Currents flowing in the shaft of the generator might damage its bearings. As a consequence, that can result in reduced operating time and large financial losses. This work proposes a protection system which utilises Rogowski coil and concepts of IEC 61850-9-2 (Process Bus) to protect the generator agains such currents. Also, it shows results of the laboratory and on-site testing where the actual measurements of the shaft currents were obtained.