电力供应系统功能失效分析

本文介绍了电力系统的地震功能评估方法，尤其对电力系统功能潮流分析方法作了深入的探讨，它不仅考虑电力设施在地震作用下的连通性问题，也考虑了供电系统的潮流（包括电压和功率）变化对供电系统的影响问题。从而为供电系统抗震分析，功能评估及灾害预防提供理论基础。     

电力系统地震功能失效数值模拟与控制分析

本文研究了电力供应系统地震功能失效评估方法,尤其对电力供应系统功能潮流分析方法与负荷的控制问题作了深入的探讨.不仅分析了供电系统的潮流(包括电压和功率)变化对供电系统的影响问题,而且建立了电流控制模型,利用DSEA控制算法对供电系统进行负荷控制,并在此基础上进行了系统过负荷时的数值模拟研究;另外,通过一实例分析,对本文的研究方法进行了验证,从而为供电系统抗震分析、功能评估及灾害预防提供理论基础.     

电力供应系统地震安全性优化控制研究

在深入研究电力供应系统潮流分布特性、发电机出力和成本曲线特性、电力系统地震安全性分析与控制的基础上,将安全约束最优化控制算法运用于电力供应系统地震安全性控制中。通过对算法的网络线性分析模型、发电机出力约束条件、线路潮流约束条件和目标函数的深入研究,得出该算法的实施过程;而后,结合供电系统潮流分析的快速解耦法、安全性分析的灵敏度安全性分析法和本文的安全约束最优化控制算法,编写了相应的Fortran和Matlab计算程序,该程序能在较短的时间内计算出调度控制措施和调度费用;最后,通过一个实际算例的分析与计算,验证了该算法的实用性和优越性。本文工作可为震后供电系统功能快速恢复,减少供电系统经济损失,使系统功能得到最大发挥提供理论分析依据,具有很大的现实意义。     

电力供应系统地震安全分析与控制对策研究

本文对电力系统地震安全性分析与控制措施进行了深入的研究。从电力系统网络模型出发,分析了Newton法和快速解耦法(FDLF)的优缺点,认为快速解耦法更适合于电力供应系统地震安全分析与控制。快速解耦法是在Newton法的基础上,利用高压电力系统的物理特性,将系统的有功和无功功率解耦得到的;该方法提高了分析速度,节省了计算时间。利用灵敏度分析方法研究了震后电力系统的安全性,并用安全性提高解耦算法(DSEA)对系统进行安全控制,最后结合一实例验证了该方法的实用性和正确性,该工作可为震后电力系统负荷快速调整、震区供电系统快速恢复电力供应,减少电力供应系统的损失提供理论分析依据。     

考虑失效相关的电力系统抗震可靠性研究

本文根据电力系统的特点,对发电厂和供电系统分别提出了不同的系统可靠性模型,并对各单体之间失效的相关性也进行了较深入的探讨,同时编制了计算系统抗震可靠性的Ｍｏｎｔｅ Ｃａｒｌｏ法程序。     

基于安全性分析电力系统地震功能失效研究

电力系统地震功能失效有两种方式,一是物理功能失效,二是供电流功能失效。对系统供电流功能失效进行了深入的研究。首先用模糊矩阵对受地震干扰的系统进行连通性分析,之后运用灵敏度安全法对系统进行安全性分析。该方法是将因地震引起的电力供应系统线路开断视为系统正常运行的一种扰动,从系统供电流方程的Taylor级数展开式出发,得到灵敏度矩阵,以系统节点注入的功率增量来计算系统运行变量增量,为判断系统运行状态提供依据。最后结合一个实例验证了该方法的实用性,该工作可作为电力系统地震功能失效分析的理论基础,为电力系统地震防灾和工程加固提供理论依据。     

基于概率的变电站系统抗震性能评估方法研究

正电力系统对于震后抗震救援工作的开展极为重要,作为电力系统的重要组成部分,变电站的抗震性能需要进行深入研究。近年来学者大多针对变电站中电气设备的抗震性能以及变电站正常运行情况下的可靠性进行研究分析,对变电站系统整体抗震性能的研究不足,缺乏评价指标与实用评估方法。本文提出了一种基于概率的系统评估方法,称为状态树方法,可用于评估具有多输入-多输出特征的工程系统的抗震性能,以一个典型220 k V变电站为例阐述了该方法的有效性与实用性。该方法分为4步:(1)定义系统功能;(2)进行系统分析,建立状态树模型;(3)定义部件易损性;(4)利用蒙特卡洛方法计算系统易损性。另外,考虑到电气设备的特殊性,在对大量地震动记录进行统计分析的基础上,对抗震设计反应谱提出了修订建议。本文的主要研究内容如下:(1)对比分析了国内外关于建筑结构、电气设备的抗震设计规范的异同,指出我国规范的问题与不足。搜集近年来美国NGA-West2、日本Ki K-net数据库公布的超过万条强震记录,按照《建筑抗震设计规范》(GB50011—2010)划分4类场地,计算伪加速度平均反应谱,采用最小二乘法进行多参数拟合,重点研究了特征周期、动力放大系数和衰减系数的变化趋势,分析了水平向和竖向地震动反应谱的区别,提出了分别适用于结构、设备的抗震设计标准反应谱。另外,开发了基于反应谱的天然地震动选择程序、人工地震动生成程序,给出了适用于计算电气设备易损性的36组天然地震动。(2)对现有系统分析评估方法进行介绍,指出不足之处。提出一种新的系统分析方法,将故障树方法与成功路径概念相结合,称之为状态树方法。针对一个典型的220 k V变电站,以输送电能为目标,定义了变电站系统的功能。结合变电站平面布置、电气连接方式建立了完整的状态树模型,描述了变电站中各部件的逻辑关系,包括变压器、断路器、隔离开关、电流互感器、电压互感器、避雷器、绝缘子以及各种支架等。(3)对110 k V电压互感器、110 k V电流互感器和10 k V高压变频器进行振动台试验,测试其动力特性与抗震性能。建立电压互感器、电流互感器数值模型,根据36组地震动时程分析结果确定了电气设备的易损性。搜集、整理、分析了现有110 k V和220 k V各类电气设备的易损性研究结果。根据振动台试验、数值模拟以及文献调研的结果,采用双对数正态分布描述电气设备的易损性,确定了各类电气设备的抗震能力中值、随机性和不确定性。(4)结合系统状态树模型与部件易损性参数,利用蒙特卡洛方法计算了变电站不同功能需求对应的抗震能力中值及对数标准差。通过参数分析,研究了部件易损性参数、易损性曲线形式对变电站整体抗震能力的影响。根据各部件对变电站抗震性能的影响大小,确定了变电站的关键设备(薄弱环节)。针对抗震能力较差的电气设备,分析了提高这些设备抗震能力对变电站整体抗震能力的影响。     

电力系统的抗震脆弱性评估模型设计与实现

传统基于多Agent的电力系统抗震脆弱性评估模型,对电力系统抗震脆弱性实施分析时,未考虑节点权重的分配情况,评估效果不理想。因此,设计基于层次分析法的电力系统抗震脆弱性评估模型,基于电力系统节点服务类型和拓扑位置,构建抗震脆弱性评价指标的层次分析模型,基于该模型设置节点权值分配方案,依据该方案采用层次分析法获取风险综合指标,对节点脆弱性指标实施运算,采集不同状态下的各节点脆弱性权值并进行平均运算,获节点脆弱性指标值。基于节点脆弱性指标值,通过层次分析法实现电力系统抗震脆弱性评估。实验结果说明,所设计模型的抗震脆弱性评估结果精度和效率高。     

论用天文因素进行中长期地震预报

天文因素与地震关系的研究符合当代科学发展潮流。本文介绍了用太阳活动、地球自转和天体运动与地震的各种关系进行中、长期地震预报的17个实例。分析了这些方法的适用性和局限性,对天文因素影响地震活动的机制问题作了粗浅探讨。     

供电系统抗震性能分析

介绍了供电系统抗震性能分析方法，结合实例进行了系统功能损失综合评价分析。     

SCIENCE CHINA Earth Sciences SUBJECT INDEX TO VOLUME 57(2014)

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Distribution of throughfall and stemflow in multi‐strata agroforestry,perennial monoculture,fallow and primary forest in central Amazonia,Brazil

The partitioning of rain water into throughfall, stemflow and interception loss when passing through plant canopies depends on properties of the respective plant species, such as leaf area and branch angles. In heterogeneous vegetation, such as tropical forest or polycultural systems, the presence of different plant species may consequently result in a mosaic of situations with respect to quantity and quality of water inputs into the soil. As these processes influence not only the water availability for the plants, but also water infiltration and nutrient leaching, the understanding of plant effects on the repartitioning of rain water may help in the optimization of land use systems and management practices. We measured throughfall and stemflow in a perennial polyculture (multi‐strata agroforestry), monocultures of peach palm (Bactris gasipaes) for fruit and for palmito, a monoculture of cupuaçu (Theobroma grandiflorum), spontaneous fallow and primary forest during one year in central Amazonia, Brazil. The effect on rain water partitioning was measured separately for four useful tree species in the polyculture and for two tree species in the primary forest. Throughfall at two stem distances, and stemflow, differed significantly between tree species, resulting in pronounced spatial patterns of water input into the soil in the polyculture system. For two tree species, peach palm for fruit (Bactris gasipaes) and Brazil nut trees (Bertholletia excelsa), the water input into the soil near the stem was significantly higher than the open‐area rainfall. This could lead to increased nutrient leaching when fertilizer is applied close to the stem of these trees. In the primary forest, such spatial patterns could also be detected, with significantly higher water input near a palm (Oenocarpus bacaba) than near a dicotyledonous tree species (Eschweilera sp.). Interception losses were 6·4% in the polyculture, 13·9 and 12·3% in the peach palm monocultures for fruit and for palmito, respectively, 0·5% in the cupuaçu monoculture and 3·1% in the fallow. With more than 20% of the open‐area rainfall, the highest stemflow contributions to the water input into the soil were measured in the palm monocultures and in the fallow. Copyright © 1999 John Wiley & Sons, Ltd.     

A Monte Carlo study of rainfall forecasting with a stochastic model

A procedure for short-term rainfall forecasting in real-time is developed and a study of the role of sampling on forecast ability is conducted. Ground level rainfall fields are forecasted using a stochastic space-time rainfall model in state-space form. Updating of the rainfall field in real-time is accomplished using a distributed parameter Kalman filter to optimally combine measurement information and forecast model estimates. The influence of sampling density on forecast accuracy is evaluated using a series of a simulated rainfall events generated with the same stochastic rainfall model. Sampling was conducted at five different network spatial densities. The results quantify the influence of sampling network density on real-time rainfall field forecasting. Statistical analyses of the rainfall field residuals illustrate improvement in one hour lead time forecasts at higher measurement densities.     

Anthropogenic Eutrophication and Red Tide Outbreak in Lacustrine Systems of the Kashmir Himalaya

Red tide, a recurrent phenomenon has become conspicuous in several Kashmir lake ecosystems since 1991. The responsible organism (Euglena pedunculata), a rare flagellate rediscovered in the Kashmir Himalaya (Khan 1993) caused first and unprecedented red tide outbreak, constituting a maximum of 96% of resident numerical phytoplankton density in Dal Lake. At present, conflicting hypotheses exist on the generation of causal assemblage(s) imparting redness to waters: Jeeji Bai (1991) linked its origin to acid precipitation – a fallout of burning oil‐fields during the Gulf War – whilst Khan (1993) holds local factor(s) responsible. Field/experimental studies support the latter contention that the influx of untreated sewage, in unison with warm temperatures, high levels of PhAR, iron and interruption to hydrological flow‐pattern together with absence/or reduction in grazing activity created conducive environmental milieu for red tide outbreak. Dal Lake “red tide” drifted the bloom‐inoculum to other waters, including Lake Wular, where additional ecological niches were carved out, threatening the aesthetic value and biological diversity of Kashmir lakes. Ecological monitoring indicates frequent seasonal red tide occurrence in Dal Lake (including summer‐autumn event of 1998) which testifies its unabated eutrophication status. Further studies are needed on ecological adaptability and biogeographic distribution of this rare and unique red tide‐causing flagellate.