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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.

81 Comments


  1. reza
    Aug 21, 2020

    Hi
    that very good
    But I have reach to less than 1 ohm of earth resistance by my special way


  2. Mohammad H. Hamdi
    Jul 22, 2020

    Hi
    can any one tell us the IEC standard for earthing resistance value in general in Oil fields please.

    thanks


  3. Carlos C. Tamayo Jr.
    Jun 25, 2020

    Seeking your support, appreciate if you could share to me MV Protection coordination study sample.


  4. Garba musa
    Jun 19, 2020

    Sir what is the correct value for earth trasformer


  5. Muhammad Shaheryar
    Apr 06, 2020

    There is no NEC 50.56.
    NEC 250.56 11th edition stated 25 ohms and less.
    NEC 250.56 is excluded from 12th edition


  6. Emeka Chime
    Feb 24, 2020

    In my company, a telecommunication giant in Nigeria, the standard earth resistance value ranges from 2.0 Ohms and below.


    • andy chan
      Feb 27, 2020

      Dear Emeka Chime,

      Please let me know, the standard earth resistance value ranges from 2.0 Ohms, the 2.0 ohms is quote from what authority or international standard?

      Thanks so much


  7. SOJI
    Jan 15, 2020

    Very Educative … Thanks Edvac …!


  8. Ali
    Dec 31, 2019

    is there any reference about the resistance value between clean and dirty earths.


  9. Kimetu
    Dec 07, 2019

    Nice one, very educative, can i get a earth resistance tester and at how much


  10. Satti
    Nov 28, 2019

    I have checked the earth resistance and it’s result is point zero one six seven so kindly tell me about the earth, that is good or not
    Result= .0167


    • Faisal Mohamed
      Oct 23, 2020

      Very good


  11. Eng. Seth Wilson
    Nov 04, 2019

    Hi, meter reads o.23 Ohms, is this good or bad?


    • MOHAMED MOUSTAFA
      Jul 05, 2020

      yes very good


  12. Ugama Albert
    Oct 18, 2019

    I installed a 5kva inverter in a house that has a thunder arrester and it’s earted. But the inverter was still destroyed by thunder. This made me to to run a test on the earthing and was discovered it was 27ohms. How come it was only the inverter that was affected and not the house appliances as well


    • LalitKishor
      Nov 04, 2019

      Because inverter has an isolation transformer and surge circuit inside to avoid cascading the fault current goes.to other appliances


  13. Mahesh
    Oct 04, 2019

    Earthing for Any equipments is Design always request customer for Soil ERT Reports and Design for Equipments or any Kind of Grid.
    Earth Enhance Compound Role is bigger than Metal Part becuse we use Metal to consider Falut Current and Life for Metal but without Good and Quality Compound its not possible.
    Avoid to use any mineral who can Damager or Corrosion your Metal Later .
    India Follow IEC as well IEEE .using CDEGS Software for Desiging Earthing and Lightning
    We has to mentioned Latest Tech Documents is our inquiry or Tender
    M-91-9910398999


  14. Mr G. T Apera
    Sep 04, 2019

    Like to buy Tong earth tester like in the photo please get back to me.


    • Mr G. Apera.
      Sep 02, 2020

      Would like to buy an earth tester (ideal ground resistance meter)


  15. Prashant shalikram pustode
    Aug 24, 2019

    Sir sgp course available ?

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