表面粗糙度对变电站绝缘子冲击闪络特性的影响

为了研究表面粗糙度对绝缘子闪络特性的影响,使用了不同目数的砂纸对绝缘子表面进行均匀打磨,并利用激光共聚焦显微镜对绝缘子表面粗糙度进行了量化处理.利用陡前沿冲击试验装置产生标准雷电冲击,并对不同粗糙度的绝缘子施加正负标准雷电波,观察了在不同极性的标准雷电波的作用下绝缘子沿面闪络电压和表面粗糙度的关系,并从实验得出,随着绝缘子表面粗糙度增大,绝缘子50％闪络电压逐渐降低,在正、负极性的标准雷电波下,新绝缘子即未经过砂纸打磨的绝缘子的平均50％击穿电压最高,分别为424.9,429.1 kV,各个粗糙度下的绝缘子的闪络电压与未打磨的绝缘子的闪络电压的比值在半对数坐标系下与粗糙度呈线性关系.     

Influence of channel‐deposition conditions and gate insulators on performance and stability of top‐gate IGZO transparent thin‐film transistors

Abstract— Amorphous‐oxide‐semiconductor thin‐film transistors (TFTs) have gained wide attention in recent years due to their many merits. In this paper, a series of top‐gate transparent thin‐film transistors (TFTs) based on amorphous‐indium—gallium—zinc—oxide (a‐IGZO) semiconductors have been fabricated and investigated. Specifically, low‐temperature SiNx and SiOx were used as the gate insulator and different Ar/O² gas‐flow ratios were used for a‐IGZO channel deposition to study the influences of gate insulators and channel‐deposition conditions. In addition to the investigation of device performance, the stability of these TFTs was also examined by applying constant‐current stressing. It was found that a high mobility of 30‐45 cm²/V‐sec and small threshold‐voltage shift in constant‐current stressing can be achieved using SiNx with suitable hydrogen‐content stoichiometry as the gate insulator and the carefully adjusted Ar/O² flow ratio for channel deposition. These results may be associated with hydrogen incorporation into the channel, the lower defect trap density, and the better water/oxygen barrier properties (impermeability) of the low‐temperature SiNx.     

绝缘子泄漏电流值预测方法综述

介绍了目前国内外绝缘子泄漏电流值预测的三种方法。分析后指出,目前预测方法存在预测机理不清楚、预测模型引入的属性不精确、预测模型的历史数据库数量大、维数高,信息挖掘困难等问题。针对这些问题提出了改进建议:预测方法机理应清楚明了,尽量实现可视化;应使用一种高效的方法对数据库中的数据进行处理,实现规则的有效提取;可将预测系统和在线监测系统结合起来,将在线监测系统测得的泄漏电流及其他环境参数作为预测系统的历史数据库,提出了未来预测方法的发展方向。     

绝缘子人工污秽闪络电压变异系数的统计分析

掌握绝缘子污闪试验数据的分散性对于绝缘子选择和设计具有重要意义。对同一污秽条件下、同一绝缘子污闪电压的变异系数及置信上限进行了统计分析;对不同污秽条件下、不同绝缘子的污闪电压变异系数的分布规律及统计量进行了分析。结果表明:采用均匀升压法得到的绝缘子污闪电压变异系数置信上限的最大值为0.130;采用均匀升压法得到的绝缘子污秽闪络电压的变异系数近似服从正态分布,期望值为5.32%,其95%置信区间的上限为5.61%,与采用升降法得到的污秽闪络电压变异系数的期望值基本一致。     

基于PIC法SF_6/N_2混合气体中绝缘子沿面放电特性研究

利用等离子体运动学方程,通过粒子网格法(PIC)对SF6/N2混合气体中绝缘子沿面放电过程进行仿真,研究其局部放电机理。通过二维泊松方程,应用有限元(FEM)方法求解电场,采用蛙跳格式(leap-frog)跟踪粒子的运动。采用蒙特卡罗碰撞模型模拟粒子的碰撞过程,实现二维环境下SF6/N2混合气体放电过程动态仿真。模拟过程中考虑了电子与SF6、N2中性粒子的电离、吸附、复合以及光电离等过程。通过模拟展现了带电粒子受力积聚到绝缘子表面发展过程,对研究绝缘子表面电荷的积聚机理及其对SF6/N2混合气体中绝缘子沿面放电发展的影响具有重要意义。     

Electrical and structural characteristics of oxides grown from polycrystalline silicon

A comparative study of dielectric properties of polysilicon oxide with silicon dioxide, grown on single crystal silicon, shows that the former is more conducting due to the presence of asperites at polysilicon/SiO₂ interface. This paper also reports attempts made to improve the electrical properties of polysilicon oxide by investigating the effects of oxidation temperature, polysilicon deposition temperature and doping on current field characteristics of polyoxide. Higher doping and higher oxidation temperature yield smoother interface with higher breakdown voltages and lower leakage currents. Surface morphology of polyoxide under different process conditions is also studied.     

Low voltage ZnO thin-film transistors with Ti-substituted BZN gate insulator for flexible electronics

We report the fabrication of ZnO based thin-film transistors (TFTs) with high-k gate insulator of Ti-substituted Bi_1.5ZnNb_1.5O₇ (BZN) films. (Bi_1.5Zn_0.5)(Zn_0.4Nb_1.43Ti_0.3O₇) film deposited on Pt/Ti/SiO₂/Si substrate by pulsed laser deposition at room temperature exhibits high dielectric constant of 73 at 100 kHz, while BZN film shows much lower dielectric constant of 50, respectively. The increasing dielectric constant with increasing Ti substitution can be attributed to the presence of a highly polarizable TiO₆ octahedra and its strong correlation with the NbO₆ octahedra. All room temperature processed ZnO based TFTs using Ti-substituted BZN gate insulator exhibited filed effect mobility of 0.75 cm²/Vs and low voltage device performance less than 2.5 V.     

劣化复合绝缘子闪络特性研究

复合绝缘子由于其质量轻体积小、机械性能好、抗污能力强、安装方便的特点而被大范围使用,但由于复合绝缘子伞裙和芯棒材料在使用中容易产生劣化,劣化后的复合绝缘子电气性能将会降低,其自然闪络及污秽闪络特性有待研究。选取的样品为运行5~7年的220 kV复合绝缘子,进行了劣化复合绝缘子的自然状态污闪试验和人工污秽闪络试验。研究发现,不同劣化程度的复合绝缘子在自然状态下的闪络特性差距较大,且随着劣化程度的降低,闪络电压呈现增加的趋势。闪络电压最高的样品为最低样品闪络电压的3.956 7倍。对于6支绝缘子试品,其低压端试验样品污闪电压明显低于高压端试验样品,低33%~64%。对于不同劣化程度的复合绝缘子,其闪络电压均随着SDD的增加而降低,且污秽对轻度劣化绝缘子闪络电压影响较大。劣化复合绝缘子闪络电压和SDD之间依然满足负幂函数关系,且随着劣化程度的降低,其幂函数常数a逐渐增加。研究结果对外绝缘劣化复合绝缘子防污工作具有指导和借鉴意义。     

热机试验设备负荷及温度自动记录装置的研制

在分析热机试验标准及熟悉试验设备的基础上 ,进行了热机试验设备负荷及温度自动记录装置的研制。笔者介绍了热机试验设备负荷及温度自动记录装置的技术参数要求、基本工作原理、调试过程和实际应用效果