Abstract: A safety system for a steam turbine installation is disclosed based on a closed circuit principle and includes a two-channel low-pressure section in which safety devices are utilized and a high pressure section. Each channel of the low-pressure section acts hydraulically on the high pressure section by way of a tripping and reset relay. The high pressure section includes a high pressure hydraulic system and is divided into an intermediate safety system and a principal safety system each having a two channel arrangement. A one-channel common safety system is provided with stop valves for the steam turbine. Feed and discharge amplifiers are hydraulically connected in series and separate the intermediate and principal safety systems.