Main features in earthing

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

6. temperature

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

12. Copper clad steel rod ( copper shrunk onto the core)

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