NETA - InterNational Electrical Testing Association Certified Technicians Circuit Breaker Maintenance Questions and Answers

Question 1

A technician performs a contact resistance test on a 3-phase, low-voltage power circuit breaker.
The readings are: Phase A = 25 µΩ, Phase B = 30 µΩ, Phase C = 45 µΩ.
According to NETA MTS standards, what is the proper evaluation of these results?

Accepted Answer

Phase C is unacceptable as it deviates by more than 50% from the lowest reading.

Answer

The deviation between phases is acceptable.

Answer

All phases are unacceptable because the readings exceed 30 µΩ.

Answer

The test is invalid and must be repeated with a higher test current.

Question 2

During a visual and mechanical inspection of a molded-case circuit breaker (MCCB), which of the following findings would be the MOST critical concern requiring immediate investigation?

Accepted Answer

Discoloration and signs of overheating around the terminal connections.

Answer

Minor dust accumulation on the exterior casing.

Answer

The absence of a manufacturer's lubrication schedule.

Answer

Slight difficulty in operating the handle mechanism.

Question 3

A client has requested a full NETA-compliant maintenance procedure on a medium-voltage vacuum circuit breaker. Which of the following electrical tests is specifically required for vacuum breakers to verify the integrity of the interrupting medium?

Accepted Answer

Dielectric withstand voltage (hi-pot) test across the open contacts.

Answer

Contact timing test.

Answer

Insulation resistance test.

Answer

Contact resistance test.

Question 4

A NETA technician is performing an insulation resistance test on a 600V class air circuit breaker. The test is conducted for one minute, phase-to-ground with the breaker closed. According to NETA standards, what is the procedure if manufacturer's data is unavailable?

Accepted Answer

Apply 1000V DC and refer to NETA Table 100.1 for the minimum acceptable resistance.

Answer

Apply 500V DC and the minimum acceptable resistance is 1 megohm.

Answer

Apply 2500V DC and the reading should be trended against previous tests.

Answer

The test is optional and can be skipped if no data is available.

Question 5

A technician is evaluating the results of a circuit breaker timing test. The primary purpose of this test is to determine:

Accepted Answer

The speed at which the circuit breaker's contacts open and close.

Answer

The current-carrying capacity of the main contacts.

Answer

The integrity of the breaker's insulation system.

Answer

The condition of the arc chutes and interrupters.

Question 6

During the maintenance of a low-voltage power circuit breaker with an electronic trip unit, a technician performs a primary current injection test. What is the main advantage of this test over a secondary current injection test?

Accepted Answer

It verifies the entire current path, including current sensors and the tripping mechanism.

Answer

It requires less setup time and is easier to perform.

Answer

It uses a lower, safer current to verify trip unit settings.

Answer

It is the only method to test thermal-magnetic breakers.

A technician performs a contact resistance test on a 3-phase, low-voltage power circuit breaker.The readings are: Phase A = 25 µΩ, Phase B = 30 µΩ, Phase C = 45 µΩ.According to NETA MTS standards, what is the proper evaluation of these results?

A technician performs a contact resistance test on a 3-phase, low-voltage power circuit breaker.
The readings are: Phase A = 25 µΩ, Phase B = 30 µΩ, Phase C = 45 µΩ.
According to NETA MTS standards, what is the proper evaluation of these results?