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VALUE UNIT

50 KA1 sec

50 cm

= I X sqrt (t) / k 625 sqmm50 KA1 sec

80

1.1 x 625 687.5 sqmm

400 m

2 l w x t

20 -m

40000 cm7.5 cm50 cm

Ra = 0.13

2 dWhere,

300 cm6.5 cm

Rb = 5.54

6 0.92

1/ R ab 1/R a + 1/R bb

Rab Ra x R b / (R a + R bb)

Rab 0.11169388

VALUE UNIT

50 KA1 sec

50 cm

= I X sqrt (t) / k 625 sqmm50 KA1 sec

80t = Operating time in (secs) =k = 80 for steel as per IS-3043

I = Faulth Current (KA) =

TECHNICAL DATAa) Resistivity (avg.) of soil ( ) - m =

20 -m= (27.11+20.11+14.79+14.32+15.62)/5=18.39 say, 20(Reference Geotechnical report)b) Maximum fault current (I) - KA (rms) =c) Duration of shock (t) considered as sec.d) Depth of Burial of conductor (h) - cm

RESISTANCE OF EARTHING MAT:

Required Size of Earthing Grid (S)

Ground Resistance is less than 1.0 , hence the calculation is OK

Therefore 6 nos. of Earth Pits Provided are OK.

PRIMARY REQUIREMENTa) The impedence to ground (Over all resistance of the earthing system)should not exceed 1.0 as per IS:3043

EARTHING CALCULATION FOR PLANT AREA FOR BTP

Rab = Total earth resistance

Resistance of one electrode in isolation:(Refer IS-3043-1987)

Rb = 100 Ln 4l

L = Length of electrode in cmD = Diameter of electrode in cm

Since Over all resistance for 1 Electrode should be

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