Voltage Regulation Flashcards

A transmission line experiences a sudden load increase. What is the FIRST control action a system operator should take to restore voltage?

Answer: Dispatch reactive power from nearby generators or capacitor banks

Reactive power support from generators or switched capacitor banks is the primary and fastest method to restore depressed voltage from load increases.

What does a negative voltage regulation value indicate about a transmission line?

Answer: Receiving-end voltage is higher than sending-end voltage

Negative voltage regulation occurs on lightly loaded or capacitive lines where the Ferranti effect raises receiving-end voltage above the sending-end value.

Which reactive power device provides continuously variable voltage support without introducing harmonics?

Answer: Static VAR Compensator (SVC)

An SVC uses thyristor-controlled reactors and thyristor-switched capacitors to provide stepless, rapid reactive power control with minimal harmonic injection (filters included).

Under which condition is the Ferranti effect most pronounced on a high-voltage transmission line?

Answer: Light load or open-circuit at the receiving end

The Ferranti effect is caused by line charging capacitance; with little or no load, there is no inductive current to offset the capacitive charging, so receiving-end voltage rises above sending-end voltage.

A generator is operating at rated MW output. The operator increases excitation. What happens to the generator's reactive power output and terminal voltage?

Answer: Reactive power increases; terminal voltage tends to rise

Increasing field excitation raises internal EMF, which pushes more reactive power (MVAR) out of the generator and supports higher terminal voltage.

What is the purpose of a load tap changer (LTC) deadband setting on a transformer?

Answer: Avoids unnecessary tap operations for small voltage deviations within an acceptable range

The deadband prevents hunting (rapid repeated tap changes) by requiring voltage to deviate beyond a defined band before a tap operation is initiated.

During a regional voltage emergency, the system operator issues a Conservative Operations instruction. Which of the following actions is consistent with that instruction?

Answer: Arming additional reactive reserves and avoiding further reactive resource commitment

Conservative Operations calls for preserving reactive reserves and limiting conditions that could worsen voltage collapse risk, including holding reactive resources in reserve.