摘要:变电所的二次系统即工厂供电系统或变电所的二次回路，其由二次设备及其相互连接的电气回路构成，是对变配电所一次系统进行进行监测，控制，调节和保护的系统。它是保证电力系统可以安全生产，经济运行，可靠供电的重要保障。

　　　本设计是为机械厂35kv总降压变电所设计的二次系统。首先，根据课题申请表和任务书，搜集该机械厂的相关的原始资料，然后对所搜集的原始资料进行整理，依据原始资料确定该厂的一次系统的参数，设计主接线图，选择相应的主变压器台数和容量。在此基础上，进行具体的二次系统设计。

　　　结合所学知识和相关设计规则，根据该厂一次系统的情况确定二次系统的系统框图，确定一次设备，设计操作电源系统，监测系统，继电保护和自动系统，控制和信号系统。　

关键词 负荷计算；一次系统；二次系统

Abstract:Substation secondary system, namely power-supply system of the factory or substation secondary circuit , which is composed by secondary equipment and other related-electrical circuit, is the system that monitor, control, regulate and protect the primary system of substation. At the same time, it is the critical guarantee that ensure the power system can produce power safely, operate power economically and supply power reliably.

　　　The aim of this project is to design the secondary system for total 35-kv step-down substation of the machine factory. First of all, on the base of the application of subject and specification, the author  collect some related-original materials of the machine factory; then investigate these collected original materials; at last, from the above analysis, the author determine the parameters of primary system, design the main wiring diagram and select the sets and capacity of corresponding main transformer. According to the above research, the author will set about the design of specific secondary system .

　　　Combined with the knowledge and related design rules and based on the condition of primary system, the author design the diagram of secondary system, determine the primary equipment, design and operate power-system, monitor-system, protection automatical system, regulation system and signal system.

Keywords  Load calculation  Primary system  Secondary system