Earthing Conductor Sizing-tsl_pellet

EARTHING CONDUCTOR SIZING CALCULATION SHEET This sheet is the cover sheet for all subsequent sheets having the same document number. The revision index and a brief description of the revision shall be entered on the cover sheet. The last revision index shall be added to the document number on the cover sheet an equally applies to all sheets having that document number. The new revision index is shown on all sheets.

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RMS/JRY

09.6.2009

Name

Date

Prepared/Changed

Rev.

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DNB

Name

Name

09.6.2009

Status

Module Assembly Component

DG

Larsen & Toubro Limited Original Size

Scale

A4

_

DCC

Basis Document

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Job name:

Job-No.:

Eng.Serv.-No.

MEF

Kind of Revision Copying of this document, and disclosure of it to others and the use or communication of the contents thereof, are forbidden without express written authority by Lurgi Metallurgie GmbH. Offenders are liable to the payment of damages All

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First Issue

Date Released

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Reference

Eng.Serv.Title

Calculation Sheet

CALCULATION :

TATA PELLET

EARTHING CONDUCTOR SIZING CALCULATION

Document-No.:

O8121

Page :

Rev.

-

1

Calculation of Conductor Size of Subsoil Ground Grid REFERENCE : IEEE Std 80 - 2000 - IEEE Guide for safety in AC Substation Grounding

A mm 2

=

tc x α r x ρ r x 10 4 / TCAP l n [(K 0 +T m ) / (K 0 +T a )]

Ix

Parameters

Value

Unit

tc=duration of fault current for calculating conductor size of subsoil ground 

3

Sec

0.0016

Per OC

grid.

ar=Thermal co­efficient of resistivity at reference tempareture of 20 Deg.C of  subsoil ground grid conductor material.

ρr =Resistivity of subsoil ground grod conductor material at referecce  temperature of 20 Deg.C

15.9

3.28

K0

605

Tm= Maximum allowable temperature for subsoil ground grid conductor 

1510

O

Ta =design ground temperature

50

O

I= Symmetrical single line to ground fault current for calculating  conductor size of subsoil ground grid.

40

KA

Amm2= Conductor size of subsoil ground grid(min)

563.5676423

Sqmm

Concidured conductor size is 75x10 Sqmm

750

Sqmm

2

This size is ok, if value of Amm < Concidered conductor size is TRUE

Refer Table - 1 of IEEE - 80 - 2000 For Steel

Refer Table - 1 of micro Ohm Cm IEEE - 80 - 2000 For Steel

TCAP =Thermal capacity per unit volume

material.

Remarks As per TISCO spec.

J / (cm3.OC)

Refer Table - 1 of IEEE - 80 - 2000 For Steel Refer Table - 1 of IEEE - 80 - 2000 For Steel

C

Refer Table - 2 of IEEE - 80 - 2000 For Steel Assumed

C As per TISCO spec.

TRUE

IEEE Std 80-2000

IEEE GUIDE FOR SAFETY

Table 1—Material constants

Material conductivity (%)

αr factor at 20 °C (1/°C)

Ko at 0 °C (0 °C)

Fusinga temperature Tm (°C)

ρr 20 °C (µΩ·cm)

TCAP thermal capacity [J/(cm3·°C)]

Copper, annealed soft-drawn

100.0

0.003 93

234

1083

1.72

3.42

Copper, commercial hard-drawn

97.0

0.003 81

242

1084

1.78

3.42

Copper-clad steel wire

40.0

0.003 78

245

1084

4.40

3.85

Copper-clad steel wire

30.0

0.003 78

245

1084

5.86

3.85

Copper-clad steel rodb

20.0

0.003 78

245

1084

8.62

3.85

Aluminum, EC grade

61.0

0.004 03

228

657

2.86

2.56

Aluminum, 5005 alloy

53.5

0.003 53

263

652

3.22

2.60

Aluminum, 6201 alloy

52.5

0.003 47

268

654

3.28

2.60

Aluminum-clad steel wire

20.3

0.003 60

258

657

8.48

3.58

Steel, 1020

10.8

0.001 60

605

1510

15.90

3.28

Stainless-clad steel rodc

9.8

0.001 60

605

1400

17.50

4.44

Zinc-coated steel rod

8.6

0.003 20

293

419

20.10

3.93

Stainless steel, 304

2.4

0.001 30

749

1400

72.00

4.03

Description

aFrom ASTM standards. bCopper-clad steel rods based on 0.254 mm (0.010 in) copper thickness. cStainless-clad steel rod based on 0.508 mm (0.020 in) No. 304 stainless

steel thickness over No. 1020 steel core.

Equation (37) and Equation (38), in conjunction with Equation (39) (which defines TCAP), reflect two basic assumptions

42

a)

That all heat will be retained in the conductor (adiabatic process).

b)

That the product of specific heat (SH) and specific weight (SW), TCAP, is approximately constant because SH increases and SW decreases at about the same rate. For most metals, these premises are applicable over a reasonably wide temperature range, as long as the fault duration is within a few seconds.

Copyright © 2000 IEEE. All rights reserved.

IEEE Std 80-2000

tc Kf

IEEE GUIDE FOR SAFETY

is the current duration in s is the constant from Table 2 for the material at various values of Tm (fusing temperature or limited conductor temperature based on 11.3.3) and using ambient temperature (Ta) of 40 °C Table 2—Material constants Conductivity (%)

Tm a (°C)

Kf

Copper, annealed soft-drawn

100.0

1083

7.00

Copper, commercial hard-drawn

97.0

1084

7.06

Copper, commercial hard-drawn

97.0

250

11.78

Copper-clad steel wire

40.0

1084

10.45

Copper-clad steel wire

30.0

1084

12.06

Copper-clad steel rod

20.0

1084

14.64

Aluminum EC Grade

61.0

657

12.12

Aluminum 5005 Alloy

53.5

652

12.41

Aluminum 6201 Alloy

52.5

654

12.47

Aluminum-clad steel wire

20.3

657

17.20

Steel 1020

10.8

1510

15.95

Stainless clad steel rod

9.8

1400

14.72

Zinc-coated steel rod

8.6

419

28.96

Stainless steel 304

2.4

1400

30.05

Material

aSee

11.3.3 for comments concerning material selection.

Examples: Using Equation (42) for a 20 kA, 3 s fault a)

For soft drawn copper Akcmil = 20 × 7.00

3

= 242.5 kcmil use 250 kcmil b)

For 40% conductivity copper-clad steel conductor Akcmil = 20 × 10.45

3

= 362.0 kcmil use 19/#7 conductor

44

Copyright © 2000 IEEE. All rights reserved.