Method and system for diagnosing electron density of return stroke discharge channel

Abstract

The invention discloses a return stroke discharge channel electron density diagnosis method and a return stroke discharge channel electron density diagnosis system, relates to the technical field of high voltage insulation prediction, and solves the technical problems of high calculation complexity and relatively large result error when an Saha equation is used for calculating electron density in the prior art. The method comprises the following steps: performing spectrum observation on a return stroke discharge channel to obtain an original emission spectrum of the return stroke discharge channel; identifying and positioning to an H atom spectral line based on the return stroke discharge channel spectral features; extracting spectral data of a certain frame at a certain height position and fitting an H atom spectral line; calculating the FWHA parameter of the H atom spectral line; and calculating the electron density of the return stroke discharge channel based on a Stark broadening method of an H atom spectral line. According to the method, the electron density of the return stroke discharge channel can be analyzed and calculated based on the atomic emission spectrum without obtaining the temperature in the return stroke discharge channel, a basis can be provided for external insulation design of a power system and a power transmission and transformation project, the accuracy of a calculation result is high, and the calculation process is relatively simple and convenient.

Description

Technical Field

[0001] The invention belongs to the field of high voltage insulation prediction, and in particular relates to a method and system for diagnosing electron density of a return discharge channel. Background Art

[0002] The study of natural lightning return discharge and long air gap discharge breakdown discharge (hereinafter collectively referred to as "return discharge channel") is the basis for the research of external insulation design and lightning protection design of high voltage power transmission and transformation projects. Understanding the temporal and spatial evolution of key physical parameters in the return discharge channel is of great significance for lightning protection of power systems and power transmission and transformation projects. Among them, the diagnosis of electron density in the return discharge channel is crucial for the simulation modeling of natural lightning.

[0003] As a key microscopic physical parameter in the backstroke discharge channel, electron density cannot be measured directly. In the early days, researchers used probe tools to infer the local value of electron density, but it was mainly used in cases with relatively low electron density. Later, laser Thomson scattering and interferometry techniques were widely used to measure electron density, but the measurement accuracy was still low. In the study of plasma discharge electron density diagnosis, most researchers use emission spectroscopy to estimate the electron density in the discharge channel. Since most discharge channels are linear light sources, their emission spectra present a series of continuous and distinguishable spectral lines, and the spectral parameters of each spectral line are easy to obtain.

[0004] At present, there are two methods for calculating the electron density in the return discharge channel using emission spectra: the Saha equation and the Stark broadening method of H atom spectrum lines. The Saha equation needs to satisfy the following two assumptions to calculate the electron density in the discharge channel: (1) the discharge channel satisfies the local thermal equilibrium (LTE) condition; (2) the discharge channel is optically thin. The return discharge channel satisfies the LTE condition. However, since the Saha equation also needs to input the temperature in the discharge channel when calculating the electron density, the use conditions are relatively harsh, and the temperature in the return discharge channel is not easy to obtain. When using the Stark broadening method of H atom spectrum lines to calculate the electron density in the return discharge channel, it is only necessary to obtain the full width of the half area (FWHA) parameter of the H atom spectrum line. The line shape of this type of spectrum line does not strictly depend on the velocity and temperature distribution of the electrons. Therefore, it is not necessary to obtain the temperature of the discharge channel to calculate the electron density, nor is it necessary for the discharge channel to meet the LTE condition. This method is relatively simple and accurate in calculating the electron density in the return discharge channel.

[0005] Spectral observation technology has good application prospects and has been applied in many plasma electron density studies. It has the advantages of real-time, non-contact and multi-element analysis. The method of calculating electron density using the Saha equation has the following shortcomings: 1) It is based on a series of assumptions, such as local thermodynamic equilibrium, Boltzmann distribution, etc. In some cases, such assumptions do not hold in plasma; 2) It involves complex mathematical calculations, especially for a variety of different elements, the calculation complexity is high; 3) In the Saha equation, temperature and electron density are coupled together. When calculating electron density, it is necessary to calculate temperature first, which is complex and the result error is large.

[0006] Therefore, the present invention provides a method and system for diagnosing electron density in a return discharge channel. Summary of the invention

[0007] The present invention aims to solve at least one of the technical problems existing in the prior art; to this end, the present invention proposes a method and system for diagnosing electron density in a return discharge channel, which is used to solve the technical problem that the prior art uses the Saha equation to calculate electron density, which has high calculation complexity and large result errors.

[0008] To achieve the above object, the first aspect of the present invention provides a method for diagnosing electron density in a return discharge channel, comprising the following steps:

[0009] Step S1: obtaining the original emission spectrum of the return discharge channel;

[0010] Step S2: based on the original emission spectrum of the return discharge channel obtained, identify and locate the H atomic spectrum line;

[0011] Step S3: extracting the spectrum data at the height L at time t, and fitting the H atomic spectrum line;

[0012] Step S4: Calculate FWHA parameters based on the fitted H atomic spectral lines;

[0013] Step S5: Calculate the electron density in the return channel based on the Stark broadening method of the H atom spectrum;

[0014] Step S6: Update and calculate the channel electron density at different height positions in different frames, repeat steps S1-S5, calculate the electron density of the return discharge channel at the next moment, until the electron density is no longer updated, and obtain the time and space distribution of the electron density in the return discharge channel.

[0015] Preferably, the step of obtaining the original emission spectrum of the return discharge channel includes:

[0016] The original emission spectrum of the return discharge channel is obtained under standard atmospheric pressure and specified temperature and humidity; wherein the original emission spectrum of the return discharge channel at time t is obtained with a time resolution of more than 1 microsecond.

[0017] Preferably, the identifying and locating the H atom spectral line based on the acquired original emission spectrum of the return discharge channel comprises:

[0018] According to the input original emission spectrum of the return discharge channel, the OI spectrum line with a spectrum line wavelength of 777.4nm is identified;

[0019] According to the spectral characteristics of the relative position between the H atomic spectral line and the OI spectral line, the Hα atomic spectral line with a spectral wavelength of 656.30nm or the Hβ atomic spectral line with a spectral wavelength of 486.10nm is identified and accurately located.

[0020] Preferably, extracting the spectral data at the height L at time t and fitting the H atomic spectral line comprises:

[0021] Based on the identified and located H atomic spectral lines, the vertical channel part with spectral resolution greater than the resolution threshold in the backstroke discharge channel is selected, and the spectral data points with equal number of wavelengths around the central wavelength of the H atomic spectral line are extracted. The H atomic spectral line diagram is fitted using the Lorenz function:

[0022]

[0023] Where A is the area enclosed by the spectral line shape; x is the spectral line wavelength; y is the spectral line intensity; ω is the FWHA parameter; x c is the central wavelength of the spectral line; y0 is the background value of the spectral line intensity.

[0024] Preferably, the calculation of FWHA parameters based on the fitted H atomic spectral lines comprises:

[0025] Based on the fitted H atomic spectrum, the electron density of the return discharge channel can be calculated by obtaining the FWHA parameters of the spectrum; the wavelength value of the area enclosed by the spectrum accounts for 1 / 4 of the total area is Δw1, and the wavelength value of the area enclosed by the spectrum accounts for 3 / 4 of the total area is Δw2. The area of ​​the spectrum enclosed between the two wavelength values ​​accounts for 1 / 2 of the total area. The FWHA parameter is calculated according to the following formula:

[0026] Δw A / 2 =Δw2-Δw1;

[0027]

[0028] Where Δw is the wavelength value; Δw A / 2 is the FWHA parameter of the Hα or Hβ spectral line.

[0029] Preferably, the Stark broadening method based on the H atom spectrum line is used to calculate the electron density in the return channel, including:

[0030] Calculate the electron density of the return discharge channel based on the FWHA parameters of the Hα or Hβ spectral line;

[0031] Calculate the Stark broadening of the Hα atomic spectral line with a spectral line wavelength of 656.30nm:

[0032]

[0033] Calculation of the electron density Nα in the return discharge channel based on the FWHAα parameters of the Hα atomic spectrum e :

[0034]

[0035] Calculate the Stark broadening of the Hβ atomic spectral line with a spectral line wavelength of 486.10nm:

[0036]

[0037] Calculation of the electron density Nβ of the return discharge channel based on the FWHAβ parameters of the Hβ atomic spectrum e :

[0038]

[0039] Preferably, the second aspect of the present invention provides a return discharge channel electron density diagnostic system, comprising an impulse voltage generator, a high voltage electrode, a VPH grating, a high-speed camera, an electro-optical converter, a photoelectric converter, an oscilloscope, a voltage divider and a computer;

[0040] The impulse voltage generator is connected to the high-voltage electrode via a bare copper wire, and the impulse voltage generator generates a standard operating impulse voltage waveform to generate a back-stroke discharge channel under the high-voltage electrode;

[0041] The VPH grating is placed in front of the lens of the high-speed camera, and the two are assembled into a slitless spectrometer;

[0042] The light emitted by the return discharge channel is split after passing through the VPH grating, and is focused on the CMOS plane of the high-speed camera through the lens to form an emission spectrum with time and space resolution;

[0043] The computer is connected to the high-speed camera by a network cable, and is used to receive the emission spectrum with time and space resolution shot by the high-speed camera;

[0044] The impulse voltage generator is connected to the voltage divider via a wire; the voltage divider is connected to the oscilloscope via a coaxial cable;

[0045] The trigger signal generated by the oscilloscope triggers the high-speed camera through the electro-optical converter, the optical fiber and the photoelectric converter, and obtains the emission spectrum of the return discharge channel with time and space resolution.

[0046] Preferably, the trigger signal transmission circuit of the high-speed camera includes:

[0047] The oscilloscope receives the voltage signal of the voltage divider to display and store the waveform; the oscilloscope sets the trigger mode and trigger level, and when the voltage signal of the voltage divider received by the oscilloscope reaches the trigger level, the oscilloscope outputs a trigger signal; the trigger signal is converted into an optical signal by the electro-optical converter, and is converted into an electrical signal by the optical fiber connection photoelectric converter; the high-speed camera receives the trigger signal converted from the photoelectric converter, which is used for the synchronous triggering of the high-speed camera and captures the emission spectrum of the return discharge channel with time and space resolution.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] 1. The electron density calculation method of the present invention has the following advantages: 1) The energy level structure and transition law of the Balmer spectrum of the H atom are clear, and there is no need to consider the complex energy level structure and transition process, and the process of calculating the electron density is relatively simple; 2) This type of spectrum has a very high resolution and signal-to-noise ratio, and a high-precision electron density calculation can be achieved; 3) Within a certain range, the Stark broadening of this type of spectrum is linearly related to the electron density, and the calculation result has a high precision; the present invention fully ensures that the physical process in the return discharge channel is not destroyed, and accurately measures the electron density in the return discharge channel;

[0050] 2. The present invention uses a slitless spectrometer constructed with a high-speed camera and a VPH grating, which not only improves the spectral resolution and spectral dispersion, but also improves the time resolution of spectral recording, and realizes the diagnosis of the spatiotemporal distribution of electron density in the return discharge channel. The electron density calculation result has high accuracy, the calculation process is relatively simple, efficient, and feasible. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0052] Figure 1 It is a schematic diagram of the process of the present invention;

[0053] Figure 2It is a schematic diagram of the electron density diagnosis system of the return discharge channel based on atomic emission spectroscopy of the present invention;

[0054] Figure 3 Schematic diagram of the FWHA parameter calculation of the present invention. DETAILED DESCRIPTION

[0055] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] See also Figure 1 , the first aspect of the present invention provides an electron density diagnostic system for a return discharge channel, including an impulse voltage generator, a high voltage electrode, a VPH grating, a high-speed camera, an electro-optical converter, a photoelectric converter, an oscilloscope, a voltage divider and a computer;

[0057] The impulse voltage generator is connected to the high-voltage electrode through a bare copper wire. The height of the high-voltage electrode from the ground is about 1m. The impulse voltage generator generates a 250 / 2500μs standard operating impulse voltage waveform to generate a backstroke discharge channel under the high-voltage electrode.

[0058] The VPH grating was placed as close as possible to the front of the lens of the high-speed camera to assemble into a simple slitless spectrometer;

[0059] The light emitted by the return discharge channel is split after passing through the VPH grating, and is focused on the CMOS plane of the high-speed camera through the lens to form an emission spectrum with time and space resolution.

[0060] The computer and the high-speed camera are connected by a network cable to receive the emission spectrum with time and space resolution taken by the high-speed camera;

[0061] The impulse voltage generator and the voltage divider are connected via a wire;

[0062] The voltage divider is connected to the oscilloscope via a coaxial cable;

[0063] The trigger signal generated by the oscilloscope triggers the high-speed camera through the electro-optical converter, the optical fiber and the photoelectric converter, and obtains the emission spectrum of the return discharge channel with time and space resolution.

[0064] The following is the trigger signal transmission circuit of the high-speed camera:

[0065] The oscilloscope receives the voltage signal from the voltage divider to display and store the waveform;

[0066] The oscilloscope sets the trigger mode and trigger level, and the trigger voltage is set to 500mV. When the voltage divider voltage signal received by the oscilloscope reaches the trigger level, the oscilloscope outputs a trigger signal;

[0067] The trigger signal is converted into an optical signal through an electro-optical converter, and then converted into an electrical signal through an optical fiber connecting the photoelectric converter;

[0068] The high-speed camera receives the trigger signal converted by the photoelectric converter, which is used for synchronous triggering of the high-speed camera and photographing the emission spectrum of the return discharge channel with time and space resolution.

[0069] Furthermore, the high-speed camera lens has a focal length range of 50-100 mm and an aperture of f / 1.2.

[0070] Furthermore, the high-speed camera is set to have a shooting frequency of 30,0000 frame / s, an exposure time of 3 μs, and a spectral response range of 400 to 1000 nm to obtain an emission spectrum of the return discharge channel with time and space resolution.

[0071] A second aspect of the present invention provides a method for diagnosing electron density in a return stroke discharge channel, wherein the return stroke discharge channel includes a natural lightning return stroke channel and a laboratory long spark discharge channel, and the electron density diagnosis method includes the following steps:

[0072] Step P1: The impulse voltage generator generates a standard operating impulse voltage wave and applies it to the high voltage electrode, and the rod electrode generates a relatively vertical return discharge channel;

[0073] Step P2: The oscilloscope displays, measures and stores the standard operation impulse voltage waveform. The trigger signal generated by the oscilloscope triggers the high-speed camera through the electro-optical converter, optical fiber and photoelectric converter to obtain the return discharge channel emission spectrum with time and space resolution;

[0074] Step P3: The light beam emitted by the return discharge channel is close to a parallel light beam when it propagates to the VPH grating;

[0075] Step P4: After the parallel light is split by the VPH grating, it generates light of different wavelengths with dispersion differences, which is focused on the CMOS plane of the high-speed camera through the high-speed camera lens to form an emission spectrum, thereby obtaining an emission spectrum of the return discharge channel with time and space resolution;

[0076] For example, consider a 1m rod-plate electrode structure as the discharge object, the air pressure is one standard atmospheric pressure, and the discharge medium is natural air. The discharge time under a 1m long air gap usually lasts for tens of microseconds or more, and the air gap is completely broken down when the leader propagates from the rod electrode to the plate electrode. The original emission spectrum of the backstroke discharge channel is obtained by Figure 2The light emitted by the return discharge channel is close to parallel light when it reaches the VPH grating. After the spectroscopic processing of the VPH grating, light of different wavelengths with different dispersions exits the VPH grating. The light of different wavelengths passes through the high-speed camera lens and is focused on the CMOS plane of the high-speed camera, forming the original emission spectrum of the return discharge channel.

[0077] Step P5: The computer program identifies and locates the H atomic spectral lines from the emission spectrum of the return discharge channel with time and space resolution;

[0078] Specifically, in the input original emission spectrum of the return discharge channel, the OI777.4nm spectrum line with the highest spectrum line intensity is first identified, and according to the spectral characteristics of the relative position between the H atomic spectrum line and the OI 777.4nm spectrum line, the Hα656.30nm atomic spectrum line and the Hβ486.10nm atomic spectrum line are identified and accurately located.

[0079] Step P6: extract the spectrum data at the height L at time t, and fit the H atomic spectrum line;

[0080] Specifically, based on the identified and located H atom spectral lines, the vertical channel part with spectral resolution greater than the resolution threshold in the backstroke discharge channel is selected, and the spectral data points with an equal number of wavelengths around the central wavelength of the H atom spectral line are extracted. The H atom spectral line diagram is fitted according to the Lorenz line shape function:

[0081]

[0082] Where A is the area enclosed by the spectral line shape; x is the spectral line wavelength; y is the spectral line intensity; ω is the FWHA parameter; x c is the central wavelength of the spectral line; y0 is the background value of the spectral line intensity.

[0083] See also Figure 3 , step P7: locate the Hα atomic spectrum with a central wavelength of 656.30nm or the Hβ atomic spectrum with a central wavelength of 486.10nm, obtain the FWHA parameters of the spectrum to calculate the electron density of the return discharge channel; the wavelength value of the area enclosed by the spectrum line accounting for 1 / 4 of the total area is Δw1, the wavelength value of the area enclosed by the spectrum line accounting for 3 / 4 of the total area is Δw2, and the area of ​​the spectrum line enclosed between the two wavelength values ​​accounts for 1 / 2 of the total area. The FWHA parameter calculation formula is as follows:

[0084] Δw A / 2 =Δw2-Δw1;

[0085]

[0086] Where Δw is the wavelength value; Δw A / 2is the FWHA parameter of the Hα or Hβ spectral line.

[0087] Step P8: Calculate the electron density of the return discharge channel based on the FWHA parameters of the Hα or Hβ spectral line;

[0088] Calculate the electron density of the return discharge channel based on the FWHA parameters of the Hα or Hβ spectral line;

[0089] Calculate the Stark broadening of the Hα atomic spectral line with a spectral line wavelength of 656.30nm:

[0090]

[0091] Calculation of the electron density Nα in the return discharge channel based on the FWHAα parameters of the Hα atomic spectrum e :

[0092]

[0093] Calculate the Stark broadening of the Hβ atomic spectral line with a spectral line wavelength of 486.10nm:

[0094]

[0095] Calculation of the electron density Nβ of the return discharge channel based on the FWHAβ parameters of the Hβ atomic spectrum e :

[0096]

[0097] Step P9: updating and calculating the channel electron density at different height positions in different frames;

[0098] Input the original emission spectrum of the return discharge channel of the next frame, and bring the FWHA parameters solved in steps P1 to P8 into the calculation formula of P7-P8. Repeat P1-P9 until the electron density is no longer updated, and the time and space distribution of the electron density in the return discharge channel can be obtained.

[0099] Part of the data in the above formula is calculated by removing the dimension and taking its numerical value. The formula is a formula closest to the actual situation obtained by software simulation of a large amount of collected data; the preset parameters and preset thresholds in the formula are set by technical personnel in this field according to actual conditions or obtained through simulation of a large amount of data.

[0100] The above embodiments are only used to illustrate the technical method of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical method of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical method of the present invention.

Claims

1. A method for diagnosing electron density in a return discharge channel, characterized in that: The following steps are involved: Step S1: obtaining the original emission spectrum of the return discharge channel; Step S2: based on the original emission spectrum of the return discharge channel obtained, identify and locate the H atomic spectrum line; Step S3: extracting the spectrum data at the height L at time t, and fitting the H atomic spectrum line; Step S4: Calculate FWHA parameters based on the fitted H atomic spectral lines; Step S5: Calculate the electron density in the return channel based on the Stark broadening method of the H atom spectrum; Step S6: Update and calculate the channel electron density at different height positions in different frames, repeat steps S1-S5, calculate the electron density of the return discharge channel at the next moment, until the electron density is no longer updated, and obtain the time and space distribution of the electron density in the return discharge channel.

2. A method for diagnosing electron density of a return discharge channel according to claim 1, characterized in that: The method of obtaining the original emission spectrum of the return discharge channel comprises: The original emission spectrum of the return discharge channel is obtained under standard atmospheric pressure and specified temperature and humidity; wherein the original emission spectrum of the return discharge channel at time t is obtained with a time resolution of more than 1 microsecond.

3. A method for diagnosing electron density of a return discharge channel according to claim 1, characterized in that: The method of identifying and locating the H atom spectral line based on the original emission spectrum of the return discharge channel obtained includes: According to the input original emission spectrum of the return discharge channel, the OI spectrum line with a spectrum line wavelength of 777.4nm is identified; According to the spectral characteristics of the relative position between the H atomic spectral line and the OI spectral line, the Hα atomic spectral line with a spectral wavelength of 656.30nm or the Hβ atomic spectral line with a spectral wavelength of 486.10nm is identified and accurately located.

4. A method for diagnosing electron density of a return discharge channel according to claim 1, characterized in that: The extracting of the spectrum data at the height L at time t and fitting the H atomic spectrum line includes: Based on the identified and located H atomic spectral lines, the vertical channel part with spectral resolution greater than the resolution threshold in the backstroke discharge channel is selected, and the spectral data points with equal number of wavelengths around the central wavelength of the H atomic spectral line are extracted. The H atomic spectral line diagram is fitted using the Lorenz function: Where A is the area enclosed by the spectral line shape; x is the spectral line wavelength; y is the spectral line intensity; ω is the FWHA parameter; x c is the central wavelength of the spectral line; y0 is the background value of the spectral line intensity.

5. A method for diagnosing electron density of a return discharge channel according to claim 4, characterized in that: The calculation of FWHA parameters based on the fitted H atomic spectral lines includes: Based on the fitted H atomic spectrum, the electron density of the return discharge channel can be calculated by obtaining the FWHA parameters of the spectrum; the wavelength value of the area enclosed by the spectrum accounts for 1 / 4 of the total area is Δw1, and the wavelength value of the area enclosed by the spectrum accounts for 3 / 4 of the total area is Δw2. The area of ​​the spectrum enclosed between the two wavelength values ​​accounts for 1 / 2 of the total area. The FWHA parameter is calculated according to the following formula: Δw A / 2 =Δw2-Δw1; Where Δw is the wavelength value; Δw A / 2 is the FWHA parameter of the Hα or Hβ spectral line.

6. A method for diagnosing electron density of a return discharge channel according to claim 5, characterized in that: The Stark broadening method based on the H atom spectrum is used to calculate the electron density in the return channel, including: Calculate the electron density of the return discharge channel based on the FWHA parameters of the Hα or Hβ spectral line; Calculate the Stark broadening of the Hα atomic spectral line with a spectral line wavelength of 656.30nm: Calculation of the electron density Nα in the return discharge channel based on the FWHAα parameters of the Hα atomic spectrum e : Calculate the Stark broadening of the Hβ atomic spectral line with a spectral line wavelength of 486.10nm: Calculation of the electron density Nβ of the return discharge channel based on the FWHAβ parameters of the Hβ atomic spectrum e :

7. A return discharge channel electron density diagnosis system, based on a return discharge channel electron density diagnosis method according to any one of claims 1 to 6, characterized in that: It includes impulse voltage generator, high voltage electrode, VPH grating, high speed camera, electro-optic converter, photoelectric converter, oscilloscope, voltage divider and computer; The impulse voltage generator is connected to the high-voltage electrode via a bare copper wire, and the impulse voltage generator generates a standard operating impulse voltage waveform to generate a back-stroke discharge channel under the high-voltage electrode; The VPH grating is placed in front of the lens of the high-speed camera, and the two are assembled into a slitless spectrometer; The light emitted by the return discharge channel is split after passing through the VPH grating, and is focused on the CMOS plane of the high-speed camera through the lens to form an emission spectrum with time and space resolution; The computer is connected to the high-speed camera by a network cable, and is used to receive the emission spectrum with time and space resolution shot by the high-speed camera; The impulse voltage generator is connected to the voltage divider via a wire; the voltage divider is connected to the oscilloscope via a coaxial cable; The trigger signal generated by the oscilloscope triggers the high-speed camera through the electro-optical converter, the optical fiber and the photoelectric converter, and obtains the emission spectrum of the return discharge channel with time and space resolution.

8. A method for diagnosing electron density of a return discharge channel according to claim 7, characterized in that: The trigger signal transmission circuit of the high-speed camera comprises: The oscilloscope receives the voltage signal of the voltage divider to display and store the waveform; the oscilloscope sets the trigger mode and trigger level, and when the voltage signal of the voltage divider received by the oscilloscope reaches the trigger level, the oscilloscope outputs a trigger signal; the trigger signal is converted into an optical signal by the electro-optical converter, and is converted into an electrical signal by the optical fiber connection photoelectric converter; the high-speed camera receives the trigger signal converted from the photoelectric converter, which is used for the synchronous triggering of the high-speed camera and captures the emission spectrum of the return discharge channel with time and space resolution.

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