Research On Improving The Success Rate Of Reclosing In Small Hydropower System

Small hydropower is an clean and renewable energy which is internationally recognized, and its development is conducive to improving the rural energy structure, increasing the supply of clean energy, and corresponding the application of the preferential policies for renewable energy. Power system has lots of small hydropower systems which contact through the weak line and large grid-connected, such as the small hydropower systems of the northwest of Shimen. After the failure of contact lines and small hydropower systems split from large electric systems, small hydropower systems have large power gap in the dry season, while have large surplus power in wet season. As most of faults in the power system are transient faults, therefore reclosing in power system has widely applied. However, in an small hydro electricity systems, if small systems have large surplus power after the failure of contact lines, there will have the question of check the same period of reclosing unsuccessful. In this paper, considered the actual operation system of small hydropower system in Shimen county, Changde city, combined the climate characteristic of small hydropower system.through the detailed analysis of existing problem, we study the selection of reclosing method and the improvement of reclosing success rate under different operation mode.We analyse its contact line reclosing problems for solving the question of check the same period of reclosing unsuccessful. After analysing the status of small hydropower systems of the northwest of Shimen, we found that the existing methods are not suitable for reclosing, for the contact line switching power is larger, the time of line main protection action take too long and setting the splitting point of station is difficulty, and so on. Based on analysis of the equal-area law of transient stability of power systems, this paper proposed a method to analyze the physical meaning of the process of conceptual clarity. The method is calculating the maximum allowable frequency difference of closing and the limit closing time. This paper also have simulated and analysed the maximum allowable time and frequency of reclosing when the transmission power is not the same time,and simulation results show that the consistent with the theoretical analysis. It provide a reliable basis for the final solution of reclosing. Sensitivity of trajectories with transient stability was applied to generator triping control strategy,which select the order and ensure minimum generator triping capacity, and use the simulation image as a reference, analysis the stability of reclosing of small power grid when 110kV power line fault in different transimission power.To improve the existing small hydropower systems in northwest Shihmen automatic reclosing success rate, a series of corresponding measures was proposed. Detailed analysis shows that corresponding measures was unique under the conditions of the existing protective devices.