Thursday, April 17, 2014

is Copper as earth pit is better then GI earth pit?

It has been often found that most of think that material used for earthing will reduce earthing resistance.
It has been often misconception that copper earthing plate or rod will have lower earth pit resistance then GI earthing plate or rod.

Lets clear this fundamental regarding as often falling in this trap will lead to higher investment on earthing by using copper as earthing material.

If one considers a plate electrode, the approximate resistance to earth is:

Resistance formula for Pipe earthing

(R) = (100r/2πL) X loge (4L/d)
·          L= Length of Pipe/Rod in cm
  • d=Diameter of Pipe/Rod in cm
  • r = Resistivity of Soil Ohm-meter.

Resistance formula for Plate earthing

(R) = (r/A) X under root(π/A).
·         r = Resistivity of Soil Ohm-meter.
·         A=Area of Earthing Plate m3.

As can be seen from the above formulas, only the resistivity of the soil and the physical dimensions of the electrode play a major role in determining the electrode resistance to earth.

The material resistivity is not considered anywhere in the above formulas.

Hence, irrespective of the material of construction of the earth electrode, any material of given dimensions would offer the same resistance to earth.

Material will help in the sizing and number of the earthing conductor or the protective conductor. Because, the short time withstand current ratings do vary according to the material of construction of the conductor.

So Never waste on putting more money on Copper earthing instead of GI earthing.