摘要:电力系统是由发电、变电、变电、配电和用电等环节组成的电能生产与消费系统。它的功能是将自然界的一次能源通过发电动力装置（主要包括锅炉、汽轮机、发电机及电厂辅助生产系统等）转化成电能，再经输、变电系统及配电系统将电能供应到各负荷中心，通过各种设备再转换成动力、热、光等不同形式的能量，为地区经济和人民生活服务。
为保证工业生产安全进行，保证电能合理输送.分配，灵活改变运行方式，特进行本次设计。本次毕业设计的主要内容是机械厂降压变电所的设计。
该次设计主要内容包括：负荷计算和无功功率补偿，变电所主变压器台数、容量和类型的选择，变电所主接线方案的设计，变电所进出线的选择与校验，变电所一次设备的选择和校验，短路电流的计算，变电所二次回路方案的选择及继电保护的整定，及防雷保护和接地装置的设计。
本次设计的内容紧密结合实际，通过查找大量资料，设计出符合要求的变电所。本文中若有设计不够明了或研究深度不够的内容，恳请老师引导 。
关键词： 变电所；短路电流；设备选择；变压器保护；主接线
Abstract：Electric power plant and substation system is made, substation, power distribution and power consumption of links such as electric power production and consumption system. It's the function of the nature a energy through the power generation power device (mainly including boiler, turbine and generator and power plant auxiliary production system, and so on) into electrical energy, then after losing power distribution system and distribution system, electric power supply to the load centers, through all sorts of equipment to convert power, heat, light and so on the different forms of energy, economy and people's life in for service.
To ensure that industrial production safety, ensure reasonable electric power transmission. Distribution, flexible change operation mode, the design nugent. The graduation design is the main content of the design of machinery factory step-down substation.
This time design main content includes: load calculation and reactive power compensation, main transformer substation sets, capacity and types of choice, the design of the main substation wiring schemes, substation the choice of the outlet and calibration, substation a equipment choice and check, the calculation of short-circuit current, substation secondary circuits scheme selection and relay protection setting, lightning protection and grounding device design.
The design of the actual content close, through the search for a large number of data, designed to meet the requirements of substation. This paper if design is clear or research depth, not content, ask teachers guide.
Keywords: substation， Short circuit current， Equipment choice， Transformer protection， The Lord wiring
