林区电网改造中配电线路导线截面的选择

１ 概述在森工系统农村电网建设与改造工程中,配电线路导线截面的选择是一项很重要的工作。导线是电网中输送电能的主要元件之一,正确地选择导线截面,对电力网的技术经济合理性具有重要的意义。     

厄瓜多尔CCS水电站站用13.8kV线路导线截面选择

通过选择合理的架空输电线路运行方式来解决电压损失超标问题,从而确定经济可靠的线路导线截面。     

微型计算机在输电线路计算中的应用

在设计输电线路时,常根据经济电流密度来选择导线截面,用允许的线路电压损失来进行校验。三相架空线路的电压损失的百分数,可由下式计算:     

关于导线和电力电缆截面的选择计算

为了保证电线路安全、可靠、优质、经济地运行,在选择导线和电力电缆截面时必须满足正常运行时的最高允许温度;同时还要保证正常运行时允许的电压损耗、经济电流密度及机械强度。     

低压导线截面选择及供电半径的确定

低压导线截面的选择,有关的文件只规定了最小截面,有的以变压器容量为依据,有的选择几种导线列表说明,在供电半径上则规定不超过O．5km。本文介绍了一种简单公式作为导线选择和供电半径确定的依据,仅供参考。     

三相联动可调型智能绝缘支架的研制

配网旁路不停电检修消缺作业技术的快速发展，满足了大部分架空线路带电作业复杂项目的应用工况需求。但在应用过程中，旁路引下电缆挂接垂直架空线路时，由于电缆外屏蔽接地因素对相邻导线绝缘遮蔽要求苛刻，影响了整体作业效率。研制一种三相联动可调型智能绝缘支架，可快速完成旁路引下电缆的接火作业，提高作业效率。     

浅谈高压电缆线路设计

文章着重对110 kV及以上高压电缆线路在设计过程中需要注意的问题进行了较为详细的分析,主要从电缆选型、电缆护套的选择、感应电压的限制以及高压电缆线路的防雷和接地等方面进行了详细的论述。     

山区架空电力线路的路径选择和杆塔定位

架空电力线路的路径选择是线路建设中的一个重要部分，直接影响到线路建设的经济性、安全可靠性和施工维护。本文就如何进行正确的线路路径选择提出了具体的原则，同时结合大兴安岭地区山区的特点，提出了如何进行适当的电力线路的杆塔定位的方法，从而提高线路建设的经济性和运行安全可靠性。     

10 kV配网电缆故障分析及防范措施

电力电缆线路的正常运行才能保障电力的输送和有线通信的畅通,一旦电力电缆发生故障,就会造成电力以及通信的中断,如能及时查出电缆故障原因并迅速予以排除,可避免造成重大的经济损失和不良的社会影响.因此,10 kV电力电缆运行的可靠性对我国配电网系统来说至关重要.主要针对10 kV配网电缆日常存在的故障问题进行分析,然后提出相...     

电缆截面核算在电缆选型中的应用介绍

介绍了电缆截面核算的原理及其影响因素,并通过应用案例,对电缆截面核算在城轨车辆电缆选型中的应用进行介绍。     

A computer model to differentiate skidder and cable-yarder based road network concepts on steep slopes

Road spacing on slpes depends on the underlying off-road transportation technology. One major decision in road network planning is to determine under what terrain conditions ground- or cable based extraction systems should be applied. The present investigation aims to develop a road spacing model for steep slope conditions and to implement a total cost model for skidder and cableyarder based road network concepts. The study analyzes transportation and road geometry to specify the relationship between road density, slope gradient, and road spacing. Production functions for skidder and yarder-systems make it possible to derive transportation cost as a function of road density and slope gradient. A total cost function integrates road building cost, harvesting strategy, and production economics to derive optimal road density for the two network concepts. The difference between the cost levels at optimum road density is an indicator for differentiating cable and skidder-based extraction systems. The model was implemented as a Visual Basic add-in for Microsoft Excel spreadsheet software. This flexible approach makes future adaptations and changes very easy due to the modular concept. The validity of the model is limited to the production functions of the underlying off-road transportation technologies. Future work needs to develop production functions for the state-of-the-art technologies and to improve the road building cost model.     

大跨度悬索静力构形和内力计算方法

建立悬索重力曲线方程的差分形式,给出悬索在自重、索端移动、集中力作用下非线性分析的一种简单的有限差分法迭代模型。与有限元方法不同,本方法不需要悬索初始线形,只需要输入悬索两端坐标、索截面面积、弹性模量、初始张力,可计算悬索在不同状态下的张力和线形,算例表明该方法收敛速度快,精度高。     

Walderschließung und forstlicher Straßenbau in der Schweiz

Summary In Switzerland developing of forest areas is part of regional planning Access to all parts of forest is opened up by truck roads and secondary lines (tracks, cable cranes). To obtain optimum results transport systems should be planned considering several aspects, viz. silviculture, access, transport, recreation social welfare, economics. Applying soil mechanics, soil stabilization and technology of road materials for pavement design permits constructing good roads with minimum cost of, construction and maintenance.      

锚管桩+锚索+框架梁复合支护在高边坡防护中的应用

以吉林敦化至延吉一级公路12合同段锚管桩、锚索、框架梁工程为例，介绍锚管桩＋锚索＋框架梁复合支护体系的应用情况及施工方法，进行了预应力锚索生产性试验过程与分析，以及生产性试验验证和调整设计参数。     

济南建邦黄河公路大桥主桥斜拉桥辅助墩顶超重主梁施工控制措施

济南建邦黄河大桥主桥是一座三塔、双索面的预应力混凝土梁斜拉桥,跨度布置为53.5＋56.5＋2×300＋56.5＋53.5m,中塔处为塔梁墩固结。主梁采用前支点挂篮进行施工,边跨合龙段位于过渡墩与辅助墩之间,中边跨合龙有一定难度。墩助墩顶主梁较重,施工难度大,本文主要介绍了该桥辅助墩顶超重主梁施工的方法及控制的措施。     

Optimum geometric layout of a single cable road

Cable-based technologies have been a backbone for harvesting on steep slopes. The layout of a single cable road is challenging because one must identify intermediate support locations and heights that guarantee structural safety and operational efficiency while minimizing set-up and dismantling costs. Our study objectives were to (1) develop an optimization approach for designing the best possible intermediate support layout for a given ground profile, (2) compare optimization procedures between linearized and nonlinear analyses of a cable structure and (3) investigate the effect of simplifying a multi-span representation. Our results demonstrate that the computational effort is 30–60 times greater for an optimization approach based on nonlinear cable mechanical assumptions than when considering linear assumptions. Those nonlinear assumptions also stipulate lower heights for intermediate supports and a larger span length. Finally, compared with the unloaded case, tensile force in the skyline is increased by as much as 80% under load for a single-span skyline configuration. Our approach provides additional value for cable operations because it ensures greater structural safety at a lower cost for installation. Improvements are still needed in developing a stand-alone application that can be easily distributed. Moreover, our rather simple assumptions regarding set-up and dismantling costs must be refined.     

哈尔滨道外二十道街松花江大桥主桥方案比选

哈尔滨道外二十道街松花江江段将修建松花江公路大桥,笔者就拟建大桥的四个方案做比较选择最佳方案。通过方案比较,认为宜选用大跨度的现代化桥,提供较自由的通航净宽,避免水中基础、减少水中施工,推荐使用主孔410m的双塔混合梁斜拉桥方案。     

集中力作用下索的静力特性精细化分析

悬索桥施工中主梁吊装及自锚式悬索桥吊杆张拉,都需要计算和监测集中力作用下悬索的索力和变形.论文推导了悬索在集中力作用下的无量纲形式的平衡方程和积分形式的协调方程,把协调方程在线性和非线性条件的索力增量方程分别转化为一次、二次和三次方程进行求解,然后对荷载位置、荷载大小以及艾维参数对线性和非线性条件下的索力增量的影响进行精细化分析.研究表明：各种条件下索力误差较小,不考虑索的增长条件下,索的变形特征主要是几何构形变化,荷我在时,正挠度和负挠度分别达到了最大值.     

The Restricting Effects of Forest Certification on the International Trade of Wood Products

Forest certification has increased the cost of companies which has affected the international trade of wood products. This paper examines forest certification costs of companies, and based on this, uses partial equilibrium to analyze its trade restriction effects, and uses space price gradient field model to check whether it is a substitution for tariff barriers. Our conclusion shows that forest certification has restricted the trade of wood products due to its high certified cost, and clarifies that in the case of tariff reduction, trade of wood products are hindered by different levels and different costs of forest certification. This paper implies that efforts should be made to increase the amount of certified forests worldwide. It is necessary to lower the certified cost and important that government policy measures to support certification should include consideration of who bears the cost, support for aggregation of smallholder growers and improved communication in timber supply chains.