EARTHING STRIP SCHEDULE
TOTAL
EARTHING
SNO. FROM TO LENGTH Ohm
SIZE
(METERS)
1 STRUCTURE DC EARTH PIT 1 25 X 3 0 0.00
2 STRUCTURE DC EARTH PIT 2 25 X 3 0 0.00
3 STRUCTURE DC EARTH PIT 3 25 X 3 0 0.00
4 STRUCTURE DC EARTH PIT 4 25 X 3 0 0.00
5 INVERTER & ACDB AC EARTH PIT 1 25 X 6 0 0.00
6 ISOLATOR & METERING AC EARTH PIT 2 50 X 6 0 0.00
7 INVERTER & ACDB AC EARTH PIT 1 50 X 6 0 0.00
8 ISOLATOR & METERING AC EARTH PIT 2 50 X 6 0 0.00
9 LIGHTING ARRESTOR LA EARTH PIT 1 50 X 6 0 0.00
10 LIGHTING ARRESTOR LA EARTH PIT 2 50 X 6 0 0.00
Resistance of Earth electrode as per BS:7430-1998
Considering Maintenance free Earth Pit with bore dia 17.2 mm and 3mtr long
where,
rc = Resistivity of the infill material in ohm-m = 5.80 ohm-m [As per Indelec catalogue]
Bore dia-50mm- Rod dia
0.0328
D = Diameter of the infill material in m = m 17.2mm = 32.8mm
l = Length of the rod or pipe in m = 3 m
d= Diameter of the rod in m 0.0172 m [As per Indelec catalogue]
(As per Soil test report
r= Resistivity of the soil in ( ohm-m) =
100.00 ohm-m and for Average refer
Resistvity detail)
R= 29.8982 ohms
Total electrodes considered = 6 Nos.
Effective resistance of earth electrode (Re) = R / No of Electrodes 4.983
EARTH STRIP CALCULATION
Earth strip as per IS: 3043
(Qc (B + 20) ) θt-θ1
K= √( δ20 ) ln (1+ B + θ1 )
where,
Qc = volumetric heat capacity of conductor material ( j / degC mm3),
B= reciprocal of temperature coefficient of resistivity at 0degC for the conductor (degC),
δ20 = electrical resistivity of conductor material at 20degC (ohm-mm)
θ1 = initial temperature of conductor = 50 degC
θt = final temperature of Steel conductor = 500 degC
θt = final temperature of Aluminium conductor = 325 degC
θt = final temperature of Copper conductor = 395 degC
Material constants as per IS-3043-1987 Table-5
Steel Aluminium Copper
B 202 228 234.5
Qc 0.0038 0.0025 0.00345
δ20 0.000138 2.826E-05 1.724E-05
For GI Strip
K= √( ( 0.0038 (202 + 20) ) ) ln ( 1 + 500-50 )
0.000138 202 + 50
K= 79.14
DC SIDE SOLAR AREA
No. Of Parallel Strings at Inverter 10 Nos. REF. SINGLE LINE DIAGRAM
Short Circuit Current Per String 18.47 A REF. MODULE DATASHEET
Total Fault Current at Inverters (If) 184.7 A
Safety Margin (25 %) 230.88 A
288.59 A
Corrission Effect (1 % Every Year and calculate for 25 years)
Area of Cross Section (A) = Fault Current (If) X Fault Current Time √(t)/ Material Constant (K)
A= Cross sectional Area of Conductor 6.32 Sq. Mm
If = Fault Current 289 Amp
t= Fault Current time 3 sec
K= Material Constant 79.14
Earthing Cable for Solar Inverter 6.00 Sq. Mm
AC SIDE - INVERTERS, ACDB & ISOLATOR BOX
No. Of Inverters 4 Nos. REF. SINGLE LINE DIAGRAM
Short Circuit Current of Inverter 167.1 A REF. INVERTER DATASHEET
Total Short Circuit Current of Inverter 668.4 A
No. Of ACDB/ISOLATOR 1 Nos.
Short Circuit Current of ACDB 160 A
Total Short Circuit Current of Inverter 160 A
kA Rating of ACDB/Isolator (If) 25 kA REF. MCCB DATASHEET
Area of Cross Section (A) = Fault Current (If) X Fault Current Time √(t)/ Material Constant (K)
A= Cross sectional Area of Conductor 315.90 Sq. Mm
If = Fault Current 25000 Amp
t= Fault Current time 1 sec
K= Material Constant 79.14
Earth Strip Size Required 50 X 6 Sq. Mm.
DC EARTHING
Resistance of Earth strip as per IS: 3043
100 Meters length of earth strip of size 6 & 25X3 mm GI is burried in the plant at 100 mm depth.
Rs = 100 r loge 4Lohms
2p l w
where,
r= resistivity of the soil in ( ohm-m) = 100.00 ohm-m
l= length of the strip in cm = 10000 cm [As per Layout]
w= width of the strip in cm = 2.5 cm
Rs1= 1.54 ohms Effective 1.18
Resistance(Re)
AC EARTHING
Resistance of Earth strip as per IS: 3043
65 Meters length of earth strip of size 50 X 6 mm GI is burried in the plant at 100 mm depth.
Rs = 100 r loge 4Lohms
2p l w
where,
r= resistivity of the soil in ( ohm-m) = 100.00 ohm-m
l= length of the strip in cm = 6500 cm [As per Layout]
w= width of the strip in cm = 5 cm
Effective
Rs2 = 2.10 ohms Resistance(Re) 1.48
LA EARTHING
Resistance of Earth strip as per IS: 3043
40 Meters length of earth strip of size 50 X 6 mm GI is burried in the plant at 100 mm depth.
Rs = 100 r loge 4Lohms
2p l w
where,
r= resistivity of the soil in ( ohm-m) = 100.00 ohm-m
l= length of the strip in cm = 4000 cm [As per Layout]
w= width of the strip in cm = 5 cm
Effective
Rs3 = 3.21 ohms Resistance(Re) 1.95
mtr long
per Indelec catalogue]
re dia-50mm- Rod dia
2mm = 32.8mm
per Indelec catalogue]
s per Soil test report
d for Average refer
sistvity detail)
ohms
NE DIAGRAM
DATASHEET
stant (K)
NE DIAGRAM
DATASHEET
TASHEET
l Constant (K)
s per Layout]
ohms
s per Layout]
ohms
s per Layout]
ohms
