Noise, vibration and harshness (NVH) problems are critical issues to be tackled in case of rotating machineries. At this purpose, operational modal analysis (OMA) represents a powerful tool. OMA methods can be applied under the assumption that the excitation acting on the system under analysis is white noise. This requirement is not met in case of rotating machines, due the presence of excitations related to rotating elements. For this reason, harmonics need to be dealt with. This work focuses on two techniques for dealing with harmonics: the use of a cepstrum signal editing procedure and the use of order based modal analysis (OBMA). This paper shows the potential of these two methodologies when processing a continuous stream of real data coming from an offshore wind turbine drive train.