Abstract:Power system relay protection is the most important defense line to ensure the safe and stable operation of the power grid. According to different functions, the power system energy transmission network can be divided into multiple links, such as generation, transmission, transformation, distribution and user, and each part has protection devices. When a fault occurs on the user side, due to the mismatching of the configuration between the protections, there will often be leapfrog tripping, resulting in the expansion of the fault and even the cracking of the power grid. In particular, under the current high proportion of renewable energy penetration in the distribution grid, higher requirements are put forward for the coordination and classification of relay protection, and the fault characteristics of the distribution network have changed significantly. Based on the consideration of the influence of the grid connection of distributed generation on the hierarchical protection of power system transformation and distribution, this paper first establishes calculation models for the distributed generation, then analyzes the fault characteristics of the distributed generation connected to the distribution grid, and discusses the influence of distributed generation on the relay protection of power system, especially the coordination among transformation, distribution and user protection.? Finally, an example of the proposed collaborative hierarchical protection optimization method for power system is analyzed, which proves the effectiveness and scientificity of the proposed method.