High-pressure gas discharge broadband transfer current measurement method

Abstract

The invention relates to a high-pressure gas discharge broadband transfer current measurement method, which comprises the following steps of: establishing a broadband high-voltage electrode system to provide a transfer path for partial discharge charges of gas, and performing pulse irradiation on an electron excitation target surface on a lower plate electrode by using a picosecond pulse laser; the electron excitation target surface is connected in series with low-inductance impedance, and discharge transfer current is converted into a voltage signal through the low-inductance impedance; the high-speed signal acquisition equipment obtains a transfer current time domain waveform based on the voltage signal; adjusting the electrode distance between the plate electrodes based on the transfer current time domain waveform until the transfer current time domain waveform is of a charge translation type; an electron excitation target surface area is replaced by a metal short tip electrode, other experiment conditions are kept unchanged, and the discharge transfer current time domain waveform obtained through measurement at the moment is the high-pressure gas partial discharge broadband transfer current waveform.

Description

Technical Field

[0001] The invention relates to the technical field of high-voltage gas discharge broadband transfer current measurement, and in particular to a high-voltage gas discharge broadband transfer current measurement method. Background Art

[0002] Partial discharge refers to the local electrical breakdown phenomenon that occurs in the insulating medium of electrical equipment. In a gas atmosphere, this discharge is usually caused by local electric field distortion. The occurrence of partial discharge poses a serious threat to the insulation performance of power equipment and may cause gap breakdown under overvoltage, threatening the safe operation of equipment and power grids. Traditional partial discharge detection methods mainly rely on the pulse current method, which diagnoses partial discharge activities by measuring the pulse current signal caused by partial discharge. These methods usually focus on the amplitude and phase information of the partial discharge signal, but due to the limited bandwidth of the general test system, the measured discharge current pulse signal cannot fully reflect the broadband physical information of the partial discharge process. This means that traditional methods cannot reveal the charge transport characteristics and migration mechanism of the entire process from initial electron generation to charge dissipation, which limits the in-depth understanding and analysis of the partial discharge mechanism.

[0003] The local discharge process is extremely short, and the entire physical process is completed within the time range of nanoseconds or even picoseconds. The charge migration movement caused by local discharge between electrodes causes a pulse current in the circuit. Local discharge detection based on the pulse current method can be regarded as the macroscopic response of the microscopic discharge process in the external circuit. However, due to the broadband characteristics of the local discharge pulse current signal, the traditional narrowband detection system cannot accurately capture these rapidly changing signals, resulting in the inability to obtain the true characteristics of the local discharge pulse waveform. In addition, the local discharge current obtained by most experimental systems will be affected by the background electric field, resulting in the difficulty of effectively obtaining the initial electron multiplication and migration current caused by the local electric field distortion even with broadband measurement. In addition, the electromagnetic mode wave excited by the local discharge and its propagation process are also related to the excitation process of the discharge current. If the broadband transfer current characteristics of the local discharge cannot be clearly grasped, there is also a lack of basis for electromagnetic wave propagation, coupling and signal interpretation.

[0004] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0005] The present invention provides a method for measuring high-voltage gas discharge broadband transfer current, which reduces the influence factors of external loop bandwidth and background electric field and utilizes the experimental determination of discharge self-sustaining critical conditions to obtain a more realistic partial discharge transfer current waveform.

[0006] A method for measuring a high-voltage gas discharge broadband transfer current comprises: Step 1, establishing a broadband high-voltage electrode system to provide a transfer path for gas partial discharge charges, wherein the high-voltage electrode system is powered by a DC high-voltage power supply to generate a stable high electric field between flat plate electrodes, wherein the flat plate electrodes include an upper plate electrode and a lower plate electrode with adjustable electrode spacing, wherein the lower plate electrode is provided with an electron excitation target surface, and the upper plate electrode is provided with a picosecond pulse laser facing the electron excitation target surface; Step 2, pulse irradiation of the electron excitation target surface on the lower plate electrode by a picosecond pulse laser; Step 3, the electron excitation target surface is connected in series with a low-inductance impedance, and the discharge transfer current is converted into a voltage signal through the low-inductance impedance; Step 4, the high-speed signal acquisition device obtains the time domain waveform of the transfer current based on the voltage signal; Step 5, adjusting the electrode spacing between the plate electrodes based on the transfer current time domain waveform until the transfer current time domain waveform is a charge translation type; Step 6, replace the electron excitation target surface area with a metal short-pointed electrode, and keep other experimental conditions unchanged. At this time, the measured discharge transfer current time domain waveform is a high-pressure gas partial discharge broadband transfer current waveform.

[0007] In the method for measuring broadband transfer current of high-voltage gas discharge, the flat plate electrodes are composed of parallel circular flat brass electrodes, the surface roughness of the circular flat brass electrodes is not greater than 0.5 μm, the root mean square error of the electrode spacing d is not greater than 0.5 mm, the diameter of the flat plate electrodes is 10-15 cm, and the minimum radius of curvature at the edge of the inner surface is not less than 0.5 cm; wherein, an upper through hole is left at the center of the upper plate electrode, the diameter of the upper through hole is 3 mm, and the radius of curvature of the edge of the upper through hole is 0.25 mm; a lower through hole is left at the center of the lower plate electrode, and the diameter of the lower through hole is 12 mm.

[0008] In the method for measuring the broadband transfer current of high-voltage gas discharge, the voltage of the upper plate electrode is U Adjustable within the range of (20~100)×d, the maximum power of the DC high voltage power supply P Not less than 50×d, where the voltage is in kV, the electrode spacing d is in cm, and the maximum power of the DC high voltage power supply is P The unit is kVA.

[0009] In the method for measuring high-voltage gas discharge broadband transfer current, a lower through hole is left at the center of the lower plate electrode, the lower through hole is filled with epoxy resin material, and the surface of the central area of ​​the epoxy resin in the hole is plasma sputtered to form a circular electron excitation target surface, and the electron excitation target surface is connected in series with a low-inductance impedance through a metal wire preset inside the epoxy resin.

[0010] In the method for measuring the broadband transfer current of high-voltage gas discharge, the sputtering material of plasma sputtering is silver, the diameter of the electron excitation target surface is 4 mm, the diameter of the metal wire is 2 mm, and the tail of the metal wire is connected in series with k parallel low-inductance resistors, and the resistance of a single low-inductance resistor is kZ. c Ω, Z c is the transmission impedance of the RF cable.

[0011] In the high-voltage gas discharge wide-band transfer current measurement method, the main body of the metal short-tip electrode is cylindrical with a diameter of 3 mm, the tip profile is approximately a Gaussian profile, and the minimum curvature radius is 250 μm. The metal short-tip electrode is embedded in the center of the epoxy resin material, with the tip facing the upper plate electrode, the length of the exposed part of the epoxy resin is 5 mm, and the tail is connected to the metal wire in the epoxy resin.

[0012] In the high-voltage gas discharge broadband transfer current measurement method, the wavelength of the picosecond pulse laser is 266nm or 343nm, the peak power of irradiating the target surface is between 40kW and 250kW, and a collimation system is used to irradiate the pulse laser through the through hole of the upper plate electrode to the electron excitation target surface range on the surface of the lower plate electrode.

[0013] In the high-voltage gas discharge broadband transfer current measurement method, the picosecond pulse laser and the high-speed signal acquisition device are externally synchronously triggered, the analog signal detection bandwidth of the high-speed signal acquisition device is not less than 2 GHz, and the sampling rate is not less than 10 GS / s.

[0014] In the method for measuring a high-voltage gas discharge wide-band transfer current, the step 5 of adjusting the electrode spacing between the plate electrodes based on the transfer current time domain waveform includes: The initial electron generation time is t s The moment when the electrons reach the upper electrode is t a , the current waveform t s ~t a The current increase rate of the stage is , I a is the time when the electron reaches the upper electrode t a The corresponding current amplitude; I s is the initial electron generation time t s The corresponding current amplitude. t s and t aIt can be determined by linear segmented fitting of the transfer current waveform, that is, the time corresponding to the first and second linear segment turning points is t s , the corresponding time of the second and third linear segment turning points is t a .when r ≥3%, it is judged that there is a charge multiplication process. At this time, the external DC voltage is maintained. U Increase the distance between the plate electrodes under the same conditions d , repeat steps 1 to 4; when r ≤-3%, it is judged that there is a charge decay process. At this time, the external DC voltage is maintained. U Reduce the distance between the plate electrodes under the same conditions d , repeat steps 1 to 4; Repeat the above process until -3%< r When it is less than 3%, the time domain waveform of the transfer current is considered to be a charge translation type, the electrode spacing is no longer adjusted, and the charge transfer process is in dynamic equilibrium.

[0015] In the method for measuring broadband transfer current of high-voltage gas discharge, the high-voltage electrode system also includes a metal sealed cavity for accommodating the flat electrode, and the metal sealed cavity includes a high-voltage bushing, a gas exchange valve, a signal terminal and a grounding wire.

[0016] Compared with the prior art, the present invention has the following advantages: compared with the direct current measurement method in the prior art, the present invention adopts a laser-excited initial electron pre-test method, which can determine the background electric field used for accurately measuring the discharge transfer current, thereby obtaining the transfer current ionized in the distorted electric field region without background electric field electron proliferation; the structural design of epoxy resin and lower plate electrode, the matching of low-inductance resistor and radio frequency cable impedance, and parameter design verification are adopted to greatly shorten the response time of the measurement loop, and the test loop bandwidth can reach GHz, avoiding the waveform distortion caused by the prior art without considering the loop parameters; it can not only be used for experimental research on the discharge mechanism, but also can be used to determine the critical ionization conditions of different gases, and can also provide necessary current waveform parameters for electromagnetic wave measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of illustrating the preferred embodiments and are not considered to be limitations of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work. Moreover, the same reference numerals are used to represent the same components throughout the drawings.

[0018] In the attached picture: Figure 1 It is a schematic structural diagram of the broadband high-voltage electrode system of the present invention; Figure 2 It is a structural schematic diagram of a test electrode system in which the electron excitation target surface area is replaced by a metal short-pointed electrode in the present invention; Figure 3 A schematic diagram of the connection of a low-inductance resistor according to an embodiment of the present invention; Figure 4 A schematic diagram of current trend of charge multiplication according to an embodiment of the present invention; Figure 5 A schematic diagram of current trend of charge dissipation according to an embodiment of the present invention; Figure 6 A schematic diagram of current trend of charge translation according to an embodiment of the present invention; Figure 7 A schematic diagram of a current measurement circuit according to an embodiment of the present invention; Figure 8 for Figure 7 A schematic diagram of an equivalent circuit of a current measurement circuit according to an embodiment of the present invention; Fig. 9 It is a schematic diagram of the simulation structure of the metal closed cavity according to an embodiment of the present invention; Fig.10 for Fig. 9 A schematic diagram of electric field distribution of a simulated structure of a metal closed cavity according to an embodiment of the present invention; Fig.11 FIG. 4 is a schematic diagram of a self-sustaining broadband transfer current waveform according to an embodiment of the present invention.

[0019] The present invention is further explained below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0020] The specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0021] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the attached claims.

[0022] To facilitate understanding of the embodiments of the present invention, further explanation will be given below by taking specific embodiments as examples in conjunction with the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.

[0023] like Figures 1 to 11 As shown, a method for measuring a high-voltage gas discharge broadband transfer current comprises the following steps: Step 1, establishing a broadband high-voltage electrode system to provide a transfer path for gas partial discharge charges, wherein the high-voltage electrode system is powered by a DC high-voltage power supply to generate a stable high electric field between flat plate electrodes, wherein the flat plate electrodes include an upper plate electrode and a lower plate electrode with adjustable electrode spacing, wherein the lower plate electrode is provided with an electron excitation target surface, and the upper plate electrode is provided with a picosecond pulse laser facing the electron excitation target surface; Step 2, pulse irradiation of the electron excitation target surface on the lower plate electrode by a picosecond pulse laser; Step 3, the electron excitation target surface is connected in series with a low-inductance impedance, and the discharge transfer current is converted into a voltage signal through the low-inductance impedance; Step 4, the high-speed signal acquisition device obtains the time domain waveform of the transfer current based on the voltage signal; Step 5, adjusting the electrode spacing between the plate electrodes based on the transfer current time domain waveform until the transfer current time domain waveform is a charge translation type; Step 6, replace the electron excitation target surface area with a metal short-pointed electrode, and keep other experimental conditions unchanged. At this time, the measured discharge transfer current time domain waveform is a high-pressure gas partial discharge broadband transfer current waveform.

[0024] In a preferred embodiment of the high-voltage gas discharge broadband transfer current measurement method, the flat plate electrodes are composed of parallel circular flat brass electrodes, the surface roughness of the circular flat brass electrodes is not greater than 0.5 μm, the root mean square error of the electrode spacing d is not greater than 0.5 mm, the diameter of the flat plate electrodes is 10~15 cm, and the minimum radius of curvature at the edge of the inner surface is not less than 0.5 cm; wherein, an upper through hole is left at the center of the upper plate electrode, the diameter of the upper through hole is 3 mm, and the radius of curvature of the edge of the upper through hole is 0.25 mm; a lower through hole is left at the center of the lower plate electrode, and the diameter of the lower through hole is 12 mm.

[0025] In a preferred embodiment of the method for measuring the broadband transfer current of a high-voltage gas discharge, the voltage of the upper plate electrode is U Adjustable within the range of (20~100)×d, the maximum power of the DC high voltage power supply P Not less than 50×d, where the voltage is in kV, the electrode spacing d is in cm, and the maximum power of the DC high voltage power supply is P The unit is kVA.

[0026] In a preferred embodiment of the high-voltage gas discharge wide-band transfer current measurement method, a lower through hole is left at the center of the lower plate electrode, the lower through hole is filled with epoxy resin material, and the surface of the central area of ​​the epoxy resin in the hole is plasma sputtered to form a circular electron excitation target surface, and the electron excitation target surface is connected in series with the low-inductance impedance through a metal wire preset inside the epoxy resin.

[0027] In a preferred embodiment of the high-voltage gas discharge broadband transfer current measurement method, the sputtering material of the plasma sputtering is silver, the diameter of the electron excitation target surface is 4 mm, the diameter of the metal wire is 2 mm, and the tail of the metal wire is connected in series with k parallel low-inductance resistors, and the resistance of a single low-inductance resistor is kZ c Ω, Z c is the transmission impedance of the RF cable.

[0028] In a preferred embodiment of the high-voltage gas discharge wide-band transfer current measurement method, the main body of the metal short-tip electrode is cylindrical with a diameter of 3 mm, the tip profile is approximately a Gaussian profile, the minimum curvature radius is 250 μm, the metal short-tip electrode is embedded in the center of the epoxy resin material, the tip faces the upper plate electrode, the length of the exposed part of the epoxy resin is 5 mm, and the tail is connected to the metal wire in the epoxy resin.

[0029] In a preferred embodiment of the high-voltage gas discharge broadband transfer current measurement method, the wavelength of the picosecond pulse laser is 266nm or 343nm, the peak power of irradiating the target surface is between 40kW and 250kW, and a collimation system is used to irradiate the pulse laser through the through hole of the upper plate electrode to the electron excitation target surface range on the surface of the lower plate electrode.

[0030] In a preferred embodiment of the high-voltage gas discharge broadband transfer current measurement method, the picosecond pulse laser and the high-speed signal acquisition device are externally synchronously triggered, the analog signal detection bandwidth of the high-speed signal acquisition device is not less than 2 GHz, and the sampling rate is not less than 10 GS / s.

[0031] In a preferred embodiment of the high-voltage gas discharge broadband transfer current measurement method, step 5 of adjusting the electrode spacing between the plate electrodes based on the transfer current time domain waveform includes: The initial electron generation time is t s The moment when the electrons reach the upper electrode is t a , the current waveform t s ~t a The current increase rate of the stage is , I a is the time when the electron reaches the upper electrode t a The corresponding current amplitude; I s is the initial electron generation time t s The corresponding current amplitude. t s and t a It can be determined by linear segmented fitting of the transfer current waveform, that is, the time corresponding to the first and second linear segment turning points is t s , the corresponding time of the second and third linear segment turning points is t a .when r ≥3%, it is judged that there is a charge multiplication process. At this time, the external DC voltage is maintained. U Increase the distance between the plate electrodes under the same conditions d , repeat steps 1 to 4; when r ≤-3%, it is judged that there is a charge decay process. At this time, the external DC voltage is maintained. U Reduce the distance between the plate electrodes under the same conditions d , repeat steps 1 to 4; Repeat the above process until -3%< r When it is less than 3%, the time domain waveform of the transfer current is considered to be a charge translation type, the electrode spacing is no longer adjusted, and the charge transfer process is in dynamic equilibrium.

[0032] In a preferred embodiment of the high-voltage gas discharge broadband transfer current measurement method, the high-voltage electrode system also includes a metal sealed cavity accommodating the flat electrode, and the metal sealed cavity includes a high-voltage bushing, a ventilation valve, a signal terminal and a grounding wire.

[0033] In one embodiment, the gas inside the metal sealed cavity can be replaced with a different single component or mixed component gas according to the test needs. When the gas changes, the applied voltage is changed. U , and repeat steps 1 to 6 to adjust the experimental conditions.

[0034] In one embodiment, a coaxial RF cable with impedance matching at the end transmits the voltage signal to a high-speed data acquisition device.

[0035] In one embodiment, the high-speed data acquisition device includes an oscilloscope.

[0036] In one embodiment, a method for measuring broadband transfer current of high-voltage gas discharge uses a broadband high-voltage electrode system to provide a transfer path for gas local discharge charge. The electrode system is powered by a DC high-voltage power supply to generate a stable high electric field between flat electrodes. A picosecond laser light source is used to pulse the electron excitation target surface on the ground electrode, and the discharge transfer current is converted into a voltage signal through a low-inductance impedance. The signal is transmitted to a high-speed data acquisition device through a coaxial radio frequency cable with end impedance matching to obtain a transfer current time domain waveform. Then, the transfer current time domain waveform is analyzed. When the current waveform is When it is the "charge multiplication type", the distance d between the flat electrodes is increased, and a picosecond laser light source is used to pulse-irradiate the electron excitation target surface on the ground electrode. At this time, the time domain waveform of the transfer current is analyzed. When the current waveform is the "charge loss type", the distance d between the flat electrodes is reduced. The distance d between the flat electrodes is repeatedly adjusted in the above manner until the time domain waveform of the transfer current is the "charge translation type". At this time, the electron excitation target surface area is replaced with a metal short-pointed electrode, and other experimental conditions are kept unchanged. At this time, the time domain waveform of the discharge transfer current is measured, which is the broadband transfer current waveform of local discharge of high-pressure gas.

[0037] In one embodiment, Figures 1 to 3As shown, the broadband high-voltage electrode system is made of brass with parallel circular flat electrodes, the electrode spacing d is adjustable, the surface roughness (Ra) is 0.31μm, the root mean square error (RMSE) of the electrode spacing d is 0.17mm, the diameter of the flat electrode is 14cm, and the minimum radius of curvature at the edge of the inner surface is greater than 0.6cm; a through hole is left at the center of the upper plate electrode, the hole diameter is 3mm, and the radius of curvature of the edge of the small hole is 0.25mm; a through hole is left at the center of the lower plate electrode, the hole diameter is 12mm, and the hole is filled with epoxy resin material; the surface of the central area of ​​the epoxy resin in the hole is plasma sputtered to form a circular laser target surface, the sputtering material is silver, and the target surface diameter is 4mm; the target surface area is connected in series with the low-inductance impedance through a metal wire preset inside the epoxy resin.

[0038] The bandwidth of the broadband high-voltage electrode system is calculated and verified. The local discharge process is regarded as a pulse current source I, and the electrode equivalent capacitance is C g , the spatial geometric capacitance between the high voltage electrode and the test cavity and the ring electrode is C p1 , acts as a coupling capacitor in the partial discharge detection circuit; the stray capacitance between the discharge electrode and the ring electrode is C p2 , which is connected in parallel with the measurement impedance Rm, ignoring the influence of the loop self-inductance and stray inductance, the current measurement loop is as follows Figure 7 The structure shown can be further simplified and equivalent to Figure 8 By solving the above circuit, we can get the time constant and system bandwidth calculation expressions of the partial discharge test circuit, as shown in equation (1) and equation (2) respectively. From the above two equations, we can know that the time constant of the circuit is τ It should be as small as possible and must be less than the actual duration of partial discharge. At this time, the spatial geometric capacitance (coupling capacitance) in the loop should be minimized. C p1 , stray capacitance C p2 and electrode capacitance C g .

[0039] (1) (2) The apparent current I m The actual migration current I The ratio of is used as the sensitivity parameter, and its calculation expression is formula (3). In order to ensure sufficient measurement sensitivity, it is necessary to make the apparent current I m As close as possible to the actual discharge migration current I, that is, a larger coupling capacitor should be used C p1 and smaller electrode capacitance C g Therefore, in order to take into account the requirements of high bandwidth (i.e. low time constant) and high sensitivity in the partial discharge detection circuit, the design principle of each circuit parameter is as follows: coupling capacitor C p1 as large as possible, while the stray capacitance C p2 and electrode capacitance C g As small as possible.

[0040] (3) After multi-parameter joint optimization design, the values ​​of various stray parameters in the closed cavity loop are shown in Table 1. The system loop time constant is calculated by equations (1) and (2): τ =8.77×10 -11 s, and the corresponding loop bandwidth is 1.81 GHz. The simulation model of the high-voltage test cavity and the simulation results of the electric field distribution are shown in Figures 9 and 10 shown.

[0041] Table 1 Loop parameters of the electrode system in the closed chamber The high-voltage electrode system is in a metal-enclosed cavity with a high-voltage bushing, a ventilation valve, a signal terminal and a grounding wire, and ensures that the electrode system and the metal-enclosed cavity have sufficient insulation margin under all experimental voltages; the epoxy resin center metal wire at the center of the lower electrode of the high-voltage electrode system passes through the bottom, the diameter of the metal wire is 2mm, and the tail of the metal wire is connected in series with 6 parallel low-inductance resistors. The resistance of a single low-inductance resistor is 300Ω, and the transmission impedance of the RF cable is 50Ω. The head of the metal wire is connected to the electron excitation target. The actual picture of the above high-voltage enclosed cavity and low-inductance impedance is as follows Figure 5 shown.

[0042] The DC high-voltage power supply is connected to the upper plate electrode of the high-voltage electrode system. The power supply parameters are adjustable within the range of 0-125 kV, and the maximum power of the power supply is 165 kVA.

[0043] The picosecond laser light source uses a DPSS laser with a pulse width of 70ps, a wavelength of 266nm, and a peak power of 85kW. A collimation system is used to irradiate the pulsed laser through the small hole of the upper plate electrode to the electron excitation target range on the surface of the lower plate electrode. The high-speed digital acquisition uses an MSO8204 digital oscilloscope with an analog bandwidth of 2GHz and a sampling rate of 10GS / s. The laser and oscilloscope are externally synchronized and triggered.

[0044] During the test, the gas in the chamber was 0.1MPa SF6 / Air mixed gas, and the distance between the plate electrodes was d =5.5cm, current I a =9.2mA, I s =5.5mA, the current increase rate is . It is judged that there is a large "charge multiplication" process. At this time, the external DC voltage is maintained. U Repeatedly adjust the distance between the plate electrodes under the same conditions d , when d=4.2cm, the charge transfer process is in dynamic equilibrium; after the above test is completed, the metal short tip electrode is replaced, its diameter is 3mm, the minimum curvature radius of the tip profile is 250μm, the exposed part length is 5mm, and the tail is connected to the metal wire in the epoxy resin material. At this time, the self-sustaining broadband transfer current waveform caused by the local electric field distortion of the needle tip in the test gas is as follows Fig.11 shown.

[0045] Although the embodiments of the present invention are described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields, and the above specific embodiments are only illustrative and instructive, rather than restrictive. A person of ordinary skill in the art can also make many forms under the guidance of this specification and without departing from the scope of protection of the claims of the present invention, all of which belong to the protection of the present invention.

Claims

1. A method for measuring high-voltage gas discharge broadband transfer current, characterized in that: The method comprises the following steps: Step 1, establishing a broadband high-voltage electrode system to provide a transfer path for gas partial discharge charges, wherein the high-voltage electrode system is powered by a DC high-voltage power supply to generate a stable high electric field between flat plate electrodes, wherein the flat plate electrodes include an upper plate electrode and a lower plate electrode with adjustable electrode spacing, wherein the lower plate electrode is provided with an electron excitation target surface, and the upper plate electrode is provided with a picosecond pulse laser facing the electron excitation target surface; Step 2, pulse irradiation of the electron excitation target surface on the lower plate electrode by a picosecond pulse laser; Step 3, the electron excitation target surface is connected in series with a low-inductance impedance, and the discharge transfer current is converted into a voltage signal through the low-inductance impedance; Step 4, the high-speed signal acquisition device obtains the time domain waveform of the transfer current based on the voltage signal; Step 5, adjusting the electrode spacing between the plate electrodes based on the transfer current time domain waveform until the transfer current time domain waveform is a charge translation type; Step 6, replace the electron excitation target surface area with a metal short-pointed electrode, and keep other experimental conditions unchanged. At this time, the measured discharge transfer current time domain waveform is a high-pressure gas partial discharge broadband transfer current waveform.

2. A method for measuring high-voltage gas discharge broadband transfer current as claimed in claim 1, characterized in that: Preferably, the flat electrode is composed of parallel circular flat brass electrodes, the surface roughness of the circular flat brass electrodes is not more than 0.5 μm, the root mean square error of the electrode spacing d is not more than 0.5 mm, the diameter of the flat electrode is 10-15 cm, and the minimum radius of curvature at the edge of the inner surface is not less than 0.5 cm; wherein, an upper through hole is left at the center of the upper plate electrode, the diameter of the upper through hole is 3 mm, and the radius of curvature of the edge of the upper through hole is 0.25 mm; a lower through hole is left at the center of the lower plate electrode, and the diameter of the lower through hole is 12 mm.

3. A method for measuring high-voltage gas discharge broadband transfer current as claimed in claim 2, characterized in that: Voltage of the upper electrode U Adjustable within the range of (20~100)×d, the maximum power of the DC high voltage power supply P Not less than 50×d, where the voltage is in kV, the electrode spacing d is in cm, and the maximum power of the DC high voltage power supply is P The unit is kVA.

4. A method for measuring high-voltage gas discharge broadband transfer current as claimed in claim 1, characterized in that: A lower through hole is left at the center of the lower plate electrode, and the lower through hole is filled with epoxy resin material. The surface of the central area of ​​the epoxy resin in the hole is plasma sputtered to form a circular electron excitation target surface, and the electron excitation target surface is connected in series with the low-inductance impedance through a metal wire preset inside the epoxy resin.

5. A method for measuring high-voltage gas discharge broadband transfer current as claimed in claim 4, characterized in that: The sputtering material of plasma sputtering is silver, the diameter of the electron excitation target surface is 4mm, the diameter of the metal wire is 2mm, and the tail of the metal wire is connected in series with k parallel low-inductance resistors. The resistance of a single low-inductance resistor is kZ c Ω,Z c is the transmission impedance of the RF cable.

6. A method for measuring high-voltage gas discharge broadband transfer current as claimed in claim 4, characterized in that: The main body of the metal short-tip electrode is cylindrical with a diameter of 3 mm. The tip profile is approximately a Gaussian profile with a minimum curvature radius of 250 μm. The metal short-tip electrode is embedded in the center of the epoxy resin material, with the tip facing the upper plate electrode. The length of the exposed part of the epoxy resin is 5 mm, and the tail is connected to the metal wire in the epoxy resin.

7. A method for measuring high-voltage gas discharge broadband transfer current as claimed in claim 1, characterized in that: The wavelength of the picosecond pulse laser is 266nm or 343nm, and the peak power of the target surface is between 40kW and 250kW. A collimation system is used to irradiate the pulse laser through the through hole of the upper plate electrode to the electron excitation target surface range on the surface of the lower plate electrode.

8. A method for measuring high-voltage gas discharge broadband transfer current as claimed in claim 1, characterized in that: The picosecond pulse laser and the high-speed signal acquisition device are externally synchronously triggered. The analog signal detection bandwidth of the high-speed signal acquisition device is not less than 2 GHz, and the sampling rate is not less than 10 GS / s.

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