随着社会经济地迅速发展，人民生活水平地不断提高，现代社会对电力系统提出更高的要求-高的可靠性以及良好的电能质量保证。因此，配电自动化系统(Distribution Automation System, DAS)是配网自动化发展的必然。配网线路如果有故障发生，就需要快速地进行故障诊断(确定故障发生线路、故障设备或者线路上可能断开的开关，即确定故障区域)、故障隔离和恢复供电，最终减少停电时间并降低损失。 因此，研究配电网故障诊断最终目的是要找到一种比较好的故障诊断方法。当配电网发生故障的时候，相关工作人员可以快速准确地找到故障线路、隔离故障线路、及时派出检修人员到故障现场进行处理。这对减小用户停电时间、缩小配电网停电面积、提高配电网的供电质量、提高配电网的服务水平有着极其重要的意义，将会取得十分明显的运行效率和经济效益。 目前，国内外涌现出大量的故障诊断方法。比如：专家系统、神经网络、贝叶斯理论、Petri网理论等等。论文针对某10kV农配网线路故障诊断系统，提出将Petri网理论用于农配网线路故障诊断。通过对农配网线路建立其对应的Petri网理论模型，再应用Petri网理论的数学方法进行故障判断。文章主要介绍了配电网系统、故障诊断系统。最后对Petri网理论做了探讨，通过实际应用示例得出该方法可以减少故障诊断时间、尽快消除故障。

With the rapid development of social economy, the living level of people unceasing enhancement. The modern society puts forward higher requirements to the power system, high reliability and good power quality guarantee. As a result, the distribution automation system-DAS is inevitable development of distribution network. If the distribution line fault occurs, need to quickly diagnosis the fault(determine the fault line, equipment failure, line disconnect switch, which is to determine the fault area), fault isolation and restoration of power supply, in order to reduce the outage time, reduce the loss. Under the background, the research of distribution network fault diagnosis problem. The ultimate goal is to find a better method of fault diagnosis, when the distribution network fault, staff can quickly and accurately find the fault line, isolate the fault line and sent relevant personnel to handle the fault site. It is important significance to decrease users outage time, reduce power area, improve the distribution network power supply quality, improve the service level of the grid, increase operation efficiency and economic benefit. At present, a large number of fault diagnosis methods have emerged at domestic and foreign. For example: Expert system, Neural network, Bayesian theory, Petri net theory ect. The article on 10kV agricultural distribution line, put forward the theory of Petri nets on rural power distribution network line fault diagnosis. This paper mainly introduces the power system, fault diagnosis system. At the end of the discussion on the Petri net theory, through the practical application shows the method can reduce diagnosis time, eliminate the fault as soon as possible.