Results 11 to 20 of about 190,115 (170)
500kV直流断路器快速机械开关典型故障特性及可靠性提升方法研究 [PDF]
, 2023 直流断路器是构建柔性直流电网不可或缺的关键设备。快速机械开关是直流断路器中承载电流、实现快速分合闸、耐受分闸恢复电压的核心组件，其结构复杂、动作速度快、电气应力严酷、可靠性要求高，因而设计研制难度大，任一环节出现问题均会影响直流断路器乃至柔直电网的安全可靠运行。然而，目前快速机械开关由于存在设计选型不合理、工艺管控不严格、试验考核不完善等问题，导致在实际工程应用中故障率较高。针对已应用于张北柔性直流电网试验示范工程的500 kV直流断路器，分析了直流断路器研制、调试 ...
张涛 +4 more
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South as a Sight ‘å—方’, from a branch to a necessity to World Literature
Journal of Research in Social Science and Humanities, 2023 In the discussion and debates on the world literature system, methodologies and methods is a topic that is valued. Moretti and Apter have prominent different opinions on the adoption of digital or abstract data outside texts and contexts. The way Moretti views the world literature system is highly based on historiography and studies of the Annual ...
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Gaoya dianqi, 2022 容性电流开断能力，特别是C2级开断能力，已成为断路器满足工程需求的关键指标，因开断过程中易发生重击穿故障而导致试验失败的风险较大，故需对其容性开断能力进行评估。基于容性电流特点，文中采用“恢复电压”及“最小临界电压”评估其开断容性电流能力，且“恢复该电压”低于“最小临界电压”时，断路器具有开断容性电流的能力。采用电场及气流场耦合分析方法，断路器开断性能进行评估，得到试验工况下“恢复电压”均小于“最小临界电压”，表明该断路器具有容性电流开断能力，顺利通过C2级试验验证，进一步表明采用“最小临界电压 ...
郭自豪 +8 more
doaj
Gaoya dianqi, 2023 直流断路器是交直流混合配电网组网的关键，然而在考虑技术经济性时，当前直流配电断路器仍沿用高压直流输电等级断路器拓扑方案的思路不再适用，亟需开发经济型直流开断技术，实现中压直流配电断路器成本和性能的平衡。文中针对交直流混合配电网直流侧故障电流经济高效开断这一关键问题，基于直流熔断器和强迫过零开断技术，提出一种基于熔断器的组合式直流开断方案，该方案采用直流熔断器与转移开关并联后再与直流负荷开关串联的形式，利用低成本的直流限流熔断器开断大电流，减轻直流负荷开关的开断要求，进而降低整机成本 ...
王昊晴 +4 more
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Gaoya dianqi, 2020 高压直流断路器是多端直流输电及高压直流系统联网的基础和安全保障,它不仅要能够开断短路电流而且要能够开断小负载电流,实现对高压直流系统的保护及控制功能。文中在振荡回路中对机械式高压直流断路器开断大电流及小电流的性能进行了测试。分别测试机械式高压直流断路器开断17.5 kA和开断50 A电流时的恢复电压值和恢复电压变化率。在试验中发现机械式高压直流断路器开断17.5 kA电流时可以在叠加高频振荡电流后的第1次过零点处开断,但是在开断50 A电流时需要在第2次电流过零点处才能开断。开断50 ...
高俊珍 +4 more
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Integrative Conservation, EarlyView.This study reconstructs the phylogeny of the Javan Hawk‐Eagle (Nisaetus bartelsi) within the subfamily Aquilinae using Maximum Likelihood and Bayesian Inference algorithms on a blood sample and GenBank data. The analysis reveals that the sampled genus Nisaetus forms a monophyletic group. Furthermore, N. bartelsi occupies a sister‐taxon of N.
Almas Lathifatul Ula +3 more
wiley +1 more source
The collective application of shorebird tracking data to conservation
Conservation Biology, EarlyView.Abstract Addressing urgent conservation issues, such as the drastic declines of North American migratory birds, requires creative, evidence‐based, efficient, and collaborative approaches. The abundance of over 50% of monitored North American shorebird populations has declined by over 50% since 1980. To address these declines, we developed a partnership
Autumn‐Lynn Harrison +71 more
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Gaoya dianqi, 2021 多断口真空断路器的各个串联断口存在非同期现象,为此需要探明非同期的影响,进而得到在不降低其开断能力的情况下的有限异步分断方法。文中以永磁操动的模块化真空断路器为研究对象,分析了影响永磁操动精度的因素,理论分析了非同期对多断口真空断路器开断能力的影响,综合杂散电容和弧后不平衡电荷的影响,提出了三断口真空断路器的有限异步开断方法。搭建了模块化串联多断口真空断路器试验平台,试验研究了有限异步开断方法对开断成功率的影响。试验结果表明:高压侧提前动作1.7 ms,可将开断成功率提高16 ...
曾祥浩 +4 more
doaj
Conservation Biology, EarlyView.Abstract Procedural, distributional, recognitional, and epistemic justice aspects of conservation interventions are well documented in contexts where pastoralism is a key livelihood and way of life. Geospatial analyses and representations of wildlife conservation and restoration that are increasingly applied in pastoralist rangeland socioecological ...
Ryan R. Unks
wiley +1 more source
Learning Styles, Engagement and Anxiety in AI‐Mediated Writing: A Multimodal Feedback Study
International Journal of Applied Linguistics, EarlyView.ABSTRACT Artificial intelligence (AI) tools now permeate English academic writing. However, evidence on how feedback modalities align with student differences and with psychological mechanisms remains limited. Prior work often reduced learning styles to simple matches with delivery modes and treated learning engagement and writing anxiety as peripheral.
Yi Ren +3 more
wiley +1 more source