Abstract: The supporting role of power communication network to power grid is more and more important. The principle based on N–1 is not enough to guide the channel arrangement of relay protection service. Protection relay of important transmission lines need to realize double protection and three routes, that is to meet N–2 requirement. Based on this, in order to find out weak links of the currently network, and to optimize the network structure or channel mode, it is needed to analyze N–2. This paper firstly describes the basic concept and research necessity of N–2. Then the idea and algorithm model of N–2 analysis and decision is put forward. Using the algorithm model and enumerating examples, the N–2 analysis of three typical scenarios of trans regional interconnection line, UHV transmission line, power plant transmission line is carried out, and the statistics of satisfying N–2 in the regional network is presented, the weak links are analyzed. At last, it introduces the important role of satisfying N–2 in reducing the fault time, improving the operation rate and maintaining the safety of the power network, which is of great significance to the quantitative evaluation of the reliability of the power communication network in this area and the reinforcement of the grid.