防雷隔离器在雷达终端上的应用

终端系统作为雷达的重要组成部分,在受到雷电浪涌的危害时,会使得部分对外接口电路损坏,造成系统无法正常工作。为避免这一问题,文中综合利用电源、地线隔离、继电器隔离保护、压敏电阻、电压抑制二极管和信号光电隔离方法设计的防雷隔离器,有效地抑制了雷电浪涌,对终端系统对外接口电路起到了较好的保护作用。并通过工程试验,验证了该防雷设备的有效性。     

线路避雷器在110kV荔茂线60~#杆防雷中的应用

110 kV荔茂线60#杆为大跨越三联杆,A、C相杆的避雷线对B相(中相)导线的保护角为51°时,不起保护作用,使60#杆B相(中相)导线易遭受雷击,造成绝缘子串闪络。为解决60#杆的雷害问题,安装了线路避雷器。对线路避雷器雷击动作后杆塔相邻相绝缘子串的耐雷水平的计算结果表明:线路避雷器除了可防止相绝缘子串遭雷击闪络而引起线路跳闸外,还可利用其雷击动作时向导线分流部分雷电流,从而降低杆塔分流系数,将杆塔相邻相绝缘子串的耐雷水平提高了约7%。近两年的线路运行表明,采用线路避雷器是线路防雷的有效措施。     

浅谈现代化智能小区防雷应注意的几个问题

从雷电产生的危害性出发,针对现代化智能小区建筑电气施工中的防雷问题,就接地装置、引下线、屋面接闪器、等电位、均压环等几个技术环节作了论述,同时使整个建筑物形成统一的等电位系统,以实现对不同雷电的防护目的。     

基于全固态调频发射机的调频发射系统

介绍了重新构建基于意大利RVRTX5KPSS／V1全固态调频发射机调频发射系统的基本过程,简要分析了新旧调频系统之间各种实测数据。基于全固态调频发射机的调频发射系统正式投入使用后．不但大大扩展了信号场强覆盖范围,系统的指标和安全可靠性都有了大幅度提高,而且广播接收质量也获得质的飞跃,更重要的是进一步确保了信号的安全优质播出。     

柴油加氢装置循环氢压缩机振动故障原因分析

通过对410Mt／a柴油加氢装置循环氢压缩机K102振动故障原因分析,从机组振动频谱、轴心轨迹入手,详细阐述了离心式压缩机组振动的形成机理以及各种振动现象下的频谱特征,对该机组振动原因做出了较为准确的判断,快速顺利地解决了该设备故障。     

浪涌对矿井水泵房电磁环境的影响

分析了浪涌能量分布特性,据此确定了浪涌辐射骚扰测量频率最高值为1 MHz。采用频谱分析仪在煤矿井下中央水泵房对水泵电机启停过程中电磁噪声进行测量。测量和分析结果表明,浪涌对煤矿井下水泵房电磁环境有一定的影响,其产生电磁辐射不会影响人体健康,但会影响矿井下的监控、通信和控制系统正常工作。     

抽水蓄能电站上游调压室最高涌浪控制工况研究

抽水蓄能电站的水力单元通常布置两台或两台以上机组,相继甩负荷发生的概率高,有可能是上游调压室最高涌浪的控制工况。本文从调压室基本方程出发,推导任意时刻甩负荷调压室最高涌浪隐式公式。将相继甩负荷工况和先增负荷后甩负荷工况的最不利叠加时刻作为初始条件带入隐式公式中,分析得出抽水蓄能电站上游调压室最高涌浪的控制工况:即在阻抗损失系数逐渐增大的情况下,控制工况由先增后甩叠加工况变成相继甩负荷工况。该结论由实际电站的数值模拟得到了验证。     

带上游串联双调压室电站水力-调速系统稳定性的研究

上游串联双调压室可以作为超长引水隧洞水电站的重要的、可行的平压措施,本文开展了带此种平压措施的水电站水力-调速系统的稳定性的研究。首先建立了包括引水管道、调压室、水轮机、调速器、发电机等子系统的完整的水力-调速系统数学模型,推导出描述其系统动态特性的综合传递函数与自由运动方程,然后利用系统的稳定条件绘制稳定域的方式,分析了调压室面积和引水管道水流惯性对系统稳定性的影响。得到:上游串联双调压室水力-调速系统稳定域达到与只设置一个调压室系统相同稳定域时,双调压室的临界稳定断面积之和大于设置单调压室时所对应的稳定断面积;第二调压室(靠厂房)的面积越小,达到相同稳定域时两调压室的临界稳定断面积之和越大;两调压室之间管道的水流惯性占第二调压室上游段管道总水流惯性的比例越小,达到相同稳定域时,两调压室的临界稳定断面积之和与设置单调压室系统的临界稳定断面之差就越小。     

Performance of proposed thin‐wire model in finite difference time domain method

Thin‐wire approximation in the finite difference time domain (FDTD) method is important in saving computer resources and truncating central processing unit (CPU) time. Previously, thin wires were mainly realized using the true thin wire (TTW) model, in which electric field components along the wire axis are set at zero, and three methods, in which electric field components along the wire axis are also set at zero and the medium around thin wires is replaced depending on wire radius, are hereafter called the RM model. The former is the most conventional and widely used method; however, its resultant radius is 0.23Δs, supposing that the space under consideration is divided by cubic cells with a Δs of the side length of FDTD cells. The first method of the RM model can realize thin wires having a radius of about 0.15Δs under the conditions we used, in which the time interval is set at a value which is slightly less than Δt_c, e.g. 0.9999t_c, where Δt_c is defined by the Courant condition; in the case of a thin wire having a radius less than 0.15Δs, the FDTD computation suffers from numerical instability. The second method can realize a thin wire having a radius of about 10⁻⁴Δs. We need some changes in the numerical electromagnetic analysis program based on the FDTD method to employ these models. The third of the RM model, which has already been proposed by the author and in which the relative permittivity and relative permeability of four FDTD cells closest to a thin wire are replaced according to the radius of the thin wire and Δs, could realize thin wires having a radius of about 10⁻⁶Δs without changing the program and numerical instability. In this paper, the third model is extensively investigated and it is demonstrated that we can deal with a thin wire with a radius of about 10⁻⁹Δs without numerical instability. The maximum difference in the evaluation of the surge impedance of an open‐ended horizontal wire located 5 m above a perfectly conducting ground is less than 5%. We can easily use the third model even though the program, which is available, has no the specific function of thin‐wire approximation. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

基于有限元法的抽水蓄能电站调压井液压滑模设计

文中介绍了利用计算机软件对白莲河抽水蓄能电站阻抗式调压井衬砌液压滑模进行的有限元仿真分析和结构优化设计。该滑模结构经多次优化改进后,其结构达到了便于拆装,施工并节约成本的目的。