NETA Cable Testing and Diagnostics 5

Question 1

During a cable dielectric absorption (DA) test, a DA ratio less than 1.0 most likely indicates:

Accepted Answer

Insulation that is wet, contaminated, or severely degraded

Answer

A dielectric absorption ratio below 1.0 means current increased over time rather than decreased, strongly indicating wet, conductive, or severely degraded insulation.

Question 2

Which cable diagnostic test method uses a sinusoidal voltage at 0.1 Hz and simultaneously measures the tan delta to assess insulation condition?

Accepted Answer

VLF withstand test with tan delta monitoring

Answer

VLF tan delta testing applies 0.1 Hz sinusoidal voltage while continuously measuring the dissipation factor to detect insulation aging and water treeing.

Question 3

When a cable section has been flooded with water, how does this primarily affect megohmmeter insulation resistance readings?

Accepted Answer

IR decreases dramatically, often below 1 MΩ

Answer

Water creates conductive paths through or along insulation, drastically lowering insulation resistance and often producing readings well below 1 MΩ.

Question 4

According to NETA MTS, the temperature correction factor for insulation resistance tests is applied to normalize readings to which reference temperature?

Accepted Answer

20°C

Answer

NETA MTS specifies correcting insulation resistance measurements to a reference temperature of 20°C to allow valid comparisons between tests taken at different ambient conditions.

Question 5

What is the significance of a 'kink' or sudden step in the TDR trace at a location other than the far end of the cable?

Accepted Answer

A fault, splice, or impedance discontinuity at that distance

Answer

A step or kink in the TDR waveform at a mid-cable location indicates a fault, splice, connector, or impedance change at the corresponding distance from the test point.

(NETA) InterNational Electrical Testing Association Certified Technicians Practice Test

(NETA) InterNational Electrical Testing Association Certified Technicians Practice Test

NETA Cable Testing and Diagnostics 5