The functions and type of turbines' by-pass system for ultra-supercritical units have been presented

the main factors affecting type selection of the by-pass system

as well as the calculation method for capacity of the said by-pass system being expounded.Considering comprehensively the flexibility and the economic efficiency in operation of units

the suitable type of by-pass system and the capacity of by-pass system have been determined

the burbine's by-pass system of three typical ultra-supercritical units having already been put into operation and being under construction in China being completely analysed and summarized.