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Improvement of Surface Flashover Performance of Al_2O_3 Ceramics in Vacuum by Adopting A-B-A insulation System

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Plasma Science and Technology 2011年第2期13卷 235-241页

作者：李盛涛张拓黄奇峰李巍巍倪风燕李建英 state key laboratory of electrical insulation and power equipment Xi'an Jiaotong University

A new insulation system with inorganic A-B-A insulators was proposed to improve the surface flashover performance in vacuum. Inorganic A-B-A insulator samples of Mo/Al2O3 cermet-Al2O3 ceramic-Mo/Al2O3 cermet were prepared, in which the conductivity and permittivity of the Mo/Al2O3 cermets were controlled through different amount of metallic molybdenum powder added. The effects of both conductivity and permittivity of Mo/Al2O3 cermets on the DC and impulse surface flashover voltage in vacuum were experimentally investigated. The result showed that the DC and impulse surface flashover voltage were improved by 52% and 95%, respectively. For the distribution of electric field, two triple junctions, i.e., vacuum-layer A-cathode （TJ1） and vacuum-layer A-layer B （TJ2） were prepared with the introduction of layer A into the A-B-A insulation system. Based on the electric field distribution obtained via electrostatic field simulation and Maxwell-Wagner three-layer model, the electric field of T J1 decreases while that of T J2 increases with the increase in conductivity and permittivity of layer A under applied DC and impulse voltage, respectively. Therefore, the improvement of surface flashover performance of A-B-A insulators has been reasonably explained.

关键词： surface fiashover in vacuum A-B-A insulator triple junction electric field distribution cermet

Investigation on X-Radiation for 126 kV Vacuum Interrupters

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Plasma Science and Technology 2016年第5期18卷 577-582页

作者：闫静刘志远耿英三张胜张颖瑶 state key laboratory of electrical insulation and power equipment Xi'an Jiaotong University

When subjected to high voltages between opened contacts, vacuum interrupters may emit X-rays. In order to ensure that these are of an acceptable level, vacuum interrupters should comply with the limits for X-ray emission and the test procedures to be carried out to verify this based on relevant standards and specifications. In this paper, a comprehensive experimental study has been performed for 126 kV vacuum interrupters used in a transmission system to understand the X-radiation level and its influence by three main parameters, namely applied power-frequency voltage, contact gap and power=frequency voltage conditioning. The radiation instrument is an FJ347 radiometer and the X-radiation dose was measured at the power-frequency test voltage. These tests demonstrated that the X-radiation emission level for a 126 kV vacuum interrupter did not exceed the following： 5 μSv per hour at a rated voltage of 126 kV and 150 μSv per hour at a power-frequency voltage of 230 kV at 1 m distance. The X-radiation dose increased with the applied power-frequency voltage increasing and decreased with the contact gap increasing. The X- radiation dose for 126 kV vacuum interrupters decreased by 57% after the conditioning procedure with a certain power-frequency voltage. During the conditioning procedure, the average value of the X-radiation dose was 4.49 mSv, which means if a professional conditions 180 interrupters per year, it will be safe at the 6.4 m distance.

关键词： vacuum interrupter X-radiation power-frequency voltage contact gap volt-age conditioning

Influence of arc current and pressure on non-chemical equilibrium air arc behavior

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Plasma Science and Technology 2018年第1期20卷 142-149页

作者：吴翊崔彧菲段嘉炜孙昊王春林纽春萍 state key laboratory of electrical insulation and power equipment Xi'an Jiaotong University

The influence of arc current and pressure on the non-chemical equilibrium （non-CE） air arc behavior of a nozzle structure was investigated based on the self-consistent non-chemical equilibrium model. The arc behavior during both the arc burning and arc decay phases were discussed at different currents and different pressures. We also devised the concept of a non- equilibrium parameter for a better understanding of non-CE effects. During the arc burning phase, the increasing current leads to a decrease of the non-equilibrium parameter of the particles in the arc core, while the increasing pressure leads to an increase of the non-equilibrium parameter of the particles in the arc core. During the arc decay phase, the non-CE effect will decrease by increasing the arc burning current and the nozzle pressure. Three factors together-- convection, diffusion and chemical reactions--influence non-CE behavior.

关键词： arc buming phase arc decay phase chemical reaction arc current pressure

Influence of the gassing materials on the dielectric properties of air

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Plasma Science and Technology 2017年第5期19卷 68-73页

作者：张含天厉天威罗兵吴翊杨飞孙昊唐力 state key laboratory of electrical insulation and power equipment Xi'an Jiaotong University state key laboratory of HVDC Electric Power Research InstituteChina Southern Power Grid

Influence of the gassing materials, such as PA6, PMMA, and POM on the dielectric properties of air are investigated. In this work, the fundamental electron collision cross section data were carefully selected and validated. Then the species compositions of the air–organic vapor mixtures were calculated based on the Gibbs free energy minimization. Finally, the Townsend ionization coefficient, the Townsend electron attachment coefficient and the critical reduced electric field strength were derived from the calculated electron energy distribution function by solving the Boltzmann transport equation. The calculation results indicated that H;O with large attachment cross sections has a great impact on the critical reduced electric field strength of the air–organic vapor mixtures. On the other hand, the vaporization of gassing materials can help to increase the dielectric properties of air circuit breakers to some degree.

关键词： air circuit breaker gassing materials Boltzmann equation analysis dielectric properties EEDF critical reduced electric field strength electron collision cross section

Experimental Research of ZnO Surface Flashover Trigger Device of Pseudo-Spark Switch

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Plasma Science and Technology 2014年第5期16卷 506-511页

作者：黄忠德姚学玲陈景亮邱爱慈 The state key laboratory of electrical insulation and power equipment Xi'an Jiaotong University

Pseudo-spark switch（PSS） is one of the most widely used discharge switches for pulse power *** has many special characteristics such as reliability in a wide voltage range,small delay time,as well as small delay *** this paper,the measuring method for the initial plasma of ZnO surface flashover triggering device of PSS is studied and the results of the measurement show that the electron emission charge is mainly influenced by trigger voltage,gas pressure and DC bias *** the bias voltage increases from 2 kV to 6 kV with the gap distancc fixed at 3 mm,the electron emission charge changes from 2 μC to about 6μ*** the gap distance changes from 3 mm to 5 mm with the bias voltage fixed at 2 kV,the electron emission charge increases from 1.5 μC to 2.5μ*** the gap distance is 4 mm,the hold-off voltage of PSS is 45 kV at gas pressure of 2 Pa,the minimum operating voltage is less than 1 ***,the operating scope is from 2.22%to 99%of its self-breakdown *** discharging delay time decreases from 450 ns to 150 ns when the trigger pulse voltage is 1 kV and the discharging voltage is changed from 1 kV to 12 *** the trigger pulse voltage is 6 kV,the discharging delay time is less than 100 ns and changes from 100 ns to 50 ns,and the delay jitters are less than30 ns.

关键词： pseudo-spark switch ZnO surface flashover trigger device electron emission charge discharging delay

An Active Triggered Surge Protective Gap

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Plasma Science and Technology 2012年第8期14卷 759-764页

作者：姚学玲陈景亮 state key laboratory of electrical insulation and power equipment Xi'an Jiaotong University

A triggered surge protective device is designed and its discharge characteristics axe studied. The experimental results show that the triggered surge protective device has excellent surge protective characteristics. When the gap distance is 5 mm, p. d is 90 *** and without an active energy trigger circuit, the DC breakdown voltage of the triggered surge protective device is 2.32 kV and the pulse breakdown voltage is 5.75 kV. Therefore, the pulse voltage ratio, which is defined as the specific value of pulse breakdown voltage and DC breakdown voltage, is 2.48. With a semiconductor ZnO flashover trigger device and an active energy coupling trigger circuit, the pulse breakdown voltage can be reduced to 3.32 kV, the pulse voltage ratio is 1.43 and the response time is less than 100 ns. These results are helpful in laying a theoretical foundation for further studies on triggered surge protective devices.

关键词： surge protective gap flashover trigger device active energy coupling trigger response time pulse voltage ratio

The Influence of Contact Space on Arc Commutation Process in Air Circuit Breaker

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Plasma Science and Technology 2016年第5期18卷 460-464页

作者：纽春萍丁炬文杨飞董得龙荣命哲徐丹 state key laboratory of electrical insulation and power equipment Xi'an Jiaotong University

In this paper, a 3D magneto-hydrodynamic （MHD） arc simulation model is applied to analyze the arc motion during current interruption in a certain air circuit breaker （ACB）. The distributions of pressure, temperature, gas flow and current density of the arc plasma in the arc region are calculated, and the factors influencing the commutation process are analyzed according to the calculated results. Based on the airflow in the arc chamber, the causes of arc commutation asynchrony and the back commutation are investigated. It indicates that a reasonable contact space design is crucial to a successful arc commutation process. To verify the simulation results, the influence of contact space on arc voltage and arc commutation is tested. This research can provide methods and references to the optimization of ACB design.

关键词： air circuit breaker arc simulation arc commutation arc chamber

Influence of Pulse Steepness on Vacuum Flashover of Casting Epoxy Resin

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Plasma Science and Technology 2009年第1期11卷 89-93页

作者：陈玉成永红王增彬周稼斌孟国栋吴锴李盛涛 state key laboratory of electrical insulation and power equipment Xi'an Jiaotong University

Research on the pulsed flashover characteristics of vacuum insulation material is significant for the design and manufacture of pulse power devices. In view of the voltage increase rate of the fast pulse （pulse steepness）, the vacuum fiashover characteristics of pure epoxy under different steepnesses is investigated by using a pulse generator with parameters of a rise time of 40 ns and a full width at half maximum of 2.5 μs. Pulses with six levels of steepness were achieved by changing the charging voltage of the generator. Based on the linear equation and electron emission equation, the relationship between the flashover voltage and pulse steepness was fitted. By virtue of the fitted formula, it was possible to predict the flashover voltage under near DC or higher steepness conditions. Based on the electron emission equation, the relationship between the time delay and flashover field was also fitted. Result shows that F-N electron emission dominates the flashover process.

关键词： pulse steepness casting epoxy resin vacuum flashover electron emission equa- tion flashover time delay

Emission Current Characteristics of Triggered Device of Vacuum Switch

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Plasma Science and Technology 2014年第4期16卷 380-384页

作者：姚学玲陈景亮胡上茂 state key laboratory of electrical insulation and power equipment Xi'an Jiaotong University

The characteristics of the triggered vacuum switch （TVS） are obviously influenced by the emission current ie and emission charge of the trigger device. In this paper, an RC charge collector is designed, and the characteristics of emission current ie and collecting charge Qc of the trigger device are studied. The experimental results indicate that the emission current ie which is produced by the initial plasma has both positive and negative components, and the polarity of the emission current ie depends mainly on the polarity of the bias voltage UBias. The emission current ie and collecting charge Qe increase with the increase of the trigger voltage Utr and the bias voltage UBias. The emission efficient r] increases linearly with the increase of the bias voltage UBias. When the gap distance is 15 mm and bias voltage UBias is 160 V and trigger voltage Utr is 2.6 kV, the emission efficiency r/reaches 6%

关键词： emission current~ collecting charge triggered device~ vacuum switch