Built-in acoustic-electric combined sensor of transformer

Abstract

The utility model provides a built-in acoustic-electric combined sensor of a transformer. The sensor includes: a mounting unit; the ultrahigh frequency sensing unit is arranged on the mounting unit; one end of the connecting rod is connected with the ultrahigh frequency sensing unit, and the other end is provided with an angle adjusting unit; the optical fiber ultrasonic sensing unit is arranged on the angle adjusting unit. The angle of the optical fiber ultrasonic sensing unit is adjusted through the angle adjusting unit, the detection range of the sensor is enlarged, or the detection angle is adjusted, so that the optimal angle is selected for detection, the problem that the detection data is inaccurate due to the fact that a fixed structure obtains single angle data is solved, the sensitivity of a detection system is enhanced, and the detection efficiency is improved. According to the invention, the detection accuracy is ensured, the partial discharge measurement advantages of the ultrahigh frequency sensing unit and the optical fiber ultrasonic sensing unit are combined, the simultaneous acquisition of ultrahigh frequency signals and optical fiber ultrasonic signals is realized through the joint detection of acoustic and electrical signals, and the problem that the sensitivity of single partial discharge detection is limited is solved.

Description

Technical Field

[0001] This utility model relates to the field of partial discharge detection technology for power transformers, and more specifically, to a transformer-embedded acoustic-electric combined sensor. Background Technology

[0002] Power transformers are critical equipment in power transmission and distribution systems. Large transformers are expensive, and their safe and stable operation is essential for ensuring the security of the power grid. However, transformer insulation materials age over time, leading to partial discharge problems. This can significantly negatively impact the safety and stability of the transformer, thus threatening the safe operation of the entire power grid. Therefore, partial discharge detection in transformers is a crucial task. By effectively diagnosing and identifying partial discharge problems within the transformer, potential faults can be eliminated in a timely manner, ensuring the normal operation of the transformer and the stable power supply from the grid.

[0003] Current methods for diagnosing partial discharge defects in transformers typically employ a single sensor. However, these methods can only acquire single pieces of information, such as ultra-high frequency, high frequency current, or ultrasonic data, making it difficult to perform simultaneous multi-sensor detection. Since acquiring data from a single sensor cannot provide accurate defect type identification, the effectiveness of problem diagnosis and identification is limited. Using both types of sensors simultaneously requires installing them in different locations, leading to complex sensor layouts and high installation and maintenance costs. Furthermore, the large distances between different sensors hinder synchronous data acquisition and precise positioning, affecting detection accuracy. Therefore, combined acoustic and electrical sensing detection of partial discharge within transformers is of significant importance.

[0004] To improve detection accuracy, ultrasonic and ultra-high frequency sensors are best placed inside the transformer; therefore, the built-in sensors need to ensure insulation safety. However, both ultrasonic and ultra-high frequency sensors use a fixed structure, resulting in incomplete coverage angles and the acquisition of data from only one angle, leading to inaccurate detection data. Utility Model Content

[0005] In view of this, this utility model proposes a transformer-embedded acoustic-electric combined sensor, which aims to solve the problem that the existing transformer internal partial discharge detection sensors are fixed structures that can only acquire single angle data, resulting in inaccurate detection data.

[0006] This invention proposes a transformer-embedded acoustic-electric combined sensor, comprising: a mounting unit for mounting on the transformer under test; a UHF sensing unit disposed on the mounting unit for detecting UHF signals generated by partial discharge within the transformer under test; a connecting rod, one end of which is connected to the UHF sensing unit, and the other end of which is provided with an angle adjustment unit; and a fiber optic ultrasonic sensing unit disposed on the angle adjustment unit, wherein the angle adjustment unit is used to adjust the arrangement angle of the fiber optic ultrasonic sensing unit to obtain an optimal detection angle, thereby enabling the fiber optic ultrasonic sensing unit to detect the ultrasonic signals generated by partial discharge within the transformer under test at the optimal detection angle, thus monitoring the operating status of the transformer under test based on the UHF signal and the ultrasonic signal.

[0007] Furthermore, in the aforementioned transformer-embedded acoustic-electric combined sensor, the piezoelectric self-powered unit is connected to the angle adjustment unit. The mounting unit is equipped with a piezoelectric self-powered unit, which generates an electrical signal to power the angle adjustment unit when the mounting unit vibrates with the transformer under test and applies the vibration signal to the piezoelectric self-powered unit.

[0008] Furthermore, in the aforementioned transformer-embedded acoustic-electric combined sensor, the piezoelectric self-powered unit is a cylindrical piezoelectric ceramic sheet.

[0009] Furthermore, in the aforementioned transformer-embedded acoustic-electric combined sensor, the mounting unit includes: an insulating disc; a mounting disc, one side of which is sealed to the insulating disc; and a flange, which is sealed to the other side of the mounting disc. The side of the insulating disc opposite to the mounting disc is sealed to the side of the ultra-high frequency sensing unit opposite to the connecting rod.

[0010] Furthermore, in the aforementioned transformer-embedded acoustic-electric combined sensor, one side of the insulating disk is sealed to the side of the ultra-high frequency sensing unit away from the connecting rod, the other side of the insulating disk is connected to one side of the mounting disk, the side of the mounting disk away from the insulating disk is sealed to the flange, and a wireless signal transmission unit is connected to the side of the flange away from the mounting disk.

[0011] Furthermore, in the aforementioned transformer-embedded acoustic-electric combined sensor, the connecting rod is a telescopic rod structure used to adjust the position of the fiber optic ultrasonic sensing unit inside the transformer under test.

[0012] Furthermore, in the aforementioned transformer-embedded acoustic-electric combined sensor, the connecting rod is hollow inside for threading wires, thereby enabling the fiber optic cable to be led out from the fiber optic ultrasonic sensing unit.

[0013] Furthermore, in the aforementioned transformer-embedded acoustic-electric combined sensor, the fiber optic ultrasonic sensing unit is a ring-shaped sensor probe manufactured by vacuum casting, and it is detachably connected to the angle adjustment unit.

[0014] Furthermore, in the aforementioned transformer-embedded acoustic-electric combined sensor, the angle adjustment unit is connected to a control unit for receiving ultra-high frequency signals and ultrasonic signals, and for controlling the angle adjustment unit based on the ultra-high frequency signals and ultrasonic signals, so as to control the angle adjustment unit to drive the fiber optic ultrasonic sensing unit to rotate to the optimal angle.

[0015] Furthermore, in the aforementioned transformer-embedded acoustic-electric combined sensor, a sealing ring is provided between the ultra-high frequency sensing unit and the mounting unit; a sealing ring is also provided between the connecting rod and the ultra-high frequency sensing unit.

[0016] This invention provides a transformer-embedded acoustic-electric combined sensor and a partial discharge detection method, combining the advantages of UHF and fiber optic ultrasonic sensing units for partial discharge measurement. Through the joint detection of acoustic and electrical signals, it achieves simultaneous acquisition of UHF and fiber optic ultrasonic signals, solving the problem of limited sensitivity in single partial discharge detection. The embedded structure, with the fiber optic ultrasonic sensor probe located inside the transformer, improves anti-interference capability, detection sensitivity, and the accuracy of defect localization. The UHF and fiber optic ultrasonic sensing units effectively detect partial discharges generated inside the transformer and quickly capture partial discharge signals. Compared to using fiber optic ultrasonic sensors and UHF sensors at different locations simultaneously, this method supports synchronous detection of fiber optic ultrasonic and UHF signals, exhibiting good consistency and efficiently monitoring internal transformer discharges, detecting latent defects, and diagnosing defects. The degree of insulation damage under the influence of an electric field is effectively assessed to provide early warning of faults and improve the condition-based maintenance level of transformers. The fiber optic ultrasonic sensor uses a vacuum casting method to fabricate the sensor probe, and all parts of the sensor, such as the mounting plate, insulating plate, UHF sensing unit, and fiber optic ultrasonic sensing unit, are sealed with sealing rings. After installation, the sensor becomes an integral part of the transformer, providing excellent sealing and ensuring reliable operation under high pressure and high oil temperature environments. The angle adjustment unit allows for adjustment of the angle of the fiber optic ultrasonic sensing unit, increasing the sensor's detection range or adjusting the detection angle to select the optimal angle for detection. This solves the problem that existing transformer internal partial discharge detection sensors with fixed structures can only acquire data from a single angle, resulting in inaccurate detection data. This enhances the sensitivity of the detection system and ensures the accuracy of detection. Attached Figure Description

[0017] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0018] Figure 1 This is a schematic diagram of the structure of the transformer-embedded acoustic-electric combined sensor provided in an embodiment of the present utility model;

[0019] Figure 2 A schematic diagram of the connection between the fiber optic ultrasonic sensing unit and the angle adjustment unit provided in an embodiment of this utility model;

[0020] Figure 3 A schematic diagram of the fiber optic ultrasonic sensing unit structure provided in an embodiment of this utility model. Detailed Implementation

[0021] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, embodiments and features of the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] See Figure 1 and Figure 2 The figure illustrates a preferred structure of the transformer-embedded acoustic-electric combined sensor provided in this embodiment of the present invention. As shown in the figure, the transformer-embedded acoustic-electric combined sensor includes: a mounting unit 1, an ultra-high frequency sensing unit 2, a connecting rod 3, an angle adjustment unit 4, an optical fiber ultrasonic sensing unit 5, a piezoelectric self-powered unit 6, and a control unit (not shown in the figure).

[0023] Mounting unit 1 is used to install on the transformer under test 8. Specifically, mounting unit 1 can be fixedly installed on the transformer under test 8 to integrate the built-in acoustic-electric sensor with the transformer under test 8 into a single structure. To ensure the sealing between the built-in acoustic-electric sensor and the transformer under test 8, preferably, a sealing ring is provided between mounting unit 1 and the transformer under test 8, so that the transformer under test 8 has good sealing at the location where the sensor is installed, avoiding leakage and insulation problems, and thus ensuring reliable operation of the sensor under high pressure and high oil temperature environments.

[0024] The ultra-high frequency (UHF) sensing unit 2 is mounted on the mounting unit 1 and is used to detect the UHF signal generated by partial discharge within the transformer under test 8. Specifically, it receives UHF signals from the surrounding environment, detects partial discharge based on the signal spectrum, and acquires the electromagnetic wave signal generated by the partial discharge. Specifically, the left side of the UHF sensing unit 2 is sealed to the right side of the mounting unit 1, and a sealing ring can be provided between them to further prevent leakage and insulation problems, ensuring the long-term stability and reliability of the sensor. The UHF sensing unit 2 can be a structure combining an antenna element, particularly a flat plate and a conical receiving antenna, featuring high integration, simple structure, and convenient processing. The operating bandwidth is 300MHz~1500MHz, the gain is 40dB, the noise figure NF≤3dB, the detection sensitivity is not greater than 2V / m, the dynamic detection range is not less than 60dB, the time deviation between different detection channels is <1μs, and the amplification frequency band of the used RF amplifier covers 2kHz~2GHz, with an amplifier gain >30dB within the frequency band. In this embodiment, the UHF sensing unit 2 can be placed inside the transformer under test 8.

[0025] One end of connecting rod 3 (e.g.) Figure 1 The left end shown is connected to the UHF sensing unit 2, and the other end (as shown on the left) is connected to the UHF sensing unit 2. Figure 2 An angle adjustment unit 4 is provided at the right end (as shown). Specifically, the connecting rod 3 can be a support rod to support the angle adjustment unit 4 and the fiber optic ultrasonic sensing unit 5, so that the fiber optic ultrasonic sensing unit 5 is supported inside the transformer 8 under test. In this embodiment, the left end of the connecting rod 3 is fixedly connected to the ultra-high frequency sensing unit 2, and the two are sealed together, which can be sealed with a sealing ring; the right end of the connecting rod 3 is fixedly connected to the angle adjustment unit 4, and the two are sealed together, which can be sealed with a sealing ring.

[0026] The fiber optic ultrasonic sensing unit 5 is installed in the angle adjustment unit 4. The angle adjustment unit 4 is used to adjust the arrangement angle of the fiber optic ultrasonic sensing unit 5 to obtain the optimal detection angle. This allows the fiber optic ultrasonic sensing unit 5 to detect the ultrasonic signal generated by partial discharge within the transformer under test 8 at the optimal detection angle, thereby monitoring the operating status of the transformer under test 8 based on UHF and ultrasonic signals. Specifically, the detection fiber in the fiber optic ultrasonic sensing unit 5 can be a single-mode fiber with a length of 50m. Figure 3As shown, the fiber optic ultrasonic sensing unit 5 can be a ring structure, and the sensor probe can be fabricated using vacuum casting. The diameter of the fiber ring is 30mm, and it is wound with 32 layers on the core shaft. This avoids excessive bending that would cause significant signal attenuation, while increasing the modulation amplitude of the interference light phase, giving the system higher detection sensitivity. Its operating frequency band covers 80kHz~200kHz. The probe fiber in the fiber optic ultrasonic sensing unit 5 is subjected to the pressure of the ultrasonic waves generated by partial discharge, causing a slight change in the length of this part of the fiber. This ultimately leads to a change in the interference phase of the reference light and the probe light, thereby detecting the partial discharge and acquiring the ultrasonic signal generated by the partial discharge. The bottom of the fiber optic ultrasonic sensing unit 5 (as shown) Figure 2 The left side (as shown) is connected to an angle adjustment unit 4, which can adjust the angle of the fiber optic ultrasonic sensing unit 5 to increase the sensor's detection range or adjust the detection angle to select the optimal angle for detection, thereby enhancing the sensitivity of the detection system and ensuring detection accuracy. The fiber optic ultrasonic sensing unit 5 can have five positions: first position, second position, third position, fourth position, and fifth position, corresponding to angles of 30°, 60°, 90°, 120°, and 150° between the fiber optic ultrasonic sensing unit 5 and the vertical outer shell of the transformer under test 8, respectively. To facilitate the replacement of the fiber optic ultrasonic sensing unit 5, preferably, the fiber optic ultrasonic sensing unit 5 and the angle adjustment unit 4 are connected in a detachable manner. For example, the fiber optic ultrasonic sensing unit 5 and the angle adjustment unit 4 can be connected by threads; other connection methods are also possible, and this embodiment does not impose any limitations on them.

[0027] A piezoelectric self-harvesting unit 6 can be mounted on the mounting unit 1. The piezoelectric self-harvesting unit 6 is connected to the angle adjustment unit 4. When the mounting unit 1 vibrates with the transformer under test 8 and the vibration signal is applied to the piezoelectric self-harvesting unit 6, it generates an electrical signal to power the angle adjustment unit 4. Specifically, the piezoelectric self-harvesting unit 6 can be a piezoelectric ceramic sheet. The mounting unit 1 vibrates synchronously with the transformer under test 8 so that the vibration signal is applied to the piezoelectric self-harvesting unit 6, causing it to generate an electrical signal to power components such as the control unit. In this embodiment, the piezoelectric self-harvesting unit 6 can be a cylindrical piezoelectric ceramic sheet with a base radius of 2cm and a thickness of 1cm. The resonant frequency of this size piezoelectric ceramic sheet is more compatible with the frequency of transformer vibration, allowing more electrical energy to be generated when the transformer's vibration signal is applied to the piezoelectric sheet. The piezoelectric sheet is connected to the angle adjustment unit 4 via wires and can also be connected to the control unit to provide power for angle control and the control unit.

[0028] In this embodiment, the angle adjustment unit 4 is connected to a control unit (not shown in the figure) for receiving UHF signals and ultrasonic signals, and controlling the angle adjustment unit 4 based on the UHF signals and ultrasonic signals to drive the fiber optic ultrasonic sensing unit to rotate to the optimal angle. Specifically, the control unit is connected to the angle adjustment unit 4, the UHF sensing unit 2, and the fiber optic ultrasonic sensing unit 5 respectively, for receiving the UHF signals acquired by the UHF sensing unit 2 and the ultrasonic signals acquired by the fiber optic ultrasonic sensing unit 5, and controlling the angle adjustment unit 4 based on the amplitude of the UHF signals and the amplitude of the ultrasonic signals to adjust the arrangement angle of the fiber optic ultrasonic sensing unit 5, especially the angle between the fiber optic ultrasonic sensing unit 5 and the vertical shell of the transformer under test 8.

[0029] In this embodiment, the UHF sensing unit 2 and the fiber optic ultrasonic sensing unit 5 are also connected to a wireless signal transmission unit, which is used to transmit the UHF signal acquired by the UHF sensing unit 2 and the ultrasonic signal acquired by the fiber optic ultrasonic sensing unit 5 to the remote monitoring room.

[0030] Continue to see Figure 1 The mounting unit 1 includes: an insulating plate 11, a mounting plate 12, and a flange 13; wherein, one side of the mounting plate 12 (e.g., Figure 1 The flange 13 (as shown on the right) is sealed to the insulating plate 11; the flange 13 is sealed to the other side of the mounting plate 11 (as shown on the right). Figure 1 (As shown on the left) Sealed connection, the insulating disc 11 is on the side opposite to the mounting disc 12 (as shown on the left) Figure 1 The right side shown) and the side of the UHF sensing unit 2 away from the connecting rod 3 (as shown) Figure 1 (As shown on the left) Sealed connection.

[0031] Specifically, one side of the insulating disk 11 is sealed to the side of the UHF sensing unit 2 away from the connecting rod 3, the other side of the insulating disk 11 is connected to one side of the mounting disk 12, the side of the mounting disk 12 away from the insulating disk 11 is sealed to the flange 13, and a wireless signal transmission unit can be connected to the side of the flange 13 away from the mounting disk 12.

[0032] In this embodiment, the connecting rod 3 can be a telescopic rod structure, used to adjust the position of the fiber optic ultrasonic sensing unit 5 inside the transformer under test 8. This expands the sensor's detection range and allows for selection of the optimal length for detection based on angle adjustments. Specifically, the connecting rod 3 is hollow inside for threading, enabling the fiber optic cable from the fiber optic ultrasonic sensing unit 5 to be led out. The connecting rod 3 can be a hollow telescopic rod with a bottom radius of 2cm made of XLPE. To ensure the transformer's insulation performance, the bottom radius of the cavity inside the telescopic rod is 0.5cm. The fiber optic ultrasonic sensing unit 5 extends from the ultra-high frequency sensing unit 2 into the interior of the transformer under test 8. The telescopic rod structure penetrates the transformer under test 8 to a length ranging from 5cm to 20cm, maximizing the monitoring range and improving the detection sensitivity and coverage of partial discharge events without damaging the transformer's insulation performance. The fiber optic cable of the fiber optic ultrasonic sensing unit 5 is led out through the telescopic rod structure and can be connected to an external demodulator. The sensor as a whole achieves an IP68 protection rating.

[0033] Continue to see Figure 2 The outer wall of the connecting rod 3 is provided with a carbon fiber shell 31, and the interior is provided with a connecting rod control line 32 and an optical fiber lead-out line 33. The two ends of the connecting rod control line 32 are connected to the control unit and the angle adjustment unit 4, respectively.

[0034] In this embodiment, the control unit is also used to control the transformer's built-in acoustic-electric combined sensor to perform periodic intermittent preliminary detection on the transformer under test 8, acquire the amplitude of the ultra-high frequency signal and the amplitude of the ultrasonic signal generated by partial discharge in the transformer under test 8, and compare them with a first threshold and a second threshold respectively; when the amplitude of the ultra-high frequency signal is greater than the first threshold and / or the amplitude of the ultrasonic signal is greater than the second threshold, the control unit controls the angle adjustment unit 4 to drive the fiber optic ultrasonic sensing unit 5 to rotate, so that the fiber optic ultrasonic sensing unit 5 rotates to each position in sequence, and acquires the amplitude of the ultrasonic signal generated by partial discharge in the transformer under test 8 at each position; when the amplitude of the ultrasonic signal at at least one position is greater than the second threshold, the amplitude of the ultrasonic signal at each position is compared, and the position with the largest ultrasonic signal amplitude is determined as the optimal position; the control unit controls the angle adjustment unit 4 to drive the fiber optic ultrasonic sensing unit 5 to rotate to the optimal position, and performs periodic intermittent partial discharge detection on the transformer under test at the optimal position, acquires the ultra-high frequency signal and ultrasonic signal generated by partial discharge in the transformer under test 5, and monitors the operating status of the transformer under test 5. In this embodiment, when the amplitude of the ultrasonic signal at each gear level is less than or less than the second threshold, the control unit controls the angle adjustment unit 4 to drive the fiber optic ultrasonic sensing unit to rotate to the initial gear level, and continues to perform periodic preliminary detection on the transformer under test 8 until the amplitude of the ultrasonic signal at at least one gear level is greater than the second threshold. The detection frequency of the periodic partial discharge detection is greater than the detection frequency of the periodic preliminary detection, and can be determined according to actual conditions; this embodiment does not impose any limitations on it.

[0035] In summary, the transformer-embedded acoustic-electric combined sensor provided in this embodiment combines the advantages of UHF sensing unit 2 and fiber optic ultrasonic sensing unit 5 in partial discharge measurement. Through the joint detection of acoustic and electrical signals, it achieves simultaneous acquisition of UHF and fiber optic ultrasonic signals, solving the problem of limited sensitivity in single partial discharge detection. The embedded structure, with the fiber optic ultrasonic sensing probe located inside the transformer, improves anti-interference capability, detection sensitivity, and the accuracy of defect localization. UHF sensing unit 2 and fiber optic ultrasonic sensing unit 5 can effectively detect partial discharge generated inside the transformer and quickly capture partial discharge signals. Compared to using fiber optic ultrasonic sensors and UHF sensors at different locations simultaneously, this embodiment supports synchronous detection of fiber optic ultrasonic signals and UHF signals, exhibiting good consistency and efficient monitoring. The system measures internal discharge in transformers to detect latent defects and diagnose the extent of insulation damage caused by these defects under an electric field, thereby effectively providing fault early warning and improving the condition-based maintenance level of transformers. The fiber optic ultrasonic sensor's fiber ring is vacuum-cast to create the sensor probe. Furthermore, all components of the sensor, such as the mounting plate, insulating plate, UHF sensing unit 2, and fiber optic ultrasonic sensing unit 5, are sealed with sealing rings. After installation, the sensor becomes an integral part of the transformer, providing excellent sealing and ensuring reliable operation under high pressure and high oil temperature environments. The angle adjustment unit 4 adjusts the angle of the fiber optic ultrasonic sensing unit 5 to increase the sensor's detection range or adjust the detection angle to select the optimal angle for detection, enhancing the sensitivity of the detection system and ensuring detection accuracy.

[0036] It should be noted that in the description of this utility model, the terms "upper", "lower", "left", "right", "inner", "outer", etc., indicating the direction or positional relationship are based on the direction or positional relationship shown in the drawings. This is only for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this utility model.

[0037] Furthermore, it should be noted that, in the description of this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0038] Obviously, those skilled in the art can make various modifications and variations to this utility model without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this utility model and their equivalents, this utility model also intends to include these modifications and variations.

Claims

1. A transformer-embedded acoustic-electric combined sensor, characterized in that, include: The mounting unit is used to install on the transformer under test. An ultra-high frequency sensing unit is mounted on the mounting unit and is used to detect ultra-high frequency signals generated by partial discharge in the transformer under test; The connecting rod is connected at one end to the ultra-high frequency sensing unit and at the other end to an angle adjustment unit; An optical fiber ultrasonic sensing unit is disposed in the angle adjustment unit. The angle adjustment unit is used to adjust the arrangement angle of the optical fiber ultrasonic sensing unit to obtain the optimal detection angle, so that the optical fiber ultrasonic sensing unit can detect the ultrasonic signal generated by partial discharge in the transformer under test at the optimal detection angle, thereby monitoring the operating status of the transformer under test based on ultra-high frequency signals and ultrasonic signals.

2. The transformer-embedded acoustic-electric combined sensor according to claim 1, characterized in that, The installation unit is equipped with a piezoelectric self-powered unit, which is connected to the angle adjustment unit. When the installation unit vibrates with the transformer under test and applies the vibration signal to the piezoelectric self-powered unit, it generates an electrical signal to supply power to the angle adjustment unit.

3. The transformer-embedded acoustic-electric combined sensor according to claim 2, characterized in that, The piezoelectric self-powered unit is a cylindrical piezoelectric ceramic sheet.

4. The transformer-embedded acoustic-electric combined sensor according to any one of claims 1 to 3, characterized in that, The installation unit includes: Insulating disc; Mounting plate, one side of which is sealed to the insulating plate; The flange is sealed to the other side of the mounting plate, and the side of the insulating plate opposite to the mounting plate is sealed to the side of the UHF sensing unit opposite to the connecting rod.

5. The transformer-embedded acoustic-electric combined sensor according to claim 4, characterized in that, One side of the insulating disk is sealed to the side of the UHF sensing unit away from the connecting rod, the other side of the insulating disk is connected to one side of the mounting disk, the side of the mounting disk away from the insulating disk is sealed to the flange, and a wireless signal transmission unit is connected to the side of the flange away from the mounting disk.

6. The transformer-embedded acoustic-electric combined sensor according to any one of claims 1 to 3, characterized in that, The connecting rod is a telescopic rod structure, used to adjust the position of the fiber optic ultrasonic sensing unit inside the transformer under test.

7. The transformer-embedded acoustic-electric combined sensor according to any one of claims 1 to 3, characterized in that, The connecting rod is hollow inside and is used for threading wires to bring out the optical fiber in the optical fiber ultrasonic sensing unit.

8. The transformer-embedded acoustic-electric combined sensor according to any one of claims 1 to 3, characterized in that, The fiber optic ultrasonic sensing unit is a ring-shaped sensor probe manufactured by vacuum casting, and it is detachably connected to the angle adjustment unit.

9. The transformer-embedded acoustic-electric combined sensor according to any one of claims 1 to 3, characterized in that, The angle adjustment unit is connected to a control unit, which receives ultra-high frequency signals and ultrasonic signals, and controls the angle adjustment unit based on the ultra-high frequency signals and ultrasonic signals to control the angle adjustment unit to drive the fiber optic ultrasonic sensing unit to rotate to the optimal angle.

10. The transformer-embedded acoustic-electric combined sensor according to any one of claims 1 to 3, characterized in that, A sealing ring is provided between the ultra-high frequency sensing unit and the mounting unit; A sealing ring is provided between the connecting rod and the ultra-high frequency sensing unit.

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