Question-2 [40 Points] For the system shown in Figure. 2, directional overcurrent relays are used at breakers B12, B21, B23, B32, B34, and B43. Overcurrent relays alone are used at B1 and B4. (a) For a fault at P1, which breakers do not operate? Which breakers should be coordinated? Repeat (a) for a fault at (b) P2, (c) P3. (d) Explain how the system is protected against bus faults i.e. mention the breakers that operate for the bus faults. B1 B12 Load L1 P₂ B21 0 2 B23 0 Load L2 P₂ 3 B32 834 0 P₁ Load L3 Figure. 2: Oneline Diagram of a Radial System B43 B4 口 Load L4

Fig: 1