A power transmission system for a wind turbine comprises a gearbox and generator. The gearbox includes a gear-box housing and gearbox output member. The generator includes: a generator housing having a drive-end side and non-drive-end side, the drive-end side being coupled to the gearbox housing; a stator supported by the generator housing; a rotor coupled to the gearbox output member so as to be driven thereby; a non-drive-end shield coupled to the non-drive-end side of the generator housing; and at least one auxiliary drive mounted to the non-drive-end shield. The at least one auxiliary drive is configured to rotate the turning gear. A corresponding method of installing a wind farm including such a power transmission system is also provided.