Chemcial Earthing Electrode :

Earth Resistance
Earth Resistance and How it should be low

• No electric circuit either single phase or three phases is complete without proper earthing
• The earthing or grounding is associated with earthing strips, earth plate
• Electrodes Fastening or welding Proper
• Resistance of earth, Resistivity of Soil
• Unless all these are stable & healthy the word good earthing will have no meaning or value. To understand why earthing resistance must be low, use ohm' law.

V ∝ I
V = R x I (where V is Voltage in Volts an R is Resistance in Ohm and I is current in ampere.)
R = ǫL/A (where, R is resistance of electrode. Ǫ is substance of electrode, L is length of electrode, A is Area od electrode)
R = R° (1+∝ ∆ T (where ∆ T is Changing temperature, ∝ is temperature coefficient)

(If Temperature is down than resistance will be less)

Earth Resistance Depends on Following Factors	Maximum Earth Resistance is Followed as Below
Temperature of Earth	L.T. lighting Arresters 4
Type of earth soil	Major Power stations 0.5
Minerals in Earth	Major sub stations 1.0
Humidity in Earth	Service connection 4
Electrode shape and size	Minor sub stations 2
Length of electrode in the earth	Neutral bushing 2
Electrode shape and size	Towers 20-30
Number of electrodes	H.T. Poles 10
Distance between two electrodes	L.T. Ploes 5

ADVANTAGES

• Safety and Reliability
• Low impedance Earthing
• Ensure Safety of life and property from earth related electrical hazards
• Longer service life than conventional earthing systems
• Corrosion resistance