Device and method for detecting initial voltage, withstand voltage and breakdown voltage of partial discharge of transformer oil

Abstract

The invention relates to a transformer oil partial discharge initial voltage, withstand voltage and breakdown voltage detection device and method.The device comprises a lightproof oil cup, a combined piezoelectric ceramic boosting device and an automatic circuit disconnecting device, two electrodes are installed on the left side and the right side in the oil cup, and a laser transmitter is arranged on the front side of the oil cup; a laser beam emitted by the computer horizontally penetrates through the position between the two electrodes, a camera device with the shooting direction facing the area between the two electrodes is arranged on a shading cover plate on the upper portion of the oil cup, and the computer analyzes shot images to judge the partial discharge initial voltage, the withstand voltage and the breakdown voltage of the transformer oil. The combined piezoelectric ceramic boosting device provides a high-voltage input power supply for the two electrodes; the automatic circuit disconnecting device automatically disconnects the power supply circuit when the light spot brightness and the light spot shape of the water molecules and the impurity particles reach set critical conditions. The device and the method are beneficial to improving the accuracy of detecting the initial voltage, the withstand voltage and the breakdown voltage of the partial discharge of the transformer oil.

Description

Technical Field

[0001] The invention relates to the technical field of transformer oil detection, and in particular to a device and method for detecting partial discharge starting voltage, withstand voltage and breakdown voltage of transformer oil. Background Art

[0002] At the construction site of power lines, electrical equipment such as oil transformers of different grades, oil switches of different grades, and oil reactors of different grades are installed. The insulating oil in these equipment needs to be tested regularly to verify its insulation performance. The electrical performance indicators of transformer oil include partial discharge inception voltage, withstand voltage and breakdown voltage, dielectric loss factor and volume resistivity.

[0003] The transformer oil partial discharge starting voltage refers to the lowest voltage value when the partial discharge phenomenon is first observed in the process of gradually increasing the voltage applied to the transformer oil. The withstand voltage test is to apply a certain voltage to the sample under certain test conditions for a certain period of time. If no breakdown or flashover occurs during this period, the transformer oil partial discharge starting voltage and withstand voltage value are key parameters for transformer insulation design, and are also key indicators for transformer oil electrical aging test design.

[0004] The breakdown voltage test of transformer oil is to increase the voltage under certain conditions until the sample breaks down, and measure the breakdown voltage or electrical strength, which is often used for transformer fault analysis and diagnosis. Due to the high technical difficulty and long test time of the partial discharge starting voltage and withstand voltage test of transformer oil, a simpler breakdown voltage test is often used in production to reflect the dielectric strength of transformer oil, such as GB / T507-2002 "Determination of Breakdown Voltage of Insulating Oil", which uses the cracking sound or the vibration of the voltmeter pointer to judge whether the breakdown voltage has been reached. The repeatability of the test data is poor, and the circuit can only be automatically cut off after a constant arc and short-circuit current reach a certain value. The short-circuit high current generated at the moment of electrode breakdown and the long-term high current during the constant arc period are very likely to cause damage to the stepping transformer or resonant transformer coil in the instrument. In addition, due to the different test procedures for partial discharge inception voltage, withstand voltage and breakdown voltage, and different application scenarios, the two cannot be replaced or converted with each other. Therefore, it is urgent to develop a test device that can quickly detect and stably obtain the partial discharge inception voltage, withstand voltage and breakdown voltage values ​​of transformer oil, and can quickly cut off the circuit at the moment of arc generation. Summary of the invention

[0005] The object of the present invention is to provide a device and method for detecting the partial discharge inception voltage, withstand voltage and breakdown voltage of transformer oil, which are beneficial to improving the accuracy of detecting the partial discharge inception voltage, withstand voltage and breakdown voltage of transformer oil.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present invention is: a transformer oil partial discharge starting voltage, withstand voltage and breakdown voltage detection device, including an opaque oil cup, a combined piezoelectric ceramic boosting device and a circuit automatic disconnection device, two oppositely arranged electrodes are fixedly installed on the left and right sides of the oil cup, a laser transmitter is arranged on the front side of the oil cup, and the laser beam emitted by the laser transmitter passes horizontally between the two electrodes, a light shielding cover is arranged on the upper part of the oil cup, and a camera device with a shooting direction facing the area between the two electrodes in the oil cup is arranged on the light shielding cover, and the camera device is connected to a computer, and the computer is connected to a computer through a The image captured by the camera device is analyzed to determine the partial discharge starting voltage, withstand voltage and breakdown voltage of the transformer oil; the combined piezoelectric ceramic booster device is electrically connected to the two electrodes via the power supply circuit to provide them with a high-voltage input power supply, and the combined piezoelectric ceramic booster device includes an integrated piezoelectric ceramic unit formed by connecting a plurality of piezoelectric ceramic units in series, and the number of piezoelectric ceramic units connected to the circuit can be changed to change the output voltage; the circuit automatic disconnection device is arranged on the power supply circuit, and when the light spot brightness and light spot shape of the water molecules and impurity particles reach the set critical conditions, it is determined that the transformer oil has been broken down and the power supply circuit is automatically disconnected.

[0007] Furthermore, the combined piezoelectric ceramic boosting device is arranged outside the oil cup; electrode mounting holes are respectively opened on the left and right sides of the oil cup, the two electrodes are respectively installed in the corresponding electrode mounting holes, and the working ends of the two electrodes are located in the oil cup and arranged opposite to each other, and the power connection ends of the two electrodes respectively pass out of the oil cup and are connected to the combined piezoelectric ceramic boosting device; the two electrodes can adjust the installation position in the electrode mounting hole forward and backward to adjust the distance between the working ends of the two electrodes; a laser emitter mounting hole is opened on the front side of the oil cup, and the laser emitter is installed on the oil cup through the laser emitter mounting hole, and its laser emitting end faces into the oil cup.

[0008] Furthermore, the laser emitter is a tunable laser with variable laser wavelength; the laser wavelength emitted by the laser emitter is adapted to the size of water molecules and impurity particles in the transformer oil, so as to illuminate the free water molecules and impurity particles in the transformer oil, thereby forming a light spot in the illumination channel.

[0009] Furthermore, the installation height of the laser transmitter is adapted to the installation height of the two electrodes so that the laser beam emitted by it can pass horizontally between the two electrodes; the oil cup is filled with transformer oil to be tested, and the filling height of the transformer oil to be tested is higher than the installation height of the two electrodes.

[0010] Furthermore, the camera device uses a high-definition camera, and the camera device is connected to a computer. The computer determines the partial discharge starting voltage, withstand voltage and breakdown voltage of the transformer oil through image analysis.

[0011] Furthermore, the combined piezoelectric ceramic boosting device includes an integrated piezoelectric ceramic unit, a sliding contact and a control module. The integrated piezoelectric ceramic unit includes 100 1000-volt piezoelectric ceramic units, which are connected in series in sequence front to back. The sliding contact is slidably installed on the side of the integrated piezoelectric ceramic unit and contacts the voltage output end of the side of each piezoelectric ceramic unit during the sliding process. One of the two electrodes is connected to one end of the integrated piezoelectric ceramic unit through an automatic circuit disconnection device and grounded, and the other of the two electrodes is connected to the sliding contact, thereby achieving an output voltage range from 1000 volts to 100 kilovolts; the control module is connected to the automatic circuit disconnection device to control the on and off of the automatic circuit disconnection device; during the operation of the combined piezoelectric ceramic boosting device, the sliding contact slides a distance of 3 piezoelectric ceramic units per second to achieve a change of 3 kilovolts in the output voltage per second, thereby providing a boosted high voltage for the two electrodes.

[0012] The present invention also provides a method for detecting the partial discharge starting voltage, withstand voltage and breakdown voltage of transformer oil using the above device, comprising:

[0013] S1. Add the transformer oil to be tested into the oil cup until it is higher than the installation height of the two electrodes;

[0014] S2, starting the laser transmitter, wherein the laser transmitter emits a laser beam to irradiate the transformer oil in the oil cup;

[0015] S3, continuously taking images of the transformer oil in the oil cup by means of a camera device; in this process, starting the combined piezoelectric ceramic booster device and continuously increasing the voltage between the two electrodes, so that the free water molecules and impurity particles in the transformer oil are ionized and excited under the electric field, forming a light spot in the illumination channel, so that the continuously taken images contain change information of the water molecules and impurity particles;

[0016] S4. Perform image analysis on the images taken by the camera device through a computer to extract the change information of water molecules and impurity particles in the taken images; when the spot brightness and spot shape of the water molecules and impurity particles reach different critical conditions, it means that the transformer oil is in different stages of starting partial discharge, about to be broken down and already broken down, and the corresponding voltage value between the two electrodes is the partial discharge starting voltage, withstand voltage and breakdown voltage of the transformer oil.

[0017] Furthermore, the specific method for performing image analysis on the captured image is:

[0018] 1) Performing regional cropping on the captured image to crop out invalid image areas in the image, including the area other than the area between the two electrodes and two light reflection areas within a certain distance from the end surface of the electrode;

[0019] 2) Perform noise reduction on the cropped image to eliminate the noise in the image so that only the background and light spots exist in the image;

[0020] 3) Perform grayscale processing and binarization on the image after noise reduction to obtain a grayscale image containing brightness information and a black-and-white image that highlights the light spot features in the image;

[0021] 4) Extracting the contour features of the light spots in the binary black-and-white image to obtain the contour size and distribution position information of all light spots and the morphological information of the pattern formed by the light spots;

[0022] 5) The brightness of all light spots within the light spot contours is calculated based on the grayscale image. When the brightness of all light spots reaches the set first threshold value and a dendritic discharge morphology appears in the light spot pattern, it is considered that the water molecules and impurity particles are ionized and excited under the electric field, and the transformer oil reaches the stage of starting partial discharge. The corresponding voltage value between the two electrodes is the partial discharge starting voltage of the transformer oil. When the brightness of all light spots reaches the set second threshold value and the dendritic discharge morphology that appears in the light spot pattern is close to penetrating between the two electrodes, it is considered that the water molecules and impurity particles are ionized and excited under the electric field, and the transformer oil is about to be broken down. The corresponding voltage value between the two electrodes is the withstand voltage of the transformer oil. When the brightness of all light spots reaches the set third threshold value and the dendritic discharge morphology that appears in the light spot pattern has penetrated between the two electrodes, it is considered that the water molecules and impurity particles are ionized and excited under the electric field, and the transformer oil has reached the stage of being broken down. The corresponding voltage value between the two electrodes is the breakdown voltage of the transformer oil.

[0023] Furthermore, the laser transmitter adopts a tunable laser with variable laser wavelength; after adding the transformer oil to be tested into the oil cup and turning on the laser transmitter, the laser wavelength is changed intermittently within a certain range adapted to the size of water molecules and impurity particles; each time the laser wavelength is changed, steps S3-S4 are repeated to obtain all partial discharge initiation voltages, withstand voltages and breakdown voltages under different laser wavelengths; the first k breakdown voltage values ​​with the smallest values ​​are taken to calculate the average value, which is used as the final breakdown voltage of the transformer oil; the partial discharge initiation voltage and withstand voltage of these k operations are respectively calculated as the average values, which are used as the final partial discharge initiation voltage and withstand voltage of the transformer oil.

[0024] Compared with the prior art, the present invention has the following beneficial effects: the present invention provides a device and method for detecting the partial discharge starting voltage, withstand voltage and breakdown voltage of transformer oil, which detects the partial discharge starting voltage, withstand voltage and breakdown voltage of transformer oil by detecting the change of free water molecules in transformer oil with the increase of voltage, which can not only improve the accuracy of detection and judgment, but also is simple to operate and easy to implement; in addition, the device innovatively adopts a combined piezoelectric ceramic booster device as a high-voltage booster power supply for the transformer oil partial discharge starting voltage, withstand voltage and breakdown voltage detection device, which has the advantages of extremely small current under high voltage, and has high integration, small size and stable performance, which is the first in the field of electric power oil detection device instruments for power systems. Therefore, the present invention has strong practicality and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a side view of the device structure of an embodiment of the present invention;

[0026] Figure 2 is a top view of the device structure of an embodiment of the present invention;

[0027] Figure 3 It is a circuit schematic diagram of a combined piezoelectric ceramic voltage boosting device in an embodiment of the present invention.

[0028] In the figure: 1. Camera device; 2. Oil cup; 3. Electrode; 4. Laser emitter; 5. Laser beam; 6. Light shielding cover. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0030] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0031] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0032] like Figure 1-2As shown, this embodiment provides a transformer oil partial discharge starting voltage, withstand voltage and breakdown voltage detection device, including an opaque oil cup 2, a combined piezoelectric ceramic boosting device and a circuit automatic disconnection device, two electrodes 3 are fixedly installed on the left and right sides of the oil cup 2, a laser emitter 4 is arranged on the front side of the oil cup 2, and a laser beam 5 emitted by the laser emitter 4 passes horizontally between the two electrodes 3, a light shielding cover 6 is arranged on the upper part of the oil cup, and a camera 1 with a shooting direction facing the area between the two electrodes in the oil cup is arranged on the light shielding cover 6, and the camera 1 is connected to a computer, and the computer judges the partial discharge starting voltage, withstand voltage and breakdown voltage of the transformer oil by performing image analysis on the image taken by the camera 1. The combined piezoelectric ceramic boosting device is electrically connected to the two electrodes through a power supply circuit to provide a high-voltage input power supply for them, and the combined piezoelectric ceramic boosting device includes an integrated piezoelectric ceramic unit formed by connecting multiple piezoelectric ceramic units in series, and can change the number of piezoelectric ceramic units connected to the circuit to change the output voltage. The circuit automatic disconnecting device is arranged on the power supply circuit, and when the light spot brightness and light spot shape of water molecules and impurity particles reach the set critical conditions, it is judged that the transformer oil has been broken down and the power supply circuit is automatically disconnected.

[0033] The installation height of the laser emitter 4 is adapted to the installation height of the two electrodes 3 so that the laser beam 5 emitted by the laser emitter 4 can horizontally pass between the two electrodes 3. The oil cup 2 is filled with transformer oil to be tested, and the filling height of the transformer oil to be tested is higher than the installation height of the two electrodes 3.

[0034] The combined piezoelectric ceramic booster device is arranged outside the oil cup 2. Electrode mounting holes are respectively provided on the left and right sides of the oil cup 2, and two electrodes 3 are respectively installed in the corresponding electrode mounting holes, and the working ends of the two electrodes 3 are located in the oil cup 2 and arranged opposite to each other, and the power connection ends of the two electrodes 3 respectively pass out of the oil cup 2 and are connected to the combined piezoelectric ceramic booster device, so as to change the voltage between the two electrodes 3 through the combined piezoelectric ceramic booster device. The two electrodes 3 can adjust the installation position in the electrode mounting hole forward and backward to adjust the spacing between the two electrode working ends.

[0035] A laser emitter mounting hole is provided on the front side of the oil cup 2 , and the laser emitter 4 is mounted on the oil cup 2 through the laser emitter mounting hole, with the laser emitting end thereof facing the inside of the oil cup 2 .

[0036] In this embodiment, the camera device 1 uses a high-definition camera and is installed on the light shielding cover 6. The camera device 1 is connected to a computer, and the computer determines the partial discharge starting voltage, withstand voltage and breakdown voltage of the transformer oil through image analysis. The camera cannot have both high definition and high speed. High definition can make the shooting picture resolution higher and the acquired image details richer, while high speed can make more pictures that can be captured per second, without missing the image change details during the boosting process. In order to increase the sensitivity of the detection, at least 100 frames per second are selected. In order to ensure the accuracy of the detection, a camera with a resolution of 1920*1080 is selected. At the same time, the camera is required to have a short focal length and macro distance, and try to capture the useful detection area within the imaging range. In actual image sampling, the light path of the laser transmitter is the effective detection area, which accounts for less than 20% of the image sampling area of ​​the entire camera. Under the premise that the camera channel bandwidth is fixed, the narrowing of the field of view, that is, the regional sampling method, can be used to reduce the image acquisition resolution and further improve the sampling frame rate. In addition, the reduction of the acquired pixels can greatly reduce the operation time in the subsequent image analysis operation.

[0037] In this embodiment, the electrode 3 is made of brass or stainless steel.

[0038] This device detects the partial discharge starting voltage, withstand voltage and breakdown voltage of transformer oil by the changes of water molecules and impurity particles in the withstand voltage test. The transformer oil in the equipment will be mixed with water and impurities after use. When voltage is applied to the transformer oil mixed with water and impurities, the transformer oil is affected by high-voltage electrons, and the free water molecules inside it will gather at the high-voltage electrode, causing the transformer oil molecules to intensify their activity, driving the impurity particles in the transformer oil to float. The higher the voltage, the more intense the movement phenomenon.

[0039] According to the Tyndall effect, that is, when the wavelength of the light wave is greater than the particle irradiated by the light channel during the irradiation, the light will be scattered, and the closer the wavelength of the light is to the size of the particle, the more obvious the scattering phenomenon is. By selecting a laser irradiator with a suitable wavelength, the free water molecules and impurity particles in the oil can be irradiated, thereby forming a light spot in the irradiation channel. Therefore, in this device, the laser emitter 4 is selected according to the size of the water molecules and impurity particles in the transformer oil, so that the wavelength of the laser emitted by the laser emitter 4 is adapted to the size of the water molecules and impurity particles in the transformer oil, thereby irradiating the free water molecules and impurity particles in the transformer oil, and forming a light spot in the irradiation channel.

[0040] Preferably, in order to further improve the accuracy of detection, the laser transmitter used in this embodiment is a tunable laser with variable wavelength of emitted laser light. How to improve the detection accuracy based on the tunable laser will be further described below.

[0041] like Figure 3As shown, in this embodiment, the combined piezoelectric ceramic boosting device includes an integrated piezoelectric ceramic unit, a sliding contact and a control module. The integrated piezoelectric ceramic unit includes 100 1000-volt piezoelectric ceramic units, which are connected in series in sequence front to back. The sliding contact is slidably installed on the side of the integrated piezoelectric ceramic unit and contacts the voltage output end of the side of each piezoelectric ceramic unit during the sliding process. One of the two electrodes is connected to one end of the integrated piezoelectric ceramic unit through an automatic circuit disconnection device and grounded, and the other of the two electrodes is connected to the sliding contact, thereby realizing an output voltage range from 1000 volts to 100 kilovolts; the control module is connected to the automatic circuit disconnection device to control the on and off of the automatic circuit disconnection device; during the operation of the combined piezoelectric ceramic boosting device, the sliding contact slides a distance of 3 piezoelectric ceramic units per second to achieve a change of 3 kilovolts in the output voltage per second, thereby providing a boosted high voltage for the two electrodes.

[0042] The real-time images in the illumination channel are collected by a high-definition camera, and image analysis is performed to extract the change information of water molecules and impurity particles in the captured images. The brightness and shape of the light spot in the image can reflect the state of the transformer oil. When the brightness of the light spot reaches a certain level and a dendritic discharge morphology appears in the light spot and is close to penetration, it means that the transformer oil is about to be broken down by high voltage. The voltage value recorded at this time is the withstand voltage of the transformer oil.

[0043] Based on this working principle, this embodiment also provides a method for detecting the partial discharge starting voltage, withstand voltage and breakdown voltage of transformer oil using the above device, including:

[0044] S1. Add the transformer oil to be tested into the oil cup 2 until it is higher than the installation height of the two electrodes 3.

[0045] S2, start the laser transmitter 4, and the laser transmitter 4 emits a laser beam 5 to irradiate the transformer oil in the oil cup 2.

[0046] S3, continuously taking images of the transformer oil in the oil cup 2 by means of the camera device 1; in this process, starting the combined piezoelectric ceramic boost device and continuously increasing the voltage between the two electrodes 3, so that the free water molecules and impurity particles in the transformer oil are ionized and excited under the electric field, forming a light spot in the illumination channel, so that the continuously taken images contain the change information of the water molecules and impurity particles.

[0047] S4. Perform image analysis on the images captured by the camera device 1 by means of a computer to extract information on changes in water molecules and impurity particles in the captured images; when the spot brightness and spot shape of the water molecules and impurity particles reach different critical conditions, it indicates that the transformer oil is at different stages of starting partial discharge, about to be broken down, and already broken down, and the corresponding voltage value between the two electrodes 3 is the partial discharge starting voltage, withstand voltage, and breakdown voltage of the transformer oil.

[0048] Among them, the specific method of performing image analysis on the captured image is:

[0049] 1) Perform regional cropping on the captured image to crop out invalid image areas in the image, including areas other than the area between the two electrodes and two light reflection areas within a certain distance from the end surface of the electrode, and only retain the stable area in the middle of the area between the two electrodes for feature recognition.

[0050] The area other than the area between the two electrodes is not within the feature recognition range of this method. However, the area within a certain distance from the end surface of the electrode, that is, the area close to the end surface of the electrode, will produce light reflection and affect the detection accuracy. By cropping the image, the detection accuracy can be improved, the feature recognition range can be reduced, the camera sampling frame rate can be increased, the amount of single frame data to be analyzed by the computer can be reduced, the analysis speed can be increased, the computing power can be reduced, and the sensitivity of feature analysis can be increased.

[0051] 2) Perform noise reduction on the cropped image to eliminate the noise in the image so that only the background and light spots exist in the image.

[0052] Noise reduction can remove small, dark interfering light spots, making the image more distinct. The threshold of noise reduction will affect the size of the noise points to be removed.

[0053] 3) The image after noise reduction is subjected to grayscale processing and binarization processing to obtain a grayscale image containing brightness information and a black-and-white image that highlights the light spot features in the image.

[0054] 4) Extract the contour features of the light spots in the binary black-and-white image to obtain the contour size and distribution position information of all the light spots and the morphological information of the pattern formed by the light spots.

[0055] 5) The brightness of all light spots within the light spot contours is calculated based on the grayscale image. When the brightness of all light spots reaches the set first threshold value and a dendritic discharge morphology appears in the light spot pattern, it is considered that the water molecules and impurity particles are ionized and excited under the electric field, and the transformer oil reaches the stage of starting partial discharge. The corresponding voltage value between the two electrodes is the partial discharge starting voltage of the transformer oil. When the brightness of all light spots reaches the set second threshold value and the dendritic discharge morphology that appears in the light spot pattern is close to penetrating between the two electrodes, it is considered that the water molecules and impurity particles are ionized and excited under the electric field, and the transformer oil is about to be broken down. The corresponding voltage value between the two electrodes is the withstand voltage of the transformer oil. When the brightness of all light spots reaches the set third threshold value and the dendritic discharge morphology that appears in the light spot pattern has penetrated between the two electrodes, it is considered that the water molecules and impurity particles are ionized and excited under the electric field, and the transformer oil has reached the stage of being broken down. The corresponding voltage value between the two electrodes is the breakdown voltage of the transformer oil.

[0056] As mentioned above, the closer the wavelength of the laser is to the size of the particles, the more obvious the scattering phenomenon is. However, the situation of transformer oil in the equipment being doped with water and impurities after use will be different. In order to improve the detection accuracy, the wavelength of the laser should be adapted to the size of the particles in the transformer oil as much as possible. Therefore, the laser transmitter in this embodiment adopts a tunable laser with a variable laser wavelength. After adding the transformer oil to be detected to the oil cup and turning on the laser transmitter, the laser wavelength is changed intermittently within a certain range that is adapted to the size of the water molecules and impurity particles. Each time the laser wavelength is changed, the operation of steps S3-S4 is repeated once, so that all partial discharge initiation voltages, withstand voltages and breakdown voltages under different laser wavelengths within the laser wavelength range can be obtained. The first k breakdown voltage values ​​with the smallest values ​​are taken to calculate the average value as the final breakdown voltage of the transformer oil. The local discharge initiation voltage and withstand voltage of these k operations are respectively calculated as the average values ​​as the final partial discharge initiation voltage and withstand voltage of the transformer oil. It should be noted here that each time the laser wavelength is changed and steps S3-S4 are repeated, the voltage between the two electrodes should be restored to the initial value and then gradually increased again to ensure operational consistency in each test.

[0057] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A transformer oil partial discharge inception voltage, withstand voltage and breakdown voltage detection device, characterized in that: The invention comprises an opaque oil cup, a combined piezoelectric ceramic voltage-boosting device and an automatic circuit disconnection device. Two electrodes arranged opposite to each other are fixedly installed on the left and right sides of the oil cup. A laser emitter is arranged on the front side of the oil cup. The laser beam emitted by the laser emitter passes horizontally between the two electrodes. A light-shielding cover is arranged on the upper part of the oil cup. A camera device with a shooting direction facing the area between the two electrodes in the oil cup is arranged on the light-shielding cover. The camera device is connected to a computer. The computer judges the partial discharge starting voltage, withstand voltage and breakdown voltage of the transformer oil by performing image analysis on the images taken by the camera device. The combined piezoelectric ceramic voltage-boosting device is electrically connected to the two electrodes via a power supply circuit to provide a high-voltage input power supply therefor. The combined piezoelectric ceramic voltage-boosting device comprises an integrated piezoelectric ceramic unit formed by connecting a plurality of piezoelectric ceramic units in series, and can change the number of piezoelectric ceramic units connected to the circuit to change the output voltage. The automatic circuit disconnection device is arranged on the power supply circuit, and when the light spot brightness and light spot shape of water molecules and impurity particles reach a set critical condition, it is judged that the transformer oil has been broken down and the power supply circuit is automatically disconnected.

2. The transformer oil partial discharge inception voltage, withstand voltage and breakdown voltage detection device according to claim 1, characterized in that: The combined piezoelectric ceramic boosting device is arranged outside the oil cup; electrode mounting holes are respectively opened on the left and right sides of the oil cup, the two electrodes are respectively installed in the corresponding electrode mounting holes, and the working ends of the two electrodes are located in the oil cup and arranged opposite to each other, and the power connection ends of the two electrodes respectively pass out of the oil cup and are connected to the combined piezoelectric ceramic boosting device; the two electrodes can adjust the installation positions in the electrode mounting holes forward and backward to adjust the distance between the working ends of the two electrodes; a laser emitter mounting hole is opened on the front side of the oil cup, and the laser emitter is installed on the oil cup through the laser emitter mounting hole, and its laser emitting end faces into the oil cup.

3. The transformer oil partial discharge inception voltage, withstand voltage and breakdown voltage detection device according to claim 1, characterized in that: The laser emitter is a tunable laser with variable laser wavelength; the laser wavelength emitted by the laser emitter is adapted to the size of water molecules and impurity particles in the transformer oil, so as to illuminate the free water molecules and impurity particles in the transformer oil, thereby forming a light spot in the light channel.

4. The transformer oil partial discharge inception voltage, withstand voltage and breakdown voltage detection device according to claim 1, characterized in that: The installation height of the laser transmitter is adapted to the installation height of the two electrodes so that the laser beam emitted by it can pass horizontally between the two electrodes; the oil cup is filled with transformer oil to be tested, and the filling height of the transformer oil to be tested is higher than the installation height of the two electrodes.

5. The transformer oil partial discharge inception voltage, withstand voltage and breakdown voltage detection device according to claim 1, characterized in that: The camera device uses a high-definition camera, and the camera device is connected to a computer. The computer determines the partial discharge starting voltage, withstand voltage and breakdown voltage of the transformer oil through image analysis.

6. The transformer oil partial discharge inception voltage, withstand voltage and breakdown voltage detection device according to claim 1, characterized in that: The combined piezoelectric ceramic boosting device includes an integrated piezoelectric ceramic unit, a sliding contact and a control module. The integrated piezoelectric ceramic unit includes 100 1000-volt piezoelectric ceramic units, which are connected in series in sequence front to back. The sliding contact is slidably installed on the side of the integrated piezoelectric ceramic unit and contacts the voltage output end of the side of each piezoelectric ceramic unit during the sliding process. One of the two electrodes is connected to one end of the integrated piezoelectric ceramic unit through an automatic circuit disconnection device and grounded, and the other of the two electrodes is connected to the sliding contact, thereby realizing an output voltage range from 1000 volts to 100 kilovolts; the control module is connected to the automatic circuit disconnection device to control the on and off of the automatic circuit disconnection device; during the operation of the combined piezoelectric ceramic boosting device, the sliding contact slides a distance of 3 piezoelectric ceramic units per second to achieve a change of 3 kilovolts in the output voltage per second, thereby providing a boosted high voltage for the two electrodes.

7. A method for detecting partial discharge inception voltage, withstand voltage and breakdown voltage of transformer oil using the device according to any one of claims 1 to 6, characterized in that: include: S1. Add the transformer oil to be tested into the oil cup until it is higher than the installation height of the two electrodes; S2, starting the laser transmitter, wherein the laser transmitter emits a laser beam to irradiate the transformer oil in the oil cup; S3, continuously taking images of the transformer oil in the oil cup by means of a camera device; in this process, starting the combined piezoelectric ceramic booster device and continuously increasing the voltage between the two electrodes, so that the free water molecules and impurity particles in the transformer oil are ionized and excited under the electric field, forming a light spot in the illumination channel, so that the continuously taken images contain change information of the water molecules and impurity particles; S4. Perform image analysis on the images taken by the camera device through a computer to extract the change information of water molecules and impurity particles in the taken images; when the spot brightness and spot shape of the water molecules and impurity particles reach different critical conditions, it means that the transformer oil is in different stages of starting partial discharge, about to be broken down and already broken down, and the corresponding voltage value between the two electrodes is the partial discharge starting voltage, withstand voltage and breakdown voltage of the transformer oil.

8. The transformer oil partial discharge inception voltage, withstand voltage and breakdown voltage detection method according to claim 7, characterized in that: The specific method for performing image analysis on the captured images is as follows: 1) Performing regional cropping on the captured image to crop out invalid image areas in the image, including the area other than the area between the two electrodes and two light reflection areas within a certain distance from the end surface of the electrode; 2) Perform noise reduction on the cropped image to eliminate the noise in the image so that only the background and light spots exist in the image; 3) Perform grayscale processing and binarization on the image after noise reduction to obtain a grayscale image containing brightness information and a black-and-white image that highlights the light spot features in the image; 4) Extracting the contour features of the light spots in the binary black-and-white image to obtain the contour size and distribution position information of all light spots and the morphological information of the pattern formed by the light spots; 5) The brightness of all light spots within the light spot contours is calculated based on the grayscale image. When the brightness of all light spots reaches the set first threshold value and a dendritic discharge morphology appears in the light spot pattern, it is considered that the water molecules and impurity particles are ionized and excited under the electric field, and the transformer oil reaches the stage of starting partial discharge. The corresponding voltage value between the two electrodes is the partial discharge starting voltage of the transformer oil. When the brightness of all light spots reaches the set second threshold value and the dendritic discharge morphology that appears in the light spot pattern is close to penetrating between the two electrodes, it is considered that the water molecules and impurity particles are ionized and excited under the electric field, and the transformer oil is about to be broken down. The corresponding voltage value between the two electrodes is the withstand voltage of the transformer oil. When the brightness of all light spots reaches the set third threshold value and the dendritic discharge morphology that appears in the light spot pattern has penetrated between the two electrodes, it is considered that the water molecules and impurity particles are ionized and excited under the electric field, and the transformer oil has reached the stage of being broken down. The corresponding voltage value between the two electrodes is the breakdown voltage of the transformer oil.

9. A transformer oil partial discharge inception voltage, withstand voltage and breakdown voltage detection method according to claim 7, characterized in that: The laser transmitter adopts a tunable laser with variable wavelength of emitted laser light; after adding transformer oil to be tested into the oil cup and turning on the laser transmitter, the laser wavelength is changed intermittently within a certain range adapted to the size of water molecules and impurity particles; each time the laser wavelength is changed, steps S3-S4 are repeated to obtain all partial discharge initiation voltages, withstand voltages and breakdown voltages under different laser wavelengths; the first k breakdown voltage values ​​with the smallest values ​​are taken to calculate the average value, which is used as the final breakdown voltage of the transformer oil; the partial discharge initiation voltages and withstand voltages of these k operations are respectively calculated with the average values, which are used as the final partial discharge initiation voltage and withstand voltage of the transformer oil.

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