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Earthling
Earthling
Earthling
Earthling
Earthling
Earthling
Earthling
Earthling
Earthling
Earthling
Earthling
Earthling
Earthling
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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=2πAd
    ρ=soil resistivity
    A=Apperant resistance
    D=distance between adjacent electrode
  • 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

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