Open power market in Nordic countries like Finland, Sweden, Norway and Denmark has increased demand of interconnecting among EMSs (Energy Management Systems) and other power related systems. The concept of Nordic power market is seen as state-of-the-art model which has combined the physical quality of electricity and free power markets. Efficient functioning within power markets and optimizing the power transmission network inside the market area has lead to standardization of the data communication protocols. The aim of this study was to find out currently used interconnecting methods and protocols among EMS, SCADA (Supervisory Control And Data Acquisition) and other power related ICT(Information and Communication technology)-systems used in electricity supply chain in Finland. This paper also reviews the topical challenges faced in protocol implementations and future development plans for EDI (Electronic Data Interchange)-protocols. Finland is the part of Nordic power market area, we have also examined the other protocols as used in Nordic area. In such a perspective, we have presented a comprehensive overview of external data communications and major protocols as used in enterprise architecture of power and energy management systems in Finland.