期刊文献+
共找到4篇文章
< 1 >
每页显示 20 50 100
换流器保护在交流故障下的出口时序特性分析 被引量:2
1
作者 张志强 余超耘 +1 位作者 刘强 蔡泽祥 《电力系统保护与控制》 EI CSCD 北大核心 2017年第10期85-90,共6页
当交流故障的故障条件不同时,换流器保护的出口结果和出口时间均具有不确定性,针对该问题展开系统的研究。梳理了换流器区故障和换流器保护的类型,并基于实际特高压直流工程的RTDS实验结果分析了交流故障下可能动作的换流器保护及其动... 当交流故障的故障条件不同时,换流器保护的出口结果和出口时间均具有不确定性,针对该问题展开系统的研究。梳理了换流器区故障和换流器保护的类型,并基于实际特高压直流工程的RTDS实验结果分析了交流故障下可能动作的换流器保护及其动作机理。详细分析了换流器保护的故障后电气特征离散性和计时原理,指出这是导致换流器保护动作时间不确定的两个原因。进一步深入对比了交流故障下存在出口时序离散性的3种换流器保护的动作逻辑,并结合上述特高压直流工程的RTDS实验结果分析了不同故障条件下这3种保护的出口时序特性。分析结果表明,这些保护延时定值极为接近,而且可能相互闭锁,不同故障条件下三者的出口时序关系决定了不同的动作结果。 展开更多
关键词 HVDC 交流故障 换流器保护 响应特性 出口时序
下载PDF
直流保护出口时间的不确定性及其时序特性 被引量:1
2
作者 李佳曼 《广东电力》 2016年第12期85-91,共7页
针对直流保护在交流故障下动作结果不确定的问题,就直流保护在交流故障下出口时间的不确定性及其特有的出口时序特性展开研究。首先分析了直流保护的计时原理,指出直流保护计时采用累计方式导致动作出口时间不确定;然后基于实际的控制... 针对直流保护在交流故障下动作结果不确定的问题,就直流保护在交流故障下出口时间的不确定性及其特有的出口时序特性展开研究。首先分析了直流保护的计时原理,指出直流保护计时采用累计方式导致动作出口时间不确定;然后基于实际的控制保护模型与参数的PSCAD/EMTDC仿真平台,通过设置不同故障条件,研究不同故障、不同故障角对直流保护出口时间的影响,结果表明直流保护出口时间在不同故障和不同故障角下具有不确定性;最后分析了直流保护在交流故障下的出口时序特性,结果表明不同直流保护的出口时序配合决定了最后保护动作的结果。 展开更多
关键词 直流保护 交流故障 出口时间 不确定性 出口时序
下载PDF
Wet-Dry Runoff Correlation in Western Route of South-to-North Water Diversion Project,China 被引量:2
3
作者 HUANG Xiao-rong ZHAO Jing-wei YANG Peng-peng 《Journal of Mountain Science》 SCIE CSCD 2015年第3期592-603,共12页
The Western Route of the South-to-North Water Diversion Project is an important trans-basin diversion project to transfer water from the upstream Yangtze River and its tributaries (water-exporting area), to the upst... The Western Route of the South-to-North Water Diversion Project is an important trans-basin diversion project to transfer water from the upstream Yangtze River and its tributaries (water-exporting area), to the upstream of the Yellow River (water- importing area). The long-term hydrologieal data from 14 stream gauging stations in the Western Route area and techniques including the pre-whitening approach, non-parametric test, Bayes, law, variance analysis extrapolation, and Wavelet Analysis are applied to identify the streamflow eharacteristics and trends, streamflow time series cross-correlations, wetness-dryness encountering probability, and periodicities that occurred over the last 50 years. The results show that the water-exporting area, water- importing area, and the streteh downstream of the water-exporting have synehronization in high-low flow relationship, whereas they display non- synchronization in long-term evolution. This corresponds to the complicated and variable climate of the plateau region. There is no obvious increasing or decreasing trend in runoff at any gauging station. The best hydrological eompensation probability for rivers where water is diverted is about 25% to lO%, and those rivers influenced significantly by diversion are the Jinsha and Yalong rivers. Proper planning and design of compensation reservoirs for the water-exporting area and stretch downstream of the water- exporting area can increase the hydrological compensation possibility from water-exporting area to the water-importing area, and reduce the impact on the stretch of river downstream of the water- exporting area. 展开更多
关键词 South-to-North Water Diversion Project Yangtze River Streamflow Encounter probability Correlation coefficient Cycle Hydrologicalcompensation
下载PDF
An Empirical Study on the Relationship Between China's Maize Price and Maize Import and Export Trade
4
作者 Jiahui HOU Junying WEI 《Agricultural Science & Technology》 CAS 2016年第9期2209-2211,共3页
Based on the time series of China’s maize trade and domestic maize price,the article analyzes the relationship between domestic maize price and China’s maize international trade by using empirical methods.The result... Based on the time series of China’s maize trade and domestic maize price,the article analyzes the relationship between domestic maize price and China’s maize international trade by using empirical methods.The results show that there is a connection between domestic maize prices and China's maize international trade,but the link is not very close.Domestic maize price is the cause of China’s maize international trade change,but its impact is very limited;China's maize international trade also can make some difference on the domestic maize price.Based on the results of research,the article brings three suggestion and expectation to adjust China’s maize international trade and the cost control reasonably in order to stabilize domestic maize price and maize yield,and to protect domestic grain security. 展开更多
关键词 Maize price Maize import and export trade Grain security
下载PDF
上一页 1 下一页 到第
使用帮助 返回顶部