基于微波辐射理论的绝缘子污秽等值盐密/灰密检测模型

用微波辐射计测量绝缘子污秽表面亮度温度,从而可获得污秽的辐射能量特性。提出用亮度温度计算绝缘子污秽等值附盐密度(equivalent salt deposit density,ESDD)、等值附灰密度(non-soluble deposit density,NSDD)的检测模型以及盐密和灰密乘积形式的检测模型。在不同测量角度下,研究干燥(相对湿度20%)和湿润(表面形成水膜)条件下,ESDD和NSDD与天线温度的关系,同时研究天线温度与环境温度及湿度的关系,并分析湿度对模型参数的影响。结果表明:ESDD和NSDD对天线温度的影响是独立的,通过测量天线温度可以同时测定ESDD和NSDD。     

Growth of Topological Insulator Bi2Se3 Thin Films on SrTiO3 with Large Tunability in Chemical Potential

The growth of high quality, gate‐tunable topological insulator Bi₂Se₃ thin films on SrTiO₃ substrates by molecular beam epitaxy is reported in this paper. The optimized substrate preparation procedures are critical for obtaining undoped Bi₂Se₃ thin films with sufficiently low carrier densities while maintaining the strong dielectric strength of the substrates. The large tunability in chemical potential is manifested in the greatly enhanced longitudinal resistivity and the reversal of the sign of the Hall resistivity at negative back‐gate voltages. These thin films provide a convenient basis for fabrication of hybrid devices consisting of gate‐tunable topological insulators and other materials such as a superconductor and a ferromagnet.     

架空输电线路复合绝缘子老化断裂试验分析

通过对架空线路复合绝缘子常见的芯棒老化故障分析,指出早期产品材质不佳、工艺落后,加之紫外线、电场及降水等外界环境的影响,是导致绝缘子性能下降、芯棒护套破损及内部芯棒出现严重老化、强度不足、出现断裂的主要原因,并对下一步老旧绝缘子的巡视运维措施提出了建议。     

基于深度学习的红外图像中劣化绝缘子片的分割方法

红外成像作技术为绝缘子在线检测的重要手段已日趋成熟,而当前对于电气设备红外图像的分析仍依靠大多依赖人工经验,缺乏智能化。传统的红外图像中劣化绝缘子的分割方法需要复杂的图像预处理和人工提取目标特征,因而存在着泛化能力差、复杂背景下识别精度低等缺陷。基于以上问题,文中提出一种基于深度学习的红外图像中劣化绝缘子的分割方法。首先搭建实验平台,获得绝缘子串在复杂背景(有其他设备和发热源干扰)下的红外图像。为了保证红外图像的多样性,拍摄在多种污秽等级下进行,选取了多种阻值的劣化绝缘子片放置在了多种位置,并不断改变了拍摄的角度。然后构建多尺度的方法实现全卷积神经网络(FCN)的3种子模型架构：FCN-32s、FCN-16s和FCN-8s,使用随机梯度下降的训练方法对模型进行端到端的训练,最终实现了红外图像中的劣化绝缘子片的自主分割提取。通过对三种子模型训练测试对比后,得出以下结果：FCN-8s模型为劣化绝缘子片分割提取最佳模型,对于验证测试数据集像素分类准确率为89.23%。结果表明文中所描述的智能化红外劣化绝缘子片分割方法,为绝缘子和其他高压电气设备的红外在线监测诊断打下了坚实基础。     

Understanding Bulk Defects in Topological Insulators from Nuclear‐Spin Interactions

Non‐invasive local probes are needed to characterize bulk defects in binary and ternary chalcogenides. These defects contribute to the non‐ideal behavior of topological insulators. The bulk electronic properties are studied via ¹²⁵Te NMR in Bi₂Te₃, Sb₂Te₃, Bi_0.5Sb_1.5Te₃, Bi₂Te₂Se, and Bi₂Te₂S. A distribution of defects gives rise to asymmetry in the powder lineshapes. The Knight shift, line shape, and spin‐lattice relaxation are investigated in terms of how they affect carrier density, spin‐orbit coupling, and phase separation in the bulk. The present study confirms that the ordered ternary compound Bi₂Te₂Se is the best topological insulator candidate material at the present time. These results, which are in good agreement with transport and angle‐resolved photoemission spectroscopy studies, help establish the NMR probe as a valuable method to characterize the bulk properties of these materials.     

在役绝缘子失效特征与无损检测

在电网各个环境中运行的不同种类绝缘子，长期服役后都会不同程度地产生失效，导致故障事故的发生，对电网可靠性带来了极大地潜在威胁，研究绝缘子的失效特征对于指导绝缘子安全检测具有十分重要的意义。本文基于在役绝缘子种类繁多和结构复杂的特点，分析绝缘子失效特征和损伤部位，提出了利用无损检测技术检测绝缘子损伤缺陷的方法。     

220kV万义线41~#冰闪故障掉闸分析

通过分析220 kV输电线路杆塔上和绝缘子上的积雪溶化在绝缘子上形成的冰柱,用绝缘子防污能力—泄漏比距的计算方法来计算冰柱的泄漏比距,从而判断出冰柱的防污能力。同时对比分析绝缘子的湿闪电压得出冰柱在溶化时的湿闪电压,得出了绝缘子在溶雪形成冰柱时不能承受220 kV的工作电压的结论。最后针对绝缘子上冰柱的形成原理制定出相应的防范措施。     

Design and Construction of Insulation Configuration for Ultra-High-Temperature Microwave Processing of Ceramics

A multilayer insulation configuration suitable for microwave sintering of ceramics up to 2100°C was designed and tested successfully. The configuration is based on porous, granular BN/ZrO₂ fiber composite powder for packed beds and spacer cylinders. This insulation allows stable, controlled microwave sintering and can be modified to microwave process materials with different thermal, dielectric properties with improved properties.     

The Role of Adsorption and Phase Change Phenomena in the Thermophysical Characterization of Moist Porous Materials

Phase change phenomena in moist porous media with low liquid content, the typical condition of a porous body at ambient conditions and far from the contact of liquid water, are controlled by the shape of the adsorption isotherms and by the effective liquid-vapor thermodynamic condition within the pores. Usually, heat and mass transfer models are developed under the assumption of thermal and hygrometric equilibrium. This gives rise to an expression of the evaporation source that is too complex in view of the dynamic identification of thermophysical and transport properties of a porous material. In this study, the hypothesis of hygrometric equilibrium is dropped. The phase change rate is considered proportional to the amount of local nonequilibrium through an appropriate delay coefficient. This approach leads to a simple representation of the process and makes manageable the formulation of a coupled heat and mass transfer inverse problem. A comparison with a first group of experiments performed with an open-pore light insulating material (expanded perlite board) confirms the suitability of the proposed approach. However, the analysis shows that, for this material, phase change occurs not far from the hygrometric equilibrium.