Method for analyzing segmented characteristics of dynamic pressure generated by arc discharge in transformer oil

Abstract

The application discloses a kind of dynamic pressure segmented feature analysis methods generated by arc discharge in transformer oil, in the method, carry out arc discharge experiment in the closed oil tank of transformer oil, observe the movement of bubble generated by discharge and measure arc discharge voltage, current and pressure waveform;Based on bubble movement analysis discharge bubble diameter change and based on the frequency band characteristics of pressure waveform generated by pressure waveform;Carry out arc discharge experiment of different energy, different boundary condition and different current waveform, compare pressure waveform, obtain the influencing factor of pressure waveform;According to the diameter change of discharge bubble of arc discharge, the frequency band characteristics of arc discharge voltage, current and pressure waveform of arc discharge, form the segmented feature of discharge pressure.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of arc discharge in transformer oil, and particularly relates to a method for analyzing segmented characteristics of dynamic pressure generated by arc discharge in transformer oil. BACKGROUND

[0002] The gas generated by arc discharge in transformer oil can increase the pressure in the oil tank, and further cause the oil tank to rupture or even explode and catch fire. Because the dynamic pressure waveform of arc discharge is not clearly understood, the explosion relief protection measures of the oil tank cannot be effectively designed.

[0003] The information disclosed in the background section merely serves to enhance the understanding of the background of the present application, and therefore can include information that does not constitute prior art that is already known to those of ordinary skill in the art. SUMMARY

[0004] In view of the deficiencies or defects in the prior art, the present application provides a method for analyzing segmented characteristics of dynamic pressure generated by arc discharge in transformer oil, which can realize the cognition of the waveform characteristics of the discharge dynamic pressure, and further reveal the generation mechanism of the discharge dynamic pressure based on the physical processes in different discharge stages.

[0005] The object of the present application is achieved by the following technical solutions.

[0006] A method for analyzing segmented characteristics of dynamic pressure generated by arc discharge in transformer oil comprises,

[0007] An arc discharge experiment is carried out in a sealed oil-filled tank of transformer oil, the movement of the bubbles generated by the arc discharge is observed, and the voltage, current and pressure waveform of the arc discharge are measured;

[0008] The diameter change of the discharge bubbles is analyzed based on the movement of the bubbles, and the frequency band characteristics of the pressure waveform are generated based on the pressure waveform;

[0009] Arc discharge experiments with different energies, different boundary conditions and different current waveforms are carried out, the pressure waveforms are compared, and the influencing factors of the pressure waveform are obtained;

[0010] The segmented characteristics of the discharge pressure are formed according to the diameter change of the discharge bubbles, the voltage, current and frequency band characteristics of the pressure waveform of the arc discharge.

[0011] In the method, the generation of the frequency band characteristics of the pressure waveform based on the pressure waveform comprises analyzing the part where the arc discharge voltage suddenly changes, which corresponds to the arc striking and extinguishing process and the bubble collapse process; and the discharge dynamic pressure waveform is subjected to fast Fourier transform to obtain the frequency spectrum characteristics of the discharge dynamic pressure.

[0012] The method includes changing the peak value of the arc discharge current, the current duration, and the electrode distance to change the arc discharge energy and carry out arc discharge experiments with different energies.

[0013] The method includes changing the oil filling amount in the oil tank, the oil tank material, and the oil tank structure size to change the boundary conditions of the arc discharge and carry out arc discharge experiments with different boundary conditions.

[0014] The method includes changing the capacitance and inductance of the discharge circuit to change the current waveform of the discharge and carry out arc discharge experiments with different current waveforms.

[0015] The method includes measuring the voltage and current of the arc discharge to obtain the arc resistance, power, and energy.

[0016] The method includes using a shadow imaging system and a high-speed camera to collect the images of the discharge bubbles, and analyzing the images of the discharge bubbles to obtain the diameter change of the discharge bubbles.

[0017] The shadow imaging system includes a light source generating an optical fiber, and a diaphragm and a lens arranged along the light path.

[0018] The method includes RLC a circuit including a high-voltage direct-current power supply, a capacitor, and an inductor, and a high-voltage differential probe and an oscilloscope.

[0019] The method includes an arc discharge experiment including a gas collection and volume statistical system for measuring the discharge bubbles.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] The present application obtains the segmented characteristics of the dynamic pressure of the arc discharge according to the shadow images, electrical parameters, bubble behavior, and pressure waveform of the arc discharge, reveals the dynamic pressure generation mechanism in different stages, and provides a mechanism and an engineering basis for correctly understanding the arc discharge pressure waveform in the transformer oil tank, and helps the simulation of the dynamic pressure waveform in the transformer oil tank.

[0022] The above description is only a summary of the technical solutions of the present application, in order to make the technical means of the present application more clear and understandable, and to achieve the level that the person skilled in the art can implement according to the content of the description, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are described below. BRIEF DESCRIPTION OF DRAWINGS

[0023] Various other advantages and benefits of the present application will become apparent to those of ordinary skill in the art, upon reading the following detailed description of the preferred embodiment. The accompanying drawings are included to provide a better understanding of the preferred embodiment, and are not intended to limit the scope of the application. It should be readily understood that the drawings are not to scale, and are merely intended to depict the various embodiments of the application. As such, the drawings should not be construed as limiting the scope of the application.

[0024] In the drawings:

[0025] Figure 1 is a flow chart of the method for analyzing the dynamic pressure segment characteristics generated by arc discharge in transformer oil;

[0026] Figure 2 is a schematic diagram of the platform for observing arc discharge bubbles, measuring electrical parameters, gas production, and pressure waveforms;

[0027] Figure 3 is a schematic diagram of the electrical parameters, pressure waveforms, and pressure segment characteristics of arc discharge;

[0028] Figure 4(a) is a curve of the diameter of an arc discharge bubble and pressure variation, and Figure 4(b) is a photograph of an arc discharge shadowgraph;

[0029] Figure 5 is the dynamic pressure segment characteristics under different arc energies.

[0030] The present application will be further explained in conjunction with the accompanying drawings and examples. DETAILED DESCRIPTION

[0031] Embodiments of the present application will be described more fully hereinafter with reference to the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the application to those skilled in the art.

[0032] It should be noted that some terms are used in the description and claims to refer to certain components. Those skilled in the art will understand that the same component can be referred to by different names. The description and claims do not distinguish components by the difference in the name, but by the difference in the function of the component. As mentioned throughout the description and claims, "including" or "including" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment for implementing the present application, and the description is for the purpose of the general principles of the specification, not to limit the scope of the present application. The scope of protection of the present application is defined by the appended claims.

[0033] In order to facilitate the understanding of the embodiments of the present application, the following will be further explained by combining the drawings with several specific examples, and each drawing does not constitute a limitation to the embodiments of the present application.

[0034] In order to better understand, Figures 1 to 5 As shown in a kind of transformer oil arc discharge generated dynamic pressure segment feature analysis method, it includes,

[0035] Carrying out arc discharge experiment in the closed oil tank of transformer oil, observing the movement of bubble generated by discharge and measuring arc discharge voltage, current and pressure waveform;

[0036] Based on bubble movement, analyze the diameter change of discharge bubble, and generate frequency band characteristics of pressure waveform based on pressure waveform;

[0037] Carrying out arc discharge experiment of different energy, different boundary conditions and different current waveform, comparing pressure waveform, obtaining influencing factors of pressure waveform.

[0038] In the present application, by changing the arc discharge energy, it is found that the pressure waveform under different discharge energies has obvious segment characteristics;By changing the oil tank boundary, using flexible material oil tank, it is found that the amplitude of quasi-static pressure and steady pressure is greatly reduced.

[0039] According to the diameter change of discharge bubble of arc discharge, arc discharge voltage, current and frequency band characteristics of pressure waveform, the segment characteristics of discharge pressure are formed.

[0040] Further, the pressure waveform characteristics are divided into four stages: shock wave, pulsating pressure, quasi-static pressure and steady pressure.

[0041] In the preferred embodiment of the method, the frequency band characteristics of the pressure waveform generated based on the pressure waveform include analyzing the part where the arc discharge voltage occurs suddenly, corresponding to the arc discharge and bubble collapse process;The fast Fourier transform is carried out on the discharge dynamic pressure waveform to obtain the frequency spectrum characteristics of the discharge dynamic pressure.

[0042] In a preferred embodiment of the method, the arc discharge energy is changed by changing the peak value of the arc discharge current, the current duration, the electrode distance to carry out arc discharge experiments of different energies.

[0043] In a preferred embodiment of the method, the boundary conditions of the arc discharge are changed by changing the oil filling amount in the oil tank, the oil tank material, the oil tank structure size to carry out arc discharge experiments of different boundary conditions.

[0044] In a preferred embodiment of the method, the current waveform of the discharge is changed by changing the capacitance and inductance of the discharge circuit to carry out arc discharge experiments of different current waveforms.

[0045] In a preferred embodiment of the method, the voltage and current of the arc discharge are measured to obtain the arc resistance, power and energy.

[0046] In a preferred embodiment of the method, a shadow imaging system and a high-speed camera are used to collect images of the discharge bubbles, and the images of the discharge bubbles are analyzed to obtain the diameter change of the discharge bubbles.

[0047] In a preferred embodiment of the method, the shadow imaging system includes a light source generating an optical fiber and a diaphragm and a lens arranged along the light path.

[0048] In a preferred embodiment of the method, the arc discharge experiment includes RLC a circuit including a high-voltage direct-current power supply, a capacitor and an inductor, and a high-voltage differential probe and an oscilloscope.

[0049] In a preferred embodiment of the method, the arc discharge experiment includes a gas collection and volume statistics system for measuring the discharge bubbles.

[0050] In one embodiment, the method includes

[0051] carrying out arc discharge experiments in a sealed oil-filled tank, observing the movement of the discharge bubbles, measuring the arc discharge voltage, current and pressure waveform,

[0052] analyzing the diameter change law of the discharge bubbles, the electrical parameters and the frequency band characteristics of the pressure waveform,

[0053] carrying out discharge experiments of different energies, different boundary conditions and different current waveforms, and comparing the pressure waveform laws,

[0054] proposing segmented characteristics of the discharge pressure according to the movement law of the arc discharge bubbles, the electrical parameters and the pressure characteristics.

[0055] In this embodiment, based on RLCThe arc discharge experiment platform in oil is built, including the electrical parameter measurement of voltage and current, gas volume statistics, high-speed observation of discharge bubble by shadow method, discharge transient pressure measurement, etc.

[0056] In one embodiment, the experimental platform schematic diagram is as shown in Figure 2 ;

[0057] In the embodiment, the arc resistance, power and energy can be further calculated based on the voltage and current measurement results of the arc discharge. Figure 3 The obtained discharge pressure waveform is as shown in

[0058] In combination with Figure 3 , it is further verified that, in the present application: by changing the arc discharge energy, it is found that the pressure waveforms under different discharge energies all have obvious segment characteristics; by changing the oil tank boundary, using the oil tank of flexible material, it is found that the amplitudes of quasi-static pressure and steady-state pressure are greatly reduced.

[0059] In another embodiment, in combination with the image processing algorithm, the image of the discharge bubble is analyzed to obtain the diameter change of the discharge bubble, and in combination with the discharge pressure waveform, the corresponding graph of the diameter change of the discharge bubble and the discharge pressure is drawn, as shown in Fig. 4(a), and the shadow method image of the arc discharge is as shown in Fig. 4(b).

[0060] In combination with the above figures, it can be found that,

[0061] When the arc is about to be extinguished, the internal plasma temperature decreases, the electron density decreases, the arc resistance increases, the voltage rises, and the arc bubble is about to collapse due to insufficient energy from the high-speed image. The mechanism is explained as follows: the arc discharge first generates a shock wave due to the breakdown and expansion process of the arc channel; the diameter of the discharge bubble changes periodically, and the essential reason is that the pressure between the bubble and the liquid is unbalanced, the bubble produces a periodic expansion and contraction process, and a pulsating pressure is generated; with the increase of the arc deposition energy, the arc gas production increases, and the gas internal pressure is almost balanced with the liquid pressure, the bubble diameter is almost unchanged, and quasi-static pressure is generated; with the end of the discharge, the arc energy is no longer injected, the discharge bubble collapses, the discharge gas temperature decreases, the discharge pressure drops and finally reaches the steady-state pressure.

[0062] In addition, in the present application, experiments are carried out under different discharge energies, and dynamic pressure waveforms under different arc deposition energies are obtained, which all conform to the above characteristics, as shown in Figure 5 .

[0063] In another more specific embodiment,

[0064] The experimental equipment includes the following:

[0065] An arc discharge device comprising the aforementioned RLC A circuit comprising a high-voltage DC power supply, a capacitor and an inductor, and a high-voltage differential probe and an oscilloscope;

[0066] A pressure sensor for real-time monitoring of pressure fluctuations in the oil tank;

[0067] A high-speed camera and shadow imaging system: for recording the movement trajectory of the discharge bubble;

[0068] A data acquisition system for recording the signal of the pressure sensor and the video data of the high-speed camera;

[0069] A transformer oil tank comprising a sealed oil-filled tank for simulating actual working conditions.

[0070] Among them, the experimental variables include:

[0071] Arc discharge energy: adjusted by changing the current peak value (such as 10kA, 20kA, 30kA) and current duration (such as 1ms, 2ms, 3ms);

[0072] Boundary conditions: in addition to changing the oil tank to a flexible material, the oil tank, by changing the oil filling amount (such as 10L, 20L, 30L) in the oil tank, the oil tank material (such as stainless steel, aluminum), the oil tank structure size (such as diameter 10cm, 20cm) to adjust;

[0073] Current waveform: changed by adjusting the capacitance (such as 1μF, 2μF, 3μF) and inductance (such as 1mH, 2mH, 3mH) in the discharge circuit;

[0074] In this more specific embodiment, including the following steps:

[0075] Preparation stage: build the experimental platform, ensure all equipment normal operation;

[0076] Parameter setting: according to the experimental design, set different arc discharge parameters and boundary conditions;

[0077] Data acquisition: start arc discharge experiment, record the data of pressure sensor and video taken by high-speed camera;

[0078] Data analysis: process the collected pressure waveform data and bubble movement image, extract the required features;

[0079] Among them, about pressure waveform data processing, including the following steps:

[0080] Pretreatment: filtering the original pressure waveform data, removing noise interference;

[0081] Feature extraction: extract the peak value, duration and frequency characteristics of the pressure waveform;

[0082] Spectrum analysis: Perform a Fast Fourier Transform (FFT) on the pressure waveform to obtain a frequency spectrum;

[0083] Mutation point detection: Identify the parts of the pressure waveform where voltage mutations occur, and establish the relationship between these mutations and the arcing, extinction, and bubble collapse processes based on observations during the experiment;

[0084] Regarding bubble motion image processing, the following steps are included:

[0085] Image preprocessing: Perform denoising and smoothing on the bubble motion images captured by the high-speed camera;

[0086] Bubble edge detection: Use image processing algorithms (such as Canny edge detection) to extract the edges of the bubbles;

[0087] Bubble diameter calculation: Based on the edge information, calculate the change in bubble diameter over time.

[0088] In another embodiment, a set of example experimental data is provided:

[0089] Arc discharge parameters: The current peak is 20 kA, and the duration is 2 ms;

[0090] Boundary conditions: The oil tank is filled with 20 L of oil, made of stainless steel, with a diameter of 20 cm;

[0091] Current waveform: The discharge circuit has a capacitance of 2 μF and an inductance of 2 mH;

[0092] The pressure waveform spectrum analysis is as follows:

[0093] Raw data: The collected pressure waveform data;

[0094] Preprocessing results: The filtered pressure waveform data is smoother;

[0095] Spectrum: The pressure waveform spectrum obtained by FFT shows the main frequency components;

[0096] Mutation points: Voltage mutations are identified to occur at 1 ms, corresponding to the arcing process, and at 2.5 ms, corresponding to the extinction process.

[0097] Finally, the segmented features of the dynamic pressure waveform are as follows:

[0098] Arcing stage: The pressure waveform shows a significant rise at 1 ms, indicating that the arc has started discharging;

[0099] Stable discharge stage: From 1 ms to 2.5 ms, the pressure waveform maintains a higher level, indicating that the arc is in a stable discharge state;

[0100] Arc extinguishing stage: the pressure waveform at 2.5ms moment drops rapidly, indicating that the arc is extinguished.

[0101] In summary, the disclosure discloses a dynamic pressure segmentation feature analysis method of arc discharge in transformer oil, and discloses the arc discharge pressure generation mechanism, which verifies the rationality of the dynamic pressure segmentation division of the discharge in the engineering proposed by the present application. The present application can be further used for the research of transformer explosion prevention and pressure relief, and is helpful for dynamic pressure simulation calculation. In addition, the dynamic pressure waveform feature analysis of arc discharge in liquid medium, the analysis of shock wave, bubble pulsation pressure and quasi-static pressure are used to perfect the cross frontier of the field and fluid mechanics and guide the engineering practice application, which also has certain significance.

[0102] The above description has been given for the purpose of illustration and description. Furthermore, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although a number of example aspects and embodiments have been discussed above, those of ordinary skill in the art will recognize certain variations, modifications, changes, additions, and sub-combinations thereof.

Claims

1. A method for analyzing the segmented characteristics of dynamic pressure generated by arc discharge in transformer oil, comprising the following steps: Carry out arc discharge experiments in a sealed oil-filled tank of transformer oil, observe the movement of bubbles generated by discharge, and measure the arc discharge voltage, current, and pressure waveforms; Analyze the change of discharge bubble diameter based on bubble motion; Generate frequency band characteristics of the pressure waveform based on the pressure waveform, including analyzing the part where the arc discharge voltage suddenly changes, corresponding to the arc discharge arcing and extinction process and bubble collapse process; perform fast Fourier transform on the discharge dynamic pressure waveform to obtain the frequency spectrum characteristics of the discharge dynamic pressure; Conduct arc discharge experiments with different energies, boundary conditions, and current waveforms, compare pressure waveforms, and identify factors influencing pressure waveforms; According to the change of discharge bubble diameter of arc discharge, the frequency band characteristics of arc discharge voltage, current and pressure waveform, the segmented characteristics of discharge pressure are formed; in, The images of discharge bubbles are collected by using shadow imaging system and high-speed camera, and the images of discharge bubbles are analyzed to obtain the changes of discharge bubble diameter. Pressure waveform data processing includes the following steps: Filter the original pressure waveform data to remove noise interference; Extract the peak, duration and frequency characteristics of the pressure waveform; Perform fast Fourier transform (FFT) on the pressure waveform to obtain a spectrum diagram; Identify the part of the pressure waveform where the voltage suddenly changes, and compare it with the observations during the experiment to establish the relationship between the sudden change and the arc starting, arc extinction and bubble collapse process; The method is used for explosion-proof and pressure relief of transformers; The arc discharge energy can be adjusted by changing the current peak value: 10kA, 20kA, 30kA and the current duration: 1ms, 2ms, 3ms, and by changing the electrode distance; In addition to changing the fuel tank to a flexible material, the boundary conditions were adjusted by changing the fuel volume in the tank: 10L, 20L, 30L, the tank material: stainless steel, aluminum, and the tank structure size: 10cm, 20cm in diameter; The current waveform can be changed by adjusting the capacitance in the discharge circuit: 1μF, 2μF, 3μF and the inductance: 1mH, 2mH, 3mH; Measure the voltage and current of arc discharge to obtain arc resistance, power and energy; Arc discharge experiments include RLC a circuit including a high-voltage DC power supply, capacitors and inductors, and a high-voltage differential probe and oscilloscope; The dynamic pressure segmentation characteristics under different arc energies have the following characteristics: From the moment of arcing, the stages are shock wave, bubble pulsation pressure, quasi-static pressure and steady-state pressure. The arc extinction moment is the dividing point between quasi-static pressure and steady-state pressure.

2. The method according to claim 1, characterized in that The shadow imaging system includes a light source that generates an optical fiber and an aperture and a lens arranged along the light path.

3. The method according to claim 1, characterized in that The arc discharge experiment includes a gas collection and volume counting system for measuring the discharge bubbles.

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