Aging of cellulose at transformer service temperatures. Part 2. Influence of moisture and temperature on degree of polymerization and formation of furanic compounds in free-breathing systems

This paper examines the influence of moisture and temperature on the degree of polymerization (DP) and furanic compounds. At normal service temperatures, the average moisture content in the solid insulation of transformers has a much stronger influence on the development of furanic compounds and degradation of the insulation than temperature itself. The influence of the initial moisture in the solid insulation on aging under normal transformer service temperatures of 75, 85, and 95 /spl deg/C has been investigated experimentally. Wet transformers have usually higher levels of furans, inferior oil properties, and lower DP values of paper than dry ones under similar service conditions. The development of furan concentration and moisture content are very important aging indicators for the evaluation and life assessment of transformer in service. Further work is necessary to combine these important aging characteristics into a valuable tool for the assessment of a large aging transformer population.     

断路器检修技术讲座 第一讲 断路器的结构与检修

断路器是城市电网开关设备中最重要的一个整机元件 ,在电网中起控制和保护作用 ,其性能好坏及可靠程度直接影响电网的安全可靠运行。为此 ,本利特请作者撰写《断路器检修》技术讲座 ,供从事断路器安装、运行及检修人员参考。本讲座共分六讲 ,分别是 :第一讲 :断路器的结构与检修 ;第二讲 :油断路器检修技术 ;第三讲 :操动机构结构及工作原理 ;第四讲 :操动机构检修调试要点 ;第五讲 :SF6 断路器和真空断路器的维修要点 ;第六讲 :断路器常见故障及可能原因分析。     

Simulating tornado-like enhancement of heat transfer for low-velocity motion of air in a rectangular channel with cavities. Part 1: Selection and justification of calculation methods

Existing experimental data on the subject are briefly analyzed and the main objectives of calculation studies on the problem area are determined. Details of a calculation procedure are described, the choice of Menter’s shear stress transfer model is substantiated, and results are presented from testing a multiblock approach for numerically simulating hydrodynamics and heat transfer in low-velocity near-wall airflows.     

影响贮氢电极性能因素的研究(Ⅰ)——电极制作条件和电解液浓度及添加物的影响

贮氢电极的制片压力增大,其快速放电能力增强,放电容量随循环次数增加衰减速度减慢;电极中TAB(聚四氟乙烯化的乙炔黑)含量增加,放电容量虽略有增大,但电荷保持能力明显下降,随着电解液浓度的增加,电极放电容量增大、充电效率提高、快速放电能力增强,自放电率降低,但6mol·L~(-1)以上电极性能变化不明显,说明电解液浓度至少要为6mol.L~(-1);在电解液中添加少量的PdCl_2,可使电极活化次数减少,放电电位显著提高,并对电极的交流阻抗图谱和循环伏安曲线有较大影响.     

基于双门槛值的变压器Hausdorff距离快速保护新判据

传统变压器差动保护一般采用傅里叶变换提取变压器两侧差流的基波分量,无法识别变压器内部轻微匝间故障。受数据窗长度的影响,保护通常至少需要半个周波才能出口动作,且在外部故障导致电流互感器(CT)饱和时可能出现保护误动。为解决上述问题,提出了一种基于Hausdorff距离的变压器保护新判据,通过对比变压器高低压侧电流波形的相似度,以达到快速识别区内外故障的效果。理论分析表明该判据的数据窗长度可以任意选取,有利于提升保护动作速度,同时双整定门槛值既保证了严重区内故障情况下保护能够快速跳闸又保证了区外故障伴随CT饱和工况下保护准确不动作。最后基于PSCAD/EMTDC对所提判据的有效性进行仿真验证。结果表明,所提判据能快速动作,动作时间可低至5.5 ms,即使发生0.5%的轻微匝间故障,保护也能在故障后一周波内跳闸,且具有较强的抗CT饱和性能。     

Takahiro Jibiki,Wataru Fujii,Yasuhiro Tanaka,Development of connection systems for wind power generating plant to electric power network: Experiment at the Tomamae Winvilla power plant,IEEJ Transactions on Electrical and Electronic Engineering (2007)2(1)3‐7

The original article to which this erratum refers was published in the IEEJ Transactions on Electrical and Electronic Engineering IEEJ Trans Elec Electron Eng(2007) 2(1) 3