The invention relates to high and medium voltage networks and substations. The network is formed by a transmission line with power system elements connected to its terminal buses as well as by a simplified connection that is located in the transmission line, with one high-voltage circuit-breaker. On the first and the second buses, protection terminals are installed, but at the place of the simplified connection, in addition to the relay protection, a verification device is installed, which monitors the operability of the communication channel(-s) and the local protection device. This verification device operates in cases when different failures occur in the communication system and in the local protection device. Also in the case when a failure occurs in the verification device, the local protection device emits a pulse and the circuit breaker is switched off. To diminish the total investment in the new connection, maintaining the required accuracy and selectivity of relay protection, the offered new solution of relay protection device is provided with an additional verification device, which continuously monitors the condition of the communication system and the local protection.