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ELECTRICAL

EARTHING REASISTANCE CALCULATION AS PER IS:3043 Document No.

0

Rev. No.

A

Class

1

EARTHING RESISTANCE CALCULATION CONTRACT NO

:

PROJECT

:

CLIENT

:

SITE

:

UNDER REVIEW

C ONFIDENTIAL

A

All

NS

05/12/06

NST

SS

Rev.

Sheet

Name

Date

Name

Name

Prepared, revised

Checked

Owner Document No.

Date

Remark, kind of revision

Status

Approved Basis document

Q.L.

DL-No.

DCC

Project Name

Project No.

Sheet / of

0

0

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ELECTRICAL

EARTHING REASISTANCE CALCULATION AS PER IS:3043 Document No.

0

Rev. No.

A

Class

Index of Revisions Rev.

Sheet

Prepared, revised Name

Date

Checked Name

Remark, kind of revision

Approved Name

Date

Status

Project Name

Project No.

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1

ELECTRICAL

EARTHING REASISTANCE CALCULATION AS PER IS:3043 Document No.

0

Rev. No.

A

Class

1

Table of Contents Section

Page

General Notes

4

Calcualtion Basis

5

Earthing Resistance for Strip and Pipe electroed

7

Earthing Resistance for Strip, Cable and Pipe electroed

9

Project Name

Project No.

Sheet / of

0

0

3/9

3/9

GENERAL NOTES 1. This document is an annexure to GS E&C Main document " Grounding Calculations" Document no. 2. The calculations have been done based on GI Strip and Pipe data considered from IS:3043 3 The Calculations are subject to revision as & when the main document gets revised due to change in any Data

PURPOSE This calculation describe the Grounding calculation of the

REFERANCE DOCUMENTS 1 2 3 4 5 6

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Project No.

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ELECTRICAL

EARTHING REASISTANCE CALCULATION AS PER IS:3043 Document No.

0

Rev. No.

A

Class

A. EARTHING CALCULATION AS PER IS:3043 The following formulas are used for the spesification IS:3043 for calculations of Main Earthing Loop Resistance for Pipe Electrode and Strip Electrode and theselection of Cross sectional area of Earth Conductor. A.1

Resistance of Pipe Electrode Where, L = Length of of Rod/pipe (cm) Rp = 100 x ρ loge 4L

2 L

A.2

Ohms

d= Diameter of pipe (cm)

d

ρ = Resistivity of Soil (ohm-meter)

Resistance of Strip Electrode Where, L = Length of of Strip (cm) Rs = 100 x ρ loge 2L2 Ohms

2 L A.3

w = Depth of strip laying (cm)

wT

ρ = Resistivity of Soil (ohm-meter) T = Width of strip (cm)

Earth Conductor Size Where, I =RMS Value of Fault Current (Amp) S = Cross section area of conductor (mm²) t = Operating Time of disconnecting device (seconds) K = Factor dependent on material of conductor (taking from IS:3043 Table)

S = I√t K

A.4

Total Earth Electrode Area A = If / Id

Where, If = Fault Current (amp) Id = Electrode Current Dencity (A/m²)

Id = ( 7.57 x 103 ) / √ρ x t

Where, Id = Electrode Current Density (A/m²) ρ = Resistivity of Soil (ohm-meter) t = Operating Time of disconnecting device (seconds)

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ELECTRICAL

EARTHING REASISTANCE CALCULATION AS PER IS:3043 Document No.

0

Rev. No.

A

Class

EARTHING CALCULATION FOR GI STRIP AND GI PIPE ELECTRODE A. BASIC DATA REQUIRED FOR THE CALCULATION Maximum Fault Level

: : 3000 MVA : 254 MVA : 35 MVA : Second 1 : Ohm-meter 51 : 10% : Galvanised Iron Strip : Galvanised Iron Pipe : Lap welded : °C 50 : Ohm 1 80

132 kV 6.6 kV 415 V System Designed for Fault Duration Soil Resistivity (PS) Voltage Variation Earth Conductor Eartth Electrode Type of joints Max. Ambient temp. below ground Desired resistance of Erath grid K Factor for Steel B. FAULT CURRENT CALCULATION System Volatge (V) 132,000 6,600 415

Fault Level (MVA) 3,000.00 254.00 35.00

Fault Current (kA) 13.12 22.22 48.69

The earth conductor to be selected on the basis of highest fault current, i.e.,

48.69

kA at 415 Bus Voltage

C. CROSS SECTION AREA OF EARTH CONDUCTOR S = I√t = 608.67 K GI Strip Cross sectional ara Height (mm) Width (mm) 40 5 40 10 65 5 65 8 65 10

Sq. mm

Cross Sectional Area (mm²) 200 400 325 520 650

Hence, the GI Strip used for the main earthing mat is

65 x

No. of Conductor 3.04 1.52 1.87 1.17 0.94 10

mm² =

1

Nos.

D. CROSS SECTION AREA OF EARTH ELECTRODE Earth Electroed Current Density Id = ( 7.57 x 103 ) / √ρ x t Earth Electrode Area Taking extra Electrode Area (%) The Final Erath Electrode Area

: : : : :

1060.01 45.94 10 50.53

Amp / m² m² m²

THE TOTAL EARTH ELECTRODE AREA CONDIDERED FOR THE PLANT Perimeter of the unit : 2000 Meter Length of Strip Electrode : 2000 Meter Total surface area of a Strip Electrode : 260.00 Sq. Meter ……………….. (A) Nos. of GI Electrode Pipe Used in the plant Length of the GI Pipe Electrode Effective Buried Length Diameter of the GI Pipe Electride Total Surface area of the GI pipe Electrode

: : : : :

50 3.5 2.5 50 19.64

Nos. Meter Meter mm Sq. Meter …………………..(B)

Total surface area of GI Strip and GI Pipe = (A)+(B) =

:

279.65

Total Number of Earth Electrode

:

5.53

Project Name 0

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Sq. Meter Nos. Project No. 0

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ELECTRICAL

EARTHING REASISTANCE CALCULATION AS PER IS:3043 Document No.

0

Rev. No.

A

Class

EARTHING CALCULATION FOR GI STRIP AND GI PIPE ELECTRODE……… Contd. E. EARTH RESISTANCE OE THE STRIP ELECTRODE Resistivity of soil Length of strip Depth of Buried electrode Width of strip

: : : :

51 200000 50 6.5

EARTH RESISTANCE : Resistance for each strip electode Rs = 100 x ρ loge 2L2 Ohms

2 L

Ohm-meter Cm Cm Cm

: :

0.0784

Ohm

: :

1 0.0784

Ohm

wT

Nos. of Strip Electrode in parallel Resistance for all parallel Strip Eelctroed

………………………………. ( C )

F. EARTH RESISTANCE OE THE PIPE ELECTRODE Effective Buried Length Diameter of the GI Pipe Electride No. of Pipes in parallel (N)

: : :

250.00 5.00 50

Cm Cm Nos.

Earth resistance for each GI Pipe Electrode : Rp = 100 x ρ loge 4L

2 L

Ohms

=

17.19

Ohm

d

= R2

Resistance for all parallel GI Pipe Electroed

= (Rp/N) =

0.344

Ohm

…………………………………(D)

Combined Resistance of Earth due to Pipe Electrode and Strip Electrode =

R1 x R2 (R1 +R2)

=

0.0638

Ohm

Grounding system is valid for the combined resistance less than 1.0 Ohm GROUNDING SYSTEM IS

=

ACCEPTABLE

SUMMARY A. GI STRIP ELECTRODE SIZE OF ELECTRODE WIDTH (mm) HEIGHT (mm) 65 10

NO. OF ELECTRODE 1

B. GI PIPE ELECTRODE SIZE OF ELECTRODE LENGTH (mm) DIA (mm) 3500 50

NO. OF ELECTRODE 50

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ELECTRICAL

EARTHING REASISTANCE CALCULATION AS PER IS:3043 Document No.

0

Rev. No.

A

Class

EARTHING CALCULATION FOR GI STRIP ELECTRODE AND CABLE ELECTRONICS EARTH STATION A. BASIC DATA REQUIRED FOR THE CALCULATION Maximum Fault Level

: : 3000 MVA : 254 MVA : 35 MVA : Second 1 : Ohm-meter 51 : 10% : Galvanised Iron Strip : Galvanised Iron Pipe : Lap welded : °C 50 : Ohm 1 80

132 kV 6.6 kV 415 V System Designed for Fault Duration Soil Resistivity (PS) Voltage Variation Earth Conductor Eartth Electrode Type of joints Max. Ambient temp. below ground Desired resistance of Erath grid K Factor for Steel B. FAULT CURRENT CALCULATION System Volatge (V) 132,000 6,600 415

Fault Level (MVA) 3,000.00 254.00 35.00

Fault Current (kA) 13.12 22.22 48.69

The earth conductor to be selected on the basis of highest fault current, i.e.,

48.69

kA at 415 Bus Voltage

C. CROSS SECTION AREA OF EARTH CONDUCTOR S = I√t = 608.67 K GI Strip Cross sectional ara Height (mm) Width (mm) 40 5 40 10 65 5 65 8 65 10

Sq. mm

Cross Sectional Area (mm²) 200 400 325 520 650

Hence, the GI Strip used for the main earthing mat is

65 x

No. of Conductor 3.04 1.52 1.87 1.17 0.94 10

mm² =

1

Nos.

D. EARTH RESISTANCE OE THE STRIP ELECTRODE + CABLE Length of strip Depth of Buried electrode Width of strip

: : :

50000 50 6.5

Cm Cm Cm

EARTH RESISTANCE FOR STRIP ELECTRODE : Resistance for each strip electode : Rs = 100 x ρ log 2L2 Ohms e

:

0.2685

Ohm

Nos. of Strip Electrode in parallel Resistance for all parallel Strip Eelctroed

: :

1 0.2685

Ohm

EARTH RESISTANCE FOR CABLE Cable Cross Section Area Length of Cable Resistance of Cable Total Resistance of the Cable

: : : :

70 500 0.321 0.1605

Sq. mm Meter Ohm / Km Ohm …………………………………( B )

2 L

wT ………………………………. ( A )

:

TOTAL EARTH RESISTANCE FOR STRIP AND CABLE R1 = (A) + (B) =

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0.4290

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Ohm

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ELECTRICAL

EARTHING REASISTANCE CALCULATION AS PER IS:3043 Document No.

0

Rev. No.

A

Class

EARTHING CALCULATION FOR GI STRIP ELECTRODE AND CABLE ELECTRONICS EARTH STATION E. EARTH RESISTANCE OE THE PIPE ELECTRODE Resistivity of soil Effective Buried Length Diameter of the GI Pipe Electrode No. of Pipes in parallel (N)

: : : :

51 250.00 5.00 8

Ohm-meter Cm Cm Nos.

Earth resistance for each GI Pipe Electrode : Rp = 100 x ρ loge 4L

2 L

Ohms

=

17.19

Ohm

d

Resistance for all parallel GI Pipe Electroed

= R2

= (Rp/N) =

Combined Resistance of Earth due to Pipe Electrode and Strip Electrode =

R1 x R2 (R1 +R2)

=

0.3576

Ohm

2.1493

Ohm R1 R2

= =

0.4290 2.1493

Ohm Ohm

Grounding system is valid for the combined resistance less than 1.0 Ohm GROUNDING SYSTEM IS

=

ACCEPTABLE

SUMMARY A. GI STRIP ELECTRODE SIZE OF ELECTRODE WIDTH (mm) HEIGHT (mm) 65 10

NO. OF ELECTRODE 1

B. EARTING CABLE CABLE TYPE CONDUCTOR DIA (mm²) Cu 70

LENGTH OF CABLE (METER) 500

C. GI PIPE ELECTRODE SIZE OF ELECTRODE LENGTH (mm) DIA (mm) 2500 50

NO. OF ELECTRODE 8

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EARTHING REASISTANCE CALCULATION AS PER IS:3043 Document No.

0

Rev. No.

A

Class

1

EARTHING RESISTANCE CALCULATION CONTRACT NO

:

PROJECT

:

CLIENT

:

SITE

:

UNDER REVIEW

C ONFIDENTIAL

A

All

NS

05/12/06

NST

SS

Rev.

Sheet

Name

Date

Name

Name

Prepared, revised

Checked

Owner Document No.

Date

Remark, kind of revision

Status

Approved Basis document

Q.L.

DL-No.

DCC

Project Name

Project No.

Sheet / of

0

0

1/9

ELECTRICAL

EARTHING REASISTANCE CALCULATION AS PER IS:3043 Document No.

0

Rev. No.

A

Class

Index of Revisions Rev.

Sheet

Prepared, revised Name

Date

Checked Name

Remark, kind of revision

Approved Name

Date

Status

Project Name

Project No.

Sheet / of

0

0

2/9

1

ELECTRICAL

EARTHING REASISTANCE CALCULATION AS PER IS:3043 Document No.

0

Rev. No.

A

Class

1

Table of Contents Section

Page

General Notes

4

Calcualtion Basis

5

Earthing Resistance for Strip and Pipe electroed

7

Earthing Resistance for Strip, Cable and Pipe electroed

9

Project Name

Project No.

Sheet / of

0

0

3/9

3/9

GENERAL NOTES 1. This document is an annexure to GS E&C Main document " Grounding Calculations" Document no. 2. The calculations have been done based on GI Strip and Pipe data considered from IS:3043 3 The Calculations are subject to revision as & when the main document gets revised due to change in any Data

PURPOSE This calculation describe the Grounding calculation of the

REFERANCE DOCUMENTS 1 2 3 4 5 6

4/9

Project Name

Project No.

Sheet / of

0

0

4/9

ELECTRICAL

EARTHING REASISTANCE CALCULATION AS PER IS:3043 Document No.

0

Rev. No.

A

Class

A. EARTHING CALCULATION AS PER IS:3043 The following formulas are used for the spesification IS:3043 for calculations of Main Earthing Loop Resistance for Pipe Electrode and Strip Electrode and theselection of Cross sectional area of Earth Conductor. A.1

Resistance of Pipe Electrode Where, L = Length of of Rod/pipe (cm) Rp = 100 x ρ loge 4L

2 L

A.2

Ohms

d= Diameter of pipe (cm)

d

ρ = Resistivity of Soil (ohm-meter)

Resistance of Strip Electrode Where, L = Length of of Strip (cm) Rs = 100 x ρ loge 2L2 Ohms

2 L A.3

w = Depth of strip laying (cm)

wT

ρ = Resistivity of Soil (ohm-meter) T = Width of strip (cm)

Earth Conductor Size Where, I =RMS Value of Fault Current (Amp) S = Cross section area of conductor (mm²) t = Operating Time of disconnecting device (seconds) K = Factor dependent on material of conductor (taking from IS:3043 Table)

S = I√t K

A.4

Total Earth Electrode Area A = If / Id

Where, If = Fault Current (amp) Id = Electrode Current Dencity (A/m²)

Id = ( 7.57 x 103 ) / √ρ x t

Where, Id = Electrode Current Density (A/m²) ρ = Resistivity of Soil (ohm-meter) t = Operating Time of disconnecting device (seconds)

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Project Name

Project No.

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0

0

5/9

1

ELECTRICAL

EARTHING REASISTANCE CALCULATION AS PER IS:3043 Document No.

0

Rev. No.

A

Class

EARTHING CALCULATION FOR GI STRIP AND GI PIPE ELECTRODE A. BASIC DATA REQUIRED FOR THE CALCULATION Maximum Fault Level

: : 3000 MVA : 254 MVA : 35 MVA : Second 1 : Ohm-meter 51 : 10% : Galvanised Iron Strip : Galvanised Iron Pipe : Lap welded : °C 50 : Ohm 1 80

132 kV 6.6 kV 415 V System Designed for Fault Duration Soil Resistivity (PS) Voltage Variation Earth Conductor Eartth Electrode Type of joints Max. Ambient temp. below ground Desired resistance of Erath grid K Factor for Steel B. FAULT CURRENT CALCULATION System Volatge (V) 132,000 6,600 415

Fault Level (MVA) 3,000.00 254.00 35.00

Fault Current (kA) 13.12 22.22 48.69

The earth conductor to be selected on the basis of highest fault current, i.e.,

48.69

kA at 415 Bus Voltage

C. CROSS SECTION AREA OF EARTH CONDUCTOR S = I√t = 608.67 K GI Strip Cross sectional ara Height (mm) Width (mm) 40 5 40 10 65 5 65 8 65 10

Sq. mm

Cross Sectional Area (mm²) 200 400 325 520 650

Hence, the GI Strip used for the main earthing mat is

65 x

No. of Conductor 3.04 1.52 1.87 1.17 0.94 10

mm² =

1

Nos.

D. CROSS SECTION AREA OF EARTH ELECTRODE Earth Electroed Current Density Id = ( 7.57 x 103 ) / √ρ x t Earth Electrode Area Taking extra Electrode Area (%) The Final Erath Electrode Area

: : : : :

1060.01 45.94 10 50.53

Amp / m² m² m²

THE TOTAL EARTH ELECTRODE AREA CONDIDERED FOR THE PLANT Perimeter of the unit : 2000 Meter Length of Strip Electrode : 2000 Meter Total surface area of a Strip Electrode : 260.00 Sq. Meter ……………….. (A) Nos. of GI Electrode Pipe Used in the plant Length of the GI Pipe Electrode Effective Buried Length Diameter of the GI Pipe Electride Total Surface area of the GI pipe Electrode

: : : : :

50 3.5 2.5 50 19.64

Nos. Meter Meter mm Sq. Meter …………………..(B)

Total surface area of GI Strip and GI Pipe = (A)+(B) =

:

279.65

Total Number of Earth Electrode

:

5.53

Project Name 0

6/9

Sq. Meter Nos. Project No. 0

Sheet / of 6/9

1

ELECTRICAL

EARTHING REASISTANCE CALCULATION AS PER IS:3043 Document No.

0

Rev. No.

A

Class

EARTHING CALCULATION FOR GI STRIP AND GI PIPE ELECTRODE……… Contd. E. EARTH RESISTANCE OE THE STRIP ELECTRODE Resistivity of soil Length of strip Depth of Buried electrode Width of strip

: : : :

51 200000 50 6.5

EARTH RESISTANCE : Resistance for each strip electode Rs = 100 x ρ loge 2L2 Ohms

2 L

Ohm-meter Cm Cm Cm

: :

0.0784

Ohm

: :

1 0.0784

Ohm

wT

Nos. of Strip Electrode in parallel Resistance for all parallel Strip Eelctroed

………………………………. ( C )

F. EARTH RESISTANCE OE THE PIPE ELECTRODE Effective Buried Length Diameter of the GI Pipe Electride No. of Pipes in parallel (N)

: : :

250.00 5.00 50

Cm Cm Nos.

Earth resistance for each GI Pipe Electrode : Rp = 100 x ρ loge 4L

2 L

Ohms

=

17.19

Ohm

d

= R2

Resistance for all parallel GI Pipe Electroed

= (Rp/N) =

0.344

Ohm

…………………………………(D)

Combined Resistance of Earth due to Pipe Electrode and Strip Electrode =

R1 x R2 (R1 +R2)

=

0.0638

Ohm

Grounding system is valid for the combined resistance less than 1.0 Ohm GROUNDING SYSTEM IS

=

ACCEPTABLE

SUMMARY A. GI STRIP ELECTRODE SIZE OF ELECTRODE WIDTH (mm) HEIGHT (mm) 65 10

NO. OF ELECTRODE 1

B. GI PIPE ELECTRODE SIZE OF ELECTRODE LENGTH (mm) DIA (mm) 3500 50

NO. OF ELECTRODE 50

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1

Project Name 0

Project No. 0

Sheet / of 7/9

ELECTRICAL

EARTHING REASISTANCE CALCULATION AS PER IS:3043 Document No.

0

Rev. No.

A

Class

EARTHING CALCULATION FOR GI STRIP ELECTRODE AND CABLE ELECTRONICS EARTH STATION A. BASIC DATA REQUIRED FOR THE CALCULATION Maximum Fault Level

: : 3000 MVA : 254 MVA : 35 MVA : Second 1 : Ohm-meter 51 : 10% : Galvanised Iron Strip : Galvanised Iron Pipe : Lap welded : °C 50 : Ohm 1 80

132 kV 6.6 kV 415 V System Designed for Fault Duration Soil Resistivity (PS) Voltage Variation Earth Conductor Eartth Electrode Type of joints Max. Ambient temp. below ground Desired resistance of Erath grid K Factor for Steel B. FAULT CURRENT CALCULATION System Volatge (V) 132,000 6,600 415

Fault Level (MVA) 3,000.00 254.00 35.00

Fault Current (kA) 13.12 22.22 48.69

The earth conductor to be selected on the basis of highest fault current, i.e.,

48.69

kA at 415 Bus Voltage

C. CROSS SECTION AREA OF EARTH CONDUCTOR S = I√t = 608.67 K GI Strip Cross sectional ara Height (mm) Width (mm) 40 5 40 10 65 5 65 8 65 10

Sq. mm

Cross Sectional Area (mm²) 200 400 325 520 650

Hence, the GI Strip used for the main earthing mat is

65 x

No. of Conductor 3.04 1.52 1.87 1.17 0.94 10

mm² =

1

Nos.

D. EARTH RESISTANCE OE THE STRIP ELECTRODE + CABLE Length of strip Depth of Buried electrode Width of strip

: : :

50000 50 6.5

Cm Cm Cm

EARTH RESISTANCE FOR STRIP ELECTRODE : Resistance for each strip electode : Rs = 100 x ρ log 2L2 Ohms e

:

0.2685

Ohm

Nos. of Strip Electrode in parallel Resistance for all parallel Strip Eelctroed

: :

1 0.2685

Ohm

EARTH RESISTANCE FOR CABLE Cable Cross Section Area Length of Cable Resistance of Cable Total Resistance of the Cable

: : : :

70 500 0.321 0.1605

Sq. mm Meter Ohm / Km Ohm …………………………………( B )

2 L

wT ………………………………. ( A )

:

TOTAL EARTH RESISTANCE FOR STRIP AND CABLE R1 = (A) + (B) =

Project Name

0.4290

8/9

Ohm

Project No.

Sheet / of

1

0

0

8/9

ELECTRICAL

EARTHING REASISTANCE CALCULATION AS PER IS:3043 Document No.

0

Rev. No.

A

Class

EARTHING CALCULATION FOR GI STRIP ELECTRODE AND CABLE ELECTRONICS EARTH STATION E. EARTH RESISTANCE OE THE PIPE ELECTRODE Resistivity of soil Effective Buried Length Diameter of the GI Pipe Electrode No. of Pipes in parallel (N)

: : : :

51 250.00 5.00 8

Ohm-meter Cm Cm Nos.

Earth resistance for each GI Pipe Electrode : Rp = 100 x ρ loge 4L

2 L

Ohms

=

17.19

Ohm

d

Resistance for all parallel GI Pipe Electroed

= R2

= (Rp/N) =

Combined Resistance of Earth due to Pipe Electrode and Strip Electrode =

R1 x R2 (R1 +R2)

=

0.3576

Ohm

2.1493

Ohm R1 R2

= =

0.4290 2.1493

Ohm Ohm

Grounding system is valid for the combined resistance less than 1.0 Ohm GROUNDING SYSTEM IS

=

ACCEPTABLE

SUMMARY A. GI STRIP ELECTRODE SIZE OF ELECTRODE WIDTH (mm) HEIGHT (mm) 65 10

NO. OF ELECTRODE 1

B. EARTING CABLE CABLE TYPE CONDUCTOR DIA (mm²) Cu 70

LENGTH OF CABLE (METER) 500

C. GI PIPE ELECTRODE SIZE OF ELECTRODE LENGTH (mm) DIA (mm) 2500 50

NO. OF ELECTRODE 8

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