
| 2-3    | 4.71   | 4.71   | 4.71   |
|--------|--------|--------|--------|
| 2-4    | 4.71   | 4.71   | 4.71   |
| 2-5    | 4.71   | 4.71   | 4.71   |
| 3-4    | 13.50  | 4.71   | 4.71   |
| 4-5    | 41.90  | 39.60  | 29.40  |
| ∑ SILF | 82.99  | 69.71  | 68.65  |

Table-6 Criticality Index and Rank using Fuzzy Approach and FVSI 

| Bus no.   | CI=∑SIVP +∑SILF   | Rank   | FVSI   | Rank   |
|-----------|-------------------|--------|--------|--------|
| 3         | 194.990           | I      | 0.966  | I      |
| 4         | 170.210           | II     | 0.964  | II     |
| 5         | 166.250           | III    | 0.679  | III    |

From the results, it can be observed that bus number 3 is the most critical bus and bus number 5 is less critical. This indicates that at the verge of voltage instability or voltage collapse, it is the load at bus no. 3 to be monitored and controlled at the earliest. The result obtained from fuzzy approach is compared with Fast Voltage Stability Index (FVSI). The ranking from both the methods agree with each other. 

## B) Under Critical Line Outage Contingencies

For ranking the critical buses under line outage contingencies, both single line outage and double line outages are considered. On screening, 12 critical line outages are considered. Under these line outages, the load buses are ranked. 

| Bus No. 3   | Bus No. 4   | Bus No. 5   |             |      |             |      |
|-------------|-------------|-------------|-------------|------|-------------|------|
| Contingency | Criticality | Rank        | Criticality | Rank | Criticality | Rank |
| Index       | Index       | Index       |             |      |             |      |
| 1-2         | 108.60      | I           | 106         | II   | 97.70       | III  |
| 2-5         | 119.40      | I           | 116.9       | II   | 89.60       | III  |
| 1-2,2-3     | 108.20      | I           | 108.2       | II   | 104.00      | III  |
| 2-3,2-5     | 114.00      | I           | 114         | I    | 109.80      | II   |
| 2-5,3-4     | 104.00      | I           | 95.52       | II   | 85.59       | III  |
