电极烧蚀对密闭容器内空气故障电弧的影响

文中基于磁流体动力学理论(MHD)建立了密闭容器内空气故障电弧的二维数学模型,研究了铜电极烧蚀金属蒸汽对故障电弧的影响。在充分考虑由电极烧蚀引起的熔化、蒸发及化学反应等不同能量传递过程的基础上,通过求解质量、动量、能量、电磁场守恒方程以及金属蒸汽浓度方程描述故障电弧内部的流体动力学和电磁场耦合过程。计算获得了电弧等离子体的温度,压力和铜蒸汽浓度分布。比较分析了考虑和不考虑电极烧蚀情况下的计算结果,研究表明电极烧蚀铜蒸汽对压力上升的影响很小,这主要归因于内部能量平衡的变化。此外,电弧电压对铜蒸汽的存在也不敏感。压力上升、电极烧蚀质量和电弧电压的仿真结果和实验结果相一致,验证了故障电弧仿真模型的有效性。     

Numerical Study on Arc Plasma Behavior During Arc Commutation Process in Direct Current Circuit Breaker

This paper focuses on the numerical investigation of arc plasma behavior during arc commutation process in a medium-voltage direct current circuit breaker(DCCB) contact system.A three-dimensional magneto-hydrodynamic(MHD) model of air arc plasma in the contact system of a DCCB is developed,based on commercial software FLUENT.Coupled electromagnetic and gas dynamic interactions are considered as usual,and a thin layer of nonlinear electrical resistance elements is used to represent the voltage drop of plasma sheath and the formation of new arc root.The distributions of pressure,temperature,gas flow and current density of arc plasma in arc region are calculated.The simulation results indicate that the pressure distribution related to the contact system has a strong effect on the arc commutation process,arising from the change of electrical conductivity in the arc root region.In DCCB contact system,the pressure of arc root region will be concentrated and higher if the space above the moving contact is enclosed,which is not good for arc root commutation.However,when the region is opened,the pressure distribution would be lower and more evenly,which is favorable for the arc root commutation.     

超高压GIS剩余寿命评估方法综述

探讨了目前国内外在GIS状态监测技术、剩余寿命评估方法等方面的研究现状,指出现有技术在GIS剩余寿命评估方面的缺陷,提出了超高压GIS剩余寿命评估方法的总体构想及发展趋势.     

Electrode Evaporation Effects on Air Arc Behavior

A numerical study of the effects of copper and silver vapours on the air arc behavior is performed. The commercial software FLUENT is adapted and modified to develop a twodimensional magneto-hydrodynamic （MHD） models of arc with the thermodynamic properties and transport coefficients, net emission coefficient for the radiation model of 99% ai-1% Cu, 99% air-1% Ag, and pure air, respectively. The simulation result demonstrates that vaporization of the electrode material may cool the arc center region and reduce the arc velocity. The effects of Ag vapour are stronger compared to those of Cu vapour.     

空气直流断路器开断特性试验研究

针对空气直流断路器,利用2 kV/30 kA直流断流冲击试验电路,以及高速摄影仪等,对空气直流断路器的分断过程进行了研究,获得了大量的试验数据。基于相关研究工作,研制了1 800 V轨道交通用大容量空气直流断路器。     

高压直流金属回路转换开关中自激振荡开断电流的数值仿真分析（英文）

This paper presents a numerical study of the current self-excited oscillations during the opening of high voltage direct current(HVDC) metallic return transfer breaker(MRTB).The switching arc is simulated using the magneto-hydrodynamics(MHD) theory coupled with the electric circuit variation.The simulation is proved accurate in simulating the current oscillation and the commutation process in MRTB by the good agreement between the calculated results and the experimental results,which are obtained on a MRTB prototype designed to break about 5 kA of DC current.Both kinds of the results show that the current oscillation starts at about 16.5 ms and the total arc time is about 24 ms with a commutation capacitor bank of 72 μF and an inductor of 173 μH.With a further analyze on how circuit parameters influence arc current oscillations,this study helps to improve the current interruption capability of MRTB.     

Q-shift复小波的一种新型构造方法及其在图像去噪中的应用

为了提高复小波变换的效率,本文提出了一种设计Q-shift复小波滤波器的新方法。与目前采用多相位矩阵的晶格分解结构得到正交小波的方法不同的是,这里从更为一般的完全重构滤波器组出发寻求满足特定要求的正交小波。不但可以构造出系数更为简单、运算更加方便的小波,而且可以实现任意精度的复小波变换。该方法的可拓展性好,可以很方便的添加如高阶消失矩等限制并简化设计过程。以普遍采用的Q-shift10/10小波为例,利用本文构造的正交小波可将复小波变换中的乘法运算降低到原来的1/3,而加法基本相当,且小波的频率选择性质更好。将其用于图像去噪的实验表明,采用本文构造的小波可以显著提高处理速度并得到更高的峰值信噪比(PSNR)。     

单星观测弹道估计的一种新方法

研究单颗卫星利用星栽红外传感器的到达角测量，在具有先验信息条件下，对弹道主动段参数进行估计的问题，提出了一种新的射向平面匹配的建模方法，该方法克服了以往算法模型病态的情况，理论分析和仿真计算结果表明了该算法的有效性。     

基于LLE方法的本征维数估计

基于局部线性嵌入(LLE)方法所确定的数据集的拓扑结构和高维数据空间的距离特性,提出了自逼近度和可分离度的概念,然后利用二者构建了一种新的本征维数估计方法.这种估计方法揭示了LLE降维过程中涉及的数据维数与邻域大小的选取之间的内在关联.最后,通过与主成分分析(PCA)进行实例对比,说明这种方法更加合理,更能反映数据集的本征特性.