Abstract: The trans-province transmission capacity of large-scale hydropower stations depends on the sending end factors: the installed scale, regulating performance, natural water flow, and ultra high-voltage power transmission capacity. This paper presents an analysis model of the trans-province transmission capacity of large-scale hydropower stations. This model evaluates the time variations in runoff in different months using a flood-dry season method, and uses a power maximization model to calculate the maximum theoretical power generation of the hydropower system under the inflows of different frequencies. Then, it analyzes the power balance of the grid. If the daily generating capacity, after the local and overseas load demands deducted, is higher than the total capacity of trans-province transmission, it indicates that the current transmission channel are not enough to meet the demand of external transmission, and new channels should be added to avoid water spilling. The model is applied to the trans-province transmission of the large-scale hydropower stations in Yunnan. The results indicate our model is effective and satisfactory in quantitative analysis of the transmission capacity under different inflow conditions, as a theoretically and practically useful tool for improving the absorption capacity of clean energy and the planning and construction of new transmission channels.

Key words: hydropower absorption, west-to-east power transmission, flood-dry season evaluation, reservoir dispatching