EFPI optical fiber sensor for monitoring partial discharge of motor

Abstract

The utility model discloses an EFPI optical fiber sensor for motor partial discharge monitoring, and relates to the field of generator stator winding insulation on-line monitoring, the EFPI optical fiber sensor comprises a package and a sensing assembly, the sensing assembly comprises an optical fiber, a vibrating diaphragm and a connecting plate, the package comprises a flexible sheath and an external installation structure, the external installation structure is a block structure, and the flexible sheath and the external installation structure are mutually connected. One end of the external installation structure is concavely provided with a coupling cavity, the other end of the external installation structure is connected with a flexible sheath, the coupling cavity is a through hole with the diameter from large to small, the small-diameter side of the coupling cavity is provided with a vibrating diaphragm, a connecting plate is fixed to the vibrating diaphragm, one end of the optical fiber extends out of the flexible sheath, and the other end of the optical fiber extends into the flexible sheath to be flush with the end face of the connecting plate. An EFPI cavity is formed among the end face of the optical fiber, the side face of the connecting plate and the end face of the vibrating diaphragm. According to the utility model, the sensor is convenient to install and fix, the coupling medium can be fully filled, the ultrasonic transmission attenuation is reduced, an all-insulation structure is adopted, extra discharge faults are avoided, and the service life of a unit and the sensor is prolonged.

Description

Technical Field

[0001] The utility model relates to the field of on-line monitoring of the insulation of generator stator windings, and particularly relates to an EFPI optical fiber sensor for monitoring partial discharge of motors. Background Art

[0002] Partial discharge of the stator winding of large generators is one of the main factors leading to insulation deterioration. During the operation of the motor, the slot opening area of the stator winding is the concentration area of electrical stress and mechanical stress. According to the statistics of generator stator winding faults, the main insulation breakdown faults of generator stator windings are mainly concentrated in the slot opening area. At present, there is no reliable monitoring method applicable to partial discharge at the slot opening.

[0003] EFPI optical fiber ultrasonic sensors have the advantages of small volume, strong anti-electromagnetic interference ability, high sensitivity, excellent insulation performance, etc. At present, they are mostly used in the partial discharge monitoring of power equipment such as transformers, GIS, and air switches. Their transmission medium is liquid or gas. If they are directly installed on the surface of stator bars, it is difficult to monitor the partial discharge signals of solid insulation media.

[0004] The Chinese patent document with the publication number CN205373872U and the publication date of July 6, 2016 discloses an optical fiber EFPI ultrasonic sensor, which includes a sensor head unit and a sensor body unit. The sensor body unit includes a sensor sheath, and the sensor head unit is arranged inside the sensor sheath. The sensor head unit includes a capillary tube, a part of the optical fiber arranged inside the capillary tube, and a sleeve bracket for fixing the optical fiber. A diaphragm for sensing ultrasonic vibration is also arranged at one end of the capillary tube. The inner surface of the diaphragm, the front end surface of the optical fiber, and the inner surface of the capillary tube jointly define a Fabry-Perot cavity. The front end surface of the optical fiber constitutes the first reflection surface of the Fabry-Perot cavity, and the inner surface of the diaphragm constitutes the second reflection surface of the Fabry-Perot cavity. This optical fiber EFPI ultrasonic sensor can achieve efficient response and acquisition of ultrasonic signals, and has high sensitivity and measurement accuracy.

[0005] However, for the technical solution with the above-mentioned publication number CN205373872U, on the one hand, when the sensor is installed, the contact area is small, which is not convenient for bonding and tying fixation. On the other hand, in the above technical solution, the diaphragm is directly arranged at the bottom, which is more vulnerable to the influence of the external environment, reducing the performance and stability of the sensor. Summary of the Utility Model

[0006] To solve the above technical problems, the utility model provides an EFPI optical fiber sensor for monitoring partial discharge of motors. By designing the EFPI structure and packaging, on-line monitoring of partial discharge at the slot opening of the stator winding can be realized, and rapid and accurate fault identification and positioning can be achieved.

[0007] The present utility model is realized by adopting the following technical solutions:

[0008] An EFPI fiber optic sensor for monitoring partial discharge of a motor, comprising a package and a sensing component. The sensing component includes an optical fiber, a diaphragm and a connecting plate. The package includes a flexible sheath and an external mounting structure. The external mounting structure is a block structure. The planar area of the coupling cavity at the bottom of the external mounting structure accounts for 20%-30% of the entire bottom area. One end of the external mounting structure is concavely provided with a coupling cavity, and the other end is connected with a flexible sheath. The coupling cavity is a through hole with a diameter decreasing from the end face of the external mounting structure far from the connecting flexible sheath to the end face connected with the flexible sheath. A diaphragm is arranged on the side with a smaller diameter of the coupling cavity. A connecting plate is fixed on the diaphragm. The cross section of the connecting plate is an annular shape. The optical fiber is arranged in the flexible sheath. One end of the optical fiber extends out of the flexible sheath, and the other end is flush with the end face of the connecting plate, so that an EFPI cavity is formed between the end face of the optical fiber and the side face of the connecting plate and the end face of the diaphragm.

[0009] A layer of optical fiber sleeve is arranged between the optical fiber and the flexible sheath.

[0010] The inner surface of the coupling cavity is smooth.

[0011] The coupling cavity, the diaphragm, the connecting plate and the optical fiber are coaxially arranged.

[0012] The tensile strength of the flexible sheath is not less than 400n / 100mm, and the compressive strength is not less than 5MPa.

[0013] The diaphragm and the connecting plate are processed into one body by MEMS technology.

[0014] The optical fiber is bonded to the diaphragm and the connecting plate by F-grade epoxy resin.

[0015] The diaphragm is a semiconductor silicon-based thin film, a quartz thin film or a graphene thin film.

[0016] The flexible sheath is made of polyamide, polyoxymethylene or polybutylene terephthalate.

[0017] The external mounting structure is made of polyamide, polyoxymethylene or polybutylene terephthalate.

[0018] Compared with the prior art, the advantages of the present utility model are as follows:

[0019] 1. In this utility model, by providing a coupling cavity on the external mounting structure, when monitoring the partial discharge ultrasonic signal of the solid insulating medium, it is beneficial to fill the coupling medium fully, reduce the ultrasonic transmission attenuation, reduce the influence of the external environment, and improve the performance and stability of the sensor. The optical fiber is arranged in the flexible sheath, which can prevent the optical fiber from breaking at the soft-hard transition section, and the setting of the flexible sheath ensures that the bending radius of the optical fiber is not less than 20 times the diameter of the optical fiber, preventing excessive attenuation of the optical signal. The external mounting structure is a block structure, forming a skirt-like structure with the coupling cavity, and the bottom plane area is larger than the plane area of the coupling cavity, increasing the contact area with the surface of the stator bar during sensor installation and facilitating bonding and tying for fixation.

[0020] 2. In this utility model, a layer of optical fiber sleeve is provided between the optical fiber and the flexible sheath. While protecting the optical fiber, it can support and fix the optical fiber, and prevent the optical fiber from being damaged or interfered by the external environment, ensuring the performance stability of the sensor.

[0021] 3. In this utility model, the coupling cavity, the diaphragm and the optical fiber are coaxial, enabling the performance of the sensor to be optimized to the greatest extent, improving the signal transmission and stability, and thus enhancing the sensitivity and accuracy of the sensor.

[0022] 4. In this utility model, a fully insulated structure design is adopted, which improves the long-term operation stability of the sensor and avoids the additional electrical influence of the sensor on high-field-strength operating devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The following will further elaborate on this utility model in conjunction with the specification drawings and specific embodiments, where:

[0024] Figure 1 is a cross-sectional schematic diagram of this utility model;

[0025] Figure 2 is a structural schematic diagram of this utility model.

[0026] Reference numerals in the drawings:

[0027] 1. Optical fiber sleeve, 2. Optical fiber, 3. Encapsulation, 4. EFPI cavity, 5. Coupling cavity, 6. Connecting plate, 7. Diaphragm, 8. Flexible sheath, 9. External mounting structure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] Embodiment 1

[0029] As the most basic embodiment of the present utility model, an EFPI fiber optic sensor for monitoring partial discharge of an electric motor includes a package 3 and a sensing component. The sensing component includes an optical fiber 2, a diaphragm 7, and a connecting plate 6. The package 3 includes a flexible sheath 8 and an external mounting structure 9. The external mounting structure 9 is a block structure. The plane area of the bottom of the external mounting structure 9 coupled to the cavity 5 accounts for 20%-30% of the entire bottom area. One end of the external mounting structure 9 is recessed to form a coupling cavity 5, and the other end is connected to a flexible sheath 8. The coupling cavity 5 is a through hole with a diameter decreasing from the end face of the external mounting structure 9 far from the connection with the flexible sheath 8 to the end face connected to the flexible sheath 8. A diaphragm 7 is provided on the side with a smaller diameter of the coupling cavity 5. A connecting plate 6 is fixed on the diaphragm 7. The cross section of the connecting plate 6 is circular. The optical fiber 2 is arranged in the flexible sheath 8. One end of the optical fiber 2 extends out of the flexible sheath 8, and the other end is flush with the end face of the connecting plate 6, so that an EFPI cavity 4 is formed between the end face of the optical fiber 2, the side face of the connecting plate 6, and the end face of the diaphragm 7.

[0030] In this embodiment, by providing a coupling cavity 5 on the external mounting structure 9, when monitoring the ultrasonic signal of partial discharge of a solid insulation medium, it is beneficial to fill the coupling medium fully, reduce the attenuation of ultrasonic wave transmission, reduce the influence of the external environment, and improve the performance and stability of the sensor; the optical fiber is arranged in the flexible sheath 8, which can prevent the optical fiber from breaking at the soft-hard transition section, and the setting of the flexible sheath 8 ensures that the bending radius of the optical fiber is not less than 20 times the diameter of the optical fiber, preventing excessive attenuation of the optical signal; the external mounting structure 9 is a block structure, forming a skirt-like structure with the coupling cavity 5, and the bottom plane area is larger than the plane area of the coupling cavity 5, which increases the contact area with the surface of the stator bar during the installation of the sensor, facilitating bonding and tying for fixation.

[0031] Embodiment 2

[0032] As a preferred embodiment of the present utility model, an EFPI fiber optic sensor for monitoring partial discharge of a motor includes a package 3 and a sensing component. The sensing component includes an optical fiber 2, a diaphragm 7, and a connecting plate 6. The package 3 includes a flexible sheath 8 and an external mounting structure 9. The external mounting structure 9 is a block structure. The planar area of the bottom of the external mounting structure 9 coupled to the cavity 5 accounts for 20%-30% of the entire bottom area. One end of the external mounting structure 9 is recessed to form a coupling cavity 5, and the other end is connected to the flexible sheath 8. The coupling cavity 5 is a through hole with a diameter that decreases from the end face of the external mounting structure 9 far from the connection with the flexible sheath 8 to the end face connected to the flexible sheath 8. A diaphragm 7 is provided on the side with a smaller diameter of the coupling cavity 5. A connecting plate 6 is fixed on the diaphragm 7. The cross section of the connecting plate 6 is an annular shape. The optical fiber 2 is arranged in the flexible sheath 8. One end of the optical fiber 2 extends out of the flexible sheath 8, and the other end is flush with the end face of the connecting plate 6, so that an EFPI cavity 4 is formed between the end face of the optical fiber 2 and the side face of the connecting plate 6 and the end face of the diaphragm 7.

[0033] A layer of optical fiber sleeve is provided between the optical fiber 2 and the flexible sheath 8. While protecting the optical fiber 2, it can support and fix the optical fiber 2 and prevent the optical fiber 2 from being damaged or interfered by the external environment, ensuring the performance stability of the sensor.

[0034] The inner surface of the coupling cavity 5 is smooth, and the size of the coupling cavity 5 can be adjusted according to the filled coupling medium. The inside of the coupling cavity 5 is smooth to ensure that the coupling medium can be filled completely.

[0035] The coupling cavity 5, the diaphragm 7, and the optical fiber 2 are coaxially arranged, and the performance of the sensor can be optimized to the greatest extent, which can ensure the transmission and stability of the signal, thereby improving the sensitivity and accuracy of the sensor.

[0036] Embodiment 3

[0037] As the best embodiment of the present utility model, an EFPI fiber optic sensor for monitoring partial discharge of an electric motor includes a package 3 and a sensing assembly. The sensing assembly includes an optical fiber 2, a diaphragm 7 and a connecting plate 6. The package 3 includes a flexible sheath 8 and an external mounting structure 9. The external mounting structure 9 is a block structure. The planar area of the bottom of the external mounting structure 9 coupled to the cavity 5 accounts for 20%-30% of the entire bottom area. One end of the external mounting structure 9 is recessed to form a coupling cavity 5, and the other end is connected to the flexible sheath 8. The coupling cavity 5 is a through hole with a diameter that decreases from the end face of the external mounting structure 9 far from the connection with the flexible sheath 8 to the end face connected to the flexible sheath 8. A diaphragm 7 is provided on the side with a smaller diameter of the coupling cavity 5. A connecting plate 6 is fixed on the diaphragm 7. The cross section of the connecting plate 6 is an annular shape. The optical fiber 2 is arranged in the flexible sheath 8. One end of the optical fiber 2 extends out of the flexible sheath 8, and the other end is flush with the end face of the connecting plate 6, so that an EFPI cavity 4 is formed between the end face of the optical fiber 2 and the side face of the connecting plate 6 and the end face of the diaphragm 7.

[0038] A layer of optical fiber sleeve is provided between the optical fiber 2 and the flexible sheath 8. While protecting the optical fiber 2, it can support and fix the optical fiber 2 and prevent the optical fiber 2 from being damaged or interfered by the external environment, ensuring the performance stability of the sensor.

[0039] The inner surface of the coupling cavity 5 is smooth, and the size of the coupling cavity 5 can be adjusted according to the filled coupling medium. The inside of the coupling cavity 5 is smooth to ensure that the coupling medium can be filled completely.

[0040] The coupling cavity 5, the diaphragm 7 and the optical fiber 2 are coaxially arranged, and the performance of the sensor can be optimized to the greatest extent, which can ensure the transmission and stability of the signal, thereby improving the sensitivity and accuracy of the sensor.

[0041] The tensile strength of the flexible sheath 8 is not less than 400n / 100mm, and the compressive strength is not less than 5MPa.

[0042] The diaphragm 7 and the connecting plate 6 are processed into one body by MEMS technology.

[0043] The optical fiber 2 is bonded to the diaphragm 7 and the connecting plate 6 by F-grade epoxy resin.

[0044] The package 3 and the sensing assembly are formed into one body by potting or bonding with F-grade epoxy resin.

[0045] The diaphragm 7 includes but is not limited to non-metallic films such as semiconductor silicon-based films, quartz films, graphene films, etc. The flexible sheath 8 and the external mounting structure 9 are made of polymer materials including but not limited to PA, POM, PBT, etc.

[0046] In this embodiment, by providing a coupling cavity 5 on the external mounting structure 9, when monitoring the ultrasonic signal of partial discharge in solid insulating media, it is beneficial to fill the coupling media fully, reducing the attenuation of ultrasonic wave transmission; the optical fiber 2 is arranged in the flexible sheath 8, which can prevent the optical fiber 2 from breaking at the soft-hard transition section, and the setting of the flexible sheath 8 ensures that the bending radius of the optical fiber is not less than 20 times the fiber diameter, preventing excessive attenuation of the optical signal, and adopting a fully insulated structure design, improving the long-term operation stability of the sensor and avoiding the additional electrical influence of the sensor on high-field-strength operating devices.

Claims

1. An EFPI optical fiber sensor for monitoring partial discharge of a motor, comprising a package (3) and a sensor component, characterized in that: The sensing component comprises an optical fiber (2), a diaphragm (7) and a connecting plate (6); the package (3) comprises a flexible sheath (8) and an external mounting structure (9); the external mounting structure (9) is a block structure; the plane area of ​​the coupling cavity (5) at the bottom of the external mounting structure (9) accounts for 20%-30% of the entire bottom area; one end of the external mounting structure (9) is concavely provided with the coupling cavity (5) and the other end is connected to the flexible sheath (8); the coupling cavity (5) is located away from the external mounting structure (9) and connected to the flexible sheath (8). ) to the end face connected to the flexible sheath (8), and the diameter of the through hole is from large to small, the side with a small diameter of the coupling cavity (5) is provided with a diaphragm (7), a connecting plate (6) is fixed on the diaphragm (7), the cross section of the connecting plate (6) is circular, the optical fiber is arranged in the flexible sheath (8), one end of the optical fiber (2) extends out of the flexible sheath (8), and the other end is flush with the end face of the connecting plate (6), so that an EFPI cavity (4) is formed between the end face of the optical fiber (2) and the side face of the connecting plate (6) and the end face of the diaphragm (7).

2. The EFPI optical fiber sensor for monitoring partial discharge of a motor according to claim 1, characterized in that: A layer of optical fiber sleeve is provided between the optical fiber (2) and the flexible sheath (8).

3. The EFPI optical fiber sensor for monitoring partial discharge of a motor according to claim 2, characterized in that: The inner surface of the coupling cavity (5) is smooth.

4. The EFPI optical fiber sensor for monitoring partial discharge of a motor according to claim 3, characterized in that: The coupling cavity (5), the diaphragm (7) and the optical fiber (2) are coaxially arranged.

5. The EFPI optical fiber sensor for monitoring partial discharge of a motor according to claim 2, characterized in that: The tensile strength of the flexible sheath (8) is not less than 400n / 100mm, and the compressive strength is not less than 5MPa.

6. The EFPI optical fiber sensor for monitoring partial discharge of a motor according to claim 1, characterized in that: The diaphragm (7) and the connecting plate (6) are processed into one piece through the MEMS process.

7. The EFPI optical fiber sensor for monitoring partial discharge of a motor according to claim 2, characterized in that: The optical fiber (2) is bonded to the diaphragm (7) and the connecting plate (6) by means of F-class epoxy resin.

8. The EFPI optical fiber sensor for monitoring partial discharge of a motor according to claim 1, characterized in that: The diaphragm (7) is a semiconductor silicon-based film, a quartz film or a graphene film.

9. The EFPI optical fiber sensor for monitoring partial discharge of a motor according to claim 1, characterized in that: The flexible sheath (8) is made of polyamide, polyoxymethylene or polybutylene terephthalate.

10. The EFPI optical fiber sensor for motor partial discharge monitoring according to claim 1, characterized in that: The external mounting structure (9) is made of polyamide, polyoxymethylene or polybutylene terephthalate.

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