NETA Power Systems Analysis & Troubleshooting 4

Question 1

A voltage unbalance exceeding NEMA's recommended 1% limit on a three-phase induction motor will result in:

Accepted Answer

Increased motor heating and reduced lifespan

Answer

Voltage unbalance causes negative-sequence currents that significantly increase motor heating, reducing insulation life and efficiency.

Question 2

When performing a ground grid resistance test using the fall-of-potential method, the remote current electrode should be placed at a minimum distance of:

Accepted Answer

At least 5 times the maximum grid dimension

Answer

IEEE 81 recommends the remote current electrode be at least 5 to 10 times the maximum grid dimension to ensure accurate fall-of-potential measurements.

Question 3

In a distance relay (ANSI 21), the reach setting defines the:

Accepted Answer

Impedance boundary up to which the relay will trip

Answer

The reach of a distance relay is the impedance (and thus the distance along the line) up to which the relay will issue a trip command.

Question 4

The purpose of the NETA Acceptance Testing Specification (ATS) is to:

Accepted Answer

Establish performance criteria for newly installed electrical equipment

Answer

NETA ATS defines acceptance testing procedures and performance criteria to verify that newly installed electrical equipment meets manufacturer and industry standards.

Question 5

A sudden pressure relay (ANSI 63) on a transformer trips when it detects:

Accepted Answer

A rapid rise in internal gas or oil pressure due to an internal fault

Answer

The sudden pressure relay responds to a rapid rate-of-rise in internal pressure caused by an arcing internal fault, providing fast transformer protection.

(NETA) InterNational Electrical Testing Association Certified Technicians Practice Test

(NETA) InterNational Electrical Testing Association Certified Technicians Practice Test

NETA Power Systems Analysis & Troubleshooting 4