雷击地线档距中央的反击性能分析

超高压输电线路高杆塔、大档距、交叉跨越、同塔多回、导线换相等应用越来越多,因雷击地线档距中央造成反击跳闸、地线断线等事故也较多,故研究输电线路档距中间反击耐雷性能有重要意义。利用PSCAD软件建立220 kV输电线路仿真模型,包括架空线路模型、杆塔的多波阻抗模型以及雷电流模型,从雷电流大小、雷击点位置和档距大小三方面,利用相交法和先导法计算分析了雷击档距中间地线时线路的反击耐雷性能,并用实例进行了验证。结果表明,校核线路雷击地线档距中央耐雷水平时,应以雷击档距中心位置为准,并考虑档距大小、杆塔塔头结构等因素影响。

耦合地线与导线档距中央空气间距确定原则的探讨

通过对事故分析,提出了耦合地线与导线档距中央空气间距确定原则的新见解,以最高气温下出现最大风速的气象条件为设计原则。实践证明此原则是合理和可行的。

输电线路档距中央绝缘配合实例分析

本文以某个具体工程为例,介绍了在输电线路设计过程中如何校验档距中央的绝缘配合,以满足线路安全运行。

1000kV单回特高压交流输电线路的绕击防雷保护

风雨在空中的漂移和空气中不均匀介质的存在使闪电的轨迹呈不规则曲线形。考虑自然闪电轨迹的随机性和雷电主先导与次先导并存现象等因素,有必要引入动态防雷保护角概念,建议特高压交流线路中地线(针)对导线的实际保护角形成的角平分线应与雷电先导的来向一致,并应计及垂直档距和水平档距的比值和风速的影响。根据杭州1962—1988年220kV新杭I线雷击统计结果,认为特高压线路防雷绕击分析应结合塔头和档内中央线路两处的防雷情况,并分别进行了防雷保护角计算与比较。

Audiovisual Archiving in Lithuanian Central State Archive

Lithuanian Central State Archive is the biggest one within the state archival service and the only state archive where audiovisual documents are stored. There are more than 800,000 units of audiovisual documents in the archive. The main laws regulating the activity of Lithuanian Central State Archive and related to audiovisual archiving are the Law on Documents and Archives of Lithuanian Republic, the Law of Cinema of Lithuanian Republic, and the Law on Copyright and Related Rights of Lithuanian Republic. There are four big collections of audiovisual documents in the Lithuanian Central State Archive--films, photo documents, sound recordings, and video recordings. The Archive＇s specialists have a large experience in the field of physical treatment and preservation of analogue audiovisual documents. Lithuanian Central State Archive digitizes audiovisual documents seeking the balance between long time preservation and nowadays access. Since May, 2010 till April 2013, Lithuanian Central State Archive implemented the project--Lithuanian documentaries on the Internet. During the project the Archives digitized and transferred to the Internet 1,000 titles of Lithuanian documentaries, created in the period 1919-1961. Lithuanian Central State Archive wants to popularize its collections, so various international projects are participated in.

档案意识漫谈

意识是人们认知世界的过程,而档案意识作为社会意识的重要组成部分,是人们对档案和档案工作这一客观事物的主观映象,也是对档案及档案工作的性质、价值的认识。档案意识在档案事业和社会发展中发挥重用作用,并反映了社会和国家的文明程度,它体现了对历史档案的重视及对客观事实的尊重。档案意识应从以下几个方面深入探讨。