Abstract:Sustained, rapid and unbalanced electricity demand growth and the rapid development of renewable energy have brought about new trends and new changes in China''s energy and power development. In order to make the power balance target more diversified and solve the shortcomings of the current power balance and substation capacity demand calculation method, this paper proposes a power balance and substation capacity demand calculation method in the market environment. This method consider the distribution network to optimize the allocation of resources, and consider the adequacy of power balance, energy saving and new energy consumption and medium voltage grid construction of the overall economic benefits and social benefits, and solve the power supply range calculation method can not completely distinguish between 110kV and 35kV network, integration of high capacity load ratio selection method does not apply to such deficiencies, enhance the medium voltage distribution network interconnection and mutual supply ability, as well as various types of power plants, the construction scale of installed capacity level, substation site landing guidance. The validity of the method is fully illustrated by the example analysis at the end of the paper.