Pe power electrical engineering sample exam 13 35

PE Power Electrical Engineering Sample Exam
13
35. Figure 35 shows a synchronous generator connected to a synchronous
motor by a transmission line. Base values are 10 MVA, 12 kV.
The motor voltage, VM , is 1 pu and the current, IM , is 1.1 pu at a leading
power factor of 0.8. A symmetrical three-phase fault occurs at the terminals
of the motor. The contribution of the fault current from the generator in kA
is nearly:
a. 1.92
b. 1.03
c. 0.78
d. 0.39
36. Consider this set of unbalanced, three-phase currents:
/ = 125 Z50° amps
/” = 95 Z10° amps
/ = 150 Z-110° amps
I , the positive-sequence component, is nearly:
37. Positive-sequence and negative-sequence components of the line-to-line
voltage of a wye-connected load, V b are specified as 115Z-15° and
30Z1050, respectively. The phase voltage |V| is nearly:
38. The positive-, negative-, and zero-sequence reactances of a 40 MVA, 20
kV synchronous generator are 0.45 pu, 0.25 pu, and 0.10 pu, respectively.
The generator is solidly grounded and is not loaded when a line-to-
ground fault occurs on phase a. (Neglect all the resistances.) The fault
current I in kA is nearly:

14
Chapter 1 Morning Exam Questions
39. The positive-, negative-, and zero-sequence reactances of a 40 MVA,
20 kV synchronous generator are 0.45 pu, 0.25 pu, and 0.10 pu, respec-
tively. The generator is solidly grounded and is not loaded when a line-
to-line fault occurs between phases
b and c. (Neglect all the resistances.)
Fault current in kA is nearly:
a.
b. 1.27
c. 2.86
d. 3.47
0
40. The positive-, negative-, and zero-sequence reactances of a 40 MVA, 20
kV synchronous generator are 0.45 pu, 0.25 pu, and 0.10 pu, respectively.
The generator is solidly grounded and is not loaded. Neglect all the resis-
tances. A double line-to-ground fault occurs between lines b and c and
ground. Fault current (in pu) is nearly:

C H A P T E R
Afternoon Exam
Questions
1. A systems application involves a multiwinding transformer as modeled in
Figure 1.
Figure 1
Vs = 20 volts, Rs = 50 ohms, N l = 100
R2 = 200 ohms, N2 = 200 R3 = 300 ohms, N3 =
Assuming an ideal transformer, the value of /, is nearly:
300