Plasma-assisted abatement of SF6 in a packed bed plasma reactor: understanding the effect of gas composition

The potential impact of SF6 as a potent greenhouse gas on the global climate is highly attractive.This paper studies the effect of H2O concentration,SF6 inlet concentration and pre-heating temperature on SF6 abatement in a packed bed plasma reactor in terms of the removal efficiency and products selectivity.The results showed that the best performance in SF6 abatement was obtained at 1%H2O and 100°C with 98.7%destruction and remove efficiency(DRE)at 2%SF6.Higher energy yields was obtained under higher SF6 inlet concentration.Moreover,the existence of water vapor weakened the micro-discharge and provided H and OH radicals for this system,which showed a close relationship to removal efficiency and products selectivity.Among four sulfur-containing products,SO2 F2 was more stable than SOF2,SOF4 and SO2.Meanwhile,SOF4 and SO2 were very susceptible to the above parameters.This article provides a better understanding of SF6 abatement in a view of both scientific and engineering.

Multichannel Discharge Characteristics of Gas Switch Gap in SF_6-N_2 or SF_6-Ar Gas Mixtures Under Nanosecond Triggering Pulses

Experiments were carried out to ascertain multichannel discharge characteristics in a self-designed coaxial field-distortion gas switch filled with SFa-N2 or SF6-Ar gas mixtures of different mixing ratios. In these experiments, the pressure varied from 0.1 MPa to 0.2 MPa, the voltage pulse peak applied to the switch was in the range from 40 kV to 78 kV, and the pulse rise time was 11 ns. The static breakdown strength of the gas switch gap in the switch was also measured. The results show that in general the average number of discharge channels for SF6-Ar or SF6-N2 gas mixture which contains less SFa is larger than that for gas mixture which contains more SF6, however, the average number of channels almost keeps constant as the gas mixing ratio varies when the pulse rise rate is high enough. The static breakdown strength of the gas switch gap decreases slightly as the content of argon or nitrogen increases.

Varian2100C加速器SF6气体漏气的检修

故障现象：每次开机后气压低出GAS联锁,补充SF6气体后联锁消失,可正常使用一天,但第二天开机故障依旧。分析与检修：正常情况下,传输微波的波导管内SF6气体的压力设置在30-32PSI之间。低于30PSI或高于32PSI均会出GAS联锁。每次开机GAS压力表指示27PSI左右,说明存在轻微漏气。

Discharge Characteristics of SF_6 in a Non-Uniform Electric Field Under Repetitive Nanosecond Pulses

The characteristics of high pressure sulphur hexafluoride（SF6） discharges in a highly non-uniform electric field under repetitive nanosecond pulses are investigated in this paper.The influencing factors on discharge process,such as gas pressure,pulse repetition frequency（PRF）,and number of applied pulses,are analyzed.Experimental results show that the corona intensity weakens with the increase of gas pressure and strengthens with the increase of PRF or number of applied pulses.Spark discharge images suggest that a shorter and thicker discharge plasma channel will lead to a larger discharge current.The number of applied pulses to breakdown descends with the increase of PRF and ascends with the rise of gas pressure.The reduced electric field（E/p） decreases with the increase of PRF in all circumstances.The experimental results provide significant supplements to the dielectric characteristics of strongly electronegative gases under repetitive nanosecond pulses.

基于SF_6分解产物的GIS设备放电类型与位置的诊断方法

针对目前工作中监测SF_6中SO_2、H_2S的浓度无法有效指导放电故障诊断的问题,首先,从SF_6在放电状况下分解的机制出发,分析不同放电类型下不同放电位置SF_6中可能产生的分解产物;提出利用特征值和特征物质种类诊断GIS设备放电类型和位置的方法,并在实际案例中得到验证。

Characteristics of SF_6 Switch with a Small Gap under High Pressure and Nanosecond Pulse

Structural design and tests on the characteristics of the SF6 gas switch with a small gap are presented. This kind of switch often works under high pressure and nanosecond pulse for getting pulse with faster risetime. The breakdown voltage and breakdown delay of a number of switches with different geometries, gas pressures and pulse waveforms were investigated. Experimental results suggested that the breakdown voltage increases linearly with the gas pressure, and the breakdown delay decreases with an increase in the gas pressure and a reduction in the gap distance of the switch under the same applied pulse. By using this kind of switch with a gap of 3 mm as a peaking switch, a pulse generator can provide an output voltage with a peak voltage of 300 kV and a risetime of 3 ns on a resistance load of 150Ω.

Analysis of the Molecules Structure and Vertical Electron Affinity of Organic Gas Impact on Electric Strength

It is necessary to find an efficient selection method to pre-analyze the gas electric strength from the perspective of molecule structure and the properties for finding the alternative gases to sulphur hexafluoride （SF6）. As the properties of gas are determined by the gas molecule structure, the research on the relationship between the gas molecule structure and the electric strength can contribute to the gas pre-screening and new gas development. In this paper, we calculated the vertical electron affinity, molecule orbits distribution and orbits energy of gas molecules by the means of density functional theory （DFT） for the typical structures of organic gases and compared their electric strengths. By this method, we find part of the key properties of the molecule which are related to the electric strength, including the vertical electron affinity, the lowest unoccupied molecule orbit （LUMO） energy, molecule orbits distribution and negativeion system energy. We also listed some molecule groups such as unsaturated carbons double bonds （C=C） and carbonitrile bonds （C=N） which have high electric strength theoretically by this method.

Review of supershort avalanche electron beam during nanosecond-pulse discharges in some gases

Supershort avalanche electron beam(SAEB)plays an important role in nanosecond-pulse discharges.This paper aims at reviewing ex-periments results on characteritics of SAEB and its spectra in different gases in nanosecond-pulse discharges.All the joint experiments were carried in the Institute of High Current Electronics of the Russian Academy of Sciences and the Institute of Electrical Engineering of the Chinese Academy of Sciences.In these experiments,the generation of a SAEB in SF 6 in an inhomogeneous electric field was studied on three generators with pulse rise times of 0.3,0.5 and~2 ns.Firstly,the comparison of SAEB parameters in SF 6 with those obtained in other gases(air,nitrogen,argon,and krypton)is introduced.Secondly,the SAEB spectra in SF 6 and air at pressures of 10 kPa(75 torr),and 0.1 MPa(750 torr)are reviewed and discussed.Finally,1.5-D theoretical simulation of the supershort pulse of the fast electron beam in a coaxial diode filled with SF 6 at atmospheric pressure is described.The simulation was carried out in the framework of hybrid model for discharge and runaway electron kinetics.The above research progress can provide better understanding of the investigation into the mechanism of nanosecond-pulse discharges.

阀切换技术在大气样品中六氟化硫快速分析中的应用

建立了双柱阀切换技术分析大气样品中的SF6含量的气相色谱-电子捕获检测器（GC-ECD）检测方法。采用规格为3.2mm×1m的5A分子筛（40-60目）柱为预柱,规格为3.2mm×0.5m的5A分子筛（60-80目）柱为分析柱。在所用实验条件下,平均峰高响应为1.08×10^-14mL/μV,SF6单位体积进样量的色谱峰高的相对标准偏差为2.2%,SF6的最低检测限为6.03×10^-13mL（3倍基线噪声）。采用该方法分析大气中SF6的含量,样品分析时间为1.2min,于12min内完成11个空气样品的分析,SF6含量的相对标准偏差2.1%。

Study of partial discharge characteristics in HFO-1234ze(E)/N2 mixtures

HFO-1234 ze(E)(trans-1,3,3,3-tetrafluoropropene,chemical formula:C3H2F4)is an extremely environmentally friendly SF6 alternative gas with high electrical strength.In this paper,the partial discharge(PD)characteristics of HFO-1234 ze(E)/N2 mixtures were studied using the gas insulation test platform.The PD inception voltage of insulating gas under positive and negative half cycles of power frequency was tested.Using SF6/N2 mixtures as a control group,the effects of electrode spacing,mixing ratio and pressure on the insulation performance of HFO-1234 ze(E)/N2 mixtures were explored.The test results show that the PD inception voltage of the negative half-cycle of pure HFO-1234 ze(E)under short electrode spacing can reach 0.96-1.04 times of pure SF6 under different pressures;the PD inception voltage of40%HFO-1234 ze(E)/60%N2 mixtures at 0.3 MPa is 0.67-0.89 times that of SF6/N2 mixtures under the same conditions,which has great application prospect.

单壁碳纳米管气体传感器在GIS局部放电检测中的应用(英文)

This paper describes a realizable fabrication method to manufacture chemical gas sensors by using singlewalled carbon nanotubes(SWCNTs).The sensors were tested for the monitoring of SF_6 decomposition gas produced by partial discharge(PD) in GIS tank.The results showed a superior sensitivity,favorable reliability and good reproducibility. For further clarifying the relativity between sensor response and partial discharge activity,the discharge in GIS tank was monitored simultaneously through conventional pulse current method and a SWCNTs gas sensor,and the measurement results were put together for comparative analysis in this paper.The sensor response showed a great dependence on partial discharge characteristics.The sensor response increased nearly linearly with limits when the energy of discharge was persistently accumulated.Partial discharge power had a great influence on the response rate and the time delay.With the increase of partial discharge power,the response rate augmented almost in proportion while the time delay gradually becomes shorter with limits.The results were quite favorable to assess the partial discharge intensity and duration to some extent.Compared with pulse current method,the sensor was predominant to detect partial discharge exposed to constantly high levels of noise.It was capable of detecting partial discharge which was too weak to be detected with pulse current method.However,the sensor response didn't show much dependency on the apparent discharge of partial discharge.

Insulation characteristics of triple mixtures of c-C_4F_8/N_2/CO_2 under lightning impulse voltage

This paper has researched the insulation characteristics of 10% c-C4F8/N2/CO2 mixtures under lightning impulse voltage by experiment. It is shown that the positive and negative lightning impulse breakdown voltages of 10%c-C4F8/N2/CO2 gas mixtures rise linearly as the electrode gap distance and gas pressure increase and under the same conditions, the positive lightning impulse breakdown voltage of the gas mixtures is always higher than the negative lightning impulse breakdown voltage. As the gas mixtures have a little higher liquefied temperature than SF6 and the comprehensive GWP is about 5% of SF6, and the positive and negative lightning impulse breakdown voltages can both reach 60% of SF6, 10%c-C4F8/N2/CO2 gas mixtures can be applied as insulation gas in electrical equipment such as C-GIS, GIT, GIL and so on.

浅论六氟化硫组合开关安装的管理

随着国民经济的发展需要,高压配电SF6的装置广泛应用于水电站、城区变电站。做好SF6的安装、维护,能保证电力系统的安全运行。

Estimation of the Type of Low Energy Discharge in GIS Adopting Characteristic Gas

In order to guarantee safe operations, low energy discharge within gas insulated switchgear （GIS） should be detected as soon as possible before they develop severely and cause final breakdown failures. This paper aims to present a GIS discharge diagnosis technique adopting gaseous decompositions. To reach this aim, needle-plate electrode and the sphere-plate electrode with metallic particles on the plate are designed to simulate two kinds of low energy discharge, namely, corona discharge and spark discharge, respectively. After sampling and analyzing the gases, different yields of gaseous by-products under different types of low energy discharge are obtained. Based on the decomposition mechanisms reported by previous researches and the experiment results, it can be concluded that S2OF10, SO2F2 , and SO2 can be used as the characteristic gas to identify low energy discharge; the increment of S2OF10 can indicate the occurrence of low energy discharges while the volume ratio between SO2F2 and SO2 can define the type of low energy discharge.

Study of RPC gas composition using Daya Bay RPCs

This study uses Daya Bay RPCs operating in streamer mode to investigate gas mixtures of at least 50% argon, at most 6% isobutane, and with small amounts of SF6. Isobutane is reduced to 2% without degradation of performance, and SF6 reduces the noise rate and current, as well as the signal size. This study provides quantitative relationships between basic RPC operating parameters and various gas compositions.