CN103941166B - High-temperature gas breakdown characteristics detecting device and method under a kind of VFTO - Google Patents

Abstract

High-temperature gas breakdown characteristics detecting device and method under a kind of VFTO, this device realizes the detection of gas breakdown process when VFTO, including gas confinement chamber, heating unit, discharge cell, spectrogrph, temperature measurer, gas charge and discharge and recovery unit, voltage source, VFTO generation unit, ammeter and computer；The method is from the breakdown process of the angle detected gas of microcosmic, by the light intensity in spectrometer measurement breakdown process and wavelength, obtains the particle temperature in breakdown process, and obtains the viscosity of particle, electrical conductivity, diffusion coefficient further；And according to the feature of particle encounter under VFTO, the collision term of Boltzmann equation is corrected.

Description

Device and method for detecting breakdown characteristic of high-temperature gas under VFTO

Technical Field

The invention belongs to the field of gas discharge, and particularly relates to a device and a method for detecting breakdown characteristics of high-temperature gas under VFTO.

Background

Considerable research work has been carried out on the breakdown characteristics of gas, liquid and solid dielectrics under conventional conditions such as direct current, power frequency alternating current and the like, and in recent years, the dielectric insulation performance under extreme conditions, the gas discharge laws of different forms and conditions and the like have attracted wide attention at home and abroad. In a super-high voltage GIS (totally-enclosed switchgear), due to high reignition frequency, a VFTO (VeryFastTransientOver-voltages) of dozens of MHZ is generated when an isolating switch is operated, and the switching-off performance of the switch is damaged. Therefore, the method has important significance for researching the gas breakdown process under the VFTO condition, however, the current detection means for the gas breakdown characteristic under the VFTO condition is still incomplete. The plasma state in the gas breakdown process under the condition of VFTO is often in a non-equilibrium state, the collision process among particles needs to be described by a non-Boltzmann distribution function, and because the frequency of VFTO is extremely high, the collision among particles in the breakdown process is different from the collision among particles under power frequency voltage, and the original Boltzmann collision model cannot be applied to the extreme condition.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a device and a method for detecting the breakdown characteristic of high-temperature gas under VFTO.

The technical scheme of the invention is as follows:

a device for detecting breakdown characteristics of high-temperature gas under VFTO comprises:

the device comprises a gas sealing chamber, a heating unit, a discharging unit, a spectrometer, a temperature measuring instrument, a gas charging and discharging and recycling unit, a voltage source, a VFTO generating unit, a current meter and a computer;

the gas sealing chamber is of a sealed cylindrical barrel-shaped structure, adopts heat-insulating transparent materials and is used for containing gas;

the heating unit comprises a resistance wire and a ceramic chip; the resistance wire is arranged at the bottom of the inner cavity of the gas closed chamber; the ceramic plates are laid on the surfaces of the resistance wires;

the discharge unit comprises an anode electrode plate and a cathode electrode plate; the anode electrode plate and the cathode electrode plate are respectively arranged at the middle position of the inner cavity wall of the gas sealing chamber and are oppositely arranged;

the probe of the spectrometer is inserted into the inner cavity of the gas closed chamber and is arranged between the anode electrode plate and the cathode electrode plate, and the output end of the spectrometer is connected with one input end of the computer;

the temperature measuring instrument is arranged at the top of the inner cavity of the gas closed chamber;

the gas charging, discharging and recovering unit is communicated with the inner cavity of the gas sealing chamber through a gas pipe;

two output ends of the voltage source are respectively connected with two wiring ends of the resistance wire;

the VFTO generating unit comprises a pulse trigger group, a pulse generator group and a VFTO synthesizing circuit; the pulse trigger group comprises a plurality of pulse triggers; the pulse generator group comprises a plurality of pulse generators; the input ends of all the pulse triggers in the pulse trigger group are respectively connected with different output ends of the computer; the output end of each pulse trigger in the pulse trigger group is respectively connected with the input end of each pulse generator in the pulse generator group; the output end of each pulse generator in the pulse generator group is respectively connected with each input end of the VFTO synthetic circuit, and the output end of the VFTO synthetic circuit is used as the output end of the VFTO generating unit and is connected with the connecting end of the anode electrode plate and the gas closed chamber through an ammeter; the zero potential end of the VFTO generating unit is connected with the connecting end of the cathode electrode plate and the gas closed chamber;

the resistance wire is used for heating the gas in the gas closed chamber; the ceramic plate is used for isolating metal steam generated when the resistance wire is heated from the gas to be detected;

the distance between the anode electrode plate and the cathode electrode plate of the discharge unit is adjustable;

the spectrometer is used for measuring the intensity of the spectrum generated by the gas plasma and the wavelength of the spectrum and transmitting the measured intensity of the spectrum and the wavelength of the spectrum to the computer;

the voltage source is used for supplying power to the resistance wire to enable the resistance wire to generate heat; the temperature measuring instrument is used for measuring the temperature of the heated gas;

the gas charging, discharging and recovering unit is used for charging and vacuumizing the gas closed chamber;

the computer is used for receiving the intensity of a spectrum and the wavelength of the spectrum generated by the gas plasma sent by the spectrometer, calculating the temperature of various particles in the plasma and the distribution of various particles in the gas breakdown process, respectively calculating the diffusion coefficient, the conductivity and the viscosity coefficient of the particles according to the distribution function of various particles in the gas breakdown process, and is used for obtaining VFTO through simulation, decomposing the obtained VFTO into a plurality of nanosecond-level pulse signals with different periods and respectively sending the nanosecond-level pulse signals to each pulse trigger in the pulse trigger group of the VFTO generation unit;

each pulse trigger in the pulse trigger group is used for respectively controlling the output frequency of each pulse generator in the pulse generator group; each pulse generator in the pulse generator group is used for respectively generating pulse signals with required frequency;

the VFTO synthesis circuit is used for respectively carrying out amplitude adjustment on pulse signals generated by each pulse signal generator in the pulse signal generator group, carrying out superposition processing and phase adjustment processing on each pulse signal after amplitude adjustment and outputting the required VFTO;

the method for detecting the breakdown characteristic of the high-temperature gas under the VFTO by adopting the detection device for the breakdown characteristic of the high-temperature gas under the VFTO comprises the following steps:

step 1: adjusting the distance between the anode electrode plate and the cathode electrode plate to reach a required value;

step 2: the gas charging, discharging and recovering unit is used for vacuumizing the gas closed chamber;

and step 3: the gas charging, discharging and recovering unit charges gas with required pressure into the gas closed chamber;

and 4, step 4: the voltage source supplies power to the resistance wire;

and 5: the temperature measuring instrument measures the temperature of the gas in the gas closed room;

step 6: judging whether the gas temperature in the gas closed chamber reaches the target temperature, if so, executing the step 7, otherwise, executing the step 4;

and 7: turning off the voltage source, and stopping supplying power to the resistance wire;

and 8: the VFTO generating unit loads VFTO on the anode electrode plate and the cathode electrode plate at the same time;

and step 9: the spectrometer measures the intensity and wavelength of the spectrum generated by the gas plasma and transmits the intensity and wavelength to the computer;

step 10: judging whether the gas breaks down under VFTO according to whether the indicated value of the ammeter changes, if so, determining that the gas breaks down under VFTO, and executing the step 11, and if not, determining that the gas does not break down under VFTO, and executing the step 9;

step 11: the gas charging, discharging and recovering unit is used for vacuumizing the gas closed chamber;

step 12: the computer calculates the temperature of various particles in the plasma according to the intensity and wavelength of the received spectrum generated by the gas plasma;

step 13: the computer calculates the distribution of various particles in the gas breakdown process according to the temperature of various particles in the gas plasma to obtain the distribution function of various particles in the gas breakdown process;

the distribution of various particles during gas breakdown is obtained by boltzmann equation (1),

$\frac{\∂f}{\∂t}+v\·\frac{\∂f}{\∂r}+\mathrm{eE}\·\frac{\∂f}{\∂p}={\▿}_p\·s---\left(1\right)$

where s is the particle stream density in momentum space, units/m³；▽_pIs the full differential of s to momentum, p is the momentum of the particle in kg.m/s, and the component of s in the direction of α axis is s_α，s_αObtained by the formula (2), wherein the α axis is an X axis, or the α axis is a Y axis, or the α axis is a Z axis;

$s_{\mathrm{\α}}={\mathrm{\σ}}_t{u}^2\·|v-v^{\′}|\∫\∫\∫(f\frac{{\∂f}^{\′}}{{\∂p}_{\mathrm{\β}}^{\′}}-f^{\′}\frac{\∂f}{{\∂p}_{\mathrm{\β}}})\×({(v-v^{\′})}^2{\mathrm{\δ}}_{\mathrm{\α\β}}-(v_{\mathrm{\α}}-{v_{\mathrm{\α}}}^{\′})(v_{\mathrm{\β}}-{v_{\mathrm{\β}}}^{\′}))d^3{p}^{\′}---\left(2\right)$

wherein σ_tIs a transport section, obtained by formula (3); u is the reduced mass of the particles,m and m 'are the mass, kg, of two colliding particles with momentum p and p'; v and v 'are the particle velocity with momentum p and the particle velocity with momentum p', m/s, respectively; f is the distribution function of particles with momentum p; f 'is the distribution function of particles with momentum p'; p'_βThe component of momentum p' in the direction of β axis, β axis is X axis, or β axis is Y axis, or β axis is Z axis, p_βIs the component of momentum p in the direction of axis β;_αβis a unit tensor; v. of_αThe component of the velocity of the particle with momentum p in the direction of α axis, m/s, v_α'is the component of the particle velocity α axial direction with momentum p', m/s_βThe velocity of the particles being momentum p is βComponent in the axial direction, m/s; v. of_β'is the component of the particle velocity β axial direction with momentum p', m/s;

${\mathrm{\σ}}_t={\mathrm{\σ}}_e+{\mathrm{\σ}}_r=\frac{2\mathrm{\π}}{k^2}\underset{l=0}{\overset{\∞}{\mathrm{\Σ}}}(2l+1)(1-{\left|S_l\right|}^2)---\left(3\right)$

wherein σ_eIs an elastic scattering cross section; sigma_rIs an inelastic scattering cross section; k is the wave number of the incident particle and is determined according to equation (4); l is angular momentum, kg · m²/s；S_lIs a random number modulo less than 1, S_l1 indicates the complete absence of such scattering, S_l0 means that the particle with angular momentum of l is completely absorbed;

wherein,is Planck constant; e is the energy of the scattering particles, joules; m is₁The mass of the lighter particles in the two collision particles is kg;

step 14: and respectively calculating the diffusion coefficient, the conductivity and the viscosity coefficient of the particles by the computer according to the distribution functions of various particles in the gas breakdown process.

Has the advantages that: compared with the prior art, the device and the method for detecting the breakdown characteristic of the high-temperature gas under VFTO have the following advantages:

1) the device is different from the previous research on the breakdown process that only macroscopic parameters such as breakdown voltage and the like are measured, the breakdown process of gas is detected from a microscopic angle, the light intensity and the wavelength in the breakdown process are measured through a spectrometer, the particle temperature in the breakdown process is obtained, and the particle temperature is applied to the research method provided by the invention to obtain the viscosity coefficient, the conductivity and the diffusion coefficient of the particles.

2) According to the GIS, VFTO is generated, and the breaking performance of the circuit breaker is damaged. At present, almost no research is carried out on the gas breakdown process under the extreme condition of VFTO, and the detection of the gas breakdown process under the condition of VFTO can be realized by the invention.

3) Complicated collision exists among particles in the gas breakdown process, the distribution of the particles needs to be described by non-Boltzmann distribution, and due to the fact that the frequency of VFTO is extremely high, the collision of the particles in the breakdown process is different from that under the power frequency condition, and therefore the collision term of the Boltzmann needs to be corrected when the particle density distribution in the breakdown process is solved under the VFTO condition. According to the characteristic of particle collision under VFTO, the invention corrects the collision item of the Boltzmann equation.

Drawings

Fig. 1 is a schematic connection diagram of a high-temperature gas breakdown characteristic detection apparatus under VFTO according to an embodiment of the present invention;

FIG. 2 is a schematic view of the construction of a flange for a gas enclosure according to one embodiment of the present invention;

FIG. 3 is a schematic diagram of the connection relationship between the gas charging/discharging and recycling unit according to an embodiment of the present invention: (a) is a structural schematic diagram of a vacuum-pumping part; (b) is a structural schematic diagram of an inflatable part;

FIG. 4 is a schematic circuit diagram of a VFTO generating unit according to an embodiment of the present invention;

fig. 5 is a flowchart of a method for detecting breakdown characteristics of high-temperature gas under VFTO according to an embodiment of the present invention.

Detailed Description

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in fig. 1, the apparatus for detecting a high-temperature gas breakdown characteristic under VFTO according to the present embodiment includes: the device comprises a gas sealing chamber 7, a heating unit, a discharging unit, a spectrometer 5, a temperature measuring instrument 3, a gas charging, discharging and recycling unit 1, a voltage source 12, a VFTO generating unit 11, an ammeter 16 and a computer 15;

the gas sealing chamber 7 is of a closed cylindrical barrel-shaped structure, is used for containing gas, is made of heat-insulating glass materials, and has the wall thickness of about 20mm, the diameter of a cylindrical barrel-shaped inner cavity of the gas sealing chamber 7 is about 170mm, and the height of about 400 mm; the top of the gas sealing chamber 7 is connected with the upper flange 6, and the bottom of the gas sealing chamber 7 is connected with the lower flange 10; the upper flange 6 and the lower flange 10 have the same structure, as shown in fig. 2, a circle groove with a width of 20mm is respectively formed at a position 85mm away from the center of the upper flange 6 and a position 85mm away from the center of the lower flange 10, and a rubber sealing gasket 17 is respectively arranged in the two circle grooves. The upper flange 6 and the lower flange 10 are connected to the gas-tight chamber in an interposed manner and are fixed all around by means of bolts 18. For high temperature test, the rubber sealing ring 17 is made of perfluoro rubber and has strong high temperature resistance.

The heating unit comprises a resistance wire 13 and a ceramic plate 9; the resistance wire 13 is used for heating the gas in the gas closed chamber, and is twisted into strands to be flatly laid and installed on the surface position of the lower flange 10 at the bottom of the cavity in the gas closed chamber in order to increase the heating area and enable the gas to be uniformly heated; the resistance wire 13 is made of iron chromium aluminum OCr27Al7MO2, and the highest temperature of the heatable gas is 1400 ℃; the ceramic material on the surface of the resistance wire 13 is an alumina ceramic plate with the model of TO-247. The method has the advantages that interference of metal steam generated when the resistance wire 13 is heated on plasma measurement in a breakdown process is avoided, and a layer of ceramic plate 9 with high heat conductivity coefficient is paved on the surface of the resistance wire 13 and used for isolating the metal steam generated when the resistance wire 13 is heated from a gas to be measured; since the ceramic is less ductile, the ceramic plate 9 has a diameter 4mm smaller than the inner diameter of the gas-tight chamber 7 for easy installation, whereas 4mm is a small amount with respect to the inner diameter of the gas-tight chamber 7, and the resistance wire is arranged below the ceramic plate, so that it does not affect the measurement of the plasma.

The discharge unit comprises an anode electrode plate 14 and a cathode electrode plate 8; the anode electrode plate 14 and the cathode electrode plate 8 are respectively arranged at the middle position of the inner cavity wall of the gas closed chamber 7, the anode electrode plate 14 and the cathode electrode plate 8 are oppositely arranged, and the distance between the anode electrode plate 14 and the cathode electrode plate 8 is adjustable; the anode electrode plate 14 and the cathode electrode plate 8 are both disc-shaped flat plate electrodes, are made of copper and have the diameter of 20mm,

the probe 4 of the spectrometer 5 is inserted into the inner cavity of the gas-enclosed chamber 7, is arranged between the anode electrode plate 14 and the cathode electrode plate 8 and is positioned at a position 5mm above the anode electrode plate 14 and above the cathode electrode plate 8, and the part of the probe 4 arranged in the inner cavity of the gas-enclosed chamber 7 is provided with a convex lens, so that the measurement range of the probe 4 can be enlarged. The spectrum intensity and the spectrum wavelength of the gas plasma under the condition of VFTO when the gas is broken down are obtained by measuring an emission spectrum generated by the gas plasma through the spectrometer 5, and the temperature of each particle in the gas plasma is obtained by utilizing a light intensity ratio method. The spectrometer 5 in the embodiment adopts an AvaSpec-ULS2048-x-USB2 dual-channel spectrometer, the measurable wavelength range is 200-1100nm, the A/D conversion adopts 16-bit 1MHZ, the lowest response time is 0.1ms, the detector adopts a CCD linear array, and the pixels are 2 x 3648.

The temperature measuring instrument 3 is arranged at the top of the inner cavity of the gas sealing chamber 7 and is used for measuring the temperature of the heated gas; the thermometer 3 in the embodiment adopts a fixed infrared thermometer with the model of SCIT-2MK2A, the temperature measuring range of 600-2000 ℃, and the aiming mode is optical visual; it is fixed on the upper flange 6 through bolts. Because the infrared thermometer 3 can only measure the temperature of one point, which may cause great errors in the measurement result, the invention adopts multi-angle measurement, fixes the infrared thermometer on the bearing by bolts, can measure the temperature of multiple directions, measures once every 15 degrees, and averages the measured value as the gas temperature in the cavity.

The gas charging, discharging and recovering unit 1 is communicated with the inner cavity of the gas closed chamber 7 through a gas pipe 2 and is used for charging and discharging gas, recovering the gas and vacuumizing the gas closed chamber; in order to prevent gas leakage during inflation and vacuum pumping, in the embodiment, the gas inflation and recovery unit 1 is communicated with the inner cavity of the gas closed chamber by connecting a threaded stainless steel gas pipe 2 to the upper flange 6, and is used for inflating gas with certain pressure into the gas closed chamber during experiments; after the experiment is finished, the gas in the gas closed chamber is vacuumized to prevent the pollution of harmful gas.

In order to prevent gas leakage during inflation and vacuum pumping, the gas inflation and deflation and recovery unit 1 in the embodiment is connected with a gas sealing chamber 7 through a gas pipe 2, the surface of the gas pipe 2 is provided with threads, and the gas pipe is tightly connected with a stainless steel pipe connected with an upper flange 6 of the gas sealing chamber 7; during the experiment, gas with certain air pressure is filled into the gas sealing chamber 7, and after the experiment is finished, the gas in the gas sealing chamber 7 is vacuumized to prevent the pollution of harmful gas; the gas charging, discharging and recovering unit 1 comprises a vacuumizing device and an inflating device; the vacuumizing part comprises a gas recovery tank 25, a vacuum gauge 19, a vacuum pump 24, a gas pressure gauge 22, a valve 20, a valve 21 and a valve 23, as shown in fig. 3(a), when the gas sealing chamber 7 is vacuumized, the valve 20, the valve 21 and the valve 23 are opened, the gas is pumped out through the vacuum pump 24, and the maximum vacuum degree is 10 Pa; the gas charging part comprises a gas storage tank 29, a filter 28, a compressor 27, a gas pressure gauge 26 and a valve 30, and as shown in fig. 3(b), when the gas closing chamber 7 is charged, the gas in the gas storage tank 26 is charged into the gas closing chamber 7 through the filter 28 and the compressor 27, and the highest pressure is 3.8 Mpa;

the two output ends of the voltage source 12 are respectively connected with the two terminals of the resistance wire 13 and used for supplying power to the resistance wire 13, so that the resistance wire 13 generates heat, and gas can reach higher temperature quickly before discharging; in the present embodiment, the voltage source 12 is a GQ-AD type 3000W adjustable switching power supply, with a maximum voltage of 1500V and a maximum current of 2000A.

The VFTO generating unit, as shown in fig. 4, includes a pulse trigger group 31, a pulse generator group 32, and a VFTO synthesizing circuit 33; in this embodiment, n pulse triggers in the pulse trigger group 31 all adopt pulse triggers of model 501003CDB (CD3), and n pulse generators in the pulse generator group 32 all adopt pulse generators of all-solid-state pulse power source of model SPG 200;

the pulse trigger group 31 comprises n pulse triggers for controlling the output frequency of the pulse generator group 32; the pulse generator group 32 includes n pulse generators for generating pulse signals of a certain frequency; the input ends of the pulse triggers in the pulse trigger group 31 are respectively connected with different output ends of the computer 15; the output end of each pulse trigger in the pulse trigger group 31 is respectively connected with the input end of each pulse generator in the pulse generator group 32; the output end of each pulse generator in the pulse generator group 32 is respectively connected with each input end of the VFTO synthesis circuit 33, and the output end of the VFTO synthesis circuit 33 is used as the output end of the VFTO generation unit 11 and is connected with the connecting end of the anode electrode plate 14 and the gas sealing chamber 7 through the ammeter 16; the zero potential end of the VFTO generating unit 11 is connected with the connecting end of the cathode electrode plate 8 and the gas closed chamber 7;

resistors R1, R2, … and Rn are respectively connected in series between each input end of the VFTO combining circuit 33 and the negative input end of the first-stage operational amplifier 34, as shown in fig. 4, a resistor Rn +1 is connected in parallel between the negative input end of the first-stage operational amplifier 34 and the output end thereof, the positive input end of the first-stage operational amplifier 34 is grounded through a resistor Rn +2, the output end of the first-stage operational amplifier 34 is connected with the negative input end of the second-stage operational amplifier 35 through a resistor Rn +3, a resistor Rn +4 is connected in parallel between the negative input end of the second-stage operational amplifier 35 and the output end thereof, and the positive input end of the second-stage operational amplifier 35 is grounded through a resistor Rn + 5.

In the embodiment, the computer 15 simulates and calculates the VFTO generated during the operation of the isolation switch in a certain GIS, and decomposes the VFTO into n nanosecond pulse signals with different amplitudes and different frequencies; the computer 15 sets the frequency value of each decomposed pulse signal in each pulse trigger in the pulse trigger set 31, each pulse trigger in the pulse trigger set 31 triggers each pulse generator in the pulse generator set 32 to generate a pulse signal according to the set frequency value of the pulse signal, each pulse generator in the pulse generator set 32 transmits the pulse signal to each input end of the VFTO synthesizing circuit 33, the resistors R1, R2, … and Rn in the VFTO synthesizing circuit 33 respectively adjust the amplitude of each received pulse signal according to the amplitude of each pulse signal decomposed by the computer 15, the n pulse signals adjusted by the resistors R1, R2, … and Rn are superposed by the first-stage operational amplifier 34 and the phase of the n pulse signals adjusted by the second-stage operational amplifier 35 to obtain the required VFTO at the output end out end of the VFTO synthesizing circuit 33, i.e. the same or close to VFTO as calculated by the computer 15 simulation.

The nanosecond-level pulse signals generated by the pulse generators in the pulse generator group 32 have frequencies f1, f2, … and fn, and voltages u₁、u₂、…、u_nU is obtained after superposition of a first-stage operational amplifier 34_n+1，

$u_{n+1}=-\frac{R_{n+1}}{R_1}{u}_1-\frac{R_{n+1}}{R_2}{u}_2-...-\frac{R_{n+1}}{R_n}{u}_n---\left(5\right)$

u_n+1U is obtained after the phase is adjusted by the second-stage operational amplifier 35_n+2I.e. VFTO

$u_{n+2}=-\frac{R_{n+4}}{R_{n+3}}{u}_{n+1}=\mathrm{VFTO}---\left(6\right)$

Wherein R is_n+3、R_n+4Is resistance, in units of Ω, and R_n+4＝R_n+3；

The computer 15 is configured to receive the intensity of the spectrum and the wavelength of the spectrum generated by the gas plasma sent by the spectrometer 5, calculate the temperature of various particles in the gas plasma and the distribution of various particles in the gas breakdown process, calculate the diffusion coefficient of the particles, the conductivity of the particles, and the viscosity coefficient of the particles according to the distribution function of various particles in the gas breakdown process, and simulate and calculate the VFTO generated during the isolation switch operation in a certain GIS, and decompose the obtained VFTO into a plurality of nanosecond-level pulse signals with the same amplitude and different periods and send the nanosecond-level pulse signals to each pulse trigger in the pulse trigger group 31 of the VFTO generation unit.

The method for detecting the breakdown characteristic of the high-temperature gas under the VFTO by adopting the detection device for the breakdown characteristic of the high-temperature gas under the VFTO in the embodiment comprises the following steps:

step 1: adjusting the distance between the anode electrode plate 14 and the cathode electrode plate 8 to 5 mm;

step 2: the gas charging, discharging and recovering unit 1 is used for vacuumizing the gas sealing chamber 7;

and step 3: the gas charging and discharging and recovering unit 1 charges SF6 gas of 0.1MPa into the gas sealing chamber 7;

and 4, step 4: the voltage source 12 supplies power to the resistance wire 13 to heat the resistance wire;

and 5: the infrared thermometer 3 measures the temperature of SF6 in the gas enclosure 7 from a plurality of angles, and averages the measured values as the gas temperature in the enclosure 7;

step 6: judging whether the gas temperature reaches 1000 degrees of the target temperature, if so, executing a step 7, and if not, executing a step 4;

and 7: the voltage source 12 is turned off, and the power supply to the resistance wire 13 is stopped;

and 8: the VFTO generating unit 11 loads VFTO on the anode electrode plate 14 and the cathode electrode plate 8 at the same time;

and step 9: the spectrometer 5 measures the spectral intensity and wavelength of the plasma in the SF6 gas and transmits the measured spectral intensity and wavelength to the computer 15;

step 10: judging whether the SF6 gas breaks down under VFTO according to whether the indicated value of the ammeter 16 changes, if the indicated value of the ammeter 16 changes, considering that the gas breaks down, and if the indicated value of the ammeter 16 does not change, considering that the gas does not break down;

step 11: the gas charging, discharging and recovering unit 1 vacuumizes the residual SF6 gas in the gas sealing chamber 7;

step 12: the computer calculates the temperature of various particles in the plasma according to the received spectral intensity and wavelength generated by the SF6 gas plasma;

step 13: the computer 15 calculates the distribution of various particles in the gas breakdown process according to the temperature of various particles in the gas plasma to obtain the distribution function of various particles in the gas breakdown process;

during gas breakdown under VFTO, the momentum change of the particles during collision is small, and the process described by the collision integral can be treated as diffusion in momentum space, and the collision term can be written as:

$c\left(f\right)=-{\▿}_p\·s=-\frac{{\∂s}_{\mathrm{\α}}}{{\∂p}_{\mathrm{\α}}}---\left(7\right)$

where s is the particle stream density in momentum space, units/m³Representing the number of particles per unit volume element in momentum space ▽_pIs the full differential of s to momentum; s_αIs the component of s in the direction of α axis, α axis is X axis, or α axis is Y axis, or α axis is Z axis, p is the momentum of the particles in kg.m/s, p is_αIs the component of momentum p in the direction of α axis, and for a particle with momentum p and a particle with momentum p' in d³The number of collisions occurring per unit time between particles within p' is

w(p+q/2,p′-q/2；q)·f(p)·f′(p′)d³qd³p' (8) wherein q is a momentum transfer value; p' is the momentum of the particles in kg · m/s; w is a w function expressed by momentum p and momentum p' of colliding two particles and a momentum transfer value q;

according to a careful balancing condition, the exchange of the starting particles and the final particles of the function w is symmetrical

w(p+q/2,p′-q/2；q)＝w(p+q/2,p′-q/2；-q)(9)

Considering the unit area of a certain point P in the momentum space perpendicular to the α axis, the particle flow density s is defined_αIs the number of particles per unit time that pass through the area from left to right more than the number of particles that pass through the area from right to left if a particle receives a α component of momentum in a collision equal to q_αThe result of this collision is that for particles passing through the area from left to right, the component value of them before the collision lies from p_α-q_αTo P_αThus, the number of particles passing through the area from left to right is

$\mathrm{\Σ}\underset{q_{\mathrm{\α}}>0}{\∫}{d}^{3}q\∫d^3{p}^{\′}\underset{p_{\mathrm{\α}}-q_{\mathrm{\α}}}{\overset{p_{\mathrm{\α}}}{\∫}}w(p+q/2,p^{\′}-q/2;q)f\left(p\right)f^{\′}\left(p^{\′}\right){\mathrm{dp}}_{\mathrm{\α}}---\left(10\right)$

Wherein f is a distribution function of particles with momentum p; f 'is the distribution function of particles with momentum p';

the number of particles passing through the area from left to right is

$\mathrm{\Σ}\underset{q_{\mathrm{\α}}>0}{\∫}{d}^{3}q\∫d^3{p}^{\′}\underset{p_{\mathrm{\α}}-q_{\mathrm{\α}}}{\overset{p_{\mathrm{\α}}}{\∫}}w(p+q/2,p^{\′}-q/2;-q)f(p+q)f^{\′}(p^{\′}-q){\mathrm{dp}}_{\mathrm{\α}}---\left(11\right)$

As can be seen from equation (8), w is the same in both integrals, and the difference between these integrals includes the difference in the expression of the integral

f(p)f′(p′)-f(p+q)f′(p′-q)

Because the momentum transfer q is very small, the difference can be expanded into a power series of q to finally obtain

$s_{\mathrm{\α}}=\mathrm{\Σ}\underset{q_{\mathrm{\α}}>0}{\∫}{d}^{3}q\∫d^3{p}^{\′}\underset{p_{\mathrm{\α}}-q_{\mathrm{\α}}}{\overset{p_{\mathrm{\α}}}{\∫}}w(p,p^{\′};q)[f\left(p\right)\frac{\∂f^{\′}\left(p^{\′}\right)}{{\∂p}_{\mathrm{\β}}^{\′}}-f^{\′}\left(p^{\′}\right)\frac{\∂f\left(p\right)}{{\∂p}_{\mathrm{\β}}}]q_{\mathrm{\β}}{q}_{\mathrm{\α}}{d}^3{p}^{\′}---\left(12\right)$

Wherein, p'_βThe component of momentum p' in the direction of β axis, β axis is X axis, or β axis is Y axis, or β axis is Z axis, p_βIs the component of momentum p in the direction of axis β;

introducing a collision cross-section instead of the function w

wd³q＝|v-v′|dσ(13)

The momentum flux density of each type of particle in the momentum space has the following form

$s_{\mathrm{\α}}=\mathrm{\Σ}\∫[f\left(p\right)\frac{\∂f^{\′}\left(p^{\′}\right)}{{\∂p}_{\mathrm{\β}}^{\′}}-f^{\′}\left(p^{\′}\right)\frac{\∂f\left(p\right)}{{\∂p}_{\mathrm{\β}}}]B_{\mathrm{\α\β}}{d}^3{p}^{\′}---\left(14\right)$

$B_{\mathrm{\α\β}}=\frac{1}{2}\∫q_{\mathrm{\α}}{q}_{\mathrm{\β}}|v-v^{\′}|\mathrm{d\σ}---\left(15\right)$

Wherein, B_αβIs the amount of particle collisions and is a tensor; q. q.s_αIs α momentum transfer value in axial direction q_ββ, v and v 'are the particle velocity with momentum p and the particle velocity with momentum p', m/s, respectively, and B is the small angle deviation_αβ(v_β-v_β') is 0, so

$B_{\mathrm{\α\β}}=\frac{1}{2}B[{\mathrm{\δ}}_{\mathrm{\α\β}}-\frac{(v_{\mathrm{\α}}-v_{\mathrm{\α}}^{\′})(v_{\mathrm{\β}}-v_{\mathrm{\β}}^{\′})}{{(v-v^{\′})}^2}]---\left(16\right)$

B＝B_αα＝u²|v-v′|³σ_t

Wherein, B_ααIs B_αβA scalar form of (a);

the distribution of various particles during gas breakdown is obtained by boltzmann equation (1),

$\frac{\∂f}{\∂t}+v\·\frac{\∂f}{\∂r}+\mathrm{eE}\·\frac{\∂f}{\∂p}={\▿}_p\·s---\left(1\right)$

where s is the particle stream density in momentum space, units/m³；▽_pIs the full differential of s to momentum, p is the momentum of the particle in kg.m/s, and the component of s in the direction of α axis is s_α，s_αObtained by the formula (2), wherein the α axis is an X axis, or the α axis is a Y axis, or the α axis is a Z axis;

$s_{\mathrm{\α}}={\mathrm{\σ}}_t{u}^2\·|v-v^{\′}|\∫\∫\∫(f\frac{{\∂f}^{\′}}{{\∂p}_{\mathrm{\β}}^{\′}}-f^{\′}\frac{\∂f}{{\∂p}_{\mathrm{\β}}})\×({(v-v^{\′})}^2{\mathrm{\δ}}_{\mathrm{\α\β}}-(v_{\mathrm{\α}}-{v_{\mathrm{\α}}}^{\′})(v_{\mathrm{\β}}-{v_{\mathrm{\β}}}^{\′}))d^3{p}^{\′}---\left(2\right)$

wherein σ_tIs a transport section, obtained by formula (3); u is the reduced mass of the particles,m and m 'are the mass, kg, of two colliding particles with momentum p and p'; v and v 'are the particle velocity with momentum p and the particle velocity with momentum p', m/s, respectively; f is the distribution function of particles with momentum p; f 'is the distribution function of particles with momentum p'; p'_βThe component of momentum p' in the direction of β axis, β axis is X axis, or β axis is Y axis, or β axis is Z axis, p_βIs the component of momentum p in the direction of axis β;_αβis a unit tensor; v. of_αThe component of the velocity of the particle with momentum p in the direction of α axis, m/s, v_α'is the component of the particle velocity α axial direction with momentum p', m/s_βThe component of the velocity of the particle with momentum p in the direction of β axis, m/s, v_β'is the component of the particle velocity β axial direction with momentum p', m/s;

${\mathrm{\σ}}_t={\mathrm{\σ}}_e+{\mathrm{\σ}}_r=\frac{2\mathrm{\π}}{k^2}\underset{l=0}{\overset{\∞}{\mathrm{\Σ}}}(2l+1)(1-{\left|S_l\right|}^2)---\left(3\right)$

wherein σ_eIs an elastic scattering cross section; sigma_rIs an inelastic scattering cross section; k is the wave number of the incident particle and is determined according to equation (4); l is angular momentum, kg · m²/s；S_lIs a random number modulo less than 1, S_l1 indicates the complete absence of such scattering, S_l0 means that the particle with angular momentum of l is completely absorbed;

wherein,is Planck constant; e is the energy of the scattering particles, joules; m is₁The mass of the lighter particles in the two collision particles is kg;

the specific operation mode for solving the boltzmann equation of the formula (1) is as follows: dividing the calculation area into small blocks with macroscopic size (which can be replaced by one point) and microscopic size (which contains enough particles), wherein the plasmas in each small block are balanced and can be represented by the same distribution function, and the small blocks are linearly unbalanced, and setting

f＝f⁰(1+ h) (17) wherein f⁰Is a local boltzmann distribution; h is a small variation;

bringing formula (17) into formula (1)

$[\frac{\∂}{\∂t}+v\·\frac{\∂}{\∂r}+\mathrm{eE}\·\frac{\∂}{\∂p}](f^0+f^{0}h)=f^0{\▿}_p\·s\·h---\left(18\right)$

For small changes in momentum

$f^0=n\left(r\right){\left[2\mathrm{\π}{k}_{B}t(r,t)\right]}^{-\frac{3}{2}}\exp [-\frac{m{|v-u\left(r\right)|}^2}{{2\mathrm{mk}}_{B}T(r,t)}]---\left(19\right)$

Wherein u (r) ═ c<v>The average velocity of the local particles is given in m/s; k is a radical of_BIs the Planck constant; t (r, T) is the local temperature, in K, which is related to the spatial position r of the particles and the time T, the values of which can be obtained by the detection means of the invention; the distribution function of each particle is obtained by solving equation (18).

Step 14: and respectively calculating the diffusion coefficient, the conductivity and the viscosity coefficient of the particles by the computer according to the distribution functions of various particles in the gas breakdown process.

The diffusion coefficient D, the conductivity σ, and the viscosity η are obtained from the expressions (20), (21), and (22)

$D=-\frac{1}{n}{\&Integral;\&Integral;\&Integral;d}^3{\mathrm{vfv}}_x\frac{1}{{\&dtri;}_p\&CenterDot;s}{v}_x---\left(20\right)$

$\mathrm{\&sigma;}=-\frac{e^2}{{2m}_2{k}_{B}T(r,t)}{\&Integral;\&Integral;\&Integral;d}^3{\mathrm{vfv}}_x\frac{1}{{\&dtri;}_p\&CenterDot;s}{v}_x---\left(21\right)$

$\mathrm{\&eta;}=-\frac{m_2}{k_{B}T(r,t)}{\&Integral;\&Integral;\&Integral;d}^3{\mathrm{vfv}}_x{v}_y\frac{1}{{\&dtri;}_p\&CenterDot;s^T}{v}_x{v}_y---\left(22\right)$

Wherein n is the particle number density, number/m³；v_xIs the velocity component of the particle in the X-axis direction, m/s; v. of_yIs the velocity component of the particle in the Y-axis direction, m/s; e is the electron charge, coulomb; m is₂The weight of each particle is Kg.

The distribution of each particle in the SF6 gas obtained in step 13 is expressed by the formula (20), the formula (21) and the formula (22) to obtain the diffusion coefficient D, the conductivity σ and the viscosity η.

Claims (10)

1. The utility model provides a high temperature gas breakdown characteristic detection device under VFTO which characterized in that: the method comprises the following steps:

the device comprises a gas sealing chamber, a heating unit, a discharging unit, a spectrometer, a temperature measuring instrument, a gas charging and discharging and recycling unit, a voltage source, a VFTO generating unit, a current meter and a computer;

the gas sealing chamber is of a sealed cylindrical barrel-shaped structure, adopts heat-insulating transparent materials and is used for containing gas;

the heating unit comprises a resistance wire and a ceramic chip; the resistance wire is arranged at the bottom of the inner cavity of the gas closed chamber; the ceramic plates are laid on the surfaces of the resistance wires;

the discharge unit comprises an anode electrode plate and a cathode electrode plate; the anode electrode plate and the cathode electrode plate are respectively arranged at the middle position of the inner cavity wall of the gas sealing chamber and are oppositely arranged;

the probe of the spectrometer is inserted into the inner cavity of the gas closed chamber and is arranged between the anode electrode plate and the cathode electrode plate, and the output end of the spectrometer is connected with one input end of the computer;

the temperature measuring instrument is arranged at the top of the inner cavity of the gas closed chamber;

the gas charging, discharging and recovering unit is communicated with the inner cavity of the gas sealing chamber through a gas pipe;

two output ends of the voltage source are respectively connected with two wiring ends of the resistance wire;

the VFTO generating unit comprises a pulse trigger group, a pulse generator group and a VFTO synthesizing circuit; the pulse trigger group comprises a plurality of pulse triggers; the pulse generator group comprises a plurality of pulse generators; the input ends of all the pulse triggers in the pulse trigger group are respectively connected with different output ends of the computer; the output end of each pulse trigger in the pulse trigger group is respectively connected with the input end of each pulse generator in the pulse generator group; the output end of each pulse generator in the pulse generator group is respectively connected with each input end of the VFTO synthetic circuit, and the output end of the VFTO synthetic circuit is used as the output end of the VFTO generating unit and is connected with the connecting end of the anode electrode plate and the gas closed chamber through an ammeter; and the zero potential end of the VFTO generating unit is connected with the connecting end of the cathode electrode plate and the gas closed chamber.

2. The apparatus of claim 1 for detecting high temperature gas breakdown characteristics at VFTO, wherein: the resistance wire is used for heating the gas in the gas closed chamber; the ceramic plate is used for isolating metal steam generated when the resistance wire is heated from the gas to be detected.

3. The apparatus of claim 1 for detecting high temperature gas breakdown characteristics at VFTO, wherein: the distance between the anode electrode plate and the cathode electrode plate of the discharge unit is adjustable.

4. The apparatus of claim 1 for detecting high temperature gas breakdown characteristics at VFTO, wherein: the spectrometer is used for measuring the intensity of the spectrum generated by the gas plasma and the wavelength of the spectrum and transmitting the measured intensity of the spectrum and the wavelength of the spectrum to the computer.

5. The apparatus of claim 1 for detecting high temperature gas breakdown characteristics at VFTO, wherein: the voltage source is used for supplying power to the resistance wire to enable the resistance wire to generate heat; the temperature measuring instrument is used for measuring the temperature of the heated gas.

6. The apparatus of claim 1 for detecting high temperature gas breakdown characteristics at VFTO, wherein: the gas charging, discharging and recovering unit is used for charging and vacuumizing the gas closed chamber.

7. The apparatus of claim 1 for detecting high temperature gas breakdown characteristics at VFTO, wherein:

the computer is used for receiving the intensity of a spectrum and the wavelength of the spectrum generated by the gas plasma sent by the spectrometer, calculating the temperature of various particles in the plasma and the distribution of various particles in the gas breakdown process, respectively calculating the diffusion coefficient, the conductivity and the viscosity coefficient of the particles according to the distribution function of various particles in the gas breakdown process, and is used for obtaining VFTO through simulation, decomposing the obtained VFTO into a plurality of nanosecond-level pulse signals with different periods and respectively sending the nanosecond-level pulse signals to each pulse trigger in the pulse trigger group of the VFTO generation unit.

8. The apparatus of claim 1 for detecting high temperature gas breakdown characteristics at VFTO, wherein:

each pulse trigger in the pulse trigger group is used for respectively controlling the output frequency of each pulse generator in the pulse generator group; each pulse generator in the pulse generator group is used for respectively generating a pulse signal with a required frequency.

9. The apparatus of claim 1 for detecting high temperature gas breakdown characteristics at VFTO, wherein:

the VFTO synthesis circuit is used for respectively generating pulses for each pulse signal generator in the pulse signal generator group

And carrying out amplitude adjustment on the signals, and outputting the required VFTO after carrying out superposition processing and phase adjustment processing on each pulse signal after amplitude adjustment.

10. The method for detecting the breakdown characteristic of the high-temperature gas at VFTO by using the device for detecting the breakdown characteristic of the high-temperature gas at VFTO according to claim 1, wherein: the method comprises the following steps:

step 1: adjusting the distance between the anode electrode plate and the cathode electrode plate to reach a required value;

step 2: the gas charging, discharging and recovering unit is used for vacuumizing the gas closed chamber;

and step 3: the gas charging, discharging and recovering unit charges gas with required pressure into the gas closed chamber;

and 4, step 4: the voltage source supplies power to the resistance wire;

and 5: the temperature measuring instrument measures the temperature of the gas in the gas closed room;

step 6: judging whether the gas temperature in the gas closed chamber reaches the target temperature, if so, executing the step 7, otherwise, executing the step 4;

and 7: turning off the voltage source, and stopping supplying power to the resistance wire;

and 8: the VFTO generating unit loads VFTO on the anode electrode plate and the cathode electrode plate at the same time;

and step 9: the spectrometer measures the intensity and wavelength of the spectrum generated by the gas plasma and transmits the intensity and wavelength to the computer;

step 10: judging whether the gas breaks down under VFTO according to whether the indicated value of the ammeter changes, if so, determining that the gas breaks down under VFTO, and executing the step 11, and if not, determining that the gas does not break down under VFTO, and executing the step 9;

step 11: the gas charging, discharging and recovering unit is used for vacuumizing the gas closed chamber;

step 12: the computer calculates the temperature of various particles in the plasma according to the intensity and wavelength of the received spectrum generated by the gas plasma;

step 13: the computer calculates the distribution of various particles in the gas breakdown process according to the temperature of various particles in the gas plasma to obtain the distribution function of various particles in the gas breakdown process;

the distribution of various particles during gas breakdown is obtained by boltzmann equation (1),

$\frac{\&part;f}{\&part;t}+v\&CenterDot;\frac{\&part;f}{\&part;r}+eE\&CenterDot;\frac{\&part;f}{\&part;p}={\&dtri;}_p\&CenterDot;s---\left(1\right)$

wherein s is momentum spaceInter particle flow density in units of units/m³T is time in seconds, r is the position of the particle in meters ▽_pIs the full differential of s to momentum, p is the momentum of the particle in kg.m/s, and the component of s in the direction of α axis is s_α，s_αObtained by the formula (2), wherein the α axis is an X axis, or the α axis is a Y axis, or the α axis is a Z axis;

$s_{\mathrm{\&alpha;}}={\mathrm{\&sigma;}}_t{u}^2\&CenterDot;\left|v-v^{\&prime;}\right|\&Integral;\&Integral;\&Integral;(f\frac{\&part;f^{\&prime;}}{\&part;p_{\mathrm{\&beta;}}^{\&prime;}}-f^{\&prime;}\frac{\&part;f}{\&part;p_{\mathrm{\&beta;}}})\&times;({\left(v-v^{\&prime;}\right)}^2{\mathrm{\&delta;}}_{\mathrm{\&alpha;}\mathrm{\&beta;}}-(v_{\mathrm{\&alpha;}}-{v_{\mathrm{\&alpha;}}}^{\&prime;}\left)\right(v_{\mathrm{\&beta;}}-{v_{\mathrm{\&beta;}}}^{\&prime;}\left)\right)d^3{p}^{\&prime;}---\left(2\right)$

wherein σ_tIs a transport section, obtained by formula (3); u is the reduced mass of the particles,m and m 'are the mass of two colliding particles with momentum p and p', respectively, and the unit is kg; v and v 'are the particle velocity with momentum p and the particle velocity with momentum p', respectively, and the unit is m/s; f is the distribution function of particles with momentum p; f 'is the distribution function of particles with momentum p'; p'_βThe component of momentum p' in the direction of β axis, β axis is X axis, or β axis is Y axis, or β axis is Z axis, p_βIs the component of momentum p in the direction of axis β;_αβis a unit tensor; v. of_αThe component of the velocity of the particle with momentum p in the direction of α axis is expressed in m/s, v_α'is the component of the particle velocity α axis direction with momentum p', and the unit is m/s_βWith the velocity of the particles being p in the direction of the β axisComponent in m/s; v. of_β'is the component of the particle velocity β axial direction with momentum p', in m/s;

${\mathrm{\&sigma;}}_t={\mathrm{\&sigma;}}_e+{\mathrm{\&sigma;}}_r=\frac{2\mathrm{\&pi;}}{k^2}\underset{l=0}{\overset{\mathrm{\&infin;}}{\&Sigma;}}(2l+1)(1-|S_l{|}^2)---\left(3\right)$

wherein σ_eIs an elastic scattering cross section; sigma_rIs an inelastic scattering cross section; k is the wave number of the incident particle and is determined according to equation (4); l is angular momentum in kg m²/s；S_lIs a random number modulo less than 1, S_l1 indicates the complete absence of such scattering, S_l0 means that the particle with angular momentum of l is completely absorbed;

wherein,is Planck constant;e is the energy of the scattering particles in joules; m is₁The mass of the lighter particles in the two collision particles is kg;

step 14: and respectively calculating the diffusion coefficient, the conductivity and the viscosity coefficient of the particles by the computer according to the distribution functions of various particles in the gas breakdown process.