Results 21 to 30 of about 14,739 (118)
主要通过EMPT电磁暂态分析软件对10 kV串联间隙金属氧化物避雷器在配电网系统中安装使用时进行仿真分析,首先进行PS15绝缘子及10 kV环电极避雷器及穿刺避雷器产品的U50%放电电压试验,再仿真分析在不同接地条件下只安装单相产品对同级其它相绝缘子的影响及只安装一级对相邻级绝缘子的影响,分析得出无论是直接接地还是单独接地,当雷电流超过40 kA后均会造成相邻相或相邻级的绝缘子闪络,建议全线安装或在雷击严重区段及易击点全线安装10 kV串联间隙金属氧化物避雷器,不需单独设置接地,条件允许可在末端设置接地。
刘素芳, 陈康, 刘思贤
doaj
分析了城市中低压配网的接地拓扑结构,研究了10 kV配网中性点经小电阻接地后的380V侧接触电压隐患以及安全条件。针对单台区独立式和多台区互联式的台区接地方式,依据相关标准和典型设计分别建立场路模型,开展了台区单相接地故障时的接触电压安全性及影响因素仿真研究。结果表明:1)对于单台区独立式的台区接地方式,保护接地与工作接地的最小分开距离受接地电阻和重复接地影响;2)对于多台区互联式的台区接地方式,最小互联台数与台区间距离、重复接地密切相关。
雷潇, 廖文龙, 刘强, 李林欢
doaj
Monitoring population extinction risk with community science data
Our modelling framework provides a robust, computationally efficient and easy‐to‐apply tool for monitoring local persistence probability that can support global conservation efforts. This will complement the monitoring of species population viability in places where standardized monitoring is still lacking, but community science observations are common.
Orlando Acevedo‐Charry +8 more
wiley +1 more source
Summary The importance of marine angiosperms, or seagrasses, as foundation species for marine coastal ecosystems is in marked contrast to their low species number of only 70 described taxa. Seagrass species tend to have very similar overall morphologies dictated by hydrodynamic forces of the ocean environment.
Xiaomei Zhang +14 more
wiley +1 more source
【问】什么是异相接地故障?电力部门为什么要求在非有效接地系统中应选用通过异相接地故障开断试验的断路器? 【答】在中性点非有效接地系统中,在一相断路器的内侧和另一相断路器的外侧各产生一个单相接地的故障,称为异相接地故障。异相接地故障实际是一种特定的两相接地故障。在开断异相接地时,断路器首开相上将出现1.73倍相电压工频过电压 ...
林立生
doaj
Laser‐guided thin‐film self‐rolling for asymmetric small‐scale swimmers
Graphical abstract AbstractSmall‐scale robots are promising miniaturized devices in biomedicine. Thin‐film self‐assembly is a commonly used strategy to fabricate tubular small‐scale robots. However, the existing methods have limitations like complex manufacturing processes and limited control of self‐assembly behavior.
Yi Chen +11 more
wiley +1 more source
Joint Extraction Method for Spatial Relations in Chinese Geological Texts
Abstract Extracting spatial relations of geological entities is an important prerequisite for achieving natural language processing tasks such as geological knowledge question answering and semantic search, and is an important means to achieve structural reconstruction of unstructured geological data.
Chuan Chen +9 more
wiley +1 more source
110 kV沙土变同等条件下不同中性点接地设备故障处理对比试验及其分析
2015年10月,国网江西省电力公司赣西供电分公司在同等条件下分别对自动消弧线圈和ZXC系列主动干预型故障相转移接地装置做了单相瞬时性接地故障、单相永久性接地故障处理试验。试验结果表明:自动消弧线圈由于补偿后的残流控制的不好,不能及时熄灭瞬时性接地电弧,对永久性接地故障接地选线的准确率仅为33%;ZXC系列主动干预型故障相转移接地装置能及时消除瞬时性接地故障,选线准确率达100%,能及时选出并切除永久性接地故障。确保了故障点的安全。
晏锋
doaj
我国城市中低压配电网电容电流急剧上升且消弧线圈补偿效果欠佳,单相接地故障电弧难以自熄易产生弧光接地过电压及扩大事故,探究弧光接地故障的快速有效熄弧方法是保障配网稳定安全运行的基础。首先根据主动转移型消弧技术的工作原理,建立熄弧过程的等效电路,利用叠加定理推导熄弧时故障点电流计算公式,分析其与故障点位置、接地点过渡电阻、线路负荷电流等因素的关系;然后采用Matlab/Simulink搭建10 kV小电流接地系统单相接地故障模型,其中采用控制论电弧模型模拟单相弧光接地故障;最后通过设置典型的故障点位置 ...
李景丽, 任俊跃, 赵子敬
doaj
Including the urbanization gradient in people‐centered wildlife conservation in Amazonia
Abstract Conservation policy in the Amazon traditionally focuses on rural areas, overlooking the socioecological roles of urban populations. This oversight can hinder sustainability by neglecting rural–urban connections. We compared the prevalence and quantity of wild meat consumed, bartered, and traded commercially in rural, peri‐urban, and urban ...
Lísley P. Lemos +3 more
wiley +1 more source

