1.2 MV大功率直流高压电源研制

 采用等边三角形结构的铁芯,次级线圈分成40级,分别进行三相全波整流,每级输出直流30 kV,串联后获得1.2 MV/A的直流高电压大功率输出。电源的能量转换效率大于95%,漏抗高达21.7%。采用无滤波电容结构,次级线圈星型/三角型接法交替使用,纹波系数小于±4%。整个电源密封在压力钢筒中,充0.8 MPa高纯度SF6气体作为绝缘介质,最大工作场强小于130 kV/cm。设计了专门的SF6气体冷却系统,气体温度控制在60 ℃以内,高电压由充气同轴传输线输出。在小负载条件下,电源各项指标满足技术要求,已经安装在1.2 MW,1.2 MeV大功率直流电子加速器上进行整机联调。     

Comparison of magnetic resonance imaging of inhaled SF6 with respiratory gas analysis

Magnetic resonance imaging of inhaled fluorinated inert gases ((19)F-MRI) such as sulfur hexafluoride (SF(6)) allows for analysis of ventilated air spaces. In this study, the possibility of using this technique to image lung function was assessed. For this, (19)F-MRI of inhaled SF(6) was compared with respiratory gas analysis, which is a global but reliable measure of alveolar gas fraction. Five anesthetized pigs underwent multiple-breath wash-in procedures with a gas mixture of 70% SF(6) and 30% oxygen. Two-dimensional (19)F-MRI and end-expiratory gas fraction analysis were performed after 4 to 24 inhaled breaths. Signal intensity of (19)F-MRI and end-expiratory SF(6) fraction were evaluated with respect to linear correlation and reproducibility. Time constants were estimated by both MRI and respiratory gas analysis data and compared for agreement. A good linear correlation between signal intensity and end-expiratory gas fraction was found (correlation coefficient 0.99+/-0.01). The data were reproducible (standard error of signal intensity 8% vs. that of gas fraction 5%) and the comparison of time constants yielded a sufficient agreement. According to the good linear correlation and the acceptable reproducibility, we suggest the (19)F-MRI to be a valuable tool for quantification of intrapulmonary SF(6) and hence lung function.     

200kV小型低电感气体开关

为减小脉冲功率源装置的体积,对场畸变三电极轨道气体开关和两电极轨道气体开关结构进行了小型化低电感设计,采用电磁场仿真软件对局部结构进行优化,对初步设计的触发开关和自击穿开关在不同气压(0~0.3MPa)和不同气体介质(N2,SF6,以及二者混合)条件下的击穿电压及导通电感等进行了研究。研究表明:小型触发开关和自击穿开关在0~0.3MPa气压范围内自击穿电压随气压具有较好的线性关系;相同气压下SF6气体的自击穿电压约为N2气体的两倍;N2与SF6压力按3∶2混合的自击穿电压约为纯SF6气体的0.8~0.9倍;内部充入0.25MPa气压的SF6气体时,触发开关和自击穿开关均可在190kV左右正常工作。根据实验中出现的开关沿面击穿现象,对开关的沿面绝缘能力进行了优化设计,并得到了实验验证。另外通过短路放电测试,得到触发开关电感约22nH,自击穿开关电感约20nH,开关导通电流大于20kA,多次放电后电极烧蚀痕迹分布均匀。     

Interruption Capability of Gases and Gas Mixtures in a Puffer-Type Interrupter

SF6 gas has been widely used in arc interruption applications for the past 20 years. Reported here is a systematic, comprehensive effort to search for and evaluate gases and gas mixtures suitable as an arc interruption medium potentially superior to SF6. The search began with several hundred gases, narrowed down to about forty, and finally fifteen gases and gas mixtures were evaluated in a full size puffer-type interrupter under 60-Hz high-power conditions. The results showed SF6 stood out as having the best interruption ability with several mixtures having ~80 percent of SF6' s performance.     

非定常空气流场中污染气体的对流与粘性扩散

基于离散涡方法求得的非定常、不稳定空气流场，数值求解了污染气体在空气中的对流湍流扩散方程．两者在每一个时间步耦合，以求非定常对流项．考虑速度脉动，改进了扩散模式．用SF6作为示踪气体，进行了现场测量实验．测得了各测点的SF6浓度随时间的变化．实验结果与数值仿真进行了对比，两者吻合．     

放电激励重复频率非链式HF激光器

 利用紫外预电离横向放电和气体循环结构建立了一套放电激励重复频率HF激光装置。研究了激光器工作介质SF6/C2H6混合气体放电特性和激光输出特性,获得激光器单次运行的最佳输出参数;通过对激光器重复频率运行时不同气体流速、充电电压与气体总压条件下的放电状态和输出能量的比较,分析了激光器重复频率稳定运行的必要条件。结果表明：所研制的激光器最大单脉冲能量0.6 J,峰值功率3 MW,电光转换效率2.4%;当混合气体工作介质以3.5 m/s的流速循环时,激光器稳定运行的最高工作频率可达50 Hz,脉冲输出能量稳定在0.26 J,平均功率达到13 W。     

Investigations of Nozzle Materials in SF6 Circuit Breakers

With a puffer and a self-blast type SF6 circuit breaker (CB), various nozzle materials have been investigated. In addition, a small-scaled model SF6 breaker has been attached to a time-of-flight mass spectrometer (TOFMS) in order to study the exhausted gas contaminated with ablated material. The experimental results clearly show an influence of the nozzle material on the interrupting capability of the SF6 CB. The observed nozzle ablation is mainly determined by the geometry of the arcing device. The erosion of the nozzle and the chemical composition of arced SF6 gas depend slightly on the quality of the PTFE nozzles only.     

直流场畸变开关中混合气体击穿特性

氩气中一般含有大量亚稳态原子,在强外电场作用下容易产生自由电子,能够促进放电通道快速形成。采用场畸变型气体开关,在直流电压下设计了实验平台来探究气体开关中采用SF6-Ar或N2-Ar混合气体后放电时延及抖动的变化情况。改变多种气体状态进行一系列实验,并得出场畸变气体火花开关中SF6-Ar及N2-Ar的击穿特性,根据工程需要对气体种类及混合比例进行最优化设计。实验表明SF6-Ar中Ar质量分数达到20%及以上时,开关放电时延及抖动明显减小。     

焦耳级放电激励紫外预电离HF激光器

研制了一台采用紫外火花预电离和横向放电结构的非链式电激励脉冲HF激光装置,采用氢闸流管结合一级磁脉冲压缩开关的高功率电激励系统。实验研究了激光工作介质SF6,H2不同压强比和总工作气压对激光输出能量的影响,得出了最佳气体组分,确定了最佳工作气压。总气压在8.8 kPa,气体组分H2与SF6气压比为1:9时,获得最佳的激光输出,输出能量达到1.3 J,激光器的光电转换效率达到2.4%。:     

SF6-N2混合气激光触发延迟抖动特性研究

 研究了SF₆-N₂混合气在四倍频Nd:YAG激光脉冲作用下的触发特性。实验结果表明：充SF₆-N₂混合气的火花隙的触发延迟和抖动、最低可触发阈值随充气压力及混合气中SF₆含量上升而上升，随激光波长减小而减小，火花隙的触发延迟和抖动随焦距的减小而减小。由于SF₆-N₂混合气的介电强度、触发延迟和抖动与混合气中SF₆含量之间均存在非线性关系，作为开关工作介质，SF₆-N₂混合气的综合性能较好的SF₆含量范围是5%～45%。     

Magnetic Control of Diffuse Discharges

By application of a crossed magnetic field, the electron energy distribution in a gas discharge can be shifted to lower energy values, as demonstrated by means of Monte Carlo calculations for electrons in He:SF6 mixtures. Consequently, through the change in the rate coefficients for ionization and attachment, the sustaining field in the discharge plasma is increased. This magnetically induced voltage rise was studied in a low-pressure glow discharge. The cathode fall was found to be the dominant component in determining the characteristics of this magnetically controlled discharge. The drastic rise of the cathode fall above a threshold value could be utilized in operating a glow discharge as an opening switch for an inductive energy storage system.     

Large eddy simulation of a shocked gas cylinder instability induced turbulence

The Navier-Stokes equations for compressible fluid are solved with the operator splitting technique and LES (large eddy simulation) with the Smagorinsky model. A computational code MVFT (multi-viscosity-fluid and turbulence) is developed to study hydrodynamic instability and the induced turbulent mixing for multi compressible fluid. In order to validate the code MVFT,the LANL's shock tube experiment of shocked SF6 gas cylinder is simulated with the initial state of SF6 gas cylinder described by dissipative ...     

SF_6气体及其衍生物的红外光谱分析

SF6气体大量应用于气体绝缘组合电器(GIS)中。通过化学方法检测SF6气体及其衍生物是检测GIS设备故障的一种重要方法。该文采用红外光谱技术分析了三种情况下的GIS设备内SF6气体组成情况,得出S2F10气体含量可以用来分析GIS故障原因是否为强火花或者电弧放电引起;CF4气体可以用来表征GIS设备内绝缘气体的绝缘状态。另外,研究表明,GIS设备在线运行时,绝缘气体气室密封失效、造成气体泄漏,引入新的气体杂质的问题比较严重。所以在进行GIS设备维护工作时,绝缘气室的密封维护工作十分重要。文章在研究GIS设备绝缘气体SF6红外谱图的基础之上提出了建立基于红外光谱技术的GIS设备故障诊断专家系统的意见。     

基于多尺度加权主成分分析的SF6红外光谱分析

利用红外光谱法分析SF6气体及其衍生物是判断气体绝缘组合电器(GIS)运行状态和故障的一种重要手段。传统的诊断方法过程繁琐、效率低下,而且受主观因素的影响较大。本文指出可以采用机器学习的方法实现GIS设备的故障诊断,并提出了多尺度加权主成分分析的特征提取方法。多尺度加权主成分分析结合了主成分分析和多尺度分解的特点,保证了尺度特征信息的最大化,并且修正了特征向量在数据分类时的权重。通过对广西电力研究院提供的SF6及其衍生物的红外光谱进行分析,证明了多尺度加权主成分分析算法对训练样本的分类效果要比标准的主成分分析算法好3～4倍。     

Parametric dependencies for photoacoustic leak localization

Unintended gas or liquid leaks from manufactured components or manufacturing systems may be detrimental to consumers, manufacturers, and the environment. Thus, leak testing is important for quality, safety, and environmental reasons. This paper describes parametric dependencies for photoacoustic leak localization. The technique is based on the interaction of 10.6-micrometer radiation from a carbon dioxide (CO2) laser and a photoactive tracer gas, sulfur hexafluoride (SF6). For the current investigations, acoustic signals are generated by scanning a laser beam at high speed through gas plumes formed above calibrated leaks. These signals are remotely measured with a four-microphone linear array and analyzed using Bartlett and minimum-variance-distortionless (MVD) matched-field processing (MFP) techniques to determine leak location. This paper extends prior work in photoacoustic leak testing through (i) use of more signal frequencies; (ii) parametric study of four different laser scan rates; and (iii) examination of mismatch between the actual acoustic environment and the propagation model used in the MFP; and (iv) presentation of leak localization results on a curved surface. For a 12-watt CO2 laser exciting the small SF6 gas plume produced by a one-cm3-per-day leak with microphones placed 0.41 m from the leak location, root-mean-square localization uncertainties as small as +/-0.5 mm on a line scan of 0.46 m can be achieved when the largest possible number of signal frequencies fall in a measurement bandwidth of approximately 70 kHz.     

Thermalization of a two-phase fluid in low gravity: heat transferred from cold to Hot

We present an experimental study of the thermal response to a positive temperature quench in two-phase fluid SF6 in low gravity for temperature ranging from 10.1 to 0.1 K from the critical temperature. The temperature was measured simultaneously in the gas, the liquid, and the cell wall by thermistors and the density distribution was observed by interferometry. During the quench the gas temperature considerably exceeded the temperature of the heating walls (overheating up to 23%). This striking observation is discussed in the light of the adiabatic heat transfer in this highly compressible fluid while the key role of the localization in low gravity of the gas and liquid phases is revealed.     

激光触发多级多通道开关触发延迟及其抖动特性

 研究了激光触发多级多通道开关的触发延迟时间及其抖动与激光脉冲能量等实验参量的依赖关系，建立了零维数值模拟模型对实验现象进行了理论解释。实验结果表明：触发延迟时间及其抖动随激光脉冲能量、工作电压、气压上升呈下降趋势；随SF₆-N₂混合气中SF₆体积百分含量上升呈上升趋势。欠压比大于等于90%时200kV原理型激光触发多级多通道开关触发延迟时间抖动小于1ns。     

Study of the Arc and of the Interaction between Arc and Operating Mechanism in SF6 Puffer Breakers

The article deals with studies of the arcing performance of SF6 puffer breakers at currents of up to 80 kA and voltages of up to 200 kV, using an interrupter unit fitted with viewing windows. The studies are mainly concerned with the behavior of the arc at current zero and with restrike phenomena under various conditions. In addition to measurements of the electrical variables and the pressure variation, the tests cover the use of high-speed cameras, spectroscopic diagnostic methods, and schlieren methods. The density fields and flow fields derived from the latter are used to optimize the gas flow. On the basis of the breaker data and those of its operating mechanism a method for computing the essential variables, e.g., pressure, gas flow, back pressure, and contact travel, is developed. The variation of these parameters as a function of the interrupter data for various currents and with due allowance for the interaction between the arc and the operating mechanism must be known if the breaker design is to be optimized. The method uses simplified equations for the gas flow and the arc. The relationship between the gas data (e. g., density, enthalpy, speed of sound, electrical conductivity, and dielectric strength) and the temperature is taken into account by using approximation functions. The temperature of the arc core is matched to the test results.     

回填材料膨润土对放射性气体滞留能力模拟研究

利用各种分析手段对膨润土的物理特性进行了表征 .X射线衍射分析表明钠基膨润土呈典型的六方晶胞 ,晶胞参数是 :a轴 4 .913,c轴 5 .4 0 5 ;差热分析曲线在低温区和高温区有明显的吸热峰出现 ;元素分析钠、钾离子的含量大于钙、镁离子的含量 ,在性能上表现为钠质膨润土具有较强的离子交换能力 ;显微分析表明其表面呈皱隙状 ,测定比表面积高达 2 4 .5 2m2 /g;吸水率测定表明膨胀率大 ,说明它具有密封功能 ,可有效阻滞地下水的渗入 .利用SF6示踪技术 ,通过采集不同时间段取样池样品 ,分析样品中示踪气体浓度 ,绘制取样池示踪气体浓度随时间的变化关系曲线 ,根据费克扩散定律计算扩散系数 .实验结果表明 ,随着压实膨润土密度的增大 ,示踪气体扩散系数迅速减小 ,当密度大于 1.8g/cm3 时 ,扩散系数降至 10 -9m2 /s.研究结果表明 ,膨润土性能优化是通过在膨润土中添加适量的活性炭 ,可明显改善其对气体的阻滞能力 ;增加其对放射性气体滞留能力 ;添加少量的石英砂增加其机械性能、导热性和减少蠕变性 ,将引起对气体阻滞能力的下降 .综合考虑 ,在膨润土中各添加 5 %活性炭和石英砂 ,既对气体具有较好的滞留能力 ,又具有较好的工程特性 .     

200kV/100kA低抖动环轨式多通道场畸变开关

 研制了一种200kV/100kA环轨式场畸变开关。对该开关以Ar，N₂，SF₆及SF₆/N₂，SF₆/Ar 混合气为工作介质的耐压及触发性能研究结果表明：该开关耐压最大偏差小于自击穿电击的4%；欠压比大于等于自击穿电击80%时，抖动极差小于2ns，标准方差抖动小于等于1ns；实现了多通道导通，通道数大于等于3；开关工作范围极大，在欠压比大于等于自击穿电击20%时抖动极差小于2.85ns。