EGSA Paralleling and Switchgear Controls 3

Question 1

What parameter does a voltage matching relay check before permitting synchronization in an automatic paralleling system?

Accepted Answer

Difference in RMS voltage magnitude between the incoming generator and the bus

Answer

The voltage matching relay ensures the incoming generator's terminal voltage is within a preset window (typically ±5%) of the bus voltage before enabling a close signal.

Question 2

A generator paralleling panel uses a 'check synchronizer' (25) relay. What does this device do?

Accepted Answer

It supervises the automatic synchronizer and blocks closing if synchronizing conditions are not met

Answer

The ANSI 25 check synchronizer relay monitors voltage magnitude, frequency, and phase angle differences and blocks the breaker close coil unless all synchronizing windows are satisfied.

Question 3

In droop speed governing, increasing the droop percentage on a generator while paralleled will generally result in:

Accepted Answer

The generator taking a smaller share of load for the same frequency deviation

Answer

Higher droop means a steeper speed-vs-load characteristic, so the governor reduces fuel/speed less aggressively per unit of load increase, resulting in that generator picking up proportionally less load.

Question 4

What is the function of a bus tie breaker in a switchgear lineup with two main bus sections?

Accepted Answer

It connects the two bus sections to allow power flow between them or to isolate a faulted section

Answer

A bus tie breaker interconnects two bus sections, enabling power transfer from one section to the other or allowing isolation of a faulted section to maintain continuity on the healthy section.

Question 5

Which ANSI device number is assigned to an instantaneous overcurrent relay?

Accepted Answer

50

Answer

ANSI device 50 is the instantaneous overcurrent relay, which operates without intentional time delay when current exceeds its pickup threshold.

(EGSA) Electrical Generating Systems Association Certified Practice Test

(EGSA) Electrical Generating Systems Association Certified Practice Test

EGSA Paralleling and Switchgear Controls 3