抗感应雷浪涌的EMI模块

介绍了用于LED灯的新型抗感应浪涌的EMI模块的结构及原理电路．讨论了其工作原理和器件参数对工作的影响，分析模块中磁集成共模电感的结构。     

Evaluation of MOSA condition using leakage current method

This paper covers the evaluation of metal-oxide surge arrester (MOSA) condition using the method based on the analysis of leakage current at the operating voltage of the network. A comparison is made between the following variants of this method: (1) the method based on harmonic analysis of the total leakage current; (2) the method based on the third order harmonic of the resistive leakage current; (3) the method of power loss; (4) the capacitive current compensation method; and (5) the method based on direct measurement of the amplitude of the resistive leakage current. For these methods the appropriate indicators are introduced for evaluating the MOSA condition. The application of these methods is analyzed depending on fluctuation and the presence of higher harmonics of the MOSA operating voltage. Calculations were conducted using the program MATLAB on a simplified equivalent circuit of a MOSA with a non-linear element modeled using the degree function. Based on the calculation results, a gradation was made for the applicability of individual indicators for evaluating the MOSA condition which indicates a special advantage for using the fundamental harmonic of the resistive component of leakage current and the fundamental harmonic of power loss.     

Numerical investigation of tip clearance effects in an axial transonic compressor

Numerical investigations of the Darmstadt transonic single stage compressor (DTC), in the Rotor1-Stator1 configuration, aimed at advancing the understanding of the effect of different rotor tip gaps and transition modelling on the blade surfaces are presented. Steady three dimensional Reynolds Averaged Navier Stokes (RANS) simulations were performed to obtain the flow fields for the different configurations at different operating conditions using the RANS-Solver TRACE. The stage geometry and the multi-block structured grid were generated by G3DMESH and a grid sensitivity analysis was conducted. For the clearance gap region, a fully gridded special H-grid was chosen. Comparisons were made between the flow characteristic at design speed, representative for a transonic flow regime, and at 65% speed, representative for a subsonic flow regime. The computations were used to analyse the flow phenomena through the tip clearance region for the different configurations and their impact on the performance of the compressor stage.     

Surge characteristics of a twisted pair

We used the method of moments (MoM), which is a numerical electromagnetic field computation method, to study the surge characteristics of twisted pair single‐phase electric power lines. The results show that wires stranded with less than several turns per meter have almost the same surge characteristics as parallel lines, but the surge impedance decreases in tens of % when the number of strands increases. To verify the simulation results, we measured the surge characteristics of a model line of twisted pair experimentally, and there is good accordance between them. It is possible to simulate the surge in twisted pair covered with polymer dielectric insulators by MoM. Moreover, we studied the surge characteristics of twisted pair which is inserted into a metal tube. According to the results, the effect of the strand is smaller than that in free space without the metal pipe. There are two propagation modes in common mode: fast surge and slow surge. Few influences of the number of strands on the surge velocity occur in the fast propagation surge, but the increase of the surge impedance and the slowdown of the propagation speed are caused by twining in the slow propagation mode. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(3): 1–9, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20737     

带引水调压室水轮机调节系统稳定性及动态品质研究

为了研究小波动过渡过程中,调压室水位波动对水力发电系统动态稳定性及调节品质的影响,从水力耦合的角度,确定了调压室水位与机组流量之间的函数关系,建立了带引水调压室的水力发电系统数学模型,并基于Simulink对系统进行仿真研究。结果表明,调压室水位波动对机组转速的主波影响较小,对机组转速的尾波影响显著;调压室时间常数及引水系统的水力阻尼是影响调压室水位波动稳定的重要因素,机组转速的主波稳定不能表明系统稳定,还必须考虑调压室水位波动稳定性。     

多机一室长廊型调压室水力过渡过程数值仿真研究

基于调压室基本方程和结构矩阵法,构建了典型的多机一室长廊型调压室—三联调压室水力过渡过程计算的恒定流模型和瞬变过程模型(简称三联模型),并基于工程实例,针对典型工况,分别采用简化模型和三联模型进行过渡过程计算。结果表明,简化模型和三联模型计算所得的蜗壳末端最大压力、机组转速最大上升率和调压室极值水位基本一致,而尾水管进口最小压力有一定的区别;采用三联模型可较好地反映恒定流状态下阻抗孔口之间的水体流动及过渡过程中尾水管进口压力的变化情况;过渡过程计算中阻抗系数取值允许一定的误差,并不会对尾水管压力和调压室水位的变化产生较大影响。     

750 kV/ 220 kV电网电磁合环操作冲击电流分析与实践

为了分析超高压电网合环操作时冲击电流的影响作用,结合新疆750 kV巴州变电站750 kV/220 kV电网合环操作实例,简化电网建模并建立冲击电流模型,分析了影响冲击电流的主要因素（电压差、相角差和总阻抗）及对应关系,进而制定合环操作方案并顺利实现电网合环。结果表明,实测冲击电流特性与理论分析结论一致,对电网合环操作实践具有重要的理论指导和经验借鉴作用。     

机组调速系统引入调压井涌浪反馈对减负荷过程的影响

鉴于长引水系统水流惯性时间系数较大,机组减负荷时,机组输出力矩无法立即响应负荷的变化,不能很好地满足电网稳定调节需求。通过BCB软件平台对带有调压井的高水头机组复杂非线性模型的减负荷过渡过程进行仿真,提出将调压井的涌浪反馈引入至机组PID调速系统的比例环节、积分环节和微分环节,对比分析减负荷后机组出力、调压井涌浪及蜗壳水压波动情况。结果表明,引入调压井的涌浪反馈至调速系统的微分环节能够加快长引水系统机组减负荷后系统的稳定。     

大型尾水调压室穹顶开挖支护力学与变形特征研究

 锦屏一级水电站尾水调压室为2个巨型圆筒状竖井,且位于2条大断层及多组节理切割的复杂高应力地质体内,球冠状顶部开挖支护困难。工程应用和理论研究均表明：开挖方式和支护参数是影响尾水调压室穹顶应力分布和变形的关键因素。基于对1#尾水调压室顶拱f14断层及煌斑岩脉,断层影响带的现场勘察研究采用力学分析、原位监测和三维数值模拟等手段,对尾水调压室围岩变形破坏机制进行深入分析,研究尾水调压室开挖过程中穹顶围岩变形和力学特征。最后,对尾水调压室的开挖、支护提出若干有益的建议,为锦屏一级水电站的动态开挖支护设计提供技术支持。     

矿井监控设备的抗干扰研究

煤矿安全监控系统是煤矿安全高效生产的重要保证,煤矿井下工作环境恶劣,弱电设备和大耗能分布广泛,特别是高频器的使用,会给监控系统带来干扰信号,因此提高矿井监控系统的抗干扰能力是实现我国煤矿安全生产最根本的发展之路。