In this paper several Under Frequency Load Shedding (UFLS) schemes are designed as special protection schemes to preserve the integrity of islands, formed following the outage of tie lines connecting two areas in a double area power system. For the purpose of analysis, the Iranian interconnected grid is simulated in a suitable power system analysis software. The grid is connected to the Khorasan province network, the greatest province of the country, through a double circuit tie line. Following

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... the outage of tie lines in a double area power system the area with great import of power may face large deficiency of energy and consequently blackout may occur in the island. The purpose of this research work is to propose a special protection scheme, being capable of preserving the balance of generation and consumption in order to prevent major outage. Special types of adaptive UFLS scheme are proposed in this work.