AEP Power Generation & Transmission 2 — Questions and Answers
Question 1: What is the primary purpose of a step-up transformer at a power plant substation?
- Reduce voltage for local distribution
- Increase voltage to minimize transmission losses (Correct answer)
- Convert AC to DC for long-distance lines
- Regulate frequency of the output power
Correct answer: Increase voltage to minimize transmission losses
Step-up transformers increase voltage (and reduce current) so that resistive losses (I²R) are minimized over long transmission distances.
Question 2: Which fuel source accounts for the largest share of AEP's electricity generation capacity?
- Nuclear
- Natural gas
- Coal (Correct answer)
- Wind
Correct answer: Coal
Historically, coal has accounted for the largest share of AEP's generation capacity, though the company is actively transitioning toward natural gas and renewables.
Question 3: What does 'baseload generation' mean in the context of power plant operations?
- Plants that run only during peak demand hours
- Plants that provide minimum constant output to meet steady demand (Correct answer)
- Plants kept on standby for grid emergencies
- Plants that generate power exclusively from renewable sources
Correct answer: Plants that provide minimum constant output to meet steady demand
Baseload plants operate at a continuous, steady output level to meet the minimum (base) level of electricity demand that exists around the clock.
Question 4: In an AC transmission system, what is the standard frequency used in the United States?
- 50 Hz
- 60 Hz (Correct answer)
- 25 Hz
- 400 Hz
Correct answer: 60 Hz
The U.S. grid operates at 60 Hz, meaning the alternating current completes 60 cycles per second.
Question 5: What is 'reactive power' (VAR) and why is it important for transmission grids?
- Power lost as heat in transmission lines
- Power that performs real work in loads
- Power that supports voltage levels but does no real work (Correct answer)
- Power generated exclusively by capacitor banks
Correct answer: Power that supports voltage levels but does no real work
Reactive power (measured in VARs) is necessary to maintain voltage levels across the grid, even though it does not perform useful work in loads.
Question 6: Which switching device is used to isolate a section of transmission line for maintenance without de-energizing the entire system?
- Circuit breaker
- Disconnect switch (Correct answer)
- Load tap changer
- Surge arrester
Correct answer: Disconnect switch
Disconnect switches (also called isolators) physically separate a line segment from the energized grid, allowing safe maintenance after a circuit breaker has interrupted load current.
Question 7: What does 'transmission congestion' refer to in electric power systems?
- Too many electrons flowing through a single wire
- A condition where transmission lines cannot carry all desired power flows (Correct answer)
- Overloading of transformer windings
- Interference from neighboring utilities on shared frequencies
Correct answer: A condition where transmission lines cannot carry all desired power flows
Transmission congestion occurs when the physical limits of transmission lines prevent all desired electricity trades from flowing, often raising locational prices.
AEP Power Generation & Transmission 2
What is the primary purpose of a step-up transformer at a power plant substation?