EEL 5250 Power Systems Analysis, Fall 2016Homework
Q1. The transformers shown in Fig. 1 are labeled in a nonstandard manner. Assume that the 1φ transformers are ideal (each with voltage gain n) and find the positive sequence per phase equivalent circuit relating V¯ a'n', to V¯an.
Q2. Given the strange connection of 1φ transformers shown in Fig. 2, assume E¯a = E¯b = E¯c = 1∠0o and find I¯a.
Q3. Draw an impedance diagram for the system shown in Fig. 3. The 3φ and line-line ratings are as follows:
Generator G1: 50 MVA 13.8 kV X = 0.15 pu
Generator G2: 20 MVA 14.4 kV X = 0.15 pu
Motor M: 20 MVA 14.4 kV X = 0.15 pu
T1: 60 MVA 13.2-161 kV, X = 0.10 pu
T2: 25 MVA 13.2-161 kV, X = 0.10 pu
T3: 25 MVA 13.2-161 kV, X = 0.10 pu
Line 1: 20 + j80 ?
Line 2: 10 + j40 ?
Line 3: 10 + j40 ?
Load: 20 + j15 MVA at 12.63 kV
Q4. The 765-kV 3φ line is 400 mile long and delivers 100 MW at 750 kV at 95% power factor lagging. Find the sending-end voltage and current and the transmission efficiency. Use the long-line model. Series impedance z = 0.02 + j0.54?/mi, shunt admittance y = j7.8 × 10-6 mho/mi.
Q5. In Fig. 4, assume that V1 = V2 = 1 and Zline = 0.1∠85o.
- For what nonzero θ12 is S12 purely real?
- What is the maximum power, -P21, that can be received by V¯2, and at what θ12 does this occur?
- when θ12 = 85o, what is the active power loss in the line?
- For what θ12 is -P21 = 1?
Q6. Find the surge impedance loading for the 765 kV 3φ line in (4). Assume the line is lossless and the series impedance is z = j0.54?/mile. Also make judgement of true or false for the following statements:
1) At surge impedance loading level, the transmission line neither absorbs reactive power nor sends out reactive power.
2) At surge impedance loading level, voltage phasors along the line differ only in phase angles.
This is the homework with chapters subject is power system please solve step by step that I can understand.