What is Earth Resistance?
The resistance of the earth electrode to the current flow into the earth is known as an earth resistance. The resistance between the earth and the earthing plate is measured through a potential fall method.
Numerically, it is equivalent to the ratio of the earth electrode’s potential to the current disappeared by it. The resistance between the earthing plate and the earth is assessed through the potential fall method.
The earthing resistance value is based upon the soil resistivity, construction design, and climate-related condition. Moisture in soil plays a critical role in the resistivity of the soil. Different types of codes indicate the desired value of an earthing system.
The acceptable earth resistance value in India is are follows:-
US AID | Earthing Practices of India by MVS Brinch
|(1) Power stations||0.5 ohms|
|(2) EHT Sub-station||1.0 ohms|
|(3) 33 KV Stations||2.0 ohms|
|(4) D/t Structure||5.0 ohms|
|(5) Tower Foot Resistance||10.0 ohms|
Chapter 4 of IEEE standard 142-2007
|Resistance suitable for industrial plant|
Sub-stations, buildings & large installations
|1 ohm to 5 ohms|
IS 2309: 1989, Cl 12.3.1 Page 32 and BS 7430:1998
|Cl 9.4.3 Lightning arrestors ground resistance for Protection of allied|
structures & buildings
Guide to control Undesirable Static Electricity
|Lightning arrestors ground resistance for Protection Of allied structures|
IS 2689:1989, Table 4 page 28 (Reaffirmed March 2010)
|Lightning arrestors ground resistance for Protection of buildings and|