The global increase in energy generated from the natural resource of wind power is growing at an astonishing rate. As the current trend to develop wind turbines of increasing power capacity continues, the requirement to validate the performance and reliability of new designs is more important than ever. A fundamental consideration before launching a new design of power transmission system is outlining procedures for type testing. Typically, type testing should include full functionality test, overload tests, cold start, operation under emergency conditions, verifying gear mesh load intensity distribution (KHb) and for planetary gearboxes with more than three planets verifying load sharing distribution (Kg). Recent experience of a significant amount of unexplained bearing failures calls for additional requirements of type testing which should target dynamic behaviour of rolling element bearings. In recent years Transmission Dynamics have elaborated a comprehensive range of ultra-miniature instrumentation, which includes electronic gear mesh alignment modules deployed in multiple stages of complex designs of epicyclic stages, planet load sharing distribution, digital multi-channel torque and shaft bending measuring systems and planet carrier deflection measurements. The system can be further enhanced by including instrumentation targeting the dynamic behaviour of individual rolling elements as a result of complex interactions of a complete power transmission system, including blades and power electronics. The configuration, installation and operation of such instrumentation systems is described in this paper. The paper concludes that type testing of wind turbines should include detailed study of the dynamic response of a complete transmission system deployed in fully operational wind turbines, followed by an extended period of in-service load measurements.