聚酰亚胺/导电炭黑抗静电复合薄膜的性能研究

采用原位聚合法制备了聚酰亚胺/导电炭黑(PI/ECB)抗静电复合薄膜,并探讨了复合薄膜的结构、微观形貌以及导电炭黑用量对其表面电阻率、热性能和力学性能的影响。结果表明:复合薄膜亚胺化完全,热性能得到提高;炭黑的质量分数为4%时,复合薄膜表面电阻率的数量级为108,达到抗静电的最佳要求。     

氧化锌压敏电阻多片并联方法及性能分析1

MOV(金属氧化锌压敏电阻)常以多片并联的形式应用于限压型SPD(电涌保护器)中,由于其性能的优劣直接影响器件的整体保护效果,遂对MOV多片并联方法及性能进行分析,通过并联后MOV电气特性的理论与试验分析,得出MOV产生电流偏差IL的主因是由于U_(1mA)和R_d的不一致性。同时基于ATP-EMTP(电磁暂态分析软件),考虑在大电流作用下MOV的响应特性和全电流区的伏安特性,并构建电路模型,利用2 ns上升速率的方波回路和8/20μs脉冲电流发生回路进行实测,仿真MOV在不同片数下的残压与通流特性,得到多片并联后MOV的特性参数变化趋势,得出MOV 5片并联其效果相对最佳。     

Common mode voltage reduction of quasi‐Z source indirect matrix converter

Quasi‐Z source indirect matrix converter (IMC) combines both advantages of conventional IMC and quasi‐Z source inverter, for example, no direct current (DC) link capacitor, compact all‐silicon power converter, bidirectional power flow, input power factor controllable, and high voltage gain; moreover, it does not require additional input filter, because continuous quasi‐Z source network integrates LC filter function. However, there is no literature to disclose common mode voltage (CMV) issue of quasi‐Z source IMC. In this paper, for the first time, the CMV issue and reduction of quasi‐Z source IMC are investigated. Firstly, the CMV of quasi‐Z source IMC is analyzed when using current typical modulation method, which follows the brief introduction of topology and modulation method for quasi‐Z source IMC, and the factors that affect the CMV are figured out; Secondly, referring to the CMV reduction methods of conventional IMC, two solutions named as Methods I and II to reduce the CMV for quasi‐Z source IMC are developed, which are achieved in the inverter stage; the third CMV reduction method is proposed in the rectifier stage through redefining the six sectors of the rectifier stage, which can implement zero current commutation. Experimental bench is built to test three approaches for reducing the CMV of quasi‐Z source IMC. Comparative evaluation is carried out between three methods and conventional modulation method. Experimental results verify that three methods can significantly reduce the CMV of quasi‐Z source IMC, with the CMV peak value reduction of 42%, but they present different features in terms of input and output current THDs, switching loss, CMV root mean square (RMS) value, modulation index limitation, and so on. Copyright © 2015 John Wiley & Sons, Ltd.     

500kV开关站构架改造工程的设计与施工

葛洲坝水力发电厂开关站 ,5 0 0kV构架的改造工程系华中电网的重大技术改造项目 ,历时 5年 ,在不影响开关站安全运行的情况下 ,克服设计和施工现场的重重困扰 ,最终完成了构架柱加固、端撑及构架梁的改造 ,消除了构架结构的重大安全隐患 ,保证开关站安全稳定运行。     

基于电流量的断路器失灵保护闭锁新原理

随着电网的日益坚强,电源容量不断增加,母线背后阻抗不断减小,越来越多的长线路末端发生故障时,母线电压下降不明显,容易出现断路器失灵保护电压闭锁元件定值灵敏度不足的问题,进而导致断路器失灵保护拒动。在分析现有解决方案的基础上,提出了一种新型的基于电流量的失灵保护闭锁方案。利用故障后失灵支路电流情况及其占母线上所有连接支路的比率关系,开放该支路的失灵闭锁元件。RTDS仿真验证结果表明,该方案能有效解决工程实际问题。     

基于LabVIEW的望远镜故障诊断与监测系统

目前大多数大型光电设备中不具备在线故障诊断与监测系统,研发出一套基于LabVIEW的大望远镜的故障诊断与监测系统。此系统通过一个标准化采集存储模块,通过外接不同传感器,可实现对大望远镜中转台位置、速度、加速度、跟踪误差的实时测量、采集、存储、显示及分析,可实现对电压、电流、气压、温度、湿度等电气及环境的在线监测,可监测各分系统运行状态及限位状态,判断故障源位置,进而实现大型望远镜的调试、运行时在线监测与控制,便于设备故障提前预防及快速事后维护。另外此系统易扩展,为改进与完善该系统提供了丰富的接口。     

基于模糊和证据理论的变压器本体绝缘状态评估方法

对电力设备运行状态进行准确可靠的评估是实施电力系统状态检修的前提和基础。以500 kV油浸式变压器为研究对象,构建了基于模糊和证据理论的变压器本体状态评估模型。选取预防性试验中具有代表性的参数为状态评估的指标,参考评价指标的出厂值和越限值进行指标归一化,利用模糊评判方法确定各个指标相对于不同状态评估等级的隶属度。将这些指标分为油中溶解气体、油化试验和电气试验三个子证据体,利用证据理论对三个子证据体进行信息合成,进而对变压器本体的运行状态进行评估。通过对某台500 kV变压器数据的实例分析验证了该评估模型应用于变压器本体状态评估中的有效性。该评估模型思路清晰,不需要大量的历史数据,为变压器状态评估提供了一种新方法。     

含有源功率解耦的单相H桥逆变器综合可靠性评估

为抑制单相H桥变换器系统中直流侧低频纹波,近年来出现了许多功率解耦方法减小或消除DCLink电容,延长DC-Link寿命,提高其可靠性。然而,由于有源功率解耦引入了额外器件,且原有器件的应力也有所改变,因此,有必要对变换器级的可靠性进行综合评估。基于2 k W的单相H桥逆变器,通过器件级的电-热应力模型、寿命模型、Weibull分布得到器件级可靠性,并基于器件级可靠性,通过可靠性框图(RBD)得到变换器级可靠性,与传统无源解耦逆变器相比较,综合评估带两种不同有源功率解耦的单相H桥逆变器可靠性。     

湖北电网GIS常见故障分析及诊断实例

本文结合湖北电网GIS维护中的故障实例,总结了GIS常见故障。以江陵换流站GIS故障诊断为例,讨论了超声波局放带电检测分析的实例。本文可作为GIS设备运行维护的参考。     

Effect of different doping methods on microstructure and photo-catalytic activity of Ag2O–TiO2 nanofibers

Ag⁺ doping TiO₂ nanofibers were prepared by in-situ and immersion methods (named as SI-TiO₂ and IM-TiO₂ nanofibers, respectively). This paper assesses the effects of the two different doping methods on the material properties. Results show that the two kinds of nanofibers with the diameter of about 20 nm are micron-sized length, and covered by nano-balls of Ag₂O with the diameter of 2–5 nm. Compared to IM-TiO₂ nanofibers, the SI-TiO₂ nanofibers have fewer Ag₂O particles. Thus, the photo-catalytic activity of IM-TiO₂ nanofibers is higher than SI-TiO₂ nanofibers, which is also proved in photo-catalysis experiment (the degradation ratio of IM-TiO₂ catalyst is 100%, and the degradation ratio of SI-TiO₂ catalyst is 95%).