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安全稳定控制系统是电网安全稳定运行的重要保证。随着高压直流输电系统在“西电东送、全国联网”格局中的广泛应用,其调制功能必将成为一种重要的稳定控制措施。文中根据在南方电网及三峡电网中的工程经验,总结、介绍了安全稳定控制系统与直流极控系统之间相互交换信号内容和要求,以及接口方案。该方案对其他电网的安全稳定控制系统的设计、制造和运行具有重要的参考价值。 相似文献
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对于远距离、大容量、交直流并联运行电网,交直流控制保护的配合对电网的安全稳定有着重要的影响。直流基频和2次谐波保护是交直流系统间相互配合的基本保护功能。利用EMTDC仿真软件和实时数字仿真(RTDS)对交直流混合运行电网中直流系统50 Hz和100 Hz保护整定原则进行了深入研究,提出了与交流系统故障清除时间和直流主设备承受能力相配合的100 Hz保护整定原则,并给出了基于EMTDC仿真的定量计算方法。该整定原则已应用于南方电网的天广、高肇和兴安直流输电系统,解决了南方电网中存在的交直流保护不配合的关键问题。 相似文献
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电力系统安全稳定控制装置的动作行为直接影响电网的安全运行。对设备跳闸、尤其是交流输电线路跳闸的正确判断是稳定控制装置正确动作的重要前提。论述了用电气量判断输电线路跳闸的必要性,研究、分析了线路跳闸电气量的变化特征,以及潮流转移、失步振荡、低频振荡等动态过程中电气量变化与线路跳闸的区别;对目前使用的跳闸判据及有关判别条件的正确含义进行了解释,分析了现场运行中所出现的误判事件的原因,指出目前使用的跳闸判据的正确性;提出了防止误判跳闸的有效措施。文中讨论的内容将有助于澄清目前国内在这方面存在的分歧和认识方面的误解,以提高安全稳定控制系统运行的可靠性。 相似文献
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研究了天广交直流系统并联运行的系统稳定性,介绍了天广直流系统的稳定控制功能以及天广交直流系统并联运行的紧急控制措施。研究表明天广交直流系统并联运行具有较大的输电能力和较好的稳定性。将直流系统自身的稳定控制功能和辅助的交流系统安全稳定装置适当地结合起来使用,可以有效地控制和减小系统单一元件或多元件故障对系统的冲击,改善交直流并联系统运行的稳定性。 相似文献
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浅谈三峡电力系统(左岸)安全稳定控制装置 总被引:1,自引:1,他引:0
三峡电力系统(左岸)投产后,华中电网和川渝电网通过“三万线”实现联网,在系统正常和检修方式下,发生线路或变压器故障以及线路过负荷或高周时,需要采取切除三峡电力系统(左岸)机组、压出力、向直流极控系统发送调节直流功率的命令或切除部分负荷以及解列“三万线”等控制措施,才能确保电网的安全稳定运行。为此,装设在三峡左一电站、三峡左二电站、龙泉换流站、荆门(斗笠)变电站、荆州换流站、葛洲坝换流站的安全稳定控制系统显得非常重要。 相似文献
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远距离、大容量、交直流混合运行电网中,交直流系统间的相互影响非常复杂。文中以南方电网交直流混联系统运行实例为基础,讨论了直流系统控制功能在交流系统故障期间的作用,分析了交流系统故障时可能误动的相关直流保护监视功能及换流变和站用变保护等,并给出了相应的改进建议。这不仅有助于提高直流输电系统的运行维护水平,确保交直流系统的安全稳定运行,还为未来直流输电系统的设计、交直流输电系统控制保护功能的合理配合等提供了有益的参考。 相似文献
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《给水排水》2014,(9)
正As the eldest and most distributed professional journal of water industry,Water Wastewater Engineering(W WE)gained very wide acceptance from the colleagues working in this field in this country since start publication in 1964.Now it is administrated by the Ministry of Construction of the People’s Republic of China and sponsored by the China Civil Engineering Society etc. 相似文献
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Samples were taken year-round at eleven sites along the altitudinal profile (2900-1400 m a.s.l.) of the Gunnison River, a 329 km tributary of the Colorado River, to document the distribution of the Plecoptera and to evaluate responses to hypolimnial-release dams in the headwaters and middle reaches. Twenty-two species were present, with the greatest species richness occurring in an unregulated segment upstream of the middle reach dams; average nymphal biomass over the study period (175 organisms, 395 mg dry mass m?2) was also greatest in this segment. Only four species (58 organisms, 48 mg m?2) were present in the tailwaters of the headwater dam and values were greatly reduced (nine species; 35 organisms, 180 mg m?2) below the middle reach dams. The stonefly community recovered ca. 80 km downstream from the last dam (15 species; 244 organisms, 250 mg m?2), apparently in response to natural resetting of environmental conditions corresponding to those above the middle reach dams. At the most downstream site (11) only four species (four organisms, 16 mg m?2) were present. The observed distributional pattern is a classic serial discontinuity in response to hypolimnial stream regulation in a temperate latitude river. 相似文献
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根据冗各电站地下厂房开挖支护的施工顺序,以隐式杆单元模拟锚杆,以壳单元模拟混凝土喷层,采用三维非线性有限元技术,对洞室群的开挖支护动态过程进行了模拟计算。通过三维非线性有限元计算分析得到:洞室群动态开挖过程中围岩应力变形的分布规律,围岩塑性区的发展规律,锚杆受力变化情况。计算结果表明:整个开挖过程中,洞周围岩位移变化规律正常,量值较小,塑性区主要分布在洞室周边,围岩稳定性较好;但在洞室交叉口处围岩的变形较大,出现较大范围的塑性区,在此基础上提出了支护措施优化方案,并对优化方案的效果进行了评价。 相似文献
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Tracey Magrann Stephen G. Dunbar Danilo S. Boskovic William K. Hayes 《Lakes & Reservoirs: Research and Management》2012,17(3):231-239
Cyanobacteria often dominate eutrophic lakes, outcompeting green algae that are required by fish and zooplankton. This study was undertaken to ascertain the impact of the cyanobacterium, Microcystis, on algal biodiversity. Under laboratory conditions, we found that the presence of Microcystis decreased phyla richness by 58%, phyla evenness by 47%, genera richness by 66% and genera evenness by 51%. Analysis by mixed anova s demonstrated a significant interaction between treatment and time and confirmed a significant reduction in richness and evenness of phyla and genera. We also conducted a phosphate restriction assay on the algae in Mason Lake (Irvine, CA, USA) and found that the threshold needed for algal growth there was 0.02 mg L?1 PO4. A pilot study was then conducted to test the effectiveness of the Blue Pro? water treatment facility in removal of this colonial organism from Mason Lake, in addition to removal of dissolved nutrients required for its growth. We measured a 97% reduction in Microcystis cells, a 72% reduction in chlorophyll‐a, and a 96% reduction in phosphate after just one 10 min cycle through the unit. Our study demonstrated that removal of Microcystis colonies may allow green algae to increase in numbers. This may improve algal biodiversity, which will benefit zooplankton and fishes. 相似文献
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The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects. 相似文献
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The floodplains of lowland rivers contain diverse aquatic habitats that provide valuable ecosystem services but are perturbed when intensively cultivated. Hydrologic, water chemistry and biological (fish) conditions in five aquatic habitats along the Coldwater River, Mississippi, were measured for more than 4 years: the river, two severed meanders that functioned as backwaters, a managed wetland and an ephemeral channel draining cultivated fields. Off‐channel habitats were connected to downstream regions 0.10% to 32% of the dry season and 24% to 67% of the wet season. The median temperatures for the five monitored sites ranged from 18°C to 23°C, the median total solids concentration for all sites was 135 mg L?1, the median total phosphorus was 0.29 mg L?1 and the median total nitrogen was 1.56 mg L?1. Chemical and physical water quality displayed strong seasonal differences between the wet winter/spring and the dry summer/fall periods so that temporal variation consisted of gradual seasonal trends superimposed on strong diurnal variations. All off‐channel habitats exhibited periods of hypoxia and temperatures >30°C during the dry season. Between‐site gradients of water and habitat quality were strongly coupled to water depth and runoff loading. The rehabilitation of one backwater by increasing water depth and diverting agricultural runoff was associated with improved water quality and fish species richness relative to an adjacent untreated backwater. The diversion of polluted runoff and the use of water control structures to maintain greater water depth were observed to be effective management tools, but the former reduces the water supply to habitats that tend to dry up and the latter reduces connectivity. Published in 2011 by John Wiley & Sons, Ltd. 相似文献
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簸箕李引黄灌区水沙分布及优化调度的经验 总被引:1,自引:0,他引:1
灌区利用水沙观测所取得的资料和试验数据,运用水沙运动力学理论,总结分析和揭示了灌区水沙分布的规律和特点。在此基础上,结合灌区的实际运行情况,围绕减少骨干渠道的淤积进行探讨、研究,进而,优化水沙调度方案。该方案实施后,骨干渠道减旅伴效果明显,取得了成功的经验。 相似文献
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小湾水库大坝防渗面板及其裂缝的加固处理 总被引:1,自引:0,他引:1
小湾水库大坝防渗面板整体抗渗性能差,且存在多条裂缝,通过对面板钢丝网喷涂丙乳砂浆加固处理及其裂缝修补,大坝渗漏量明显减少,且左岸上灌浆廊道内及大坝下游坝面92~93 m高程下廊道入口处原有小股射流全部消失. 相似文献
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Carbon dioxide (CO2) and methane (CH4) diffusive emissions were measured during two field surveys in Queensland and Tasmania, Australia, using the floating chamber method. Bubbling and degassing emissions in 2010 were estimated in Koombooloomba Dam reservoir using only inverted funnels and gas concentrations, respectively. A total of 14 reservoirs and 16 rivers and lakes were sampled from 2006 to 2010. Spatial variation was substantial within each water body, as well as between them. The main drivers of diffusive emission variation were physiographic region and climate, with a clear demarcation being observed between diffusive emissions from tropical Queensland and temperate Tasmania, and between the humid West Coast Range (Tasmania) and dry Central Plateau (Tasmania). Higher CO2 and CH4 diffusive emissions were observed during the dry season, when long water residence times would promote organic matter degradation. Estimated total gross emissions, including diffusive, bubbling and degassing emissions, for Koombooloomba Dam reservoir were about 1.5 × 106 t CO2eq km2 per year, or 24 × 106 t CO2eq per year. This corresponds to a plant emission factor of 3.18 kg CO2eq MWh?1. Using an estimate of terrestrial emissions derived from literature data for the Tully River catchment area, rough estimated net emissions from the catchment area are about 44 kt CO2eq per year, or 5.83 kg CO2eq MWh?1, which is in the lower range of the studied reservoirs. 相似文献