架空-海缆混合高压输电线路自适应重合闸方案的研究

提出了利用比率制动差动原理判别架空-海缆混合高压输电线路的故障区段判别方法,以应用于自适应重合闸。在架空线路和海缆连接处增设电流互感器,并通过通信通道将二次电流传输至混合线路两端的保护。当混合线路发生故障,保护动作后,利用线路两端电流互感器和增设的电流互感器二次电流分别构成比率制动差动判据,进行故障区段判别。若故障发生在架空线段,开放重合闸;若故障发生在电缆段,则闭锁重合闸。PSCAD/EMTDC仿真结果表明,该故障区段识别方法能够准确可靠地判别故障区段,无死区、不受故障位置和过渡电阻的影响,可提高自动重合闸的重合成功率。     

架空-电缆混合输电线路故障定位方法综述

对国内外学者关于架空线-电力电缆混合线路故障定位的研究进行了梳理和综述。首先分析了混合线路故障定位存在的特殊问题,然后对架空-电缆混合输电线路故障定位方法的研究现状进行了总结。现有的混合线路故障定位方法有故障分析法、行波法、频率分析法以及智能法等。其中,故障分析法和行波法的准确性主要受混合线路参数不均一的影响,行波法因故障行波会在线缆连接点处发生复杂的折反射过程而导致反射波头难以识别。对于频率法,能否准确地确定故障暂态信号的固有频率值将直接影响其故障定位精度。智能法需对样本集进行离线训练,且需存储大量数据,应用起来较为困难。最后,对下一步需要开展的研究工作进行了展望。     

E-voting scheme using secret sharing and K-anonymity

E-voting maybe replaces the traditional voting scheme in the future, however, the security threat must be paid enough attention. In this paper, a novel e-voting scheme is proposed using secret sharing and k-anonymity, which not only satisfies the basic security goals such as the non-cheating, the universal verifiability, the confidentiality, and the anonymity, but also achieves the addition properties including coercion-resistance and unconditional security since the security of the proposed scheme does not rely on any computational hard problem.

     

金属矿山矿井提升机钢丝绳监测系统

介绍了金属矿山矿井提升机铜丝绳监测系统的工作原理、硬件电铸以及程序设计等.该系统可实时监测钢丝绳拉力及实时显示数据,并对待感嚣数值进行分析,若数值小于编程设定的阈值则判定为安全,若数值大于编程所设定的阈值,则判定为危险.当判定为危险后通过蜂鸣器进行报警,工作人员可以根据显示的钢丝绳的拉力数值及蜂鸣器声音来判断是否存在坠灌的危险.     

从《践土会盟》分析陈氏书院建筑木雕艺术

本文以全国重点文物保护单位的广州陈氏书院建筑木雕《践土会盟》为例，分析其制作工艺、构图特点，研究其建筑装饰艺术和蕴含的历史文化价值。     

Simulation analysis of directivity and optimization of the array of the AlN thin film PMUT array

The relatively low piezoelectric constant of the aluminum nitride piezoelectric film limits the development and application of the piezoelectric micro-machined ultrasonic transducer based on the aluminum nitride. Therefore, the directivity of the piezoelectric micro-machined ultrasonic transducer array is studied for this problem. First, the far-field sound pressure and normalized directivity function of the transducer array are calculated according to the Rayleigh principle. Furthermore, the effects of array element radius, array element spacing, array element number and operating frequency on the beam width, direction sharpness angle and sidelobe level of the array are analyzed, and the transducer array is optimized. Finally, based on the optimization results, area and filling efficiency, the final structure size of the transducer array is determined and the sound pressure distribution visually simulated. The results show that the optimized transducer array has an ideal sound pressure distribution, good directivity and sharp main lobe. The-3dB beamwidth of the main lobe is about 9 ° and the sidelobe level is about 0.228.     

Order evaluation to new elementary operation approach for MIMO multidimensional systems

A new elementary operation approach (NEOA) for Roesser model realisation of multi-input and multi-output (MIMO) multidimensional (n-D) systems has been recently proposed, which can generate a lowest possible realisation but requires trying different processing manners for various possible realisations with different structures and orders. This paper develops two kinds of novel order evaluation methods and the corresponding algorithms for the realisation procedures A and B of the NEOA, respectively, such that the best processing manner for the lowest possible realisation can be determined with much less computational complexity. These new results enable us, for the first time, to know exactly the order of a realisation before actually conducting the realisation, and thus provide us a novel and high-efficiency way to explore the lowest possible realisation problem for MIMO n-D systems. Examples are given throughout this paper to illustrate the main idea as well as effectiveness of the proposed methods.     

Phaselet-based current differential protection scheme based on transient capacitive current compensation

Time-domain compensation of capacitive current, derived from differential equation of pi-equivalent circuit of the transmission line, is introduced into a practical phaselet-based current differential protection scheme. First thoughtful analyses with comparisons are carried out for the time-domain compensation algorithm and also both the phasor compensation method and Bergeron transmission line model method. And then Electromagnetic Transients Program (EMTP) simulations are performed for the three compensation methods mentioned above. The simulation results show that this time-domain compensation method can effectively overcome shortcomings of other two methods, for example, disabling compensation for transient capacitive current, or huge computation consumption and high rate sampling which are far beyond the communication and sampling capabilities that the existing relay devices can offer. As a result phaselet algorithm with 5 ms data window can be applied to current differential protection, hence the trip time is reduced, and the selectivity and sensitivity of protection are enhanced. And also protection devices operating with lower sampling frequency and communication rate present are available for this scheme.     

基于故障分量的分相阻抗差动保护新原理

提出了一种基于故障分量的分相阻抗差动保护新原理。该原理分别提取线路两端保护安装处的故障分量进行阻抗计算，然后利用这2个阻抗之差构成阻抗差动判据。该原理无需进行采样数据同步处理，耐受电容电流和过渡电阻的影响。电流幅值差动保护判据以线路两侧的电流幅值差为动作量，幅值和为制动量，在发生电压互感器断线时，可作为阻抗差动保护判据的补充判据。仿真结果验证了该原理的正确性和有效性。