滨海滩涂输电线路接地装置抗腐蚀设计探讨

位于滨海滩涂的接地装置受海水电化学腐蚀、海洋微生物和海洋生物腐蚀的影响,引起接地体的受损甚至断裂,得不到有效保护的焊接点因腐蚀而受损,严重时引起接地体剥离,接地装置解裂.文章分析了金属接地体的腐蚀成因,并从接地体的选择、优化接地体布置方式、焊接点的防腐蚀和接地装置腐蚀防护等方面进行研究分析,得到提高滨海滩涂输电线路接地装置耐腐蚀性的方法.     

广西110kV送电线路杆塔接地装置分析

广西区内大部分110 kV送电线路工程主要采用放射形接地装置,在一些土壤电阻率高的地区通过添加降阻剂来辅助接地,仅在水田和部分居民区采用闭合环形接地装置。为了解决放射形接地装置占地面积过大导致施工容易受阻、降阻剂腐蚀接地体容易导致安全隐患的问题,笔者对广西区内的一些线路工程采用的杆塔接地装置进行分析,指出了各种杆塔接地装置存在的一些利弊。建议应更有效地应用接地模块以及闭合环形接地装置,以更好地实现110 kV送电线路安全投产、运行可靠、维护方便。     

浅析扬水站、点接地体腐蚀的原因及对策

一、问题的提出 接地体是直接与土壤接触、有一定散流电阻的一个或多个金属导体,也称接地极。它是扬水站、点电力系统接地装置的一个重要组成部分。唐山市丰南区扬水站、点大部分建于20世纪六七十年代,接地体的材料全部采用钢材,开挖检查发现,运行25年以上的扬水站接地体腐蚀严重,已呈锈断状态。另据历年电气预防性试验表明,大部分接地体已不能满足接地电阻的要求,严重威胁着扬水站、点的安全运行。     

水情自动测报系统中接地装置的设计

水情自动测报系统接地装置的结构主要有单列垂直接地式、网格式组合接地式和辐射式组合接地式。接地装置的接地电阻主要由接地体本身的电阻、接地引线电阻、接地体表面与土壤的接触电阻、散流电阻4部分构成。接地装置设计时,在低土壤电阻率的地区可采用单列式接地装置;在高土壤电阻率的地区采用深埋接地极、人工改善土壤等措施降阻。结合金沟河灌区的实际,介绍了在水情自动测报系统接地工程中可以采用的几种设计方案,阐述了各方案的使用条件和应用中应注意的问题。     

电气设备的接地装置及其运行维护浅谈

接地是确保电气设备正常工作和安全防护的重要措施,电气设备接地通过接地装置实施。接地装置由接地体和接地线组成,与土壤直接接触的金属体称为接地体;连接电气设备与接地体之间的导线(或导体)称为接地线。     

征地困难地区输电线路杆塔接地装置研究

方框加放射线接地装置由于水平敷设的放射线较长、占地面积较大,容易引起青苗赔偿纠纷,造成施工困难,延误工期。针对该问题,从接地材料、施工特点及全寿命周期费用等方面,研究无放射线的方框加铜覆钢垂直接地棒的接地装置。结果表明在强腐蚀土壤中采用铜覆钢材料,减少了维护费用,提高了运行的安全性和可靠性;在征地困难或青苗赔偿较高地区采用垂直接地装置能够减少水平接地沟的开挖,减小施工阻力及保障施工工期,具有较好的经济效益。     

对电力免维护接地装置的探讨

传统的接地装置耐腐蚀能力差,使用寿命短,安全性能低,维护成本高。本文介绍了用铜包钢做成接地体和接地线,使接地装置全部组成元件都具有铜材的良好抗自然腐蚀能力的免维护的接地装置,分析了其保障人身安全、设备安全和电力系统安全的优越性。在此基础上,提出了免维护接地装置的制造工艺和设计要求,并对其应用前景进行了展望。     

对电力免维护接地装置的探讨

传统的接地装置耐腐蚀能力差,使用寿命短,安全性能低,维护成本高。本文介绍了用铜包钢做成接地体和接地线,使接地装置全部组成元件都具有铜材的良好抗自然腐蚀能力的免维护的接地装置,分析了其保障人身安全、设备安全和电力系统安全的优越性。在此基础上,提出了免维护接地装置的制造工艺和设计要求,并对其应用前景进行了展望。     

浅谈农网改造中变电所接地装置改造

在农网改造中,接地装置的改造扩建,是变电所改造中必不可少的一部分,它对变电所安全运行具有非常重要的意义。该文介绍了接地相关知识、接地常采用的方式、接地装置改造需注意的几个问题,以及遇高土壤电阻率的解决方法等。     

引汉济渭二期工程北干线土壤对PCCP管腐蚀性评价

引汉济渭二期工程北干线压力管道拟采用预应力钢筒混凝土管道(PCCP),管道存在被土壤腐蚀的可能,对管道沿线进行土壤腐蚀性测试PCCP管腐蚀性进行评价,结果显示,沿线地层对钢结构具腐蚀性,腐蚀等级为微～强腐蚀;管道沿线粗、细粒土对钢结构的腐蚀性等级差别较大。根据评价结果建议采用防腐层外加阴极保护的联合防护措施;设计防护措施时可在确保工程安全运行的前提下,根据管道所处土壤类别分别设计;及早建立PCCP管土壤腐蚀性评价体系。可为管道防腐设计提供依据。     

Call for Papers

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.     

地下厂房施工过程的三维非线性数值模拟分析

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。     

Evaluation of freshwater mussel relocation as a conservation and management strategy

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.     

基于模型试验的河床砂砾石层基本特性研究

为了经济可靠地确定深厚覆盖层的基本特性参数,以大渡河双江口水电站坝基河床砂砾石层基本特性研究为工程背景,进行大尺寸模型试验,研究河床砂砾石层的旁压模量和动探击数随密度、级配以及上覆压力的变化规律。根据室内模型试验结果,结合现场旁压试验及钻孔试验成果,推断出坝址区河床砂砾石相关层位的密度,并依此进行砂砾石室内力学试验,获得设计所需力学参数。研究成果可为深厚覆盖层基本特性测试提供新的方法。     

SPATIAL AND TEMPORAL WATER QUALITY VARIABILITY IN AQUATIC HABITATS OF A CULTIVATED FLOODPLAIN

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.     

Spatio‐temporal variation of gross CO2 and CH4 diffusive emissions from Australian reservoirs and natural aquatic ecosystems,and estimation of net reservoir emissions

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.     

Automated system for removal and pneumatic transport of fly ash from electric precipitator hoppers

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. __________ Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008).     

The flood pulse advantage and the restoration of river-floodplain systems

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.     

基于BP神经网络-马尔科夫链模型的隧道围岩位移预测

在隧道工程施工中,围岩位移预测起着很重要的作用。将BP神经网络-马尔科夫链模型引入到隧道围岩位移预测中来,通过对训练样本的学习,利用BP神经网络实现了对位移时间序列的滚动预测,同时得到了实测值与预测值的相对误差;在此基础上利用马尔科夫链对相对误差进行修正,有效地提高了预测结果的精度。并将该模型应用于某公路隧道拱顶下沉位移时序预测中,结果表明该模型具有精度高、科学可靠的特点,为隧道围岩变形的预测提供了新的途径。     

Short communication. Pipelines as a refuge for freshwater snails

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.