6.6kv Cable Calculation (Cc)

Reference : Unistar High Voltage XLPE Cables - Catalogue Formula Used : KVA Full load current = KV x

3

Short circuit current  A = Ish x

t k

Where t = short circuit time in sec k = constant

Voltage Drop VDROP =

3 * IFL * (R COS f + X SIN f) * L KV * 1000 * N.R

%

Where IFL = Full load current of the Load connected in Amps KVA = Rating of the Load connected KV = System Voltage R = Resistance of the cable in Ohm/Ph/KM X = Reactance of the cable in Ohm/Ph/KM L = Length of the cable in meters N.R = No of Runs of the cable cosf = Power factor of the system Voltage Dip VDIP =

3 * IST * (R COS f + X SIN f) * L KV * 1000 * N.R

%

Where IST = Starting current of the Motor in Amps KVA = Rating of the Load connected KV = System Voltage R = Resistance of the cable in Ohm/Ph/KM X = Reactance of the cable in Ohm/Ph/KM L = Length of the cable in meters N.R = No of Runs of the cable cosf = Starting Power factor of the system Derating Factor  o  Ambient temperatu temperature re correction correction factor for 50 C = Group derating factor  Multi Core cables For 3 circuits, derating factor run in air= 0.92 Therefore the Total derating factor = 0.83x 0.92= 0.7636

0.83

1.1Primary Air (PA) fans Load = KV =

2700 kW 11 2700

Full load current =

=

165.75

=

165.75 0.76

=

217.1

A

3 x 11 x 0.9 x 0.95 Total derating Factor

=

0.76

Current to be carried by the cable

Short circuit current =  A =

40

40 x

0.16 94

A

kA x

1000

= 170.21

331

A

2

mm

Considering 3C x185 cable 3C x 185 XLPE cable can carry Voltage drop 3 x

165.75

=

x(

11000 0.121

0.211 x

x

0.9 + 0.0968 x 0.435 ) x 0.2 x 100

1

Voltage dip Starting Current = = = 3 x

745.86

=

4.5 x Full load Current 4.5 x 165.75 746 A

x(

11000 0.545

0.211 x

x

0.9 + 0.0968 x 0.436 ) x 0.2 x 100

1

Conclusion 1 x 3C x 185 XLPE, AL conductor, armoured cable

CABLE SIZING CALCULATIONS FOR 6.6 KV LOADS REV

S.NO

TAG. NO.

FEEDER  DETAILS

RATED RATED POWER KW POWER KVA

RATED VOLATGE KV

RATED CURRENT

STARTING CURRENT

RATED I / D.F.

Area of the conductor for

CURRENT CARRYING CAPACITY

COS f

SIN f  

CABLE

SIZE

current

I

6.6kV UNIT SWITCH BOARD-1

1

INCOMER FROM UAT-1

2

INCOMER FROM 6MVA DG1

3

TIE TO COMMON SWITCHBOARD 1A

LENGTH

RUN

HT cables to withstand Short circuit TYPE

(m)

(NO)

R

X

VD %

ST VD %

ST VD VD LIMIT LIMIT ALLOWABL ALLOWABL E E

I. USB-1 -

-

-

6.6

1250.00

5625.00

1644.74

1030

0.9

0.435889894

114.2857143

1C x

630

XLPE

100

2

0.039

0.104

0.079243833

0.356597248

VD < 5 %

STVD< 15%

-

-

-

6.6

1250.00

5625.00

1644.74

1030

0.9

0.435889894

114.2857143

1C x

630

XLPE

100

2

0.039

0.104

0.079243833

0.356597248

VD < 5 %

STVD< 15%

-

-

-

6.6

1250.00

5625.00

1644.74

1030

0.9

0.435889894

114.2857143

1C x

630

XLPE

100

2

0.039

0.104

0.079243833

0.356597248

VD < 5 %

STVD< 15%

4

TIE TO USB-2

-

-

-

6.6

1250.00

5625.00

1644.74

1030

0.9

0.435889894

114.2857143

1C x

630

XLPE

100

2

0.039

0.104

0.079243833

0.356597248

VD < 5 %

STVD< 15%

5

SFC TRANSFORMER1

T

-

1760

6.6

162.06

729.28

213.24

240

0.9

0.435889894

114.2857143

3C x

120

XLPE

100

1

0.197

0.102

0.05658967

0.254653515

VD < 5 %

STVD< 15%

6

SFE TRANSFORMER1

T

-

850

6.6

78.27

352.21

102.99

240

0.9

0.435889894

114.2857143

3C x

120

XLPE

100

1

0.197

0.102

0.027330238

0.122986073

VD < 5 %

STVD< 15%

7

UST-1

T

-

2000

6.6

184.16

828.73

242.32

240

0.9

0.435889894

114.2857143

3C x

150

XLPE

75

1

0.159

0.099

0.040507416

0.182283373

VD < 5 %

STVD< 15%

8

HP FEED WATER PUMP-1

M

2080

-

6.6

212.81

957.65

280.01

305

0.9

0.435889894

114.2857143

3C x

185

XLPE

75

1

0.127

0.097

0.039351547

0.177072101

VD < 5 %

STVD< 15%

9

HP FEED WATER PUMP-2 (STAND BY)

M

2080

-

6.6

212.81

957.65

280.01

305

0.9

0.435889894

114.2857143

3C x

185

XLPE

150

1

0.211

0.097

0.116702224

0.525140287

VD < 5 %

STVD< 15%

10

CONDENSATE FORWARDING PUMP1

M

224

-

6.6

22.92

103.13

30.16

240

0.9

0.435889894

114.2857143

3C x

120

XLPE

150

1

0.197

0.102

0.012003869

0.054015179

VD < 5 %

STVD< 15%

11

CONDENSATE FORWARDING PUMP3 (STSNDBY)

M

224

-

6.6

22.92

103.13

30.16

240

0.9

0.435889894

114.2857143

3C x

120

XLPE

150

1

0.197

0.102

0.012003869

0.054015179

VD < 5 %

STVD< 15%

12

UST-3

T

-

2000

6.6

184.16

828.73

242.32

270

0.9

0.435889894

114.2857143

3C x

150

XLPE

75

1

0.159

0.099

0.040507416

0.182283373

VD < 5 %

STVD< 15%

13

UST-5

T

-

2000

6.6

184.16

828.73

242.32

270

0.9

0.435889894

114.2857143

3C x

150

XLPE

75

1

0.159

0.099

0.040507416

0.182283373

VD < 5 %

STVD< 15%

FINAL CABLE SIZE

TOTAL LENGTH

1Cx630

600

1Cx630

600

1Cx630

600

1Cx630

600

3Cx120

100

3Cx120

100

3Cx150

75

3Cx185

75

3Cx185

150

3Cx120

150

3Cx120

150

3Cx150

75

3Cx150

75

FINAL CABLE SIZE

TOTAL LENGTH

1Cx630

600

1Cx630

600

1Cx630

600

1Cx630

600

3Cx120

100

3Cx120

100

3Cx150

75

3Cx185

75

3Cx185

150

3Cx120

150

3Cx120

150

3Cx150

75

3Cx150

75

USB-1 CABLE SIZE (SQMM)

CABLE T YPE

1Cx630 3Cx185 3Cx150

CU CU CU CU

3Cx120

TOTAL LENGTH (mtr) 2400 225 225 500

USB-1 CABLE SIZE (SQMM)

CABLE T YPE

1Cx630 3Cx185 3Cx150

CU CU CU CU

3Cx120

TOTAL LENGTH (mtr) 2400 225 225 500