某煤矿通风机站直配线路防雷保护方法研究

针对直配线路上的旋转电动机易受雷击损坏的问题,分析了某煤矿通风机站直配线路的防雷保护现状及存在的问题,指出直配线路仅依靠避雷器的保护是不够的,旋转电动机的防雷保护应考虑主绝缘、匝间绝缘和中性点绝缘的保护要求;提出了一种安全可靠的防雷保护方法,即在直配线路母线侧避雷器端并联电容、电缆进线端串联电抗的方法,并分别从旋转电动机主绝缘、匝间绝缘和感应雷过电压防护等方面进行效果分析。仿真结果表明,该防雷保护方法能有效限制雷电侵入波的陡度和幅值。     

某煤矿通风机站直配线路防雷保护方法研究

针对直配线路上的旋转电动机易受雷击损坏的问题,分析了某煤矿通风机站直配线路的防雷保护现状及存在的问题,指出直配线路仅依靠避雷器的保护是不够的,旋转电动机的防雷保护应考虑主绝缘、匝间绝缘和中性点绝缘的保护要求;提出了一种安全可靠的防雷保护方法,即在直配线路母线侧避雷器端并联电容、电缆进线端串联电抗的方法,并分别从旋转电动机主绝缘、匝间绝缘和感应雷过电压防护等方面进行效果分析。仿真结果表明,该防雷保护方法能有效限制雷电侵入波的陡度和幅值。     

矿用隔爆型干式变压器绕组局部放电对温升的影响

为了分析矿用隔爆型干式变压器绕组绝缘层中的气隙或杂质等缺陷对绕组温升的影响,以一台连续式绕组1 000kVA/10kV矿用干式变压器作为研究对象,介绍了矿用干式变压器绕组匝间及层间绝缘结构;借助红外摄像仪对不同放电类型和不同老化温度下试样的温升特性曲线进行类比分析,得出以Nomex绝缘纸为绝缘层的干式变压器匝间放电及层间放电与温度之间的关系;运用传热学原理并结合绝缘材料特性进行数值计算及分析,得出矿用干式变压器匝间放电对绕组发热过程的影响,为变压器内部热点温度的定位及局部放电点的准确定位提供了理论依据。     

虚拟技术在变压器冲击试验中的应用研究

针对如何有效及时地发现即将投入电网运行以及正在电网中运行的变压器所存在的绝缘缺陷,减少此类故障或事故的发生,避免变压器绝缘问题所导致的灾害,基于虚拟仪器技术平台设计了一种具有集成高压示波器、高速记录仪、脉冲峰值表等专用仪器仪表功能的标准变压器冲击试验测试系统,该系统装置具有强大的数值分析和记录功能。通过对所作的冲击试验研究结果分析,该试验装置能够及时发现变压器层间、匝间和主绝缘存在的绝缘缺陷,从而可以避免因变压器绝缘缺陷所带来的危害。     

STD工业控制机在电机检测系统中的应用

STD微机控制系统是针对电机空载、短路、匝间绝缘和耐压试验而设计的电机参数自动检测系统。文中论述了系统的基本组成和有关的软件设计方法。     

发电机转子交流阻抗试验的影响因素分析与应用

发电机转子交流阻抗试验是判断转子绕组有元匝间短路的实用方法之一，试验方法简单、费用较低、灵敏度较高，多年来被广泛应用。但因其影响因素过多，在试验中容易产生数据误差，造成对绕组匝闻绝缘状况的误判，因此技术人员应对其影响因素充分认识并掌握。     

矿用干式变压器绝缘在线监测及故障诊断预警系统研制

针对传统的矿用干式变压器监测方法采用热电偶检测干式变压器内部温度而存在监测量单一,不能有效反映干式变压器绝缘实时状态的问题,提出了一种矿用干式变压器绝缘在线监测及故障诊断预警系统的设计方案,介绍了系统整体结构和故障诊断方法,建立了干式变压器匝间绝缘故障类型库。现场调试结果表明,该系统运行稳定,可实现对矿用干式变压器的远程实时监测和故障诊断预警功能。     

防止变压器瓦斯保护误动措施

近年来各电力企业时常发生由于变压器本体瓦斯保护误动而引起变压器跳闸的故障,使电力系统和变压器可靠性运行水平和电力用户供电可靠性都受到影响;同时鉴于瓦斯保护装置对反映变压器绕组匝间短路或内部绝缘电弧的故障高度灵敏性和重要作用。     

发电机转子匝间短路实时在线监测的应用

通过对发电机转子电磁特性分析。确立了匝间短路故障严重程度和有效磁场损失之间的定性对应关系。在考虑磁场饱和的条件下。建立了转子匝间短路故障诊断数学模型,通过计算有效磁场损失导致的发电机电气参数变化,特别是对无功输出的影响,建立在线识别转子匝间短路故障的判据,并采用现场匝间短路故障记录数据加以验证。     

电动机转子匝间短路故障诊断方法设计

由于电动机转子匝间短路情形较复杂,使得电动机转子匝间的短路故障诊断受到干扰,为提升电动机转子匝间短路故障诊断效果,将重复脉冲法应用于匝间短路故障的诊断中,首先对匝间短路故障点进行定位,再运用重复脉冲法对匝间短路故障进行在线监测,以判断电动机转子匝间是否存在短路故障,至此完成诊断.最后,进行测试实验,并对得出的数据进行对...     

一种实现模拟海浪回波产生的电路

无风三尺浪是大海的特点,当海上有浪时,从海面上远望,海浪由近及远是逐步减弱的,一般情况下,越近的距离海浪越大,在这种海况下,雷达天线发射的无线电波遇到海浪便会反射回来,反射回来的无线电波的功率随海浪由近及远是逐步减弱的,我们可以用一个具有模拟指数衰减曲线功能的电路模拟该功能,在电路中模拟产生了强、中、弱三种状态海浪的信号,通过模拟器面板上的波段开关可以控制海浪信号的强、中、弱三种状态,在电路中通过采用压控振荡器及速率乘法器等器件实现了以上功能。     

香港维多利亚港内船行波浪摄影测量应用研究

在香港维多利亚港对船行波浪实体进行同步陆地立体摄影测量。用解析摄影测量绘制波浪等值线图,对船行波高、船速、入/反射波的相关信息进行统计分析,进而研究了维多利亚港内常见船舶类型的兴波能力及入/反射波的运动过程。     

检测真空灭弧室内部放电的超声波传感器

研制了一种能够检测真空灭弧室内部放电的超声波的传感器。内容包括对传感器的要求,传感器的实现方案,及传感器的绝缘和抗干扰问题。实测特性和放电声发射波接收实例验证了传感器的实用性。     

Numerical analysis of homogeneous condensation in rarefaction wave in a shock tube by the space-time CESE method

A detailed numerical investigation has been carried out for the homogeneous condensation of water vapor in a non-stationary rarefaction wave generated in a shock tube. The space-time CESE method has been adopted to simulate the mutual interaction of condensation with the rarefaction wave for an extremely long time. It is found that the homogeneous condensation in the rarefaction wave has a significant influence on the flow due to the latent heat release and the continuous change of cooling rate. Three stages can be defined in this process: the initial stage which contains the onset of the condensation and the formation of the condensation shock waves in both downstream and upstream directions, the oscillating stage which is characterized as the repeat of quench and onset of condensation in the expansion fan approximately in a logarithm time manner, and the asymptotic stage which the oscillating waves are damping out with time and no apparent condensation shock wave is formed.     

Spatial direct numerical simulation of transitional boundary layer over compliant surfaces

An iterative implicit fractional step method is developed and employed for the simulation of transitional boundary layer over compliant surfaces. The three-dimensional perturbation Navier-Stokes equations are discretized by curvilinear finite volumes on a collocated grid system. A multigrid procedure is used for computations associated with the pressure-Poisson equation, while simulation is carried out by MPI-based parallel computation with domain decomposition. Results in the literature for oblique linear waves and the non-linear breakdown of a wave triad over a rigid wall are repeated to check the accuracy of the codes that had been developed. Oblique linear TS (Tollmien-Schlichting) waves over finite-length compliant membranes are generally found to coexist with CIFI (compliance induced flow instability) or FISI (flow induced surface instabilities) waves. The latter waves usually possess longer wavelengths and thus propagate at a larger oblique wave angles than the TS waves. Simulation reveals that compliant surfaces may slow down the development of secondary instabilities during the early stages of laminar-turbulent transition. However, during the later stages of fundamental wave breakdown, interactions with CIFI and edge-generated waves may increase the amplitudes of the original 2D and 3D TS waves, leading to an earlier breakdown on compliant surfaces. Linear interaction between the flow and compliant membranes has been assumed.     

Dependence of mean square slope on wave state and its application in altimeter wind speed retrieval

Mean square slope (MSS) of sea surface is a parameter describing the sea surface roughness and plays a key role in understanding the sea surface dynamics. Although MSS is influenced by many factors such as wind speed and sea surface waves, it has been traditionally parameterized by wind speed only. In this study, the surface wave impact on MSS is investigated using a collocated data set of altimeter and buoy measurements. It is found that the MSS detected by Ku-band altimeter is closely related to the wind wave components and increases with the degree of wind wave development; however, it is almost independent of the swell. The wave effect on MSS is mainly ascribed to the contribution of longer waves rather than shorter waves. An analytical spectral MSS model is proposed, and it is shown that the MSS calculated from the model agrees well with the altimeter-measured MSS when the pseudo-wave age is adjusted to the wave age corresponding to wind waves. This model is applied to derive wind speeds from altimeter data including the normalized radar cross section and the significant wave height of sea surface waves. With the collocated data set, it is shown that this new algorithm performs better than previous empirical algorithms.     

基带形成滤波器的数字实现

探讨了个人通信系统中扩频数据的基带波形形成问题，提出了用波形编码方法实现形成滤波器的方案．实验结果表明，该方案可实现理想的输出波形（如升余弦波形），具有可编程产生多种波形、工作频率范围宽等特点，可广泛用于各类数据通信系统中，实现理想的数字基带波形形成．     

一种骨架驱动的近岸涌浪动画合成方法

大面积水面及波浪的快速建模与可控动画一直是计算机图形学研究的热点问题之一,但是由于天然波浪的复杂性与不规则性,现有的波浪模拟方法无法在计算效率与真实感之间很好的权衡.本文针对此问题,以近岸涌浪为对象,研究波浪形态特征的表示与提取方法,快速生成可控的波浪动画.首先以波浪视频为数据源,利用数学形态学算法从水面视频图像中提取出涌浪骨架特征;然后根据此特征控制涌浪形状与高度,重用高度场数据生成可控的更加多样的近岸涌浪运动形态,克服了流体动画计算效率低下且难以交互控制的缺点.实验表明本文提出的方法能够以简单直观的控制方式,快速实现用户期望的变形效果.     

Influence of self- and cross-diffusion on wave train solutions of reaction-diffusion systems

The present paper deals with the wave train solutions of a generalized reaction-diffusion system. A comparative study of the nature of waves of the system in the presence of both self-diffusion and cross-diffusion has been performed. A two-species oscillatory model has also been considered as an example and analysed for its spiral wave solutions.     

一种实现水波动画的新算法

近年来，自然景物的模拟一直是计算机图形学中最具挑战性的问题之一，关于山，水，云，烟，火焰等自然景物的模拟，在计算机游戏，影视，广告等各种领域中有着广泛的用途，作为自然景物模拟的重要内容，对流水，波浪的模拟正日益引起人们的关注，该文基于小振幅波理论和细胞自动机的模型，给出了一种实现水波动画的新算法，较之于以往的做法不同的是，作者既没有去特意构造具体的波形函数，也没有去求解复杂的Navier-Stokes方程，而是基于小振幅波理论和细胞自动机的模型，采用邻域传播的思想对水波进行动态的造型，在小振幅波理论中，水波的波形近似成正弦分布，根据这一规律，可以构造出不同邻域下水波演变的细胞自动机模型，文中还采用以POINT图元为基本粒子的粒子系统，对水花效果进行了实时的模拟，为了不波和浪花逼真地结合在一起，本文运用了色彩融和的技术来完成浪花的显示，实践证明用该算法模拟水波，效果比较真实，而且在普通的PC平台上即可满足一般动画的实时需求。