A Solved problem to draw the per unit Reactance Diagram

Draw the per unit reactance diagram for the power systems shown below. Neglect resistance and use a base of 100MVA, 220KV in 50 ohms line. The ratings of the generator, motor and transformers are

G: 40 MVA, 25 KV, X’’ = 20%; M: 50 MVA, 11 KV, X’’ = 30%

T₁:40 MVA, 33 Y / 220 Y KV, X = 15%; T₂: 30 MVA, 11 Δ /220Y KV, X = 15%

Load: 11 KV, 50MW + j68 MVAR

Solution:

Base MVA_{b new} = 100 MVA; Base KV_{b new} = 220 KV

Transmission line j50 Ω:

Z_actual = j50 Ω

Transformer T₁:

KV_{b old} = 220 KV

Generator G₁:

Transformer T₂:

KV_{b old} = 220 KV (HT side voltage)

Synchronous motor:

Reactance diagram: