(Solved): Question 4 (20 MARKS) a. A grounding reactor is to be applied in the system shown in Figure 3 to l ...

Question 4 (20 MARKS) a. A grounding reactor is to be applied in the system shown in Figure 3 to limit the maximum line to ground fault current to \( 400 \mathrm{~A} \) at point \( \mathrm{F} \). Figure 3 Using a 20 MVA base, determine in per unit form: i. Source positive and negative sequence reactance (4 marks) ii. System total zero, positive and negative sequence reactances (3 marks) iii. Sequence currents for a line to ground fault (3 marks) iv. Value of grounding reactor (2 marks) b. If the transformer bank is solidly grounded, determine in pu form: i. Sequence currents (3 marks) ii. Current in phase "a" (2 marks) iii. Positive sequence current for a three-phase fault at ' \( \mathrm{F} \) ' (3 marks)