NETA Power Cable Test Methods 2

Question 1

When performing a DC high-potential test on a shielded cable, where should the voltage be applied?

Accepted Answer

Between conductor and shield/ground

Answer

DC hi-pot voltage is applied between the conductor and the grounded shield to stress the insulation as it would be in service.

Question 2

Which test method is best suited for locating the position of a fault in an underground cable?

Accepted Answer

Time Domain Reflectometry (TDR)

Answer

TDR sends a pulse along the cable and measures the reflected signal travel time to pinpoint fault location.

Question 3

A cable's insulation resistance reading drops significantly when corrected to 20°C compared to the reading taken at 40°C. What does this indicate?

Accepted Answer

The insulation may be deteriorating since temperature correction should increase the reading

Answer

Insulation resistance decreases with temperature, so a corrected (lower-temperature) value that is still low suggests genuine insulation degradation.

Question 4

What is the primary purpose of a guard terminal on a megohmmeter when testing cables?

Accepted Answer

To eliminate surface leakage current from the measurement

Answer

The guard terminal diverts surface leakage and connector contamination currents away from the measurement circuit so only bulk insulation current is read.

Question 5

During a VLF (Very Low Frequency) hipot test, what typical frequency is used?

Accepted Answer

0.1 Hz

Answer

VLF testing uses 0.1 Hz to reduce reactive current demand on the test set compared to 60 Hz testing.

(NETA) InterNational Electrical Testing Association Certified Technicians Practice Test

(NETA) InterNational Electrical Testing Association Certified Technicians Practice Test

NETA Power Cable Test Methods 2