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
