Fabry-Perot sensor and transformer

Abstract

The invention relates to the technical field of sensors, and discloses a Fabry-Perot sensor and a transformer, the sensor comprises a first reflecting surface, a second reflecting surface and an electrorheological fluid, the first reflecting surface and the second reflecting surface form a cavity, the electrorheological fluid is injected into the cavity, and then the cavity is packaged; the distribution structure of the electrorheological fluid in the cavity is changed according to the change of the intensity of the electric field to be measured so as to change the refractive index of the incident light of the optical fiber in the cavity. The problem that an electric field sensor in the prior art is large in size and cannot precisely measure electric field distribution in power equipment is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and in particular to a Fabry-Perot sensor and a transformer. Background Art

[0002] Fiber optic Fabry-Perot sensors have been widely studied and applied in many fields. Compared with other sensors, fiber optic sensors have a series of unique advantages: high sensitivity, anti-electromagnetic interference, corrosion resistance, moisture resistance, good electrical insulation, explosion-proof, and easy to form a telemetry network with fiber optic transmission systems.

[0003] The Fabry-Perot interferometer (FPI), also known as the Fabry-Perot etalon, consists of a cavity formed by two mirrors and the gap between them. The existing technical solution of combining Fabry-Perot sensors with magnetostrictive materials is to fix the magnetostrictive material to the second reflective surface of the Fabry-Perot cavity, and the change of the magnetic field intensity to be measured causes the magnetostrictive material to expand and contract in the axial direction of the optical fiber of the Fabry-Perot cavity, causing the second reflective surface of the Fabry-Perot cavity to deform, and the length of the Fabry-Perot cavity to change, thereby changing the phase difference of the light wave injected between the two reflectors, and then determining the magnetic field size based on the phase difference. In this solution, the magnetostrictive material is outside the Fabry-Perot cavity, resulting in a large volume of the sensor. It is not conducive to the measurement of relevant field strength in a narrow space. Moreover, no relevant technical solutions for using Fabry-Perot sensors to measure electric field strength have been retrieved. Summary of the invention

[0004] In view of this, the present invention provides a Fabry-Perot sensor and a transformer to solve the problem that the electric field sensor is large in size and cannot accurately measure the electric field distribution in the power equipment.

[0005] In a first aspect, the present invention provides a Fabry-Perot sensor, a first reflection surface, a second reflection surface and an electrorheological fluid, wherein:

[0006] The first reflecting surface and the second reflecting surface form a cavity, and the cavity is encapsulated after electrorheological fluid is injected into the cavity;

[0007] The distribution and structure of the electrorheological fluid particle phase in the cavity will change according to the change of the electric field strength to be measured. This change in the particle phase structure can change the refractive index of the optical fiber incident light in the cavity. The change in refractive index will cause the change in the phase angle of the light wave, and then establish the relationship between the electric field strength to be measured and the phase angle of the light wave, so as to detect the electric field strength to be measured. The present invention detects the change in electric field strength by changing the refractive index of the Fabry-Perot sensor instead of changing the Fabry-Perot cavity length.

[0008] The dielectric constant and refractive index of the electrorheological fluid are different due to the random distribution state of the electrorheological fluid particles in the cavity and the chain and cluster state in the spatial electric field. The dielectric constant and refractive index of the electrorheological fluid under different electric field strengths are also different. Therefore, under different electric field strengths, the intensity and phase of the reflected light reflected back by the second reflection surface are also different. Furthermore, the electric field strength is tested by phase difference. The cavity of the present application is fixed, and there is no need for a changing space for the cavity, which greatly reduces the volume of the sensor.

[0009] In some optional embodiments, the electrorheological fluid is a mixed fluid consisting of a dielectric particle phase and a liquid insulating medium.

[0010] In some optional embodiments, the dielectric particle phase is silicon dioxide particles, and the liquid insulating medium is transformer oil.

[0011] In some optional embodiments, the ratio of the dielectric particle phase to the liquid insulating medium is set based on the dielectric constant of the liquid insulating medium.

[0012] In some optional embodiments, the cavity and the optical fiber are fixed together by glue.

[0013] In some optional embodiments, the glue comprises UV curing glue.

[0014] In some optional embodiments, the length of the cavity is set based on the wavelength of the incident light of the optical fiber.

[0015] In some optional embodiments, a first electrode and a second electrode are respectively disposed on the cavity, and the first electrode and the second electrode are used to test the electric field strength between two potentials.

[0016] In some optional embodiments, the first electrode and the second electrode are obtained by deposition or sputtering.

[0017] In a second aspect, the present invention provides a transformer, comprising the Fabry-Perot sensor of the first aspect and any optional embodiment thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 This is the structure diagram of the Fabry-Perot interferometer;

[0020] Figure 2is a structural diagram of a Fabry-Perot sensor according to an embodiment of the present invention;

[0021] Figure 3 is a structural diagram of another Fabry-Perot sensor according to an embodiment of the present invention;

[0022] Figure 4 is a structural diagram of another Fabry-Perot sensor according to an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0025] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] In the related art, reference Figure 1The fiber Fabry-Perot sensor is an optical resonant cavity composed of two optical parallel plates with reflective films on the end faces, a spacing of L, and parallel to each other. When a beam of coherent light is injected into the FP cavity, most of the light is reflected back and forth in the cavity to form an optical resonance. During each reflection process, a small amount of light is transmitted from the two mirrors, and the phase difference between each transmitted light beam and the previous transmitted light beam is constant. The relationship between the relevant parameters can be determined by formula (1). Where θ is the phase difference; n is the refractive index of the cavity medium; L is the FP cavity length, referred to as the cavity length; and λ is the wavelength of the incident light:

[0028] θ=4πnL / λ (1)

[0029] The cavity length L and the refractive index n of the cavity medium are the two main design parameters of the Fabry-Perot sensor. Any change in any parameter in formula (1) can lead to a change in the phase difference θ, thereby obtaining a detection signal of the electric field strength. By demodulating the detected signal, the required information such as the measured value and the change law can be obtained.

[0030] At present, a technical solution for measuring magnetic field by combining magnetostrictive material with Fabry-Perot cavity has been retrieved. The volume of magnetostrictive material changes with the external magnetic field, thereby changing the length of Fabry-Perot cavity connected to the material, and then changing the phase difference between the two reflective surfaces, and then determining the magnitude of magnetic field based on the phase difference. That is, the only technical solution in the prior art is to measure magnetic field strength by Fabry-Perot sensor, and there is no related technical solution in the prior art to use Fabry-Perot sensor to measure electric field strength.

[0031] Oil-immersed transformers are important power equipment in the composition of the national power grid, and their safety has important strategic and economic significance for the operation of the national economy. The internal electric field strength and electric field strength distribution of oil-immersed transformers are of great significance to their own safe operation and operation status diagnosis. The internal installation space of oil-immersed transformers is limited, and large sensors are difficult to install at any position in the transformer test space. It is not convenient to obtain precise transformer internal electric field strength and its electric field strength field distribution parameters, and it is impossible to meet the data precision requirements of the intelligent operation of the power grid for monitoring the transformer operation status, especially the electric field strength at the coil and its electric field strength changes. The data support of the electric field strength information is slightly insufficient. The optical fiber Fabry-Perot sensor is small in size, highly flexible, and can be installed in a small space. It can obtain precise electric field strength distribution data, which is conducive to realizing multi-position electric field strength measurement, providing reliable data for oil-immersed transformer electric field modeling, and monitoring transformer operation status, thereby meeting the data needs of intelligent operation of the power grid.

[0032] In this regard, a Fabry-Perot sensor is provided in this embodiment, such as Figure 2 and Figure 3As shown, the sensor includes: a first reflection surface R1, a second reflection surface R2 and an electrorheological fluid, wherein:

[0033] A cavity is formed between the first reflecting surface R1 and the second reflecting surface R2, and an electrorheological fluid is injected into the cavity and then encapsulated;

[0034] The distribution structure of the electrorheological fluid in the cavity changes according to the change of the electric field intensity to be measured, so as to change the refractive index of the incident light of the optical fiber in the cavity.

[0035] The present application is specifically a Fabry-Perot (FP) sensor, and the electrorheological fluid is specifically an electromagnetic rheological fluid, which is a fluid whose rheological properties can undergo a liquid-solid transition under the action of an external electric field. Figure 2 , I0 is the incident light of the optical fiber, I1 is the reflected light at the first reflection surface R1, and I2 is the reflected light at the second reflection surface R2. Figure 2 It means that when the spatial electric field intensity is zero or low, the particle phase in the electrorheological fluid is randomly distributed. Figure 3 , Figure 3 It means that when the spatial electric field intensity exceeds a threshold value, the electrorheological fluid particle phase is linked and clustered along the direction of the electric field intensity. The dielectric constant and refractive index of the electrorheological fluid are different in the random distribution state of the electrorheological fluid particle phase in the FP cavity and in the state of spatial electric field linking and clustering, that is, the states of linking and clustering under different electric field intensities are different, thereby causing the dielectric constant and refractive index of the electrorheological fluid under different electric field intensities to be different, that is, the cavity medium refractive index n in formula (1). Therefore, under the action of different electric field intensities, the intensity and phase of the reflected light I2 reflected back by the second reflection surface R2 are also different. In this way, by demodulating the reflected light signals of the two reflection surfaces of the first reflection surface R1 and the second reflection surface R2, the relationship between the phase difference of the light signal and the spatial electric field intensity is calibrated, and the spatial electric field intensity value can be measured. The Fabry-Perot sensor cavity of the present application is fixed, does not increase the external volume, does not require the change space of the cavity, and greatly reduces the volume of the sensor.

[0036] In some optional embodiments, such as Figure 2 and Figure 3 As shown, a mixed fluid consisting of a dielectric particle phase and a liquid insulating medium.

[0037] In this embodiment, the dielectric particle phase is solid microparticles or nanoparticles according to their size, that is, the electrorheological fluid is a mixed fluid composed of microparticles and insulating medium, or the electrorheological fluid is a mixed fluid composed of nanoparticles and insulating medium.

[0038] The dielectric constant of micro- and nano-particles is high, and the dielectric constant of insulating media is low. Electrorheological fluid is obtained by mixing micro- and nano-particles and insulating media.

[0039] In some optional embodiments, such as Figure 2 and Figure 3 As shown, the dielectric particle phase is silicon dioxide particles and the liquid insulating medium is transformer oil.

[0040] Silicon dioxide, also known as glass, is an electrorheological fluid particle phase. The particle phase aggregates under the action of an external electric field. As the volume percentage of the particle phase increases, the chain structure changes to a quasi-crystalline structure. Through the structural change of the electrorheological fluid particle phase under the action of an external electric field, the reflection and interference of the incident light will also change. As the particle phase structure changes, its dielectric constant also changes, resulting in a change in the refractive index. If the electrorheological fluid is injected into the Fabry-Perot sensor cavity, the structure of the electrorheological fluid particle phase in the cavity and its refractive index will also change as the strength of the external electric field changes, and the phase angle will also change accordingly. By establishing the correspondence between the phase angle and the strength of the external electric field, the electric field strength value can be measured after calibration.

[0041] In some optional embodiments, such as Figure 2 or Figure 3 , the ratio of the dielectric particle phase to the liquid insulating medium is set based on the dielectric constant of the liquid insulating medium.

[0042] By adjusting the volume percentage between the dielectric particle phase and the liquid insulating medium, the dielectric constant of the electrorheological fluid is adjusted. The dielectric constant of the electrorheological fluid can be configured according to the dielectric constant of the transformer oil so that the sensor is in an operable electric field strength range, which neither exceeds the insulation strength of the sensor nor is lower than the sensor's perceptible electric field strength, thereby avoiding the situation where the electric field strength value cannot be obtained. For example, the higher the electric field strength to be measured, the higher the dielectric constant of the electrorheological fluid needs to be to improve the insulation strength, thereby making the electric field strength shared by the electrorheological fluid lower, preventing the sensor from being damaged by exceeding the bonding strength of the sensor.

[0043] In some optional embodiments, such as Figure 4 As shown, the cavity and the optical fiber are fixed together by glue.

[0044] refer to Figure 4 , a reflective surface and a silicon chip form a bowl-shaped space, and after injecting electrorheological fluid into the bowl-shaped space, the other reflective surface is covered, and then it can be sealed with glue, and then the sealed cavity is fixed to the connecting shell. Finally, the connecting shell is covered with the optical fiber and fixed by dispensing glue. Glue is applied to the part of the connecting shell covering the optical fiber to connect the optical fiber and the cavity together to form an assembly structure with a certain strength.

[0045] In some optional embodiments, the glue comprises UV curing glue.

[0046] The UV curing glue is UV glue, which is applied to the part of the connecting shell that covers the optical fiber, and then irradiated with ultraviolet light. After the glue is cured, the optical fiber and the cavity are connected together to form an assembly structure with a certain strength. The glue can also be hot melt glue or AB (two-component epoxy resin ab adhesive) glue, etc.

[0047] In some optional embodiments, such as Figure 2 or Figure 3 , the length of the cavity is set based on the wavelength of the incident light in the fiber.

[0048] Since the refractive index injected into the cavity is changed by changing the distribution structure of the electrorheological fluid in the cavity, the cavity length L is fixed. The length of the cavity is specifically determined according to the wavelength of the incident light of the optical fiber.

[0049] In some optional embodiments, such as Figure 2 or Figure 3 A first electrode and a second electrode are respectively arranged on the cavity, and the first electrode and the second electrode are used to test the electric field strength between two potentials.

[0050] By contacting two electrodes with different potentials, and then sending incident light into the first reflection surface R1 and the second reflection surface R2 through an optical fiber, and then testing the phase difference between the two reflected lights, the electric field strength between the two potentials is measured.

[0051] In some optional embodiments, the first electrode and the second electrode are obtained by deposition or sputtering.

[0052] In this embodiment, the present invention provides a transformer, which includes the above-mentioned Fabry-Perot sensor. The Fabry-Perot sensor is arranged inside the transformer to monitor the distribution of electric field strength to diagnose the healthy operation of the transformer. Since the cavity of the Fabry-Perot sensor is fixed, the volume of the Fabry-Perot sensor is reduced, so that it can be arranged in a small space inside the coil.

[0053] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A Fabry-Perot sensor, characterized in that: The sensor comprises: a first reflecting surface, a second reflecting surface and an electrorheological fluid, wherein: The first reflecting surface and the second reflecting surface form a cavity, and the cavity is encapsulated after the electrorheological fluid is injected into the cavity; The distribution structure of the electrorheological fluid in the cavity changes according to the change of the electric field intensity to be measured, so as to change the refractive index of the incident light of the optical fiber in the cavity.

2. The sensor according to claim 1, characterized in that The electrorheological fluid is a mixed fluid composed of a dielectric particle phase and a liquid insulating medium.

3. The sensor according to claim 2, characterized in that The dielectric particle phase is silicon dioxide particles, and the liquid insulating medium is transformer oil.

4. The sensor according to claim 2, characterized in that The ratio of the dielectric particle phase to the liquid insulating medium is set based on the dielectric constant of the liquid insulating medium.

5. The sensor according to claim 1, characterized in that The cavity and the optical fiber are fixed together by glue.

6. The sensor according to claim 5, characterized in that The glue comprises UV curing glue.

7. The sensor according to claim 1, characterized in that The length of the cavity is set based on the wavelength of the incident light of the optical fiber.

8. The sensor according to claim 1, characterized in that A first electrode and a second electrode are respectively arranged on the cavity, and the first electrode and the second electrode are used to test the electric field strength between two potentials.

9. The sensor according to claim 8, characterized in that The first electrode and the second electrode are obtained by deposition or sputtering.

10. A transformer, characterized in that: The transformer comprises a Fabry-Perot sensor as claimed in any one of claims 1 to 9.

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