Ultrasonic-based non-contact monitoring system and method for transformer oil level

Abstract

This invention relates to the field of ultrasonic oil level monitoring technology, and more particularly to a non-contact transformer oil level monitoring system and method based on ultrasound. A fixed cylinder is connected to the inner bottom of the oil tank, with the top of the fixed cylinder flush with the bottom of the oil tank. A float is positioned directly above the fixed cylinder and can move up and down with the oil level. The float achieves oil level following through buoyancy. A connecting pipe is connected to the bottom of the fixed cylinder, with the other end of the connecting pipe extending into the inner bottom of the oil tank. A filter screen is fixedly connected to the inner bottom of the oil tank, covering the inlet of the connecting pipe. A rotating shaft is rotatably connected to the inner side of the fixed cylinder, with a blade fixedly connected to the outer side of the top of the rotating shaft. An ultrasonic probe, which is an ultrasonic receiver, is embedded in the inner side of the top of the rotating shaft. This invention can accurately obtain the ultrasonic velocity inside the oil tank at that moment using the time difference method and oil flow velocity, eliminating temperature compensation errors while also eliminating interference from impurities in the oil on the sound velocity.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic oil level monitoring technology, specifically to a non-contact transformer oil level monitoring system and method based on ultrasound. Background Technology

[0002] Oil level is a crucial parameter for fault monitoring in oil-immersed transformers. Timely detection of abnormal conditions can effectively reduce the incidence of oil-related transformer failures. However, current transformer oil level monitoring devices suffer from low measurement accuracy and weak anti-interference capabilities. For example, relying on readings from oil level gauges to determine oil level is susceptible to the experience of the inspectors, making the accuracy of the data uncertain. Furthermore, due to long-term transformer operation, oil level gauges may experience water ingress, corrosion, or contamination of the viewing window, leading to false oil level readings and making accurate oil level determination difficult. Due to its high frequency, good directionality, and strong penetrating power, ultrasound can be used in fields such as ranging and non-destructive testing, depending on its propagation speed. However, current transformer oil level monitoring technologies all have varying degrees of defects. For example, transformer oil temperature varies greatly due to its own load conditions and the ambient temperature. Meanwhile, the sound velocity of the medium is closely related to temperature. Studies have shown that transformer oil temperature and sound velocity exhibit an approximately linear relationship with a slope of about 4.04, indicating that for every 1°C increase in oil temperature, the sound velocity increases by about 4 m / s.

[0003] When measuring the oil level of a transformer using ultrasound, the temperature can be used to correct for the speed of sound based on the above relationship, which is beneficial to further improving the measurement accuracy of the monitoring device. However, impurities such as air bubbles, fiber particles, and metal particles are often present in the oil tank. The quantity, size, and location of these impurities will affect the results of ultrasonic ranging to varying degrees. In this invention, a single ultrasonic generator and ultrasonic receiver are used to generate a differential flow velocity in the transformer oil within the tank. Based on the generated flow velocity, impurities in the oil flow of the measurement section are removed. Since the sound velocity and the oil flow velocity can be superimposed, this invention uses the time difference method and the oil flow velocity to accurately obtain the ultrasonic velocity in the tank at this time. This can eliminate temperature compensation errors and eliminate the interference of impurities in the oil on the sound velocity, thereby further improving the accuracy of oil level measurement via ultrasonic waves.

[0004] Therefore, a non-contact transformer oil level monitoring system and method based on ultrasound is proposed to address the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a non-contact monitoring system and method for transformer oil level based on ultrasound. It uses the time difference method and oil flow velocity to accurately obtain the ultrasonic velocity in the oil tank at this time, which can eliminate temperature compensation error and eliminate the interference of impurities in the oil on the sound velocity. The accuracy of oil level measurement by ultrasound can be further improved.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a non-contact transformer oil level monitoring system based on ultrasound, comprising an oil tank and a float plate. A breathing capsule is installed on the inner side of the top of the oil tank, and a fixed cylinder is connected to the inner side of the bottom of the oil tank. The top of the fixed cylinder is flush with the bottom of the oil tank. The float plate is set on the upper side of the fixed cylinder and can move up and down with the oil level. The float plate achieves oil level following through buoyancy. The bottom end of the fixed cylinder is connected to a connecting pipe, and the other end of the connecting pipe extends into the inner side of the bottom end of the oil tank. A filter screen is fixedly connected to the inner side of the bottom end of the oil tank, and the filter screen covers the inlet of the other end of the connecting pipe. A rotating shaft is rotatably connected to the inner side of the fixed cylinder. A paddle is fixedly connected to the outer side of the top of the rotating shaft. An ultrasonic probe is embedded in the inner side of the top of the rotating shaft. This ultrasonic probe is an ultrasonic receiver. A fixed shaft is fixedly connected to the bottom end of the floating plate. An ultrasonic probe is also embedded in the inner side of the bottom end of the fixed shaft. The ultrasonic probe is an ultrasonic generator. A rotor-type flow meter is rotatably connected to the outer side of the bottom end of the fixed shaft. This invention can accurately obtain the ultrasonic speed in the oil tank at this time using the time difference method and oil flow velocity. It can eliminate temperature compensation error and eliminate the interference of impurities in the oil on the sound speed. The accuracy of oil level measurement by ultrasonic waves can be further improved. By generating oil velocity, impurities in the detection section of the oil (the oil between the two ultrasonic probes) are removed. On the other hand, the sound wave velocity under real static conditions can be obtained using the time difference method. Compared with the temperature approximation compensation in the existing technology, this method can eliminate errors from two dimensions, thereby further increasing the accuracy of oil level measurement and further reducing interference. When the blades rotate, a negative pressure is generated on the underside of the blades, which draws the oil from the tank. The oil is filtered through the filter screen and then discharged through the connecting pipe and the fixed cylinder, making the oil in the detection section clean. Even if the oil between the two ultrasonic probes is clean, the rotor flow meter measures the oil flow velocity c. At this time, the distance between the two ultrasonic probes is k = (vc)t1, where t1 is the time when the ultrasonic receiver receives the ultrasonic generator when there is oil velocity. When the blades rotate, the oil is filtered through the filter screen and discharged through the fixed cylinder. For the ultrasonic generator on the upper side, the direction of the oil flow is opposite to that of the sound wave emitted. Because the speed of sound can be vector-superimposed with the velocity of the transmission medium, that is, when there is oil flow, the actual speed of the sound wave is vc. Then, the transmission time t1 of the sound wave between the ultrasonic receiver and the ultrasonic generator is obtained through the ultrasonic receiver and the ultrasonic generator, and k = (vc)t1 can be obtained. After the propeller stops and the oil settles, the distance between the two ultrasonic probes is k=vt2, where t2 is the time it takes for the ultrasonic receiver to receive the ultrasonic generator when there is no oil velocity. The specific value of the ultrasonic propagation speed v in static oil under the current environment is calculated by (vc)t1= vt2, and then the size of the distance k between the two ultrasonic probes is obtained, so as to achieve accurate measurement of oil level. At this time, the oil level is k+mn, where m is the distance from the surface of the ultrasonic receiver to the float plate, and n is the distance from the ultrasonic generator to the inner side of the bottom of the oil tank.

[0007] In a preferred embodiment of the ultrasonic-based non-contact transformer oil level monitoring system of the present invention, the filter mesh is hemispherical and multi-layered. The filter mesh is used to filter impurities such as air bubbles, fiber particles, and metal particles in the detection section. As a preferred embodiment of the ultrasonic-based non-contact transformer oil level monitoring system of the present invention, an annular groove is provided on the inner side of the fixed cylinder, a sliding cylinder is slidably connected to the inner side of the groove, the top end of the sliding cylinder is fixedly connected to the bottom end of the float plate, and an outlet is provided at the top end of the sliding cylinder for discharging the upward oil flow.

[0008] The inner sides of the sliding cylinder and the fixed cylinder form a channel for oil flow. This invention slides the sliding cylinder and the fixed cylinder together to form a continuous "straight cylinder". Under the effect of the "straight cylinder", the oil flow velocity inside the sliding cylinder and the oil flow velocity inside the fixed cylinder can be made to be close to the same. To avoid large velocity differences between the upper and lower parts of the detection section, which could affect the accuracy of the measurement; In a preferred embodiment of the ultrasonic-based non-contact transformer oil level monitoring system of the present invention, the density of the slide is close to that of the oil, and the float plate can always drive the slide to move up and down with the oil.

[0009] In a preferred embodiment of the ultrasonic-based non-contact transformer oil level monitoring system of the present invention, the thickness of the groove is greater than the thickness of the slide cylinder, and the slide cylinder is slidably connected to the inner side of the groove.

[0010] By using a sliding connection to reduce the gap between the sliding cylinder and the fixed cylinder, the interference of oil flow velocity is further reduced; As a preferred embodiment of the ultrasonic-based non-contact transformer oil level monitoring system of the present invention, the diameter difference between the inner side of the sliding cylinder and the inner side of the fixed cylinder is 1-3mm. By reducing the diameter difference, the interference of oil flow velocity is further reduced, so that the oil flow velocity inside the sliding cylinder and the oil flow velocity inside the fixed cylinder are approximately the same. In a preferred embodiment of the ultrasonic-based non-contact transformer oil level monitoring system of the present invention, an electric push rod is fixedly connected to the outside of the fixed cylinder, and the movable end of the electric push rod extends into the inside of the slide groove and can abut against the slide cylinder.

[0011] In this invention, when the oil flow is generated, the float will move upward under the thrust of the oil flow. This invention sets up an electric push rod. When the electric push rod is detected, the movable end of the electric push rod extends. By pressing the movable end of the electric push rod against the slide cylinder, the float is prevented from drifting under the action of the upflow. At the same time, the slide cylinder can also limit the float and prevent the slide cylinder from shifting laterally. After the detection is completed, the movable end of the electric push rod can be retracted, so that the float can continue to move with the oil flow. In a preferred embodiment of the ultrasonic-based non-contact transformer oil level monitoring system of the present invention, a second controller is fixedly connected to the top of the oil tank. The signal line of the second controller passes through the breathing capsule and the float plate and is connected to the ultrasonic probe on the upper side. The signal line is used to realize signal transmission and power supply.

[0012] As a preferred embodiment of the ultrasonic-based non-contact transformer oil level monitoring system of the present invention, a hub motor is rotatably connected to the bottom end of the fixed cylinder via a shaft. A seal is provided at the connection between the shaft and the inner side of the bottom end of the fixed cylinder. After the shaft extends out of the inner side of the bottom end of the fixed cylinder, a gear is fixedly connected to its outer side. A gear ring is also installed on the outer side of the hub motor. The gear ring on the outer side of the hub motor meshes with the gear. When the hub motor rotates, the blades will rotate synchronously. In this invention, the blades rotate in the following way: when the hub motor rotates, it drives the shaft to rotate through the gear ring and gears. As the shaft rotates, the blades will rotate accordingly.

[0013] A first controller is fixedly connected to the bottom of the fixed cylinder. The first controller and the second controller are connected by a signal line to achieve communication. A connecting pipe is fixedly connected to the bottom of the first controller. A conductive slip ring is fixedly connected to the other end of the connecting pipe. The signal line between the conductive slip ring and the first controller is set inside the connecting pipe. The conductive slip ring is slidably connected to the bottom of the rotating shaft to achieve electrical communication during rotation.

[0014] The conductive slip ring in this invention is used to realize the rotational connection of signals and electricity, which is existing technology and will not be elaborated further here.

[0015] The steps of the ultrasonic-based non-contact monitoring method for transformer oil level are as follows: Step 1: When the blades rotate, the oil in the tank is drawn out. After being filtered by the filter screen, the oil is discharged through the fixed cylinder. This cleans the oil in the detection section and creates a flow velocity in the detection section. The rotor flow meter measures the oil flow velocity c. At this time, the distance between the two ultrasonic probes is k = (vc)t1. The ultrasonic generator emits ultrasonic waves, where t1 is the time it takes for the ultrasonic receiver to receive the ultrasonic generator when there is oil velocity. Step 2: After the propeller stops and the oil settles down, the ultrasonic generator emits ultrasonic waves again. The distance between the two ultrasonic probes is k=vt2, where t2 is the time it takes for the ultrasonic receiver to receive the ultrasonic generator when there is no oil flow. Step 3: Calculate the specific value of the ultrasonic propagation speed v in static oil under the current environment using (vc)t1= vt2. Then, substitute this specific value into Step 2 to obtain the distance k between the two ultrasonic probes, thus achieving accurate measurement of the oil level. The oil level at this time is k+mn, where m and n are constants. m is the distance from the surface of the ultrasonic receiver to the float, and n is the distance from the ultrasonic generator to the inner side of the bottom of the oil tank.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. This ultrasonic-based non-contact transformer oil level monitoring system can accurately obtain the ultrasonic velocity in the oil tank at this time by using the time difference method and oil flow velocity. It can eliminate temperature compensation error and eliminate the interference of impurities in the oil on the sound velocity. The accuracy of oil level measurement by ultrasonic waves can be further improved. 2. This ultrasonic-based non-contact transformer oil level monitoring system removes impurities from the detection section of the oil (the oil between two ultrasonic probes) by generating oil velocity. It also obtains the sound wave velocity under real static conditions using the time-difference method. Compared with the temperature approximation compensation in the existing technology, it can eliminate errors from two dimensions, thereby further increasing the accuracy of oil level measurement and further reducing interference. 3. In this ultrasonic-based non-contact transformer oil level monitoring system, when the blades rotate, a negative pressure is generated on the underside of the blades, which draws oil from the oil tank. The oil is filtered through a filter screen and then discharged through a connecting pipe and a fixed cylinder, keeping the oil in the detection section clean. This ensures that the oil between the two ultrasonic probes is clean, and the rotor velocity meter measures the oil flow velocity c. At this time, the distance between the two ultrasonic probes is k = (vc)t1, where t1 is the time it takes for the ultrasonic receiver to receive the ultrasonic generator when there is oil velocity. 4. This ultrasonic-based non-contact transformer oil level monitoring system works as follows: When the blades rotate, the oil is filtered through the filter screen and discharged through the fixed cylinder. For the ultrasonic generator on the upper side, the direction of the oil flow is opposite to that of the sound wave emitted. Since the speed of sound can be vector-superimposed with the velocity of the transmission medium, the actual speed of the sound wave is vc when there is oil flow. Then, the transmission time t1 of the sound wave between the ultrasonic receiver and the ultrasonic generator is obtained through the ultrasonic receiver and the ultrasonic generator. This gives k = (vc)t1. After the blades stop and the oil returns to calm, the distance between the two ultrasonic probes is k = vt2, where t2 is the time when the ultrasonic receiver receives the ultrasonic generator when there is no oil flow. The specific value of the ultrasonic propagation speed v in the static oil under the current environment is calculated by (vc)t1 = vt2, and then the size of the distance k between the two ultrasonic probes is obtained, thus achieving accurate measurement of the oil level. The oil level at this time is k + mn, where m is the distance from the surface of the ultrasonic receiver to the float plate, and n is the distance from the ultrasonic generator to the inner side of the bottom of the oil tank.

[0017] 5. In this ultrasonic-based non-contact transformer oil level monitoring system, the inner sides of the sliding cylinder and the fixed cylinder form a channel for oil flow. This invention slides the sliding cylinder and the fixed cylinder to form a continuous "straight cylinder". Under the effect of the "straight cylinder", the oil flow velocity inside the sliding cylinder and the oil flow velocity inside the fixed cylinder can be made close to the same, avoiding a large flow velocity difference between the upper and lower positions of the detection section, which would affect the accuracy of the measurement. 6. In this ultrasonic-based non-contact transformer oil level monitoring system, because the float plate will rise under the thrust of the oil flow when the oil flow is generated, the present invention sets up an electric push rod. During detection, the movable end of the electric push rod extends and presses against the slide cylinder to prevent the float plate from drifting under the action of the rising flow. At the same time, the slide cylinder can also limit the float plate and prevent the slide cylinder from shifting laterally. After the detection is completed, the movable end of the electric push rod can be retracted, so that the float plate can continue to move with the oil flow. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall appearance and structure of the present invention; Figure 2 This is a schematic diagram of the internal structure of the fuel tank of the present invention when it is cut open; Figure 3 This is a schematic diagram of the external structure of the fixed cylinder and the sliding cylinder of the present invention; Figure 4 This is a schematic diagram of the internal structure of the present invention, with both the fixed cylinder and the sliding cylinder cut open. Figure 5 For the present invention Figure 4 A schematic diagram of the structure at point A; Figure 6 For the present invention Figure 4 A schematic diagram of the structure at point B; Figure 7 This is a schematic diagram of the structure of the outlet and the inner chute of the present invention; Figure 8 This is a schematic diagram of the structure of the blade and its central ultrasonic probe of the present invention; Figure 9 This is a schematic diagram of the structure of the fixed shaft and the ultrasonic probe at its bottom end of the present invention.

[0019] In the diagram: 1. Oil tank; 2. Breather connector; 3. Gas relay connector; 4. Oil drain valve; 5. Fixed cylinder; 51. Slide groove; 6. First controller; 7. Conductive slip ring; 8. Rotary shaft; 9. Connecting pipe; 10. Second controller; 11. Signal line; 12. Filter screen; 13. Slide cylinder; 131. Outlet; 14. Breathing capsule; 15. Electric push rod; 16. Rotor flow meter; 17. Blade; 18. Ultrasonic probe; 19. Gear; 20. Seal; 21. Hub motor; 22. Float; 23. Fixed shaft. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1, please refer to Figures 1-5 , Figure 7 , Figure 8 and Figure 9 The present invention provides a technical solution: The ultrasonic-based non-contact transformer oil level monitoring system includes an oil tank 1 and a float 22. A breathing capsule 14 is installed on the inner side of the top of the oil tank 1, and a fixed cylinder 5 is connected to the inner side of the bottom of the oil tank 1. The top of the fixed cylinder 5 is flush with the bottom of the oil tank 1. The float 22 is located directly above the fixed cylinder 5 and can move up and down with the oil level. The float 22 achieves oil level following through buoyancy. Among them, the bottom of the oil tank 1 is also connected to the gas relay connecting pipe 3 and the oil drain valve 4. The inside of the breathing capsule 14 is connected to the breathing apparatus connecting pipe 2 to realize "breathing" during space compensation. These are all existing structures in existing products and will not be elaborated further here. The bottom end of the fixed cylinder 5 is connected to a connecting pipe 9, and the other end of the connecting pipe 9 extends into the inner side of the bottom end of the oil tank 1. A filter screen 12 is fixedly connected to the inner side of the bottom end of the oil tank 1, and the filter screen 12 covers the inlet of the other end of the connecting pipe 9. A rotating shaft 8 is rotatably connected to the inner side of the fixed cylinder 5. A paddle 17 is fixedly connected to the outer side of the top end of the rotating shaft 8. An ultrasonic probe 18 is embedded in the inner side of the top end of the rotating shaft 8. The ultrasonic probe 18 is an ultrasonic receiver. A fixed shaft 23 is fixedly connected to the bottom end of the floating plate 22. An ultrasonic probe 18 is also embedded in the inner side of the bottom end of the fixed shaft 23. The ultrasonic probe 18 is an ultrasonic generator. A rotor-type flow meter 16 is rotatably connected to the outer side of the bottom end of the fixed shaft 23. This invention can accurately obtain the ultrasonic speed in the oil tank at this time using the time difference method and oil flow velocity. It can eliminate temperature compensation error and eliminate the interference of impurities in the oil on the sound speed. The accuracy of oil level measurement by ultrasonic waves can be further improved. By generating oil velocity, impurities in the detection section of the oil are removed, which is the oil between the two ultrasonic probes 18. On the other hand, the sound wave velocity under real static conditions can be obtained by using the time difference method. Compared with the temperature approximation compensation in the existing technology, the error can be eliminated from two dimensions, thereby further increasing the accuracy of oil level measurement and further reducing interference. When the blade 17 rotates, a negative pressure is generated on the lower side of the blade 17, which draws the oil from the oil tank 1. The oil is filtered by the filter screen 12 and then discharged through the connecting pipe 9 and the fixed cylinder 5, making the oil in the detection section clean. Even if the oil between the two ultrasonic probes 18 is clean, the rotor flow meter 16 measures the oil flow velocity c. At this time, the distance between the two ultrasonic probes 18 is k = (vc)t1, where t1 is the time when the ultrasonic receiver receives the ultrasonic generator when there is oil velocity. When the blade 17 rotates, the oil is filtered through the filter screen 12 and discharged through the fixed cylinder 5. For the ultrasonic generator on the upper side, the direction of the oil flow is opposite to that of the sound wave emitted. Because the speed of sound can be vector-superimposed with the speed of the transmission medium, that is, when there is oil flow, the actual speed of the sound wave is vc. Then, the transmission time t1 of the sound wave between the ultrasonic receiver and the ultrasonic generator is obtained through the ultrasonic receiver and the ultrasonic generator, and k = (vc)t1 can be obtained. After the propeller 17 stops and the oil returns to calm, the distance between the two ultrasonic probes 18 is k=vt2, where t2 is the time when the ultrasonic receiver receives the ultrasonic generator when there is no oil velocity. The specific value of the propagation speed v of the ultrasonic wave in the static oil under the current environment is calculated by (vc)t1= vt2, and then the size of the distance k between the two ultrasonic probes (18) is obtained, so as to realize the accurate measurement of the oil level. The oil level at this time is k+mn, where m is the distance from the surface of the ultrasonic receiver to the float 22, and n is the distance from the ultrasonic generator to the inner side of the bottom of the oil tank 1.

[0022] Example 2 is a further improvement upon Example 1. Please refer to Example 1. Figures 1-9The filter mesh 12 is hemispherical and multi-layered. The filter mesh 12 is used to filter impurities such as air bubbles, fiber particles, and metal particles in the detection section. Specifically, an annular groove 51 is provided on the inner side of the fixed cylinder 5, and a sliding cylinder 13 is slidably connected to the inner side of the groove 51. The top end of the sliding cylinder 13 is fixedly connected to the bottom end of the float plate 22, and an outlet 131 is provided at the top end of the sliding cylinder 13 for discharging the upward oil flow.

[0023] The inner sides of the sliding cylinder 13 and the fixed cylinder 5 form a channel for oil flow. The present invention slides the sliding cylinder 13 and the fixed cylinder 5 to form a continuous "straight cylinder". Under the effect of the "straight cylinder", the oil flow velocity inside the sliding cylinder 13 and the oil flow velocity inside the fixed cylinder 5 can be made to be close to the same. To avoid large velocity differences between the upper and lower parts of the detection section, which could affect the accuracy of the measurement; Specifically, the density of the slide 13 is close to that of the oil, and the float 22 can always drive the slide 13 to move up and down with the oil.

[0024] Specifically, the thickness of the groove 51 is greater than the thickness of the cylinder 13, and the cylinder 13 is slidably connected to the inner side of the groove 51.

[0025] The gap between the sliding cylinder 13 and the fixed cylinder 5 is reduced by using a sliding connection, which further reduces the interference of oil flow velocity. Specifically, in this invention, the diameter difference between the inner side of the slide cylinder 13 and the inner side of the fixed cylinder 5 is 1-3mm. By reducing the diameter difference, the interference of oil flow velocity is further reduced, so that the oil flow velocity inside the slide cylinder 13 and the oil flow velocity inside the fixed cylinder 5 are close to the same. Specifically, an electric push rod 15 is fixedly connected to the outside of the fixed cylinder 5. The movable end of the electric push rod 15 extends into the inside of the slide groove 51 and can abut against the slide cylinder 13.

[0026] In this invention, when the oil flow is generated, the float 22 will move upward under the thrust of the oil flow. This invention sets up an electric push rod 15. When the electric push rod 15 is detected, the movable end of the electric push rod 15 extends. By making the movable end of the electric push rod 15 press against the slide cylinder 13, the float 22 is prevented from drifting under the action of the upflow. At the same time, the slide cylinder 13 can also limit the float 22 and prevent the slide cylinder 13 from shifting laterally. After the detection is completed, the movable end of the electric push rod 15 can be retracted, so that the float 22 can continue to move with the oil flow. Specifically, a second controller 10 is fixedly connected to the top of the fuel tank 1. The signal line 11 of the second controller 10 passes through the breathing capsule 14 and the float 22 and is connected to the ultrasonic probe 18 on the upper side. The signal line 11 is used to realize signal transmission and power supply.

[0027] Specifically, a hub motor 21 is rotatably connected to the bottom end of the fixed cylinder 5 via a shaft. A seal 20 is provided at the connection between the rotating shaft 8 and the inner side of the bottom end of the fixed cylinder 5. After the rotating shaft 8 extends out of the inner side of the bottom end of the fixed cylinder 5, a gear 19 is fixedly connected to its outer side. A gear ring is also installed on the outer side of the hub motor 21. The gear ring on the outer side of the hub motor 21 meshes with the gear 19. When the hub motor 21 rotates, the blade 17 will rotate synchronously. In this invention, the blade 17 rotates in the following way: when the hub motor 21 rotates, it drives the rotating shaft 8 to rotate through the gear ring and gear 19. As the rotating shaft 8 rotates, the blade 17 will rotate accordingly.

[0028] The bottom end of the fixed cylinder 5 is fixedly connected to the first controller 6. The first controller 6 and the second controller 10 are connected by a signal line to realize communication. The bottom end of the first controller 6 is fixedly connected to a connecting pipe. The other end of the connecting pipe is fixedly connected to a conductive slip ring 7. The signal line between the conductive slip ring 7 and the first controller 6 is set inside the connecting pipe. The conductive slip ring 7 is slidably connected to the bottom end of the rotating shaft 8 to realize electrical communication during rotation.

[0029] The conductive slip ring 7 in this invention is used to realize the rotational connection of signals and electricity. It is existing technology and will not be elaborated further here.

[0030] This invention also discloses a non-contact monitoring method for transformer oil level based on ultrasound, the steps of which are as follows: Step 1: When the blade 17 rotates, it draws oil from the oil tank 1. The oil is filtered through the filter screen 12 and discharged through the fixed cylinder 5. This cleans the oil in the detection section and creates a flow velocity in the detection section. The rotor flow meter 16 measures the oil flow velocity c. At this time, the distance between the two ultrasonic probes 18 is k = (vc)t1. The ultrasonic generator emits ultrasonic waves, where t1 is the time it takes for the ultrasonic receiver to receive the ultrasonic generator when there is oil velocity. Step 2: After the propeller 17 stops and the oil returns to calm, the ultrasonic generator emits ultrasonic waves again. The distance between the two ultrasonic probes 18 is k=vt2, where t2 is the time when the ultrasonic receiver receives the ultrasonic generator when there is no oil flow. Step 3: Calculate the specific value of the ultrasonic propagation speed v in static oil under the current environment by (vc)t1= vt2, and then substitute this specific value into Step 2 to obtain the distance k between the two ultrasonic probes 18, so as to achieve accurate measurement of the oil level. The oil level at this time is k+mn, where m and n are constant values, m is the distance from the surface of the ultrasonic receiver to the float 22, and n is the distance from the ultrasonic generator to the inner side of the bottom of the oil tank 1.

[0031] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A non-contact transformer oil level monitoring system based on ultrasound, comprising an oil tank (1) and a float (22), wherein a breathing capsule (14) is installed on the inner side of the top of the oil tank (1), characterized in that: The bottom inner side of the oil tank (1) is connected to a fixed cylinder (5). The top of the fixed cylinder (5) is flush with the bottom of the oil tank (1). The float (22) is set on the upper side of the fixed cylinder (5) and can move up and down with the oil level. The bottom end of the fixed cylinder (5) is connected to a connecting pipe (9), and the other end of the connecting pipe (9) extends into the inner side of the bottom end of the oil tank (1). A filter screen (12) is fixedly connected to the inner side of the bottom end of the oil tank (1), and the filter screen (12) covers the inlet of the other end of the connecting pipe (9). The inner side of the fixed cylinder (5) is rotatably connected to the rotating shaft (8), the outer side of the top of the rotating shaft (8) is fixedly connected to the blade (17), and the inner side of the top of the rotating shaft (8) is embedded with an ultrasonic probe (18), which is an ultrasonic receiver. A fixed shaft (23) is fixedly connected to the bottom end of the floating plate (22). An ultrasonic probe (18) is also embedded in the inner side of the bottom end of the fixed shaft (23). The ultrasonic probe (18) is an ultrasonic generator. A rotor-type flow meter (16) is rotatably connected to the outer side of the bottom end of the fixed shaft (23). When the blade (17) rotates, it draws oil from the oil tank (1). The oil is filtered through the filter screen (12) and discharged through the fixed cylinder (5) to clean the oil in the detection section. The rotor flow meter (16) measures the oil flow velocity c. At this time, the distance between the two ultrasonic probes (18) is k = (vc)t1, where t1 is the time when the ultrasonic receiver receives the ultrasonic generator when there is oil velocity. After the propeller (17) stops and the oil settles down, the distance between the two ultrasonic probes (18) is k=vt2, where t2 is the time when the ultrasonic receiver receives the ultrasonic generator when there is no oil flow. The specific value of the propagation speed v of ultrasonic waves in static oil under the current environment is calculated by (vc)t1= vt2, and then the size of the distance k between the two ultrasonic probes (18) is obtained, so as to realize the accurate measurement of the oil level. The oil level at this time is k+mn, where m is the distance from the surface of the ultrasonic receiver to the float (22), and n is the distance from the ultrasonic generator to the inner side of the bottom of the oil tank (1).

2. The ultrasonic-based non-contact transformer oil level monitoring system according to claim 1, characterized in that: The filter mesh (12) is hemispherical and is a multi-layer graded filter mesh.

3. The ultrasonic-based non-contact transformer oil level monitoring system according to claim 1, characterized in that: An annular groove (51) is provided on the inner side of the fixed cylinder (5). A sliding cylinder (13) is slidably connected to the inner side of the groove (51). The top end of the sliding cylinder (13) is fixedly connected to the bottom end of the float (22). An outlet (131) is provided at the top end of the sliding cylinder (13) for discharging the upward oil flow.

4. The ultrasonic-based non-contact transformer oil level monitoring system according to claim 3, characterized in that: The density of the slide (13) is close to that of the oil, and the float (22) can always drive the slide (13) to move up and down with the oil.

5. The ultrasonic-based non-contact transformer oil level monitoring system according to claim 3, characterized in that: The thickness of the groove (51) is greater than the thickness of the cylinder (13), and the cylinder (13) is slidably connected to the inner side of the groove (51).

6. The ultrasonic-based non-contact transformer oil level monitoring system according to claim 3, characterized in that: The diameter difference between the inner side of the sliding cylinder (13) and the inner side of the fixed cylinder (5) is 1-3 mm.

7. The ultrasonic-based non-contact transformer oil level monitoring system according to any one of claims 1-3, characterized in that: An electric push rod (15) is fixedly connected to the outside of the fixed cylinder (5). The movable end of the electric push rod (15) extends into the inside of the slide groove (51) and can abut against the slide cylinder (13).

8. The ultrasonic-based non-contact transformer oil level monitoring system according to claim 7, characterized in that: The top of the fuel tank (1) is fixedly connected to a second controller (10). The signal line (11) of the second controller (10) passes through the breathing capsule (14) and the float (22) and is connected to the ultrasonic probe (18) on the upper side.

9. The ultrasonic-based non-contact transformer oil level monitoring system according to claim 8, characterized in that: The bottom end of the fixed cylinder (5) is rotatably connected to the hub motor (21) via a shaft. A seal (20) is provided at the connection between the rotating shaft (8) and the inner side of the bottom end of the fixed cylinder (5). After the rotating shaft (8) extends out of the inner side of the bottom end of the fixed cylinder (5), a gear (19) is fixedly connected to its outer side. A gear ring is also installed on the outer side of the hub motor (21). The gear ring on the outer side of the hub motor (21) meshes with the gear (19). When the hub motor (21) rotates, the blade (17) will rotate synchronously. The bottom end of the fixed cylinder (5) is fixedly connected to the first controller (6). The first controller (6) and the second controller (10) are connected by a signal line to realize communication. The bottom end of the first controller (6) is fixedly connected to a connecting pipe. The other end of the connecting pipe is fixedly connected to a conductive slip ring (7). The conductive slip ring (7) is slidably connected to the bottom end of the rotating shaft (8) to realize electrical communication during rotation.

10. A non-contact transformer oil level monitoring method based on ultrasound, using the non-contact transformer oil level monitoring system based on ultrasound as described in claim 9, characterized in that... The steps are as follows: Step 1: When the blade (17) rotates, the oil in the oil tank (1) is drawn out. The oil is filtered through the filter screen (12) and discharged through the fixed cylinder (5). On the one hand, the oil in the detection section is clean, and on the other hand, the flow velocity appears in the detection section. The rotor flow meter (16) measures the oil flow velocity c. At this time, the distance between the two ultrasonic probes (18) is k = (vc)t1. The ultrasonic generator emits ultrasonic waves. t1 is the time when the ultrasonic receiver receives the ultrasonic generator when there is oil velocity. Step 2: After the propeller (17) stops and the oil returns to calm, the ultrasonic generator emits ultrasonic waves again. The distance between the two ultrasonic probes (18) is k=vt2, where t2 is the time when the ultrasonic receiver receives the ultrasonic generator when there is no oil flow. Step 3: Calculate the specific value of the propagation speed v of the ultrasonic wave in the static oil under the current environment by (vc)t1= vt2, and then substitute this specific value into Step 2 to obtain the size of the distance k between the two ultrasonic probes (18) to achieve accurate measurement of the oil level. The oil level at this time is k+mn, where m and n are constant values, m is the distance from the surface of the ultrasonic receiver to the float (22), and n is the distance from the ultrasonic generator to the inner side of the bottom of the oil tank (1).

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