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.
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.”
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.
Reference: Fluke Earth Ground Testing Fact – Distributor Training Program
SANS10142-1 WIRING REGULATIONS CONTAINS THE PRINCIPLES TO BE FOLLOWED FOR THE WIRING OF PREMISES.
No one reads the questions so why ask
What is earth fault ?
i got a reading of 5.81 ohms on a changeover switch gear earth point while the generator (350KVA) earth point gave a reading of 1,89 ohmns, is it safe?
My enquiry is what is the value expected amp/ohm on Ground Pipeline ?
I just performed a Ground Protection between Pipeline & offshore structure what tie in to the Sea Bed Anode ground is Cadweld on Pipeline which is coming from Offshore 30 inch Pipeline going onshore due to allow welding activities while the Pipeline is in-service liquids onto is Crude.
Question what is the amp value ?
You Mentioned In the article
NEC 50.56 Actually It Shall Be NEC 250.56
I don’t see 50.56 in the NEC. I don’t see a 250.56 either, what year of the NEC you are using, please advise. Thank you.
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.
I need to learn
What should be ground ohms for 10kva solar powered system?