8.1.1 直击雷的防护 ·················································································································45 8.1.2 感应雷的防护 ·················································································································46 8.1.3 雷电波侵入的防护 ·········································································································46 8.2 接地装置 ·······························································································································47 8.2.1 接地的有关概念 ·············································································································47 8.2.2 接地装置的设计 ·············································································································47 第9章 结论与展望 ························································································································49 9.1 结论 ·······································································································································49 9.2 展望 ·······································································································································49 参考文献 ···········································································································································50 致谢 ···················································································································································51 附录 ···················································································································································52 附录A 外文资料·························································································································52 附录B 设备汇总表 ·····················································································································69 附录C 主接线图 ·························································································································70
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石家庄铁道大学四方学院毕业设计
第１章 绪 论
1.1 课题研究的背景
随着国民经济的发展，我国铁路运输正向着电气化的方向迅速发展。改革开放以来，我国电气化铁路建设速度逐年加快，“九五”期间建设电气化铁路4783.77km，而“十五”期间的第一年就修建了3665.4km，建设速度十分惊人。至2002年底，我国已建成41条电气化铁路干(支)线，电气化铁路建设总长达到了18615.73km，居亚洲第一，世界第三位[1]。至2007年底，我国的电气化铁路营业路程已达到24046.6km，占我国铁路总营业路程的37.8%，各大干线都已实现了电气化。预计到2020年我国铁路营业里程将达12万公里以上，其中电气化铁路比重将达到60%，总长7万多公里。根据我国电气化铁路迅速发展的需要，我国应加强牵引变电所的建设。
1.2 电气化铁道的发展现状
我国电气化铁路采用单相工频制供电[2]，目前电力系统通常以110kV或220kV的电压等级为电气化铁道提供高压电源。牵引供电系统主要包括牵引变电所和牵引网两大部分[3]。牵引供电回路是由牵引变电所——馈电线——接触网——电力机车——钢轨——回流线——接地网组成的闭合回路。现阶段我国主要采用传统模式进行设计、建造和管理的变电所自动化程度不高，一般需要有稳定的值班队伍。因此我国建设目标是向无人值守方向发展。
国外电气化的水平要高于我国，在变电所的运行管理模式上已经做到了无人值守。例如我国哈大线铁路电气化改造是系统引进德国设备、材料、技术及项目管理方式的电气化工程，具有技术含量高、设备先进等特点。这些新技术是我国电气化铁路的发展方向，值得学习和借鉴。
1.3 牵引变电所简介
牵引变电所是电力牵引的专用变电所，它的任务是将区域电力系统送来的电能根据电力牵引对电流和电压的不同要求转变为适用于电力牵引的电能。牵引变电所分为中心牵引变电所和中间牵引变电所，其主要电力设备是降压变压器，称主变压器或牵引变压器，并设有备用[4]。
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石家庄铁道大学四方学院毕业设计
牵引网由馈(电)线、接触网、轨(地)、回流线等组成，是牵引供电网(回路)，完成对电力机车的送电任务。牵引网供电方式按分区所运行状态分为单边供电、双边供电，按牵引网设备类型分为直接供电、BT供电、AT供电和CC供电方式。
电力系统与牵引变电所的连接方式称为外部电源的供电方式，它取决于牵引负荷的用电等级和电力系统的分布情况。电力牵引为一级负荷，牵引变电所应有两路电源供电，当任一路故障时，另一路仍正常供电。外部电源以保证供电可靠性为原则，可分为环形(双侧)单回路供电方式、环形(双侧)双回路供电方式、单电源(单侧)双回路供电方式、放射供电供电方式。
1.4 本次设计研究的主要内容
本次设计的题目是某中心牵引变电所电气系统设计。 (1)确定牵引供电方案。
(2)确定牵引变压器的容量、台数及型式。
(3)进行短路计算。为选择变电所中的断路器、隔离开关、电流互感器、电压互感器等电气设备以及母线选型、防雷与接地装置的选择及校验提供依据。
(4)对设计的变电所进行继电保护整定计算。 (5)对变电所进行防雷与接地系统设计。
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石家庄铁道大学四方学院毕业设计
第2章 牵引变压器的容量计算和选择
2.1 牵引变压器的容量计算
2.1.1 牵引变压器容量计算的步骤
牵引变压器容量的计算一般分为以下三个步骤：
(1)根据任务书中给定的计算条件求出供应牵引负荷所必须的容量，称为计算容量。
(2)根据列车紧密运行时供电臂的有效电流和充分利用牵引变压器的过载能力，计算出校核容量，这是确保变压器安全运行所必须计算的容量。
(3)根据计算容量和校核容量，再考虑其他因素(如备用方式等)，并按实际变压器系列产品的规格选定变压器的数量和容量称为安装容量。
本次设计采用单相Vv接线的形式，根据任务书中给出的数据，计算式如下：
Sa?U2NI?a (2-1) Sb?U2NI?b (2-2)
2.1.2 变压器计算容量和校核容量的计算
(1)设右供电臂计算容量为Sa，左供电臂的计算容量为Sb。由以上公式得单相Vv接线变压器的计算容量分别为：
Sa?U2NI?a?27.5?620?17050kV?A
Sb?U2NI?b?27.5?410?11275kV?A (2)Vv接线变压器最大负荷为：
Sa.max?2U2NIa.max?2?27.5?880?48400kV?A Sb.max?2U2NIb.max?2?27.5?720?39600kV?A 由公式
S校?Smaxk可得两台变压器的校核容量分别为：
(其中k=1.8) (2-3)
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