Abstract:The simulation and analysis of two operating conditions are carried out with and without the speed - regulating characteristics of hydroelectric generating set in the current power grid,and the tie - line transmission power limits under both conditions are obtained. According to the results,the tie - line transmission power limit with speed - regulating characteristics of hydroelectric generating set is higher than the tie - line transmission power limit without speed - regulating characteristics of hydroelectric generating set. But as the current power grid is consisted merely of hydroelectric generating set,the tie - line transmission power limit will also be restricted by the anti - regulation characteristics of hydroelectric generating set under faulted condition.