基于虚拟阻抗模型的电流互感器饱和判据

提出一种虚拟阻抗模型的电流互感器饱和判别方法,它可以有效地识别区内外故障因电流互感器(TA)饱和对差动保护的影响。在电力系统的线路、母线、主设备等一些差动保护中,区外故障时,在大的短路电流作用下TA饱和容易造成保护误动。基于RL模型的短数据窗算法可以测得保护安装点的二次等效系统阻抗,它可以等效到在系统故障增量模型中虚拟一条阻抗支路。区内外故障TA饱和时,该支路虚拟阻抗会发生明显的变化。分析该阻抗在TA饱和与否情况下的变化规律,利用这种变化规律可以可靠、灵敏地判别出区内外故障TA饱和,是否闭锁差动保护,提高差动保护的可靠性。     

防止主变压器差动保护误动一例

结合一起未遂事故,详细分析了主变差动保护在桥式接线时的CT二次接线原则和差动保护原理,同时指出了某些情况下系统穿越电流也可能成为差动电流的事实,并对类似的多种危险情况提出了防范措施。     

电流互感器的二次侧引出端的组合

介绍如何组合电流互感器的二次侧引出端子。     

和应涌流导致差动保护误动原因分析

和应涌流可能引起运行变压器或发电机的差动保护误动,影响变压器与发电机的正常运行.目前,还没有防止和应涌流引起相关差动保护误动的有效措施,现场主要是靠二次谐波励磁涌流判据或三次谐波电流互感器饱和判据起到一定的闭锁作用.首先结合和应涌流的特点分析了与其相关的差动保护误动的原因主要在于电流互感器发生饱和,进一步通过多起现场误动实例与仿真,着重分析了不同类型的和应涌流发生时,电流互感器饱和检测判据所起到的闭锁作用.结果证明,虽然电流互感器饱和判据在变压器级联形式下能起到一定的闭锁作用,但在变压器并联或与多电源相连时很难起到较好的闭锁作用.     

一起主变差动保护动作的原因分析及处理

分析了由于检修工艺不到位而遗留的隐患所造成的主变引线短路故障的问题。指出检修质量对设备安全运行至关重要。     

K-means method for rough classification of R&D employees' performance evaluation

This paper proposes an approach that can roughly cluster a data set with fuzzy linguistic entries as a prior data arrangement for performance evaluation of R&D employees. The extension principles of fuzzy linguistic numbers are used to modify the K‐means method for handling the linguistic data set. We define the absolute difference of fuzzy linguistic variables as their fuzzy distance. Based on this definition, the K‐means approach can be modified slightly for clustering purposes. The performance of employees engaged in designing and R&D‐oriented jobs is possibly related to some qualitative attributes and the evaluation of such attributes for each employee has a tendency toward semantic scales. In the proposed approach, the supervisor can evaluate the performance of each employee directly with a semantic scale. The modified K‐means approach can roughly cluster their performance into different classes in advance of applying some other sophisticated processes.     

Uniform controllability of semidiscrete approximations of parabolic control systems

Controlling an approximation model of a controllable infinite dimensional linear control system does not necessarily yield a good approximation of the control needed for the continuous model. In the present paper, under the main assumptions that the discretized semigroup is uniformly analytic, and that the control operator is mildly unbounded, we prove that the semidiscrete approximation models are uniformly controllable. Moreover, we provide a computationally efficient way to compute the approximation controls. An example of application is implemented for the one- and two-dimensional heat equation with Neumann boundary control.     

微分方程解的亏量

研究函数f(g)与其小函数的亏量关系。对方程f P(z)f Q(z)f=φ(z)的任一超越解f,对于f的任一小函数c,在（φ（g)-cQ(g))g^'2-c'P(g)g'-c″ c'/g'g″≠0条件下，证明δ（c,f(g))=0.对于方程f^(n) P1(z)f^(n-1) … Pn-1(z)f=φ(z)的任一超解f，对于任一常数c，当φ(g)-cPn-1(g)≠0时，证明δ（c,f(g))=0.     

振动轮式微机械陀螺仪微分方程模型的建立

介绍了振动轮式微机械陀螺仪的工作原理，给出了振动轮式微机械陀螺仪的结构示意图和工作原理图。利用刚体转动的欧拉动力学方程，通过严格的力学分析和严密的数学验算推导了振动轮式微机械陀螺仪的基座与驱动轮之间的夹角θ和驱动轮与外框架之间的夹角ψ的关系的一个微分方程模型，并对这个微分方程数学模型进行了简化。     

三轴差速器的设计及应用

提出了一种新机构———三轴差速器 ,讲述了该机构的设计原理 ,并举例说明了其在管道机器人上的应用