NETA Ground Resistance Testing Methods 4

Question 1

When performing a slope method ground resistance test, what does a flat slope in the resistance curve indicate?

Accepted Answer

The current and potential electrodes are properly placed in resistivity-free soil

Answer

A flat or plateau region in the slope method curve indicates the potential electrode is outside the mutual resistance zones of both the current and ground electrodes, confirming valid placement.

Question 2

Which NETA standard specifies the acceptance criteria for ground grid resistance at electrical substations?

Accepted Answer

NETA ATS Section 7.13

Answer

NETA ATS Section 7.13 addresses grounding systems and provides acceptance criteria and test procedures for ground resistance measurements.

Question 3

What effect does frozen ground have on earth resistance measurements using the fall-of-potential method?

Accepted Answer

Frozen ground increases soil resistivity, giving falsely high readings

Answer

Ice formation in frozen soil dramatically increases resistivity because water, the primary conductor in soil, becomes non-conductive ice.

Question 4

In a clamp-on ground resistance test, what is the primary limitation compared to the fall-of-potential method?

Accepted Answer

Clamp-on testers cannot isolate a single electrode; they measure the parallel combination of all grounding paths

Answer

Clamp-on testers inject current into the ground loop and measure the total impedance of all parallel grounding paths, making it impossible to isolate a single electrode's resistance.

Question 5

A technician measures ground resistance using the 62% rule. The current electrode (C2) is placed 100 feet from the ground electrode (C1). Where should the potential electrode (P2) be placed?

Accepted Answer

62 feet from C1

Answer

The 62% rule places the potential electrode at 62% of the distance between the ground electrode and the current electrode, which is 0.62 × 100 = 62 feet from C1.

(NETA) InterNational Electrical Testing Association Certified Technicians Practice Test

(NETA) InterNational Electrical Testing Association Certified Technicians Practice Test

NETA Ground Resistance Testing Methods 4