GROUND ELECTRODEGROUND ELECTRODE

• The resistance of metal and that of the conection to it.The resistance of metal and that of the conection to it.

• The contact resistance of surrounding earth to the electrode.The contact resistance of surrounding earth to the electrode.

• The resistance in the surronding earth to current flow or earth The resistance in the surronding earth to current flow or earth resistivity which often most significan factor.resistivity which often most significan factor.

Ground resistance derived Ground resistance derived from general formulafrom general formula

A

LR

.

Area

Lengthsistivitycesis RetanRe

This formula illustrate in the This formula illustrate in the shells of concentric earthshells of concentric earth

Area

shellofThicknesSoilofsistivityR

....Re

• R R =Resistance of the ground rod to the =Resistance of the ground rod to the earth in ohms earth in ohms

• LL =Grounding electrode length=Grounding electrode length

• RR = Grounding electrode radius= Grounding electrode radius

• = average resistivity in ohms- cm = average resistivity in ohms- cm

r

LLn

LR

14

2