An all-fiber temperature detection device for transformer windings based on vernier effect

Abstract

The present invention discloses a transformer winding all-fiber temperature detection device based on the vernier effect, comprising a temperature sensing unit and a signal acquisition unit; the temperature sensing unit comprises a Sagnac ring cascade, a plurality of 2×2 couplers and a broadband light source; the Sagnac ring cascade comprises a first Sagnac interference ring and a second Sagnac interference ring; the first Sagnac interference ring comprises a reference fiber disk, a single-mode fiber and a polarization-maintaining fiber; the second Sagnac interference ring comprises a sensing fiber disk, a single-mode fiber and a polarization-maintaining fiber; the interiors of the sensing fiber disk and the reference fiber disk are respectively connected with polarization-maintaining fibers of different lengths; the signal acquisition unit is composed of a spectrum analyzer, a data acquisition card, a computer, a 1×4 coupler and an optical switch. The present invention can realize high-sensitivity in-situ detection of transformer winding temperature, while avoiding the influence of stress caused by winding deformation or transformer vibration.

Description

Technical Field

[0001] The invention relates to the technical field of optical sensing systems, and in particular to a transformer winding all-optical fiber temperature detection device based on a vernier effect. Background Art

[0002] During the long-term operation of the transformer, the aging or damage of the winding insulation often causes a short circuit and local overheating of the winding. The high temperature of the winding will cause the insulation to age faster, affecting the life of the transformer, or even directly burning the transformer and causing loss of life and property. In order to avoid serious accidents caused by overheating of the transformer winding, it is necessary to detect the temperature status of the transformer winding in real time. In recent years, with the development of optical fiber sensing technology, the method of measuring temperature using optical fiber has overcome the shortcomings of traditional electrical temperature measurement, such as being easily affected by electromagnetic interference, and has received widespread attention.

[0003] Existing transformer winding temperature sensors based on fiber optic sensing technology generally use fiber Bragg gratings as temperature sensing elements. However, on the one hand, the fiber Bragg grating itself is relatively fragile. In the transformer winding, especially the oil-immersed transformer winding environment, the harsh oil environment and the transformer vibration or winding deformation make the fiber Bragg grating easy to break. Even if the surface is wrapped with a reinforced structure, it will inevitably be affected by stress, resulting in inaccurate temperature detection results and difficulty in disassembly. On the other hand, the sensitivity of temperature sensors based on fiber Bragg grating is mostly low, about 10pm / ℃, which cannot meet the needs of accurately measuring the temperature of transformer windings.

[0004] Compared with fiber grating sensors, interferometric temperature sensors have the advantages of high sensitivity, less environmental influence, and easy distribution. As a means of enhancing sensitivity, the optical vernier effect is widely used in interferometric fiber sensors. At present, interferometric structures such as cascaded FPI, MZI, and FSI have appeared. However, for the temperature measurement of transformer windings, the deformation of the windings or the vibration of the transformer, especially the oil environment of oil-immersed transformers, can easily affect the accuracy of the measurement results. Therefore, a temperature sensing system that can adapt to winding deformation or transformer vibration and can measure at multiple points is required. The fiber Sagnac interferometer composed of polarization-maintaining fiber has the advantages of simple structure, compactness, and less interference. Therefore, the temperature sensor that uses the cascaded Sagnac interference to generate the vernier effect to achieve temperature sensitization can effectively solve the problem of insufficient sensitivity of current temperature sensors and their inability to adapt to the winding environment. Summary of the invention

[0005] The present invention proposes an all-fiber temperature detection device for transformer windings based on the vernier effect. Two sections of polarization-maintaining optical fibers of different lengths are used as a fixed part and a sliding part for generating the vernier effect, respectively. By coiling the polarization-maintaining optical fibers, high-sensitivity in-situ detection of the transformer winding temperature can be achieved, while avoiding the influence of stress caused by winding deformation or transformer vibration. Multi-point measurement of the transformer winding can be achieved by using a 1×4 coupler and an optical switch.

[0006] In order to solve the above problems, the present invention proposes a transformer winding all-fiber temperature detection device based on the vernier effect, which includes a temperature sensing unit and a signal acquisition unit;

[0007] The temperature sensing unit includes a Sagnac ring cascade, a plurality of 2×2 couplers and a broadband light source; the Sagnac ring cascade includes a first Sagnac interference ring and a second Sagnac interference ring; the first Sagnac interference ring includes a reference fiber disk, a single-mode fiber and a polarization-maintaining fiber; the second Sagnac interference ring includes a sensing fiber disk, a single-mode fiber and a polarization-maintaining fiber; the interiors of the sensing fiber disk and the reference fiber disk are respectively connected with polarization-maintaining fibers of different lengths; the interference spectrum generated by the second Sagnac interference ring serves as a sliding part causing a vernier effect, and the polarization-maintaining fiber inside the second Sagnac interference ring serves as a temperature-sensitive part that is closely attached to the transformer winding to realize temperature sensing; the interference spectrum generated by the first Sagnac interference ring serves as a fixed part causing a vernier effect and is placed in a shielding box near the transformer; the broadband light source is connected to the first Sagnac interference ring through a 2×2 coupler;

[0008] The signal acquisition unit is composed of a spectrum analyzer, a data acquisition card, a computer, a 1×4 coupler and an optical switch; the sensing optical fiber disk and the reference optical fiber disk are respectively connected to the 1×4 coupler through a 2×2 coupler; the 1×4 coupler is used to evenly divide the optical signal after the first interference generated by the first Sagnac interference ring into 4 paths, and transmit it to the next second Sagnac interference ring of each optical path as a sliding part at the same time; the optical switch is located in the transmission optical path from the second Sagnac interference ring to the spectrum analyzer; the spectrum analyzer can identify at least one complete spectrum envelope cycle; the data acquisition card is used to collect and calculate the temperature change corresponding to the real-time offset of the spectrum envelope wavelength and upload it to the computer; the computer is used to control the winding measurement point temperature required for the optical signal transmission path according to the temperature change.

[0009] Preferably, the optical power of the broadband light source is not less than 35mW; the splitting ratio of the 2×2 coupler is 50:50; the splitting ratio of the 1×4 coupler is 25:25:25:25; the scanning range of the spectrum analyzer is 1460-1600nm, and the wavelength resolution is 0.004nm.

[0010] Preferably, the polarization-maintaining optical fiber in the sensing optical fiber disc is wound in a disc-shaped single layer and placed in a packaging box made of insulating paper laminate; the polarization-maintaining optical fiber in the reference optical fiber disc is wound in a disc-shaped single layer and placed in a packaging box made of SiO2 aerogel.

[0011] Preferably, the packaging boxes of the sensing optical fiber disk and the reference optical fiber disk are both hollow rectangular blocks as a whole, with square upper and lower surfaces, hollow inside, and an opening on one side, which is rectangular; the height of the packaging box is 6 mm, the thickness is 1 mm, the side length of the box is 7 cm, the width of the opening is 2 mm, and the length does not exceed 6.5 cm. The inside is filled with epoxy resin, bonded, and the opening is sealed.

[0012] Preferably, the packaged sensing fiber discs are evenly distributed on the transformer windings at vertical intervals of 15 to 20 cm as temperature sensing contacts. The reference fiber disc is placed in a shielding box near the transformer. The single-mode optical fibers led out of each fiber disc are gathered at the optical switch for signal transmission.

[0013] Preferably, both ends of the polarization-maintaining optical fibers in the sensing optical fiber disk and the reference optical fiber disk are fused with single-mode optical fibers and lead out two optical fiber interfaces, which are used to directly connect to a 2×2 coupler with a fusion loss not exceeding 3dB.

[0014] Preferably, the polarization-maintaining optical fibers of the sensing optical fiber disk and the reference optical fiber disk are both panda-type polarization-maintaining optical fibers, with a working band coverage of 1460-1600 nm, and an optical fiber diameter not exceeding 15 μm to ensure low-loss fusion with a single-mode optical fiber. The length of the polarization-maintaining optical fiber wound into the reference optical fiber disk is 2.5 m, and the length of the polarization-maintaining optical fiber wound into the sensing optical fiber disk is 2.65 m to ensure that the generated superimposed spectrum can be effectively identified by the spectrum analyzer as a complete spectrum envelope period.

[0015] Preferably, the inner diameter of the optical fiber disk wound with the polarization-maintaining optical fiber of the sensing optical fiber disk and the reference optical fiber disk is not less than 5 cm, and the outer diameter is not more than 6.5 cm, so as to ensure good transmission performance of the optical fiber.

[0016] The beneficial effects of the present invention are as follows:

[0017] (1) Since the polarization-maintaining optical fiber itself is insensitive to stress, after the present invention fixes it in a packaging box made of insulating paper laminate, it effectively avoids interference from winding deformation or transformer vibration, and can adapt well to the oil environment near the winding.

[0018] (2) The present invention utilizes the vernier effect produced by the cascaded Sagnac interference ring structure to achieve enhanced temperature sensitivity, and has a simple structure and is easy to manufacture.

[0019] (3) The present invention utilizes an optical switch to control the transmission path of the optical fiber signal, thereby realizing quasi-distributed temperature detection, quickly locating the heating position of the winding, and eliminating faults in a timely manner.

[0020] (4) The present invention proposes a transformer winding all-fiber temperature detection device based on the vernier effect, which can effectively adapt to the harsh environment inside the transformer winding, greatly improve the temperature sensitivity, and solve the problem of measurement accuracy caused by the deformation of the winding or the vibration of the transformer caused by the traditional fiber optic temperature sensor. The use of 1×4 coupler, optical switch and multiple temperature sensing units realizes quasi-distributed detection of winding temperature, which can quickly locate the heating position of the winding and detect faults in time. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 This is an optical path topology diagram of all-fiber temperature detection based on the vernier effect according to an embodiment of the present invention.

[0023] Figure 2 This is a structural diagram of a polarization-maintaining optical fiber disk packaging box according to an embodiment of the present invention.

[0024] Figure 3 This is a layout diagram of a transformer winding all-optical fiber temperature detection device according to an embodiment of the present invention.

[0025] Among them, 1 is a broadband light source, 2 and 5 are 2×2 couplers, 3 is a reference fiber disk, 4 is a sensing fiber disk, 6 is a spectrum analyzer, 7 is a data acquisition card, 8 is a computer, 9 is a 1×4 coupler, 10 is an optical switch; 11 is a polarization-maintaining fiber; and 12 is a single-mode fiber. DETAILED DESCRIPTION

[0026] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0027] It should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, or are the orientation or positional relationship in which the invented product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply 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", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0028] In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components are required to be absolutely horizontal or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0029] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" 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, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] like Figure 1 As shown, an all-optical fiber temperature detection device for transformer windings based on vernier effect in this embodiment includes a temperature sensing unit and a signal acquisition unit.

[0031] The temperature sensing unit includes a Sagnac ring cascade, several 2×2 couplers and a broadband light source 1. The Sagnac ring cascade includes a first Sagnac interference ring and a second Sagnac interference ring. The first Sagnac interference ring includes a reference fiber disk 3, a single-mode fiber 12 and a polarization-maintaining fiber 11. The second Sagnac interference ring includes a sensing fiber disk 4, a single-mode fiber 12 and a polarization-maintaining fiber 11. The interiors of the sensing fiber disk 4 and the reference fiber disk 3 are respectively connected with polarization-maintaining fibers 11 of different lengths. The interference spectrum generated by the second Sagnac interference ring serves as a sliding part that causes a vernier effect, and the polarization-maintaining fiber 11 inside it serves as a temperature-sensitive part that is closely attached to the transformer winding to realize temperature sensing. The interference spectrum generated by the first Sagnac interference ring serves as a fixed part that causes a vernier effect and is placed in a shielding box near the transformer. The broadband light source 1 is connected to the first Sagnac interference ring through a 2×2 coupler 2;

[0032] The signal acquisition unit is composed of a spectrum analyzer 6, a data acquisition card 7, a computer 8, a 1×4 coupler 9 and an optical switch 10. The sensing fiber disc 4 and the reference fiber disc 3 are connected to the 1×4 coupler 9 through the 2×2 coupler 5 and the 2×2 coupler 2 respectively. The 1×4 coupler 9 is used to divide the optical signal after the first interference generated by the first Sagnac interference ring into 4 paths, and transmit it to the next second Sagnac interference ring of each optical path as a sliding part. The optical switch 10 is located in the transmission optical path from the second Sagnac interference ring to the spectrum analyzer 6. The spectrum analyzer 6 can identify at least one complete spectrum envelope cycle. The data acquisition card 7 is used to collect and calculate the temperature change corresponding to the real-time offset of the spectrum envelope wavelength and upload it to the computer 8. The computer 8 is used to control the winding measurement point temperature required for the optical signal transmission path according to the temperature change.

[0033] The optical power of the broadband light source 1 is not less than 35 mW. The splitting ratio of the 2×2 coupler is 50:50. The splitting ratio of the 1×4 coupler 9 is 25:25:25:25. The scanning range of the spectrum analyzer 6 is 1460-1600 nm, and the wavelength resolution is 0.004 nm.

[0034] The polarization-maintaining optical fiber 11 in the sensing optical fiber disc 4 and the reference optical fiber disc 3 is wound in a disc-shaped single layer. Figure 2 The structure shown is encapsulated, the difference is that the packaging box body of the reference optical fiber disc 3 is made of SiO2 aerogel, and the packaging box body of the sensing optical fiber disc 4 is made of insulating paper laminate. The packaging box is a hollow cuboid as a whole, with square upper and lower surfaces, hollow inside, and an opening on one side, which is rectangular. The height of the packaging box is 6mm, the thickness is 1mm, and the outer side length of the box is 7cm. The width of the opening is 2mm and the length does not exceed 6.5cm, ensuring that the optical fiber disc can be directly placed in it. After the wound polarization-maintaining optical fiber 11 disc is fused with two sections of single-mode optical fiber 12 and placed in it, the inside is filled with epoxy resin to bond and seal the opening, and the joints of the two single-mode optical fibers 12 are led out. The insulating paper laminate and epoxy resin are resistant to high temperatures not less than 150°C, and the overall packaging box does not break within the pressure range of 0.1MPa~1MPa to adapt to the harsh environment of the winding. SiO2 aerogel has good thermal insulation properties to ensure the constant temperature of the reference optical fiber disc 3.

[0035] Figure 3The layout diagram of the all-fiber temperature detection device for transformer windings. The encapsulated reference fiber disc 3 is placed in a shielding box near the transformer, and the encapsulated sensing fiber disc 4 is placed close to the transformer winding as a temperature sensing contact. Four sensing fiber discs 4 are placed on one winding, and are evenly distributed on the transformer winding with a vertical interval of 15 to 20 cm. Among them, the single-mode optical fiber 12 led out from the reference fiber disc 3 is connected to the 1×4 coupler 9 and the broadband light source 1 through the two ports of the 2×2 coupler 2. The single-mode optical fiber 12 led out from the sensing fiber disc is connected to the optical switch 10 and the spectrum analyzer 6 through the two ports of the 2×2 coupler 5. After the light emitted by the broadband light source 1 enters the first Sagnac interference loop through the 2×2 coupler 2 to generate interference, the optical signal is divided into four paths through the 1×4 coupler 9, and each path enters the second Sagnac interference loop through the 2×2 coupler 5. After two interferences, the optical signal is output to the spectrum analyzer 6 through the optical switch 10. The optical switch 10 is controlled by the computer 8 to select the optical path that forms the vernier effect, corresponding to each temperature measurement point of the winding, to achieve quasi-distributed detection of the transformer winding temperature.

[0036] The working principle and use method of the present invention are as follows:

[0037] The broadband light source 1 emits light and enters the first Sagnac interference ring through the 2×2 coupler 2. The light passes through the reference fiber disk 3 wound with the polarization-maintaining fiber 11 in the clockwise and counterclockwise directions to generate an optical path difference, forming interference. The interference light enters the second Sagnac interference ring through the 2×2 coupler 5. The light also passes through the sensing fiber disk 4 wound with the polarization-maintaining fiber 11 in the clockwise and counterclockwise directions to form a second interference. The superimposed spectrum generated by the two interferences is scanned and read by the spectrum analyzer 6, collected by the data acquisition card 7, and uploaded to the computer 8. When the sensing fiber disk 4 detects a temperature change, the interference light generated by the Sagnac interference ring where it is located will shift in wavelength, while the interference light generated by the other Sagnac interference ring will remain unchanged. According to the vernier effect, the superimposed spectral envelope generated by the two interferences will shift significantly. After being scanned and read by the spectrum analyzer 6, the computer 8 controls the data acquisition card 7 to collect and calculate the real-time offset of the spectral envelope wavelength corresponding to the temperature change, thereby realizing temperature measurement.

[0038] Although the embodiments of the present invention are described in conjunction with the accompanying drawings, the patent owner may make various deformations or modifications within the scope of the attached claims. As long as they do not exceed the protection scope described in the claims of the present invention, they should be within the protection scope of the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the methods and core ideas of the present invention. The above are only preferred implementation methods of the present invention. It should be pointed out that due to the limitations of textual expression and the objective existence of infinite specific structures, ordinary technicians in this technical field can make several improvements, modifications or changes without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the inventive concept and technical solution to other occasions without improvement, should be regarded as the protection scope of the present invention.

Claims

1. A transformer winding all-fiber temperature detection device based on vernier effect, comprising a temperature sensing unit and a signal acquisition unit; characterized in that: The temperature sensing unit includes a Sagnac ring cascade, a plurality of 2×2 couplers and a broadband light source; the Sagnac ring cascade includes a first Sagnac interference ring and a second Sagnac interference ring; the first Sagnac interference ring includes a reference fiber disk, a single-mode fiber and a polarization-maintaining fiber; the second Sagnac interference ring includes a sensing fiber disk, a single-mode fiber and a polarization-maintaining fiber; the interiors of the sensing fiber disk and the reference fiber disk are respectively connected with polarization-maintaining fibers of different lengths; the interference spectrum generated by the second Sagnac interference ring serves as a sliding part causing a vernier effect, and the polarization-maintaining fiber inside the second Sagnac interference ring serves as a temperature-sensitive part that is closely attached to the transformer winding to realize temperature sensing; the interference spectrum generated by the first Sagnac interference ring serves as a fixed part causing a vernier effect and is placed in a shielding box near the transformer; the broadband light source is connected to the first Sagnac interference ring through a 2×2 coupler; The polarization-maintaining optical fiber in the reference optical fiber disk is wound in a disk-shaped single layer and placed in a packaging box made of SiO2 aerogel; the packaging boxes of the sensing optical fiber disk and the reference optical fiber disk are both hollow rectangular parallelepiped as a whole, with square upper and lower surfaces, hollow inside, and an opening on one side, which is rectangular; the height of the packaging box is 6mm, the thickness is 1mm, the side length of the box is 7cm, the width of the opening is 2mm, and the length does not exceed 6.5cm. The inside is filled with epoxy resin to bond and seal the opening; The signal acquisition unit is composed of a spectrum analyzer, a data acquisition card, a computer, a 1×4 coupler and an optical switch; the sensing optical fiber disk and the reference optical fiber disk are respectively connected to the 1×4 coupler through a 2×2 coupler; the 1×4 coupler is used to evenly divide the optical signal after the first interference generated by the first Sagnac interference ring into 4 paths, and transmit it to the next second Sagnac interference ring of each optical path as a sliding part at the same time; the optical switch is located in the transmission optical path from the second Sagnac interference ring to the spectrum analyzer; the spectrum analyzer can identify at least one complete spectrum envelope cycle; the data acquisition card is used to collect and calculate the temperature change corresponding to the real-time offset of the spectrum envelope wavelength and upload it to the computer; the computer is used to control the winding measurement point temperature required for the optical signal transmission path according to the temperature change.

2. The all-fiber temperature detection device for transformer windings based on the vernier effect according to claim 1 is characterized in that: The optical power of the broadband light source is not less than 35mW; the splitting ratio of the 2×2 coupler is 50:50; the splitting ratio of the 1×4 coupler is 25:25:25:25; the scanning range of the spectrum analyzer is 1460-1600nm, and the wavelength resolution is 0.004nm.

3. The all-fiber temperature detection device for transformer windings based on the vernier effect according to claim 1 is characterized in that: The sensing optical fiber discs are used as temperature sensing contacts and are evenly distributed on the transformer windings at vertical intervals of 15 to 20 cm.

4. The all-fiber temperature detection device for transformer windings based on the vernier effect according to claim 1 is characterized in that: Both ends of the polarization-maintaining optical fibers in the sensing optical fiber disk and the reference optical fiber disk are fused with single-mode optical fibers and lead out two optical fiber interfaces, which are used to directly connect to a 2×2 coupler and the fusion loss does not exceed 3dB.

5. The all-fiber temperature detection device for transformer windings based on the vernier effect according to claim 1 is characterized in that: The polarization-maintaining optical fibers of the sensing optical fiber disk and the reference optical fiber disk are both panda-type polarization-maintaining optical fibers, covering an operating band of 1460 to 1600 nm, and an optical fiber diameter not exceeding 15 μm to ensure low-loss fusion with a single-mode optical fiber; the length of the polarization-maintaining optical fiber wound into the reference optical fiber disk is 2.5 m, and the length of the polarization-maintaining optical fiber wound into the sensing optical fiber disk is 2.65 m to ensure that the generated superimposed spectrum can be effectively identified by a spectrum analyzer as a complete spectrum envelope period.

6. The all-fiber temperature detection device for transformer windings based on the vernier effect according to claim 1 is characterized in that: The inner diameter of the optical fiber disk wound with the polarization-maintaining optical fiber of the sensing optical fiber disk and the reference optical fiber disk is not less than 5 cm, and the outer diameter is not more than 6.5 cm, so as to ensure good transmission performance of the optical fiber.

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