Abstract: In Fujian Huadian Kemen Power Generation Corporation Limited project phase I, when the unit operated under high load, the high pressure regulating valve of the small steam turbine was opened, a great quantity of cool reheating steam participated in working, and the high pressure regulating valve and low pressure regulating valve jittered frequently in large amplitude. According to analysis, it was considered that the fault reason is the setting of the overlap of high pressure regulating valve and the low pressure regulating valve of the small turbine tended to be larger. The degree of overlap had been modified in accordance with the value recommended by the manufacturer of the microelectrohydraulic control system devices, and the unit can operate normally in full load. 
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Key words: small steam turbine, electro-hydraulic control system of small steam turbine, high pressure and low pressure regulating valves, jitter, degree of overlap