The standard deals with the maintenance of grid-connected wind turbine generators (WTGs). It provides information on maintenance, inspection, repair, testing, documentation and spare parts maintenance. Particular attention is paid to the aspects of safety, cost-effectiveness and protection of the investment by means of effective and efficient maintenance over their intended lifetime. In its focus it deals with the operating phase of the WTG and serves as an overview and is essentially aimed at operators of commercial wind turbines. From a technical point of view, a wind turbine is always a combination of a building and a machine. As a result, special standards must be set for maintenance. The standard stipulates which maintenance activities should be implemented holistically and safely, economically and effectively in conjunction with an individually developed maintenance concept.