Transmission Network Planning Considering Short-circuit Current

The rapid development of power grids leads to more and more electromagnetic ring and quickly enhanced short-circuit current level, which has put power system at great security and stability risks. Short-circuit current level is related with electrical network structure directly, therefore, the factor of short-circuit current should be taken onto account in the stage of power network planning to achieve a integrated optimum between short-circuit current capacity and transmission capacity. In traditional methods, short-circuit current is usually checked after transmission network planning is finished, which can hardly guide transmission network planning through the technical index of short-circuit current, as a result, short-circuit current of the planning result may at some point exceed the maximum short-circuit rating of circuit breakers. In this paper, literatures of transmission network planning and current-limiting measures were studied in order to put short-circuit current index into transmission network planning model, and a transmission network planning model considering short-circuit current was proposed. This thesis mainly obtains the following results:1. The recently research of transmission network planning was described, including the principles and steps of conventional transmission network planning and various planning models and corresponding solving algorithms. The impact of electrical network structure to short-circuit current level was analyzed based on practical calculation method of three-phase short-circuit current, and the applications of all kinds of short-circuit current limiting measures was introduced.2. Two industry examples of adjusting electrical network structure to limit short-circuit current were given, and the theory of line-breaking measure to limit short-circuit current was analyzed. Finally, the principles of opening electromagnetic ring were introduced after analyzing their advantages and disadvantages.3. An electrical network structure optimization model on purpose of limiting short-circuit current was proposed. The New England39-bus system was calculated applying branch selecting strategy based on sensitivity index, and some practical optimal solutions are given.4. An bi-level transmission network planning model considering short-circuit current was presented, which employed traditional transmission network planning as upper level and electrical network structure optimization as lower level, and they updated themselves by exchanging planning schemes. Garver-6-bus system was solved based on immune algorithm to verify the effectiveness of the model presented.