__Calculate Min. Cross Section area of Earthing Conductor__Cross Section Area of Earthing Conductor As per IS 3043 (A) =(If x√t) / K

Where: t = Fault current Time (Second).

K = Material Constant.

**Example:**

Calculate Cross Section Area of GI Earthing Conductor for System has 50KA Fault Current for 1 second. Corrosion will be 1.0 % Per Year and No of Year for Replacement is 20 Years.

Cross Section Area of Earthing Conductor (A) =(If x√t) / K

Here: If = 50000 Amp

T = 1 Second

K = 80 (Material Constant, For GI=80, copper K=205, Aluminium K=126).

Cross Section Area of Earthing Conductor (A) = (50000×1)/80

Cross Section Area of GI Earthing Conductor (A) = 625 Sq.mm

Allowance for Corrosion = 1.0 % Per Year & Number of Year before replacement say = 20 Years

Total allowance = 20 x 1.0% = 20%

Safety factor = 1.5 Required Earthing Conductor size = Cross sectional area x Total allowance x Safety factor Required Earthing Conductor size = 1125 Sq.mm say 1200 Sq.mm

Hence, Considered 1Nox12x100 mm GI Strip or 2Nox6 x 100 mm GI Strips