This International Standard deals with the definition and the characteristics of control systems and is the basis for tender documents and technical tenders. It is not limited to the actual controller tasks but also include other tasks which may be assigned to a control system, such as for instance sequence control tasks, safety, provision for the actuating energy. The testing of control systems for hydro turbines can generally fulfil the following tasks: – verification of system characteristics as per contract specification; – verification of general proper functioning in the workshop and/or on site; – tests to prove the fulfilment of guarantees; – assessment of the actual state of an existing control system with regard to the question of repair or replacement. This standard covers the following systems: – speed, power, opening, water level and flow control for all turbine types; – electronic, electrical and fluid power devices; – safety devices; – start-up, shutdown devices etc.