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# Earthling

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Main features in earthing

Main features in earthing

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### Transcript

• 1. Earthing
G.V. Nilanka
• 2. Content………..
purpose of earthing
Earthing design
Soil resistivity testing
Resistance to earth of a rod or pipe electrode
Resistance to earth of a strip
Resistance to earth of a infill material
• 3. purpose of earthing
We provide a direct path to fault current.
What is fault current?
By earthing we can get common reference potential in electrical system.
There are several earthing arrangement
To achieve good earthing,a suitable low resistance to earth is desirable.
• 4. Earthing design
Using Rods or pipe
Using Strip
Using Infill material
Using foundation
• 5. Soil resistivity testing
This varies with some parameters.
• moisture content
• 6. temperature
• 7. Depth
• Soil resistivity testing
• 8. Calculate the soil resistivity
ρ=soil resistivity
A=Apperant resistance
• 9. Resistance to earth a rod or pipe electrode
R=ρ(ln(8l/D)-1)/2πL
L =length of electrode
D=diameter
ρ = resistivity of soil
• 10. Cont….
l varies with electrode arrangement
• 11. Three types of copper rods are commonly available.
• Solid Copper
• 12. Copper clad steel rod ( copper shrunk onto the core)
• 13. Copper Bonded steel core (copper is molecularly bonded to nickel plated steel rod)
• Resistance to earth of a strip
L – length of the strip
h - the depth buried
w - width of the strip
P and Q are coefficient for strip or round conductor
Rn=FR
• 14. Resistance to earth of a infill material
Where
ρ = resistivity of soil in Ω-m
ρc = resistivity of infill material Ω-m
d = Diameter of the electrode – m
D = Diameter of infill – m
L = Driven Length – m
• 15. Thank You