Variable-frequency insulation electric-thermal force coupling electric tree aging multi-parameter in-situ characterization test system and method

Abstract

The application discloses a variable-frequency insulation electric heating force coupling electric tree branch aging multi-parameter in-situ characterization test system and method. In the test system, an electric tree branch sample electrode system is arranged in a test cavity of an infrared spectrum test system; a sample mounting seat of the electric tree branch sample electrode system is used for clamping two ends of a sample to be tested and can apply tensile / compressive stress; a grounding electrode is in contact with a side surface opposite to a tip end of a needle electrode of the sample to be tested; a heater is in contact with the sample to be tested; a complex waveform voltage generating system is connected with the needle electrode; the grounding electrode is connected with a leakage current test system; the leakage current test system is connected with a computer; an electroluminescence and digital imaging system is used for observing the sample to be tested in bright field and dark field and is connected with the computer; a spectrum test system is used for performing spectrum imaging on the sample to be tested and is connected with the computer; and an output end of a partial discharge test system is connected with the computer. The application can realize real-time observation of multi-parameter in-situ characterization in an electric tree branch initiation and growth process.

Description

Technical Field

[0001] This invention belongs to the field of insulation testing technology for solid insulation materials, specifically relating to a multi-parameter in-situ characterization testing system and method for electrothermal coupling electrical tree aging of frequency conversion insulation. Background Technology

[0002] With the widespread adoption of smart grids that integrate new energy power, various types of power equipment, including high-capacity power electronic equipment, are subjected to high-voltage frequency conversion. Solid insulation media in frequency conversion insulation systems often withstand the coupling effects of high temperature, high voltage, and high frequency, making them highly susceptible to insulation aging and failure. Due to the casting process, solid insulation media inevitably contain insulation defects such as air gaps, interface mismatches, impurities, and conductor sharp corners. Under these special operating conditions, these defects can easily lead to electrical treeing, posing a significant threat to the safe and stable operation of power equipment.

[0003] In the study of electrical tree aging in solid insulating materials, domestic and foreign researchers have focused on the effects of various voltage forms, such as AC voltage, DC voltage, variable frequency sinusoidal voltage, and DC superimposed low-frequency harmonics, emphasizing the following aspects: (1) the morphological characteristics of electrical tree initiation and growth; (2) the characteristics of partial discharge during electrical tree initiation and growth; and (3) the electroluminescence characteristics during electrical tree initiation and growth. Existing studies have focused on lower voltage frequencies where discharge is weaker, and the discharge characteristics of electrical tree channels have not received attention. Under variable frequency voltage waveforms, electrical trees are often accompanied by strong partial discharge and luminescence within the channels. However, existing devices and methods can only obtain single parameters such as electrical tree morphology, partial discharge, or electroluminescence characteristics separately, and cannot obtain them simultaneously. Furthermore, it is not possible to simultaneously characterize the structural and physicochemical property changes of electrical trees at different growth stages online. Due to the randomness of electrical tree growth in solid insulation, if different electrical tree samples are used, the single structural or performance parameters obtained are difficult to correlate with each other, making it impossible to conduct in-depth research on the electrical tree aging mechanism. Furthermore, the experimental method of continuing electrical tree growth on the original sample after offline testing deviates from actual working conditions because the fatigue and damage accumulation effects during the initiation and growth of electrical trees have time characteristics. Once the voltage is removed and offline parameter testing is performed, the fatigue and damage accumulation effects will diminish. The electrical tree growth during the subsequent electrical tree growth experiment will differ from that under continuous voltage application in actual conditions, making it difficult to accurately obtain various in-situ parameters during the electrical tree aging process. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a multi-parameter in-situ characterization test system and method for the aging of electrical treeing in variable frequency insulation electrothermal coupling. This system is suitable for efficient testing of the initiation and growth characteristics of electrical treeing in solid insulation materials under complex variable frequency voltage coupled with multiple physical fields, and can observe the multi-parameter in-situ characterization of the initiation and growth process of electrical treeing in real time.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The in-situ characterization and testing system for multi-parameter aging of variable frequency insulation electrothermal coupling electric tree includes a complex waveform voltage generation system, an electric tree sample electrode system, a leakage current testing system, an electroluminescence and digital imaging system, a spectral testing system, a partial discharge testing system, an infrared spectral testing system, and a computer.

[0007] The electric tree sample electrode system is installed inside the test chamber of the infrared spectroscopy test system;

[0008] The electric tree sample electrode system includes a sample mounting base, a grounding electrode, and a heater. The sample mounting base is used to clamp the two ends of the sample to be tested and can apply tensile or compressive stress to the sample. The grounding electrode is located on one side of the sample mounting base and is in contact with the side of the sample opposite to the tip of the needle electrode. The heater is in contact with the sample and is used to apply non-uniform thermal stress to the sample.

[0009] The complex waveform voltage generation system can be connected to the needle electrode, the grounding electrode is also connected to the leakage current testing system, the leakage current testing system is connected to the computer, the electroluminescence and digital imaging system is used to observe the test sample in bright field and dark field and is connected to the computer, the spectral testing system is used to perform spectral imaging of the test sample and is connected to the computer, and the input and output terminals of the partial discharge testing system are connected to the grounding terminal of the leakage current testing system and the computer, respectively.

[0010] Preferably, the sample mounting base includes a sample clamp and a fixing base. The sample clamp is capable of clamping the end of the sample to be tested. The sample clamp and the fixing base are connected by a knob. One end of the knob passes through the fixing base and is threadedly connected to the sample clamp. The sample clamp is provided with a stress sensor for detecting the magnitude of the tensile or compressive stress applied to the sample to be tested.

[0011] Preferably, multiple needle electrodes are spaced apart and parallel on the test sample. A complex waveform voltage generation system is connected in parallel with all needle electrodes. The electric tree sample electrode system also includes a stepping control console. The sample mounting base and grounding electrode are both set on the stepping control console. A heater is set on the test sample at the position corresponding to the tip of each needle electrode.

[0012] Preferably, the heater uses an arc-shaped heating band. In the thickness direction of the sample to be tested, the arc-shaped heating band is located above or below the tip of the needle electrode. The opening side of the arc-shaped heating band faces the tip of the needle electrode, and the tip of the needle electrode is located on the concave side of the arc-shaped heating band.

[0013] A thermocouple is installed on the arc-shaped heating belt, and both the arc-shaped heating belt and the thermocouple are connected to the heating controller.

[0014] Preferably, the arc-shaped heating bands are arranged symmetrically about the needle electrode.

[0015] Preferably, the complex waveform voltage generation system uses a complex waveform power supply, and the output terminal of the complex waveform power supply is connected to the needle electrode on the test sample; the spectral testing system uses a fiber optic spectrometer; the infrared spectral testing system uses an infrared spectral testing instrument; the grounding electrode uses a copper sheet electrode, one side of the copper sheet electrode is in contact with the surface of the test sample, and a copper rod is fixedly connected to one side of the copper sheet electrode.

[0016] Preferably, the leakage current testing system includes an ammeter and a protective resistor, which are connected in series. One end of the protective resistor is connected to a grounding electrode, and the other end of the protective resistor is grounded. The ammeter is set at the grounding end of the protective resistor.

[0017] The input terminal of the partial discharge test system is connected to the grounding line of the protective resistor, and the grounding terminals of the computer and the ammeter are also connected.

[0018] Preferably, the electroluminescence and digital imaging system includes an optical focusing imaging system and a CCD camera. The optical focusing imaging system includes a light source, a focusing lens, and a beam splitter. The light source is located below the test sample, and the focusing lens is located above the test sample. The focusing lens is used to focus the transmitted light from the needle tip of the needle electrode. The beam splitter is located at the focal point above the focusing lens. The CCD camera is located on one of the outgoing rays of the beam splitter, and the spectral testing system is located on the other outgoing ray of the beam splitter.

[0019] The infrared spectroscopy testing system has a window on its testing chamber for the light emitted from the light source to pass through.

[0020] Preferably, the variable frequency insulation electrothermal coupling electric tree aging multi-parameter in-situ characterization test system of the present invention further includes a dark chamber, in which the electric tree sample electrode system, electroluminescence and digital imaging system, spectral testing system and infrared spectral testing system are all located.

[0021] This invention also provides a multi-parameter in-situ characterization test method for the aging of variable frequency insulation electrothermal coupling electrical treeing, which uses the multi-parameter in-situ characterization test system for the aging of variable frequency insulation electrothermal coupling electrical treeing as described above, and includes the following process:

[0022] The test sample is mounted on the test sample holder, and a preset tensile or compressive stress is applied to the test sample through the test sample holder;

[0023] Adjust the electroluminescence and digital imaging system and the spectral testing system so that the tip and front area of ​​the needle electrode can be clearly imaged by the electroluminescence and digital imaging system and the spectral testing system;

[0024] The test sample is heated to a preset temperature using a heater. Then, a target frequency conversion voltage is applied to the needle electrode through a complex waveform voltage generation system. Subsequently, the distribution of light emission from the electrical tree channel and the morphological characteristics of the electrical tree are recorded by an electroluminescence and digital imaging system at set periodic intervals. The spectral testing system, partial discharge testing system, leakage current testing system, and infrared spectral testing system simultaneously record the spectral characteristics, partial discharge signal spectrum, current dynamic change curve, and infrared spectral characteristics during the development of the electrical tree. The spatial distribution cloud map of the electroluminescence location, the change of the intensity of the electroluminescence characteristic peak, the change of the intensity and number of partial discharges, the maximum value of the loop current, and the evolution of the functional groups in the electrical tree region are extracted.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] This invention, by setting up an electrical tree sample electrode system, a leakage current testing system, an electroluminescence and digital imaging system, a spectral testing system, a partial discharge testing system, and an infrared spectral testing system, enables multi-physics field coupling testing of electrical stress, thermal stress, and mechanical stress in insulating samples, more closely resembling actual working conditions. Furthermore, the strategy of simultaneous testing of multiple samples significantly improves testing efficiency. This invention can correlate electrical tree growth characteristics with leakage current, obtaining the loop current characteristics at different growth stages of electrical trees. Spectroscopic testing aids in the mechanistic exploration of the electrical tree initiation process. During the initiation and growth of electrical trees, their spectral characteristics change due to the generation of unsaturated groups and partial discharges. Spectroscopic testing can establish a connection between spectral characteristics and electrical tree growth characteristics, enabling mechanistic research. Electroluminescence testing can measure the conductivity and non-conductivity of electrical trees. Electroluminescence testing can display the location of partial discharges within the electrical tree channels, providing an indication of the conductivity of the electrical tree channels. Infrared spectral testing can reveal the changes in the functional groups of the insulating dielectric in the electrical tree region during electrical tree growth, obtaining its aging patterns and mechanisms. This system can realize online real-time measurement of the above-mentioned parameters, which is very different from the traditional offline testing method. It avoids the problem that the fatigue and damage accumulation effect caused by offline testing will fade and the electrical tree aging test will be out of touch with reality. It can effectively obtain the characterization of a variety of in-situ parameters in the electrical tree aging process and extract the correlation between various parameters, which is conducive to further and more accurately establishing the growth characteristics and mechanism of electrical trees in frequency conversion insulation.

[0027] Furthermore, the heater of this invention employs an arc-shaped heating band, which can apply a temperature gradient stress to the sample, better suited to the actual working conditions of uneven temperature distribution in frequency conversion insulation. Specifically, the arc-shaped heating band applies a temperature gradient stress to the sample, adhering to the sample surface and located at and in front of the needle tip. On one hand, the arc-shaped heating band can provide a wider range of uneven temperature distribution than existing straight heating bands; on the other hand, the edge effects of burrs and other impede observation in practical heating bands can adversely affect observation. The arc-shaped heating band can also maximize the provision of uneven temperature distribution while avoiding obstruction of the observation area near the needle tip, facilitating experimental observation and better suited to the actual working conditions of uneven temperature distribution in frequency conversion insulation. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the multi-parameter in-situ characterization and testing system for the aging of variable frequency insulation electrothermal coupling electric tree.

[0029] Figure 2(a) is a front view of the sample mounting base of the present invention after it holds the sample to be tested; Figure 2(b) is a top view of the sample mounting base of the present invention after it holds the sample to be tested; Figure 2(c) is a side view of Figure 2(b);

[0030] Figure 3 This is a schematic diagram illustrating the principle of heating the sample with a heating band in an embodiment of the present invention;

[0031] Figure 4 This is an example of electroluminescence observed in real-time under variable frequency voltage in a dark field according to an embodiment of the present invention.

[0032] In the diagram, 1-complex waveform power supply, 2-needle electrode, 3-light source, 4-test sample, 5-copper rod, 6-ammeter, 7-grounding, 8-partial discharge test system, 9-focusing lens, 10-spectrum splitter, 11-fiber optic spectrometer, 12-computer, 13-CCD camera, 14-infrared spectrometer cavity, 15-stepping control console, 16-stand, 17-dark chamber, 20-sample holder, 21-fixed base, 22-knob, 23-pressure display, 24-arc heating belt, 25-heating controller. Detailed Implementation

[0033] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0034] The objective of this invention is to achieve in-situ characterization testing of multiple parameters in the aging of electrical trees in insulating dielectrics. Furthermore, this invention also considers the degradation of electrical trees in solid insulating materials under the influence of complex voltage waveforms from frequency conversion. Simultaneously, it couples in the complex multi-field physical processes involved in the initiation and growth of electrical trees.

[0035] Reference Figure 1The present invention provides a multi-parameter in-situ characterization and testing system for frequency conversion insulation electrothermal coupling electric tree aging, comprising a complex waveform voltage generation system, an electric tree sample electrode system, a leakage current testing system, an electroluminescence and digital imaging system, a spectral testing system, a partial discharge testing system, an infrared spectral testing system, and a multi-stress coupling testing system for voltage, temperature, and mechanical force.

[0036] The complex waveform voltage generation system includes an arbitrary waveform generator and waveform amplifier with a frequency of 1kHz or higher, which can realize voltage waveform output including but not limited to unipolar / bipolar square waves, triangular waves, and sine waves.

[0037] The electrical tree specimen electrode system includes a specimen mounting base, a grounding electrode, and a heater. The specimen mounting base holds the electrical tree specimen in place. When multiple needle electrodes are installed on the electrical tree specimen, these needle electrodes are connected in parallel to the output of a complex waveform voltage generation system. The grounding electrode is a copper rod, which is grounded. The specimen mounting base clamps both ends of the electrical tree specimen, allowing tensile / compressive stress to be applied. The applied stress magnitude is displayed by a pressure sensor. A temperature gradient is applied to the electrical tree specimen via the heater.

[0038] The leakage current testing system includes a galvanometer and a protective resistor. It can dynamically acquire the current changes in the circuit in real time. It can also switch the high-frequency power supply to DC output at any stage of electrical tree growth to obtain the DC resistance characteristics of different electrical tree growth stages and transmit them to a computer for analysis.

[0039] The electroluminescence and digital imaging system includes a high-sensitivity CCD, which can simultaneously perform bright-field and dark-field observations. Bright-field observations are used to observe the morphology of electrical trees and extract characteristic parameters such as the length, width, and fractal dimension of the electrical trees. Dark-field observations are used to obtain the distribution characteristics of electroluminescence properties within the electrical tree channels.

[0040] The spectral testing system includes a lens assembly, fiber optic probe, grating, and spectrometer, enabling spectral imaging in the 200–1000 nm wavelength range, covering the spectral range of electrical dendrite initiation and growth processes. The electroluminescence and digital imaging systems share a lens assembly (i.e., an optical focusing imaging system) with the spectral testing system.

[0041] The partial discharge testing system includes a high-frequency antenna detector and data analysis and processing software (existing mature software), which can obtain high-frequency signals in the partial discharge during the growth process of electrical trees and establish the correlation between the signals and the growth characteristics of electrical trees.

[0042] The infrared spectroscopy testing system is an infrared spectroscopy testing instrument. The testing chamber of the original infrared spectroscopy instrument can be modified to accommodate an electrode system for testing electrical tree branches. Simultaneously, proper insulation treatment should be performed for high-voltage connections.

[0043] In addition to the electric and force fields described above, the multi-field coupling test system also includes an electric heating system consisting of a digital temperature controller and an arc-shaped heating belt.

[0044] The specific method of using this invention is as follows: First, the prepared test sample is clamped on the sample mounting base, and the target tensile / compressive stress is applied to the test sample through the sample mounting base. The focal plane of the microscope and the position of the sample are adjusted so that the tip and the front area of ​​the computer software interface are clearly visible. Second, the heating device (i.e., the heater) is turned on for a preset time, and after the temperature distribution stabilizes, A target frequency-converted voltage is applied to the high-voltage needle electrode. Then, a high-sensitivity fluorescence CCD is used to record the luminescence distribution and morphological characteristics of the electrical tree channels at set intervals. A fiber optic spectrometer, a partial discharge testing system, a loop current testing system, and an infrared spectroscopy testing system simultaneously record the spectral characteristics, partial discharge signal spectrum, current dynamic change curve, and infrared spectral characteristics during the electrical tree development process. Spatial distribution cloud maps of electroluminescence positions, changes in the intensity of electroluminescence characteristic peaks, changes in the intensity and frequency of partial discharges, the maximum value of the loop current, and the evolution of characteristic functional groups in the electrical tree region are extracted. Finally, a database linking the electrical tree characteristic parameters with the synchronously acquired physical and chemical parameters is established to obtain the in-situ parameter evolution law during the electrical tree growth process and to propose the aging mechanism of electrical trees under electrothermal-mechanical multi-field coupling conditions. The entire life cycle of the electrical tree mainly includes five stages: initiation, early growth, middle growth, late growth, and breakdown. Breakdown occurs rapidly under high-frequency voltage and is not considered here. During the initial stage of electrical tree initiation, the partial discharge signal is very low, and the current in the circuit is small. The performance evolution of the sample can be obtained through electroluminescence intensity and spectral characteristic peaks. In the early stage of electrical tree growth, the partial discharge signal increases, but the current in the circuit is still small. Correlation with parameters such as the length and width of the electrical tree can be established through partial discharge spectra, electroluminescence position distribution, and spectral characteristic peak positions. In the middle stage of electrical tree growth, changes in partial discharge, circuit current, and electroluminescence are all significant. Correlation with parameters such as the length and width of the electrical tree can be established through partial discharge spectra, circuit current values, electroluminescence position distribution, and spectral characteristic peaks. In the later stage of electrical tree growth, the growth rate accelerates significantly. To protect the ammeter, circuit current testing cannot be performed at this stage. Correlation with the length and width of the electrical tree can be established through partial discharge spectra, electroluminescence position distribution, and spectral characteristic peaks. Furthermore, infrared spectroscopy, being unaffected by electrical parameters, can be performed throughout the entire lifecycle of electrical tree initiation, growth, and breakdown to obtain changes in physicochemical structural parameters.

[0045] The database obtained through this invention allows for: ① obtaining the location and intensity of electroluminescence within the electrical tree channel under variable frequency voltage by combining real-time spectroscopy with fluorescence CCD imaging and fiber optic spectroscopy; ② obtaining the correlation between the conductivity of the electrical tree channel and the residual insulation strength of the sample with the electrical tree morphology through current changes; ③ obtaining the partial discharge spectrum characteristics under the coupling effect of electrical tree morphology and voltage waveform in real time; and ④ obtaining the variation law of characteristic functional groups of the sample under the coupling effect of electrical tree morphology and voltage waveform in real time. Ultimately, this enables real-time, in-situ research on the growth law and mechanism of electrical trees under electrothermal-mechanical multi-stress coupling conditions.

[0046] Example

[0047] like Figure 1 As shown, this embodiment of the variable frequency insulation electrothermal coupling electric tree aging multi-parameter in-situ characterization test system includes a complex waveform voltage generation system, an electric tree sample electrode system, a leakage current test system, an electroluminescence and digital imaging system, a spectral test system, a partial discharge test system 8, an infrared spectral test system, a computer 12, and a darkroom 17. Referring to Figures 2(a)-2(c), the electric tree sample electrode system includes a sample mounting base, a grounding electrode, and a heater. The sample mounting base includes a sample holder 20 and a fixing base 21. The sample holder 20 can clamp the end of the test sample 4. The sample holder 20 and the fixing base 21 are connected by a knob 22. One end of the knob 22 passes through the fixing base 21 and is threadedly connected to the sample holder 20. The sample holder 20 is provided with a stress sensor for detecting the magnitude of the tensile or compressive stress applied to the test sample 4. The sample holder 20 and the fixing base 21 can clamp both ends of the test sample 4 and apply tensile or compressive stress to the test sample 4. Referring to Figure 2... (a) By rotating the knobs 22 on both sides, the sample clamps 20 and the fixing base 21 on both sides can be moved closer or further apart, thereby applying compressive or tensile stress to the test sample 4; the grounding electrode is a copper sheet electrode, so as to... Figure 1 Taking the orientation shown as an example, the right surface of the copper sheet electrode is in contact with the left surface of the test sample 4, and a copper rod 5 is fixedly connected to one side of the copper sheet electrode; In this embodiment, referring to Figure 2(b), multiple needle electrodes 2 are spaced apart and parallel on the test sample 4, and a complex waveform voltage generation system is connected in parallel with all needle electrodes 2. The electric tree sample electrode system also includes a stepping control console 15, and the sample mounting base and grounding electrode are both set on the stepping control console 15. By controlling the stepping stage, multiple samples (each needle electrode 2 on the test sample 4 corresponds to a test site, and multiple needle electrodes 2 are set on the test sample 4 of this invention, which is equivalent to multiple samples) can be observed sequentially; A heater is set on the test sample 4 at the position corresponding to the tip of each needle electrode 2. The heater is in contact with the test sample 4 and is used to apply non-uniform thermal stress to the test sample 4; Specifically, refer to Figure 3The heater uses an arc-shaped heating band 24, which is positioned along the thickness direction of the sample 4 to be tested. Figure 3 (as shown in the direction perpendicular to the paper), the arc-shaped heating band 24 is located above or below the tip of the needle electrode 2, and the arc-shaped heating band 24 has an opening (as shown in the direction perpendicular to the paper). Figure 3 As shown, the downward-facing side (its open side) of the arc-shaped heating band 24 faces the tip of the needle electrode 2, and the tip of the needle electrode 2 is located on the concave side of the arc-shaped heating band 24 (i.e., the tip of the needle electrode 2 protrudes downwards from the top of the arc-shaped heating band 24). A thermocouple is mounted on the arc-shaped heating band 24, and both the arc-shaped heating band 24 and the thermocouple are connected to the heating controller 25. Generally, the arc-shaped heating band 24 is arranged symmetrically about the needle electrode 2. Uneven thermal stress can be applied to the test sample 4 through the arc-shaped heating band 24.

[0048] The complex waveform voltage generation system uses a complex waveform power supply 1, the output of which is connected to the needle electrode 2 on the test sample 4. The infrared spectroscopy testing system uses an infrared spectroscopy instrument. The spectral testing system uses a fiber optic spectrometer 11. The leakage current testing system includes an ammeter 6 and a protective resistor, which are connected in series. One end of the protective resistor is connected to the grounding electrode, and the other end is grounded. The ammeter 6 is placed at the grounding end of the protective resistor. The input of the partial discharge testing system 8 is connected to the grounding line of the protective resistor. The computer 12 is connected to the grounding end of the ammeter 6. The partial discharge testing system 8 can measure the high-frequency pulse discharge signal during the growth process of electrical tree branches in real time and can store and analyze it. The electroluminescence and digital imaging system includes an optical focusing imaging system and a CCD camera 13. The optical focusing imaging system includes a light source 3, a focusing lens 9, and a beam splitter 10. The light source 3 is located below the test sample 4, and the focusing lens 9 is located above the test sample 4. The focusing lens 9 is used to focus the transmitted light from the tip of the needle electrode 2. The beam splitter 10 is located at the focal point above the focusing lens 9. The CCD camera 13 is positioned on one of the output rays of the beam splitter 10, and the spectral testing system is positioned on the other output ray of the beam splitter 10. The infrared spectral testing system has a window on its test cavity for the light emitted from the light source 3 to pass through. The focusing lens 9 converges the light signals during the initiation and growth of electric trees, and splits them into two paths by the beam splitter 10. One path enters the CCD camera, enabling the recording and analysis of electric tree morphology under bright field and the testing of electroluminescence distribution under dark field. The other path enters the fiber optic spectrometer, enabling real-time dynamic recording of the spectrum during the growth of electric trees. In this embodiment, the electric tree sample electrode system, electroluminescence and digital imaging system, spectral testing system, and infrared spectral testing system are all housed within darkroom 17. The measurements are performed in darkroom 17 to avoid interference from ambient light sources. Simultaneously, all measurement data are transmitted to a computer for storage and analysis.

[0049] Recording the morphology of electrical trees allows for the characterization and analysis of their growth parameters (length, width, fractal dimension, cumulative damage, etc.). The spatial distribution of electroluminescence within the tree channels reveals the conductivity distribution at different growth stages and in different parts of the channels. Spectral data reflects the spectral characteristics during the initiation and growth of electrical trees. These spectral characteristics change due to the generation of unsaturated groups and partial discharges; therefore, spectral testing can establish a correlation between spectral characteristics and the growth properties of electrical trees.

[0050] By placing the electric tree electrode system in the infrared spectrometer cavity 14, infrared spectral data during the electric tree growth process can be obtained, and changes in chemical functional groups during the electric tree growth process can be extracted.

[0051] Based on the above scheme, this invention performs real-time online observation in a dark field, using variable frequency voltage, to obtain... Figure 4 The electroluminescence diagram shown is as follows: Figure 4 In the image, the luminescent part is a dendritic channel where partial discharge occurs, indicating that it is non-conductive. From the needle tip to the luminescent position, there are also invisible electrical dendritic channels, indicating that they are conductive.

[0052] In this way, the above testing system can be used to simultaneously measure the dynamic data of electric tree growth, electroluminescence location distribution, spectral data, current data, partial discharge data and infrared spectral data during the electric tree growth process. It can realize the real-time acquisition of in-situ parameters at different stages of electric tree initiation and growth, obtain the correlation characteristics between different characteristic parameters, solve the problem of mutual independence between traditional characterization methods, and establish the real-time characteristics and mechanisms of multiple parameters and electric tree growth dynamics.

[0053] The system described above in this invention can achieve electric tree growth testing under the action of multiple physical fields by applying electrical stress, mechanical stress, and thermal stress.

Claims

1. A variable frequency insulation electric heating force coupling electric treeing aging multi-parameter in-situ characterization test system, characterized in that, The system comprises a complex waveform voltage generating system, an electrical tree sample electrode system, a leakage current testing system, an electroluminescence and digital imaging system, a spectrum testing system, a partial discharge testing system (8), an infrared spectrum testing system and a computer (12); The electrical tree sample electrode system is arranged in a testing cavity of the infrared spectrum testing system; The electrical tree sample electrode system comprises a sample mounting seat, a grounding electrode and a heater, the sample mounting seat is used for clamping two ends of a sample (4) to be tested and can apply a tensile stress or a compressive stress to the sample (4) to be tested, the grounding electrode is arranged on one side of the sample mounting seat and is in contact with a side of the sample (4) to be tested opposite to a tip of a needle electrode (2), and the heater is in contact with the sample (4) to be tested and is used for applying a non-uniform thermal stress to the sample (4) to be tested; The complex waveform voltage generating system is connected with the needle electrode (2), the grounding electrode is further connected with the leakage current testing system, the leakage current testing system is connected with the computer (12), the electroluminescence and digital imaging system is used for observing the sample (4) to be tested in bright field and dark field and is connected with the computer (12), the spectrum testing system is used for performing spectrum imaging on the sample (4) to be tested and is connected with the computer (12), and input and output ends of the partial discharge testing system (8) are connected with a grounding end of the leakage current testing system and the computer (12) respectively; The sample mounting seat comprises a sample clamping piece (20) and a fixing seat (21), the sample clamping piece (20) can clamp end portions of the sample (4) to be tested, the sample clamping piece (20) and the fixing seat (21) are connected through a knob (22), one end of the knob (22) penetrates through the fixing seat (21) and is threadedly connected with the sample clamping piece (20), and a stress sensor for detecting a magnitude of the tensile stress or the compressive stress applied to the sample (4) to be tested is arranged on the sample clamping piece (20); The heater adopts an arc-shaped heating belt (24), in a thickness direction of the sample (4) to be tested, the arc-shaped heating belt (24) is located on an upper side or a lower side of a needle tip portion of the needle electrode (2), an opening side of the arc-shaped heating belt (24) faces the needle tip portion of the needle electrode (2), and the needle tip of the needle electrode (2) is located on a concave side of the arc-shaped heating belt (24); A thermocouple is arranged on the arc-shaped heating belt (24), and the arc-shaped heating belt (24) and the thermocouple are connected with a heating controller (25); The electroluminescence and digital imaging system comprises an optical focusing imaging system and a high-sensitivity fluorescent CCD camera, the optical focusing imaging system comprises a light source (3), a focusing lens (9) and a light splitter (10), the light source (3) is located below the sample (4) to be tested, the focusing lens (9) is located above the sample (4) to be tested, the focusing lens (9) is used for focusing transmitted light near the needle tip of the needle electrode (2), the light splitter (10) is arranged at a focal point above the focusing lens (9), the high-sensitivity fluorescent CCD camera is arranged on one light exit line of the light splitter (10), and the spectrum testing system is arranged on another light exit line of the light splitter (10); A window is arranged on the testing cavity of the infrared spectrum testing system for the light source (3) to pass through. The leakage current test system comprises a current meter (6) and a protective resistor, the current meter (6) and the protective resistor are connected in series, one end of the protective resistor is connected with the grounding electrode, the other end of the protective resistor is grounded, and the current meter (6) is arranged at the grounding end of the protective resistor; The partial discharge test system (8) comprises a high-frequency antenna probe and data analysis processing software, an input end of the partial discharge test system (8) is connected to the grounding circuit of the protective resistor, and the grounding ends of the computer (12) and the current meter (6) are connected.

2. The variable frequency insulation electric-thermal coupled electrical treeing multi-parameter in-situ characterization test system according to claim 1, characterized in that, A plurality of needle electrodes (2) are arranged on the to-be-tested sample (4) in a spaced and parallel manner, a complex waveform voltage generating system is connected in parallel with all the needle electrodes (2), the electrical treeing sample electrode system further comprises a stepping control console (15), and the sample mounting seat and the grounding electrode are arranged on the stepping control console (15); a heater is arranged on the to-be-tested sample (4) at a position corresponding to the tip of each needle electrode (2). 3.The variable frequency insulation electric-thermal force coupling electrical tree aging multi-parameter in-situ characterization test system according to claim 1, characterized in that, The arc-shaped heating belt (24) is symmetrically arranged about the needle electrode (2).

4. The variable frequency dielectric heating power coupled electrical treeing multi-parameter in-situ characterization test system of claim 1, wherein, The complex waveform voltage generating system adopts a complex waveform power supply (1), the output end of the complex waveform power supply (1) is connected with the needle electrode (2) on the to-be-tested sample (4); the spectral test system adopts a fiber spectrum analyzer (11); the infrared spectrum test system adopts an infrared spectrum test instrument; the grounding electrode adopts a copper sheet electrode, one side surface of the copper sheet electrode is in contact with the surface of the to-be-tested sample (4), and the copper sheet electrode is fixedly connected with a copper rod (5) on one side.

5. The variable frequency dielectric heating power coupled electrical treeing multi-parameter in-situ characterization test system according to claim 1, characterized in that, The electrical treeing sample electrode system, the electroluminescence and digital imaging system, the spectral test system and the infrared spectrum test system are all arranged in the darkroom (17).

6. A method for in-situ characterization and testing of multi-parameters of variable frequency dielectric heating power coupled electrical treeing aging, characterized in that, The method is performed by using the variable-frequency insulation electric heating force coupling electrical treeing aging multi-parameter in-situ characterization test system according to any one of claims 1-5, and comprises the following processes: The to-be-tested sample (4) is mounted on the sample mounting seat, and a preset tensile stress or compressive stress is applied to the to-be-tested sample (4) through the sample mounting seat; The electroluminescence and digital imaging system and the spectral test system are adjusted, so that the tip of the needle electrode (2) and the front area can be clearly imaged by the electroluminescence and digital imaging system and the spectral test system; The heater is used to heat the to-be-tested sample (4), after the to-be-tested sample (4) is heated to a preset temperature, the target variable-frequency voltage is applied to the needle electrode (2) through the complex waveform voltage generating system; then, the electroluminescence and digital imaging system is used to take pictures at a set periodic interval to record the luminescence distribution of the electrical treeing channel and the electrical treeing appearance characteristics, the spectral test system, the partial discharge test system (8), the leakage current test system and the infrared spectrum test system are used to simultaneously record the spectral characteristics, the partial discharge signal spectrum, the current dynamic change curve and the infrared spectrum characteristics in the electrical treeing development process, respectively, and the electroluminescence position space distribution cloud picture, the electroluminescence characteristic peak position intensity change, the partial discharge intensity and frequency change, the maximum value of the loop current and the evolution of the electrical treeing region characteristic functional group are extracted.

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