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Home / Technical Articles / 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

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Edvard Csanyi

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 facilities. Professional in AutoCAD programming.

80 Comments


  1. Tarek Aboukhadra
    Aug 14, 2021

    Dear
    You Mentioned In the article
    NEC 50.56 Actually It Shall Be NEC 250.56
    thanks


  2. Tilak
    Apr 19, 2021

    My question is that what should the value of earthing of residential boarding school hostels and a classroom for all commercial buildings. kindly give your valuable answer so that we can maintain our earthing pits as per given your suggestion.


  3. Alacross
    Apr 07, 2021

    I need to learn


  4. Ezekiel Adeniyi
    Jan 03, 2021

    What should be ground ohms for 10kva solar powered system?

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