Extra-high voltage transformer pressure relief valve membrane strain on-line monitoring method and device

Abstract

The invention relates to the technical field of on-line monitoring, and discloses an extra-high voltage transformer pressure relief valve membrane strain on-line monitoring method and device, and the method comprises the steps: obtaining a first light wave signal through an optical fiber Fabry-Perot sensor, and obtaining a second light wave signal through an optical fiber grating temperature sensor; the optical fiber Fabry-Perot sensor comprises a guide optical fiber and a reflection optical fiber, the end faces of the guide optical fiber and the reflection optical fiber are suspended and aligned, the guide optical fiber and the reflection optical fiber are located on the two sides of a pre-slotting of the pressure relief valve membrane respectively and inserted into the hollow glass capillary to form a Fabry-Perot cavity, and one end of the hollow glass capillary is fixedly connected with the pressure relief valve membrane. The other end is in sliding connection with the guide fiber or the reflection fiber; obtaining the cavity length variation of the Fabry-Perot cavity 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; and obtaining a strain monitoring result according to the cavity length variation. According to the method, the strain of the pressure relief valve membrane is accurately measured under the condition that normal work of the pressure relief valve membrane is not affected.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of online monitoring, in particular to a method and device for monitoring membrane strain of a pressure relief valve of an extra-high voltage transformer. BACKGROUND

[0002] Partial discharge refers to a non-through discharge phenomenon occurring in a partial area due to uneven electric field distribution inside or on the surface of insulating materials. Partial discharge is an inevitable phenomenon in the operation of a transformer. The voltage and current of an extra-high voltage transformer are high, and the insulating performance of the material is required to be higher, and it is also more likely to cause strong partial discharge. The extra-high voltage transformer is filled with oil, and once the partial discharge causes the extra-high voltage transformer to explode, it will seriously endanger the safety of the surrounding personnel and cause huge economic losses.

[0003] To avoid the explosion of the extra-high voltage transformer, a pressure relief valve membrane is installed on the extra-high voltage transformer to release the pressure inside the extra-high voltage transformer. When the pressure inside the extra-high voltage transformer increases, the pressure relief valve membrane generates strain, and the membrane expands outward and protrudes. When the pressure exceeds the design pressure limit of the membrane, the membrane ruptures, and the pressure inside the extra-high voltage transformer is released. By monitoring the strain of the pressure relief valve membrane, the pressure inside the extra-high voltage transformer can be directly obtained, and the explosion of the extra-high voltage transformer can be predicted. The pressure relief valve membrane releases the internal pressure of the extra-high voltage transformer by itself deformation. The existing strain monitoring method of the pressure relief valve membrane installs a stress sensor to detect the strain of the pressure relief valve membrane, but the stress sensor has an influence on the deformation of the pressure relief valve membrane, which changes the performance of the pressure relief valve membrane and affects the normal work of the pressure relief valve membrane.

[0004] Therefore, how to monitor the strain of the pressure relief valve membrane without affecting the normal work of the pressure relief valve membrane has become a technical problem to be solved by those skilled in the art. SUMMARY

[0005] The present application provides a method and device for monitoring membrane strain of a pressure relief valve of an extra-high voltage transformer, to solve the technical problem of how to monitor the strain of the pressure relief valve membrane without affecting the normal work of the pressure relief valve membrane, and to achieve the effect of accurately measuring the strain of the pressure relief valve membrane without affecting the normal work of the pressure relief valve membrane.

[0006] In a first aspect, the present application provides a method for monitoring membrane strain of a pressure relief valve of an extra-high voltage transformer, comprising:

[0007] The first optical wave signal is acquired by a fiber Fabry-Perot sensor, and the second optical wave signal is acquired by a fiber grating temperature sensor, the fiber Fabry-Perot sensor comprises an optical fiber group with end face suspended alignment and an empty core glass capillary, the optical fiber group comprises a guide optical fiber and a reflection optical fiber, the guide optical fiber and the reflection optical fiber are respectively located on two sides of a pre-slotted pressure relief valve membrane of a to-be-monitored extra-high voltage transformer and are fixedly connected with the pressure relief valve membrane, the guide optical fiber and the reflection optical fiber are inserted into the empty core glass capillary to form a Fabry-Perot cavity on the pressure relief valve membrane, one end of the empty core glass capillary is fixedly connected with the pressure relief valve membrane, and the other end of the empty core glass capillary is slidably connected with the optical fiber group;

[0008] According to the first optical wave signal, a current cavity length of the Fabry-Perot cavity is obtained, and according to the second optical wave signal, a current temperature of the pressure relief valve membrane is obtained.

[0009] According to the current cavity length and the current temperature, a cavity length change amount of the Fabry-Perot cavity caused by the pressure relief valve membrane due to internal pressure change of the to-be-monitored extra-high voltage transformer is obtained.

[0010] According to the cavity length change amount, a strain monitoring result of the pressure relief valve membrane is obtained.

[0011] Preferably, the method for obtaining the cavity length change amount of the Fabry-Perot cavity caused by the pressure relief valve membrane due to internal pressure change of the to-be-monitored extra-high voltage transformer according to the current cavity length and the current temperature comprises:

[0012] An optimal working temperature of the pressure relief valve membrane is calibrated to obtain a standard temperature, and a length of the Fabry-Perot cavity of the fiber Fabry-Perot sensor is calibrated according to the standard temperature to obtain an original cavity length of the Fabry-Perot cavity;

[0013] A thermal expansion coefficient of the pressure relief valve membrane is calibrated to obtain a thermal expansion coefficient calibration value of the pressure relief valve membrane;

[0014] According to the current temperature, the standard temperature and the thermal expansion coefficient calibration value, a cavity length temperature change amount of the pressure relief valve membrane caused by the current temperature is obtained;

[0015] According to the current cavity length, the original cavity length and the cavity length temperature change amount, the cavity length change amount of the Fabry-Perot cavity caused by the pressure relief valve membrane due to internal pressure change of the to-be-monitored extra-high voltage transformer is obtained.

[0016] Preferably, the calculation formula of the cavity length change amount is:

[0017] ΔL=L1-L0-(T1-T0)g

[0018] Wherein, ΔL represents the cavity length variation of the Fabry-Perot cavity, L1 represents the current cavity length of the Fabry-Perot cavity, L0 represents the original cavity length, T1 represents the current temperature, T0 represents the standard temperature, and g represents the thermal expansion coefficient calibration value of the pressure relief valve membrane.

[0019] Preferably, the first optical wave signal is acquired by the optical fiber Fabry-Perot sensor, and the second optical wave signal is acquired by the optical fiber grating temperature sensor, comprising:

[0020] The optical fiber Fabry-Perot sensor, the optical fiber grating temperature sensor and the signal measuring instrument are connected in series through optical fibers, the first working spectral wavelength range of the optical fiber Fabry-Perot sensor and the second working spectral wavelength range of the second optical fiber grating temperature sensor are respectively located at two ends of the third working spectral wavelength range of the signal measuring instrument.

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

[0022] In a second aspect, the present application also provides a device for monitoring strain of a pressure relief valve membrane of an ultra-high voltage transformer, which realizes the method for monitoring strain of the pressure relief valve membrane of the ultra-high voltage transformer, and comprises an optical fiber Fabry-Perot sensor, an optical fiber grating temperature sensor, a signal measuring instrument and a signal processing module.

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

[0024] The optical fiber Fabry-Perot sensor comprises an optical fiber group with end faces in suspension alignment and a hollow glass capillary, and the optical fiber group comprises a guide optical fiber and a reflection optical fiber.

[0025] The guide optical fiber and the reflection optical fiber are respectively located on two sides of a pre-slotted pressure relief valve membrane of the ultra-high voltage transformer to be monitored and are fixedly connected with the pressure relief valve membrane.

[0026] The guide optical fiber and the reflection optical fiber are both inserted into the hollow glass capillary to form a Fabry-Perot cavity on the pressure relief valve membrane.

[0027] One end of the hollow glass capillary is fixedly connected with the pressure relief valve membrane, and the other end of the hollow glass capillary is slidably connected with the optical fiber group.

[0028] The guide optical fiber is connected with the optical fiber grating temperature sensor.

[0029] The signal processing module is configured to obtain a current cavity length of the Fabry-Perot cavity according to the first optical wave signal, obtain a current temperature of the pressure relief valve film according to the second optical wave signal, obtain a cavity length change amount of the Fabry-Perot cavity caused by the pressure relief valve film due to a change in internal pressure of the ultra-high voltage transformer to be monitored according to the current cavity length and the current temperature, and obtain a strain monitoring result of the pressure relief valve film according to the cavity length change amount.

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

[0031] Preferably, the third working spectral wavelength range is 1510nm-1590nm.

[0032] The first working spectral wavelength range is located between 1510nm-1580nm.

[0033] The second working spectral wavelength range is located between 1580-1590nm.

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

[0035] Preferably, the third working spectral wavelength range is 1528nm-1563nm.

[0036] The first working spectral wavelength range is located between 1533nm-1563nm.

[0037] The second working spectral wavelength range is located between 1528-1533nm.

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

[0039] Preferably, the device comprises a plurality of the fiber Fabry-Perot sensors and a plurality of the fiber grating temperature sensors, and each of the fiber Fabry-Perot sensors is connected across two sides of the pre-slotted pressure relief valve film.

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

[0041] The first fiber Fabry-Perot sensor is connected across two sides of a first pre-slotted pressure relief valve film, and the second fiber Fabry-Perot sensor is connected across two sides of a second pre-slotted pressure relief valve film.

[0042] The installation direction between the first fiber-optic Fabry-Perot sensor and the second fiber-optic Fabry-Perot sensor forms a 90° angle.

[0043] The application provides an on-line monitoring method and device for membrane strain of a UHV transformer pressure release valve.

[0044] The on-line monitoring method for membrane strain of a UHV transformer pressure release valve provided by the application measures the current temperature of the pressure release valve membrane through a fiber-optic grating temperature sensor, calculates the cavity length temperature variation of the Fabry-Perot cavity on the pressure release valve membrane caused by temperature variation, eliminates the influence of environmental temperature on the strain of the pressure release valve membrane, and has higher measurement accuracy. Then, the working state of the UHV transformer is monitored according to the obtained internal pressure of the UHV transformer, and measures are taken before the valve membrane is broken, so as to avoid transformer explosion caused by partial discharge. The fiber-optic Fabry-Perot strain sensor has the advantages of high precision, small temperature cross-influence and small influence on the strain of the pressure release valve membrane. The first working spectral wavelength range of the fiber-optic Fabry-Perot sensor and the second working spectral wavelength range of the fiber-optic grating temperature sensor are located at two ends of the third working spectral wavelength range of the signal measuring instrument, so as to avoid the superposition of the first light wave signal of the fiber-optic Fabry-Perot sensor and the second light wave signal of the fiber-optic grating temperature sensor, and realize the 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. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 is a step schematic diagram of an on-line monitoring method for membrane strain of a UHV transformer pressure release valve provided by a preferred embodiment of the application;

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

[0047] Figure 3 is a Fabry-Perot cavity length-strain relationship curve of a fiber-optic Fabry-Perot sensor provided by a preferred embodiment of the application;

[0048] Figure 4 is a relationship between an applied strain and a test strain of a fiber-optic Fabry-Perot sensor provided by a preferred embodiment of the application;

[0049] Figure 5 is an on-line monitoring result schematic diagram of membrane strain of a UHV transformer pressure release valve to be monitored provided by a preferred embodiment of the application;

[0050] Figure 6 is a structure schematic diagram of an on-line monitoring device for membrane strain of a UHV transformer pressure release valve provided by a preferred embodiment of the application;

[0051] Figure 7 is another structure diagram of the on-line monitoring device for membrane strain of the pressure relief valve of the extra-high voltage transformer according to a preferred embodiment of the present application;

[0052] Reference signs:

[0053] 1-fiber Fabry-Perot sensor, 11-first fiber Fabry-Perot sensor, 12-second fiber Fabry-Perot sensor, 2-fiber grating temperature sensor, 21-first fiber grating temperature sensor, 22-second fiber grating temperature sensor, 3-fiber group, 31-guiding fiber, 32-reflecting fiber, 4-fiber, 41-first fiber, 42-second fiber, 5-signal measuring instrument, 6-spectrum diagram, 7-pressure relief valve membrane, 8-pre-slotted, 81-first pre-slotted, 82-second pre-slotted, 9-empty core glass capillary, 101-first fixed point, 102-second fixed point. DETAILED DESCRIPTION

[0054] The embodiments of the present application will be described in detail below with reference to the drawings. The embodiments are presented only for the purpose of illustration and should not be understood as limiting the present application. The accompanying drawings are used for reference and illustration only and do not limit the scope of patent protection of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. In the description of the present application, the terms "first", "second", "third" and the like are used only for the purpose of description and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second", "third" and the like can explicitly or implicitly include one or more features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specified.

[0055] In the description of the present application, it should be noted that, unless otherwise specified and limited, the terms "mounting", "connection" and "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication inside two elements. The term "and / or" used herein includes any and all combinations of one or more related listed items. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0056] In the description of the present application, it should be noted that, unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as commonly understood by one skilled in the art. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. For those skilled in the art, the specific meaning of the above terms in the present application can be understood in specific circumstances.

[0057] Please refer to Figure 1 The steps of a method for monitoring the membrane strain of an ultra-high voltage transformer pressure relief valve are shown in the schematic diagram of the present application. In the embodiments of the present application, a method for monitoring the membrane strain of an ultra-high voltage transformer pressure relief valve is provided, which comprises:

[0058] S1, obtaining a first optical wave signal by a fiber Fabry-Perot sensor, and obtaining a second optical wave signal by a fiber grating temperature sensor, the fiber Fabry-Perot sensor comprising an end-suspended alignment optical fiber group and a hollow glass capillary, the optical fiber group comprising a guide optical fiber and a reflection optical fiber, the guide optical fiber and the reflection optical fiber being respectively located on both sides of the pre-slotted pressure relief valve membrane of the ultra-high voltage transformer to be monitored, and being fixedly connected with the pressure relief valve membrane, the guide optical fiber and the reflection optical fiber being inserted into the hollow glass capillary to form a Fabry-Perot cavity on the pressure relief valve membrane, one end of the hollow glass capillary being fixedly connected with the pressure relief valve membrane, and the other end of the hollow glass capillary being slidably connected with the optical fiber group; in the preferred embodiments of the present application, a fiber Fabry-Perot sensor is used as a strain sensor for measurement, to measure the strain of the pressure relief valve membrane of the ultra-high voltage transformer to be monitored. Since the pressure relief valve membrane is made of a metal material, the thermal expansion coefficient is large, and temperature changes will cause the thermal expansion and contraction of the pressure relief valve membrane. The strain caused by the thermal expansion and contraction of the pressure relief valve membrane is superimposed on the strain caused by the internal pressure change of the ultra-high voltage transformer. By measuring the change of temperature, the strain caused by the temperature change of the pressure relief valve membrane is obtained, and then the strain caused by the temperature change is subtracted from the total strain to obtain the true strain caused by the internal pressure change of the ultra-high voltage transformer. Therefore, a fiber grating temperature sensor is used to measure the temperature of the environment around the pressure relief valve membrane, to compensate for the influence of temperature on the strain measurement of the pressure relief valve membrane. Specifically, a first optical wave signal is obtained by a fiber Fabry-Perot sensor, and a second optical wave signal is obtained by a fiber grating temperature sensor. The working principle of the pressure relief valve membrane is that when the internal pressure of the ultra-high voltage transformer increases, the diaphragm expands outward and protrudes, releasing the pressure by producing deformation, and when the internal pressure exceeds the design pressure limit of the pressure relief valve membrane, the pressure relief valve membrane breaks, and the internal pressure of the ultra-high voltage transformer is released. In order to prevent the installation of the fiber Fabry-Perot sensor from affecting the deformation of the pressure relief valve membrane and changing the performance of the pressure relief valve membrane, the fiber Fabry-Perot sensor of the present application is a point sensor, such as Figure 2The structure and installation position of the optical fiber Fabry-Perot sensor are shown. The installation position of the optical fiber Fabry-Perot sensor 1 is reserved at a small pre-slot 8 of the pressure relief valve film, and the strain at the pre-slot 8 is measured. The optical fiber Fabry-Perot sensor 1 includes an optical fiber group 3 with end face suspended alignment and a hollow glass capillary 9. The optical fiber group 3 includes a guide optical fiber 31 and a reflecting optical fiber 32, which are respectively located on both sides of the pre-slot 8 of the pressure relief valve film of the ultra-high voltage transformer to be monitored, and are fixedly connected with the pressure relief valve film. The fixed positions are respectively a first fixed point 101 and a second fixed point 102. The guide optical fiber 31 and the reflecting optical fiber 32 are inserted into the hollow glass capillary 9 to form a Fabry-Perot cavity on the pressure relief valve film. One end of the hollow glass capillary 9 is fixedly connected with the pressure relief valve film, and the other end of the hollow glass capillary 9 is slidably connected with the optical fiber group 3. The guide optical fiber 31 is used for transmitting an optical signal, is responsible for guiding the optical signal emitted by a light source into the Fabry-Perot cavity, and guiding the reflected / interfered optical signal of the reflecting optical fiber 32 out of the signal measuring instrument. One end of the guide optical fiber 31 is connected with a broadband light source, and the other end surface serves as a reflecting surface of the Fabry-Perot cavity, and is suspended in alignment with the end surface of the reflecting optical fiber 32. The reflecting optical fiber 32 is a carrier of the reflecting surface of the Fabry-Perot cavity, and the end surface thereof is specially treated, such as coating or polishing, to form a high-reflectivity reflecting surface, which constitutes the Fabry-Perot cavity with the end surface of the guide optical fiber 31, and can monitor the distance change between the pre-slots 8 of the pressure relief valve film. The guide optical fiber 31 and the reflecting optical fiber 32 are fixedly attached to the pressure relief valve film, and will not affect the accuracy of the measurement results due to the change of the position. The guide optical fiber 31 and the reflecting optical fiber 32 are inserted into the hollow glass capillary 9. In order to prevent the hollow glass capillary 9 from affecting the strain of the pressure relief valve film, one end of the hollow glass capillary 9 is fixedly connected with the pressure relief valve film, and the other end is slidably connected with the optical fiber group 3. When the pressure relief valve film is strained, the hollow glass capillary 9 and the optical fiber group 3 also slide, and will not affect the function of the pressure relief valve film.

[0059] Further, in the preferred embodiment of the present application, the signal measuring instrument is used to collect the optical wave signals of the optical fiber Fabry-Perot sensor 1 and the optical fiber grating temperature sensor. The optical fiber Fabry-Perot sensor 1, the optical fiber grating temperature sensor and the signal measuring instrument are connected in series through optical fibers. The first working spectral wavelength range of the optical fiber Fabry-Perot sensor 1 and the second working spectral wavelength range of the optical fiber grating temperature sensor are respectively located at both ends of the third working spectral wavelength range of the signal measuring instrument, so as to avoid the superposition of the first optical wave signal of the optical fiber Fabry-Perot sensor 1 and the second optical wave signal of the second optical fiber grating temperature sensor, and to realize the simultaneous measurement of the wavelength of the optical fiber grating temperature sensor and the cavity length of the optical fiber Fabry-Perot sensor 1 on the same optical fiber.

[0060] S2, according to the first optical wave signal, the current cavity length of the Fabry-Perot cavity is obtained, and according to the second optical wave signal, the current temperature of the pressure relief valve membrane is obtained; the core of the fiber Fabry-Perot sensor 1 is a Fabry-Perot cavity. When light is incident into the Fabry-Perot cavity, multiple reflections and interferences will occur between the two reflection end faces of the guide optical fiber 31 and the reflection optical fiber 32, and finally an interference spectrum is formed. When the interference condition is met, the output light signal appears a peak value, and at this time the relationship between the wavelength and the cavity length is:

[0061] 2nL=mλ

[0062] Wherein, n represents the refractive index of the medium in the Fabry-Perot cavity, the medium in the Fabry-Perot cavity of the application is air, so the refractive index is 1, L represents the Fabry-Perot cavity length, m represents the interference order, which is an integer related to the number of reflections of light in the Fabry-Perot cavity, and λ represents the wavelength corresponding to the interference peak.

[0063] The wavelength difference between the two adjacent peaks in the interference spectrum can be used to eliminate the influence of the interference order m, and the cavity length can be directly calculated. From the interference spectrum, find two adjacent peaks, 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] Two interference equations are combined to obtain the cavity length calculation formula of the Fabry-Perot cavity:

[0067]

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

[0069] The fiber grating temperature sensor is used to measure the environmental temperature of the pressure relief valve membrane of the high-voltage transformer. Before measurement, the optimal working temperature of the pressure relief valve membrane is calibrated to obtain a standard temperature. Under the standard temperature, the wavelength of the optical wave signal corresponding to the fiber grating temperature sensor is the reference wavelength. According to the wavelength of the second optical wave signal and the reference wavelength, the current temperature of the pressure relief valve membrane is obtained, and the calculation formula of the current temperature is:

[0070]

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

[0072] S3, obtaining a cavity length change amount of the Fabry-Perot cavity caused by the pressure release valve film due to the internal pressure change of the ultra-high voltage transformer according to the current cavity length and the current temperature; in the preferred embodiment of the present application, the length of the Fabry-Perot cavity of the optical fiber Fabry-Perot sensor 1 is calibrated at a standard temperature to obtain an original cavity length of the Fabry-Perot cavity. Further, the thermal expansion coefficient of the pressure release valve film is calibrated to obtain a thermal expansion coefficient calibration value of the pressure release valve film. The current temperature has a strain influence on the pressure release valve film at the ambient temperature, and the influence is reflected by the Fabry-Perot cavity length change. Therefore, according to the current temperature, the standard temperature and the thermal expansion coefficient calibration value, the cavity length temperature change amount of the Fabry-Perot cavity on the pressure release valve film at the current temperature is obtained, and the calculation formula of the cavity length temperature change amount of the Fabry-Perot cavity is:

[0073] L2 = (T1-T0)g

[0074] Wherein, L2 represents the cavity length temperature change amount of the Fabry-Perot cavity, and g represents the thermal expansion coefficient calibration value of the Fabry-Perot cavity on the pressure release valve film.

[0075] Further, the influence of temperature on the strain measurement of the pressure release valve film is eliminated, and the cavity length change amount of the Fabry-Perot cavity caused by the internal pressure of the ultra-high voltage transformer is obtained according to the current cavity length, the original cavity length and the cavity length temperature change amount, and the calculation formula of the cavity length change amount is:

[0076] ΔL = L1-L0-(T1-T0)g

[0077] Wherein, ΔL represents the cavity length change amount of the Fabry-Perot cavity, L1 represents the current cavity length of the Fabry-Perot cavity, and L0 represents the original cavity length.

[0078] In the preferred embodiment of the present application, the current temperature of the pressure release valve film is measured by the optical fiber grating temperature sensor, the cavity length temperature change amount of the Fabry-Perot cavity on the pressure release valve film caused by the temperature change is calculated, the influence of the ambient temperature on the strain of the pressure release valve film is eliminated, and the accuracy of the strain monitoring of the pressure release valve film caused by the internal pressure change of the ultra-high voltage transformer is improved.

[0079] S4, obtaining the strain monitoring result of the pressure release valve film according to the cavity length change amount; calculating the ratio of the cavity length change amount to the fixed point distance of the optical fiber Fabry-Perot sensor 1 to obtain the strain result of the pressure release valve film, and the fixed points of the optical fiber Fabry-Perot sensor 1 include the first fixed point 101 between the guide optical fiber 31 and the pressure release valve film and the second fixed point 102 between the reflection optical fiber 32 and the pressure release valve film.

[0080] As Figure 3 is the relationship curve between the Fabry-Perot cavity length and the strain of the optical fiber Fabry-Perot sensor, and Figure 3It can be seen that the fiber Fabry-Perot sensor 1 Fabry-Perot cavity length increases linearly with the increase of the applied strain, by measuring the change of Fabry-Perot cavity length to get the applied strain, the fiber Fabry-Perot sensor 1 can be measured by the change of Fabry-Perot cavity length to strain value, get the strain monitoring results of pressure relief valve film.

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

[0082] As shown in Figure 5 The on-line monitoring result schematic diagram of the strain of the pressure relief valve film of the ultra-high voltage transformer to be monitored is shown in the figure, under the condition that the internal pressure of the ultra-high voltage transformer is low and stable, the strain of the pressure relief valve film keeps a stable value. If the internal pressure of the ultra-high voltage transformer increases, the strain of the pressure relief valve film increases, and when it exceeds the alarm threshold, it will alarm in time to realize the monitoring of the safety performance of the pressure relief valve film itself, and predict the explosion of the ultra-high voltage transformer.

[0083] In the preferred embodiment of the present application, the first optical wave signal is obtained by the optical fiber Fabry-Perot sensor 1, and the second optical wave signal is obtained by the optical fiber grating temperature sensor. The optical fiber Fabry-Perot sensor 1 comprises an optical fiber group 3 with end face suspended alignment and a hollow glass capillary 9. The optical fiber group 3 comprises a guide optical fiber 31 and a reflective optical fiber 32. The guide optical fiber 31 and the reflective optical fiber 32 are respectively located on both sides of the pre-slotted 8 of the pressure relief valve membrane of the ultra-high voltage transformer to be monitored, and are fixedly connected with the pressure relief valve membrane. The guide optical fiber 31 and the reflective optical fiber 32 are both inserted into the hollow glass capillary 9 to form a Fabry-Perot cavity on the pressure relief valve membrane. One end of the hollow glass capillary 9 is fixedly connected with the pressure relief valve membrane, and the other end of the hollow glass capillary 9 is slidably connected with the optical fiber group 3. According to the first optical wave signal, the current cavity length of the Fabry-Perot cavity is obtained. According to the second optical wave signal, the current temperature of the pressure relief valve membrane is obtained. According to the current cavity length and the current temperature, the cavity length change amount of the Fabry-Perot cavity caused by the internal pressure change of the ultra-high voltage transformer to be monitored is obtained. According to the cavity length change amount, the strain monitoring result of the pressure relief valve membrane is obtained. The online monitoring method for the strain of the pressure relief valve membrane of the ultra-high voltage transformer disclosed in the present application measures the current temperature of the pressure relief valve membrane by the optical fiber grating temperature sensor, calculates the thermal expansion and contraction of the pressure relief valve membrane caused by the temperature change, eliminates the influence of the environmental temperature on the strain of the pressure relief valve membrane, has higher measurement accuracy, and then monitors the working state of the ultra-high voltage transformer according to the obtained internal pressure of the ultra-high voltage transformer. Measures are taken before the valve membrane is broken to avoid transformer explosion caused by partial discharge. The optical fiber Fabry-Perot strain sensor of the present application has the advantages of high precision, small temperature cross-influence and small influence on the strain of the pressure relief valve membrane. The first working spectral wavelength range of the optical fiber Fabry-Perot sensor 1 and the second working spectral wavelength range of the optical fiber grating temperature sensor are respectively located at both ends of the third working spectral wavelength range of the signal measuring instrument, so as to avoid the superposition of the first optical wave signal of the optical fiber Fabry-Perot sensor 1 and the second optical wave signal of the second optical fiber grating temperature sensor, and realize the simultaneous measurement of the wavelength of the optical fiber grating temperature sensor and the cavity length of the optical fiber Fabry-Perot sensor 1 on the same optical fiber.

[0084] Correspondingly, as shown in Figure 6 the structural schematic diagram of the online monitoring device for the strain of the pressure relief valve membrane of the ultra-high voltage transformer, based on the online monitoring method for the strain of the pressure relief valve membrane of the ultra-high voltage transformer, the present embodiment further provides an online monitoring device for the strain of the pressure relief valve membrane of the ultra-high voltage transformer, which realizes the online monitoring method for the strain of the pressure relief valve membrane of the ultra-high voltage transformer disclosed in the present embodiment. The device comprises 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 optical fiber Fabry-Perot sensor 1, the optical fiber grating temperature sensor 2 and the signal measuring instrument 5 are connected in series through an optical fiber.

[0086] The fiber-optic Fabry-Perot sensor 1 comprises an end-face suspended alignment optical fiber group 3 and a hollow glass capillary 9, the optical fiber group 3 comprising a guide optical fiber 31 and a reflecting optical fiber 32;

[0087] The guide optical fiber 31 and the reflecting optical fiber 32 are respectively located on two sides of a pre-slotted pressure relief valve film 8 of a to-be-monitored extra-high voltage transformer, and are fixedly connected with the pressure relief valve film;

[0088] The guide optical fiber 31 and the reflecting optical fiber 32 are both inserted into the hollow glass capillary 9 to form a Fabry-Perot cavity on the pressure relief valve film 7;

[0089] One end of the hollow glass capillary 9 is fixedly connected with the pressure relief valve film 7, and the other end of the hollow glass capillary 9 is slidably connected with the optical fiber group 3;

[0090] The guide optical fiber 31 is connected with the fiber-optic grating temperature sensor 2;

[0091] The signal processing module is configured to obtain a current cavity length of the Fabry-Perot cavity according to the first optical wave signal, obtain a current temperature of the pressure relief valve film 7 according to the second optical wave signal, obtain a cavity length change amount of the Fabry-Perot cavity caused by the pressure relief valve film 7 due to internal pressure change of the to-be-monitored extra-high voltage transformer according to the current cavity length and the current temperature, and obtain a strain monitoring result of the pressure relief valve film 7 according to the cavity length change amount.

[0092] In the preferred embodiment of the present application, the current temperature of the pressure relief valve film 7 is measured by the fiber-optic grating temperature sensor 2, the cavity length temperature change amount of the Fabry-Perot cavity on the pressure relief valve film 7 caused by temperature change is calculated, the influence of environmental temperature on the strain of the pressure relief valve film 7 is eliminated, and the measurement accuracy is higher, and then the working state of the extra-high voltage transformer is monitored according to the obtained internal pressure of the extra-high voltage transformer, measures are taken before the valve film is broken, and local discharge is avoided to cause transformer explosion. The fiber-optic Fabry-Perot strain sensor of the present application has the advantages of high precision, small temperature cross-influence, and small influence on the strain of the pressure relief valve film 7.

[0093] In a preferred embodiment of the present application, the signal measuring instrument 5 is used to collect the optical wave signals of the fiber-optic F-P sensor 1 and the fiber-optic grating temperature sensor 2. The fiber-optic F-P sensor 1 and the fiber-optic grating temperature sensor 2 are connected in series, and a single optical fiber is used to transmit the optical wave signals. The first working spectral wavelength range of the fiber-optic F-P sensor 1 and the second working spectral wavelength range of the fiber-optic grating temperature sensor 2 are located at the two ends of the third working spectral wavelength range of the signal measuring instrument 5, respectively, so as to avoid the superposition of the first optical wave signal of the fiber-optic F-P sensor 1 and the second optical wave signal of the fiber-optic grating temperature sensor 2, and to realize the simultaneous measurement of the wavelength of the fiber-optic grating temperature sensor and the cavity length of the fiber-optic F-P sensor 1 on the same optical fiber. The amount of optical fiber required is small, the influence of strain online monitoring on the performance of the pressure relief valve membrane 7 is reduced, and the stability and reliability of the operation of the pressure relief valve membrane 7 are ensured.

[0094] In a preferred embodiment of the present application, the third working spectral wavelength range of the signal measuring instrument 5 is 1510nm-1590nm, which is the working wavelength range of the current mainstream fiber-optic grating temperature sensor 2 and fiber-optic F-P sensor 1, covering a total wavelength range of 80nm in C band and L band, which is sufficient to support the measurement of the optical wave signals of the fiber-optic F-P sensor 1 and the fiber-optic grating temperature sensor 2. The first working spectral wavelength range of the fiber-optic F-P sensor 1 is located between 1510nm-1580nm, and the second working spectral wavelength range of the fiber-optic grating temperature sensor 2 is located between 1580-1590nm, and the length of the F-P cavity is 150μm. Assigning a wider wavelength range to the fiber-optic F-P sensor 1 can obtain higher measurement accuracy in white light interference demodulation, and the working spectral wavelength range of the fiber-optic grating temperature sensor 2 is designed to be 10nm, which is sufficient to support the wavelength range in the measurement of more than 2 fiber-optic grating temperature sensors 2.

[0095] In a preferred embodiment of the present application, the third working spectral wavelength range of the signal measuring instrument 5 is 1528nm-1563nm, the first working spectral wavelength range of the fiber-optic F-P sensor 1 is located between 1533nm-1563nm, and the second working spectral wavelength range of the fiber-optic grating temperature sensor 2 is located between 1528-1533nm, and the length of the F-P cavity is 250μm. The working spectral wavelength ranges of the fiber-optic F-P sensor 1 and the fiber-optic grating temperature sensor 2 are compressed into the C band range, making full use of mature fiber-optic communication devices, and using a signal measuring instrument 5 with a narrower working spectral wavelength range can effectively save the demodulation cost. The working spectral wavelength range of the fiber-optic grating temperature sensor 2 is designed to be 5nm, and the working spectral wavelength range of the fiber-optic F-P sensor 1 is designed to be 30nm, which effectively separates the working spectral wavelength ranges of the fiber-optic grating temperature sensor 2 and the fiber-optic F-P sensor 1, and ensures the accuracy of the measurement results.

[0096] In a preferred embodiment of the present application, a plurality of fiber-optic Fabry-Perot sensors 1 and a plurality of fiber-optic grating temperature sensors 2 are included, and each fiber-optic Fabry-Perot sensor 1 is connected across two sides of the pre-slotted groove 8 of the pressure relief valve membrane 7. The strain of the pressure relief valve membrane 7 at different positions is measured by using a plurality of fiber-optic Fabry-Perot sensors 1, and the temperature of the pressure relief valve membrane 7 at different positions is measured by using a plurality of fiber-optic grating temperature sensors 2, so that more accurate data is obtained.

[0097] In a preferred embodiment of the present application, as shown in Figure 7 Another structure diagram of an on-line monitoring device for strain of a pressure relief valve membrane of an extra-high voltage transformer is shown in FIG. 6. The on-line monitoring device for strain of the pressure relief valve membrane of the extra-high voltage transformer includes a first fiber-optic Fabry-Perot sensor 11 and a first fiber-optic grating temperature sensor 21 connected in series through a first optical fiber 31, and a second fiber-optic Fabry-Perot sensor 12 and a second fiber-optic grating temperature sensor 22 connected in series through a second optical fiber 31. The first fiber-optic Fabry-Perot sensor 11 is connected across two sides of a first pre-slotted groove 81 of the pressure relief valve membrane 7, the second fiber-optic Fabry-Perot sensor 12 is connected across two sides of a second pre-slotted groove 82 of the pressure relief valve membrane 7, and the installation direction of the first fiber-optic Fabry-Perot sensor 11 and the second fiber-optic Fabry-Perot sensor 12 forms a 90° angle. The first fiber-optic grating temperature sensor 21 and the second fiber-optic grating temperature sensor 22 are connected to a signal measuring instrument 5 through optical fibers, and the signal measuring instrument is a multi-channel signal measuring instrument.

[0098] In a preferred embodiment of the present application, the current temperature of the pressure relief valve membrane is measured by using the fiber-optic grating temperature sensor, the temperature variation of the cavity length of the Fabry-Perot cavity on the pressure relief valve membrane caused by temperature change is calculated, the influence of the ambient temperature on the strain of the pressure relief valve membrane is eliminated, and the measurement accuracy is higher. Then, the working state of the extra-high voltage transformer is monitored according to the obtained internal pressure of the extra-high voltage transformer, and measures are taken before the valve membrane is broken, so that the transformer explosion caused by partial discharge is avoided. The fiber-optic Fabry-Perot strain sensor for measuring the strain of the pressure relief valve membrane has the advantages of high accuracy, small temperature cross-influence, and small influence on the strain of the pressure relief valve membrane. The first working spectral wavelength range of the fiber-optic Fabry-Perot sensor and the second working spectral wavelength range of the fiber-optic grating temperature sensor are located at two ends of a third working spectral wavelength range of the signal measuring instrument, so that the first light wave signal of the fiber-optic Fabry-Perot sensor and the second light wave signal of the fiber-optic grating temperature sensor are not superimposed, and the wavelength of the fiber-optic grating temperature sensor and the cavity length of the fiber-optic Fabry-Perot sensor are measured on the same optical fiber at the same time.

[0099] The specific limitation of the on-line monitoring device for the membrane strain of the pressure relief valve of an extra-high voltage transformer can refer to the above-mentioned limitation of the on-line monitoring method for the membrane strain of the pressure relief valve of an extra-high voltage transformer, which will not be repeated here. Those skilled in the art can realize that, in combination with the embodiments disclosed in the present application, each module and step described can be realized in hardware, software or a combination of both. Whether the functions are realized in hardware or software depends on the specific application and design constraints of the technical solution. The skilled person can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0100] In summary, the method and device for monitoring the strain of the pressure relief valve membrane of the UHV transformer provided by the embodiments of the present application solve the technical problem of how to monitor the strain of the pressure relief valve membrane without affecting the normal operation of the pressure relief valve membrane. The method obtains a first optical signal by using a fiber-optic F-P sensor, and obtains a second optical signal by using a fiber-optic grating temperature sensor. The fiber-optic F-P sensor includes an optical fiber group with an end face suspended in alignment and a hollow glass capillary. The optical fiber group includes a guide optical fiber and a reflection optical fiber. The guide optical fiber and the reflection optical fiber are respectively located on two sides of a pre-slotted pressure relief valve membrane of the UHV transformer to be monitored, and are fixedly connected with the pressure relief valve membrane. Both the guide optical fiber and the reflection optical fiber are inserted into the hollow glass capillary to form an F-P cavity on the pressure relief valve membrane. One end of the hollow glass capillary is fixedly connected with the pressure relief valve membrane, and the other end of the hollow glass capillary is slidably connected with the optical fiber group. According to the first optical signal, the current cavity length of the F-P cavity is obtained. According to the second optical signal, the current temperature of the pressure relief valve membrane is obtained. According to the current cavity length and the current temperature, the cavity length change amount of the F-P cavity caused by the internal pressure change of the UHV transformer to be monitored is obtained. According to the cavity length change amount, the strain monitoring result of the pressure relief valve membrane is obtained. The method for monitoring the strain of the pressure relief valve membrane of the UHV transformer disclosed in the present application measures the current temperature of the pressure relief valve membrane by using the fiber-optic grating temperature sensor, calculates the cavity length temperature change amount of the F-P cavity on the pressure relief valve membrane caused by the temperature change, eliminates the influence of the environmental temperature on the strain of the pressure relief valve membrane, has higher measurement accuracy, and then monitors the working state of the UHV transformer according to the obtained internal pressure of the UHV transformer, takes measures before the valve membrane is broken, and avoids the transformer explosion caused by partial discharge. The fiber-optic F-P strain sensor for measuring the strain of the pressure relief valve membrane has the advantages of high precision, small temperature cross-influence, and small influence on the strain of the pressure relief valve membrane. The first working spectral wavelength range of the fiber-optic F-P sensor and the second working spectral wavelength range of the fiber-optic grating temperature sensor are respectively located at two ends of a third working spectral wavelength range of a signal measuring instrument, so as to avoid the superposition of the first optical signal of the fiber-optic F-P sensor and the second optical signal of the second fiber-optic grating temperature sensor, and realize the simultaneous measurement of the wavelength of the fiber-optic grating temperature sensor and the cavity length of the fiber-optic F-P sensor on the same optical 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. An on-line monitoring method of membrane strain of a pressure relief valve of an extra-high voltage transformer, characterized in that, The method comprises: obtaining a first optical wave signal through a fiber Fabry-Perot sensor and a second optical wave signal through a fiber grating temperature sensor, wherein the fiber Fabry-Perot sensor comprises an end-face suspended alignment fiber group and a hollow glass capillary, the fiber group comprises a guide fiber and a reflection fiber, the guide fiber and the reflection fiber are respectively located on two sides of a pre-slotted pressure relief valve membrane of a to-be-monitored extra-high voltage transformer and are fixedly connected with the pressure relief valve membrane, the guide fiber and the reflection fiber are inserted into the hollow glass capillary to form a Fabry-Perot cavity on the pressure relief valve membrane, one end of the hollow glass capillary is fixedly connected with the pressure relief valve membrane, and the other end of the hollow glass capillary is slidably connected with the fiber group; obtaining a current cavity length of the Fabry-Perot cavity according to the first optical wave signal and a current temperature of the pressure relief valve membrane according to the second optical wave signal; obtaining a cavity length change amount of the Fabry-Perot cavity caused by the pressure relief valve membrane due to internal pressure change of the to-be-monitored extra-high voltage transformer according to the current cavity length and the current temperature; obtaining a strain monitoring result of the pressure relief valve membrane according to the cavity length change amount.

2. The membrane strain online monitoring method of the ultra-high voltage transformer pressure relief valve according to claim 1, characterized in that, The method comprises: calibrating an optimal working temperature of the pressure relief valve membrane to obtain a standard temperature, and calibrating a length of the Fabry-Perot cavity of the fiber Fabry-Perot sensor according to the standard temperature to obtain an original cavity length of the Fabry-Perot cavity; calibrating a thermal expansion coefficient of the Fabry-Perot cavity on the pressure relief valve membrane to obtain a thermal expansion coefficient calibration value of the Fabry-Perot cavity; obtaining a cavity length temperature change amount of the Fabry-Perot cavity on the pressure relief valve membrane caused by the current temperature according to the current temperature, the standard temperature and the thermal expansion coefficient calibration value; obtaining the cavity length change amount of the Fabry-Perot cavity caused by the pressure relief valve membrane due to internal pressure change of the to-be-monitored extra-high voltage transformer according to the current cavity length, the original cavity length and the cavity length temperature change amount.

3. The membrane strain on-line monitoring method of the ultra-high voltage transformer pressure relief valve according to claim 1, characterized in that, The calculation formula of the cavity length change amount is as follows: ΔL = L1 - L0 - (T1 - T0)g wherein ΔL represents the cavity length change amount of the Fabry-Perot cavity, L1 represents the current cavity length of the Fabry-Perot cavity, L0 represents the original cavity length, T1 represents the current temperature, T0 represents the standard temperature, and g represents the thermal expansion coefficient calibration value of the pressure relief valve membrane.

4. The method of claim 1, wherein the method is characterized by, The method comprises: connecting the fiber Fabry-Perot sensor, the fiber grating temperature sensor and a signal measuring instrument in sequence through optical fibers, wherein a first working spectral wavelength range of the fiber Fabry-Perot sensor and a second working spectral wavelength range of the second fiber grating temperature sensor are respectively located at two ends of a third working spectral wavelength range of the signal measuring instrument; collecting the first optical wave signal of the fiber Fabry-Perot sensor and the second optical wave signal of the fiber grating temperature sensor through the signal measuring instrument.

5. An on-line monitoring device for membrane strain of a pressure relief valve of an extra-high voltage transformer, characterized in that, The device is used for realizing the method for monitoring the membrane strain of the pressure relief valve of the ultra-high voltage transformer, and comprises a fiber-optic 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 through an optical fiber. The fiber-optic Fabry-Perot sensor comprises an optical fiber group with end face suspended alignment and a hollow glass capillary tube. The leading optical fiber and the reflecting optical fiber are respectively located on two sides of a pre-slotted pressure relief valve membrane of the ultra-high voltage transformer to be monitored and are fixedly connected with the pressure relief valve membrane. The leading optical fiber and the reflecting optical fiber are inserted into the hollow glass capillary tube to form a Fabry-Perot cavity on the pressure relief valve membrane. One end of the hollow glass capillary tube is fixedly connected with the pressure relief valve membrane, and the other end of the hollow glass capillary tube is slidably connected with the optical fiber group. The leading optical fiber is connected with the fiber-optic grating temperature sensor. The signal processing module is used for obtaining a current cavity length of the Fabry-Perot cavity according to the first optical wave signal, obtaining a current temperature of the pressure relief valve membrane according to the second optical wave signal, obtaining a cavity length change amount of the Fabry-Perot cavity caused by the pressure relief valve membrane due to the internal pressure change of the ultra-high voltage transformer to be monitored according to the current cavity length and the current temperature, and obtaining a strain monitoring result of the pressure relief valve membrane according to the cavity length change amount.

6. The membrane strain on-line monitoring device of the ultra-high voltage transformer pressure relief valve according to claim 5, characterized in that, The first working spectral wavelength range of the fiber-optic Fabry-Perot sensor and the second working spectral wavelength range of the fiber-optic grating temperature sensor are respectively located at two ends of a third working spectral wavelength range of the signal measuring instrument.

7. The membrane strain on-line monitoring device of the ultra-high voltage transformer pressure relief valve according to claim 5, characterized in that, The third working spectral wavelength range is 1510nm-1590nm. The first working spectral wavelength range is located between 1510nm-1580nm. The second working spectral wavelength range is located between 1580-1590nm. The original cavity length of the Fabry-Perot cavity is 150μm.

8. The membrane strain on-line monitoring device of the ultra-high voltage transformer pressure relief valve according to claim 5, characterized in that, The third working spectral wavelength range is 1528nm-1563nm. The first working spectral wavelength range is located between 1533nm-1563nm. The second working spectral wavelength range is located between 1528-1533nm. The original cavity length of the Fabry-Perot cavity is 250μm.

9. The membrane strain on-line monitoring device of the ultra-high voltage transformer pressure relief valve according to claim 5, characterized in that, The device comprises a plurality of fiber-optic Fabry-Perot sensors and a plurality of fiber-optic grating temperature sensors, and each fiber-optic Fabry-Perot sensor is connected across two sides of a pre-slotted pressure relief valve membrane.

10. The membrane strain on-line monitoring device of the ultra-high voltage transformer pressure relief valve according to claim 9, characterized in that, The device comprises a first fiber-optic Fabry-Perot sensor and a first fiber-optic grating temperature sensor connected in series through a first optical fiber, and a second fiber-optic Fabry-Perot sensor and a second fiber-optic grating temperature sensor connected in series through a second optical fiber. The first fiber-optic Fabry-Perot sensor is connected across two sides of a first pre-slotted pressure relief valve membrane, and the second fiber-optic Fabry-Perot sensor is connected across two sides of a second pre-slotted pressure relief valve membrane. The installation direction between the first fiber-optic Fabry-Perot sensor and the second fiber-optic Fabry-Perot sensor forms a 90° included angle.

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