Research On Distribution System Short-circuit Anaylsis Based On Phase-component Methods

Distribution system is an important part of power system to supply power to users. It is different form the traditional transmission system in network structure and operation mode. It has some specific features, such as radial structure, larger R/X, three-phase unbalanced and so on. So the single-phase analysis method used to the traditional system is not suitable to the distribution system.More and more people realize the importance of distribution system with the proposed smart grid and the study on the problems occurring in distribution system is carrying out. Adapt for the needs of smart grid and the access of the distributed generators, new requirements to the power flow calculation and fault analysis of distributed system are put forward.This paper studies the distribution system's operation characteristics and common grounding methods, and puts forward a kind of fault analysis method which based on phase component method. System mathematical mode is established by node admittance matrix. For the source, transformer, line, load and shunt capacitor of the distribution system, the detailed three-phase models is provided each. Further more, the node admittance matrix of each element is expressed respectively in phase and line component.Considering the features of distribution system, this paper adopts the implicit Zbus-Gauss algorithm. This algorithm is good at convergence and stability when dealing with the branch network and calculating the distributed system flow. This paper analyses metallic and non-metallic short circuit tpye, and also takes into consideration short circuit faults at distribution nodes or somewhere else.For diffierent type of faults,lists correction methods respectively, what's more, unifis them in the form.Finally, the 4 buses and 20 buses system is uset to test the method proposed in this paper. The results of these examples verify the effectiveness and feasibility of this algorithm.