A method and system for simulating and measuring arc discharge in insulating oil of converter transformer

Abstract

The present invention discloses a method and system for simulating and measuring arc discharge in insulating oil of a converter transformer in the technical field of electric power system, comprising the following steps: building an arc discharge experimental platform in insulating oil of a converter transformer to obtain parameter index changes in an oil tank; simulating an arc discharge experiment in insulating oil of the transformer according to the obtained parameter index changes and a preset converter transformer equivalent model; and performing multi-dimensional and multi-scale measurements of an arc burning process under multiple working conditions based on the simulated arc discharge experiment in insulating oil of the transformer.

Description

Technical Field

[0001] The present invention belongs to the technical field of power systems, and in particular relates to a method and system for simulating and measuring arc discharge in insulating oil of a converter transformer. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.

[0003] High-voltage direct current transmission projects have entered a stage of rapid development. Converter transformers and converter valves together form the core of the AC-DC transmission system connection. Due to long-term exposure to thermal, electrical and mechanical multi-physical field coupling, their operating conditions and insulation problems are more complicated. Arc discharge faults are the main cause of the explosion of the converter transformer oil tank. In the arc discharge evolution process before the transformer explodes, there are multiple extreme physical strong field couplings such as complex electromagnetic fields, strong electric fields, high temperature fields, strong pressure fields and fluid fields. In addition, arc discharge is highly destructive, develops rapidly, and has extremely complex behavior characteristics, which brings great difficulties to the study of its evolutionary physical mechanism. It is a major challenge faced by improving the insulation operation reliability of converter transformers.

[0004] According to the inventors, the key feature extraction, three-dimensional space modeling and microscopic spatiotemporal behavior characteristics of arc discharge in insulating oil under the coupling of multiple physical fields have great limitations. The evolution of arc discharge under short time scale is affected by the laws of extremely strong field coupling of space electromagnetic field, space flow field and temperature field, especially the correspondence between arc evolution mechanism and temperature and pressure. Therefore, it is necessary to extract key characteristic parameters of arc discharge in converter transformer oil, so as to lay the foundation for the next step of obtaining quantitative mathematical relationship between parameters and finally revealing the evolution mechanism of arc discharge in converter transformer oil under the action of extremely strong field.

[0005] However, the existing simulation experimental platform mainly relies on high-speed cameras to observe the evolution of discharge motion in insulating oil. The measurement method is relatively simple and the imaging effect is poor. In addition, the application of precise measurement technology for parameters such as temperature, current density, and electromagnetic environment around the arc in the insulating oil has not been considered. . In order to make full use of the characteristics of high arc light intensity, strong radiation energy, and diverse morphological changes in the oil, it is necessary to observe and record various characteristic parameters of arc discharge in the simulation experiment from multiple angles and multiple means. In addition, due to the particularity of arc discharge simulation in insulating oil before the explosion, in order to make the simulation platform consistent with the extreme strong field conditions before the explosion of the converter transformer, the experimental oil tank needs to be specially designed to be "pressure-resistant and explosion-proof", and the external experimental voltage waveform and polarity, electrode structure, gap distance, and gas and liquid pressure, temperature and other indicators inside the oil tank need to be optimized to better reflect the actual operating conditions. Summary of the invention

[0006] In order to solve the above problems, the present invention proposes a simulation and measurement method and system for arc discharge in the insulating oil of a converter transformer. The physical structure and supporting equipment of the experimental oil tank are designed by constructing an experimental platform. The physical simulation experiment is comprehensively optimized from multiple angles to explore the equivalence principle of physical simulation experiments under complex working conditions before the explosion of the converter transformer. The existing photoelectric measurement system is improved to realize multi-dimensional and multi-scale measurement of arc discharge, and the feasibility and flexibility of the experiment are taken into account to fully reflect the characteristics of the evolution of arc discharge in the insulating oil of the converter transformer before the explosion, so as to provide technical support for the next step of reconstructing the three-dimensional spatial model of arc discharge in the insulating oil.

[0007] According to some embodiments, a first solution of the present disclosure provides a method for simulating and measuring arc discharge in insulating oil of a converter transformer, which adopts the following technical solution:

[0008] A method for simulating and measuring arc discharge in insulating oil of a converter transformer comprises the following steps:

[0009] Build an arc discharge experimental platform in the insulating oil of the converter transformer to obtain the parameter index changes in the oil tank;

[0010] According to the obtained parameter index changes and the preset converter transformer equivalent model, the arc discharge experiment in the transformer insulating oil is simulated;

[0011] Based on the simulated arc discharge experiment in transformer insulating oil, multi-dimensional and multi-scale measurements of the arc burning process under multiple working conditions are carried out.

[0012] As a further technical limitation, the parameter indicators in the oil tank include temperature, current density, pressure in the insulating oil and the electromagnetic environment around the arc.

[0013] As a further technical limitation, the constructed arc discharge experimental platform in the insulating oil of the converter transformer includes a high-voltage step-up transformer, a voltage regulator, a coupling capacitor, a rectifier silicon stack, a DC blocking capacitor, an AC / DC voltage divider, an experimental oil tank and a discharge electrode model.

[0014] Furthermore, the experimental oil tank is provided with observation windows of multiple schlieren levels for multi-angle shooting of the arc discharge process; the experimental oil tank is provided with an oil filter for filtering moisture, impurities and gas in the insulating oil, and the oil filter is equipped with a movable circulation heating system for controlling the oil temperature.

[0015] Furthermore, a plurality of oil inlets are provided on one side of the experimental oil tank, and a plurality of oil outlets are provided on the other side; the number of the oil inlets and the number of the oil outlets are kept consistent.

[0016] As a further technical limitation, the converter transformer equivalent model is used to perform full-scale, full-domain field simulation on the converter transformer under full-operating conditions. Based on the global field inversion results and insulation margin, the arc discharge experimental model and oil tank in the insulating oil of the converter transformer under AC, DC and polarity reversal voltages are optimized and designed. An AC / DC composite voltage experimental platform and a polarity reversal experimental platform are built to carry out arc discharge experiments in the transformer insulating oil.

[0017] As a further technical limitation, a digital delayed pulse generator is used as a unified trigger source, and the influencing factors of the optical measurement system are comprehensively considered and optimized and corrected to achieve synchronous measurement of multi-dimensional electrical-optical signal data information.

[0018] According to some embodiments, the second solution of the present disclosure provides a system for simulating and measuring arc discharge in the insulating oil of a converter transformer, which adopts the method for simulating and measuring arc discharge in the insulating oil of a converter transformer provided in the first solution, and adopts the following technical solution:

[0019] A system for simulating and measuring arc discharge in insulating oil of a converter transformer, comprising:

[0020] The acquisition module is configured to build an arc discharge experimental platform in the insulating oil of the converter transformer and obtain parameter index changes in the oil tank;

[0021] A simulation module is configured to simulate an arc discharge experiment in transformer insulating oil according to the acquired parameter index changes and a preset converter transformer equivalent model;

[0022] The measurement module is configured to perform multi-dimensional and multi-scale measurements of the arc burning process under multiple working conditions based on the simulated arc discharge experiment in the transformer insulating oil.

[0023] According to some embodiments, a third solution of the present disclosure provides a computer-readable storage medium, which adopts the following technical solution:

[0024] A computer-readable storage medium stores a program thereon, which, when executed by a processor, implements the steps of the arc discharge simulation and measurement method in the insulating oil of a converter transformer as provided in the first aspect of the present disclosure.

[0025] According to some embodiments, a fourth solution of the present disclosure provides an electronic device, which adopts the following technical solution:

[0026] An electronic device comprises a memory, a processor and a program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of the arc discharge simulation and measurement method in the insulating oil of a converter transformer as provided in the first aspect of the present disclosure are implemented.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention builds an arc discharge experimental platform, optimizes the design of the oil tank structure, and realizes real-time monitoring of the temperature and pressure changes in the tank; on the basis of the existing optical-electrical measurement system, a multi-dimensional and multi-scale measurement method for the arc combustion process is proposed to fully observe the evolution of arc discharge in the insulating oil before the explosion of the converter transformer, improve the synchronous measurement technology, and provide a data basis for reconstructing three-dimensional spatial models such as spatial electromagnetic fields, spatial flow fields, and arc temperature, and analyzing the time domain evolution characteristics of arc discharge.

[0029] The arc discharge evolution mechanism in the insulating oil of the converter transformer disclosed in this invention carries out theoretical and technological innovation research, which is helpful to propose converter transformer explosion warning and blocking methods and build a forward defense line of "active" protection for converter transformer explosion, and has a certain foresight. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings constituting a part of the present disclosure are used to provide a further understanding of the present disclosure. The illustrative embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation on the present disclosure.

[0031] Figure 1 is a flow chart of a method for simulating and measuring arc discharge in insulating oil of a converter transformer in the first embodiment of the present disclosure;

[0032] Figure 2 This is a design diagram of an arc discharge experimental platform in insulating oil of a converter transformer in the first embodiment of the present disclosure;

[0033] Figure 3 This is a preliminary design diagram of the arc discharge experiment oil tank structure in the first embodiment of the present disclosure;

[0034] Figure 4 It is the ±800kV converter transformer calculation model in the first embodiment of the present disclosure;

[0035] Figure 5 It is the insulation model of the converter transformer end in the first embodiment of the present disclosure;

[0036] Figure 6 It is the arc discharge experimental electrode model in the AC and DC voltage experimental platform in the first embodiment of the present disclosure;

[0037] Figure 7 It is a schematic diagram of the AC / DC superposition voltage application method in the first embodiment of the present disclosure;

[0038] Figure 8 is the polarity reversal experimental voltage curve in the first embodiment of the present disclosure;

[0039] FIG9( a ) is a schematic diagram of charge separation caused by the flow of insulating oil when the oil is stationary in the first embodiment of the present disclosure;

[0040] FIG9( b ) is a schematic diagram of charge separation caused by the flow of insulating oil during oil flow in the first embodiment of the present disclosure;

[0041] Fig.10 is a schematic diagram of the structure of a parallel light path grain shadow system in a single light path grain shadow system in the first embodiment of the present disclosure;

[0042] Fig.11 is a simplified diagram of a reflective dual-light path pattern shadow system in Embodiment 1 of the present disclosure;

[0043] Fig.12 Schematic diagram of an integrated optical waveguide transient electric field measurement system based on the Pockels effect in Embodiment 1 of the present disclosure;

[0044] Fig.13 It is a schematic diagram of an arc space temperature distribution measurement system based on spectrum acquisition in the first embodiment of the present disclosure;

[0045] Fig.14 This is a schematic diagram of the Raman spectroscopy oil-paper insulation detection platform in the first embodiment of the present disclosure;

[0046] Fig.15 This is a schematic diagram of the principle structure of the medium-splitting gas chromatograph in the first embodiment of the present disclosure;

[0047] Fig.16 It is a structural block diagram of the arc discharge simulation and measurement system in the insulating oil of the converter transformer in the second embodiment of the present disclosure. DETAILED DESCRIPTION

[0048] The present disclosure is further described below in conjunction with the accompanying drawings and embodiments.

[0049] It should be noted that the following detailed descriptions are all illustrative and are intended to provide further explanation of the present disclosure. 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 disclosure belongs.

[0050] 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 disclosure. 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 "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0051] In the absence of conflict, the embodiments in the present disclosure and the features in the embodiments may be combined with each other.

[0052] Embodiment 1

[0053] Embodiment 1 of the present disclosure introduces a method for simulating and measuring arc discharge in insulating oil of a converter transformer.

[0054] like Figure 1 A method for simulating and measuring arc discharge in insulating oil of a converter transformer is shown, comprising the following steps:

[0055] Build an arc discharge experimental platform in the insulating oil of the converter transformer to obtain the parameter index changes in the oil tank;

[0056] According to the obtained parameter index changes and the preset converter transformer equivalent model, the arc discharge experiment in the transformer insulating oil is simulated;

[0057] Based on the simulated arc discharge experiment in transformer insulating oil, multi-dimensional and multi-scale measurements of the arc burning process under multiple working conditions are carried out.

[0058] This embodiment firstly builds an arc discharge measurement system in the insulating oil of a converter transformer under the action of a multi-field coupled extremely strong field. Starting from the preliminary construction of an arc discharge experimental platform, the design of the physical structure of the experimental oil tank and supporting equipment is focused on; the physical simulation experiment is comprehensively optimized from multiple angles to explore the equivalence principle of physical simulation experiments under complex working conditions before the explosion of the converter transformer; the existing photoelectric measurement system is improved to realize multi-dimensional and multi-scale measurement of arc discharge, and the feasibility and flexibility of the experiment are taken into account to fully reflect the characteristics of the arc discharge evolution in the insulating oil of the converter transformer before the explosion, and provide technical support for the next step of reconstructing the three-dimensional spatial model of arc discharge in the insulating oil.

[0059] Design of arc discharge experimental platform in converter transformer insulating oil Figure 2 As shown in the figure, the experimental circuit is mainly composed of a high-voltage step-up transformer, a voltage regulator, a coupling capacitor, a rectifier silicon stack, a DC blocking capacitor, an AC / DC voltage divider, an experimental oil tank, and a discharge electrode model. Since the arc discharge in the transformer insulating oil is in an extremely strong and complex field, the waveform and polarity of the externally applied experimental voltage inside the oil tank, the electrode structure, the gap distance, and the gas and liquid pressure, temperature and other factors need to reflect the actual operating conditions.

[0060] To this end, this embodiment aims at its "anti-pressure and explosion-proof" performance, and considers the application of accurate measurement technology of parameters such as temperature, current density, and electromagnetic environment around the arc in the insulating oil, and proposes a preliminary design scheme for the experimental oil tank structure, such as Figure 3 shown.

[0061] like Figure 3As shown, the experimental oil tank is composed of a box body and a box cover, and is comprehensively optimized in terms of box body material, shape, thickness, sealing performance, etc. to ensure that it has good mechanical properties, pressure bearing performance, sealing performance, high temperature resistance and corrosion resistance, and can withstand 100kV DC voltage and 100kV power frequency AC voltage, minimizing the danger of the experiment. In this embodiment, the box body is a columnar structure (it can also be set to other shapes such as a rectangular parallelepiped, depending on the specific needs of the site), made of high-strength steel plate (such as Q345), with a wall thickness of 12mm, and the mechanical strength is configured to be when the pressure inside it is equal to 2 atmospheres, the oil tank is damaged or torn, so as to simulate the process of damage or tearing of the oil tank of an actual transformer when it fails.

[0062] A pressure relief valve and a monitoring device are respectively provided on the top of the oil tank. The diameter of the pressure relief valve should be greater than or equal to 200mm to release the pressure inside the tank in time. The monitoring device includes a pressure sensor and a temperature sensor, which are used to obtain the internal pressure and temperature values. The number and position of the sensors are further optimized according to the actual situation to achieve all-round real-time measurement of the temperature and pressure changes in the oil tank, thereby accurately simulating the transformer explosion disaster process and providing a theoretical basis for the subsequent quantitative detection and analysis of various performance parameters and damage states of arc discharge under different intensities.

[0063] The innovation of this embodiment lies in that four Schlieren-level observation windows are installed on the oil tank body, which can be used for shooting at four angles at the same time, so as to facilitate the observation of the dynamic evolution of the initiation, movement and development of arc discharge in the insulating oil and the gas production characteristics in the process; at the same time, the experimental oil tank is equipped with an oil filter to filter out moisture, impurities and gas in the insulating oil; it is matched with a movable circulation heating system to achieve precise control of the oil temperature and adjust the flow rate of the insulating oil circulation through a variable frequency motor.

[0064] There has been relatively complete research in the existing literature on the effect of oil flow velocity on arc discharge. Unlike the single oil filling and draining valve of an ordinary oil tank, the experimental oil tank of this embodiment is provided with three oil inlets and outlets. The use of different oil inlets and outlets can simulate the effect of different oil flow directions on arc discharge, filling the gap in research in this area.

[0065] According to the parameter indicators obtained from the experimental platform, the actual fault characteristics and influencing factors of arc discharge in the insulating oil of the converter transformer before the explosion are summarized, and the actual geometric structure equivalent model of the converter transformer under typical faults is constructed, and the full-scale full-domain field simulation of the converter transformer is carried out. In this embodiment, a two-dimensional actual geometric size model is established by taking an oil-immersed converter transformer of model ZZDFPZ-415000 / 500-800 as an example. Its main physical and chemical parameters are shown in Table 1. Its overall model and quarter model are shown in Table 1. Figure 4 shown.

[0066] Table 1 Physical and chemical parameters of converter transformer materials

[0067]

[0068]

[0069] The components of the converter transformer winding mainly include: iron core 1, voltage regulating winding 2, grid-side winding 3, valve-side winding 4, oil-immersed cardboard 5, transformer oil 6 and electrostatic ring 7. The main insulation of the converter transformer refers to the insulation of the winding to other parts other than itself, mainly the insulation of the winding to the grounded parts such as the iron core, clamps, oil tank, insulation between different windings, and insulation of the lead wire to the grounded part and between different winding leads. End insulation also belongs to the category of main insulation. It refers to the insulation from the end of the winding to the upper and lower iron yokes and the ends between adjacent windings. It is an important part of the main insulation of the converter transformer.

[0070] During the simulation, the end insulation area is taken for calculation. The insulation structure of the converter transformer end is as follows: Figure 5 As shown, 1 is the voltage regulating winding, 2 is the grid side winding, 3 is the valve side winding, 4 is the insulating paperboard, 5 is the valve side winding electrostatic ring, 6 is the formed angle ring, and all gap media are transformer oil.

[0071] The high-voltage electrostatic ring 5 is placed at the end of the converter transformer winding. It is an open metal ring with a certain thickness. It is wrapped with metal foil or metal braided tape on a skeleton made of insulating material, or directly made of metal core, and its exterior is wrapped with insulating paper for insulation. The metal core is reliably connected to the metal foil or metal braided tape through a metal soft wire or metal foil tape and then led out, and then connected to the first turn coil at the end of the high-voltage winding. The electrostatic ring can not only improve the electric field distribution at the head end, but also form additional capacitance between the electrostatic ring and the coil at the head end, thereby improving the initial distribution of the winding potential under the action of the impulse voltage. The angle ring 6 is an arc-shaped insulating part with an inward or outward flange. The role of the angle ring is to increase the insulation distance of the end and prevent the end from discharging along the surface; the other role is to separate the oil gap at the end, and separate the longer oil gap in the extremely uneven electric field at the end of the winding into several smaller oil gaps, and make each oil gap have basically the same insulation margin, so as to improve the utilization factor of the insulation. In order to achieve the best insulation effect and prevent surface discharge, the ideal shape of the angle ring should coincide with the end equipotential line. The converter transformer uses a formed angle ring that basically conforms to the equipotential surface, which can effectively reduce the risk of insulation surface discharge in this area.

[0072] The voltage types that converter transformer windings bear are very complex. They not only bear AC voltage, but also DC voltage, AC / DC superposition voltage and polarity reversal voltage. When the load or power supply of the AC system at both ends changes and DC transmission is required to reverse the power flow, or when the AC system fails and stops working, it must bear the polarity reversal voltage. Therefore, compared with ordinary power transformers, when designing the insulation of converter transformers, not only the insulation performance under AC action should be considered, but also the insulation performance under polarity reversal voltage should be considered. Oil-paper insulation is the main insulation structure of converter transformers, and the nonlinearity of oil and paperboard makes the electric field distribution at the end of converter transformers very complex. It is of great significance in practical engineering to study its internal electric field distribution, simulate arc discharge experiments in converter transformer insulating oil, optimize transformer insulation structure, and improve the reliability of transmission system.

[0073] Furthermore, the insulation structure model at the converter transformer end is subjected to grid-side AC withstand voltage, valve-side AC withstand voltage, valve-side DC withstand voltage, and polarity reversal voltage experiments to obtain its electric field distribution.

[0074] Furthermore, four typical electrode models are used to simulate arc discharge experiments based on the obtained maximum field strength.

[0075] On this basis, aiming at the typical faults of converter transformers under different operating conditions, the equivalence criterion of physical simulation experiments of arc discharge in insulating oil of converter transformers was studied.

[0076] In order to simulate the arc discharge process in the insulating oil under the extremely non-uniform electric field, this embodiment uses a needle-plate electrode structure, such as Figure 6 As shown in the figure, the plate electrode material is copper, the needle electrode material is tungsten alloy, the tip electrode end angle is 60°, and positive polarity high voltage is applied; the flat plate electrode is a 150mm diameter disk with a grounded bottom, and the distance from the needle tip to the flat plate ground electrode is 10mm. In order to meet different experimental requirements, the oil gap distance can be accurately adjusted by the ruler installed on the electrode rod, and the accuracy can reach 0.1mm.

[0077] Applied voltage waveform and polarity

[0078] As mentioned above, due to the special operating conditions of the converter transformer, the excitation voltage type of its valve-side winding is very different from that of an ordinary power transformer: in addition to being subjected to AC voltage, lightning strikes and operating overvoltage, it is also subjected to DC, DC superimposed on AC and polarity reversal voltages. Different voltage types also affect the electric field distribution inside the converter transformer.

[0079] To this end, this embodiment builds an AC / DC composite voltage and polarity reversal simulation experiment platform:

[0080] 1) AC / DC composite voltage experimental platform

[0081] The test adopts the pressure-increasing method, and the pressure-increasing method is as follows: Figure 7 As shown, AC, DC and AC / DC superposition voltages of different proportions are applied to the test piece, and the voltage is increased at a constant speed until breakdown. The AC voltage and DC voltage are directly increased and broken down, with a voltage increase speed of 2kV / s (effective value), and the AC / DC superposition voltage is pre-applied. After the DC voltage is pre-applied for 1 minute, the AC voltage is increased at a constant speed until breakdown.

[0082] 2) Polarity reversal experimental platform

[0083] The DC polarity reversal test standard currently used in my country is formulated with reference to the IEC61378 standard, but the polarity reversal time adopted by each unit is also different. The current standard in my country stipulates that the voltage waveform when conducting a polarity reversal test on a converter transformer is as follows: Figure 8 First, the voltage is applied to the negative peak within 1 minute and maintained for 90 minutes, then the applied voltage is changed from the negative peak to the positive peak with the same amplitude within 1 minute and maintained for 90 minutes, then the voltage is changed to the negative peak again and maintained for 45 minutes, and finally the voltage is reduced to 0V within 1 minute. It is stipulated that no more than 10 partial discharge pulses greater than 2000pC shall occur within any 10 minutes.

[0084] Oil flow status

[0085] A large number of fault statistics show that most of the current large-scale converter transformers are oil-immersed transformers, and the most typical insulation structure is the oil-paper insulation system. Due to the flow of transformer oil, the oil and the insulating paperboard rub against each other, resulting in charge separation at their interface, and through the movement process of charge migration, accumulation and discharge, a rush current is formed, as shown in Figure 9(a) and Figure 9(b). Figure 9(a) shows the oil at rest, and Figure 9(b) shows the oil flowing. The flow rate, flow direction, flow state of the insulating oil, as well as the temperature, conductivity, water content, aging degree, etc. of the oil itself will cause oil flow electrification of different intensities.

[0086] In order to simulate the oil flow state under different operating conditions as much as possible, the three oil inlets and outlets of the experimental oil tank of this embodiment can be used to inject transformer oil of different viscosities and different aging states from different directions and at different rates. The matching oil filter is used to control the water content of the insulating oil, and the variable frequency motor is used to adjust the circulating flow rate of the insulating oil. The movable circulating heating system can realize accurate control of the oil temperature and reflect it through the temperature sensor, so as to monitor the physical and chemical properties of the insulating oil in the tank in real time during arc discharge of different intensities.

[0087] Taking into account the complex behavioral characteristics of arc discharge in the insulating oil of the converter transformer, in order to better provide technical support for the above-mentioned exploration and research, this embodiment attempts to build a multi-dimensional, multi-scale optical-electrical measurement system for the arc burning process under different oil temperatures, oil speeds, voltages, oil gap distances, oil flow directions, insulating oil aging states, etc., based on the optimization of the arc morphology, electromagnetic field, temperature field, and voltage and current measurement systems.

[0088] The arc measurement device mainly includes an image acquisition system (high-speed camera), a transient electromagnetic field measurement system (optical waveguide electromagnetic field sensor, magnetic field tester), a spatial temperature measurement system (spectrometer), a voltage and current measurement system (wideband Rogowski coil, high-voltage probe) and a high-speed trigger system. During the experiment, it is planned to set up multiple groups of high-speed cameras at different angles to collect discharge arc images, optimize the high-speed camera lens aperture, focal length, frame rate, exposure time and other parameters, and study the construction of a dual-light path reflective focusing schlieren detection system to improve the imaging effect.

[0089] The Schlieren method is a physical measurement method that uses a Schlieren system to display and measure the flow field. It can be roughly divided into a single-path Schlieren system and a dual-path Schlieren system. Fig.10 This is the optical path diagram of the transmission type single light path ripple system. Due to the uneven flow field medium in the disturbance area, a small deflection angle ε is generated when the light beam passes through the inhomogeneous medium. Then the light source produces a relative displacement Δh relative to the knife edge, and the relationship between ε and Δh is:

[0090] Δh=f 2 ·ε (1)

[0091] Among them, f 2 is the focal length of the Schlieren lens.

[0092] At the same time, the contrast C of this part of illumination change relative to the background illumination is:

[0093]

[0094] Theoretical formula for compressible flow field:

[0095]

[0096] Where n is the refractive index of the fluid in the disturbed flow field, is the gradient of the refractive index along the y direction, and L is the thickness of the disturbed fluid along the z direction (the propagation direction of light).

[0097] The relationship between illumination change and refractive index is obtained from the above formulas (2) to (4):

[0098] (The direction of the blade is perpendicular to the x direction) (4)

[0099] Where n is the gas refractive index and h is the height of the light source image.

[0100] like Fig.11 This is a schematic diagram of the reflective dual-path schlieren system used in this embodiment. The light beam passes through the disturbance area and hits the schlieren spherical mirror to form an effective light source, then focuses on the knife edge, is cut by the knife edge, and finally forms an image. Since the light beam passes through the disturbance area twice, the sensitivity is higher than that of the single-path system. Therefore, the deflection angle in the dual-path schlieren system is twice that of the single-path schlieren system, so:

[0101] (The direction of the blade is perpendicular to the x direction) (5)

[0102] In the formula, R is the radius of the spherical reflector, R=2f, and f is the focal length of the spherical mirror.

[0103] From the comparison between formula (4) and formula (5), it can be seen that the sensitivity of the dual-light path ripple system is 4 times that of the single-light path ripple system, which can better convert the change of the medium refractive index into the change of light intensity, so that the visualization phenomenon of the refractive index change is displayed more clearly.

[0104] On this basis, the design of the focused schlieren system is an inverse problem that considers the coupling of various parameters. According to the physical model, the various physical quantities are first sorted out, and then they are linked together through different types of formulas to obtain the results. Table 2 lists the three major parameters involved in the system: performance, components, and geometric layout; Table 3 lists the design formulas followed by the focused schlieren system.

[0105] Table 2 Classification of parameters according to different properties

[0106]

[0107] Table 3 Analysis of properties of each curve

[0108]

[0109]

[0110] In order to study the spatial electric field distribution of arc discharge in insulating oil, this embodiment improves the integrated optical waveguide transient electric field measurement system based on the Pockels effect, which mainly includes a collimating lens, an optical waveguide electric field sensor and a photodetector, such as Fig.12 As shown, the tank light wave signal to be observed is converted into linear polarized light through the optical fiber into circular polarized light by the collimation of the lens, and then converted into circular polarized light by the 1 / 4 wave plate. Under the influence of the external electric field and voltage, the light passing through the crystal sensor will produce double refraction. The applied voltage is proportional to the double refracted light wave and linearly related to the output light intensity. Therefore, the voltage value can be measured after electro-optical conversion and corresponding signal processing.

[0111] On this basis, this embodiment carries out an optimized design of light wave modulation transmitted in the optical waveguide between the electrodes, thereby exploring the functional curve relationship between the relative light intensity and the needle plate electrode voltage during arc discharge.

[0112] like Fig.13 As shown, this embodiment uses a spectral method to measure the temperature distribution of the arc space in the insulating oil. The system includes: a lens optical device, a spectrometer, an imaging screen, a trigger device, etc. After the controller receives the trigger signal, an arc with a controllable arc burning process is generated in the test oil tank. After the collimation and focusing effect of the lens optical device, the arc spectrum is collected by the spectrometer, and the arc image is collected by the imaging screen. The spectrum data and the arc image data are transmitted to the computer, and the calibration coefficient is calculated. Combined with image processing, the arc temperature field distribution can be obtained, which is used to further study the selection of key parameters such as spectral line sensitivity, resolution and sharpness.

[0113] In addition, the Raman spectrometer, the mid-split gas chromatograph and the mid-split automatic degassing oscillator were used to study the gas production characteristics in the insulating oil by gas production volume, gas production rate and three-ratio method. Referring to the oscillation degassing method of GB T 17623-2017 "Gas chromatography determination of dissolved gas components in insulating oil", the mid-split automatic degassing oscillator was used to heat, oscillate and degas the insulating oil after discharge at a constant temperature and time; and then, Fig.14 FIG. 1 is a schematic diagram of the Raman spectrum oil-paper insulation detection platform of the present embodiment, which mainly includes a laser, a spatial filter, a notch filter, a spectrometer, a charge-coupled device (CCD) and a computer, etc., to obtain a stable Raman spectrum of insulating oil; Fig.15 The figure shows the principle structure diagram of the medium-fraction gas chromatograph of this embodiment, which mainly includes four parts: column box, gas path, detector and circuit, and realizes scientific testing and analysis of the gas components of insulating oil.

[0114] The above-mentioned optical observation system and electrical measurement system use a digital delayed pulse generator as a unified trigger source, utilizing its advantages of fast speed, strong logic function, high fan-out capability, high time resolution, low noise, and small lead crosstalk. Taking into account factors such as the exposure time of the optical measurement system and the transmission delay of the coaxial cable signal, the time relationship between the optical signal and the electrical signal of each frame is corrected, and the synchronization scheme based on the exposure clock signal of the high-speed camera is optimized, ultimately realizing the synchronous observation of the optical-electrical data information of the multi-physical characteristic quantities of arc discharge in insulating oil.

[0115] Embodiment 2

[0116] Embodiment 2 of the present disclosure introduces a system for simulating and measuring arc discharge in insulating oil of a converter transformer.

[0117] like Fig.16 The arc discharge simulation and measurement system in the insulating oil of a converter transformer shown in the figure comprises:

[0118] The acquisition module is configured to build an arc discharge experimental platform in the insulating oil of the converter transformer and obtain parameter index changes in the oil tank;

[0119] A simulation module is configured to simulate an arc discharge experiment in transformer insulating oil according to the acquired parameter index changes and a preset converter transformer equivalent model;

[0120] The measurement module is configured to perform multi-dimensional and multi-scale measurements of the arc burning process under multiple working conditions based on the simulated arc discharge experiment in the transformer insulating oil.

[0121] The detailed steps are the same as the arc discharge simulation and measurement method in the converter transformer insulating oil provided in Example 1, and will not be repeated here.

[0122] Embodiment 3

[0123] A third embodiment of the present disclosure provides a computer-readable storage medium.

[0124] A computer-readable storage medium stores a program thereon, which, when executed by a processor, implements the steps of the arc discharge simulation and measurement method in the insulating oil of a converter transformer as described in the first embodiment of the present disclosure.

[0125] The detailed steps are the same as the arc discharge simulation and measurement method in the converter transformer insulating oil provided in Example 1, and will not be repeated here.

[0126] Embodiment 4

[0127] A fourth embodiment of the present disclosure provides an electronic device.

[0128] An electronic device comprises a memory, a processor and a program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of the method for simulating and measuring arc discharge in insulating oil of a converter transformer as described in the first embodiment of the present disclosure are implemented.

[0129] The detailed steps are the same as the arc discharge simulation and measurement method in the converter transformer insulating oil provided in Example 1, and will not be repeated here.

[0130] Although the above describes the specific implementation methods of the present disclosure in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present disclosure. Technical personnel in the relevant field should understand that on the basis of the technical solution of the present disclosure, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present disclosure.

Claims

1. A method for simulating and measuring arc discharge in insulating oil of a converter transformer, characterized in that: The following steps are involved: Build an arc discharge experimental platform in the insulating oil of the converter transformer to obtain the parameter index changes in the oil tank; According to the obtained parameter index changes and the preset converter transformer equivalent model, the arc discharge experiment in the transformer insulating oil is simulated; Based on the simulated arc discharge experiment in transformer insulating oil, multi-dimensional and multi-scale measurements of the arc burning process under multiple working conditions are carried out; The constructed arc discharge experimental platform in the insulating oil of the converter transformer includes an experimental oil tank; the body of the experimental oil tank is provided with observation windows of multiple schlieren levels for multi-angle shooting of the arc discharge process; the experimental oil tank is equipped with an oil filter for filtering moisture, impurities and gas in the insulating oil, and the oil filter is equipped with a movable circulating heating system for controlling the oil temperature; One side of the experimental oil tank is provided with multiple oil inlets, and the other side is provided with multiple oil outlets, into which transformer oils of different viscosities and different aging states are respectively injected from different directions and at different rates; the number of the oil inlets and the oil outlets is kept consistent.

2. A method for simulating and measuring arc discharge in insulating oil of a converter transformer as claimed in claim 1, characterized in that: The parameter indicators in the oil tank include the temperature, current density, pressure in the insulating oil and the electromagnetic environment around the arc.

3. A method for simulating and measuring arc discharge in insulating oil of a converter transformer as claimed in claim 1, characterized in that: The arc discharge experimental platform in the insulating oil of the converter transformer also includes a high-voltage step-up transformer, a voltage regulator, a coupling capacitor, a rectifier silicon stack, a DC blocking capacitor, an AC / DC voltage divider and a discharge electrode model.

4. A method for simulating and measuring arc discharge in insulating oil of a converter transformer as claimed in claim 1, characterized in that: The converter transformer equivalent model is used to perform full-scale, full-domain field simulation of the converter transformer under all operating conditions. Based on the global field inversion results and insulation margin, the arc discharge experimental model and oil tank in the insulating oil of the converter transformer under AC, DC and polarity reversal voltages are optimized and designed. An AC / DC composite voltage experimental platform and a polarity reversal experimental platform are built to carry out arc discharge experiments in the insulating oil of the transformer.

5. A method for simulating and measuring arc discharge in insulating oil of a converter transformer as claimed in claim 1, characterized in that: A digital delayed pulse generator is used as a unified trigger source, and the influencing factors of the optical measurement system are comprehensively considered and optimized and corrected to achieve synchronous measurement of multi-dimensional electrical-optical signal data information.

6. A system for simulating and measuring arc discharge in insulating oil of a converter transformer, comprising: The acquisition module is configured to build an arc discharge experimental platform in the insulating oil of the converter transformer and obtain parameter index changes in the oil tank; A simulation module is configured to simulate an arc discharge experiment in transformer insulating oil according to the acquired parameter index changes and a preset converter transformer equivalent model; A measurement module is configured to perform multi-dimensional and multi-scale measurements of arc burning processes under multiple working conditions based on a simulated arc discharge experiment in transformer insulating oil; The constructed arc discharge experimental platform in the insulating oil of the converter transformer includes an experimental oil tank; the body of the experimental oil tank is provided with observation windows of multiple schlieren levels for multi-angle shooting of the arc discharge process; the experimental oil tank is equipped with an oil filter for filtering moisture, impurities and gas in the insulating oil, and the oil filter is equipped with a movable circulating heating system for controlling the oil temperature; One side of the experimental oil tank is provided with multiple oil inlets, and the other side is provided with multiple oil outlets, into which transformer oils of different viscosities and different aging states are respectively injected from different directions and at different rates; the number of the oil inlets and the oil outlets is kept consistent.

7. A computer-readable storage medium having a program stored thereon, characterized in that: When the program is executed by a processor, the steps of the arc discharge simulation and measurement method in the converter transformer insulating oil as described in any one of claims 1 to 5 are implemented.

8. An electronic device comprising a memory, a processor, and a program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps of the arc discharge simulation and measurement method in the converter transformer insulating oil are implemented as described in any one of claims 1 to 5.

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