic diagram of a method for copper-based deposition coating and functional film transfer using PMMA. Figure 2 A schematic diagram of a sensor probe packaging method based on a ceramic ferrule. Figure 3 Schematic diagram of the packaged hydrogen sensor.

[0020] Example 1: Figure 1 The figure shows a schematic diagram of a method for correcting infrared temperature measurement images of a transformer tank wall based on a point temperature sensor array, and provides a method for manufacturing a cavity of the present invention. The single-mode optical fiber 101 and the hollow-core optical fiber 102 are fused together at their ends by a fusion splicer to form a pure quartz probe. Then, the palladium alloy functional film 105 and the multilayer graphene film 104 are attached to the copper base 106 by magnetron sputtering and physical deposition.

[0020] The functional film transfer method and processing details are as follows: spin-coat PMMA on the multilayer graphene film 104, then pick up the probe composed of the single-mode optical fiber 101 and the hollow-core optical fiber 102 by hand, and vertically bond it to the functional film. After heating and drying, PMMA can be firmly bonded to the hollow-core optical fiber 102 made of quartz. After bonding with PMMA, put the copper base 106 at the sensor probe port into the FeCl3 solution, wait for the copper base to corrode, and then air-dry to obtain a complete hydrogen sensor probe.

[0021] Example 2: Figure 2 The figure shows a schematic diagram of a sensor probe packaging method based on a ceramic ferrule, which provides the functional membrane transfer part of the present invention. The functional membrane transfer and its subsequent protection measures are as follows: First, before the functional membrane transfer and probe production, a ceramic ferrule 203 with an inner diameter of 126 is inserted from the head of the single-mode optical fiber 204, and then the ceramic ferrule 203 with an inner diameter of 126 is used. Figure 1 The method described above sequentially fuses the hollow core fiber 202 to the single mode fiber 204 and transfers the functional film. After completing the above steps, the sensor probe composed of the functional film 201, the hollow core fiber 202 and the single mode fiber 204 needs to be pulled by a micro-motion platform until it is completely retracted into the ceramic ferrule 203. The distance that the functional film 201 of the probe is retracted into the ferrule 203 is about 100.

Claims

1. The present invention relates to a functional film transfer method and packaging structure of a Fabry-Perot optical sensor for measuring hydrogen content based on cavity length change, which includes two key technologies: a functional film transfer method and a sensor packaging method.

2. The method for transferring a functional film of a Fabry-Perot optical sensor for measuring hydrogen content based on cavity length change according to claim 1, characterized in that: Preparation and transfer process of functional film. The single-mode optical fiber and the hollow-core optical fiber are fused together at their ends using a fusion splicer to form a pure quartz probe. Then, magnetron sputtering and physical deposition are used on the copper substrate to attach the palladium alloy functional film and the multilayer graphene film 104 to the copper substrate. In this way, compared with the quartz diaphragms in other patents, the sensitivity of the sensor is greatly improved while ensuring that the diaphragm will not break.

3. The functional film packaging preparation of a Fabry-Perot optical sensor for measuring hydrogen content based on cavity length change according to claim 1 is characterized in that: The packaging method of the sensor diaphragm is as follows: insert a ceramic ferrule with an inner diameter of 100 mm from the head of the single-mode optical fiber, and after the sensor end is completed, it will be packaged with UV glue. In this way, the sensor and its packaging part occupy a small volume, have a smooth surface and are non-conductive, and are suitable for the internal environment of the transformer.

4. The functional film transfer scheme of a Fabry-Perot optical sensor for measuring hydrogen content based on cavity length change according to claim 1, characterized in that: The transfer method of the sensor membrane is as follows: spin-coat PMMA on the multi-layer graphene film, then pick up the probe composed of single-mode optical fiber and hollow-core optical fiber by hand, and vertically bond it to the functional film. After heating and drying, PMMA can be firmly bonded to the hollow-core optical fiber made of quartz. After bonding with PMMA, put the copper base of the sensor probe port into the FeCl3 solution, wait for the copper base to corrode, and air-dry to obtain a complete hydrogen sensor probe.

5. The functional film packaging structure of a Fabry-Perot optical sensor for measuring hydrogen content based on cavity length change according to claim 1, characterized in that: The packaging method of the sensor diaphragm is as follows: After the sensor diaphragm is transferred, the sensor probe composed of the functional membrane, hollow-core optical fiber and single-mode optical fiber needs to be pulled by a micro-motion platform until it is completely retracted into the ceramic ferrule. The distance of the functional membrane of the probe retracting into the ferrule is about. If this distance is too short, the functional membrane will be affected by the oil flow in the transformer and will not be able to achieve the protective effect; if the distance is too long, the hydrogen diffusion time will be longer, affecting the response time of the sensor. In this way, the reliability and sensitivity of the hydrogen sensor can be greatly guaranteed.

6. The film composition selection of the cross-section coating technology of the dissolved hydrogen in oil sensor device based on V-cut optical fiber FBG according to claim 1 is characterized in that: The palladium alloy film composition of the functional film of the Fabry-Perot optical sensor for measuring hydrogen content based on cavity length change is selected as follows: Palladium (Pd) has a specific absorption effect on hydrogen, and it will expand when absorbing hydrogen. Acting on the gate area of ​​FBG can change the interference wavelength of the optical signal, and then measure the hydrogen concentration. Gold (Au) can enhance the corrosion resistance and stability of palladium, and can form a lattice with palladium at the atomic level to increase the speed of palladium absorbing hydrogen. Nickel (Ni) and titanium (Ti) can be used to make memory alloys to improve the repeatability of palladium absorbing and releasing hydrogen. The content ratio of each metal is palladium: gold: nickel: titanium = 50%: 30%: 10%: 10%.

7. The method for selecting the thickness of the functional film of a Fabry-Perot optical sensor for measuring hydrogen content based on cavity length change according to claim 1, characterized in that: The thickness of the graphene film of the Fabry-Perot optical sensor is selected as follows: the graphene film serves as the main conversion membrane between gas concentration and optical signals, and as the substrate of the functional membrane components, its thickness affects the reliability, sensitivity and resonant frequency of the entire membrane. The present invention has determined that the optimal thickness of graphene is around 30nm.

8. The packaging of the Fabry-Perot optical sensor for measuring hydrogen content based on cavity length change and the fixing method of the sensor itself according to claim 1 is characterized in that: The optical fiber fixing method of the Fabry-Perot optical sensor is as follows: after the sensor probe is retracted, the bottom of the ceramic ferrule is sealed with ultraviolet glue. According to this method, when performing the fixing operation of the sensor probe, the sensor probe can be simply and quickly fixed in the ceramic ferrule, thereby preventing damage to the sensor caused by slipping during subsequent use, or a decrease in sensitivity caused by slipping.

9. The functional film composition of a Fabry-Perot optical sensor for measuring hydrogen content based on cavity length change according to claim 1, characterized in that: The transition layer of the Fabry-Perot optical sensor is selected as follows: in the process of making the palladium alloy functional film, before plating the palladium alloy, a layer of silver is deposited on the side biased towards the graphene. Silver can increase the absorption rate of hydrogen and alleviate the hydrogen embrittlement problem of palladium metal.

10. The composition of the membrane intermediate layer of the Fabry-Perot optical sensor for measuring hydrogen content based on cavity length change according to claim 1, characterized in that: The middle layer of the Fabry-Perot optical sensor is selected as follows: PMMA is spin-coated on the multi-layer graphene film, and then the probe composed of the single-mode optical fiber and the hollow-core optical fiber is picked up by hand and vertically bonded to the functional film. After heating and drying, the PMMA can be firmly bonded to the hollow-core optical fiber made of quartz. The PMMA material used in this operation will automatically dissolve at high temperatures, so that the graphene membrane itself can be more firmly bonded to the optical fiber cavity.

Images