Comparison of Chemical And Conventional Earthing
What is Conventional Earthings?
The conventional method of Earthing is by using a 600mmx600mm plate of Copper or Galvanized Iron Plate of thickness 3 to 5 mm, placing it in a 4 feet x 4 feet hole of 10 feet depth, back filled by alternate layers of salt and charcoal. The plate connected by GI Strip or Copper strip to the protecting equipment. Above the plate till the surface of the earth, normal soil is back filled. Also a pipe preferably of GI is osed to water the plate surrounding at the top with a filter and a cone. Conventional earthings had been very common and it was presumed that with increasing area, the Earth Resistance shoud reduce, with Ohms law. In the following paragraph we will discuss few disadvantages and why Chemical earthings are so Popular now a days, if sourced from a dependable agency.
The major disadvantage of Plate type earthings are the following:
1. The common salt used for encircling the plate corrode the earthing plate itself. The weakest link is, the joint of copper plate to earth strip that connects the plate to the equipment. The corrosion damage the plate and connector and reduce the fault carrying capacity slowly till the time it is completely disconnected and earthing no longer working.
2. The salt leaches out continuously with the rain water. This reduces the salt present surrounding the earth and make the layer porous. With time, the salt icompletely leached out with percolated rainy water and capacity of the plate to feed the fault current to surrounding soil reduces.
Further, as per BS:7430 and other standards, the effect of the Diameter or width of the strip or plate is very limited. Pl watch attached video here below showing this phenomena how inefficient is plate earthing in comparison to Pipe or Plate Earthing.
Another disadvantage is stability of earthing resistance. In conventional earthing, with time surrounding salt leaches out and corrode the plate and only as effective as the length of the plate in comarision to the long pipe more effective. With time, the performance of the conventional earthing depends upon the periodicity of watering and in absence of this it even fails. It also therefore necessitates more periodic maintenance of earthing than the Chemical Earthing.
The foot print in Chemical Earthing is much less, 8-10 inch augured hole 10 feet long keeping 2 inch Pipe earthing in it, strip in pipe or pipe in pipe as per customer specifications or engineer requirement depending upon the primary conductor cross section requirement. The back fill compound is most important characteristics of chemical earthing, which helps to maintain the moisture and in turn conductivity of the surrounding soil over a very long time. The moisture carrying capacity and increasing volume with water, which exerts pressure on the walls of earthing and surrounding soil. Further, its also help to improve the moisture and conductivity in surrounding soil which is most effective in contributing the earthing resistance or performance of the earthing.
Therefore, the Chemical earthing is cheaper, employ less foot print and require less maintenance, i.e. only annual or semi annual.