This thesis has been made for VEO Oy. The purpose of the thesis is to introduce available implementation alternatives for 110 kV digital substation and effects of digitalization in substation projects costs. To achieve the concept of digital substation is opened with scientific literature and applicable standards. In short it means a substation where all communication between devices is done by IEC 61850 station- and process bus. For this thesis process bus is more important. First a closer look at digital substations structure is taken and necessary components to achieve digital substation are introduced. For implementation purposes thesis introduces devices found from today’s markets for digital substation are introduced. With this study it can be said that digital substation is achievable with current devices. Thesis introduces effects of digitalization in substations project costs compared to conventional substation. From the study cost reductions in favor of digital substation pro-jects can be seen. Especially moving from conventional hard wired copper wires to optical fibres in communication can introduce big savings on costs. Total cabling will be re-duced due to optic fibers with higher bandwidth compared to copper wiring. This reduces costs on materials, building and engineering. Most importantly couple implementation alternatives for digital substation with process bus are introduced. In fully digital substation implementation all of communication inside substation is done digitally using station- and process bus. To achieve this use of non-conventional instrument transformers is required. Other introduced implementation is using conventional instrument transformers with stand-alone merging units. Stand-alone merging units are used to digitize analogue signal from the conventional instrument transformer and to act as point of entry to process bus.