- 2069 Bhadra · 6 marks
Reactance diagram of eight-bus system
Short answer
Base 10 MVA, 11 kV generator side, 66 kV lines. Per-unit reactances: X_G1 = X_G2 = 0.1093, X_G3 = 0.0874, X_T1 = X_T2 = X_T3 = 0.10, X_T4 = 0.0514, each line 0.0459 pu. Motor reactance is unspecified.
Construct a reactance diagram for the system given below and express all the reactances in per unit system. G1, G2: 10 MVA, 11.5 kV, 10%; G3: 15 MVA, 11.5 kV, 12%; T1, T2: 10 MVA, 11/66 kV, 10%; T3: 15 MVA, 11/66, 15%; T4: 35 MVA, 66/11 kV, 18%; L1 = L2 = L3 = L4 = j20 Ω/ph. [Figure: G1 (bus 1) → T1 → bus 2; G2 (bus 3) → T2 → bus 4; line L2 from bus 2 to bus 6, L1 from bus 2 to bus 4, L3 from bus 4 to bus 7, L4 from bus 6 to bus 7; T3 between bus 6 and bus 5 feeding G3; T4 between bus 7 and bus 8 feeding motor M (no motor rating printed).]
Choice of base: 10 MVA, with 11 kV in the generator circuits (the transformer LV rating) and 66 kV on the lines. The motor rating is not printed, so its reactance is left as (pu on its own rating). Its value on the common base is .
Per-unit reactances (10 MVA base)
| Element | X (pu, 10 MVA) |
|---|---|
| G1, G2 | 0.1093 each |
| G3 | 0.0874 |
| T1, T2 | 0.1000 each |
| T3 | 0.1000 |
| T4 | 0.0514 |
| L1 to L4 | 0.0459 each |
Reactance diagram
(E1)-j0.1093-[1]-j0.10-[2]---j0.0459(L2)---[6]
| |
j0.0459(L1) j0.0459(L4)
| |
(E2)-j0.1093-[3]-j0.10-[4]---j0.0459(L3)---[7]
[6]-j0.10(T3)-[5]-j0.0874-(E3)
[7]-j0.0514(T4)-[8]-jXM-(Em)
All sources (E1, E2, E3, Em) return to the
common reference (neutral) bus.
Answer: On 10 MVA (11 kV / 66 kV bases): , , , , and each line 0.0459 pu.
✓ Answer checked by Claude Opus 5.5 (high effort)
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