An electrical power generating assembly for a wind turbine. The electrical power generating assembly comprises a gearbox comprising a gearbox output shaft, a generator comprising a rotor that is coupled to the gearbox output shaft; and a current measuring module located between the gearbox and the generator. The current measuring module comprises: an electrical pickup mounted to the electrical power generating assembly, wherein the electrical pickup includes an electrical contact that engages with a slip ring associated with the rotor. The current measuring module further comprises: a first current measuring device mounted with respect to the electrical pickup to detect current flowing at least through the electrical pickup; and a second current measuring device mounted with respect to the electrical pickup to detect current flowing through at least a component associated with the gearbox output shaft.