These practice questions are meant to guide the Power4Vets student through studying the
fundamentals of power system dynamics. This is meant for students without a strong electrical
background, or for those who would like to brush up on their knowledge. By reading the related
sections in EPRI Power System Dynamics Tutorial and completing the following practice questions,
students will be better prepared to take the Power Systems Operator and Control (PSOC) Simulation
training.
1. Ensure you have the EPRI Power System Dynamics Tutorial –
see Power4Vets downloads page online: link (.pdf, 71mb)
2. Study following sections of the EPRI Power System Dynamics Tutorial:
 2.2 Mathematics
 2.3 DC Electricity Review
 2.4 AC Electricity Review
 2.6 Power System Equipment
 3.1 - 3.2 Active and Reactive Power
3. Use the Practice Questions in the next section to guide your studies
4. Answer Key for Practice Questions:
The answer key is available at the end of the practice questions.
Right triangles
Which of the following is true about a Right Triangle in mathematics?
a) There are more than 3 sides
b) One of its angles equals 90 degrees
c) The hypotenuse is always the longest side of the triangle
d) Both B and C
The sum of the angles in a triangle always equals ______ degrees.
a) 0
b) 90
c) 180
d) 360
(Not drawn to scale)
Use the above diagram to answer the next 5 questions:
What is Angle C?
a) 45 degrees
b) 90 degrees
c) 120 degrees
d) 180 degrees
If angle A = 35 degrees, what is angle B?
a) 15 degrees
b) 55 degrees
c) 85 degrees
d) 170 degrees
© 2013 IncSys – Not Distributable Without Permission
If angle B = 56 degrees, what is angle A?
a) 34 degrees
b) 44 degrees
c) 114 degrees
d) 184 degrees
If side b = 4 and side a = 3, what is the length of side c?
If side c = 10 and side b = 8, what is the length of side a?
Trigonometric Functions
One period of a sine function is equivalent to how many degrees?
a) 90
b) 180
c) 360
d) There is not enough information
The magnitude of a sine wave at 80 degrees will be equal to the magnitude at ______.
a) 440 degrees
b) 180 degrees
c) 350 degrees
d) -10 degrees
Use the following figure to answer the next 6 questions.
How do you calculate the sine of angle A?
How do you calculate the sine of angle B?
© 2013 IncSys – Not Distributable Without Permission
If a=3, b=4, and c=5, what is the sine of angle A?
If a=3, b=4, and c=5, what is the sine of angle B?
It is given that Side c=10 and Side a = 6. Find Side b, Angle A, and Angle B. (Hint: follow the
example on page 79 of the dynamics tutorial)
It is given that Side b = 12 and Side a = 5. Find Side c, Angle A, and Angle B.
Use of Ratios
Which of the following is an example of a ratio?
a) A fraction
b) A percentage
c) An hypotenuse
d) Both (a) and (b)
Assume a given generator unit has a maximum output of 800MW.
What percentage of the unit’s capacity is occupied when it is producing 600MW?
a) 20%
b) 40%
c) 75%
d) 100%
Which of the following fractions corresponds to 80%?
a) 8/10
b) 8/100
c) 80/10
d) 800/10
© 2013 IncSys – Not Distributable Without Permission
Which of the following percentages corresponds to the fraction “2/5”?
a) 20%
b) 25%
c) 30%
d) 40%
From prior experience, you know that a loss of a 1500 MW generator unit in a given system
results in a 0.3 HZ dip in system frequency. What frequency dip would result from the loss of a
1000 MW unit?
a) 0.1 HZ
b) 0.2 HZ
c) 0.3 HZ
d) None of the above
It is known by experience that a loss of a 1200 MW unit in a given system results in a 0.1 HZ dip
in system frequency. Today, a fully loaded generator unit in your system tripped off, resulting
in a 0.08 HZ dip in system frequency. What is the maximum MW output of this generator?
a) 800
b) 920
c) 960
d) 1000
Per-Unit values
Suppose the voltage at a 345 kV bus is measured as 355 kV. Which of the following is closest to
the per-unit voltage?
a) 0.85
b) 0.97
c) 1.03
d) 1.15
Suppose the per-unit voltage at a 115 kV bus is measured as 0.92. Which of the following is
closest to the actual voltage?
a) 92.9
b) 105.8
c) 115
d) 120.5
Suppose the voltage at a 12 kV bus is measured as 18 kV. What is the per-unit voltage?
a) 1.2
b) 1.4
c) 1.5
d) 1.6
© 2013 IncSys – Not Distributable Without Permission
Suppose the per-unit voltage at a 34.5 kV bus is measured as 1.24. Which of the following is
closest to the actual voltage?
a) 12.4
b) 27.8
c) 34.5
d) 42.8
For the following three questions, suppose a 138kV to 345kV transformer with a 105 MVA
Rating has a 7% impedance at a given moment.
1. What is the per-unit impedance? ______ p.u.
2. Calculate the base impedance for the high side (345kV) ________ Ohms
3. Calculate the base impedance for the low side (138kV) ________ Ohms
4. Calculate the Actual Ohms on the high side base ________ Ohms
5. Calculate the Actual Ohms on the low side base _________ Ohms
Current
What is the unit of measurement of electric current?
a) Coulon
b) Hertz
c) Ampere
d) Volts
Current is measured as an amount of _________ passing through a cross section of a conductor
over time.
a) Charge
b) Voltage
c) Electrical Power
d) None of the above
True or false: electrons in a conductor require a force to cause a current flow to occur.
a) True
b) False
Choose the answer which completes the following sentence. Electrons are _______ charged.
a) Positively
b) Negatively
c) Neutrally
d) (None of the above)
© 2013 IncSys – Not Distributable Without Permission
Resistance
Resistance uses the same unit of measurement as which of the following?
a) Current
b) Voltage
c) Impedance
d) Reactance
Conductor A has twice the resistivity of conductor B. Which is the better conductor?
Which of the following factors affects the resistance for a given conductor?
a) Length of the conductor
b) Type of conductor material
c) The voltage drop across the conductor
d) Both A and B
Use the following image of Circuit segments A and B to answer the next 2 questions.
Assume that R1 = R2. Which circuit will allow more current flow from left to right?
Assume that R1 = R2. Which circuit has more total resistance?
The letter “I” in electrical formulas usually represents ______?
a) Inductance
b) Voltage
c) Current
d) Impedance
Voltage
True or false: electrons in a conductor require voltage to cause a current flow to occur.
a) True
b) False
© 2013 IncSys – Not Distributable Without Permission
Voltage is the ___________ that results in a potential for current flow.
a) Electromagnetic Pulse
b) Locomotive Force
c) Separation of charge
d) Distance between each electron
Which of the following is NOT an example of a voltage source?
a) Battery
b) Generator
c) Voltmeter
d) None of the above
Which of the following is NOT an example of where Measured Voltage can be taken?
a) Between two phases of a transmission line
b) From phase to ground
c) From ground to ground
d) None of the above
Which of the following is NOT true about voltage?
a) It is the distance between two separated charges
b) It is the electromotive force that causes current flow in a conductor
c) It is also known as potential difference.
d) Its unit of measurement is the volt
Which of the following devices maintains a voltage difference (EMF) between its terminals?
a) Circuit Breaker
b) Autotransformer
c) Voltage source
d) Voltmeter
Electrical Circuits
In which of the following types of circuits does voltage and current remain at a constant level?
a) Parallel Circuit
b) DC Circuit
c) AC Circuit
d) Series Circuit
Which of the following is an example of a voltage source for a direct current circuit?
a) Battery
b) Generator
c) Alternator
d) None of the above
© 2013 IncSys – Not Distributable Without Permission
Ohm’s Law
Which of the following is the Ohm’s Law?
a) V=IR
b) P=VI
c) E=MC
d) I=CE
If 6 amps flows through .6 Ohms of resistance, what is the voltage in volts?
If the current in a 8 volt circuit is 10 amps, what is the resistance in ohms?
In a simple electrical circuit with a 12 volt supply and a 24 ohm resistor, current is ____ amps
Kirchoff’s Laws
The total resistance of a series circuit containing three 5-ohm resistors is ______ ohms.
The total resistance of a parallel circuit containing two 10-ohm resistors is ______ ohms.
The total resistance of a series circuit containing four 25-ohm resistors is ______ ohms.
The total resistance of a parallel circuit containing six 4.5-ohm resistors is ______ ohms.
© 2013 IncSys – Not Distributable Without Permission
Use the above image to answer the following 6 questions:
True or false: R1 and R2 are in parallel.
What is the source voltage (in volts)?
What is the source current (in amps)?
What is the total resistance (in ohms)?
What is the voltage drop across R1 (in volts)?
What is the voltage drop across R2 (in volts)?
Power and Energy
Which of the following is the DC Power equation?
e) V=IR
f) P=VI
g) E=MC
h) I=CE
© 2013 IncSys – Not Distributable Without Permission
Which of the following is NOT a correct way to rearrange the DC Power equation?
a) P=VI
b) V=P/I
c) I=P/V
d) I=V/P
Power in a simple 12 volt, 4 amp DC series circuit is _____.
a) 8 W
b) 3 W
c) 16 W
d) 48 W
Power in a simple 15 volt, 3 amp DC series circuit is _____.
a) 12 W
b) 18 W
c) 45 W
d) None of the above
Current in a simple 12 volt, 60W series circuit is_______.
a) 5 amp
b) 6 amp
c) 10 amp
d) 12 amp
Alternating Current Systems
Each phase in a 3-phase AC system is _____________ degrees out of phase with the other two
phases.
a) 0
b) 30
c) 90
d) 120
© 2013 IncSys – Not Distributable Without Permission
What is the amplitude of the above sine wave?
If in the above image, x = 10 seconds, what is the period (in seconds) of this sine wave?
When the sine waves of both current and voltage peak at the same, this is known as ______.
a) Current is lagging voltage
b) Current is leading voltage
c) Current is in phase with voltage
d) None of the above
The magnitude of a sine function is maximized at __________?
a) 0 degrees
b) 45 degrees
c) 90 degrees
d) 180 degrees
The magnitude of a sine function is minimized at __________?
a) 0 degrees
b) 45 degrees
c) 90 degrees
d) 180 degrees
If current leads voltage then _________ reacts more quickly to changes than _________?
a) voltage; current
b) current; voltage
c) primary winding; secondary winding
d) generator; load
© 2013 IncSys – Not Distributable Without Permission
Magnetism and Magnetic Fields
Which of the following is the unit of measurement for inductance?
a) Ohm
b) Amp
c) Watt
d) Henry
Which of the following will increase the strength of the magnetic field in an electromagnet?
a) Increasing the distance between the poles
b) Increasing the turns of wire
c) Decreasing the turns of wire
d) Decreasing the number of magnetic poles
Magnetic flux lines go from the North Pole to the south pole of the magnet.
a) True
b) False
A transformer turns ratio is ______ its current ratio.
a) Inversely related to
b) Not related to
c) Equal to
d) None of the Above
AC Power
Total opposition to current flow in an AC circuit with both resistance and reactance is called
_________.
a) Impedance
b) Inductance
c) Capacitance
d) MVA
Active power and reactive power are _______ degrees apart in phase
a) 0
b) 45
c) 90
d) 180
Using the power triangle, calculate the MVA when the MW and Mvar components are 3 and 4,
respectively.
a) 5 MVA
b) 7 MVA
c) 12 MVA
d) 25 MVA
© 2013 IncSys – Not Distributable Without Permission
Using the power triangle, calculate the MW component when the MVA and Mvar values are 10
and 6, respectively.
a) 2 MW
b) 8 MW
c) 16 MW
d) 136 MW
Consider a power triangle with 10 MVA and 6 MW. What is the power factor?
a) 16%
b) 40%
c) 60%
d) 140%
Consider a power triangle with 5 MVA and 3 Mvar. What is the power factor?
a) 8%
b) 15%
c) 80%
d) 108%
Generators, motors (read turbines)
Field current in a generator flows through which of the following?
a) The rotor
b) The magnetic coil
c) The battery
d) The turbine
Increasing the torque exerted on the rotor shaft ________ torque angle.
a) Decreases
b) Increases
c) Has no affect on
d) None of the above
Two generators in the same system have differing maximum output values. The East generator,
operating at 60.000 Hz is located 40 miles from the West generator, which is _________.
a) Operating at 60.040 Hz
b) Operating at 59.960 Hz
c) Operating at 60.000 Hz
d) None of the Above
© 2013 IncSys – Not Distributable Without Permission
Increasing mechanical input to a generator connected only to one load will cause which of the
following?
a) Decrease in frequency
b) Increase in frequency
c) No change in frequency
d) None of the above
Increasing load on the same generator as the in the previous question will cause which of the
following?
a) Decrease in frequency
b) Increase in frequency
c) No change in frequency
d) None of the above
When a generator’s power output cannot stay in line with its mechanical input, this is called
________.
a) Loss of synchronism
b) Loss of Field
c) Motoring
d) None of the above
Which of the following will increase when mechanical power is increased on a generator?
a) Torque Angle
b) Power Factor
c) Phase Angle
d) Both A and B
Power Transformers
What is the secondary current on an 800:5 CT with 400 amps flowing in?
a) 2 amps
b) 2.5 amp
c) 8.4 amps
d) 160 amps
e) 400 amps
What is the secondary current on a 400:5 CT with 120 amps flowing in?
a) 0.5 amp
b) 1.5 amps
c) 2.5 amps
d) 5 amps
A current transformer (CT) creates a ________ output is used for metering and relaying.
© 2013 IncSys – Not Distributable Without Permission
a)
b)
c)
d)
Low current
High current
Low voltage
None of the above
Why is it beneficial to step power up to higher voltages?
a) Current is lowered, meaning less power losses
b) Current is increased, meaning faster power delivery
c) Current is lowered, meaning faster power delivery
d) Current is increased, meaning less power losses
e) None of the above
In a three phase power transformer, the ______ connection has a common point for all
windings, while the ______ has all three windings connected in series
a) tertiary; secondary
b) primary; autotransformer
c) delta; wye
d) wye; delta
Losses in a transformer due to its excitation current is proportional to which formula?
a) PV=nRT
b) V = IR
c) I^2 * R
d) P = VI
Transmission Lines
In modern transmission lines, copper has been largely replaced by __________.
The advantage of using aluminum (over copper) in transmission line conductors is that
aluminum is ______.
a) More expensive
b) Cheaper
c) Lighter
d) Both B and C
© 2013 IncSys – Not Distributable Without Permission
Phases
The image above represents which of the following?
a) The natural capacitance of a transmission line
b) Phase to ground faults
c) Phase to phase faults
d) Both B and C
The image above represents which of the following?
a) The natural capacitance of a transmission line
b) Transmission line impedance model
c) Power-angle curve
d) Both A and B
© 2013 IncSys – Not Distributable Without Permission
Active, Reactive, and Complex Power
Which of the following describes reactive power flow?
I. It supports the magnetic and electrical fields necessary to operate power equipment
II.
It provides power to small resistive elements
III.
It is never consumed by the power system
IV. It is a continual exchange of power and energy
a) I and II
b) I and III
c) IV
d) Both B and C
A _________ Generator can produce active and reactive power simultaneously.
a) Automatic
b) Double
c) Synchronous
d) Retroactive
A(n) _________ is a reactive power source, which supplies VARS to the system.
a) Insulator
b) Voltmeter
c) Battery
d) Capacitor
True or false: Supplying vars to the system will generally cause voltage to increase.
a) True
b) False
How many MVARs does a 100 MVAR capacitor bank provide at 90% of nominal voltage?
a) 75
b) 81
c) 95
d) 100
System operators can use ____________ to regulate voltage.
a) Synchronous Var condensors
b) Reactors
c) Shunt Capacitors
d) All of the above
© 2013 IncSys – Not Distributable Without Permission
Phase Angle, Power Angle, and Torque Angle
The _______ angle at a point in a power system is the angular separation between the current
and the voltage waves.
a) Voltage
b) Phase
c) Power
d) Torque
The ________ angle is the voltage angle between two locations in the power system.
a) Voltage
b) Phase
c) Power
d) Torque
The ______ angle of a generator has a large impact on the MW delivered by the generator to
the system.
a) Voltage
b) Phase
c) Power
d) Torque
Within limits, the larger the ___________, the more MW the generator outputs.
a) Voltage
b) Phase
c) Power
d) Torque
The larger the ______ angle (up to 90 degrees), the larger active power flow between the two
points.
a) Voltage
b) Phase
c) Power
d) Torque
The ___________ of a generator has a large impact on the MW delivered by the generator to
the system.
a) Voltage
b) Phase
c) Power
d) Torque
© 2013 IncSys – Not Distributable Without Permission
2-2: Mathematics
Right triangles
Which of the following is true about a Right Triangle in mathematics?
a) There are more than 3 sides
b) One of its angles equals 90 degrees
c) The hypotenuse is always the longest side of the triangle
d) Both B and C
The sum of the angles in a triangle always equals ______ degrees.
a) 0
b) 90
c) 180
d) 360
(Not drawn to scale)
Use the above diagram to answer the next 5 questions:
What is Angle C?
a) 45 degrees
b) 90 degrees
c) 120 degrees
d) 180 degrees
If angle A = 35 degrees, what is angle B?
a) 15 degrees
b) 55 degrees
c) 85 degrees
d) 170 degrees
© 2013 IncSys – Not Distributable Without Permission
If angle B = 56 degrees, what is angle A?
a) 34 degrees
b) 44 degrees
c) 114 degrees
d) 184 degrees
If side b = 4 and side a = 3, what is the length of side c?
5
If side c = 10 and side b = 8, what is the length of side a?
6
Trigonometric Functions
One period of a sine function is equivalent to how many degrees?
a) 90
b) 180
c) 360
d) There is not enough information
The magnitude of a sine wave at 80 degrees will be equal to the magnitude at ______.
a) 440 degrees
b) 180 degrees
c) 350 degrees
d) -10 degrees
Use the following figure to answer the next 6 questions.
How do you calculate the sine of angle A?
Side a divided by the hypotenuse c.
How do you calculate the sine of angle B?
Side b divided by the hypotenuse c.
© 2013 IncSys – Not Distributable Without Permission
If a=3, b=4, and c=5, what is the sine of angle A?
3/5
If a=3, b=4, and c=5, what is the sine of angle B?
4/5
It is given that Side c=10 and Side a = 6. Find Side b, Angle A, and Angle B. (Hint: follow the
example on page 79 of the dynamics tutorial)
B=8; A = 53.1 degrees; B = 36.9 degrees
It is given that Side b = 12 and Side a = 5. Find Side c, Angle A, and Angle B.
C=13; A=67.4 degrees; B = 22.6 degrees
Use of Ratios
Which of the following is an example of a ratio?
a) A fraction
b) A percentage
c) An hypotenuse
d) Both (a) and (b)
Assume a given generator unit has a maximum output of 800MW.
What percentage of the unit’s capacity is occupied when it is producing 600MW?
a) 20%
b) 40%
c) 75%
d) 100%
Which of the following fractions corresponds to 80%?
a) 8/10
b) 8/100
c) 80/10
d) 800/10
© 2013 IncSys – Not Distributable Without Permission
Which of the following percentages corresponds to the fraction “2/5”?
a) 20%
b) 25%
c) 30%
d) 40%
From prior experience, you know that a loss of a 1500 MW generator unit in a given system
results in a 0.3 HZ dip in system frequency. What frequency dip would result from the loss of a
1000 MW unit?
a) 0.1 HZ
b) 0.2 HZ
c) 0.3 HZ
d) None of the above
It is known by experience that a loss of a 1200 MW unit in a given system results in a 0.1 HZ dip
in system frequency. Today, a fully loaded generator unit in your system tripped off, resulting
in a 0.08 HZ dip in system frequency. What is the maximum MW output of this generator?
a) 800
b) 920
c) 960
d) 1000
Per-Unit values
Suppose the voltage at a 345 kV bus is measured as 355 kV. Which of the following is closest to
the per-unit voltage?
a) 0.85
b) 0.97
c) 1.03
d) 1.15
Suppose the per-unit voltage at a 115 kV bus is measured as 0.92. Which of the following is
closest to the actual voltage?
a) 92.9
b) 105.8
c) 115
d) 120.5
Suppose the voltage at a 12 kV bus is measured as 18 kV. What is the per-unit voltage?
a) 1.2
b) 1.4
c) 1.5
d) 1.6
© 2013 IncSys – Not Distributable Without Permission
Suppose the per-unit voltage at a 34.5 kV bus is measured as 1.24. Which of the following is
closest to the actual voltage?
a) 12.4
b) 27.8
c) 34.5
d) 42.8
For the following three questions, suppose a 138kV to 345kV transformer with a 105 MVA
Rating has a 7% impedance at a given moment.
6. What is the per-unit impedance? ______ p.u. 0.07
7. Calculate the base impedance for the high side (345kV) ________ Ohms 1133.6
8. Calculate the base impedance for the low side (138kV) ________ Ohms 181.4
9. Calculate the Actual Ohms on the high side base ________ Ohms 79.3
10. Calculate the Actual Ohms on the low side base _________ Ohms 12.7
2-3: DC electricity
Current
What is the unit of measurement of electric current?
a) Coulon
b) Hertz
c) Ampere
d) Volts
Current is measured as an amount of _________ passing through a cross section of a conductor
over time.
a) Charge
b) Voltage
c) Electrical Power
d) None of the above
True or false: electrons in a conductor require a force to cause a current flow to occur.
a) True
b) False
Choose the answer which completes the following sentence. Electrons are _______ charged.
a) Positively
b) Negatively
c) Neutrally
d) (None of the above)
© 2013 IncSys – Not Distributable Without Permission
Resistance
Resistance uses the same unit of measurement as which of the following?
a) Current
b) Voltage
c) Impedance
d) Reactance
Conductor A has twice the resistivity of conductor B. Which is the better conductor?
Conductor B
Which of the following factors affects the resistance for a given conductor?
a) Length of the conductor
b) Type of conductor material
c) The voltage drop across the conductor
d) Both A and B
Use the following image of Circuit segments A and B to answer the next 2 questions.
Assume that R1 = R2. Which circuit will allow more current flow from left to right? Parallel
Assume that R1 = R2. Which circuit has more total resistance? Series
The letter “I” in electrical formulas usually represents ______?
a) Inductance
b) Voltage
c) Current
d) Impedance
Voltage
True or false: electrons in a conductor require voltage to cause a current flow to occur.
a) True
b) False
© 2013 IncSys – Not Distributable Without Permission
Voltage is the ___________ that results in a potential for current flow.
a) Electromagnetic Pulse
b) Locomotive Force
c) Separation of charge
d) Distance between each electron
Which of the following is NOT an example of a voltage source?
a) Battery
b) Generator
c) Voltmeter
d) None of the above
Which of the following is NOT an example of where Measured Voltage can be taken?
a) Between two phases of a transmission line
b) From phase to ground
c) From ground to ground
d) None of the above
Which of the following is NOT true about voltage?
a) It is the distance between two separated charges
b) It is the electromotive force that causes current flow in a conductor
c) It is also known as potential difference.
d) Its unit of measurement is the volt
Which of the following devices maintains a voltage difference (EMF) between its terminals?
a) Circuit Breaker
b) Autotransformer
c) Voltage source
d) Voltmeter
Electrical Circuits
In which of the following types of circuits does voltage and current remain at a constant level?
a) Parallel Circuit
b) DC Circuit
c) AC Circuit
d) Series Circuit
Which of the following is an example of a voltage source for a direct current circuit?
a) Battery
b) Generator
c) Alternator
d) None of the above
© 2013 IncSys – Not Distributable Without Permission
Ohm’s Law
Which of the following is the Ohm’s Law?
a) V=IR
b) P=VI
c) E=MC
d) I=CE
If 6 amps flows through .6 Ohms of resistance, what is the voltage in volts?
3.6
If the current in a 8 volt circuit is 10 amps, what is the resistance in ohms?
0.8
In a simple electrical circuit with a 12 volt supply and a 24 ohm resistor, current is ____ amps
0.5
Kirchoff’s Laws
The total resistance of a series circuit containing three 5-ohm resistors is ______ ohms. 15
The total resistance of a parallel circuit containing two 10-ohm resistors is ______ ohms. 5
The total resistance of a series circuit containing four 25-ohm resistors is ______ ohms. 100
The total resistance of a parallel circuit containing six 4.5-ohm resistors is ______ ohms. 0.75
© 2013 IncSys – Not Distributable Without Permission
Use the above image to answer the following 6 questions:
True or false: R1 and R2 are in parallel. False
What is the source voltage (in volts)? 12
What is the source current (in amps)? 4
What is the total resistance (in ohms)? 3
What is the voltage drop across R1 (in volts)? 4
What is the voltage drop across R2 (in volts)? 8
Power and Energy
Which of the following is the DC Power equation?
a) V=IR
b) P=VI
c) E=MC
d) I=CE
© 2013 IncSys – Not Distributable Without Permission
Which of the following is NOT a correct way to rearrange the DC Power equation?
a) P=VI
b) V=P/I
c) I=P/V
d) I=V/P
Power in a simple 12 volt, 4 amp DC series circuit is _____.
a) 8 W
b) 3 W
c) 16 W
d) 48 W
Power in a simple 15 volt, 3 amp DC series circuit is _____.
a) 12 W
b) 18 W
c) 45 W
d) None of the above
Current in a simple 12 volt, 60W series circuit is_______.
a) 5 amp
b) 6 amp
c) 10 amp
d) 12 amp
2-4: AC Electricity
Alternating Current Systems
Each phase in a 3-phase AC system is _____________ degrees out of phase with the other two
phases.
a) 0
b) 30
c) 90
d) 120
© 2013 IncSys – Not Distributable Without Permission
What is the amplitude of the above sine wave? 2.5
If in the above image, x = 10 seconds, what is the period (in seconds) of this sine wave?
10
When the sine waves of both current and voltage peak at the same, this is known as ______.
a) Current is lagging voltage
b) Current is leading voltage
c) Current is in phase with voltage
d) None of the above
The magnitude of a sine function is maximized at __________?
a) 0 degrees
b) 45 degrees
c) 90 degrees
d) 180 degrees
The magnitude of a sine function is minimized at __________?
a) 0 degrees
b) 45 degrees
c) 90 degrees
d) 180 degrees
If current leads voltage then _________ reacts more quickly to changes than _________?
a) voltage; current
b) current; voltage
c) primary winding; secondary winding
d) generator; load
© 2013 IncSys – Not Distributable Without Permission
Magnetism and Magnetic Fields
Which of the following is the unit of measurement for inductance?
a) Ohm
b) Amp
c) Watt
d) Henry
Which of the following will increase the strength of the magnetic field in an electromagnet?
a) Increasing the distance between the poles
b) Increasing the turns of wire
c) Decreasing the turns of wire
d) Decreasing the number of magnetic poles
Magnetic flux lines go from the north pole to the south pole of the magnet.
a) True
b) False
A transformer turns ratio is ______ its current ratio.
a) Inversely related to
b) Not related to
c) Equal to
d) None of the Above
AC Power
Total opposition to current flow in an AC circuit with both resistance and reactance is called
_________.
a) Impedance
b) Inductance
c) Capacitance
d) MVA
Active power and reactive power are _______ degrees apart in phase
a) 0
b) 45
c) 90
d) 180
Using the power triangle, calculate the MVA when the MW and Mvar components are 3 and 4,
respectively.
a) 5 MVA
b) 7 MVA
c) 12 MVA
d) 25 MVA
© 2013 IncSys – Not Distributable Without Permission
Using the power triangle, calculate the MW component when the MVA and Mvar values are 10
and 6, respectively.
a) 2 MW
b) 8 MW
c) 16 MW
d) 136 MW
Consider a power triangle with 10 MVA and 6 MW. What is the power factor?
a) 16%
b) 40%
c) 60%
d) 140%
Consider a power triangle with 5 MVA and 3 Mvar. What is the power factor?
a) 8%
b) 15%
c) 80%
d) 108%
2-5: Protective Relaying
Read
2.6: Power System Equipment
Generators, motors (read turbines)
Field current in a generator flows through which of the following?
a) The rotor
b) The magnetic coil
c) The battery
d) The turbine
Increasing the torque exerted on the rotor shaft ________ torque angle.
a) Decreases
b) Increases
c) Has no affect on
d) None of the above
Two generators in the same system have differing maximum output values. The East generator,
operating at 60.000 Hz is located 40 miles from the West generator, which is _________.
a) Operating at 60.040 Hz
b) Operating at 59.960 Hz
c) Operating at 60.000 Hz
d) None of the Above
© 2013 IncSys – Not Distributable Without Permission
Increasing mechanical input to a generator connected only to one load will cause which of the
following?
a) Decrease in frequency
b) Increase in frequency
c) No change in frequency
d) None of the above
Increasing load on the same generator as the in the previous question will cause which of the
following?
a) Decrease in frequency
b) Increase in frequency
c) No change in frequency
d) None of the above
When a generator’s power output cannot stay in line with its mechanical input, this is called
________.
a) Loss of synchronism
b) Loss of Field
c) Motoring
d) None of the above
Which of the following will increase when mechanical power is increased on a generator?
a) Torque Angle
b) Power Factor
c) Phase Angle
d) Both A and B
Power Transformers
What is the secondary current on an 800:5 CT with 400 amps flowing in?
a) 2 amps
b) 2.5 amp
c) 8.4 amps
d) 160 amps
e) 400 amps
What is the secondary current on a 400:5 CT with 120 amps flowing in?
a) 0.5 amp
b) 1.5 amps
c) 2.5 amps
d) 5 amps
© 2013 IncSys – Not Distributable Without Permission
A current transformer (CT) creates a ________ output is used for metering and relaying.
a) Low current
b) High current
c) Low voltage
d) None of the above
Why is it beneficial to step power up to higher voltages?
a) Current is lowered, meaning less power losses
b) Current is increased, meaning faster power delivery
c) Current is lowered, meaning faster power delivery
d) Current is increased, meaning less power losses
e) None of the above
In a three phase power transformer, the ______ connection has a common point for all
windings, while the ______ has all three windings connected in series
a) tertiary; secondary
b) primary; autotransformer
c) delta; wye
d) wye; delta
Losses in a transformer due to its excitation current is proportional to which formula?
a) PV=nRT
b) V = IR
c) I^2 * R
d) P = VI
Transmission Lines
In modern transmission lines, copper has been largely replaced by __________.
Aluminum
The advantage of using aluminum (over copper) in transmission line conductors is that
aluminum is ______.
a) More expensive
b) Cheaper
c) Lighter
d) Both B and C
© 2013 IncSys – Not Distributable Without Permission
Phases
The image above represents which of the following?
a) The natural capacitance of a transmission line
b) Phase to ground faults
c) Phase to phase faults
d) Both B and C
The image above represents which of the following?
a) The natural capacitance of a transmission line
b) Transmission line impedance model
c) Power-angle curve
d) Both A and B
© 2013 IncSys – Not Distributable Without Permission
3.1-3.2: Active and Reactive Power
Active, Reactive, and Complex Power
Which of the following describes reactive power flow?
I.
It supports the magnetic and electrical fields necessary to operate power equipment
II.
It provides power to small resistive elements
III.
It is never consumed by the power system
IV.
It is a continual exchange of power and energy
a) I and II
b) I and III
c) IV
d) Both B and C
A _________ Generator can produce active and reactive power simultaneously.
a) Automatic
b) Double
c) Synchronous
d) Retroactive
A (n) _________ is a reactive power source, which supplies VARS to the system.
a) Insulator
b) Voltmeter
c) Battery
d) Capacitor
True or false: Supplying vars to the system will generally cause voltage to increase.
c) True
d) False
How many MVARs does a 100 MVAR capacitor bank provide at 90% of nominal voltage?
a) 75
b) 81
c) 95
d) 100
System operators can use ____________ to regulate voltage.
a) Synchronous Var condensors
b) Reactors
c) Shunt Capacitors
d) All of the above
© 2013 IncSys – Not Distributable Without Permission
Phase Angle, Power Angle, and Torque Angle
The _______ angle at a point in a power system is the angular separation between the current
and the voltage waves.
a) Voltage
b) Phase
c) Power
d) Torque
The ________ angle is the voltage angle between two locations in the power system.
a) Voltage
b) Phase
c) Power
d) Torque
The ______ angle of a generator has a large impact on the MW delivered by the generator to
the system.
a) Voltage
b) Phase
c) Power
d) Torque
Within limits, the larger the ___________, the more MW the generator outputs.
a) Voltage
b) Phase
c) Power
d) Torque
The larger the ______ angle (up to 90 degrees), the larger active power flow between the two
points.
a) Voltage
b) Phase
c) Power
d) Torque
The ___________ of a generator has a large impact on the MW delivered by the generator to
the system.
a) Voltage
b) Phase
c) Power
d) Torque
© 2013 IncSys – Not Distributable Without Permission