Gandhinagar Insti tute of Technology

Elements of Electrical Engineering

“Topic: Earthing”

Guided By: Prof. Rahish Silavat

Branch : Mechanical Engineering Div: L-3

Group Member

• Harshil Zaveri(130120119251)

EARTHING

WHAT IS EARTHING? The term Earthing means the connection of

the neutral point of the supply system or non current carrying parts of electrical apparatus, such as metallic frame work, metallic covering of cables, earth terminal of socket outlet, stay wire etc. to the general mass of earth in such a manner that at all times immediate discharge of electrical energy takes place without danger.

VARIOUS CIRCUIT DIAGRAM OF EXPLAINING EARTHING

PURPOSE OF EARTHING• To save human life from danger of electrical shock or death

by blowing a fuse i.e. To provide an alternative path for the fault current to flow so that it will not endanger the user

• To protect buildings, machinery & appliances under fault conditions   ie. To ensure that all exposed conductive parts do not reach a dangerous potential.

• To provide safe path to dissipate lightning and short circuit currents.

• To provide stable platform for operation of sensitive  electronic equipments   i.e. To maintain the voltage at any part of an electrical system at a known value so as to prevent over current or excessive voltage on the appliances or equipment . 

• To provide protection against static electricity from  friction      

GOOD EARTHING MEANS

Good Earthing must have low impedance enough to ensure that sufficient current can flow through the safety device so that it disconnects  the supply ( <0.4 sec ). Fault current is much more than the full load current of the circuit which melts the fuse. Hence, the appliance is disconnected automatically from the supply mains.

QUALITIES OF GOOD EARTHING

Must be of low electrical resistance • Must be of good corrosion resistance • Must be able to dissipate high fault current repeatedly

VARIOUS METHOD OF EARTHNG

1. Strip Earthing2. Earthing through water

mains3. Rod Earthing4. Pipe Earthing5. Plate Earthing

(1) STRIP EARTHING

This system of Earthing employees the use of copper wire or strip of cross section not less than 25 mm X 1.6 mm.

The strips or wires are burried in horizontal trenches.

This type of Earthing is used where the earth bed has a rocky soil and excavation work is difficult.

(2) EARTHING THROUGH WATER MAINS

In this type of Earthing, standard copper lead is used which is rounded on the pipe with the help of a steel binding wire and properly designed Earthing clip.

The copper lead is soldered to make it solid. Before making connection to the water main,

it should be ensured that G.I pipe is used through out.

(3)ROD EARTHING

It is the cheapest method of Earthing and is employed in sandy areas.

In this method, a copper rod is hammered directly into the earth and no excavation work is required.

The Earthing lead is joined to this rod with the help of nuts and bolts

(4) PIPE EARTHING

PIPE EARTHING Pipe earthing is best form of earthing and it is cheap also in this system

of earthing a GI pipe of 38 mm dia and 2meters length is embedded vertically in ground to work as earth electrod but the depth depend upon the soil conditions, there is no hard and fast rule for this.

But the wire is embedded upto the wet soil. The earth wire are fastened to the top section of the pipe with nut and

bolts. The pit area arround the GI pipe filled with salt and coal mixture for

improving the soil conditions and efficiency of the earthing system. It can take heavy leakage current for the same electrode size in

comparison to plate earthing. The earth wire connection with GI pipes being above the ground level

can be checked for carrying out continuity test as and when desired, while in plate earthing it is difficult.

In summmer season to have an effective earthing three or four bucket of water is put through the funnel for better continuity of earthing.

PLATE EARTHING

PLATE EARTHING In this type of earthing plate either of copper or of

G.I. is buried into the ground at a depth of not less than 3 meter from the ground level.

The earth plate is embedded in alternative layer of coke and salts for a minimum thickness of about 15cm.

The earth wire(copper wire for copper plate earthing and G.I. wire for G.I. plate earthing) is securely bolted to an earth plate with the help of bolt nut and washer made of copper, in case of copper plate earthing and of G.I. in case of G.I. plate earthing.

APPLICATIONS

• Telecommunication • Transmission• Substations & Power Generations• Transformer Neutral earthing• Lightning Arrestor Earthing• Equipment Body Earthing• Water Treatment Plants• Heavy Industries• College, Hospitals, Banks• Residential Building

Thank You