Ieee 80 Tiuch and Step Volt - Full Calc
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FICHTNER INDIA STANDARD CALCULATIONS DOC. NO. FOR REV. NO. SIZING OF EARTHING GRID DATE (IEEE METHOD) PAGE NO. EARTHING CALCULATIONS 1.0 INPUT DATA 1.1 Fault Current If kA = 31.5 kA 1.2 Duration of Fault current tc secs. = 3 secs. for conductor sizing 1.3 Total Fault Current consider I kA = 31.5 kA Step & Touch potential 1.4 Ratio of Soil return current to Ig / I = 0.6 Fault current (assumed) 1.5 Fault return current through Ig kA = 18.9 kA actual Earth 1.6 Duration of shock current for ts secs. = 0.5 secs. potential gradient calculations 1.7 Length of area to be earthed L M = 150 M 1.8 Breadth of area to be earthed B M = 65 M 1.9 Soil Resistivity of upper layer r1 = 50 1.10 Soil Resistivity of lower layer r2 = 50 1.11 Surface Soil Resistivity = 3000 1.12 Design ambient temperature Ta = 45 1.13 Depth of burial of conductor h M = 0.6 M 1.14 Area of Plot Ap = 9750 M Wm Wm Wm Wm rs Wm Wm 0 C 0 C M2
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Ieee 80 Tiuch and Step Volt - Full Calc
Transcript of Ieee 80 Tiuch and Step Volt - Full Calc
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FICHTNER INDIA STANDARD CALCULATIONS DOC. NO.
FOR REV. NO.
SIZING OF EARTHING GRID DATE
(IEEE METHOD) PAGE NO.
EARTHING CALCULATIONS1.0 INPUT DATA
1.1 Fault Current If kA = 31.5 kA
1.2 Duration of Fault current tc secs. = 3 secs.
for conductor sizing
1.3 Total Fault Current considered I kA = 31.5 kA
Step & Touch potential
1.4 Ratio of Soil return current to Ig / I = 0.6
Fault current (assumed)
1.5 Fault return current through Ig kA = 18.9 kA
actual Earth
1.6 Duration of shock current for ts secs. = 0.5 secs.
potential gradient calculations
1.7 Length of area to be earthed L M = 150 M
1.8 Breadth of area to be earthed B M = 65 M
1.9 Soil Resistivity of upper layer r1 = 50
1.10 Soil Resistivity of lower layer r2 = 50
1.11 Surface Soil Resistivity = 3000
1.12 Design ambient temperature Ta = 45
1.13 Depth of burial of conductor h M = 0.6 M
1.14 Area of Plot Ap = 9750 M
Wm Wm
Wm Wm
rs Wm Wm
0C 0C
M2
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2.0 CONDUCTOR SIZING2.1 Material of conductor = MS2.2 Type of conductor = ROD2.3 Type of joint = WELDING
2.4 Conductor resistivity = 15
2.5 Conductor Density SW = 7.86
2.6 Specific heat SH = 0.1142.7 Thermal co-efficient of
resistivity at temp. Tr = 0.004232.8 Reference temp. for
material constant Tr = 20
2.9 Maximum allowable temp. Tm = 620
2.10
A = If* TCAP --As per IEEE 80, eqn.33ln 1+ Tm-Ta Ko+Ta
where TCAP = 4.184*SW*SH = 3.749 --As per IEEE 80, eqn.32and Ko = = 216.407 --As per IEEE 80, page 65
Therefore, A = 658.159Considering Corrosion Allowance of 30 % --As per CBIP Tech.
Area of cross-section required is 855.606 report no. 5
Conductor Size chosen is 33.006 mm dia MS Strip
rr mW/cm3 mW/cm3
gm/cm3 gm/cm3
Cal/gm/0C Cal/gm/0C
ar
0C 0C0C 0C
Conductor cross-section, A in mm2
tc*ar*rr*104
J/cm3/0C1/ar - Tr
mm2
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FICHTNER INDIA STANDARD CALCULATIONS DOC. NO.
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Actual conductor cross-section area = 1017.88Therefore d = conductor diameter in M = 0.036 M
mm2
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3.0 TOLERABLE STEP AND TOUCH POTENTIAL
3.1 hs = 0 --depends on thickness of crushed gravel spreaded throughout the plot3.2 K -0.96721 --As per IEEE-80 page 40
3.3 Cs = 0.55 --As per Fig.-8 / page 41 of IEEE-80
3.4 = --As per IEEE 80, eqn.24 for average
human weight of 50kg
3.5 = --As per IEEE 80, eqn.26 for average
human weight of 50kgTherefore,
Volts = 1788.13 V
Volts = 570.069 V4.0 INITIAL DESIGN4.1 Length of area considered M = 150 M4.2 Breadth of area considered M = 65 M
4.3 Spacing between conductors D M = 5 MNo. of conductors on either direction
na = 31 --As per IEEE 80, page 41
nb = 14 --As per IEEE 80, page 41
4.4 Total Length of buried conductorLc M = 4115 M
4.5 Total no. of earthing pitsNp = 25 Nos.
Rod depth dr M = 3 MTherefore Rod Length Lr M = 75 M
= r-rs =
r+rs
Tol-Estep (1000+6*rs*Cs)*0.116/sqrt(ts)
Tol-Etouch (1000+1.5*rs*Cs)*0.116/sqrt(ts)
Tolerable Estep
Tolerable Etouch
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4.6 Total LengthTL=Lc+1.15Lr M = 4201.25 M -As per IEEE 80, page 114 & page 115
5.0 GRID RESISTANCE
5.1 = 0.235 W --As per IEEE 80, eqn.40
6.0 CALCULATION OF MESH AND STEP(ATTAINABLE) VOLTAGES
6.2 Es = 519.5815 V --As per IEEE 80, eqn.73
TL Tolerable 1788.1326.1 Em = 506.3446 V --As per IEEE 80, eqn.71
TL Tolerable 570.0695where,Km
= 0.375934 --As per IEEE 80, eqn.68
where,Kii for grids with ground rods / earth pits predominantly along the perimeter 1ho(reference depth of burial) = 1 M (assumed)
Spacing between conductors 'D' in M = 5 M= 20.8326667
Kh = = 1.26491106
Ks = 0.385761 --As per IEEE 80, eqn.74
Ki = 0.656+.172nx 5.988 --As per IEEE 80, eqn.69where, nx = max(na,nb)
Grid resistance Rg=r é 1 + 1 1+ 1 ë TL Ö20Ap 1+hÖ20/Ap
= r*Ig*Ks*Ki
= r*Ig*Km*Ki
=1 ( ln D 2 + (D+2h)2 - h ) + Kii ln ( 8 )) 2p 16hd 8Dd 4d Kh p(2n-1)
n = Öna*nbÖ(1+h/ho)
=1 1 + 1 + 1 (1-0.5n-2)
p 2h D+h D
(
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EARTHING CALCULATIONS1.0 INPUT DATA
1.1 Fault Current If kA = 3.18 kA
1.2 Duration of Fault current tc secs. = 0.5 secs.
for conductor sizing
1.3 Total Fault Current considered I kA = 3.18 kA
Step & Touch potential
1.4 Ratio of Soil return current to Ig / I = 0.6
Fault current (assumed)
1.5 Fault return current through Ig kA = 1.908 kA
actual Earth
1.6 Duration of shock current for ts secs. = 0.5 secs.
potential gradient calculations
1.7 Length of area to be earthed L M = 70 M
1.8 Breadth of area to be earthed B M = 70 M
1.9 Soil Resistivity of upper layer r1 = 400
1.10 Soil Resistivity of lower layer r2 = 400
1.11 Surface Soil Resistivity = 2500
1.12 Design ambient temperature Ta = 40
1.13 Depth of burial of conductor h M = 0.5 M
1.14 Area of Plot Ap = 4900 M
Wm Wm
Wm Wm
rs Wm Wm
0C 0C
M2
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2.0 CONDUCTOR SIZING2.1 Material of conductor = MS2.2 Type of conductor = ROD2.3 Type of joint = WELDING
2.4 Conductor resistivity = 15
2.5 Conductor Density SW = 7.86
2.6 Specific heat SH = 0.1142.7 Thermal co-efficient of
resistivity at temp. Tr = 0.004232.8 Reference temp. for
material constant Tr = 20
2.9 Maximum allowable temp. Tm = 620
2.10
A = If* TCAP --As per IEEE 80, eqn.33ln 1+ Tm-Ta Ko+Ta
where TCAP = 4.184*SW*SH = 3.749 --As per IEEE 80, eqn.32and Ko = = 216.407 --As per IEEE 80, page 65
Therefore, A = 26.90267Considering Corrosion Allowance of 30 % --As per CBIP Tech.
Area of cross-section required is 34.97346 report no. 5
Conductor Size chosen is 6.67305 mm dia MS Strip
rr mW/cm3 mW/cm3
gm/cm3 gm/cm3
Cal/gm/0C Cal/gm/0C
ar
0C 0C0C 0C
Conductor cross-section, A in mm2
tc*ar*rr*104
J/cm3/0C1/ar - Tr
mm2
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Actual conductor cross-section area = 34Therefore d = conductor diameter in M = 0.01 M
mm2
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3.0 TOLERABLE STEP AND TOUCH POTENTIAL
3.1 hs = 0.102 --depends on thickness of crushed gravel spreaded throughout the plot3.2 K -0.72414 --As per IEEE-80 page 40
3.3 Cs = 0.74 --As per Fig.-8 / page 41 of IEEE-80
3.4 = --As per IEEE 80, eqn.24 for average
human weight of 70kg
3.5 = --As per IEEE 80, eqn.26 for average
human weight of 70kgTherefore,
Volts = 2686.582 V
Volts = 838.169 V4.0 INITIAL DESIGN4.1 Length of area considered M = 70 M4.2 Breadth of area considered M = 70 M
4.3 Spacing between conductors D M = 7 MNo. of conductors on either direction
na = 11 --As per IEEE 80, page 41
nb = 11 --As per IEEE 80, page 41
4.4 Total Length of buried conductorLc M = 1540 M
4.5 Total no. of earthing pitsNp = 0 Nos.
Rod depth dr M = 3 MTherefore Rod Length Lr M = 0 M
= r-rs =
r+rs
Tol-Estep (1000+6*rs*Cs)*0.157/sqrt(ts)
Tol-Etouch (1000+1.5*rs*Cs)*0.157/sqrt(ts)
Tolerable Estep
Tolerable Etouch
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4.6 Total LengthTL=Lc+Lr M = 1540 M -As per IEEE 80, page 114 & page 115
5.0 GRID RESISTANCE
5.1 = 2.776 W --As per IEEE 80, eqn.40
Ground Potential Rise 5296.02351 Volt
6.0 CALCULATION OF MESH AND STEP(ATTAINABLE) VOLTAGES
6.2 Es Actual = 457.29519 V --As per IEEE 80, eqn.73
TL Tolerable 2686.58156.1 Em Actual = 1001.6143 V --As per IEEE 80, eqn.71
TL Tolerable 838.16902 NOT OK, NEED TO ADD RODS AROUD PERIPHERYwhere, SEE NEXT SHEETKm
= 0.88955859 --As per IEEE 80, eqn.68
where,Kii for grids with ground rods / earth pits predominantly along the perimeter 0.5700634 Without Ground Rods, Kii is not 1, use formula
ho(reference depth of burial) = 1 M (assumed)
Spacing between conductors 'D' in M = 7 M= 11
Kh = = 1.22474487
Ks = 0.40613523 --As per IEEE 80, eqn.74
Grid resistance Rg=r é 1 + 1 1+ 1 ë TL Ö20Ap 1+hÖ20/Ap
= r*Ig*Ks*Ki
= r*Ig*Km*Ki
=1 ( ln D 2 + (D+2h)2 - h ) + Kii ln ( 8 )) 2p 16hd 8Dd 4d Kh p(2n-1)
n = Öna*nbÖ(1+h/ho)
=1 1 + 1 + 1 (1-0.5n-2)
p 2h D+h D
(
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Ki = 0.644+.148n 2.272 --As per IEEE 80, eqn.69
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EARTHING CALCULATIONS1.0 INPUT DATA
1.1 Fault Current If kA = 3.18 kA
1.2 Duration of Fault current tc secs. = 0.5 secs.
for conductor sizing
1.3 Total Fault Current considered I kA = 3.18 kA
Step & Touch potential
1.4 Ratio of Soil return current to Ig / I = 0.6
Fault current (assumed)
1.5 Fault return current through Ig kA = 1.908 kA
actual Earth
1.6 Duration of shock current for ts secs. = 0.5 secs.
potential gradient calculations
1.7 Length of area to be earthed L M = 70 M
1.8 Breadth of area to be earthed B M = 70 M
1.9 Soil Resistivity of upper layer r1 = 400
1.10 Soil Resistivity of lower layer r2 = 400
1.11 Surface Soil Resistivity = 2500
1.12 Design ambient temperature Ta = 40
1.13 Depth of burial of conductor h M = 0.5 M
1.14 Area of Plot Ap = 4900 M
Wm Wm
Wm Wm
rs Wm Wm
0C 0C
M2
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2.0 CONDUCTOR SIZING2.1 Material of conductor = MS2.2 Type of conductor = ROD2.3 Type of joint = WELDING
2.4 Conductor resistivity = 15
2.5 Conductor Density SW = 7.86
2.6 Specific heat SH = 0.1142.7 Thermal co-efficient of
resistivity at temp. Tr = 0.004232.8 Reference temp. for
material constant Tr = 20
2.9 Maximum allowable temp. Tm = 620
2.10
A = If* TCAP --As per IEEE 80, eqn.33ln 1+ Tm-Ta Ko+Ta
where TCAP = 4.184*SW*SH = 3.749 --As per IEEE 80, eqn.32and Ko = = 216.407 --As per IEEE 80, page 65
Therefore, A = 26.90267Considering Corrosion Allowance of 30 % --As per CBIP Tech.
Area of cross-section required is 34.97346 report no. 5
Conductor Size chosen is 6.67305 mm dia MS Strip
rr mW/cm3 mW/cm3
gm/cm3 gm/cm3
Cal/gm/0C Cal/gm/0C
ar
0C 0C0C 0C
Conductor cross-section, A in mm2
tc*ar*rr*104
J/cm3/0C1/ar - Tr
mm2
18 of 22 .
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Actual conductor cross-section area = 34Therefore d = conductor diameter in M = 0.01 M
mm2
19 of 22 .
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3.0 TOLERABLE STEP AND TOUCH POTENTIAL
3.1 hs = 0.102 --depends on thickness of crushed gravel spreaded throughout the plot3.2 K -0.72414 --As per IEEE-80 page 40
3.3 Cs = 0.74 --As per Fig.-8 / page 41 of IEEE-80
3.4 = --As per IEEE 80, eqn.24 for average
human weight of 70kg
3.5 = --As per IEEE 80, eqn.26 for average
human weight of 70kgTherefore,
Volts = 2686.582 V
Volts = 838.169 V4.0 INITIAL DESIGN4.1 Length of area considered M = 70 M4.2 Breadth of area considered M = 70 M
4.3 Spacing between conductors D M = 7 MNo. of conductors on either direction
na = 11 --As per IEEE 80, page 41
nb = 11 --As per IEEE 80, page 41
4.4 Total Length of buried conductorLc M = 1540 M
4.5 Total no. of earthing pits Lp 280 MNp = 20 Nos.
Rod depth dr M = 7.5 MTherefore Rod Length Lr M = 150 M
= r-rs =
r+rs
Tol-Estep (1000+6*rs*Cs)*0.157/sqrt(ts)
Tol-Etouch (1000+1.5*rs*Cs)*0.157/sqrt(ts)
Tolerable Estep
Tolerable Etouch
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4.6 Total LengthTL=Lc+Lr M = 1690 M -As per IEEE 80, page 114 & page 115
5.0 GRID RESISTANCE
5.1 = 2.753 W --As per IEEE 80, eqn.40
Ground Potential Rise 5252.03673 Volt
6.0 CALCULATION OF MESH AND STEP(ATTAINABLE) VOLTAGES
6.2 Es Actual = 549.11079 V --As per IEEE 80, eqn.73
TL Tolerable 2686.58156.1 Em Actual = 749.05861 V --As per IEEE 80, eqn.71
TL Tolerable 838.16902where, 1786.36434367398 0.41932Km
= 0.77168339 --As per IEEE 80, eqn.68
where,Kii for grids with ground rods / earth pits predominantly along the perimeter 1 Without Rods, Kii is set to unity = 1
ho(reference depth of burial) = 1 M (assumed)
Spacing between conductors 'D' in M = 7 M= 11
Kh = = 1.22474487
Ks = 0.40613523 --As per IEEE 80, eqn.74
Grid resistance Rg=r é 1 + 1 1+ 1 ë TL Ö20Ap 1+hÖ20/Ap
= r*Ig*Ks*Ki
= r*Ig*Km*Ki
=1 ( ln D 2 + (D+2h)2 - h ) + Kii ln ( 8 )) 2p 16hd 8Dd 4d Kh p(2n-1)
n = Öna*nbÖ(1+h/ho)
=1 1 + 1 + 1 (1-0.5n-2)
p 2h D+h D
(
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Ki = 0.644+.148n 2.272 --As per IEEE 80, eqn.69
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Schwarz's Formula
Rg = R1*R2 - R12 -0.102282 WR1 + R2 - 2*R12
where,
R1 = 0.198113 W
R2 = 0.695697 W
R12 = 0.190316 W
Soil Resistivity 5050
---- for rods penetrating 50 to 2 layers---- for rods and grid conductors 50 in the same layer---- for uniform soil
5050
where, H is the upper layer thickness 2 m
Total Length of buried conductor 4115 m
L = Length of plot plan 150 m
B = Breadth of plot plan 65 mh' = sqrt(d1*h) or [0.5*d1 if h = 0] 0.146969
where,
h = Depth of burial of conductor 0.6 m
d1 = dia of the grid conductors in m 0.036 m
A = Area of Plot 9750 m²
0.006076K1 = -0.04*L / W + 1.41 ---- for h = 0 1.084615
-0.05*L / W + 1.2-0.05*L / W + 1.13
K2 = 0.15*L / W + 5.5 ---- for h = 0 4.9107690.10*L / W + 4.68-0.05*L / W + 4.4
n = no. of ground rods 25
dr = Rod depth 3 m
d2 = dia of the ground rods in m 0.036 m
[r/(p*LC)]*[ln(2*LC/h') + K1*(LC/ÖA) - K2]
[ra/(2*n*p*dr)]*[ln(8*dr/d2) - 1 + 2*K1*(dr/ÖA)*(Ön - 1)²]
[ra/(p*LC)]*[ln(2*LC/dr) + K1*(LC/ÖA) - K2 + 1]
r = W-mra = Apparent soil resistivity as seen by a ground rod in W-m W-m
dr*(r1*r2) / [r2*H + r1(dr - H)] W-m
dr*(r1*r2) / [r2*(H-h) + r1(dr + h - H)] W-m
r1 = r2 r1 = W-mr2 = W-m
LC =
h/ÖA =
---- for h / ÖA = 0.1---- for h / ÖA = 0.16667
---- for h / ÖA = 0.1---- for h / ÖA = 0.16667
