Upgrade of nuclear power plant I&C systems by using digital technology has been implemented to overcome the obsolescence of existing equipment and improve plant availability in many advanced countries. For upgrade of the Plant Protection System(PPS) based on conventional analog technology in the UCN 3&4 and YGN 5&6, French modernized Digital Integrated Protection System(DIPS) with proven technology is reviewed and evaluated for the adaptability into PPS. This paper contains the results of feasibility study for the design of digital PPS using French DIPS technology. Based on the results of evaluations, the system architecture of digital PPS is designed and described.