An electrical power generating assembly (20) for a wind turbine (1). The electrical power generating assembly comprises a gearbox (22) comprising a gearbox output shaft, a generator (24) comprising a rotor (32) that is coupled to the gearbox output shaft; and a current measuring module (40) located between the gearbox (22) and the generator (24). The current measuring module (40) comprises: an electrical pickup (42) mounted to the electrical power generating assembly (20), wherein the electrical pickup (42) includes an electrical contact (44) that engages with a slip ring (48) associated with the rotor (32). The current measuring module further comprises: a first current measuring device (50) mounted with respect to the electrical pickup (42) to detect current flowing at least through the electrical pickup; and a second current measuring device (52) mounted with respect to the electrical pickup (42) to detect current flowing through at least a component associated with the gearbox output shaft.