Answer / mahamuni raja

to determine the no.of earthing pits required is depends
uponn the area required to dissipate the fault courrent to
the area of pipe electrode.
To protect 35M building , 1no. of lightning arrestor is
sufficient however better to provide two nos.of down
conductors hence to protect the building if any one
conductor fails.

Answer / jagjeet

The LE installed on the Top of 35 mtrs high building covers
the redial distance of 35 mtrs across the LE on ground
level so the no. of LE not only depend on Height of the
building but the others dimensions of the buildings.

Answer / william lobo

The number of earthing pits depends on the soil resistance.
We may require earth resistance of 1ohm or 3 ohms at the
most. To get this we will have to install at least 2 pits
and as per parallel formula i.e. 1/r1+1/r2+1/r3= 1/R. We
have to keep on increasing the number of earth pits till we
get the required value for R=1 or 3 as per requirement.

Answer / anand

it is depends on what extent you need the safety level.

Answer / ramasubramanian.ganesan

Normally the area which is covered by a lighting arrester
calculated on the basis of PYTHAGAROUS statement.

In a right angled triangle, the sum of sqr.root of the
adjacent and opposite sides is equal to the sqr root of the
third side.

In the question asked the height is 35 meters. based on the
above we have to calculate the required datas.

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