The Line Flow indices are divided into five categories using Fuzzy Set 

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notations: very small index (VS), small index (S), medium index (M), high index (H), and very high index (VH). Fig. 5 shows the correspondence between the Line Flow index and the five linguistic variables. Fig. 6 shows the severity index for voltage profile and Line Flow index. 

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The fuzzy rules, which are used for evaluation of severity indices of bus voltage profiles and line flow indices, are given in Table 1. 

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The Criticality Index is obtained by adding the two severity indices as shown in Fig. 7. The Criticality Index is obtained at critical load for all the load buses. 

The buses are ranked in decreasing order of Criticality Index. 

The following are the steps involved in the approach: 