A novel fast distance relay for series compensated transmission lines

This paper presents a fast distance relay for series compensated transmission lines based on the R–L differential-equation algorithm using the theory of equal transfer process of transmission lines. The measuring distances based on the proposed algorithm can fast approach the actual value of fault distance when a fault occurs in front of the series capacitor. When a fault occurs behind of the series capacitor, the fault loop, including the series capacitor, does not match the R–L transmission line model, so the measuring distances fluctuate severely. Based on this, the relative position of the fault with respect to the series capacitor can be judged effectively according to the fluctuation range of the measuring distances, and the accurate fault location can be obtained fast. A variety of PSCAD/EMTDC simulation tests show that the new relay has fast operating speed and high accuracy when applied to the long series compensated transmission lines.     

探针馈电圆柱共形微带天线阻抗特性的FDTD法分析

将圆柱坐标系下非分裂式理想匹配层吸收边界条件(UPML)引入到圆柱共形微带天线的全波分析中，并给出了其中的场量迭代方程，明显地减小了计算空间，简化了编程；提出了圆柱坐标系下考虑有限尺寸探针半径的新算法，使得计算结果更加精确；应用GPOF方法预估了时域晚时响应，使计算时间减少了70％～90％。本文给出的模型能够对任意多层圆柱共形结构的微带天线进行计算，因此对此类天线的CAD设计具有实际意义。     

一种宽带矢量调制器的设计及其应用

矢量调制器是一种可以同时控制微波信号幅度和相位的器件。本文介绍了一种基于新型微带定向耦合器的宽带矢量调制器。新的耦合器结构克服了传统微带耦合器耦合度低、方向性差的问题,也不需要Lange耦合器复杂的加工工艺,在平衡放大器、移相器和衰减器等场合具有广泛的应用。其次,研究了用串联电感对衰减器中PIN二极管的寄生参数进行补偿的一种简单方法,以改善衰减器衰减量变化时的相位性能。该方法原理简单,可在一定带宽内替代复杂的平衡结构,并给出相近的性能。最后给出了矢量调制器的测试结果和它在自适应天线阵等实际系统中的应用情况,并讨论了用于提高载波和边带抑制、满足高精度要求的校准方法。     

大气状态下AFM阳极氧化加工Si的研究

Si纳米氧化线是构筑基于Si的纳米器件的基础。通过AFM针尖诱导阳极氧化加工的n型Si(100)的实验得到凸出的n型Si(100)氧化物高度和偏置电压成线性关系,与针尖扫描速度成负对数关系,并在前人的基础上深化了AFM针尖诱导氧化加工的机理和理论模型,得到了合适的加工条件为偏压8 V和扫描速度1μm/s。     

全球宽带接入市场发展分析分析

通过对目前宽带线路数最多的10个国家和地区、2003年上半年新增线路最多的10个国家、全球宽带业务普及率最高的10个国家和地区、部分运营商住宅DSL业务的第一年费用以及2000～2002年全球入门级住宅DSL业务价格的发展趋势等图表的分析,阐明了全球宽带接入市场的发展状况,指出了其市场规模继续扩大、经济发达国家宽带线路增长速度较快、普及率的差距逐渐缩小以及业务价格趋于稳定等特点.     

平行线束法的仿射研究

用 3 个仿射图的投射方向构成 1 个仿射坐标系,同时也构成 1 个三棱锥,在此仿射坐标系中用球面三角重新研究由两个仿射图求第 3 个仿射图的投影作图理论 ——平行线束法。进一步还给出了由两个仿射图得到正投影的条件、由两个正投影得到第 3 个正投影的条件、以及由 V,H 两投影得到指定方向上的正投影的条件,简化了研究过程,得到了更简单的公式。     

Failure analysis of aluminum cable steel reinforced (ACSR) conductor of the transmission line crossing the Paraná River

The failure of the conductor of the 460 kV overhead transmission line located along the crossing of the Paraná River was investigated. As a result of this failure, a blackout took place in the southern states of Brazil in January of 2002, reaching approximately 67 million inhabitants. Investigation of the external aluminium layer of the ACSR conductor near the fracture showed typical static deformation marks and dynamic fretting wear tangential marks, both associated with the presence of Al₂O₃ debris. Additionally, encrusted silicon particles were observed on the external surface of the strands. The internal Al layer showed elliptical deformation marks also associated with Al₂O₃ debris. Both Al₂O₃ and Si particles are efficient abrasive material, which associated with slight relative motion of metallic surfaces (clamp/strand and strand/strand) can promote fretting wear. Two types of fracture surface of the Al strands were identified: 45° and quasi-normal surfaces, the former being the predominant type. Delamination and particle detachment were the mechanisms of superficial degradation observed on the Al strands, indicating that the rupture of the strands occurred under a gross slip fretting regime induced by sub-conductor oscillation. Inspection of the internal surface of as-cast Al–10%Si spacer clamps revealed different stages of intense circumferential wear caused by the preferential cracking and particle detachment of the eutectic constituent of the as-cast microstructure. This intense wear reduces the clamping contact pressure, which allows higher displacement amplitude and leads to the critical fretting regime. Finally, a few suggestions are discussed to minimise the occurrence of future failures.     

线加权余量法及其在正交异性板弯曲分析中的应用

利用有限差分法对控制方程和边界条件进行半离散化,使其定义在一些离散线上,然后采用加权余量法求解。这就是本文提出的线加权余量法,也可称之为有限差分-加权余量分维耦合法。文中以正交各向异性薄板弯曲平衡问题为例推导了有关具体算式,给出了数值算例,说明了本文方法的有效性。     

一种新型微带光子带隙结构的优化设计

本文对一种渐变尺寸的新型光子带隙结构进行了优化设计。根据优化后得出的最优结构参数 ,设计出PBG结构。实验结果证明 ,这种优化后的新型结构可以在保持阻带抑制幅度的同时减小通带内的波纹     

同杆并架双回线基于电流突变量的综合选相

相电流差突变量选相元件在单回线故障中具有良好的选相性能，但在同杆双回线跨线故障中可能误选相。利用六序故障分量的分析方法，分析了相电流突变量在同杆双回线跨线故障中的幅值和相位特征，给出了其相位比相方程。在此基础上，提出了一种运用测量阻抗和方向元件相结合的综合选相方法，并给出了选相流程图。仿真结果表明，在双回线简单故障和跨线故障时，基于单回线单端电气量的同杆并架双回线综合选相方法具有较理想的选相性能。