In recent years, power system blackouts caused by extreme weather have occurred more frequently. Based on the analysis of the characteristics of large scale failures of the distribution network in extreme weather, a fault recovery strategy considering repair sequence is proposed to improve the power supply capacity of the distribution network. A two-layer distribution network reconfiguration model considering both reliability and costs is established. Considering both the reliability and the economy, the loss load and the cost of distributed generation are minimized at the upper layer and the lower layer, respectively. Firstly, the statues of tie switches are adjusted after the network failure to construct the new radial network and obtain the topology based on the graph theory. Then the dynamic programming method is utilized to determine the optimal topology and the fault repair sequence. Taking the improved PG&E 69 node system as an example, the effectiveness and practicability of the proposed method for fault recovery under extreme disasters are verified.

As the power grid continues to grow, the number of components on buses is increasing. It requires bus differential protection to integrate reliability and security. This paper has introduced the inspection and handling process of a malfunction accident of 220kV microcomputer bus differential protection. The model bus differential protection was the product after six unified. The basic principle of busbar differential backup protection has been introduced. The causes of misoperation caused by microcomputer bus differential protection are analyzed from three aspects: criterion of operation bus, generation of differential current, and rationality of operation bus voltage blocking. Preventive measures and solutions for preventing malfunction of microcomputer bus differential protection has been given in this paper. Through the suggestion of changing the logic of the criterion of the running bus and the opening of the busbar voltage, the reliability of the protector has been greatly improved and the safe and stable operation of the power grid has been ensured.