Conventional methods of earthing
1. Plate type Earthing

Generally for plate type earthing normal Practice is to use
Cast iron plate of size 600 mm x600 mm x12 mm. OR
Galvanized iron plate of size 600 mm x600 mm x6 mm. OR
Copper plate of size 600 mm * 600 mm * 3.15 mm
Plate burred at the depth of 8 feet in the vertical position and GI strip of size 50 mmx6 mm bolted with the plate is brought up to the ground level.
These types of earth pit are generally filled with alternate layer of charcoal & salt up to 4 feet from the bottom of the pit.


2. Pipe type Earthing

For Pipe type earthing normal practice is to use GI pipe [C-class] of 75 mm diameter, 10 feet long welded with 75 mm diameter GI flange having 6 numbers of holes for the connection of earth wires and inserted in ground by auger method.

These types of earth pit are generally filled with alternate layer of charcoal & salt or earth reactivation compound.

Method for Construction of Earthing Pit

Excavation on earth for a normal earth Pit size is 1.5M X 1.5M X 3.0 M.
Use 500 mm X 500 mm X 10 mm GI Plate or Bigger Size for more Contact of Earth and reduce Earth Resistance.
Make a mixture of Wood Coal Powder Salt & Sand all in equal part
Wood Coal Powder use as good conductor of electricity, anti corrosive, rust proves for GI Plate for long life.
The purpose of coal and salt is to keep wet the soil permanently.
The salt percolates and coal absorbs water keeping the soil wet.
Care should always be taken by watering the earth pits in summer so that the pit soil will be wet.
Coal is made of carbon which is good conductor minimizing the earth resistant.
Salt use as electrolyte to form conductivity between GI Plate Coal and Earth with humidity.
Sand has used to form porosity to cycle water & humidity around the mixture.
Put GI Plate (EARTH PLATE) of size 500 mm X 500 mm X 10 mm in the mid of mixture.
Use Double GI Strip size 30 mm X 10 mm to connect GI Plate to System Earthling.
It will be better to use GI Pipe of size 2.5″ diameter with a Flange on the top of GI Pipe to cover GI Strip from EARTH PLATE to Top Flange.
Cover Top of GI pipe with a T joint to avoid jamming of pipe with dust & mud and also use water time to time through this pipe to bottom of earth plate.
Maintain less than one Ohm Resistance from EARTH PIT conductor to a distance of 15 Meters around the EARTH PIT with another conductor dip on the Earth at least 500 mm deep.
Check Voltage between Earth Pit conductors to Neutral of Mains Supply 220V AC 50 Hz it should be less than 2.0 Volts.
http://electrical-engineering-portal.com/earthing-in-electri...

Neutral and generator body should be earthed in separate earthing pits on opposite sides of the generator side