NETA Power Systems Analysis & Troubleshooting 2

Question 1

When performing a power factor test on a transformer bushing, a low power factor reading typically indicates:

Accepted Answer

Moisture or contamination in the insulation

Answer

Low power factor on a bushing test indicates moisture ingress or contamination degrading the dielectric insulation.

Question 2

A cable insulation resistance test shows dramatically different readings between phases. The MOST likely cause is:

Accepted Answer

Localized insulation damage or moisture on one phase

Answer

Significantly different IR readings between phases point to localized insulation damage or moisture penetration on the affected phase.

Question 3

In a protective relay coordination study, the primary goal is to ensure that:

Accepted Answer

The relay closest to the fault operates first

Answer

Relay coordination ensures the device nearest the fault operates first, isolating only the faulted section while upstream devices serve as backup.

Question 4

What does a tan delta (dissipation factor) trending upward over successive test intervals on a cable system indicate?

Accepted Answer

Progressive insulation degradation requiring attention

Answer

An upward trend in tan delta values over time indicates progressive deterioration of the cable insulation system.

Question 5

The ANSI device number for an overcurrent relay is:

Accepted Answer

50/51

Answer

ANSI device number 50 designates an instantaneous overcurrent relay and 51 designates a time-overcurrent relay.

(NETA) InterNational Electrical Testing Association Certified Technicians Practice Test