NETA Ground Resistance Testing Methods

Question 1

The fall-of-potential method for measuring ground electrode resistance uses a minimum of:

Accepted Answer

Two auxiliary electrodes (current and potential) and a ground resistance meter

Answer

One auxiliary electrode and two meters

Answer

Three auxiliary electrodes to triangulate the measurement

Answer

No auxiliary electrodes — it measures from the electrode to a reference point

Question 2

For the fall-of-potential test to provide accurate results, the current and potential electrodes should be placed at minimum distances because:

Accepted Answer

The resistance spheres of influence of the electrodes must not overlap

Answer

Short distances increase the test current, improving accuracy

Answer

Shorter distances reduce the effect of soil resistivity variations

Answer

Short distances are required by NETA testing standards only

Question 3

The Wenner 4-pin method is used to measure:

Accepted Answer

Soil resistivity, which is used to design grounding systems

Answer

Ground electrode resistance of a specific electrode

Answer

Contact resistance of buried ground conductors

Answer

Ground fault current in the grounding system

Question 4

A ground resistance test shows a reading of 50 ohms for an industrial substation grounding system. This value is:

Accepted Answer

Potentially too high — IEEE 80 and NETA recommend less than 1 ohm for substation grounding systems

Answer

Acceptable per NETA standards for all industrial installations

Answer

Excellent for a ground rod in high-resistivity soil

Answer

Normal for a grounding system in sandy soil

Question 5

The clamp-on ground resistance test method is advantageous because it:

Accepted Answer

Requires no auxiliary test electrodes and can test electrodes without disconnection from the grounding system

Answer

Provides more accurate results than the fall-of-potential method

Answer

Can be used to measure soil resistivity simultaneously

Answer

Tests the ground electrode at full fault current levels

Question 6

Touch potential and step potential are safety concerns during ground fault conditions because:

Accepted Answer

They describe the voltage a person could experience, which may cause ventricular fibrillation

Answer

They are measures of the ground electrode's ability to dissipate fault current

Answer

They determine the maximum fault current the grounding system can handle

Answer

They describe the mechanical forces on grounding conductors during faults