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8. Calculate Qty of Chemical Earthing Material & Size of Earthing Rod

CALCULATE QTY OF CHEMICAL EARTHING MATERIAL & SIZE OF EARTHING ROD

Calculate Qty of Chemical Earthing and size of Earthing Rod for following specification.

  • Earthing Bore Hole (Auger) size is 150MM and Length is 3Meter. * Chemical Earthing Material is available in Bag of 25Kg.Mixing Ratio of Earthing Compound and Water is 2:1. * Earthing Rod Material is GI and length is 3 Meter. * Size of Transformer for Upstream of Electrical Network is 2000KVA,430V,8%Impedance and consider Short Circuit Current is for 0.5Sec.

CALCULATION:

(A) CALCULATE REQUIRED CHEMICAL EARTHING MATERIAL

  • Volume of Bore Hole = π r² x h * Volume of Bore Hole = 3.14 x (0.150/2) ² x 3.0 * Volume of Bore Hole = 0.053 m3 * Chemical Earthing in one Bag=25Kg * Volume of Chemical Earthing material (Dry) in one Bag = Bag weight in kg x 0.00117 m3 * Volume of Chemical Earthing material (Dry) in one Bag = 25 x 0.00117 m3 * Volume of Chemical Earthing material (Dry) in one Bag = 0.02925 m3 * Mixing Ratio of Earthing Compound and Water is 2:1 * Hence Volume of Chemical Earthing material (Wet) in one Bag =0.02925×2 m3 * Volume of Chemical Earthing material (Wet) in one Bag =0.0585 m3 * Required Chemical Earthing material = Volume of Bore Hole x Bag Weight / Volume of Chemical Earthing material (Wet) in one Bag * Required Chemical Earthing material = 0.053×25 / 0585 Kg * Required Chemical Earthing material =22.5 Kg * Required Chemical Earthing material = Volume of Bore Hole / Volume of Chemical Earthing material (Wet) in one Bag * Required Chemical Earthing material = 0.053 / 0.0585 * Required Chemical Earthing material = 0.9 Bag

(B) CALCULATE SIZE OF EARTHING ROD

  • Transformer Full Load Current= Size of Transformer/ 1.732XVolt * Transformer Full Load Current= 2000×1000 /1.732×430 * Transformer Full Load Current=2685Amp * Short Circuit Current = Transformer Full Load Current / Transformer Impedance * Short Circuit Current = 2865 x100 / 8 * Short Circuit Current =33567.86 Amp * Short Circuit Current =33.6 KA * Earthing Rod Size= √ (Fault currentx2 x Fault Time) / k * Where K for GI=80, Aluminium= 126, Copper=205 * Earthing Rod Size=√ (33567.86)2 x 0.5 / 80 (Sq.mm) * Earthing Rod Size=296.70 Sq.mm * Earthing Rod Size= π d² / 4 (mm) * Diameter of Earthing Rod =√ Earthing Rod Size x 4 / 3.14 * Diameter of Earthing Rod =19.4mm * Length of Earthing Rod=3 Meter