Development of Solutions for Automatic Calculation of Fault Current Protection in Highly Automated Zones of 6 – 35 kV Distribution Networks

Power transmission lines in distribution networks are equipped with two-stage current protection devices, the first stage being current cutoff, and the second stage being overcurrent protection. The operation of these devices with setpoints calculated in a conventional way does not always meet the sensitivity and selectivity requirements for relay protection. Therefore, there is a need to use additional technical solutions when designing and retrofitting distribution networks, including the introduction of distributed generators. Such a solution could be a centralized adaptive relay protection system that accounts for the possible changes in the topology and operating modes that affect the choice of the setpoints for relay protection. This system may be optimal for highly automated (digital) substations of electrical networks that use communication channels with all control elements, including relay protection. The current level of observability makes it possible to prevent conditions in which relay protection ceases to meet the sensitivity and selectivity requirements. A feature of the proposed solution is the preliminary calculation of most setpoint groups. In the case of change in topology and operating modes, new groups of setpoints are transmitted in real time. Real-time calculations are only carried out when modes that have been ignored at the preliminary stage occur.