Following reasons earthing is essential in electrical installation :
1. To provide an alternative path for the leakage current to flow towards earth. 2. To save human life from danger of electrical shock due to leakage current. 3. To protect high rise buildings structure against lightening stroke. 4. To provide safe path to dissipate lightning and short circuit currents. 5. To provide stable platform for operation of sensitive electronic equipment’s.
Diagram for Pipe Type earthing :
Excavation on earth for a normal earth Pit of size 2.7 M X 0.6 M X 3.0 M.Or 4.5 M For Pipe type earthing normal practice is to use; GI pipe [C-class] of 75 mm diameter of length Having 6 numbers of holes for the connection of earth wires Normal Practice is to use GI earthing pipe of length as per requirement. Cover Top of GI pipe with a T joint to avoid jamming of pipe with dust & mud. These types of earth pit are generally filled with alternate layer of charcoal & salt up to 4 feet from the bottom of the pit. The electrical installation which to be earthed, is connected to the top of the earth pipe by means of copper or aluminium earth continuity conductor of sufficient cross-section. Normal practice is to use GI earthing wire of 10/8/6 SWG as per requirement
(2) Plate type Earthing:
Excavation on earth for a normal earth Pit size is 1.5M X 1.5M X 3.0 M. Specifications: Generally for plate type earthing normal Practice is to use GI earthing plate of size mentioned below as per requirement. GI strip of size 40×6 mm or 50 mmx6 mm bolted with the plate is brought up to the ground level or Cu Strip of size 25×3 mm or 40×3 mm or 50×3 mm is used if Copper plate is used. These types of earth pit are generally filled with alternate layer of charcoal & salt up to 4 feet from the bottom of the pit.( Amount of Salt and Charcoal more than 8Kg) Make a mixture of Coal Powder Salt & Sand all in equal part. Because of following reasons- 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. Use of Coal Powder also beneficial as it is 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. Prepare a Concrete chamber of size 450mm×700mm as shown in fig. and close the chamber by removable C.I. plate. Make arrangement with the help of G.I. pipe of size 19mm and funnel for pouring the water in earth pit when required.