EPRI EXAM 4 QUESTIONS WITH CORRECT
ANSWERS!!
If a generator is producing 500 MW and 200 Mvar, is the generator? A. Leading B.
Lagging C. Underexcited D. Dropping
B. Lagging (Solve for phase angle, + is lagging, - is leading
What is the IEEE device number for a differential relay? A. 87 B. 86 C. 67 D. 50
A. 87 (See IEEE chart pg. 125)
Can a synchronous machine have a negative torque angle? What does this mean? A. Yes /
the machine is absorbing reactive power B. No / the machine is absorbing active power C.
No / the machine is absorbing reactive power D. Yes / the machine is absorbing active
power
D. Yes / the machine is absorbing active power (pg. 153)
A customer load is fed at 120 volts. The customer voltage is doubled while the load
magnitude stays the same. What effect does this have on the power losses? A. Doubles the
losses B. Halves the losses C. Increases the losses by a factor of four D. Decreases the losses
by a factor of four
D. Decreases the losses by a factor of four (combination of ohms law, active power equation, and
voltage drop across distribution systems pg.367)
In a DC circuit, a 100 volt battery is connected to both sides of a 2 ohm resistor. What is the
current through the resistor and the power usage of the resistor? A. 50 amps / 5000 watts
B. 40 amps / 80 watts C. 50 amps / 100 watts D. 40 amps / 3200 watts
A. 50 amps / 5000 watts (ohms law & watts law)
The actual voltage is 362 kV on a 345 kV bus. What is the p.u. voltage? A. 1.0 B. 1.05 C. 1.5
D. .95
B. 1.05 (Ratio of voltages)
, A load has a power factor of 0.9 lagging. If the load draws 100 MVA, what is the MW
draw? A. 100 B. 90 C. 111 D. 44
B. 90 MW (Power Factor Equation - (PF = Active / Complex)
Which of the following is NOT a synchronizing variable? A. Phase angle B. Frequency
difference C. Voltage magnitude difference D. MW flow differential
D. MW flow differential (pg. 138)
In a typical multi-stage steam turbine, the governor control valves control the steam entry
to the: A. high pressure turbine B. intermediate pressure turbine C. low pressure turbine
D. crossover
A. high pressure turbine (no idea, governor controls input? High pressure turbine is first?)
The high side of a delta-wye connected transformer is connected to a power system with
199 kV L-G high side voltage. What is the voltage across the winding of the delta
transformer? A. 199 kV B. 230 kV C. 345 kV D. 500 kV
C. 345 kV (Divide abcd by 199 for turns ratio. then 199+199+199 (delta wye has three
connections) / turns ratio solved in part 1 should equal answer. So = 1.73 (199*3)/1.73
= 345
What does the voltage angle represent?
The amount by which a voltage sine wave has shifted left or right with respect to a reference
What does the phase angle represent at a point in a power system?
It is the angular separation between the current and the voltage waves.
The power angle is the...? What greek letter represents it?
voltage angle between two locations in the power system. The power angle is represented by the
Greek letter delta.
A rule of thumb is that active power flows __________ on power angle?
downhill
ANSWERS!!
If a generator is producing 500 MW and 200 Mvar, is the generator? A. Leading B.
Lagging C. Underexcited D. Dropping
B. Lagging (Solve for phase angle, + is lagging, - is leading
What is the IEEE device number for a differential relay? A. 87 B. 86 C. 67 D. 50
A. 87 (See IEEE chart pg. 125)
Can a synchronous machine have a negative torque angle? What does this mean? A. Yes /
the machine is absorbing reactive power B. No / the machine is absorbing active power C.
No / the machine is absorbing reactive power D. Yes / the machine is absorbing active
power
D. Yes / the machine is absorbing active power (pg. 153)
A customer load is fed at 120 volts. The customer voltage is doubled while the load
magnitude stays the same. What effect does this have on the power losses? A. Doubles the
losses B. Halves the losses C. Increases the losses by a factor of four D. Decreases the losses
by a factor of four
D. Decreases the losses by a factor of four (combination of ohms law, active power equation, and
voltage drop across distribution systems pg.367)
In a DC circuit, a 100 volt battery is connected to both sides of a 2 ohm resistor. What is the
current through the resistor and the power usage of the resistor? A. 50 amps / 5000 watts
B. 40 amps / 80 watts C. 50 amps / 100 watts D. 40 amps / 3200 watts
A. 50 amps / 5000 watts (ohms law & watts law)
The actual voltage is 362 kV on a 345 kV bus. What is the p.u. voltage? A. 1.0 B. 1.05 C. 1.5
D. .95
B. 1.05 (Ratio of voltages)
, A load has a power factor of 0.9 lagging. If the load draws 100 MVA, what is the MW
draw? A. 100 B. 90 C. 111 D. 44
B. 90 MW (Power Factor Equation - (PF = Active / Complex)
Which of the following is NOT a synchronizing variable? A. Phase angle B. Frequency
difference C. Voltage magnitude difference D. MW flow differential
D. MW flow differential (pg. 138)
In a typical multi-stage steam turbine, the governor control valves control the steam entry
to the: A. high pressure turbine B. intermediate pressure turbine C. low pressure turbine
D. crossover
A. high pressure turbine (no idea, governor controls input? High pressure turbine is first?)
The high side of a delta-wye connected transformer is connected to a power system with
199 kV L-G high side voltage. What is the voltage across the winding of the delta
transformer? A. 199 kV B. 230 kV C. 345 kV D. 500 kV
C. 345 kV (Divide abcd by 199 for turns ratio. then 199+199+199 (delta wye has three
connections) / turns ratio solved in part 1 should equal answer. So = 1.73 (199*3)/1.73
= 345
What does the voltage angle represent?
The amount by which a voltage sine wave has shifted left or right with respect to a reference
What does the phase angle represent at a point in a power system?
It is the angular separation between the current and the voltage waves.
The power angle is the...? What greek letter represents it?
voltage angle between two locations in the power system. The power angle is represented by the
Greek letter delta.
A rule of thumb is that active power flows __________ on power angle?
downhill
