Power System Flashcards

What is the purpose of a surge arrester in a power system?

Answer: To protect equipment from transient overvoltages

Surge arresters clamp transient overvoltages caused by lightning or switching surges, protecting insulation of connected equipment.

Which fault type is the most common in overhead transmission lines?

Answer: Single line-to-ground fault

Single line-to-ground faults account for approximately 70–80% of all faults on overhead transmission lines due to insulator flashovers or conductor contact with ground.

What does the term 'infinite bus' represent in power system analysis?

Answer: A bus with constant voltage and frequency regardless of load

An infinite bus is an idealized source with constant voltage magnitude and frequency, used as a reference in stability studies.

The Ferranti effect in a transmission line occurs when:

Answer: The line is lightly loaded or open-circuited at the receiving end

Under light or no-load conditions, the charging current of the line causes the receiving-end voltage to exceed the sending-end voltage.

In a power system, the term 'spinning reserve' refers to:

Answer: Generating capacity online and synchronized but not fully loaded

Spinning reserve is online generating capacity that can immediately respond to sudden load increases or generation loss.

What is the skin effect in transmission line conductors?

Answer: Increase in conductor resistance at high frequencies due to current crowding near the surface

At higher frequencies, eddy currents push current toward the conductor surface, effectively reducing the cross-sectional area and increasing resistance.

The base impedance in a per-unit system is defined as:

Answer: Base voltage squared divided by base MVA

Base impedance equals (base kV)² / base MVA, derived from Ohm's law applied to the chosen base voltage and power.