Power systems are permanently with failures risk, caused by electrical faults, human mistakes, harmonic component, flickers, among others. At the operational level, the impact of the incorrect operations of the “Protection Systems” in faults clearing has been documented, different studies cases of electrical failures not detected or not desired in a timely manner, they have led to the disconnection of the load of entire regions and even the total collapse of an electrical system. The foregoing is evident that the adequate selection of protection systems favors the reliable and safety operation of the grid. This paper introduces a novel methodology for the selection of protection systems for transmission lines, in the “Peruvian National Interconnected Electric System”. This methodology was structured for the revision of regulatory parameters related to the characteristics and “performance” of the protection systems and the technical aspects such as the redundancy of the “protection system”, the SIR estimation (source impedance ratio) and critical fault clearance times. Finally, the methodology studied in the Expansion Plan for Perú for the years 2019-2028, by means of electrical analysis, which allowed determining the way to have the characteristics of the protection systems of the new national grid expansion projects.