Earthing Grid Calculations For Khondbond R3 For Approval

CALCULATION NO TATA PROJECTS LIMITED
SHEET 3 OF 25
TPL-039-EDC-8001 EARTHING CALCULATION
Reference standard : IS 3043
1. CONDUCTOR SIZING
1.1) Earthing Conductor Sizing

Earthing system is a grid arrangement of conductors buried in the soil, designed to carry and
dissipate fault current.
Input data :-
(i) Conductor material = Mild Steel MS
(ii) System Voltage = 0.415 kV
(iii) Fault Current, If = 50 kA
(iv) Fault Daration, tc = 1 sec
(v) Max. Allowable Temperature, θf = 500 0

C See note
(vi) Ambient Temperature, Ta = 50 0

C
(vii) Intial Temperature, θ i 40 0

C
(viii) Electrical resistivity of conductor

material at 20 deg.c, ∂20 = 0.000138 ohm mm
(ix) Volumetric heat capaciy of conductor

material, Qc = 0.0038 J/(mm3.oC)
(x) Reciprocal of temperature coefficient of = 202

resistivity at deg.c for conductor, B
Conductor Size :-
As per IS,
(B+20) θf - θ i
A= If. t K = QC log e 1 +
K δ 20 B+θi
Substituting the input data, we get
K = 80.69
A 619.68 sq.mm
Diameter of the earthing conductor = 28.10 mm
Allowance for corrosion considered as per specification Clause no 2.3 1.50 mm
= 29.60 mm
Size of the conductor required = 30
Hence, the conductor selected = 40.00 mm dia Rod
to standard size
As per calculation 32mm Dia rod is sufficient, however as per MOM 29-11-2012 Note number 25 page 20 of 22
40mm dia MS rod is been mentioned and same is considered
NOTE:Since jointing of grid conductors are by arc welding, maximum allowable
temperature considered is 500 deg.c as per IS-3043

SHEET 4 OF 25
Reference documents :
a) IS 3043
b) Soil Resistivity Report :Attached
c) Plot plan (Dwg no. TCE.6928A-04-SK-0002, Rev : R1)
Number of 3.5Mtr, No of 20 Mtr 1.5Mtr

Ground Grid 3.5Mtr 40mm
Area Wise 40mm Dia, GI Pipe Deep Bore 40mm Dia
S.No Resistance in Dia Driven Remarks Condu
Description Electrodes Earth 100mm Dia GI Driven
Ohms Rods ctor
pit(Np): Pipe Earth Pits Rods
Length
170 Refer Group-1

1 Group-1 (R1) 2.20 15 Calculation Sheet 568.43
200 Refer Group-2

2 Group-2 (R2) 1.57 20 Calculation Sheet 552
110 Refer Group-3

90 Refer Group-4
160 Refer Group-5

1 60 Refer Group-6
75 Refer Group-7
15 295 350 Refer LCSS-1

8 LCSS-1 (R8) 0.90 40 Calculation Sheet 856
15 295 374 Refer LCSS-2

10 20 666 Refer MPDS

10 MPDS (R10) 0.91 20 Calculation Sheet 3042
20 750 300 Refer LCSS-3

11248
1/Rz=1/R1+1/R2+1/R3+1/R4+1/R5+1/R6+1/R7+1/R8+
1/R9+1/R10+1/R11
Paralleling of all the Zones
1/RZ 10.46
Value of RZ 0.096
Conclusion
The Earth resistance of whole plant area is 0.096(Ω) which satisfies the requirement of Earth resistance of
overall to be lower than 1(Ω).
a. Size of Mild steel conductor buried in ground - 40mm Dia Rod.

b. Earth Resistance : 0.096Ohms
No of driven rods apart from node rods will be placed along the building periphery and at free space
NOTE: 1
which will be connected to main grid.
2 Location of earth pits will be finalised during layout drawings.
3 Neutral earth pits are not considered for the above sizing calculation.
4 All Building Dimensions are approximate however their can be variation at a later date.
5 Dedicated Electronic Earth pit will be considered separately for electronic equipments.
6 Earthing conductor along the pipe rack structure to the slime dam area is not considered
in the above calculations. How ever by considering the same the Resistance value further come down.
7 Any other area which is not considered in the above calculation will be shown in Composite
Earthing Layout
8 Earth conductor and Inter connection rods buried 600mm from Finished Ground level
9 Zones are marked in enclosed Annexure-1 for Reference.
For Weigh Bridge area which is isolated from main grid for present operation , for this area good soil to be used for
10 achieving required Grid resistance.
SHEET 5 OF 25
LCSS-1
1 Input Data :
1 System Voltage, Vs = 6.6 kV
2 System fault Current, If (rms sym. g/f current) = 22 KA
3 Fault Duration, t = 1 sec
4 Avg.Soil Resistivity, r = 2266.82 W-metre
5 Grid Spacing = 2 Mtr
6 Length in X Direction = 48 Mtr
7 Length in Y Direction = 17 Mtr
8 No. of conductor along length = 24 Mtr
9 No. of conductor along breadth = 8.00 Mtr
10 Total conductor used along length in m. = 408 Mtr
11 Total conductor used along breadth in m. = 384 Mtr
12 Conductor length in the horizontal grid in m.(Lc). = 792 Mtr
13 4MtrX4 Mtr Auxiliary Grid for Four Corners = 64 Mtr
14 Total Conductor length in the horizontal grid in m.(Lc). = 856 Mtr
15 Depth of burial strip, (w) = 0.6 Mtr
Calculation of Maximum Ground Potential Rise :
Max. Ground potential above remote earth, GPR = Ig x Rg Volts
Where,
Ig = grid current = I f x Sf
Rg= Grid Resistance = 0.90 Ohm

Sf = Fault current division factor
Ig = 11 KA at Sf = 0.5
Substituting the values,
Ground Potential Rise, GPR = 9939.26 Volts
As GPR is < 10kV,in this case no need to calculate Attainable touch and Step Potential.
SHEET 6 OF 25
2 Calculation for Resistance of one pipe electrode for deep bore (Re):
a) Resistance of one pipe electrode (Re) = 100ρ 4l
For deep bore ---------- In -----
2pi l d
(i) Length of pipe, L = 2000 cm
(ii) Diameter of pipe, D = 10 cm
(iii) Resistivity of one pipe electrode = 120.64 ohm
(iv) Number of Electrode = 15.00 Nos
(v) Effective Resistance = 8.04 Ohms
b)Calculation for Resistance of one driven Rod 1.5 mtr (Rp1):
For typically at evry node
(iv) Number of Electorodes = 350.00 Nos
c) Resistance of one Driven rod 3.5 Mtr (Rp2) = 100ρ 4l
---------- In -----
2pi l d

d) Resistance of one pipe electrode (Rp3)

= 100ρ 4l
Treated earth pit 3.5 Mtr
---------- In -----
2pi l d

SHEET 7 OF 25
Calculation for Resistance due to conductor :

e) Resistance due to interconnection of strip = 100ρ 2l2
---------- In -------
2pi l wt
(i) Length in strip, l = 85600 cm
(ii) Twice the dimeter (For Conductor in Cm), t = 8 cm
(iii) depth of burial strip, w = 60 cm
(iv) Resistance due to interconnection of strip = 7.27 ohm
For LCSS-1 Earthing Resistance(RG1) = 7.27 ohm

Effective Resistence
(1/RG1+1/Rp1+1/Rp2+1/Rp3+1/Re) = 1.11
Total Resistance = 0.90 Ohms

SHEET 8 OF 25
LCSS-2
1 Input Data :
12 Conductor length in the horizontal grid in m.(L c). = 1507 Mtr
14 Total Conductor length in the horizontal grid in m.(L c = 1571 Mtr
Max. Ground potential above remote earth, GPR = I g x Rg Volts
Where,
Ig = grid current = If x S f

Ig = 11 KA at Sf = 0.5
SHEET 9 OF 25

---------- In -----
2pi l d


c) Resistance of one Driven rod 3.5 Mtr (Rp2) = 100ρ 4l

---------- In -----
2pi l d

d) Resistance of one pipe electrode (Rp3)

= 100ρ 4l
---------- In -----
2pi l d

SHEET 10 OF 25

---------- In -------
2pi l wt
Effective Resistence = 1.11

(1/RG1+1/Rp1+1/Rp2+1/Rp3+1/Re)
= 0.90 ohm
Total Resistance
SHEET 11 OF 25
MPDS
1 Input Data :
11 Total conductor used along breadth in m. = 1350.00 Mtr
12 Conductor length in the horizontal grid in m.(Lc). = 2978.00 Mtr
14 Total Conductor length in the horizontal grid in m.(L = 3042.00 Mtr
Max. Ground potential above remote earth, GPR = Ig x R g Volts
Where,
Ig = grid current = If x Sf

Ig = 11 KA at Sf = 0.5
SHEET 12 OF 25

---------- In -----
2pi l d

(iv) Number of Electorodes = 10.00 nos

c)Calculation for Resistance of one driven Rod

= 100ρ 4l
3.5 mtr (Rp1):
---------- In -----
2pi l d

d)Resistance of one pipe electrode (Rp3) Treated

= 100ρ 4l
earth pit 3.5 Mtr
---------- In -----
2pi l d


SHEET 13 OF 25

---------- In -------
2pi l wt
(i) Length in strip, l = 304200.00 cm
= 2.40 ohm
For MPDS Earthing Resistance(RG2)
Effective Resistence 1.10
(1/RG1+1/Rp1+1/Rp2+1/Re)
0.91 Ohm
Total Resistance
SHEET 14 OF 25
LCSS-3
1 Input Data :
9 No. of conductor along breadth = 12 Mtr
12 Conductor length in the horizontal grid in m.(Lc). = 1225 Mtr
14 Total Conductor length in the horizontal grid in m.(Lc). = 1289 Mtr
16 Satelite earth dimensions (20X20mtr by 2 mtr grid spacing) = 440 Mtr
Max. Ground potential above remote earth, GPR = Ig x Rg Volts
Where,
Ig = grid current = I f x Sf

Ig = 11 KA at Sf = 0.5
SHEET 15 OF 25
---------- In -----
2pi l d
(v) Effective Resistance = 11.24 ohm


c)Calculation for Resistance of one driven Rod 3.5 mtr (Rp1):

d)Calculation for Resistance of one driven

= 100ρ 4l
Rod 3.5 mtr (Rp1)(For Satelite Earthing):
For typically at evry node ---------- In -----

2pi l d

(iv) Number of Electorodes = 350.00
(v) Effective Resistance = 3.22

SHEET 16 OF 25
e) Resistance of one pipe electrode (Rp3)

= 100ρ 4l
---------- In -----
2pi l d

(iv) Number of Electorodes = 75.00
(v) Effective Resistance = 15.01
f) Resistance due to interconnection of 2l2

= 100ρ
strip
---------- In -------
2pi l wt
g) Resistance due to interconnection of

strip (For Satelite area)
Effective Resistence (1/RG1+1/Rp+1/Re) = 1.10
Total Resistance = 0.91 ohm

CALCULATION NO TATA PROJECTS LIMITED SHEET 17 OF 25
Individual Area Earth Resistance for Group 1 :
Resistance of one pipe electrode (Rp1) Earth Pit = 100ρ 4l
---------- In -----
2pi l d
(i) Avg.Soil resistivity (ρ) in ohm-meter = 2266.82 W-metre

(ERT 01)
(ii) Length of pipe, L = 350 cm
(iii) Diameter of pipe, D = 4 cm
(iv) Resistivity of one pipe electrode = 604.13 ohm

(v) Number of Electorodes = 15.00 nos
(vi) Effective Resistance = 40.28 ohm
Resistance of one Driven Rod 3.5 Mtr (Rp2) = 100ρ 4l
---------- In -----
2pi l d

(ERT 01)

Typical Calculation for Resistance due to conductor :

= 100ρ 2l2
---------- In -------
2pi l wt
(i) Soil resistivity (ρ) in ohm-meter = 2266.82
(i) Length in strip, l = 23243.4 cm
Soil Length of Earthing Mutual

Depth of Number of Number of
Length in Width in resistivity (ρ) Earthing Resistance Resistance 3.5 Mtr, 40mm 3.5 Mtr, 40mm Effective value
S.NO Area Description burial in Ohms Rm =
Dia GI Pipe Dia MS of RG
m m in ohm- Ring in 1/RG+1/Rp1+
strip, (w) (RG) elctrodes (n) Driven Rod
meter cm 1/Rp2
PRIMARY CRUSHER WELL (DOUBLE

1 268.75 2266.82 0.6 23243.4 22.71 0.21 15.00 85.00 4.77
GRID) (R1) Area in m^2
COOLING TOWER (PCH) (DOUBLE

2 23 30 2266.82 0.6 21200 24.59 0.21 15.00 85.00 4.85
GRID) (R2)
DUST SUPRESSION SYSTEM - PUMP

3 13 9 2266.82 0.6 4400 92.68
HOUSE-1 (SINGLE GRID)(R3)
CANTEEN WITHOUT KITCHEN (FOR

4 26 14 2266.82 0.6 8000 56.37
200 MEMBERS) (SINGLE GRID)(R4)
5 MUTUAL RESISTANCE WITH COOLING TOWER GRID RESISTANCE R5=R3*R2/R3+R2 4.61
1/RG1= 1/R1+1/R4+1/R5
Paralleing of all the areas Value of
1/RG1 0.46
Value of RG1 2.20

Ohms
---------- In -----
2pi l d

(ERT-02)

---------- In -----
2pi l d

(ERT-02)


meter cm 1/Rp2
COOLING TOWER (SINGLE

1 18 15 2510.33 0.6 6600 73.34
GRID)(R1)
SECONDARY CRUSHER
2 17 15 2510.33 0.6 12800 41.95 0.20 20.00 100.00 4.92
HOUSE (DOUBLE GRID)(R2)
PRIMARY SCREEN HOUSE

3 20.5 17 2510.33 0.6 15000 36.64 0.21 20.00 100.00 4.84
(DOUBLE GRID) (R3)
TERITARY CRUSHER HOUSE

4 35 17 2510.33 0.6 20800 27.68 0.22 4.64
(DOUBLE GRID)(R4)
1/RG1=1/R1+1/R2+1/R3+1/R4
Paralleing of all the areas
Value of 1/RG1 0.64
Value of RG1 1.57

Ohms
---------- In -----
2pi l d

(ERT-02)

---------- In -----
2pi l d

(ERT-02)


Length in Width in resistivity (ρ) Earthing Resistance Resistance 3.5 Mtr, 40mm 3.5 Mtr, 40mm
Dia GI Pipe Dia MS
meter cm 1/Rp2
PLANT WATER AREA 0.6 22600 25.77

1 (SINGLE GRID)(R1) 78 35 2510.33
0.6 5800 81.67

COMPRESSOR
2 HOUSE(SINGLE GRID)(R2) 18 11 2510.33
CHILLER PLANT (SINGLE 0.6 4800 95.54

3 GRID)(R3) 18 6 2510.33
SCRUBBER, RINSING &
SCREEN HOUSE(SINGLE 0.6 12400 43.10 0.21 15.00 110.00
4 GRID)(R4) 39 23 2510.33
0.6 3600 120.99

5 TH3(SINGLE GRID) (R5) 11 7 2510.33
0.6 4100 108.77

6 TH4(SINGLE GRID)(R6) 10.5 10 2510.33
0.6 4200 106.64

7 TH5(SINGLE GRID)(R7) 12 9 2510.33
1/RG1=1/R1+1/R2+1/R3+1/R4+1/R5+1/R6
+1/R7
Value of 1/RG1 0.30
Value of RG1 3.35

Ohms
SHEET 19 OF 25
Effective value
of RG
4.76
Individual Area Earth Resistance for Group 4:
---------- In -----
2pi l d

(ERT-02)

---------- In -----
2pi l d

(ERT-02)


Length in resistivity (ρ) Earthing Resistance Resistance 3.5 Mtr, 40mm 3.5 Mtr, 40mm Effective value
S.NO Area Description Width in m burial in Ohms Rm =
m in ohm- Ring in 1/RG+1/Rp1+
meter cm 1/Rp2
SLIME DISPOSAL TANK/PUMP 0.6 4083.3 109.14

1 AREA (SINGLE GRID)( R1) 6.5 Dia 2510.33
DUST SUPRESSION SYSTEM -

0.6 5400 86.67
PUMP HOUSE-2(SINGLE GRID)
2 (R2) 18 9 2510.33
INTERMEDIATE STOCKPILE 0.6 27800 21.55 0.20 15.00 90.00 4.92

3 AREA(SINGLE GRID)(R3) 75 64 2510.33
0.6 4440 101.88

4 TH2A (SINGLE GRID)(R4) 12.2 10 2510.33
0.6 4200 106.64

5 TH2B(SINGLE GRID)(R5) 12 9 2510.33
0.6 4520 100.39

6 TH1(SINGLE GRID)(R6) 12 10.6 2510.33
CYCLONE AND DEWATERING
SCREEN BUILDING(SINLE 0.6 5800 81.67
7 GRID)(R7) 19 10 2510.33
1/RG1=1/R1+1/R2+1/R3+1/R4+1/R5+1/R6+1/
R7
Value of 1/RG1 0.27
Value of RG1 3.77

Ohms
---------- In -----
2pi l d

(ERT-03 & 04)

---------- In -----
2pi l d

(ERT-03 & 04)


Length in Width in resistivity (ρ) Earthing Resistance Resistance 3.5 Mtr, 40mm 3.5 Mtr, 40mm Effective
Dia GI Pipe Dia MS value of RG
meter cm 1/Rp2
PRODUCT STOCKPILE 0.6 9.34 0.26 15.00 80.00 3.84

1 AREA(SINGLE GRID)(R1) 213 118 2321.30 66200
0.6 85.13
2 TH8(SINGLE GRID)(R2) 14.1 11 2321.30 5020
0.6 65.34
3 TH9(SINGLE GRID)(R3) 19.5 15 2321.30 6900
0.6 98.61
4 TH10(SINGLE GRID)(R4) 12 9 2321.30 4200
DH1 AND DH2 (SINGLE GRID) 0.6 24.98 0.19 15.00 80.00 5.17
5 (R5) 100 7 2321.30 21400
TH11(SINGLE GRID)(R6)
6 12 9 4225.34 0.6 4200 179.50 5.02
MUTUAL WITH R5
1/RG1=1/R1+1/R2+1/R3+1/R4+1/R6
Value of 1/RG1 0.50
Value of RG1 2.01

Ohms
SHEET 22 OF 25
---------- In -----
2pi l d
3.5m Earth Pit 20m Deep Earth Pit

(i) Avg.Soil resistivity (ρ) in ohm-meter = 4225.34 W-metre 4225.34 W-metre
(ERT-05)
(ii) Length of pipe, L = 350 cm 2000 cm
(iii) Diameter of pipe, D = 4 cm 4 cm
(iv) Resistivity of one pipe electrode = 1126.10 ohm 255.70 ohm

(v) Number of Electorodes = 25.00 2 nos
(vi) Effective Resistance = 45.04 563.05184884 ohm
---------- In -----
2pi l d

(ERT-05)

(v) Number of Electorodes = 60.00
(vi) Effective Resistance = 18.77

Depth of Number of 3.5 Resistanc
Resistance
Length in resistivity (ρ) Earthing Resistance Mtr, 40mm Dia e with
S.NO Area Description Width in m burial in Ohms Rm = (RG
m in ohm- Ring in *Rp)/(RG +
GI Pipe Earth Pits
strip, (w) (RG) elctrodes (n) in Ohms
meter cm Rp)
WEIGH BRIDGE AND WEIGH MAN

1 16 9 4225.34 0.6 5000 155.47 121.83 2 121.83
ROOM (SINGLE GRID)
WEIGH BRIDGE DEEP BORE EARTH

2 1 82.52
PIT (R1)
OLCS BUILDING (JH-1) (SINGLE GRID)

3 17 14.5 4225.34 0.6 6300 128.33
(R2)
1/RG1=1/R1+1/R2+1/Rp1+1/Rp2
Paralleing of all the areas Value of
1/RG1 0.10
Value of RG1 10.48

Ohms
---------- In -----
2pi l d

(ERT-03 & 04)

---------- In -----
2pi l d
(i) Avg.Soil resistivity (ρ) in ohm-meter = 2321.30

(ERT-03 & 04)


meter cm 1/Rp2
EMERGENCY DG (SINGLE
GRID AND IT MAY BE 0.6 88.34
CLBBED WITH MPDS GRID)
1 (R1) 13 11 2321.30 4800
0.6 17.92 0.20 15.00 75.00 4.97

THICKENER(SINGLE GRID)
2 (R2) 50 Dia 2321.30 31410
COMBINED CANTEEN FOR

EMPLOYEE AND 0.6 39.32
CONTRACTOR (SINGLE
3 GRID)(R3) 47 16 2321.30 12600
0.6 74.46
4 TH7(SINGLE GRID)(R4) 17.5 12 2321.30 5900
0.6 81.39
5 TH6(SINGLE GRID)(R5) 19 7.5 2321.30 5300
1/RG1=1/R1+1/R2+1/R3+1/R4+1/R5
Value of 1/RG1 0.26
Value of RG1 3.79

Ohms
SHEET 24 OF 25
Various Equipment earthing conductor sizes

Selected Galvanised steel conductor
Thickness
(in sqmm)
S.No Equipment Remarks
(in mm)
(in mm)
Width
Area
Neutral Earthing
LV Neutral of Power Through 1Cx630sqmm cable
1 Transformer through
NGR
LV Neutral of service Through 1Cx630sqmm cable
2 Transformer
(1000kVA & above)
LV Neutral of service Through 1Cx630sqmm cable
3 Transformer (630kVA
& below)
LV Neutral of Lighting
4 25 4 100
Transformer
Enclosure Earthing
33/6.9 Power
5 75 10 750
Transformer
6 6.6 kV SPB Busduct 75 10 750
7 6.6 kV Swgr 75 10 750
8 6.6 kV Motors 50 6 300
2000kVA LT
9 75 10 750
Transformers
1600kVA and
10 65 8 520
1000kVA Transformer
11 LT Busducts 65 8 520
12 LT PCC 65 8 520
13 LT MCC 65 6 390
14 DB 50 6 300
15 DG Set 50 6 300
Battery Charger
16 50 6 300
/DCDB
17 Cable Trays 25 6 150
Structural Steel
18 25 6 150
Columns
19 Steel pipe rack 25 6 150
20 Control Panel 25 6 150
21 3 Phase Receptacles 25 6 150
22 Fence/Gate 25 6 150
23 Lighting Mast/Pole 25 4 100
24 Local Starters 8 SWG
25 Junction Boxes 8 SWG
26 Local control stations 8 SWG

SHEET 25 OF 25
Selected Galvanised steel conductor
Thickness
(in sqmm)
S.No Equipment Remarks
(in mm)
(in mm)
Width
Area
LT Motors (Rating in kW)
LT AC motors from
27 150 KW up to 200 50 6
KW
LT AC motors from
28 110 KW up to 132 40 6
KW
LT AC motors from 55
29 25 6
KW up to 90 KW
LT AC motors from 15
30 25 6
KW up to 45 KW
LT AC motors from
31 16.0 Stranded
3.75 KW up to 11 KW
LT AC motors from
32 6 Stranded
0.75 KW up to 11 KW
Main lighting
33 50 6
distribution board
MCB DB/sub-lighting
boards, lighting
transformer,
34 25 4
continuous earth bus
for highbay lighting
system
Control desk, control

post isolator and
socket outlet above
35 50 Stranded
16A upto and
stranded including
100A
Push-button station,
limit switches, switch
36 boxes, isolator and 6 Stranded
socket outlet up to
16A
Highbay lighting
37 fittings, control gear 12 SWG
and junction boxes
38 Lighting wiring system 14 SWG

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CALCULATION NO TATA PROJECTS LIMITED

1.1) Earthing Conductor Sizing

(i) Conductor material = Mild Steel MS

(ii) System Voltage = 0.415 kV

(iii) Fault Current, If = 50 kA

(iv) Fault Daration, tc = 1 sec

(v) Max. Allowable Temperature, θf = 500 0

(vi) Ambient Temperature, Ta = 50 0

(vii) Intial Temperature, θ i 40 0

(viii) Electrical resistivity of conductor

(ix) Volumetric heat capaciy of conductor

(x) Reciprocal of temperature coefficient of = 202

Substituting the input data, we get

Diameter of the earthing conductor = 28.10 mm

Allowance for corrosion considered as per specification Clause no 2.3 1.50 mm

Size of the conductor required = 30

Hence, the conductor selected = 40.00 mm dia Rod

40mm dia MS rod is been mentioned and same is considered

NOTE:Since jointing of grid conductors are by arc welding, maximum allowable

temperature considered is 500 deg.c as per IS-3043

c) Plot plan (Dwg no. TCE.6928A-04-SK-0002, Rev : R1)

Number of 3.5Mtr, No of 20 Mtr 1.5Mtr

170 Refer Group-1

200 Refer Group-2

110 Refer Group-3

160 Refer Group-5

15 295 350 Refer LCSS-1

15 295 374 Refer LCSS-2

10 20 666 Refer MPDS

20 750 300 Refer LCSS-3

a. Size of Mild steel conductor buried in ground - 40mm Dia Rod.

2 Location of earth pits will be finalised during layout drawings.

2 System fault Current, If (rms sym. g/f current) = 22 KA

3 Fault Duration, t = 1 sec

4 Avg.Soil Resistivity, r = 2266.82 W-metre

5 Grid Spacing = 2 Mtr

6 Length in X Direction = 48 Mtr

7 Length in Y Direction = 17 Mtr

8 No. of conductor along length = 24 Mtr

9 No. of conductor along breadth = 8.00 Mtr

10 Total conductor used along length in m. = 408 Mtr

11 Total conductor used along breadth in m. = 384 Mtr

12 Conductor length in the horizontal grid in m.(Lc). = 792 Mtr

13 4MtrX4 Mtr Auxiliary Grid for Four Corners = 64 Mtr

14 Total Conductor length in the horizontal grid in m.(Lc). = 856 Mtr

15 Depth of burial strip, (w) = 0.6 Mtr

Calculation of Maximum Ground Potential Rise :

Max. Ground potential above remote earth, GPR = Ig x Rg Volts

Rg= Grid Resistance = 0.90 Ohm

Ground Potential Rise, GPR = 9939.26 Volts

For deep bore ---------- In -----

(i) Length of pipe, L = 2000 cm

(ii) Diameter of pipe, D = 10 cm

(iii) Resistivity of one pipe electrode = 120.64 ohm