An equivalent scheme of the Baltic power system integrated with power unification (ENTSO-E) is proposed. The general model of the synchronously operating the extended power unification ENTSO-E allows transmission system operators (TSO) to monitor each possible (emergency) state of the EPS for the admissibility of the electrical regime in their area of responsibility. The results of specific studies for various scenarios of changes in renewable energy generation are presented. It seems that the proposed model of the Baltic energy system (Lithuania, Latvia and Estonia) can be used to determine the acceptable value of the RES generated capacity share in the total generation, which does not affect on the reliability of EPS entire power unit.