Research On Calculation Method Of The Optimal Break Point Set In Loop Network Protection Coordination

Determining the minimum break point set is one of key steps of relay protection setting calculation in loop network. Since the break point do not cooperate with other protection coordination, which not only making it the weak department of power grid, but also the important factors affecting safety and stability of power grid. The minimum break point set often more than one group, and there are differences between the different minimum break point set. It is very important of how to solve multigroup minimum break point set and select the optimal break point set in loop network. This article mainly studies the method of solving minimum break point set and the evaluation index of optimal break point. The concrete content are as follows:Firstly, the basic concepts of graph are introduced, the principle of solving break point set based on graph and the properties of break point set are analyzed. The parallel lines and non-branch path of network are simplified, which reduces the number of directed simple loops. The method of how to form all directed simple loops and the solving approach of simplified network break point set are studied. Combined with example the process of forming directed simple loop and solving break point set are given.Secondly, the method of calculating minimum break point set is proposed, which bases on the improved quantum-inspired binary particle swarm optimization algorithm. Combined with the character of minimum break point set, quantum-inspired particle swarm optimization algorithm is improved, which introduces initial particle optimization, tabu list and partial mutation strategy, and its improves convergence speed and global searching ability of the algorithm. Example analysis shows the effectiveness of the method.Finally, the cause of break point relay vulnerability is analyzed. The break point protection importance assessment is converted to the circuit where the protection installed. The circuit electrical betweenness, circuit break degree of risk and the average distance indexes are built. On the basis of this, the index of relay protection importance as selecting the optimal break point set is proposed. Simulation example shows that this index can fully reflect the important degree of relay in the power grid, according to it can select the least importance optimal break point set effectively.