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Unit III Practice QuestionsQ1. Draw the positive, negative and zero sequence impedance networks for the power system given...
Q3. Draw the positive, negative and zero sequence impedance networks for the power system given in    the figure. Choose a...
Q5. Draw the positive, negative and zero sequence impedance networks for the power system given in     the figure. Choose ...
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Questions unit3

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Sequence networks

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  1. 1. Unit III Practice QuestionsQ1. Draw the positive, negative and zero sequence impedance networks for the power system given in the figure. Choose a base of 50 MVA, 220kV in the 100 ohms transmission line and mark all impedances in pu. The ratings of the generators and transformers are: Generator 1: 25 MVA, 11kV, X1=20%; X2=20%; Generator 2: 25 MVA, 11kV, X1=20%; X2=20%; Three-phase transformer (each): 20MVA, 11 Y/220 Y kV, X=15%. The zero sequence reactance of each machine is 8%. The neutral reactance is 5% on individual machine ratings.Q2. Draw the positive, negative and zero sequence impedance networks for the power system given in the figure. Choose a base of 50 MVA, 220kV in the 50Ω transmission lines and mark all impedances in pu. The ratings of the generators and transformers are: Generator 1: 25 MVA, 11kV, X1=X2=20%, Xg0 = 10% Generator 2: 25 MVA, 11kV, X1=X2=15%, Xg0 = 8% Three-phase transformer (each): 20MVA, 11 Y/220 Y kV, X=15% The zero sequence reactance of each machine is 8%. Assume that the zero sequence reactance of the lines is 250% of their positive sequence reactance.
  2. 2. Q3. Draw the positive, negative and zero sequence impedance networks for the power system given in the figure. Choose a base of 100 MVA, 200kV in the 100 ohms transmission line and mark all impedances in pu. The ratings of the generators, transformers are: G1: 20 MVA, 11kV, X1=20%; X2=10%; G2: 50 MVA, 33kV, X1=20%; X2=15%; YY Transformer: 50MVA, 200/11KV, X= 10%; Y∆ Transformer: 45MVA, 200/33KV, X = 15%. The zero sequence reactance of each machine is 5%. The neutral reactance is 3% on individual machine ratings.Q4. Draw all the sequence networks for the power system shown in the figure below: Choose a base of 50 MVA, 220KV in the 50 ohm transmission lines and mark all the reactances in pu. The ratings of the generators and the transformers are: Generator 1 : 25MVA, 11KV, X1=X2=15%, Xg0 = 5% Generator 2 : 25MVA, 11KV, X1=X2=10%, Xg0 = 8% 3 phase transformers(each) = 20 MVA, 11 /220 KV, X = 15% The negative sequence reactance of each synchronous machine is equal to its positive seq. reactance. The zero sequence reactance of each machine is 8%. The neutral reactance is 5%.
  3. 3. Q5. Draw the positive, negative and zero sequence impedance networks for the power system given in the figure. Choose a base of 150 MVA, 220kV in the 60 ohms transmission line and mark all impedances in pu. The ratings of the generators, transformers are: G1: 50 MVA, 13kV, X1=25%; X2=15%; G2: 40 MVA, 25kV, X 1=15%; X2=10%; YY Transformer: 45MVA, 220/15KV, X= 15%; Y∆ Transformer: 50MVA, 230/35KV, X = 10%.The zero sequence reactanceof each machine is 4%.The neutral reactance is 5%on individual machine ratings.

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