1 OF 2

305260211.xls.xls

LARSEN & TOUBRO LIMITEDELECTRICAL DIVISION, H.Q., CHENNAI

PROJECT REF. NO. PAGE :

Relocation of Riyam Substation and Transformer

Repair Workshop PREPARED CHECKED APPROVED DATE

TITLE

EARTHING CALCULATIONS SSJ AKR AKS 22-Feb-16

INPUT DATA

1 Soil resistivity = 26 Ohm.m2 Type of conductor used = Copper Flat 3 Length of Grid buried in ground L = 275 m4 Depth of burial of electrode w = 0.5 m5 Length of Rod or Pipe l = 3.5 m6 Dia of Rod or Pipe d = 0.016 m7 No. of Electrodes n = 148 Distance between adjacent rods s = 7 m9 P(Ref: Table 5 BS 7430:1991) = 2

10 Q(Ref: Table 5 BS 7430:1991) = -1.3

CALCULATIONS

8lA Resistance of one vertical Electrode R = ------------ LOGe -------- - 1

2*phi*l d= 7.650 ohms

Net resistance of Electrodes Re = Rr/n

= 0.546443675 ohms

B Resistance of horizontal Buried Rh = ------------ x LOGe ----------

Earth grid P x Phi x L w *d= 0.278 ohms

R x RhC Net Resistance R = -------------

R + Rh= 0.184 ohms

RESULT

Since the total Resistance is less than 1 ohm, earthing for this area is SAFE.

2*L2

-----+ Q2

CONSTRUCTION GROUP

2 OF 2

305260211.xls.xls

LARSEN & TOUBRO LIMITEDELECTRICAL DIVISION, H.Q., CHENNAI

PROJECT REF. NO. PAGE :

Relocation of Riyam Substation and Transformer

Repair Workshop PREPARED CHECKED APPROVED DATE

TITLE

EARTHING CALCULATIONS SSJ AKR AKS 22-Feb-16

CONSTRUCTION GROUP