By the unbalanced concentration of transmission lines in recent years, the occurrences of multiple facility faults have become a great concern for sub-transmission power systems. In this paper, the problem of multiple facility faults is dealt with quantitatively. We use outage power and outage electric energy as the reliability indices. By the use of these indices the scale of a fault and the time required for the restoration are evaluated. In sub-transmission power systems, the number of the system composition is large. Therefore it is difficult to find an optimal system composition and a restoration procedure. In this paper, we introduce the tabu search method and the cluster analysis in order to find a solution easily. We simulate the proposed method by using an IEEJ sub-transmission system model (a 66 kV suburban system) in order to verify the validity of the proposed method