AEP Power Generation & Transmission 3 — Questions and Answers
Question 1: What is the function of a lightning arrester (surge arrester) on a transmission line?
- Increase line voltage during storms
- Divert transient overvoltages safely to ground (Correct answer)
- Measure lightning strike frequency
- Disconnect the line automatically during thunderstorms
Correct answer: Divert transient overvoltages safely to ground
Surge arresters clamp transient overvoltages caused by lightning or switching and divert the surge current to ground, protecting equipment insulation.
Question 2: In a combined-cycle natural gas plant, what happens to the exhaust heat from the gas turbine?
- It is vented directly into the atmosphere
- It is used to produce steam that drives a steam turbine for additional power (Correct answer)
- It preheats the incoming fuel gas
- It is recycled back into the combustion chamber
Correct answer: It is used to produce steam that drives a steam turbine for additional power
Combined-cycle plants recover hot exhaust gas from the combustion turbine in a heat recovery steam generator (HRSG) to produce steam that drives a second turbine, boosting overall efficiency above 60%.
Question 3: What is the purpose of a static VAR compensator (SVC) on a transmission system?
- Measure real power flow on a line
- Provide dynamic reactive power support to regulate voltage (Correct answer)
- Convert high-voltage DC back to AC
- Monitor line temperature in real time
Correct answer: Provide dynamic reactive power support to regulate voltage
An SVC rapidly injects or absorbs reactive power to maintain stable voltage at key transmission buses during load changes or faults.
Question 4: Which AEP subsidiary operates the high-voltage transmission system across much of the central and eastern U.S.?
- AEP Energy
- AEP Transmission (Correct answer)
- Appalachian Power
- Indiana Michigan Power
Correct answer: AEP Transmission
AEP Transmission (through subsidiaries like AEP Transmission Holding Company) owns and operates one of the largest high-voltage transmission networks in the nation.
Question 5: What does 'capacity factor' measure for a power plant?
- The ratio of actual output to maximum possible output over a period (Correct answer)
- The efficiency of fuel conversion to electricity
- The percentage of fuel burned versus fuel wasted
- The rated megawatt output at peak demand
Correct answer: The ratio of actual output to maximum possible output over a period
Capacity factor is the ratio of actual energy produced over a time period to the energy that would have been produced if the plant ran at full rated capacity the entire time.
Question 6: What is 'islanding' in the context of power grid operations?
- Installing offshore wind turbines on man-made islands
- A grid segment that operates independently after being separated from the main grid (Correct answer)
- A technique to route power around congested lines
- A method to balance load between multiple generators
Correct answer: A grid segment that operates independently after being separated from the main grid
Islanding occurs when a portion of the network becomes electrically isolated from the main grid but continues to be energized by local generation, which can create safety and synchronization hazards.
Question 7: What is the main advantage of high-voltage direct current (HVDC) transmission over AC for very long distances?
- HVDC is cheaper to build in all scenarios
- HVDC has lower resistive losses and no reactive power charging current on long lines (Correct answer)
- HVDC automatically regulates frequency
- HVDC requires no converter stations at either end
Correct answer: HVDC has lower resistive losses and no reactive power charging current on long lines
HVDC avoids the capacitive charging current and skin effect losses of AC, making it more efficient for bulk power over distances typically exceeding 500–600 miles.
AEP Power Generation & Transmission 3
What is the function of a lightning arrester (surge arrester) on a transmission line?