The document contains 5 practice questions asking to draw the positive, negative, and zero sequence impedance networks for various power system configurations. Information provided includes generator and transformer ratings, line impedances, and zero/neutral sequence reactance values. The questions require calculating and representing the sequence networks using per unit values with various bases related to the system ratings.

1. Unit III Practice Questions
Q1. 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. 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. 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 reactance
of each machine is 4%.
The neutral reactance is 5%
on individual machine ratings.