An ultra-high voltage transformer pressure release valve membrane strain online monitoring method and device

Abstract

The application relates to the technical field of online monitoring, and discloses a method and device for monitoring the membrane strain of an ultra-high voltage transformer pressure release valve online, wherein a first light wave signal is obtained through a fiber Fabry-Perot sensor, and a second light wave signal is obtained through a fiber grating temperature sensor; the fiber Fabry-Perot sensor comprises a guide optical fiber and a reflection optical fiber which are aligned in a cantilevered end face mode and are respectively located on the two sides of a pre-groove of the pressure release valve membrane; the guide optical fiber and the reflection optical fiber are both inserted into a hollow glass capillary tube to form a Fabry-Perot cavity; one end of the hollow glass capillary tube is fixedly connected with the pressure release valve membrane, and the other end is slidably connected with the guide optical fiber or the reflection optical fiber; based on the current cavity length of the Fabry-Perot cavity obtained according to the first light wave signal and the current temperature obtained according to the second light wave signal, the cavity length variation of the Fabry-Perot cavity is obtained; and based on the cavity length variation, a strain monitoring result is obtained. The method of the application can accurately measure the strain of the pressure release valve membrane without affecting the normal work of the pressure release valve membrane.

Description

Technical Field

[0001] This invention relates to the field of online monitoring technology, and in particular to a method and device for online monitoring of the strain of a pressure relief valve diaphragm in an ultra-high voltage transformer. Background Technology

[0002] Partial discharge refers to a non-penetrating discharge phenomenon that occurs in certain areas within or on the surface of insulating materials due to uneven electric field distribution. Partial discharge is an unavoidable phenomenon during transformer operation. Ultra-high voltage (UHV) transformers, with their high voltage and large current, have even higher requirements for the insulation performance of materials and are more prone to strong partial discharge. Since UHV transformers are filled with oil, if partial discharge causes an explosion, it will seriously endanger the lives of surrounding personnel and cause huge economic losses.

[0003] To prevent explosions in ultra-high voltage (UHV) transformers, pressure relief valves are installed to release internal pressure. When the internal pressure increases, the diaphragm strains, expanding outwards. When the pressure exceeds the diaphragm's design limit, it ruptures, releasing the internal pressure. By monitoring the strain of the pressure relief valve diaphragm, the internal pressure of the UHV transformer can be directly obtained, thus enabling prediction of explosions. The pressure relief valve diaphragm releases internal pressure through its own deformation. Existing methods for monitoring diaphragm strain involve installing stress sensors. However, stress sensors can affect the diaphragm's deformation, altering its performance and affecting its normal operation.

[0004] Therefore, how to monitor the strain of the pressure relief valve diaphragm without affecting its normal operation has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] This invention provides an online monitoring method and device for the strain of a pressure relief valve diaphragm in an ultra-high voltage transformer, which solves the technical problem of how to monitor the strain of the pressure relief valve diaphragm without affecting its normal operation, and achieves the effect of accurately measuring the strain of the pressure relief valve diaphragm without affecting its normal operation.

[0006] In a first aspect, the present invention provides a method for online monitoring of the strain of a pressure relief valve diaphragm in an ultra-high voltage transformer, the method comprising:

[0007] A first optical wave signal is acquired using a fiber optic Fabry-Perot sensor, and a second optical wave signal is acquired using a fiber optic grating temperature sensor. The fiber optic Fabry-Perot sensor includes an optical fiber assembly with its end faces suspended and aligned, and a hollow glass capillary. The optical fiber assembly includes a guiding fiber and a reflecting fiber. The guiding fiber and the reflecting fiber are located on both sides of a pre-grooved pressure relief valve diaphragm of the UHV transformer to be monitored, and are fixedly connected to the pressure relief valve diaphragm. Both the guiding fiber and the reflecting fiber are inserted into the hollow glass capillary to form a Fabry-Perot cavity on the pressure relief valve diaphragm. One end of the hollow glass capillary is fixedly connected to the pressure relief valve diaphragm, and the other end of the hollow glass capillary is slidably connected to the optical fiber assembly.

[0008] Based on the first optical wave signal, the current cavity length of the Fabry-Perot cavity is obtained, and based on the second optical wave signal, the current temperature of the pressure relief valve diaphragm is obtained.

[0009] Based on the current cavity length and the current temperature, the change in the cavity length of the Fabry-Perot cavity caused by the pressure change inside the UHV transformer to be monitored is obtained.

[0010] Based on the change in cavity length, the strain monitoring results of the pressure relief valve diaphragm are obtained.

[0011] Preferably, the step of obtaining the change in the length of the Fabry-Perot cavity caused by the pressure change inside the UHV transformer to be monitored, based on the current cavity length and the current temperature, includes:

[0012] The optimal operating temperature of the pressure relief valve diaphragm is calibrated to obtain a standard temperature, and the length of the Fabry-Perot cavity of the fiber optic Fabry-Perot sensor is calibrated based on the standard temperature to obtain the original cavity length of the Fabry-Perot cavity.

[0013] The coefficient of thermal expansion of the pressure relief valve diaphragm is calibrated to obtain the calibrated value of the coefficient of thermal expansion of the pressure relief valve diaphragm.

[0014] Based on the current temperature, the standard temperature, and the calibration value of the coefficient of thermal expansion, the change in temperature of the cavity length of the pressure relief valve diaphragm due to the current temperature is obtained.

[0015] Based on the current cavity length, the original cavity length, and the cavity length temperature change, the change in the cavity length of the pressure relief valve diaphragm caused by the internal pressure change of the UHV transformer to be monitored is obtained.

[0016] Preferably, the formula for calculating the change in cavity length is:

[0017] ΔL=L1-L0-(T1-T0)g

[0018] Where ΔL represents the change in the length of the Fabry cavity, L1 represents the current length of the Fabry cavity, L0 represents the original length of the Fabry cavity, T1 represents the current temperature, T0 represents the standard temperature, and g represents the calibrated value of the thermal expansion coefficient of the pressure relief valve diaphragm.

[0019] Preferably, the step of acquiring the first optical wave signal through a fiber optic Fabry-Perot sensor and acquiring the second optical wave signal through a fiber optic grating temperature sensor includes:

[0020] The fiber optic Fabry-Perot sensor, the fiber optic grating temperature sensor, and the signal measuring instrument are connected in series via optical fiber. The first operating wavelength range of the fiber optic Fabry-Perot sensor and the second operating wavelength range of the second fiber optic grating temperature sensor are located at opposite ends of the third operating wavelength range of the signal measuring instrument.

[0021] The signal measuring instrument acquires the first optical wave signal of the fiber optic Fabry-Perot sensor and the second optical wave signal of the fiber optic grating temperature sensor.

[0022] Secondly, the present invention also provides an online monitoring device for the diaphragm strain of a pressure relief valve in an ultra-high voltage transformer, which realizes the above-mentioned online monitoring method for the diaphragm strain of a pressure relief valve in an ultra-high voltage transformer. The device includes: an optical fiber Fabry-Perot sensor, a fiber optic grating temperature sensor, a signal measuring instrument, and a signal processing module.

[0023] The fiber optic Fabry-Perot sensor, the fiber optic grating temperature sensor, and the signal measuring instrument are connected in series via optical fibers.

[0024] The fiber optic Fabry-Perot sensor includes an optical fiber assembly with its end faces suspended and aligned, and a hollow glass capillary. The optical fiber assembly includes a guide fiber and a reflective fiber.

[0025] The guiding optical fiber and the reflecting optical fiber are located on both sides of the pre-grooved slot of the pressure relief valve diaphragm of the UHV transformer to be monitored, and are fixedly connected to the pressure relief valve diaphragm.

[0026] Both the guiding optical fiber and the reflecting optical fiber are inserted into the hollow glass capillary to form a Fabry-Perot cavity on the pressure relief valve diaphragm.

[0027] One end of the hollow glass capillary is fixedly connected to the pressure relief valve diaphragm, and the other end of the hollow glass capillary is slidably connected to the optical fiber assembly.

[0028] The guiding optical fiber is connected to the fiber grating temperature sensor;

[0029] The signal processing module is used to obtain the current cavity length of the Fabry-Perot cavity based on the first optical wave signal, and to obtain the current temperature of the pressure relief valve diaphragm based on the second optical wave signal; to obtain the change in cavity length of the Fabry-Perot cavity caused by the pressure change inside the UHV transformer to be monitored based on the current cavity length and the current temperature; and to obtain the strain monitoring result of the pressure relief valve diaphragm based on the change in cavity length.

[0030] Preferably, the first operating spectral wavelength range of the fiber optic Fabry-Perot sensor and the second operating spectral wavelength range of the fiber optic grating temperature sensor are located at opposite ends of the third operating spectral wavelength range of the signal measuring instrument.

[0031] Preferably, the wavelength range of the third working spectrum is 1510nm-1590nm;

[0032] The first working spectrum wavelength range is between 1510nm and 1580nm;

[0033] The second working spectrum wavelength range is between 1580-1590 nm;

[0034] The original length of the Fabry cavity is 150 μm.

[0035] Preferably, the wavelength range of the third working spectrum is 1528nm-1563nm;

[0036] The first working spectrum wavelength range is between 1533nm and 1563nm;

[0037] The second working spectrum wavelength range is between 1528-1533 nm;

[0038] The original length of the Fabry cavity is 250 μm.

[0039] Preferably, the device includes a plurality of fiber optic Fabry-Perot sensors and a plurality of fiber optic grating temperature sensors, each fiber optic Fabry-Perot sensor being connected across both sides of the pre-grooved diaphragm of the pressure relief valve.

[0040] Preferably, the device includes a first fiber Fabry-Perot sensor and a first fiber grating temperature sensor connected in series via a first optical fiber, and a second fiber Fabry-Perot sensor and a second fiber grating temperature sensor connected in series via a second optical fiber.

[0041] The first fiber optic Fabry-Perot sensor is connected across the two sides of the first pre-grooved slot of the pressure relief valve diaphragm, and the second fiber optic Fabry-Perot sensor is connected across the two sides of the second pre-grooved slot of the pressure relief valve diaphragm.

[0042] The installation directions of the first fiber optic Fabry-Perot sensor and the second fiber optic Fabry-Perot sensor form a 90° angle.

[0043] This application provides a method and apparatus for online monitoring of the diaphragm strain of an ultra-high voltage transformer pressure relief valve. Compared with the prior art, the beneficial effects of the embodiments of this application are as follows:

[0044] This application discloses an online monitoring method for the strain of a pressure relief valve diaphragm in an ultra-high voltage (UHV) transformer. It measures the current temperature of the pressure relief valve diaphragm using a fiber optic grating temperature sensor, calculates the temperature change in the cavity length of the Fabry-Perot cavity on the diaphragm due to temperature variations, and eliminates the influence of ambient temperature on the diaphragm strain. This method achieves higher measurement accuracy. Furthermore, based on the obtained internal pressure of the UHV transformer, the operating status of the UHV transformer can be monitored, allowing for preventative measures to be taken before the diaphragm ruptures, thus avoiding transformer combustion and explosion caused by partial discharge. The fiber optic Fabry-Perot strain sensor used in this application offers advantages such as high accuracy, minimal temperature cross-influence, and minimal impact on the diaphragm strain. The first operating wavelength range of the fiber optic Fabry-Perot sensor and the second operating wavelength range of the fiber optic grating temperature sensor are located at opposite ends of the third operating wavelength range of the signal measuring instrument, avoiding superposition of the first optical wave signal from the fiber optic Fabry-Perot sensor and the second optical wave signal from the second fiber optic grating temperature sensor. This enables simultaneous measurement of both the wavelength of the fiber optic grating temperature sensor and the cavity length of the fiber optic Fabry-Perot sensor on the same optical fiber. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the steps of an online monitoring method for the strain of a pressure relief valve diaphragm in an ultra-high voltage transformer, provided by a preferred embodiment of the present invention.

[0046] Figure 2 This is a schematic diagram of the structure and installation position of the fiber optic Fabry-Perot sensor provided in a preferred embodiment of the present invention;

[0047] Figure 3 This is a Fabry-Perot cavity length-strain relationship curve of an optical fiber Fabry-Perot sensor provided in a preferred embodiment of the present invention;

[0048] Figure 4 This is the relationship between the applied strain and the test strain of the fiber optic Fabry-Perot sensor provided in a preferred embodiment of the present invention;

[0049] Figure 5 This is a schematic diagram of the online monitoring results of the diaphragm strain of the pressure relief valve of the ultra-high voltage transformer to be monitored, provided in a preferred embodiment of the present invention;

[0050] Figure 6 This is a schematic diagram of the structure of an online monitoring device for the diaphragm strain of a pressure relief valve in an ultra-high voltage transformer, provided in a preferred embodiment of the present invention.

[0051] Figure 7 This is a schematic diagram of another online monitoring device for pressure relief valve diaphragm strain of an ultra-high voltage transformer provided in a preferred embodiment of the present invention;

[0052] Figure label:

[0053] 1-Fiber Fabry-Perot sensor, 11-First fiber Fabry-Perot sensor, 12-Second fiber Fabry-Perot sensor, 2-Fiber Bragg grating temperature sensor, 21-First fiber Bragg grating temperature sensor, 22-First fiber Bragg grating temperature sensor, 3-Fiber optic group, 31-Guiding fiber, 32-Reflecting fiber, 4-Fiber optic, 41-First fiber optic, 42-Second fiber optic, 5-Signal measuring instrument, 6-Spectrum diagram, 7-Pressure relief valve diaphragm, 8-Pre-grooving, 81-First pre-grooving, 82-Second pre-grooving, 9-Hollow glass capillary tube, 101-First fixing point, 102-Second fixing point. Detailed Implementation

[0054] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The embodiments are provided for illustrative purposes only and should not be construed as limiting the invention. The accompanying drawings are for reference and illustration only and do not constitute a limitation on the scope of protection of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of this invention. In the description of this invention, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0055] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0056] In the description of this invention, it should be noted that, unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing specific embodiments only and is not intended to limit the invention. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0057] Please see Figure 1 The diagram illustrates the steps of an online monitoring method for the diaphragm strain of a pressure relief valve in an ultra-high voltage transformer. In an embodiment of the present invention, a method for online monitoring of the diaphragm strain of a pressure relief valve in an ultra-high voltage transformer is provided, the method comprising:

[0058] S1. A first optical wave signal is acquired using a fiber optic Fabry-Perot sensor, and a second optical wave signal is acquired using a fiber optic grating temperature sensor. The fiber optic Fabry-Perot sensor includes an optical fiber group with its end faces suspended and aligned, and a hollow glass capillary. The optical fiber group includes a guiding fiber and a reflecting fiber. The guiding fiber and the reflecting fiber are located on both sides of a pre-grooved slot in the pressure relief valve diaphragm of the UHV transformer to be monitored, and are fixedly connected to the pressure relief valve diaphragm. Both the guiding fiber and the reflecting fiber are inserted into the hollow glass capillary to form a Fabry-Perot cavity on the pressure relief valve diaphragm. One end of the hollow glass capillary is fixedly connected to the pressure relief valve diaphragm, and the other end is slidably connected to the optical fiber group. In a preferred embodiment of this application, a fiber optic Fabry-Perot sensor is used as a strain sensor to measure the strain of the pressure relief valve diaphragm of the UHV transformer to be monitored. Because the pressure relief valve diaphragm is made of a metallic material with a large coefficient of thermal expansion, temperature changes will cause thermal expansion and contraction of the pressure relief valve diaphragm. The strain caused by the thermal expansion and contraction of the pressure relief valve diaphragm is superimposed on the strain caused by the internal pressure change of the UHV transformer. By measuring temperature changes, the strain of the pressure relief valve diaphragm caused by temperature changes is obtained. Subtracting the strain caused by temperature changes from the total strain yields the true strain of the pressure relief valve diaphragm due to pressure changes within the UHV transformer. Therefore, a fiber optic grating temperature sensor is used to measure the temperature of the environment surrounding the pressure relief valve diaphragm to compensate for the influence of temperature on the strain measurement of the diaphragm. Specifically, a first optical wave signal is acquired using a fiber optic Fabry-Perot sensor, and a second optical wave signal is acquired using a fiber optic grating temperature sensor. The working principle of the pressure relief valve diaphragm is that when the internal pressure of the UHV transformer increases, the diaphragm expands outward, releasing pressure through deformation. When the internal pressure exceeds the design pressure limit of the pressure relief valve diaphragm, the diaphragm ruptures, releasing the pressure inside the UHV transformer. To prevent the installation of the fiber optic Fabry-Perot sensor from affecting the deformation of the pressure relief valve diaphragm and altering its performance, the fiber optic Fabry-Perot sensor in this application is a point-type sensor. Figure 2The diagram shows the structure and installation position of the fiber optic Fabry-Perot sensor 1. The sensor is installed across a small pre-grooved slot 8 on the pressure relief valve diaphragm to measure the strain at the slot 8. The fiber optic Fabry-Perot sensor 1 includes an optical fiber assembly 3 with its end faces suspended and aligned, and a hollow glass capillary tube 9. The optical fiber assembly 3 includes a guide fiber 31 and a reflective fiber 32. The guide fiber 31 and the reflective fiber 32 are located on both sides of the pre-grooved slot 8 on the pressure relief valve diaphragm of the UHV transformer to be monitored, and are fixedly connected to the pressure relief valve diaphragm. The fixed positions are the first fixed point 101 and the second fixed point 102, respectively. The guide fiber 31 and the reflective fiber 32 are inserted into the hollow glass capillary tube 9 to form a Fabry-Perot cavity on the pressure relief valve diaphragm. One end of the hollow glass capillary tube 9 is fixedly connected to the pressure relief valve diaphragm, and the other end is slidably connected to the optical fiber assembly 3. The guiding fiber 31 is used to transmit optical signals, responsible for guiding the optical signals emitted by the light source into the Fabry-Perot cavity and exporting the optical signals reflected / interfered by the reflecting fiber 32 to the signal measuring instrument. One end of the guiding fiber 31 is connected to the broadband light source, and the other end face serves as a reflecting surface of the Fabry-Perot cavity, suspended and aligned with the end face of the reflecting fiber 32. The reflecting fiber 32 is the carrier of the reflecting surface of the Fabry-Perot cavity. Its end face is specially treated, such as coated or polished, to form a highly reflective reflecting surface. Together with the end face of the guiding fiber 31, it forms the Fabry-Perot cavity, which can monitor the distance change between the pre-grooved slots 8 of the pressure relief valve diaphragm. The guide fiber 31 and the reflective fiber 32 are fixedly attached to the pressure relief valve diaphragm, so that the accuracy of the measurement results will not be affected by the change of position. The guide fiber 31 and the reflective fiber 32 are inserted into the hollow glass capillary tube 9. In order to prevent the hollow glass capillary tube 9 from affecting the strain of the pressure relief valve diaphragm, one end of the hollow glass capillary tube 9 is fixedly connected to the pressure relief valve diaphragm, and the other end is slidably connected to the fiber group 3. When the pressure relief valve diaphragm is strained, the hollow glass capillary tube 9 and the fiber group 3 also slide accordingly, without affecting the function of the pressure relief valve diaphragm.

[0059] Furthermore, in a preferred embodiment of this application, a signal measuring instrument is used to collect the optical signals of the fiber optic Fabry-Perot sensor 1 and the fiber optic grating temperature sensor. The fiber optic Fabry-Perot sensor 1, the fiber optic grating temperature sensor, and the signal measuring instrument are connected in series via optical fiber. The first operating wavelength range of the fiber optic Fabry-Perot sensor 1 and the second operating wavelength range of the fiber optic grating temperature sensor are located at opposite ends of the third operating wavelength range of the signal measuring instrument, respectively. This avoids the superposition of the first optical signal of the fiber optic Fabry-Perot sensor 1 and the second optical signal of the second fiber optic grating temperature sensor, thereby enabling simultaneous measurement of the wavelength of the fiber optic grating temperature sensor and the cavity length of the fiber optic Fabry-Perot sensor 1 on the same optical fiber.

[0060] S2. Based on the first optical wave signal, the current cavity length of the Fabry-Perot cavity is obtained; based on the second optical wave signal, the current temperature of the pressure relief valve diaphragm is obtained. The core of the fiber optic Fabry-Perot sensor 1 is the Fabry-Perot cavity. When light is incident into the Fabry-Perot cavity, multiple reflections and interferences occur between the two reflecting end faces of the guiding fiber 31 and the reflecting fiber 32, ultimately forming an interference spectrum. When the interference condition is met, the output optical signal shows a peak value. At this time, the relationship between the wavelength and the cavity length is:

[0061] 2nL=mλ

[0062] Where n represents the refractive index of the medium in the Fabry-Perot cavity. In this application, the medium in the Fabry-Perot cavity is air, so the refractive index is 1. L represents the length of the Fabry-Perot cavity. m represents the interference order, which is a positive integer related to the number of times light is reflected in the Fabry-Perot cavity. λ represents the wavelength corresponding to the interference peak.

[0063] By utilizing the wavelength difference between two adjacent peaks in the interference spectrum, the influence of the interference order m can be eliminated. The cavity length can be directly calculated, and two adjacent peaks can be found in the interference spectrum. The wavelengths of the two adjacent peaks are λ1 and λ2, respectively. Assuming λ2 < λ2, the corresponding interference orders are m and m-1, then the interference equation is:

[0064] 2nL=mλ1

[0065] 2nL=(m-1)λ2

[0066] Solving the two interference equations simultaneously, we obtain the formula for calculating the length of the Fabry-Perot cavity:

[0067]

[0068] Based on the first optical wave signal, the current cavity length of the Fabry-Perot cavity is calculated using the cavity length calculation formula. Typically, the Fabry-Perot cavity is filled with air, and n is set to 1.

[0069] The fiber optic grating temperature sensor is used to measure the ambient temperature of the pressure relief valve diaphragm in a high-voltage transformer. Before measurement, the optimal operating temperature of the pressure relief valve diaphragm is calibrated to obtain a standard temperature. At the standard temperature, the wavelength of the optical signal corresponding to the fiber optic grating temperature sensor is used as the reference wavelength. Based on the wavelength of the second optical signal and the reference wavelength, the current temperature of the pressure relief valve diaphragm is obtained. The formula for calculating the current temperature is:

[0070]

[0071] Where T1 represents the current temperature, λ3 represents the wavelength corresponding to the second optical signal, λ0 represents the reference wavelength, k represents the fiber grating temperature-wavelength coefficient, and T0 represents the standard temperature.

[0072] S3. Based on the current cavity length and the current temperature, the change in the cavity length of the Fabry-Perot cavity caused by the pressure change inside the UHV transformer to be monitored is obtained. In a preferred embodiment of this application, the length of the Fabry-Perot cavity of the fiber optic Fabry-Perot sensor 1 is calibrated at a standard temperature to obtain the original cavity length of the Fabry-Perot cavity. Further, the thermal expansion coefficient of the pressure relief valve diaphragm is calibrated to obtain a calibrated value. The ambient temperature at the current temperature affects the strain of the pressure relief valve diaphragm, and this effect is reflected in the change in the Fabry-Perot cavity length. Therefore, based on the current temperature, the standard temperature, and the calibrated value of the thermal expansion coefficient, the change in temperature of the cavity length of the Fabry-Perot cavity on the pressure relief valve diaphragm due to the current temperature is obtained. The formula for calculating the change in temperature of the Fabry-Perot cavity length is:

[0073] L2=(T1-T0)g

[0074] Where L2 represents the temperature change of the Fabry cavity length, and g represents the calibrated value of the thermal expansion coefficient of the Fabry cavity on the pressure relief valve diaphragm.

[0075] Furthermore, to eliminate the influence of temperature on the pressure relief valve diaphragm strain measurement, the change in cavity length of the Fabry-Perot cavity caused by internal pressure in the UHV transformer is obtained based on the current cavity length, the original cavity length, and the temperature change of the cavity length. The formula for calculating the change in cavity length is:

[0076] ΔL=L1-L0-(T1-T0)g

[0077] Where ΔL represents the change in the length of the Fabry cavity, L1 represents the current length of the Fabry cavity, and L0 represents the original length of the cavity.

[0078] In a preferred embodiment of this application, the current temperature of the pressure relief valve diaphragm is measured by a fiber optic grating temperature sensor, and the temperature change of the cavity length of the Fabry-Perot cavity on the pressure relief valve diaphragm caused by temperature changes is calculated. This eliminates the influence of ambient temperature on the strain of the pressure relief valve diaphragm and improves the accuracy of strain monitoring of the pressure relief valve diaphragm caused by internal pressure changes in the ultra-high voltage transformer.

[0079] S4. Based on the change in cavity length, obtain the strain monitoring result of the pressure relief valve diaphragm; calculate the ratio of the change in cavity length to the distance between the fixed points of the fiber optic Fabry-Perot sensor 1 to obtain the strain result of the pressure relief valve diaphragm. The fixed points of the fiber optic Fabry-Perot sensor 1 include a first fixed point 101 between the guiding fiber 31 and the pressure relief valve diaphragm and a second fixed point 102 between the reflecting fiber 32 and the pressure relief valve diaphragm.

[0080] like Figure 3 The curve showing the relationship between the Fabry-Perot cavity length and strain of the fiber optic Fabry-Perot sensor is given by... Figure 3It can be seen that the Fabry-Perot cavity length of the fiber optic Fabry-Perot sensor 1 increases linearly with the increase of applied strain. By measuring the change in the Fabry-Perot cavity length, the applied strain can be obtained. The change in the Fabry-Perot cavity length measured by the fiber optic Fabry-Perot sensor 1 can be converted into a strain value, and the strain monitoring result of the pressure relief valve diaphragm can be obtained.

[0081] like Figure 4 The figure shows the relationship between the applied strain and the test strain of the fiber optic Fabry-Perot sensor. Figure 4 It can be seen that the ratio of the strain measurement value obtained by the fiber optic Fabry-Perot sensor 1 to the strain applied value is 0.99, which is very close to 1, indicating the accuracy of the fiber optic Fabry-Perot sensor 1.

[0082] like Figure 5 The diagram shows the online monitoring results of the pressure relief valve diaphragm strain in the UHV transformer under test. When the internal pressure of the UHV transformer is low and stable, the pressure relief valve diaphragm strain maintains a stable value. If the internal pressure of the UHV transformer increases, the pressure relief valve diaphragm strain increases, triggering an alarm when it exceeds the alarm threshold. This allows for monitoring of the safety performance of the pressure relief valve diaphragm itself and prediction of potential explosions in the UHV transformer.

[0083] In a preferred embodiment of the present invention, a first optical wave signal is acquired by an optical fiber Fabry-Perot sensor 1, and a second optical wave signal is acquired by a fiber optic grating temperature sensor. The optical fiber Fabry-Perot sensor 1 includes an optical fiber group 3 with its end faces suspended and aligned, and a hollow glass capillary tube 9. The optical fiber group 3 includes a guiding optical fiber 31 and a reflecting optical fiber 32. The guiding optical fiber 31 and the reflecting optical fiber 32 are located on both sides of the pre-grooved slot 8 of the pressure relief valve membrane of the UHV transformer to be monitored, and are fixedly connected to the pressure relief valve membrane. The guiding optical fiber 31 and the reflecting optical fiber 32 are both inserted into the hollow glass capillary tube 9 to form a Fabry-Perot cavity on the pressure relief valve membrane. One end of the hollow glass capillary tube 9 is fixedly connected to the pressure relief valve membrane, and the other end of the hollow glass capillary tube 9 is slidably connected to the optical fiber group 3. The current cavity length of the Fabry-Perot cavity is obtained according to the first optical wave signal, and the current temperature of the pressure relief valve membrane is obtained according to the second optical wave signal. The change in cavity length of the Fabry-Perot cavity caused by the internal pressure change of the UHV transformer to be monitored is obtained according to the current cavity length and the current temperature. The strain monitoring result of the pressure relief valve membrane is obtained according to the change in cavity length. This application discloses an online monitoring method for the strain of a pressure relief valve diaphragm in an ultra-high voltage (UHV) transformer. It measures the current temperature of the pressure relief valve diaphragm using a fiber optic grating temperature sensor, calculates the thermal expansion and contraction of the diaphragm due to temperature changes, and eliminates the influence of ambient temperature on the diaphragm strain. This method offers higher measurement accuracy. Furthermore, based on the obtained internal pressure of the UHV transformer, the operating status of the transformer can be monitored, allowing for preventative measures to be taken before the diaphragm ruptures, thus avoiding transformer combustion and explosion caused by partial discharge. The fiber optic Fabry-Perot strain sensor used in this application offers advantages such as high accuracy, minimal temperature cross-influence, and minimal impact on the diaphragm strain. The first operating spectral wavelength range of the fiber optic Fabry-Perot sensor 1 and the second operating spectral wavelength range of the fiber optic grating temperature sensor are located at opposite ends of the third operating spectral wavelength range of the signal measuring instrument. This avoids the superposition of the first optical wave signal from the fiber optic Fabry-Perot sensor 1 and the second optical wave signal from the second fiber optic grating temperature sensor, enabling simultaneous measurement of the wavelength of the fiber optic grating temperature sensor and the cavity length of the fiber optic Fabry-Perot sensor 1 on the same optical fiber.

[0084] Accordingly, such as Figure 6 The schematic diagram shown is of an online monitoring device for the diaphragm strain of a pressure relief valve in an ultra-high voltage transformer. Based on an online monitoring method for the diaphragm strain of a pressure relief valve in an ultra-high voltage transformer, this embodiment of the invention also provides an online monitoring device for the diaphragm strain of a pressure relief valve in an ultra-high voltage transformer, realizing the online monitoring method for the diaphragm strain of a pressure relief valve in an ultra-high voltage transformer disclosed in this embodiment of the invention. The device includes: an optical fiber Fabry-Perot sensor 1, an optical fiber grating temperature sensor 2, a signal measuring instrument 5, and a signal processing module.

[0085] The fiber optic Fabry-Perot sensor 1, the fiber optic grating temperature sensor 2, and the signal measuring instrument 5 are connected in series via optical fibers.

[0086] The fiber optic Fabry-Perot sensor 1 includes an optical fiber group 3 with its end faces suspended and aligned, and a hollow glass capillary 9. The optical fiber group 3 includes a guiding optical fiber 31 and a reflecting optical fiber 32.

[0087] The guiding optical fiber 31 and the reflecting optical fiber 32 are located on both sides of the pre-grooved slot 8 of the pressure relief valve diaphragm of the UHV transformer to be monitored, and are fixedly connected to the pressure relief valve diaphragm.

[0088] Both the guiding optical fiber 31 and the reflecting optical fiber 32 are inserted into the hollow glass capillary tube 9 to form a Fabry-Perot cavity on the pressure relief valve diaphragm 7.

[0089] One end of the hollow glass capillary tube 9 is fixedly connected to the pressure relief valve diaphragm 7, and the other end of the hollow glass capillary tube 9 is slidably connected to the optical fiber group 3.

[0090] The guiding optical fiber 31 is connected to the fiber grating temperature sensor 2;

[0091] The signal processing module is used to obtain the current cavity length of the Fabry-Perot cavity based on the first optical wave signal, and the current temperature of the pressure relief valve diaphragm 7 based on the second optical wave signal; to obtain the change in cavity length of the pressure relief valve diaphragm 7 caused by the pressure change inside the UHV transformer to be monitored based on the current cavity length and the current temperature; and to obtain the strain monitoring result of the pressure relief valve diaphragm 7 based on the change in cavity length.

[0092] In a preferred embodiment of this application, the current temperature of the pressure relief valve diaphragm 7 is measured by a fiber optic temperature sensor 2. The temperature change of the cavity length of the Fabry-Perot cavity on the pressure relief valve diaphragm 7 caused by temperature changes is calculated, eliminating the influence of ambient temperature on the strain of the pressure relief valve diaphragm 7. This results in higher measurement accuracy. Furthermore, based on the obtained internal pressure of the UHV transformer, the operating status of the UHV transformer can be monitored, allowing for measures to be taken before the diaphragm ruptures, preventing partial discharge from causing a transformer explosion. The fiber optic Fabry-Perot strain sensor of this application has the advantages of high accuracy, minimal temperature cross-influence, and minimal impact on the strain of the pressure relief valve diaphragm 7.

[0093] In a preferred embodiment of this application, a signal measuring instrument 5 is used to acquire the optical signals of the fiber optic Fabry-Perot sensor 1 and the fiber optic grating temperature sensor 2. The fiber optic Fabry-Perot sensor 1 and the fiber optic grating temperature sensor 2 are connected in series and transmitted using a single optical fiber. The first operating spectral wavelength range of the fiber optic Fabry-Perot sensor 1 and the second operating spectral wavelength range of the fiber optic grating temperature sensor 2 are located at opposite ends of the third operating spectral wavelength range of the signal measuring instrument 5, respectively. This avoids the superposition of the first optical signal of the fiber optic Fabry-Perot sensor 1 and the second optical signal of the second fiber optic grating temperature sensor, enabling simultaneous measurement of the wavelength of the fiber optic grating temperature sensor and the cavity length of the fiber optic Fabry-Perot sensor 1 on the same optical fiber. This reduces the amount of optical fiber required, minimizing the impact of online strain monitoring on the performance of the pressure relief valve diaphragm 7 and ensuring the stability and reliability of the pressure relief valve diaphragm 7.

[0094] In a preferred embodiment of this application, the third operating spectral wavelength range of the signal measuring instrument 5 is 1510nm-1590nm, which is the operating wavelength range of the currently mainstream fiber Bragg grating temperature sensor 2 and fiber optic Fabry-Perot sensor 1. This covers a wavelength range of 80nm across the C-band and L-band, sufficient to support the measurement of optical signals from both the fiber optic Fabry-Perot sensor 1 and the fiber optic grating temperature sensor 2. The first operating spectral wavelength range of the fiber optic Fabry-Perot sensor 1 is between 1510nm and 1580nm, and the second operating spectral wavelength range of the fiber optic grating temperature sensor 2 is between 1580nm and 1590nm. The length of the Fabry-Perot cavity is 150μm. Allocating a wider wavelength range to the fiber optic Fabry-Perot sensor 1 enables higher measurement accuracy through white light interferometry demodulation. The operating spectral wavelength range of the fiber optic grating temperature sensor 2 is designed to be within the 10nm range, sufficient to support the wavelength variation range measured by two or more fiber optic grating temperature sensors 2.

[0095] In a preferred embodiment of this application, the third operating spectral wavelength range of the signal measuring instrument 5 is 1528nm-1563nm, the first operating spectral wavelength range of the fiber optic Fabry-Perot sensor 1 is between 1533nm-1563nm, the second operating spectral wavelength range of the fiber optic grating temperature sensor 2 is between 1528-1533nm, and the length of the Fabry-Perot cavity is 250μm. By compressing the operating spectral wavelength ranges of the fiber optic Fabry-Perot sensor 1 and the fiber optic grating temperature sensor 2 into the C-band, fully utilizing mature fiber optic communication devices, and using the signal measuring instrument 5 with its narrow operating spectral wavelength range, demodulation costs can be effectively saved. Designing the operating spectral wavelength range of the fiber optic grating temperature sensor 2 to be in the 5nm range and the operating spectral wavelength range of the fiber optic Fabry-Perot sensor 1 to be in the 30nm range effectively separates the operating spectral wavelength ranges of the fiber optic grating temperature sensor 2 and the fiber optic Fabry-Perot sensor 1, ensuring the accuracy of the measurement results.

[0096] In a preferred embodiment of this application, multiple fiber optic Fabry-Perot sensors 1 and multiple fiber optic grating temperature sensors 2 are included, with each fiber optic Fabry-Perot sensor 1 bridging both sides of the pre-grooved slot 8 of the pressure relief valve diaphragm 7. By using multiple fiber optic Fabry-Perot sensors 1 to measure the strain at different locations on the pressure relief valve diaphragm 7, and using multiple fiber optic grating temperature sensors 2 to measure the temperature at different locations on the pressure relief valve diaphragm 7, more accurate data can be obtained.

[0097] In a preferred embodiment of this application, such as Figure 7 The diagram shows a schematic of another online monitoring device for the strain of a pressure relief valve diaphragm in an ultra-high voltage (UHV) transformer. This device includes a first fiber optic Fabry-Perot sensor 11 and a first fiber optic grating temperature sensor 21 connected in series via a first fiber optic cable 31, and a second fiber optic Fabry-Perot sensor 12 and a second fiber optic grating temperature sensor 22 connected in series via a second fiber optic cable 31. The first fiber optic Fabry-Perot sensor 11 spans both sides of the first pre-grooved slot 81 of the pressure relief valve diaphragm 7, and the second fiber optic Fabry-Perot sensor 12 spans both sides of the second pre-grooved slot 82 of the pressure relief valve diaphragm 7. The installation directions of the first and second fiber optic Fabry-Perot sensors 11 and 12 form a 90° angle. The first and second fiber optic grating temperature sensors 21 and 22 are connected to a signal measuring instrument 5 via optical fibers. This signal measuring instrument is a multi-channel signal measuring instrument.

[0098] In a preferred embodiment of this application, the current temperature of the pressure relief valve diaphragm is measured using a fiber optic grating temperature sensor. The temperature change in the cavity length of the Fabry-Perot cavity on the diaphragm caused by temperature variations is calculated, eliminating the influence of ambient temperature on the diaphragm strain. This results in higher measurement accuracy. Furthermore, based on the obtained internal pressure of the UHV transformer, the operating status of the UHV transformer is monitored, allowing for preventative measures to be taken before the diaphragm ruptures, thus avoiding transformer combustion and explosion caused by partial discharge. The fiber optic Fabry-Perot strain sensor of this application offers advantages in measuring the strain of the pressure relief valve diaphragm, including high accuracy, minimal temperature cross-influence, and minimal impact on the diaphragm strain. The first operating wavelength range of the fiber optic Fabry-Perot sensor and the second operating wavelength range of the fiber optic grating temperature sensor are located at opposite ends of the third operating wavelength range of the signal measuring instrument. This avoids superposition of the first optical wave signal from the fiber optic Fabry-Perot sensor and the second optical wave signal from the second fiber optic grating temperature sensor, enabling simultaneous measurement of the wavelength of the fiber optic grating temperature sensor and the cavity length of the fiber optic Fabry-Perot sensor on the same optical fiber.

[0099] Specific limitations regarding the online monitoring device for the diaphragm strain of an ultra-high voltage transformer pressure relief valve can be found in the above-described limitations regarding the online monitoring method for the diaphragm strain of an ultra-high voltage transformer pressure relief valve, and will not be repeated here. Those skilled in the art will recognize that the various modules and steps described in conjunction with the embodiments disclosed in this invention can be implemented in hardware, software, or a combination of both. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this invention.

[0100] In summary, the online monitoring method and apparatus for the strain of a pressure relief valve diaphragm in an ultra-high voltage transformer provided in this application solves the technical problem of how to monitor the strain of the pressure relief valve diaphragm without affecting its normal operation. The method acquires a first optical wave signal using a fiber optic Fabry-Perot sensor and a second optical wave signal using a fiber optic grating temperature sensor. The fiber optic Fabry-Perot sensor includes an optical fiber group with its end faces suspended and aligned, and a hollow glass capillary tube. The optical fiber group includes a guiding fiber and a reflecting fiber, which are respectively located on both sides of a pre-grooved slot in the pressure relief valve diaphragm of the ultra-high voltage transformer to be monitored, and are aligned with the pressure relief valve diaphragm. The pressure relief valve diaphragm is fixedly connected, and both the guiding optical fiber and the reflecting optical fiber are inserted into a hollow glass capillary tube to form a Fabry-Perot cavity on the pressure relief valve diaphragm. One end of the hollow glass capillary tube is fixedly connected to the pressure relief valve diaphragm, and the other end is slidably connected to the optical fiber group. The current cavity length of the Fabry-Perot cavity is obtained based on a first optical wave signal, and the current temperature of the pressure relief valve diaphragm is obtained based on a second optical wave signal. Based on the current cavity length and current temperature, the change in cavity length of the Fabry-Perot cavity caused by the pressure change inside the UHV transformer to be monitored is obtained. Based on the change in cavity length, the strain monitoring result of the pressure relief valve diaphragm is obtained. The online strain monitoring method for the pressure relief valve diaphragm of a UHV transformer disclosed in this application measures the current temperature of the pressure relief valve diaphragm using a fiber optic grating temperature sensor, calculates the change in cavity length and temperature of the Fabry-Perot cavity on the pressure relief valve diaphragm caused by temperature changes, eliminates the influence of ambient temperature on the strain of the pressure relief valve diaphragm, and has higher measurement accuracy. Furthermore, based on the obtained internal pressure of the UHV transformer, the operating status of the UHV transformer can be monitored, and measures can be taken before the valve diaphragm ruptures to avoid partial discharge causing transformer explosion. The fiber optic Fabry-Perot strain sensor of this application offers advantages such as high accuracy, minimal temperature cross-influence, and minimal impact on the strain of the pressure relief valve diaphragm. The first operating wavelength range of the fiber optic Fabry-Perot sensor and the second operating wavelength range of the fiber optic grating temperature sensor are located at opposite ends of the third operating wavelength range of the signal measuring instrument, respectively. This avoids the superposition of the first optical wave signal from the fiber optic Fabry-Perot sensor and the second optical wave signal from the second fiber optic grating temperature sensor, enabling simultaneous measurement of both the wavelength of the fiber optic grating temperature sensor and the cavity length of the fiber optic Fabry-Perot sensor on the same fiber.

[0101] The various embodiments in this specification are described in a progressive manner. For directly identical or similar parts of the embodiments, refer to each other. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. It should be noted that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification.

[0102] The embodiments described above are merely preferred embodiments of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various improvements and substitutions without departing from the technical principles of this application, and these improvements and substitutions should also be considered within the scope of protection of this application. Therefore, the scope of protection of this patent application should be determined by the scope of the claims.

Claims

1. A method for online monitoring of diaphragm strain in a pressure relief valve of an ultra-high voltage transformer, characterized in that, The method includes: A first optical wave signal is acquired using a fiber optic Fabry-Perot sensor, and a second optical wave signal is acquired using a fiber optic grating temperature sensor. The fiber optic Fabry-Perot sensor includes an optical fiber assembly with its end faces suspended and aligned, and a hollow glass capillary. The optical fiber assembly includes a guide fiber and a reflective fiber. The guide fiber and the reflective fiber are located on both sides of a pre-grooved pressure relief valve diaphragm of the UHV transformer to be monitored, and are fixedly connected to the pressure relief valve diaphragm. Both the guide fiber and the reflective fiber are inserted into the hollow glass capillary to form a Fabry-Perot cavity on the pressure relief valve diaphragm. One end of the hollow glass capillary is fixedly connected to the pressure relief valve diaphragm, and the other end of the hollow glass capillary is slidably connected to the optical fiber assembly. Based on the first optical wave signal, the current cavity length of the Fabry-Perot cavity is obtained, and based on the second optical wave signal, the current temperature of the pressure relief valve diaphragm is obtained. Based on the current cavity length and the current temperature, the change in the cavity length of the Fabry-Perot cavity caused by the pressure change inside the UHV transformer to be monitored is obtained. Based on the change in cavity length, the strain monitoring results of the pressure relief valve diaphragm are obtained.

2. The online monitoring method for diaphragm strain of ultra-high voltage transformer pressure relief valve as described in claim 1, characterized in that, The step of obtaining the change in the length of the Fabry-Perot cavity caused by the pressure change inside the UHV transformer under monitoring, based on the current cavity length and the current temperature, includes: The optimal operating temperature of the pressure relief valve diaphragm is calibrated to obtain a standard temperature, and the length of the Fabry-Perot cavity of the fiber optic Fabry-Perot sensor is calibrated based on the standard temperature to obtain the original cavity length of the Fabry-Perot cavity. The coefficient of thermal expansion of the Fabry-Perot cavity on the pressure relief valve diaphragm is calibrated to obtain the calibrated value of the coefficient of thermal expansion of the Fabry-Perot cavity. Based on the current temperature, the standard temperature, and the calibration value of the coefficient of thermal expansion, the change in temperature of the cavity length of the Fabry-Perot cavity on the pressure relief valve diaphragm due to the current temperature is obtained. Based on the current cavity length, the original cavity length, and the cavity length temperature change, the change in the cavity length of the pressure relief valve diaphragm caused by the internal pressure change of the UHV transformer to be monitored is obtained.

3. The online monitoring method for diaphragm strain of ultra-high voltage transformer pressure relief valve as described in claim 1, characterized in that, The formula for calculating the change in cavity length is: ΔL=L1-L0-(T1-T0)g Where ΔL represents the change in the length of the Fabry cavity, L1 represents the current length of the Fabry cavity, L0 represents the original length of the Fabry cavity, T1 represents the current temperature, T0 represents the standard temperature, and g represents the calibrated value of the thermal expansion coefficient of the pressure relief valve diaphragm.

4. The method for online monitoring of diaphragm strain in ultra-high voltage transformer pressure relief valve as described in claim 1, characterized in that, The process of acquiring the first optical wave signal through a fiber optic Fabry-Perot sensor and the second optical wave signal through a fiber optic grating temperature sensor includes: The fiber optic Fabry-Perot sensor, the fiber optic grating temperature sensor, and the signal measuring instrument are connected in series via optical fiber. The first operating wavelength range of the fiber optic Fabry-Perot sensor and the second operating wavelength range of the second fiber optic grating temperature sensor are located at opposite ends of the third operating wavelength range of the signal measuring instrument. The signal measuring instrument acquires the first optical wave signal of the fiber optic Fabry-Perot sensor and the second optical wave signal of the fiber optic grating temperature sensor.

5. An online monitoring device for the strain of a pressure relief valve diaphragm in an ultra-high voltage transformer, characterized in that, The device for implementing the online monitoring method for the diaphragm strain of the pressure relief valve of an ultra-high voltage transformer as described in any one of claims 1-4 includes: an optical fiber Fabry-Perot sensor, a fiber optic grating temperature sensor, a signal measuring instrument, and a signal processing module; The fiber optic Fabry-Perot sensor, the fiber optic grating temperature sensor, and the signal measuring instrument are connected in series via optical fibers. The fiber optic Fabry-Perot sensor includes an optical fiber assembly with its end faces suspended and aligned, and a hollow glass capillary. The optical fiber assembly includes a guide fiber and a reflective fiber. The guiding optical fiber and the reflecting optical fiber are located on both sides of the pre-grooved slot of the pressure relief valve diaphragm of the UHV transformer to be monitored, and are fixedly connected to the pressure relief valve diaphragm. Both the guiding optical fiber and the reflecting optical fiber are inserted into the hollow glass capillary to form a Fabry-Perot cavity on the pressure relief valve diaphragm. One end of the hollow glass capillary is fixedly connected to the pressure relief valve diaphragm, and the other end of the hollow glass capillary is slidably connected to the optical fiber assembly. The guiding optical fiber is connected to the fiber optic temperature sensor; The signal processing module is used to obtain the current cavity length of the Fabry-Perot cavity based on the first optical wave signal, and to obtain the current temperature of the pressure relief valve diaphragm based on the second optical wave signal; to obtain the change in cavity length of the Fabry-Perot cavity caused by the pressure change inside the UHV transformer to be monitored based on the current cavity length and the current temperature; and to obtain the strain monitoring result of the pressure relief valve diaphragm based on the change in cavity length.

6. The online monitoring device for diaphragm strain of ultra-high voltage transformer pressure relief valve as described in claim 5, characterized in that, The first operating spectral wavelength range of the fiber optic Fabry-Perot sensor and the second operating spectral wavelength range of the fiber optic grating temperature sensor are located at opposite ends of the third operating spectral wavelength range of the signal measuring instrument.

7. The online monitoring device for diaphragm strain of ultra-high voltage transformer pressure relief valve as described in claim 5, characterized in that, The third working spectrum wavelength range is 1510nm-1590nm; The first working spectrum wavelength range is between 1510nm and 1580nm; The second working spectrum wavelength range is between 1580-1590 nm; The original length of the Fabry cavity is 150 μm.

8. The online monitoring device for diaphragm strain of ultra-high voltage transformer pressure relief valve as described in claim 5, characterized in that, The third working spectrum wavelength range is 1528nm-1563nm; The first working spectrum wavelength range is between 1533nm and 1563nm; The second working spectrum wavelength range is between 1528-1533 nm; The original length of the Fabry cavity is 250 μm.

9. The online monitoring device for diaphragm strain of ultra-high voltage transformer pressure relief valve as described in claim 5, characterized in that, The device includes multiple fiber optic Fabry-Perot sensors and multiple fiber optic grating temperature sensors, with each fiber optic Fabry-Perot sensor bridging both sides of the pre-grooved diaphragm of the pressure relief valve.

10. The online monitoring device for diaphragm strain of ultra-high voltage transformer pressure relief valve as described in claim 9, characterized in that, The device includes a first fiber optic Fabry-Perot sensor and a first fiber optic grating temperature sensor connected in series via a first optical fiber, and a second fiber optic Fabry-Perot sensor and a second fiber optic grating temperature sensor connected in series via a second optical fiber. The first fiber optic Fabry-Perot sensor is connected across the two sides of the first pre-grooved slot of the pressure relief valve diaphragm, and the second fiber optic Fabry-Perot sensor is connected across the two sides of the second pre-grooved slot of the pressure relief valve diaphragm. The installation directions of the first fiber optic Fabry-Perot sensor and the second fiber optic Fabry-Perot sensor form a 90° angle.

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