EGSA Paralleling and Switchgear Controls Questions and Answers

Question 1

In generator paralleling switchgear, which ANSI standard device number corresponds to the synchronism-check relay, whose primary function is to prevent the paralleling breaker from closing until voltage, frequency, and phase angle are within acceptable limits?

Accepted Answer

25

Answer

51

Answer

27

Answer

81

Question 2

A technician is attempting to parallel a generator to a live bus. The synchroscope is rotating slowly in the 'fast' direction, and voltages are matched. What is the MOST likely adjustment required to achieve synchronization?

Accepted Answer

Decrease the incoming generator's speed slightly.

Answer

Increase the incoming generator's voltage.

Answer

Decrease the incoming generator's voltage.

Answer

Increase the incoming generator's speed further.

Question 3

Which of the following best describes the primary purpose of the 'soft loading' or 'ramping' feature in an automatic paralleling control system?

Accepted Answer

To gradually transfer the real power (kW) load to or from the generator to prevent system disturbances.

Answer

To verify the paralleling breaker's mechanical operation under no-load conditions.

Answer

To allow the generator to build up full excitation before connecting to the bus.

Answer

To prevent a sudden voltage sag on the bus when the generator is connected.

Question 4

What hazardous condition is a reverse power relay (ANSI Device 32) designed to protect a generator against in a paralleling application?

Accepted Answer

The generator absorbing real power from the bus, causing it to be motored.

Answer

The generator drawing reactive power from the bus due to underexcitation.

Answer

The generator supplying excessive current into a short-circuit fault.

Answer

The bus frequency exceeding the generator's maximum operating limits.

Question 5

A facility with a multi-generator paralleling system experiences a complete power outage. Which control logic feature is essential for ensuring that the first generator to reach rated speed and voltage can close its breaker to the de-energized bus to begin restoration?

Accepted Answer

Dead bus closing logic

Answer

Load demand sequencing

Answer

Isochronous load sharing

Answer

Sync-check override

Question 6

When commissioning a new paralleling system, which of the following is NOT an absolute electrical requirement for safely synchronizing two AC generators?

Accepted Answer

Identical prime mover horsepower ratings.

Answer

Equal terminal voltages.

Answer

Same phase sequence.

Answer

Matching frequencies and phase angles.