UNE-EN IEC 61400-8:2025 specifies minimum requirements for the design of wind turbine nacelle-based structures.

It focuses on the integrity of structural components within and in the vicinity of the nacelle, including the hub, mainframe, main shaft, structures associated with direct drive systems, gearbox structures, yaw structural connection and nacelle enclosure. 

It also addresses connections of the structural components to control and protection mechanisms together with structural connections of electrical units and other mechanical systems. 

UNE-EN IEC 61400-8:2025 focuses on ferrous material-based nacelle structures although it can also apply to other materials. It includes the design of bolted and welded joints in nacelle structures and of cast and forged components. 

It specifies the material testing requirements to be used in the design process for nacelle structures. The structural connections of the gearbox and main shaft are also within its scope.

The safety level of wind turbines designed in conformity with this standard is to be equal to or higher than the level required in IEC 61400-1:2019. Probabilistic methods are provided for calibrating partial safety factors and for use in the design process.