An intelligent protection scheme to deal with extreme fault currents in smart power systems

In modern power systems, the generation capacity is increasing significantly for responding to high electric energy demands. This generation expansion directly affects the level of short circuit in transmission systems and increases the fault current magnitude, which may pass the breaking capacity of circuit breakers. To deal with extreme fault currents in power systems, an intelligent protection scheme is proposed in this paper, which removes the necessity of installing expensive fault current limiters. This protection scheme uses communication capabilities defined in IEC 61850 to design smart cascading switching actions to isolate the faulty part of the system. In fact, it is a supervisory protection algorithm in addition to the conventional distance protection, which is the main protection of HV transmission systems. This protection is activated if the fault current is higher than breaking capacity of circuit breakers; otherwise, the conventional distance protection is responsible to clear the fault. Numerical results obtained from implementing the proposed protection algorithm in a 400 kV system demonstrate the effectiveness of this method in terms of fault clearing time, stability margin improvement and power system economy.