Concept:
For a synchronous generator,
E = V + IaZs
Explanation:
Given that,
Xs = 0.8 pu, P = 1.0 pu, upf
V = 1.1 pu, Ra = 0
Power of a non-salient pole synchronous generator can be defined as P = VIa cos ϕ
1 = 1.11 × Ia × 1
Ia = 0.91 pu
E = V + IaZs
= 1.11∠0 + 0.91 ∠0 × 0.8 ∠90°
= 1.319 ∠33.49
The required angle = 33.49°