The Research Of An New Protection In Distribution Network

With the rapid development of economy and electric power demand increases quickly, distribution network becomes more complexity, and conventional protection cannot meet the need of the protection in distribution network. The reasons are: 1. the relay settings are not best settings under different mode of operation(including the main mode of operation) cased by changes of the network; 2. the performance of protection become worse and reject action when most disadvantage fault occur under the least mode of operation of the network. To solve these defects, adaption protection is brought forward and used widely.Firstly, the paper analyses the origin and development condition of adaptive protection; analyses the structure,start-up model and implementation model of the computing relay settings; and analyses the current situation of the protection in distribution network,the application of adaptive protection in distribution network protection and the researches in the world.Secondly, the paper systematically discusses the theory of Genetic Algorithm and introduces the main modified measures towards the Genetic Algorithm's defects of premature convergence, low ability of local searching, no norms in encoding and failing to express constraint conditions of problems, and improves Genetic Algorithm's selection operator, gene reorganization operator and gene mutation operator. Following are the specific improvements: 1. Adopting the selection ways of the best save strategy and two two competition. 2. Adopting the hyperbolic curve reorganization probability and exponent mutation probability increasing with the relative maintenance generation of the best individual.Finally, the paper introduces the mathematics model of Genetic Algorithm application in adaptive protection in distribution network .Its object function is minimizing the sum of the operation times of relays. The paper defines the start-up condition(the mode of operation and protection action),and analyses the restraints particularly. The researches using Matlab indicate that the application of the modified Genetic Algorithm in distribution network protection is efficiency and feasible.