EGSA Paralleling and Switchgear Controls 4

Question 1

What is the purpose of reactive droop compensation in an automatic voltage regulator (AVR) when generators are paralleled?

Accepted Answer

To provide a drooping VAR-vs-voltage characteristic that promotes stable reactive load sharing

Answer

Reactive droop (cross-current compensation) intentionally reduces AVR output as reactive output increases, creating a drooping characteristic that stabilizes reactive load division between paralleled machines.

Question 2

A transfer scheme described as 'open transition' with 'in-phase monitoring' will:

Accepted Answer

Open the normal source before closing the alternate source, but only when both sources are in phase

Answer

In-phase open transition waits for the natural voltage crossover point where both sources are momentarily in phase, then opens the normal source and immediately closes the alternate source, minimizing transfer transients.

Question 3

What condition is indicated when the frequency difference between paralleled generators results in a 'beat' frequency on the bus voltage waveform?

Accepted Answer

The generators have a slip frequency and are not yet fully synchronized

Answer

A beat frequency (amplitude modulation of the bus voltage) indicates a frequency difference (slip) between two generators that are running at slightly different speeds.

Question 4

In switchgear applications, what is the significance of an 'electrically operated' vs. a 'manually operated' circuit breaker?

Accepted Answer

Electrically operated breakers can be controlled remotely via SCADA or relay outputs without physical operator presence

Answer

Electrically operated breakers have motor-charged spring mechanisms and solenoid trip/close coils, enabling remote control, automatic relay tripping, and SCADA integration without a local operator.

Question 5

Which device function would be used to detect a generator operating as a motor (prime mover failure) in a paralleled system?

Accepted Answer

ANSI 32 – Directional power (reverse power) relay

Answer

The ANSI 32 reverse power relay detects when real power flow reverses (generator motoring) due to prime mover failure, and trips the generator breaker to protect the prime mover.

(EGSA) Electrical Generating Systems Association Certified Practice Test

(EGSA) Electrical Generating Systems Association Certified Practice Test

EGSA Paralleling and Switchgear Controls 4