1. Scope This part of IEC 61850 specifies the logical node classes for use in the domain of hydroelectric power stations, steam and gas turbines. 1.1 General This IEC61850 domain information model standard utilizes the existing Logical Node (LN) classes defined in IEC 61850-7-4 Basic communication structure Compatible logical node classes and data object classes where possible, while defining new and extended domain specific LN classes to provide the necessary data objects for application to functions and systems in in the domain of hydroelectric power stations, steam and gas turbines. The domain information model includes the interface towards a central operator centre s control functions. The Scope related to steam and gas turbine specifics is limited to the overall control functions, generator and turbine control functions. For hydroelectric power the scope includes the entire power station automation system. The Edition 3 is intended to form a basis for extensions in local implementations. Such extensions may be defined in profiles.