EARTHING CALCULATION FOR TOUCH AND STEP VOLTAGEFull description
CalculationFull description
Str calculation
Full description
Earthing TrafoFull description
Advanced earthing design calculation for solar PV area and substation areas
frp tankFull description
design
Prerequisites TECHNICAL DATA SYMBOL
DESCRIPTION
i2t Tm
Energy of max earth fault
Ta
Ambient Temperature
αr
Thermal coefficient of resistivity
ρr
Resistivity of earthing conductor
Max allowable fusing temperature
K0 TCAP
Thermal capacity of conductor per unit volume Soil resistivity Resistivity of the surface layer material Thickness of the surface layer Maximum fault clearing time Total length of buried conductors Depth of the earthing grid Earth fault current
Sf
Current division factor X/R ratio at the fault location
f
System frequency Duration of the fault Total length of horizontal grid conductors Length of grid conductors on the perimeter Total length of earthing electrodes / rods Length of each earthing electrode / rod
A'
Total area of the grid Maximum length of the grids in the x directions Maximum length of the grids in the y directions Maximum distance between any two points on the grid Spacing between parallel grid conductors Cross-sectional diameter of a grid conductor
A is the minimum cross-sectional area of the earthing grid conductor (mm2)
A = 16.630826229 Cs is the surface layer derating factor
Cs= 0.9990025
is the touch voltage limit (V) is the step voltage limit (V)
Rg is the earthing grid resistance with respect to remote earth (Ω) Rg = 0.0004898663
Ig is Symmetrical grid current Ig = 20
IG is the maximum grid current IG= 1.7247463558
GPR is the maximum ground potential rise GPR= 0.0008448952
ECHNICAL DATA
CRIPTION
VALUE
UNIT
3
A2s
9
°C
5
°C
tivity
0.006
°C-1
ductor
2
μΩ. cm
ature
146.666667
ctor per unit volume
terial
tors
5 0.003 2 45
Jcm-3°C-1
Ω.m Ω.m m
45
s
10
m
5
m
20
A
1 3 50
Hz
3
s
10
m
the perimeter
5
m
odes / rods
3
m
rode / rod
2
m
25
m2
in the x directions
5
m
in the y directions
6
m
any two points on the grid
4
m
d conductors
7
m
2
m
d conductors
grid conductor
area of the earthing grid conductor (mm2)
pect to remote earth (Ω)
x= 0.02603184
TA is the dc time offset constant
TA= 235.61945 Df is the decrement factor Df = 2.97474999
n is Geometric Factor
na= 4 nb=1, for square grids nc=1 , for square and rectangular grids
nd=1, for square, rectangular and L-shaped grids
NOW for square grids for square and rectangular grids for square, rectangular and L-shaped grids
n= n= n=
2.278474253 1.024295039 2.224431599
Ki is Irregularity factor Ki= 0.8126071
for
Kii is a weighting factor for earth electrodes /rods on the corner mesh Kii=1 for grids with earth electrodes along the grid perimeter or corners Kii = 0.4642175
Kh is a weighting factor for depth of burial Kh = 2.4494897
Km is the geometric spacing factor Km= 0.1506657 Lm is the effective buried length ,for grids with few or no earthing electrodes (and none on corners or along the perimeter) Lm= 13
Em is the mesh voltage Em= 0.0324868
Ks is the geometric spacing factor Ks= 0.0212511
Ls is the effective buried length Ls= 10.05
Es is the maximum allowable step voltage Es= 0.0059272
RESULT
50 kg:
EARTHING GRID DESIGN IS SAFE
RESULT
70 kg:
EARTHING GRID DESIGN IS SAFE
otherwise
nb= 0.5
otherwise
nc= 1.1122158
otherwise
nd= 0.5121475
otherwise
n= 1.1392371
the corner mesh
r or corners
ng electrodes
OR
Lm is the effective buried length , for grids with earthing electrodes on the corners and along the perimeter Lm= 15.58723
