The steel company SSAB in Borlänge will, in the near future, replace its protective relays in one of their substations due to the condition and age of the relays. In connection with the change, SSAB intended to switch the current communication protocol IEC 60870-5-103 (IEC 103) to IEC 61850. They were thus interested in knowing what differences there were between these protocols and what were the technical and economical pros and cons for the change. To answer SSAB's questions, this bachelor thesis project was initiated with the aim of a feasibility study regarding the relays change and the protocol switching. To this purpose, the relevant parts of the substation and its functions were first examined to have an overall picture and the understanding of how they worked and interacted. After that, the communication protocols IEC 103 and IEC 61850 were investigated separately and comparatively. After a few weeks a visit was paid to SSAB to visually see what was to be done and to obtain a better understanding. During the visit, the substation that would receive new protection relays were shown and how their parts in the system were connected and interacted. Besides, other electrical devices were also shown, for example, large step-down transformers and a capacitor bank. After this, further study of the protocols, the relays as well as the associated parts were conducted and the information collected. Finally, the collected information was analysed, compared and documented in this thesis to generate a result and a comparison. From this feasibility study, it is clear that the new protocol had many advantages technically and some economically, which in particular include: 1) communication where IEC 103 uses master/slave at speeds up to 10 Mbit/s and IEC 61850 uses client/server and peer to peer at speeds between 100 Mbit/s to 1 Gbit/s; 2) connection where IEC 103 was point to point and with IEC 61850 it will be connected in ring formation for better redundancy; 3) interoperability where IEC 103 was limited by vendor specific codes, whereas IEC 61850 enabled interoperability through a common language and file format called SCL.