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介绍了RCS-978数字式变压器成套保护装置的硬件组成、保护原理及功能。它集成了一台主变的全套电量保护,对每台主变采用双套主保护、双套后备保护的配置原则,可提高安全性和可靠性。装置中差动保护采用了独特的差动二次电流相位调整方法、可靠的励磁涌流及TA饱和判据,反时限过激磁保护的动作特性针对不同的变压器过励磁倍数曲线进行配合。主保护包括高灵敏度的工频变化量比率差动、稳态比率差动、差动速断、零序比率差动和过激磁保护,后备保护配置灵活、完善,其跳闸出口采用整定方式。另外,装置还具有完善的录波打印和事件报文功能,并配有后台管理分析软件。 相似文献
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指出了通道误码是一个同通道长度相关的指标,分析了误码对线路纵差保护的影响,介绍了实际运行中必须解决的引起非随机误码的一些原因,并分析了通道双向延时不对称度对线路纵差保护正常运行的影响,指出用于线路纵差保护的复用通道双向路由必须一致。 相似文献
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巴基斯坦某水电站5号机组开机并网后,在增负荷过程中220 kV主变C相差动保护动作,根据主变保护装置故障录波及报文数据,发现事故原因为主变低压侧B相CT绕组极性反接,调整其极性后再次开机,机组、主变正常投运,故障解除。在此故障现象的基础上,分析了YNd11联接组别的变压器,在不同的差动保护相位调整方式下,主变高、低压侧单相CT二次绕组极性反接时,对保护装置三相差动电流计算的影响。 相似文献
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提出了一种基于故障分量的分相阻抗差动保护新原理。该原理分别提取线路两端保护安装处的故障分量进行阻抗计算,然后利用这2个阻抗之差构成阻抗差动判据。该原理无需进行采样数据同步处理,耐受电容电流和过渡电阻的影响。电流幅值差动保护判据以线路两侧的电流幅值差为动作量,幅值和为制动量,在发生电压互感器断线时,可作为阻抗差动保护判据的补充判据。仿真结果验证了该原理的正确性和有效性。 相似文献
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差动保护原理已经广泛应用于高压线路保护,但受电容电流的影响,全电流差动保护的抗过渡电阻能力低。文中提出基于电阻性差流分量的差动保护新原理,利用差电流的电阻性分量来构成差动保护判据,可以避免电容电流的影响。该原理与线路电容参数及电抗器补偿情况无关,对于高阻接地故障的灵敏度高,可以作为现有差动保护原理的补充。EMTP仿真验证了基于该差动保护新原理所构成的保护判据的可靠性和灵敏性。 相似文献
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介绍了发电机失磁保护的4种主判据,针对阻抗Ⅱ段和低电压判据延时较长的不足,提出利用发电机功率变化量作为失磁保护辅助加速判据,并介绍了实际微机保护装置的动模试验情况。 相似文献
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指出了电子式互感器(ET)接入的线路光纤差动保护在数据同步方面遇到的主要困难,分析了全球定位系统(GPS)同步方法与传统数据同步方法的局限,提出了利用改进插值法进行数据同步的新方法。该方法不依赖于任何外部设备,可靠性高;不调整采样时刻,适应于IEC 60044-8标准规定的合并单元功能结构条件,并能灵活适用于线路一侧为ET一侧为传统互感器的情况。数据同步的目标始终是要保证参加差动运算的电压电流量追溯到一次侧是同一时刻的,为此,各侧ET二次变送延时的影响必须被计及到保护装置的数据同步过程之中。对保护装置而言,补偿两侧ET二次变送延时的时间差是数据同步的核心内容。对需要配置光纤差动保护的线路,ET的合并单元最好能够提供符合IEC 60044-8标准的数据输出接口。 相似文献
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直流输电线路保护中,以电压变化率为动作判据的线路行波保护和低电压保护难以检测出线路高阻接地故障,线路差动保护需要通过闭锁躲避区外故障而使动作延时较长,从而难以起到后备作用。同时,直流控制系统环节对线路保护的动作特性也有很大的影响,小负荷水平下将导致线路电流波动而导致差动保护拒动。结合某一直流线路实际参数,基于真实的直流控制保护模型与参数的EMTDC仿真平台,采用实际故障录波分析和仿真分析相结合的手段,系统分析了线路保护不正确动作的机理以及直流系统控制环节对线路保护的影响,并提出了解决方案。 相似文献
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针对常规保护配置不能满足中低压系统中多端线路快速全线切除故障的难题,提出了一种基于光纤通信的多端线路电流差动保护新方案。具体介绍了保护装置的工作原理、同步方式、通信方式、硬件构成及测试结果等。动模试验结果表明,所提出的多端线路光纤电流差动保护装置性能优越,完全能够满足T接线路全线速动切除故障的要求,在中低压系统中具有良好的推广使用价值。 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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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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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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In the lower River Murray, Australia, populations of gastropods have declined markedly over the past 40 years. Of the native fauna of about 18 species, only the ancylid Ferrissia petterdi remains common (but in patches), and another five species feature in sporadic local resurgences. Until recently the viviparid Notopala was thought to be extinct. The introduced physid Physa acuta is widespread, but in low numbers. The decline probably is associated with flow regulation, high turbidity and the introduction of common carp. Snail populations have persisted, however, in irrigation pipelines fed from the river, where they periodically cause blockages. This paper reports the discovery of the only known populaion of Notopala hanleyi in a pipeline where the inner wall accumulates microbial and other organic matter, providing high quality food for snails. In the Murray before regulation most of the periphytic biomass was probably microbial, as fluctuating water levels would have maintained littoral communities in a highly productive, early state of succession his postulated that, by stabilizing seasonal water levels, regulation has promoted the production of filamentous green algae, an inferior food source, and so displaced snail populations from the open aquatic environment. 相似文献
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V. K. Konovalov O. V. Yashkin V. V. Ermakov 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2008,42(2):105-109
A system for removal and pneumatic transport of fly ash is examined, in which air pulses act on batches (pistons) of ash formed
in a duct. Studies are made of the effect of several physical parameters on the force required to displace a piston of ash
and these serve as a basis for choosing a system for removal and pneumatic transport of ash simultaneously from several hoppers
of an electric precipitator. This makes it possible to separate the ash particles according to size without introducing additional
components. Formulas are given for calculating the structural and dynamic parameters of this system and measurements of indirect
dynamic parameters are used to calculate the input-output characteristics of the system. In order to optimize the system,
configurations for summing several ducts into a single transport duct for pneumatic ash transport are proposed. Some variants
of dry ash utilization and the advantages of producing of size-separated particles are considered.
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Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008). 相似文献
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Peter B. Bayley 《河流研究与利用》1991,6(2):75-86
The ‘flood pulse advantage’ is the amount by which fish yield per unit mean water area is increased by a natural, predictable flood pulse. Evidence for this increase is presented from tropical and temperate fisheries. It is argued that increasing multispecies fish yield by restoring the natural hydrological regime is consistent with increasing production of other trophic levels and with restoration from ecological and aesthetic viewpoints. When applied to a river-floodplain system, this restoration would provide a large, self-sustaining potential for recreation, commercial exploitation, and flood control. An interim ‘natural flood pulse’ restoration approach is proposed for systems modified for navigation. This approach approximates the natural hydrological regime in a river reach and is intended as a first step in the long process of restoring the watershed. 相似文献