EPRI Power System Dynamics Review – Qs & As
If a generator is producing 500 MW and 200 Mvar, is the generator?
-Leading
-Lagging
-Underexcited
-Dropping ✔️Ans --Lagging
What is the IEEE device number for a differential relay?
-87
-86
-67
-50 ✔️Ans --87
Can a synchronous machine have a negative torque angle? What does this
mean?
-Yes / the machine is absorbing reactive power
-No / the machine is absorbing active power
-No / the machine is absorbing reactive power
-Yes / the machine is absorbing active power ✔️Ans --Yes / the
machine is absorbing active power
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?
-Double the losses
-Halves the losses
-Increases the losses by a factor of four
-Decreases the losses by a factor of four ✔️Ans --Decreases the
losses by a factor of four
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?
,-50 amps / 5000 watts
-40 amps / 80 watts
-50 amps / 100 watts
-40 amps / 3200 watts ✔️Ans --50 amps / 5000 watts
The actual voltage is 362 kV on a 345 kV bus. What is the p.u. voltage?
- 1.0
- 1.05
- 1.5
- .95 ✔️Ans -- 1.05
A load has a power factor of 0.9 lagging. If the load draws 100 MVA, what is
the MW draw?
- 100
- 90
- 111
- 44 ✔️Ans -- 90
Which of the following is NOT a synchronizing variable?
- Phase angle
- Frequency difference
- Voltage magnitude difference
- MW flow differential ✔️Ans -- MW flow differential
In a typical multi-stage steam turbine, the governor control valves control the
steam entry to the:
- high pressure turbine
- intermediate pressure turbine
- low pressure turbine
- crossover ✔️Ans -- high pressure turbine
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?
, - 199 kV
- 230 kV
- 345 kV
- 500 kV ✔️Ans -- 345 kV
Thermal limits are the direct result of?
- High torque and power angles
- The thermal capability of system equipment
- A reactive power deficiency
- All of the above ✔️Ans -- The thermal capability of system
equipment
True or False: Reactive power flow is influenced more by system power and
torque angles than reactive power. ✔️Ans -False
At what line power angle does the MW transfer across a transmission path
equal ½ of the path's PMAX?
- 15 degrees
- 20 degrees
- 30 degrees
- 45 degrees ✔️Ans -- 30 degrees
A transmission line is rated at 1000 MVA. The power flow is currently 0 MW
and 1001 Mvar. Is the transmission line overloaded?
- Yes
- No
- Impossible to determine
- The line has no load ✔️Ans -- Yes
The TTC limit has been determine to be 1000 MW from east to west for a
particular transmission path. The transmission path operator sells 500 MW of
this TTC. What is the path's ATC?
- 1000 MW
- 1500 MW
If a generator is producing 500 MW and 200 Mvar, is the generator?
-Leading
-Lagging
-Underexcited
-Dropping ✔️Ans --Lagging
What is the IEEE device number for a differential relay?
-87
-86
-67
-50 ✔️Ans --87
Can a synchronous machine have a negative torque angle? What does this
mean?
-Yes / the machine is absorbing reactive power
-No / the machine is absorbing active power
-No / the machine is absorbing reactive power
-Yes / the machine is absorbing active power ✔️Ans --Yes / the
machine is absorbing active power
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?
-Double the losses
-Halves the losses
-Increases the losses by a factor of four
-Decreases the losses by a factor of four ✔️Ans --Decreases the
losses by a factor of four
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?
,-50 amps / 5000 watts
-40 amps / 80 watts
-50 amps / 100 watts
-40 amps / 3200 watts ✔️Ans --50 amps / 5000 watts
The actual voltage is 362 kV on a 345 kV bus. What is the p.u. voltage?
- 1.0
- 1.05
- 1.5
- .95 ✔️Ans -- 1.05
A load has a power factor of 0.9 lagging. If the load draws 100 MVA, what is
the MW draw?
- 100
- 90
- 111
- 44 ✔️Ans -- 90
Which of the following is NOT a synchronizing variable?
- Phase angle
- Frequency difference
- Voltage magnitude difference
- MW flow differential ✔️Ans -- MW flow differential
In a typical multi-stage steam turbine, the governor control valves control the
steam entry to the:
- high pressure turbine
- intermediate pressure turbine
- low pressure turbine
- crossover ✔️Ans -- high pressure turbine
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?
, - 199 kV
- 230 kV
- 345 kV
- 500 kV ✔️Ans -- 345 kV
Thermal limits are the direct result of?
- High torque and power angles
- The thermal capability of system equipment
- A reactive power deficiency
- All of the above ✔️Ans -- The thermal capability of system
equipment
True or False: Reactive power flow is influenced more by system power and
torque angles than reactive power. ✔️Ans -False
At what line power angle does the MW transfer across a transmission path
equal ½ of the path's PMAX?
- 15 degrees
- 20 degrees
- 30 degrees
- 45 degrees ✔️Ans -- 30 degrees
A transmission line is rated at 1000 MVA. The power flow is currently 0 MW
and 1001 Mvar. Is the transmission line overloaded?
- Yes
- No
- Impossible to determine
- The line has no load ✔️Ans -- Yes
The TTC limit has been determine to be 1000 MW from east to west for a
particular transmission path. The transmission path operator sells 500 MW of
this TTC. What is the path's ATC?
- 1000 MW
- 1500 MW
