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CONTRACTOR : SAMSUNG C&T CLIENT QATARI DIAR

Revision NODate 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 ρ = 101.53 Ohm -Metre

Resistity if Concrete ρs = 5,000.00 Ohm -Metre

Spacing for Earth Mat for Basement D = 15 Metre

Thickness of Basement Slab hs = 2.5 MetreThickness 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 Maximum Allowable 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

sCsEtouch 157.05.11000

Where Cs = Reduction factor for derating nominal value or surface layer resistivityAs given in IEEE 80-2000 Eqn No 27

09.02

109.01

hs

sCs

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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 stepFrom 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

IskhsCsEStep 157.0)(61000

Document number

CONTRACTOR : SAMSUNG C&T CLIENT QATARI DIAR

LUSAIL DEVELOPMENT PRIMARY INFRASTRUCTURE CP5B UTILITY TUNNEL ALONG ROAD A2

3. Calculation of Grounding Resistance/Grid ResistnaceAs per Eq 40 of IEEE 80-86 for Grid Depths between 0.25 M & 2.5 M

ρ is the soil resistivityLt is is the total length of the buried conductorA is the total area occupied by the earthing grid

CALCULATION OF MAXIMUM ATTAINABLE TOUCH AND STEP VOLTAGE

(Refer Definitions for Detail)

AhALtRg

201

112011

Substituting the ValuesRg = 0.306 Ohms

4. Calculation of Maximum Ground 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 VoltageAs per the IEEE 80-2000 Eqn no 80

(Refer Definitions for Detail)

IgKiKm

whereKm, the spacing factor of Mesh VoltageAs per the IEEE 80-2000 Eqn no 80

Where D is the spacing between the parellal Grid Conductorsh 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

LrLeIgKiKmEmesh

15.1

hKh 1(

12

8ln48

)2(16

ln21 22

nKhKii

dh

dDhD

dhDKm

Where p

c

LLna 2

A

Ln pb

42

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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 Mtrsubstituting the Values

na = 2.67nb = 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 conductorsnr & nc are the no of rows and columns respectively

nc = 82nr = 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

1121

c

g

r

g

nL

nWD

RLLyLx

LrLcLm

2222.155.1

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

LrLcIgkiksEstep

15.1

25.0111

211 n

DhDhKs

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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 = 0.75Lc+0.85Lr

= 5259 Meter

Finally the maximum allowable Step voltage Es is = 17.043 Volt

Since the Maximum Attained voltage is less than the permissible voltage Calculated the system is considered SAFE