LVSG01 earthing conductors Calculations
1) Calculation of Earthing Conductor Size - BS 7430:2011+A1:2015
S: cross section area of the main earthing conductor (mm2) 240.00 225.34
I: fault current (ampere) 28000
t: duration of fault current (seconds) 1.00
k: material coefficient of copper earth conductor (A.sqrt(sec.)/mm2) 124.25
Where:
k= α * SQRT { LOGe ( ( T2+β ) / (T1+β) ) }
T2: maximum permitted final temperature of the conductor ( c ) 160.00
T1: ambient temperature of the conductor ( c ) 52.00
generator (0.4kv) neutral and earthing conductors Calculations
1) Calculation of Earthing Conductor Size - BS 7430:2011+A1:2015
S: cross section area of the main earthing conductor (mm2) 185.00 169.01
I: fault current (ampere) 21000
t: duration of fault current (seconds) 1.00
k: material coefficient of copper earth conductor (A.sqrt(sec.)/mm2) 124.25
Where:
k= α * SQRT { LOGe ( ( T2+β ) / (T1+β) ) }
T2: maximum permitted final temperature of the conductor ( c ) 160.00
T1: ambient temperature of the conductor ( c ) 52.00
transformer (4.16/0.4kv) neutral and earthing conductors Calculations
1) Calculation of Earthing Conductor Size - BS 7430:2011+A1:2015
S: cross section area of the main earthing conductor (mm2) 300.00 241.44
I: fault current (ampere) 30000
t: duration of fault current (seconds) 1.00
k: material coefficient of copper earth conductor (A.sqrt(sec.)/mm2) 124.25
Where:
k= α * SQRT { LOGe ( ( T2+β ) / (T1+β) ) }
T2: maximum permitted final temperature of the conductor ( c ) 160.00
T1: ambient temperature of the conductor ( c ) 52.00
transformer (33/4.16kv) earthing conductors Calculations
1) Calculation of Earthing Conductor Size - BS 7430:2011+A1:2015
S: cross section area of the main earthing conductor (mm2) 240.00 201.20
I: fault current (ampere) 25000
t: duration of fault current (seconds) 1.00
k: material coefficient of copper earth conductor (A.sqrt(sec.)/mm2) 124.25
Where:
k= α * SQRT { LOGe ( ( T2+β ) / (T1+β) ) }
T2: maximum permitted final temperature of the conductor ( c ) 160.00
T1: ambient temperature of the conductor ( c ) 52.00
MV earthing conductors Calculations at 4.16KV MV switchgear room
1) Calculation of Earthing Conductor Size - BS 7430:2011+A1:2015
S: cross section area of the main earthing conductor (mm2) 120.00 96.58
I: fault current (ampere) 12000
t: duration of fault current (seconds) 1.00
k: material coefficient of copper earth conductor (A.sqrt(sec.)/mm2) 124.25
Where:
k= α * SQRT { LOGe ( ( T2+β ) / (T1+β) ) }
T2: maximum permitted final temperature of the conductor ( c ) 160.00
T1: ambient temperature of the conductor ( c ) 52.00
MV earthing conductors Calculations at 33KV MV switchgear room
1) Calculation of Earthing Conductor Size - BS 7430:2011+A1:2015
S: cross section area of the main earthing conductor (mm2) 240.00 201.20
I: fault current (ampere) 25000
t: duration of fault current (seconds) 1.00
k: material coefficient of copper earth conductor (A.sqrt(sec.)/mm2) 124.25
Where:
k= α * SQRT { LOGe ( ( T2+β ) / (T1+β) ) }
T2: maximum permitted final temperature of the conductor ( c ) 160.00
T1: ambient temperature of the conductor ( c ) 52.00
Earthing resistance Calculations for the BOOSTER PUMP ROOM (SM807)
1) Calculation of Single Earthing Rod Resistance - BS 7430:2011+A1:2015
Note: Conductor Size Assumed to be 70 mm2
Rr: Single Earthing Rod Resistance (ohm) 62.26
26
ρ: Soil Resistivity (ohm.meter) 200.00
L: Length of Earthing Rod (meter) 3.00
d: Diameter of Earthing Rod (meter) 0.025
2) Calculation of grid mesh Resistance Rm - BS 7430:2011+A1:2015
Rm: Mesh resistance (ohm) 11.42
ρ: Soil Resistivity (ohm.meter) 200.00
L: total length of strip used in the mesh, in metres (m). 71.00
A: the actual area covered by the mesh, in square metres (m2) 106.00
3) Calculation of Round Conductor Resistance - BS 7430:2011+A1:2015
Rta: Resistance of Strip or Round Conductor (ohm) 6.65
ρ: Soil Resistivity (ohm.meter) 200.00
L: Length of Earthing Strip or Round Conductor (meter) 60.00
h: Depth of Earthing Strip or Round Conductor (meter) 0.50
d: Width of Earthing Strip or Round Conductor (meter) 0.0140
k: The value is 1.36 for strip, or 1.85 for round conductor 1.85
1/𝑅𝑔=" " 8𝑥1/𝑅𝑟 "
4) Calculation of total earthing of the building (Rg)
+" 1/𝑅𝑚 + 1/𝑅𝑡𝑎 =
0.128 + 0.088 + 0.15 = 0.37
𝑅 = 2.73 ohm
