Silicon nanorods‐based all‐dielectric waveguides with long decay‐length at the telecommunication band

We investigate subwavelength waveguides composed of silicon nanorods array in straight and nonstraight regimes deposited on a silica (SiO₂) substrate. It is shown that using all‐dielectric nanorods with high permittivity to design an all‐dielectric optical waveguide provides several advantages such as low‐dissipation coefficient and long decay length for the distributed fields. Exploiting silicon arrays in touching and nontouching arrangements, we examined the optical response of the structure to the guiding of magnetic and electric fields with transverse and longitudinal polarization modes. We studied the decay length for all propagated modes in both nanochain orientations numerically. Simulation results for straight arrays showed that the averaged decay length for the structure with dielectric particles in touching regime is 1.6 µm (for the waveguide with the length of 2.2 µm), and for the nontouching array is 2.2 µm (for the array with the length of 3.1 µm). Calculating transmission loss factors and considering decay length of the proposed waveguide, we verified the strong potential of the proposed structure to design all‐dielectric photonic devices to operate at telecommunication spectra (λ~1310 nm and 1550 nm). Also, we computed bending losses [dB] for the examined structures based on the bends degree. Copyright © 2015 John Wiley & Sons, Ltd.     

The performance of power cables with fully synthetic tapedinsulation

The testing of oriented polyethylene tape with an embossed surface design for use as oil-impregnated insulation for flexible power cables is described. The development was carried out with small samples in the form of sheets, small cylindrical samples about 1 m long, and long cables either 15 m or 100 m long. Tests with these experimental configurations included investigating: (1) breakdown stress and statistics of breakdown; (2) dielectric loss measurements; (3) design of screens; (4) design of splices; (5) mechanical problems of taping and installing cables; and (6) oil impregnation and type of oil. The results point the way to the next development steps. These are: (1) development of thinner embossed tapes to exploit the potential of the high dielectric strength inherent in synthetic taped insulation; (2) development of accessories such as splices and terminations; and (3) complete system design to avoid a dramatic increase in dielectric loss caused by oil contamination. If the integrity of the insulation homogeneity can be maintained, it appears the high voltage breakdown stresses will be adequate to permit economical operation     

中间变压器对电容式电压互感器介损测量的影响

测量电容式电压互感器的一次绕组对二次绕组及地的阻抗特性时在某种接线方式下阻抗会呈感性,这将使电容式电压互感器的介损测量产生异常结果。当阻抗呈容性时对介损测量影响较小。中详尽分析了各种不同的测量接线方式下中间变压器对电容式电压互感介损测量产生的影响,这些分析结果可以为电容式电压互感器的现场测量提供合理的测量方法及理论依据。     

光检测及放大电路的新设计

为满足光缆动态损耗测量系统宽动态范围和高灵敏度的要求,本文提出一种新的光检测及放大电路设计。单端光检测及放大电路应用广泛,结构简单,但难以抑制电路的共模噪声。新设计将光检测器和放大器通过对称结构搭建差分电路,达到了更高的光检测灵敏度和抗共模噪声性能。它充分考虑了前端电路各种噪声源,采用合理的元器件和电路设计抵消了大部分共模噪声。通过实验证明该电路提高了测量系统的灵敏度。新电路已成功应用于光功率信号系统的光电转换电路中。     

Sol-gel processed ferroelectric and multiferroic thin films for integrated devices

Abstract

Ferroelectric barium titanate and multiferroelectric bismuth ferrite thin films have been fabricated by using sol-gel processing technique. The starting materials for fabrication of were barium 2-ethyl hexanoate and titanium (IV) isoproposxide. Bismuth nitrate and ferric nitrate were the precursors for the fabrication of thin films. The as-deposited films were annealed at higher temperature for crystallization. The X-ray diffraction study on the films showed that the as-grown films were found to be amorphous that crystalized to proper phases by annealing at 550?°C in air for one hour. All the samples showed high optical transparencies in the visible frequency range. The room temperature dielectric constant and loss tangent of barium titanate thin films at 1?kHz frequency were found to be 400 and 0.01 respectively. Both the dielectric constant and loss tangent showed small dispersion in the frequency range of 0.10–1000?kHz range. The ferroelectricity in barium titanate thin films was confirmed by the presence of bell shaped capacitance-voltage (C-V) butterfly loop and saturated polarization-field (P-E) hysteresis loop. The as-grown bismuth ferrite thin films were also found to be amorphous that crystallizes after annealing at 500?°C. These films also showed high optical transparencies in the visible region. The bismuth ferrite thin film samples showed saturated hysteresis loop and magnetic polarization-magnetic field hysteresis loop as well, confirming the multiferroic nature of the samples.     

Photonic integration using asymmetric twin-waveguide (ATG) technology: part I-concepts and theory

In this first of two papers (hereinafter called Paper I), we present a universal approach for simply realizing monolithic photonic integration based on asymmetric twin-waveguide (ATG) technology. The concepts and important developments leading to ATG integration technology will be reviewed. The ATG structure consists of active and/or passive devices formed in separate, vertically displaced waveguides. Light is transferred between the waveguides via very low loss, lateral, adiabatic tapered mode transformers, allowing different optical functions to be realized in the different waveguides. The design of the adiabatic tapered mode transformer uses an algorithm based on perturbation theory. We show that the same designs can also be deduced from coupled local mode theory. Using the perturbation algorithm to design the taper coupler in an ATG based high bandwidth photodiode, a transfer efficiency of greater than 90% from the fiber waveguide to the coupling waveguide is achieved while the taper length can be reduced by 35% compared to conventional two-section linear taper couplers. The taper design algorithm is further optimized to make the adiabatic taper couplers tolerant to variations in incident light polarization, operation wavelength, and dimensional control during fabrication. Finally, we propose and design a taper that adiabatically couples light from the fundamental mode to the first-order mode. Such a taper coupler is useful in an integrated semiconductor optical amplifier/p-i-n detector circuit.     

谐波对电力电缆线路损耗的影响

介绍谐波产生的原因和基本原理,对高次谐波引起电力电缆电阻损耗、线路介质损耗和三相四线制电缆线路损耗分析,表明可以通过对电缆自身设计参数以及线路敷设方式的优化,来减小高次谐波对线路损耗的影响,为电力电缆载流量的计量提供了一定的理论参考。     

测量介质损耗的数字化过零点电压比较法

高电压设备的状态检修对提高电力系统运行的可靠性和高电压设备的维修效率十分有效，在线监测介质损耗对于高电压设备的状态检修具有重要意义。在线监测介质损耗要求精度高，抗干扰能力强，文章作者研究开发的过零点电压比较法（ZCPV法）已能够满足这一要求，在此基础上，应用数字测量和处理技术，又研究开发了性能更优越的数字化测量介质损耗的过零点电压比较法（DZCPV法）。文中介绍了DZCPV法的原理及使用该方法的介质损耗测量装置的具体设计。     

高电压大容量陶瓷电容器组开发与应用

为了防止机车驶过分相绝缘器的过电压损害机车控制系统,保证火车正常运行,常在绝缘器两端加装阻容装置,高电压大容量的电容是该装置的核心元件。本文通过选用一种高介电常数的瓷料,设计并制造了一种小体积、低介质损耗的陶瓷电容器组。该电容器包含16个并联的电容器单元,每个电容器单元由3个陶瓷电容器元件串联组成。通过合理布置电容器组的结构,在保证基本电气性能的基础上预防了环氧树脂浇注的应力集中,同时减少了环氧树脂的用量,提高了产品的环保性能。该产品具有电容量大、介质损耗小、环保无油污染的特点,并已开始工业化生产且投入相关线路的使用。     

有界波电磁脉冲模拟器参数对传播模式的影响

为了从数量上获得有界波电磁脉冲模拟器的各种参数对其工作区间内电磁波传播的影响程度,基于时域有限差分法建立了有界波电磁脉冲模拟器的数值分析模型,并利用建立的模型计算了模拟器参数对电磁场分量的相对大小和电磁波传播模式的影响。结果表明:增大工作区间的长度和宽度可使得电磁波越来越近似于横电磁波模传播,宽度影响效果尤其明显;有耗大地的介电常数基本不影响电磁波传播模;横向方向的电场分量随着有耗大地电导率的增大而逐渐增大。所以工作区间的宽度和有耗大地的电导率是影响电磁波传播模式的主要因素,这对电磁脉冲模拟器设计具有重要的指导意义。     

加Blackman-Harris窗插值算法仿真介损角测量

为了更好地将加布莱克曼-哈里斯(Blackman-Harris)窗插值谐波分析法用于介损角测量,仿真分析了该算法及其在信号频率、3次谐波、直流分量、采样频率、A/D量化位数、采样时间长度、介损角真实值、白噪声及脉冲噪声变化时计算所得介损角误差的变化。仿真结果表明,频率波动时算法误差很小且稳定;算法随3次谐波分量的增加误差有很微小的增加;算法随直流分量的增加变化不显著;算法随A/D量化位数的增加误差减少,≥10位的量化位数能满足精度要求;随采样频率的增加误差稍有下降,但趋势不明显;随采样长度增加误差减少,0.1s的采样时间长度足够;介损角误差与真实值的关系不大;随白噪声和脉冲噪声含量的减少误差减少,对白噪声和脉冲噪声信噪比约80 dB能满足要求。     

基于数字滤波的介质损耗测量积分算法

针对通常采用的测量介质损耗的方法对硬件或软件的要求过高,并且要实现高精度测量的难度问题,本文提出了一种基于数字滤波的介质损耗因数测量的积分算法.该方法通过软件方法实现测量功能,算法原理简单,能够比较容易地用MCU编程实现.对决定该算法精度的数字滤波器设计要点和移相方法进行了分析,探讨了A/D转换字长及数据采样密度对算法误差的影响.仿真研究表明,该算法具有较高的测量精度和较强的抗干扰能力,实现算法的硬件电路简单,常用的MCU器件的性能即可满足算法实现要求,具有良好的实用性.     

基于经验模态分解和正弦波参数法的介损角测量算法

将基于经验模态分解(empirical mode decomposition,EMD)的新型时空滤波方法应用于介损角的测量中。利用EMD对强噪声背景下的采样信号进行分解,根据所得到的固有模态分量的频谱特性进行选择性滤波,提取其基波分量,并结合正弦波参数法计算介损角。探讨了系统频率变化和介损角变化对测量真实值的影响。仿真结果表明该方法可明显减小计算误差,对提高数字化测量d 的精确性具有实际意义。     

基于希尔波特-黄变换的介损数字测量算法

准确提取基波电压和电流信号是检测介质损耗因素的关键。提出了一种新的介质损耗因数检测算法,采用希尔波特-黄变换(HHT)对试品电压和电流信号进行检测,通过经验模态分解法(EMD)提取信号的固有模态函数(IMF),再进行Hilbert变换,得到各自的瞬时频率,由瞬时频率进行介质损耗因数的准确检测。该算法无需同步采样,可以实时提取测量电压、电流信号的基波成分。仿真结果表明,HHT受采样数据长度、频率跟踪误差的影响较小,在非同步采样的情况下,具有良好的应用特性,能有效提高介质损耗因数检测的准确度。     

基于Prony算法-准同步序列的超低频介损测量方法

超低频介质损耗因数测量方法，由于测量信号频率低导致采样时间长，采集数据量大，且在非同步采样时，快速傅里叶变换存在频谱泄露和栅栏效应，影响对介质损耗因数的精确测量。为降低测量信号采样时间和采集数据量，以及非同步采样时频谱泄露和栅栏效应，提出一种基于Prony算法 准同步序列的超低频介损测量方法，利用Prony算法并结合据辨识方法，对采样电压信号的基波频率进行预估，通过Newton插值算法，实现对电压和电流信号的准同步插值重构，获得采样信号的准同步序列，由FFT及介损等效电路模型，对准同步序列进行求解，实现对超低频介质损耗因数的求取。在频率波动、谐波含量变化、介损角变化和不同信噪比的噪声下测量介质损耗因数。仿真结果表明，该方法在软件上实现了准同步采样，有效降低了栅栏效应和频谱泄露对介质损耗因数测量的影响，并且采样时间短，采集数据量少，测量精度高，适用于对超低频介质损耗因数的精确测量。     

解决OPGW进站安全运行问题瞰研究与实践

为解决光纤复合架空地线（OPGW）进变电站在出线构架引下区段近年来频繁发生熔损事件,严重影响通信网及电网安全运行的问题,基于理论研究结论,分析了目前OPGW进站方式存在的缺陷,创新研制出一种新型介质光缆复合架空地线（ODGW）及其架设方案,并在220kV线路中得到成功应用,其能在不需要特殊安装金具、不改变施工工艺前提下,很好地解决OPGW进站电磁兼容性及安全运行问题,并适用各电压等级输电线路,不需要特别维护,还简化了变电站构架光缆接续点施工工艺。     

基于卡尔曼滤波和加窗插值谐波分析法的介损测量方法

加窗插值的谐波分析法可减轻非同步采样对介质损耗角测量的影响,是一种非常有效的介质损耗角计算方法。但在有噪声干扰、特别是在信噪比较低的情况下,用这种方法进行介质损耗角测量时产生的误差足以掩盖真实值。为此作者提出先将信号进行卡尔曼滤波处理,再使用加窗插值的谐波分析法计算的介质损耗角测量方法。仿真结果表明,与原有算法相比,所提出的方法能明显提高测量准确度。     

基于移相和平衡测量原理的介质损耗在线测量方法

基于目前的微电流传感器设计和制造技术,利用信号移相和小电流平衡测量原理,采用单匝无源微电流传感器作为检流计,通过微型控制单元(Micro-Controlller Unit,MCU)实现了低成本高准确度的介质损耗因数在线测量方法.介绍了该方法的测量原理和实现方式,分析了该方法的理论测量精度:设计了通过电阻电容改变介质损耗角的简单实用的模拟试验电路.理论分析和试验结果表明,该介质损耗测量方法具有较高的测量准确度及稳定性.     

330kV电容式电压互感器的最新发展

对西容公司最新开发的用于330kV电力系统的电容式电压互感器进行了阐述，介绍了开发中关键问题的解决。其系列产品的成功开发使得产品具有介损小、绝缘水平高、局放小、爬距大等技术特点。     

结合频谱校正的修正理想采样频率方法用于介损角测量

提出了结合频谱校正方法和修正理想采样频率的介损角测量方法,该方法使用加Hanning窗插值的谐波分析法获得信号基波频率的准确值,然后根据获得的频率采用线性插值的方法构造符合同步采样的序列并进行DFT,进而获得信号的介损角。仿真信号的计算结果表明,该算法精确度高、实现容易,是介损角测量的一种很有推广价值的方法。