All the questions are related to the operation and control of an isolated system whose one- line diagram is given below.
1 2 Gen 1, 2,3
69 kV, 50 MVA
Xg = 0.05 pu
lines are identical with z = j 0.002 pu/mi; b = 0.005 pu/mi
TR: 100 MVA, x= 0.05 pu Sb = 50 MVA
Vb = 69 kV at bus 1
The generators each has M = 100 MW.sec. and is equipped with a governor with a droop range of 0.5
- 5%. The load has Dwo = 0.2 MW.
A basic model for the power-frequency control loop for the generators is given below.
Q1 (30) You are asked to do contingency screening for this system.
During the peak load condition the operating point is determined as follows:
V = 1.0000/0o 1.0000/3.2727o 0.9819/-1.4006o 0.9332/-7.6657o pu
i) Determine if the line from bus 1 to 2 is overloaded in this case. The line has 50 MVA loading limit. Use pi equivalent model.
ii) What would you do to boost the voltage at bus 4?
Suggest two solutions, and point out which one is a better choice in one-two sentences.
Q2 (35) You are asked to analyze the power-frequency variations in case of a loss of a generator.
i) (10) Draw a simplified power-frequency block diagram dynamic model of this system. You can neglect the line dynamics.