基于LabView的电流互感器励磁特性自动测量系统

电流互感器二次绕组的励磁特性是决定互感器性能的重要因素．二次绕组品质的好坏直接关系到成品的质量。本文介绍了互感器制造厂常用的电流互感器励磁特性的检测方法，并剖析了其缺点，结合虚拟仪器的概念提出了一种基于计算机技术的电流互感器励磁特性检测系统，并讨论了这种系统的原理及其硬件和软件实现。系统实现了电流互感器二次绕组励磁特性检测自动化，极大提高了生产效率；又具有开发周期短、成本低的特点，并且以实际测量结果展示此方法的优势。     

井下智能变电站电流检测系统研究

针对以电磁式电流互感器为核心的传统电流检测方式存在电流互感器安装与维护困难、占用空间大、精度低等问题,设计了一套以Rogowski线圈为传感头的井下智能变电站电流检测系统。详细介绍了积分还原电路、自适应放大电路的设计,并进行了系统稳定性分析及Rogowski线圈测试、线性度测试、频率特性测试和温度特性测试。测试结果表明,该系统具有较高的精度和良好的线性度。     

35kV电网单相接地引起电压互感器故障的原理研究

以近期在工程中发生的单相接地引起电压互感器高压熔断器熔断事件为例,分析故障后的电压波型,并根据在实验室做出的电压互感器铁心的励磁特性,计算不接地相电压互感器在电压切换过程中的冲击电流,说明间歇性单相接地可能是导致电压互感器高压熔断器熔断或电压互感器高压绕组损毁的重要因素.     

广义S变换鉴别电力变压器励磁涌流特征量的仿真研究

针对电力变压器励磁涌流所引起的变压器差动保护误动作,采用广义S变换,将变压器内部故障电流和励磁涌流从时域关系转换到频域关系。根据幅值和频率结合信息熵的概念,总结出频率信息熵和幅值信息熵两个参考指标。仿真结果验证,在电流互感器饱状态下通过频率信息熵和幅值信息熵的阈值,可准确区分变压器的内部故障电流和励磁涌流,避免变压器差动保护误动作。该研究表明了S变换在励磁涌流特征量鉴别中的有效性。     

全光纤电流互感器控制电路设计

论述了全光纤电流互感器检测和控制原理,以单片FPGA为控制核心设计了全光纤电流互感器信号检测与控制硬件电路,并对关键部件指标和检测控制方法进行了分析和讨论。结合前端光纤电流传感头搭建了全光纤电流互感器装置。经实验测试,其在额定一次电流100 A~4 000 A范围内均实现了0.2 S级测量准确度,满足电力电网对电流互感器测量准确度的要求。     

接地消弧装置导致PT铁磁谐振机理分析

随着电缆的应用和配电系统的发展,发生单相接地故障时故障点电容电流幅值增大,可能会导致故障进一步发展,采用接地消弧装置能够有效地消除电容电流。在配置有接地消弧装置的中性点不接地配电系统中,接地消弧装置动作会导致配电系统状态变化,存在导致电磁式电压互感器（PT）铁芯饱和从而产生铁磁谐振的风险。通过分析接地消弧装置动作对配电系统状态造成的影响,综合考虑铁磁谐振回路特性和PT铁芯励磁特性,对PT铁磁谐振的产生原理进行研究。提出了一种基于谐振回路特性和铁芯励磁特性的能够表达谐振非线性过程的迭代计算方法,通过MATLAB计算验证了理论分析方法和迭代计算方法的有效性。     

基于GSM技术的防分流窃电系统的设计

提出一种新的应用高压电力计量系统电能表电流线圈分流窃电故障检测方法.首先通过分析.得出电流互感器二次绕组端电压和通过电能表电流线圈的电流比值与电能表电流线圈被短接故障的关系,及其与损失电量之间的关系.其次,设计了基于GSM技术的防分流窃电系统.经实验证明该系统能及时发现分流窃电行为,从而实现了防窃电的目的.     

电子式互感器测量环节传输特性的研究

电子式互感器作为电力系统的一种新型二次设备,具有动态范围大、数据传输抗干扰能力强、测量精度高、线性性良好等特点,因而在现代电力系统及继电保护中发挥着重要的作用.在分析罗氏线圈电流互感器结构和测量原理的基础上,对其进行传感头和模拟信号处理系统的建模工作,推导了传递函数,研究了电网高次谐波及冲击电流两种电网畸变波形对电子式电流互感器传输特性的影响,并通过Simulink进行了定性、定量仿真分析,同时还分析了电子式互感器的结构参数对输入输出特性的影响.     

基于自适应正弦滤波的零序电流互感器在线检测方法

针对目前停电检测零序电流互感器极性和正确性的困难,本文提出了在线检测零序电流互感器极性和正确性方法,该方法将自适应正弦滤波应用于在线检测之中,通过保护电流互感器副边向系统注入高频电流信号,利用零序电流互感器副边的响应信号的不同相位和幅值特性,对零序电流互感器的极性和正确性进行在线检测。本文通过仿真实验,证明了该方法的可行性。     

特种电流传感器

提出的特种电流传感器是在现有电流互感器的基础上增加一种新型的小型化、高准确度的电流传感器,对其工作原理、结构特性、测试结果等进行了分析和介绍,该特种电流传感器具有非接触测量、体积小、质量轻、准确度高等特点,在供电、用电和自动控制系统领域里有较好的发展前景。     

Effective solution of certain problems of theory of schedulings of nets

Cybernetics and Systems Analysis -     

Complexity of families of learning algorithms and estimation of the nonrandomness of extraction of empirical regularities

The paper presents a general approach to the evaluation of the complexity of classes of algorithms, so-called pVCD-method. To develop this method, all the examined families of models of empiric generalization were restricted to classes implementable on computers and, wider, by examining their partially recursive representations. Within the framework of the algorithmic approach, the concept of Kolmogorov’ complexity of algorithms for the recognition of properties or the extraction of regularities is proposed. The method proposed to evaluate the nonrandomness of the extraction of empirical regularities is based on this concept.     

变电站一次设备喷涂PRTV用量的分析

对国网宁夏电力检修公司宁安运维站近2年来一次设备喷涂PRTV用量的统计数据进行分析整理,得出各类一次设备按照标准要求喷涂PRTV时的用量估算值,并针对现存作业中存在的问题,提出相应解决方案。     

Analysis of microdensitometric data in terms of probability of cleavage of DNA

Computer-aided analysis of autoradiographic films of DNA fragments is presented. The Powell least-squares procedure is used for optimization of parameters for components of complex densitometric curves. Since each densitometric spectrum may be divided for several non-overlapped blocks of bands, there is no upper limit on the number of parameters which must be optimized. Eight shapes for the component bands are utilized: symmetric and asymmetric Gauss and Cauchy functions, direct, symmetric and asymmetric product of Gauss function and inverse of Cauchy function, and log-normal function. The probability of DNA cleavage is calculated with correction for multiple cuts. The methods presented was applied to detailed analysis of densitometric spectra of a 21-bp DNA restriction fragment and allowed for direct correlation between structural microheterogeneity of DNA and the resulting cutting pattern. This method should facilitate the analysis of densitometric data from antibiotic-induced cleavage of DNA and footprinting experiments.     

联合收割机脱粒滚筒恒速智能控制器设计

研究了轴流式联合收割机的控制问题,给出了联合收割机脱粒滚筒的数学模型,介绍了基于模式识别的智能控制原理,建立了联合收割机脱粒滚筒恒速控制模型,设计了基于模式识别的智能恒速控制器.应用Matlab/Simulink进行了控制器仿真,其结果表明,将基于模式识别的智能控制应用于联合收割机脱粒滚筒的恒速控制,其过渡过程平稳、响应速度快、无超调、无振荡并且无稳态误差.     

An estimate of numbers of terms of semicycles of delay difference equations

In this paper, we study the semicycles of oscillatory solutions of the delay difference equation y_n+1 − y_n + p_ny_n-k = 0, where p_n is a sequence of nonnegative real numbers and k is a positive integer. Upper bound of numbers of terms of semicycles are determined in the case when

Our results improve and complement known results in literature.     

Complexity of approximation of 3-edge-coloring of graphs

The problem to find a 4-edge-coloring of a 3-regular graph is solvable in polynomial time but an analogous problem for 3-edge-coloring is NP-hard. To make the gap more precise, we study complexity of approximation algorithms for invariants measuring how far is a 3-regular graph from having a 3-edge-coloring. We show that it is an NP-hard problem to approximate such invariants with an error O(n1−ε), where n denotes the order of the graph and 0<ε<1 is a constant.     

Modifications of the method of variation of parameters

In spite of being a classical method for solving differential equations, the method of variation of parameters continues having a great interest in theoretical and practical applications, as in astrodynamics. In this paper we analyse this method providing some modifications and generalised theoretical results. Finally, we present an application to the determination of the ephemeris of an artificial satellite, showing the benefits of the method of variation of parameters for this kind of problems.