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1. (In Total 10 Points) Three zones of a single-phase circuit a below. The zones are connected by transformers T1 and T2 (single phase transformers), whose ratings are also shown. Using base values of 7.50 kVA and 120 V in Zone Two (2), draw the per-unit circuit and determine the per-unit impedances and the per-unit source voltage. Then calculate the load current both in per-unit and in amperes. Transformer winding resistances and shunt admittance branches are neglected-(10.0 points). Zone 1 Zone 2 Zone 3 V, = 220/0° volts T₁ 30 KVA 240/480 volts Xeq = 0.10 p.u. Xane -20 Zload = 0.9 +/0.20 T₂ 20 KVA 460/115 volts Xea = 0.10 p.u.
2. (In Total 10 Points) Figure below shows the one-line diagram of a three-phase power system. By selecting a common base of 1,000 MVA and 11 kV on the motor side (shown by an "M"), draw an impedance diagram showing all impedances including the load impedance (in series) in per-unit. The data are given as follows: G: T₁: T₂: T3: T4: M: 66.5 MVA Lines 1 and 2 have series reactances of 48.4 2 and 65.43 92, respectively. At bus 4, the three-phase load absorbs 57 MVA at 10.45 kV and 0.6 power factor lagging (20.0 Points). G 90 MVA 50 MVA 40 MVA 40 MVA 40 MVA T3 В Your Answer to Question #2: 5 22 kV 22/220 kV 220/11 kV x x 22/110 kV x 110/11 kV x 10.45 kV Line 1 220 kV Line 2 110 kV x=0.180 per unit 0.100 per unit 0.060 per unit 0.064 per unit 0.080 per unit x=0.185 per unit 3 6 M Load