Search

What Is a Good Ground Resistance Value?

Home / Technical Articles / Electrical Lectures / What Is a Good Ground Resistance Value?

Zero Ohms… Not Really!

The goal in ground resistance is to achieve the lowest ground resistance value possible, that makes sense economically and physically, when contacting the earth, also known as the soil/ground rod interface.

What Is a Good Ground Resistance Value?
What Is a Good Ground Resistance Value?

Ideally, a ground should be zero ohms of resistance, but…

Unfortunately, there is not one standard ground resistance threshold recognized by all certifying agencies.

The NFPA and IEEE recommend a ground resistance value of 5 ohms or less while the NEC has stated to “Make sure that system impedance to ground is less than 5 ohms specified in NEC 50.56. In facilities with sensitive equipment it should be 5ohms or less.

Copper Earth Rod thermoweld connection at a 33kV Substation in Nakheel, UAE
Copper Earth Rod thermoweld connection at a 33kV Substation in Nakheel, UAE (photo by Muhammad Adnan; Substation Designer via Flickr)

The telecommunications industry has often used 5 ohms or less as their value for grounding and bonding while electric utilities construct their ground systems so that the resistance at a large station will be no more than a few tenths of one ohm.

In general, the lower the ground resistance, the safer the system is considered to be.

Reference: Fluke Earth Ground Testing Fact – Distributor Training Program

SEARCH: Articles, software & guides

Premium Membership

Premium membership gives you an access to specialized technical articles and extra premium content (electrical guides and software).
Get Premium Now ⚡

About Author

author-pic

Edvard Csanyi

Edvard - Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV/MV switchgears and LV high power busbar trunking (<6300A) in power substations, commercial buildings and industry fascilities. Professional in AutoCAD programming. Present on