超声定位技术在变压器故障诊断中的应用

以某电厂500kV变压器局部放电故障为例,介绍了变压器故障找寻的过程。首先通过变压器油中溶解气体确定故障性质,然后结合变压器长时感应耐压测局部放电、超声波定位确定故障部位,最后综合变压器返厂解体检查的情况,确定了故障原因。综上所述,结合现场实践,提出了变压器现场局部放电试验的改进建议。     

三相共筒式GIS内典型绝缘缺陷局部放电试验的比较分析

气体绝缘组合电器(简称GIS)在输变电系统中的应用越来越广泛,为了更好地保证GIS在运行中的稳定性,本文研究了三相共筒式GIS在运行中常见的故障类型,根据具体的试验条件,设计了三种典型的绝缘缺陷模型,并采用超高频法(UHF)对存在故障的GIS进行了局部放电检测,分析了几种绝缘缺陷放电的典型图谱,为GIS的稳定运行和故障的及时检修提供了依据。     

同轴线管介质阻挡放电的伏安特性

采用一维流体力学模型对大气压下氦气同轴线管介质阻挡放电动力学特性进行数值模拟研究,获得了保持放电稳定性的方法。通过求解一维电子、离子、亚稳态原子连续性方程、动量方程和电流连续性方程,计算出同轴线管介质阻挡放电的放电电流和气体电压。分析讨论了不同放电模式下同轴线管介质阻挡放电的伏安特性。     

核电厂中压电气贯穿件局部放电试验的研究

介绍了三代核电站AP1000中压电气贯穿件功能和电气参数,以及IEEE 317—1983、GB13538—1992对中压电气贯穿件局部放电试验的要求,依据其试验要求和电气参数,利用局部放电测量法中的脉冲电流法设计了一套局部放电试验电路,通过对比试验提出了可降低中压电气贯穿件局部放电量的结构改进方案,对试验过程中干扰识别及抗干扰措施做了详细分析。     

针织加热织物的热电性能

为研究镀银导电长丝在积极保暖服装中应用的可行性,对导电长丝的热电稳定性进行测试,并采用镀银导电长丝和涤纶短纤纱制作了3种不同结构的针织加热织物以研究其加热效果。结果显示,镀银导电长丝的电阻随着老化时间和老化温度的增加而增大。通过提取和分析镀银导电长丝和针织加热织物表面的红外温度图像,得出其表面最高平衡温度与功率消耗密度呈正比关系,且针织加热织物的功率消耗密度与模拟服装内部的平衡温度也高度线性相关。     

灯丝电压整流滤波对微波炉效率的影响

本文研究了灯丝电压整流滤波对微波炉效率的影响,结果表明,对灯丝电压进行整流滤波后,不仅能够降低灯丝上的功率消耗,一定程度上提升磁控管的效率外,对磁控管的工作也能起到一定的稳定作用。     

500kV串补装置火花间隙放电特性试验研究

为解决500 k V串补装置火花间隙自触发问题,分析了火花间隙系统的构成及工作原理,针对主间隙的放电分散性设计了试验回路及方案,并利用某串补站退出运行的火花间隙,测量了不同间隙距离下的击穿电压,以及固定间隙距离下不同污秽的击穿电压。结果表明,火花间隙击穿电压分散性较大,交流击穿电压峰值分散区间为±7 k V;电极上存在污秽物时,间隙的击穿电压最低约降至洁净电极理论击穿电压值的65.0%。     

干式空心电抗器故障原因分析及处理措施

对干式空心电抗器的结构特点进行了介绍,对干式空心电抗器常见故障原因加以分析,对温升影响、沿面树状放电、匝间短路等几个方面进行了着重研究;并根据故障原因,对各类故障防范措施进行了探讨,从设计、材料选择、制作工艺、运行维护管理等方面给出了一些针对性建议。     

Effects of secondary electron emission coefficients on Townsend's second ionization coefficient in argon dielectric barrier discharges

One‐dimensional fluid model simulations are performed to investigate how the secondary electron emission arising from ions (γ_i), metastable atoms (γ_m), and photons (γ_p) affect Townsend's second ionization coefficient (γ′) in argon dielectric barrier discharges. Since Townsend's breakdown criterion determines the value of γ′, it is naturally affected by the discharge condition such as the reduced electric field (E/p) as well as the combination of γ_i, γ_m, and γ_p. It also depends on the other contributions from the indirect ionization processes such as cumulative ionizations or metastable–metastable collision ionizations. When the nonionic electron‐yielding processes such as the effects of γ_m, γ_p, and the indirect ionizations are considered, the calculated γ′ increases largely under the higher pd (pressure times distance) branch of the Paschen curve. Since the experimental characteristics of γ′, which decreases with E/p, can hardly be explained without such nonionic processes, the contributions of those processes can be quite important in Townsend discharges especially under high pd conditions. These processes tend not to appear and γ′ tends to converge to γ_i under the lower pd branch of the Paschen curve. The value of γ_i can possibly be estimated by using γ′ under the lower pd condition. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Experimental study on micro EDM-drilling of Ti6Al4V using helical electrode

There is a growing interest in the machining of micro-holes with high aspect-ratio in difficult-to-machine alloys for the aerospace industry. Processes based on electro discharge machining (EDM) and developed for the manufacture of both micro-electrode and micro-hole are actually used, but most of them involve micro-EDM machines. In this work, the influence of EDM parameters on material removal rate, electrode wear, machining time and micro-hole quality when machining Ti6Al4V is studied. Due to an inefficient removal of debris when increasing hole depth, a new strategy based on the use of helical-shaped electrodes has been proposed. The influence of helix angle and flute depth with respect to process performance has been addressed. Main results include 37% reduction in machining times (hole diameter 800 μm) when using electrode helix angle of 45° and flute-depth of 50 μm, and an additional 19% with flute-depth of 150 μm. Holes of 661 μm diameter and as much as 6.81 mm depth, which yields in aspect ratio of 10:1, have successfully been machined in Ti6Al4V.