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Step & Touch Voltage Calculation For Tunnel Ieee-80-2000

STEP & TOUCH VOLTAGE CALCULATION FOR A TUNNEL WITH UNDERGROUND SUBSTATION . THE TUNNEL IS EARTHED AT EVERY 45 METER USING 1C 150 Sq mm LEAD SHEATHED CABLES

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Apsi Lal
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735 views5 pages

Step & Touch Voltage Calculation For Tunnel Ieee-80-2000

STEP & TOUCH VOLTAGE CALCULATION FOR A TUNNEL WITH UNDERGROUND SUBSTATION . THE TUNNEL IS EARTHED AT EVERY 45 METER USING 1C 150 Sq mm LEAD SHEATHED CABLES

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Apsi Lal
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© © All Rights Reserved
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Download as PDF, TXT or read online on Scribd
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Document number

CONTRACTOR : SAMSUNG C&T CLIENT QATARI DIAR


Revision NO
Date of Issue
1. INPUT DATA
SYSTEM VOLTAGE = 0.415 kV
SYSTEM GROUNDING = NEUTRAL
GRID CURRENT Ig = 44 kA
Duration of Shock Current ts = 1 Second
CALCULATION FOR MAXIMUM PERMISSIIBLE TOUCH AND STEP VOLTAGE
LUSAIL DEVELOPMENT PRIMARY INFRASTRUCTURE CP5B UTILITY TUNNEL ALONG ROAD A2
08-Jan-2013
Area of Substation Grid A = 24,363.72 Sq. Metre
Conductor Size for Main Grid d = 150 Sq. mm
Depth of Burial W.R.T Ground level h = 7.5 Metre
Length of burried Conductor L = 4,780.53 Metre
( Periphery conductor + Grid conductors)
Total Ground Rod Length Lr = 159 Metre
Soil Resistivity = 101.53 Ohm-Metre
Resistity if Concrete s = 5,000.00 Ohm-Metre
Spacing for Earth Mat for Basement D = 15 Metre
Thickness of Basement Slab hs = 2.5 Metre Thickness of Basement Slab hs = 2.5 Metre
Weighing Term Kii = 1
No of Conductors along the Length of Tunnel na = 206 Nos
No of Conductors along the width of Tunnel nb = 2 Nos
Calculation of Tolerable Etouch & E step voltage
The MaximumAllowable Toucgh Voltage
From Eq .33 of IEEE 80-2000 for a person with 70 Kg body Weight]
Where Cs =Reduction factor for derating nominal value or surface layer resistivity
| |
ts
s Cs Etouch
157 . 0
5 . 1 1000 + =
Where Cs =Reduction factor for derating nominal value or surface layer resistivity
As given in IEEE 80-2000 Eqn No 27
09 . 0 2
1 09 . 0
1
+
|
|
.
|

\
|

=
hs
s
Cs

Document number
CONTRACTOR : SAMSUNG C&T CLIENT QATARI DIAR
LUSAIL DEVELOPMENT PRIMARY INFRASTRUCTURE CP5B UTILITY TUNNEL ALONG ROAD A2
Substituting
Cs= 0.09 X(1- (101.53/ 5000))
( 2 x 2.5 +0.09)
Cs= 0.983
Substituting the above values
Tolerable E touch at basement = 0.157
1
= 1314.4825 volts
Tolerable E touch at basement = 1314.483 Volts
[1000+1.5x 0.983x 5000 ] x
1-
Tolerable E touch at basement = 1314.483 Volts
Tolerable E step
From Eq 30 of IEEE 80-2000, Step voltage for a person with a body weight of 70 Kg is given by
Substituting the derived Values
Tolerable E step
=
1
Tolerable E step at Basement 4786.93 Volts
[1000+6x 0.983x 5000 ] x 0.157 ]
| |
ts
I s k hs Cs EStep
157 . 0
) ( 6 1000 + + =
Document number
CONTRACTOR : SAMSUNG C&T CLIENT QATARI DIAR
LUSAIL DEVELOPMENT PRIMARY INFRASTRUCTURE CP5B UTILITY TUNNEL ALONG ROAD A2
3. Calculation of GroundingResistance/Grid Resistnace
As per Eq 40 of IEEE 80-86 for Grid Depths between 0.25 M & 2.5 M
is the soil resistivity
Lt is is the total length of the buried conductor
A is the total area occupied by the earthing grid
CALCULATION OF MAXIMUM ATTAINABLE TOUCH AND STEP VOLTAGE
(Refer Definitions for Detail)
(
(
(

|
|
|
.
|

\
|
+
+ + =
A
h
A Lt
Rg
20
1
1
1
20
1 1

Substituting the Values


Rg = 0.306 Ohms
4. Calculation of MaximumGround Potential Rise
Maximum ground potential above remote earth GPR = Ig x Rg Volts
Where Ig =Grid Current
therefore Ig = 44 kA
substituting the Values
Ground potential Rise GPR = 13469.49 Volts
Now the GPR is Greater than the tolerable touch voltage
5. Calculation of E Mesh Voltage
As per the IEEE 80-2000 Eqn no 80
(Refer Definitions for Detail)
Ig Ki Km
where
Km, the spacing factor of Mesh Voltage
As per the IEEE 80-2000 Eqn no 80
Where D is the spacing between the parellal Grid Conductors
h is the depth of the buried conductors
Kh is the weighting factor of depth of burial.
Kh = 2.915475947
No of Parellal Paths(n) = na x nb x nc x nd
Lr Le
Ig Ki Km
Emesh
15 . 1 +

=

h Kh + = 1 (
( )
(

+
(

+
+

=
[ [ 1 2
8
ln
4 8
) 2 (
16
ln
2
1
2 2
n Kh
Kii
d
h
d D
h D
d h
D
Km
Where
p
c
L
L
na
2
=
A
L
n
p
b
4
2
=
Document number
CONTRACTOR : SAMSUNG C&T CLIENT QATARI DIAR
LUSAIL DEVELOPMENT PRIMARY INFRASTRUCTURE CP5B UTILITY TUNNEL ALONG ROAD A2
Lc is total length of horrizontal Grid conductors in Mtr = 5247+270+1283 Mtr
(Incudes Tunnel Main Grid +Horrizontal connections) = 6800 Mtr
Lp is the length of Grid conductors on the perimeter in Mtr = 5103 Mtr
substituting the Values
na = 2.67
nb = 0.32
nc=nd=1( see Note Below)
n = 2.67 x 0.32 x 1 x 1
n = 0.86
The irregularity factor Ki( Eqn 89 IEEE80-2000) = 0.644+(0.148 x n)
=
= 0.771644184
Note : Considering the tunnel as Rectangular shape neglecting the Access Chambers, Susbtation & Ventillation Chamber.
However the conductors within these structures are considered.
0.644+( 0.148 x 0.86)
The average spacing between the Grid conductors D
Wg & Lg is the width and length of the grid conductors
nr & nc are the no of rows and columns respectively
nc = 82
nr = 2
Substituting these values D = 132.5
So Assigning the Values in the Equation for Km Km = 0.447
The effective Burried Length Lm =
Lm = 11461.727
Substituting the above values in the equation, the maximum attainable
|
.
|

\
|

=
1 1 2
1
c
g
r
g
n
L
n
W
D
R L
Ly Lx
Lr
Lc Lm
(
(

|
|
.
|

\
|
+
+ + =
2 2
22 . 1 55 . 1
5. Calculation of attainable E Step
The Geometric spacing factor Ks is given by
Since the Maximum Attained voltage is less than the permissible voltage Calculated the system is considered SAFE
Substituting the above values in the equation, the maximum attainable
Touch Voltage is
= 134.44 volts
Lr Lc
Ig ki ks
Estep
15 . 1 +

=

( )
(

+
+
+
[
=
2
5 . 0 1
1 1
2
1 1
n
D h D h
Ks
Document number
CONTRACTOR : SAMSUNG C&T CLIENT QATARI DIAR
LUSAIL DEVELOPMENT PRIMARY INFRASTRUCTURE CP5B UTILITY TUNNEL ALONG ROAD A2
Substituting the values on the above equation, Ks = 0.026
The Effective burried Length Ls = 0.75L
c
+0.85L
r
= 5259 Meter
Finally the maximumallowable Step voltage Es is = 17.043 Volt
Since the Maximum Attained voltage is less than the permissible voltage Calculated the system is considered SAFE

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