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2x660 MW IB TPS (UNIT-3 4), BANHARPALLI

Design Memorandum For Grounding System

Doc. No. PE-DC-391-509-E002

Revision 0

2

DEVELOPMENT CONSULTANTS

PRIVATE LIMITED

Reviewed for general conformance with Contractdrawings and specifications.

ACTION : 1

1 Approved 4 Disapproved.

2 Approved except asnoted. Forward finaldrawing.

5For information/referenceonly.

3 Approved except asnoted. Resubmissionrequired.

Blank

Approval of Contract documents by the Consultant shallnot relieve the Seller of his responsibility for any errorsand fulfilment of Contract requirements.

Digitally signed by Shouvik Patari

DN: cn=Shouvik Patari, o=DCPL,

ou=DCPL,

[email protected]

m, c=IN

Date: 2014.01.30 16:08:27 +05'30'



Design Memorandum For Grounding System2x660 MW IB TPS (UNIT-3 & 4), BANHARPALLI

Doc. No. PE-DC-391-509-E002

Rev No: 0

Date: 19.02.13

INDEX

S. No. DESCRIPTION SHEETNO.

1. SCOPE 3

2. DESIGN PHILOSOPHY – BELOW GRADE GROUNDING 3-4

3. DESIGN PHILOSOPHY – ABOVE GRADE GROUNDING 4-5

4. REFERENCES 5

5. ANNEXURE-A1: CALCULATIONS OF GROUNDINGCONDUCTOR SIZE

ANNEXURE–A2: ETAP REPORT –GROUND GRID INPUTDATA & RESULTS

6-7

8-10

6. ANNEXURE-B: MATERIAL AND SIZE DETAILS OF BELOWGRADE AND ABOVE GRADE GROUNDING SYSTEM

11-14

2

02.01.14

14

15-18

(i) SAMPLE CALCULATION 19




Doc. No. PE-DC-391-509-E002

Rev No: 0

Date: 19.02.13

1.0 SCOPE

1.1 This document covers the design of below and above grade grounding system forthe main plant area of 2x660 MW IB TPS (UNIT-3 & 4), BANHARPALLI.

1.2 The following aspects of below grade grounding system design are covered:(a) Determination of size of ground conductor.

(b) Establishing the ground grid configuration.(c) Determination of ground grid resistance.(d) Check on Step and Touch potential.

1.3 The methodology and material details of above grade grounding system are alsocovered in this document.

1.4 The following calculations/ details are not covered in this document:

(a) Grounding for switchyard areas (OPGCL Scope).(b) Grounding for Coal Handling area / Ash Handling area (CHP & AHP vendor

Scope).(c) Grounding for plants & facilities not part of Main Plant Package.

Further, interconnection of aux. Plants/ other areas grounding grid with mainplant grounding grid shall be in Customer’s scope inline with Cl. 2.1.2 below.

2.0 DESIGN PHILOSOPHY OF BELOW GRADE GROUNDING SYSTEM

2.1 Type of grounding

2

02.01.14




Doc. No. PE-DC-391-509-E002

Rev No: 0

Date: 19.02.13

details of electronic grounding, system supplier, BHEL/EDN documentation shallbe referred.

2.1.6 All system neutrals (including neutrals of power transformers), groundingterminals of EHV surge arrestors and EHV voltage transformers are connected totwo nos. treated test pits, which in turn are connected to the ground grid.

2.1.7 All lightning protection down conductors are connected to dedicated groundelectrodes through isolating links and then to the grounding system.

2.1.8 The sizes of conductors for below grade grounding are tabulated in Annexure-C,Table-1.

2.2 Design Criteria

2.2.1 Average soil resistivity has been computed based on Soil Resistivity Measurements(Test results are attached at Annexure-D) furnished by OPGCL as part of ContractSpecification “ Vol-A: Geo technical Investigation Report”.

2.2.2 The size of grounding conductor is based on the maximum ground fault currentvalue of 50 kA for 1 second, with all below grade joints being welded type. Theminimum rate of corrosion of steel for selection of grounding conductor isconsidered as 0.12 mm per year. The grounding grid has been sized for a power

plant life of 40 years.

2.2.3 For a fault located within power station premises, the ground grid design is basedon the maximum fault current that is expected to occur during the design life of

2

02.01.14




Doc. No. PE-DC-391-509-E002

Rev No: 0

Date: 19.02.13

3.1.3 75x10 mm galvanised M.S. flats are run as main earth conductor along buildingcolumns / walls and securely fixed to the same by welding / clamping at intervalsnot exceeding 750 mm. Connections from runway conductor/submats are made tothe main earth conductor.

3.1.4 Railway tracks are bonded across fish plates and earthed at regular intervals. Atthe point where rail track leaves plant area, the rail section is provided with

insulated joint at both ends.

3.1.5 Metallic hand rails, fencing of transformer yard, etc. are connected to the belowground earthing system. Earthing conductor is buried at least 2000 mm outsidethe fence of electrical installations. Every alternate post of the fences and all gatesare connected to earthing grid by one lead.

3.1.6 Each street lighting pole/flood light pole and lighting mast will be grounded by

35x6 mm GS flat, which will be connected to two no. 40 mm dia & 3m longearthing spike, directly driven into ground at a depth of 1 meter from groundlevel. The junction box at each lighting pole is grounded at two (2) points fromtwo (2) nos. earthing terminals by 16 SWG GI wire. One 16 SWG GI wire shall betaken upto the junction box from lighting fixtures and connected to groundingpoint.

3.1.7 Cable screens and armour (wherever applicable) are earthed at both ends for

multi core cables. For single core cables, the same is done at switchgear end only.

3.1.8 Above grade ground conductor connections are welded except at the equipmentend, where the connections are bolted.

2

02.01.14



ANNEXURE- A1

CALCULATION OF GROUNDING CONDUCTOR

SIZE



Doc. No. PE-DC-391-509-E002

Rev No. 00

CALCULATION OF GROUNDING CONDUCTOR SIZE Annexure-A1

As per equation 40 of IEEE-80-2000 cross sectional area of earthing conductor shall be:

A (mm2)= I x sqrt [ {( tc x r x r x 104)/ TCAP}/ ln { (K 0 + Tm)/ (K 0 + Ta)}]

where,

A= Conductor cross section in sq. mm.I= Ground fault current (rms) in kA = 50 kA

tc= Time of flow of current = 1 sec.r= Thermal coefficient of resistivity = 0.00423 deg. C

(for mild steel as per CBIP manual TR-5) at 20 deg. C

r= = 15 micro-ohm cm

(for mild steel as per CBIP manual TR-5)

TCAP = Thermal capacity factor in J/cu.cm./ deg.C= 4.184 x SH X SW [As per Eq. 39 of IEEE-80-2000]

SH = Specific heat in Cal/gm/deg. C = 0.114

(for mild steel as per CBIP manual TR-5)SW = Specific weight in gm/cc = 7.86

(for mild steel as per CBIP manual TR-5)Hence,

TCAP = 4.184 x 0.114 x 7.86 = 3.749

Tm = Max. allowable temp. = 620 deg. C

(for mild steel as per CBIP manual TR-5)

Ta = Ambient temperature = 50 deg. C

Tr = Reference temperature 20 deg. C


2x660 MW IB TPS (UNIT-3 & 4), BANHARPALLI

Ground conductor resistivity

19.02.13

2

02.01.14



ANNEXURE- A2

ETAP REPORT –GROUND GRID INPUT

DATA & RESULTS



Location: BANHARPALI

Engineer: VKS Study Case: GRD1

5.5.6C

Page: 1

SN: BHARATBHEL

Filename: OPGCL

Project: 2X660 MW BANHARPALI TPSETAP

Contract: 391

Date: 02-01-2014

IEEE Std 80-2000

Number of Ground Conductors: 31

Number of Ground Rods: 60

Total Length of Ground Conductors: 9614.00 m

Total Length of Ground Rods: 180.00 m

Ground Grid Systems

Electrical Transient Analyzer Program





5.5.6C

Page: 2

SN: BHARATBHEL

Filename: OPGCL


Contract: 391

Date: 02-01-2014

Ground Grid Input Data

System Data:

kg

for

Factor Fault

Factor

CpSf TsTc

kA

Total

Body CurrentConductorsDuration°CAvailable

for

Tf

Ground

for Sizing

Total Fault

Fault Duration (Seconds)

%

Projection

%

Division

X/R

Short-Circuit Current

Current Ambient Temp. Weight Freq.

Hz 50.0 50 50.00 14.0038.880 1.00 1.00 1.0073.4 100.0

Soil Data:

mm m mm Resistivity

Lower Layer Soil

Resistivity Depth

MaterialType Material Type

Upper Layer Soil

Depth Resistivity Surface Material

Material Type Clean limestone 3000.0 0.15 Moist soil 50.0 1.00 Moist soil 50.0

Type %

Conductivity

1/°C

@ 20 °C

r Factor

K0 @

0 °C

Temperature

Fusing

°C

Resistivity of Ground Conductor

@ 20°C .cm

Capacity

Per Unit Volume

J/(cm³.°C)

Thermal

Conductor/Rod

Material Constants:

Mild Steel, MS 10.8 0.00423 216.4 620.0 15.00 3.75Conductor & Rod





5.5.6C

Page: 3

SN: BHARATBHEL

Filename: OPGCL


Contract: 391

Date: 02-01-2014

Ground Grid Summary Report

%

Calculated %

CalculatedPotential Rise

Rg Step Potential Touch Potential

Volts VoltsVoltsVolts Tolerable Calculated Tolerable Calculated

Volts Ground

GPR

Ohm Resistance Ground

0.076 2209.9 338.7519.5 107.31730.265.2 6.2

Total Fault Current: 38.880 kA Reflection Factor (K): -0.967

Maximum Grid Current: 29.167 kA Surface Layer Derating Factor (Cs): 0.773

Decrement Factor (Df): 1.022

Grid area is smaller than 6.25 m² or greater than 10,000 m²

Report of Intermediate Constants for IEEE 80 Methods

- Correction factor for grid geometry regarding touch voltage (Kim): 2.891

- Correction factor for grid geometry regarding step voltage (Kis): 2.891

- Spacing factor for touch voltage (Km): 0.795



One-Line Diagram - OLV1 (Short-Circuit Analysis)

Gr i d1

Bus1

21 kV 8. 8

9 7 k V

Bus2

21 kV 8. 8

9 7 k V

Bus3

400 kV5 0 .0 k A

43. 8

U130346 MVAsc

3. 1

62. 07

Gen Uni t #2

660 MW

GCB- 2

T2

810 MVA

HVCB- 2

3. 1

62. 07

Gen Uni t #1

660 MW

GCB- 1

T1

810 MVA

HVCB- 1

Gr i d1

U130346 MVAsc

660 MWGen Uni t #2

660 MW

T1

810 MVA T2

810 MVA

Bus1

21 kV

Bus3

400 kV

Bus2

21 kV

Gen Uni t #1

5 0 .0 k A

8. 8 9 7

k V

43. 8

3. 13. 1

HVCB- 1 HVCB- 2

GCB- 1

62. 07

8. 8 9 7

k V

GCB- 2

62. 07




Gr i d1

Bus1

21 kV 8. 8

8 k V

Bus2

21 kV 8. 8

8 k V

Bus3

400 kV

244. 3 9

k V

4 4 .6 6 k A

25. 89

U130346 MVAsc

9. 4

0

0

Gen Uni t #2

660 MW

GCB- 2

T2

810 MVA

HVCB- 2

9. 4

0

0

Gen Uni t #1

660 MW

GCB- 1

T1

810 MVA

HVCB- 1

Gr i d1

U130346 MVAsc

Gen Uni t #1

660 MWGen Uni t #2

660 MW

T1

810 MVA T2

810 MVA

Bus1

21 kV

Bus3

400 kV

Bus2

21 kV

244. 3 9

k V

4 4 .6 6 k A

8. 8 8 k

V

0

25. 89

9. 49. 4

HVCB- 1 HVCB- 2

GCB- 1

0

8. 8 8 k

V

0

GCB- 2

0




Gr i d1

Bus1

21 kVBus2

21 kV 9. 0

5 k V

Bus3

400 kV

2 5 2.6 k V

3 8 .8 8 k A

28. 54

U130346 MVAsc

10. 36

0

0

Gen Uni t #2

660 MW

GCB- 2

T2

810 MVA

HVCB- 2

Gen Uni t #1

660 MW

GCB- 1

T1

810 MVA

HVCB- 1

NO

Gr i d1

U130346 MVAsc

Gen Uni t #1

660 MWGen Uni t #2

660 MW

T1

810 MVA T2

810 MVA

Bus1

21 kV

Bus3

400 kV

Bus2

21 kV

2 5 2.6 k V

3 8 .8 8 k A

28. 54

10. 36

HVCB- 1

NO

HVCB- 2

GCB- 1

9. 0 5 k

V

0

GCB- 2

0



ANNEXURE- B

MATERIAL AND SIZE DETAILS OF BELOW GRADE

AND ABOVE GRADE GROUNDING SYSTEM



Doc. No. PE-DC-381-509-E002

Rev No. 0

19.02.13

Annexure-B:

SL. NO. TITLE MATERIAL

1 MAIN STATION GROUNDING

GRID

MS ROD

2 EARTH CONDUCTOR IN

CONCRETE FLOOR

GALVANISED MS

FLAT

3 ELECTRODES IN TEST PITS MS ROD

4 ELECTRODES FOR

LIGHTNING PROTECTION

DOWN CONDUCTORS

MS ROD

5 OTHER ELECTRODES MS ROD

SIZE

40 MM. DIA

75X10

40 MM. DIA

40 MM. DIA

Material and Size Details Of Below Grade & Above Grade Grounding System



40 MM. DIA

TABLE-1: BELOW GRADE GROUNDING SYSTEM - CONDUCTOR SIZES

2

02.01.14



Doc. No. PE-DC-381-509-E002

Rev No. 0

19.02.13

Annexure-B:



SL.NO. TYPE OF EQUIPMENT SIZE (MM) MATERIAL NO. OF LEADS

1 RISERS 75 X 10 GALVANISED

STEEL FLAT

N.A.

2 SUB-MAT BURIED IN FLOOR

FINISH

75 X 10 GALVANISED

STEEL FLAT

N.A.

3 RUNWAY CONDUCTOR/ MAIN

EARTH LEAD ALONG COLUMNS

50 x 6 GALVANISED

STEEL FLAT

N.A.

4 11 kV/3.3 kV/ 415 V

SWITCHGEAR / MCC

75 X 10 GALVANISED

STEEL FLAT

TWO

5 SYSTEM NEUTRALS 75 X 10 GALVANISED

STEEL FLAT

TWO

6 415 V DISTRIBUTION BOARDS 50 x6 GALVANISED

STEEL FLAT

TWO

7 FUSE DISTRIBUTION BOARDS 50 X 6 GALVANISED

STEEL FLAT

TWO

8 11 kV & 3.3 kV MOTORS 50 X 6 GALVANISED

STEEL FLAT

TWO

9 415 V MOTORS : ABOVE 90 KW 50 X 6 GALVANISED

STEEL FLAT

TWO

Material and Size Details Of Below Grade & Above Grade Grounding System

TABLE-2: ABOVE GROUND EARTHING SYSTEM - CONDUCTOR SIZES

2

02.01.14



Doc. No. PE-DC-381-509-E002

Rev No. 0

19.02.13

Annexure-B:



18 RAILS & METAL PARTS, FENCE 35 X 6 GALVANISED

STEEL FLAT

ONE

19 TRANSFORMER TANKS/

RADIATORS

75 X 10 GALVANISED

STEEL FLAT

TWO

20 GENERATOR ENCLOSURE 75 X 10 GALVANISED

STEEL FLAT

TWO

21 WELDING OUTLETS 3-PHASE

RECEPTACLES

35 X 6 GALVANISED

STEEL FLAT

TWO

22 LOCAL PANELS, LIGHTING

POLES

35 X 6 GALVANISED

STEEL FLAT

TWO

23 LIGHTING FIXTURES,SINGLE -

PHASE RECEPTACLES

16 SWG GI WIRE ONE

24 LIGHTING DISTRIBUTION

BOARDS

50 X 6 GALVANISED

STEEL FLAT

TWO

2

02.01.14



1.0 TYPICAL SIZING CALCULATION FOR EARTHING CONDUCTORS OF PLANT AUXILIARIES

1.01

A=

I= 40000.00 Amperesc= . ec

A= 486.40 Square mm

Hence the Size chosen 65 x 10 mm is adequate

1.02 11 kV EQUIPMENT

A=

I= 40000.00 Amperesc= . ec

A= 486.40 Square mm


1.03 11 KV/ 3.3 KV/ 415 V SWITCHGEAR , MCCS

A=

I= 50000.00 Amperesc= 1.00 Sec

A= 608.00 Square mm


1.04 RISER, SUB-MAT

SAMPLE CALCULATION

NEUTRAL & ENCLOSURE EARTHING OF GENERATOR TRANSFORMER, STATION

TRANSFORMER, LT AUXILIARY TRANSFORMER, LT BUSDUCT, LT PCC/PMCC

( As per equation 33 of IEEE-80-2000 )



ct I 01216.0

ct I 01216.0

ct I 01216.0



ANNEXURE- C

SOIL RESISTIVITY DATA ANALYSIS



Doc. No. PE-DC-391-509-E002

Sl. No. AVERA GE SOIL RESISTIVITY (IN

OHM METER) AT 2 METER DEPTH

1 21.100

2 21.850

3 23.110

4 21.350

5 20.220

6 21.850

7 26.870

8 26.250

9 24.860

10 25.240

23.270

ERT 3

ERT 4

ERT 5

Net Average Resistivity (Ohm-m) at 2 M depth

ERT 6

ERT 7

ERT 8

ERT 9

ERT 10

Since the below grade earthing system is to be laid at a depth of 1M.

Soil resitivi ty value considered after taking suitable margin of over

100% = 50 (Ohm-m)

GROUNDING SYSTEM DESIGN MEMORANDUM Rev No. 01

2x660 MW IB TPS (UNIT-3 & 4), BANHARPALLI Date:19.02.13

Annexure-C: Soi l Resis tivi ty Data Analysis

ERT NO.

ERT 1

ERT 2

02.01.14

02



ANNEXURE- D

SOIL RESISTIVITY TEST RESULTS



-

,.,.-

51.

No.

ERT No.

Location

Spacing

in M tr.

1

2

3

4

2.00

I

3.00

-

9

9 00

Coo li

ng

Tower

4.00

,Ar

ea

6.00

8,00

2.00

-

3.00

10

10.00

Panel Bui lding

4.00

Area

6.0 0

8.0 0

Resistance

fn .(1

Mtr.

5

1.98

1 32

0.93

-

-

0 48

0 21

2 0i

1.82

1.45

0. 95

5

Resistivity In n crn.

6

2486 88

2486 88

2336 16

1808

64

1055 04

2524.56

3428. 88

3642 40

3579 60

1758 40

114

SWAYIN &

ASSOCJ.ATES

OPGC

j l r



- -

•.

-

.

cr I

SI. No.

ERT N o.

Location

Spacing In Mtr Re

slstarice In

n

Mtr.

Re

sistivity

in

n

cm

I

1 2

3 \

4

5

6

I

I

2. 00

2.1 4 268 7 84

I

I

3 00

1 12

21 10 08

7

7.0.0

SWitchya rd

Area

4 00

. 0.76

1909

12

6

00

0. 32

1205 76

8..00

0.0 7

351 68

2 00 2.09

2625 04

I

.

3 00

1.03

1940 52

S

8 00

Sw

itc

h

yard

Area •

4 00

0.68

17

08 16

6 00

0.28

1055 04

8 00

0.06

301 44

113

SWAYIN .

ASSOCIATES

OPG.C



I .

1

51.

No.

ERT No.

Location

Spacing .hi Mtl'.

1

2 3

4

2..00

3.00

TG Suilding

.

- '

4

4;

00

4.00

Are a

6.00

. 8.00

2.00·

3;0 0

5

5.00

Bo

ller Ar

ea

4.00

6. 00 .

8. 00 .

2.0 0

3.00

6

6.0

0 ·

Bo ner Area

4..00

6.00

8.00

-

112

'

,,-

,

,

. .

_

Resistance Ii ,

n

Nt-r;

t{esisthiity In n ·em.

. 5

I

(;

1.70

2135.20

0.85 · 1601 .40

0 30

753.60

0.07

263.76

0.00 0.00

1.61

2022. 16

-

0.79

1488.36

0. 29

728.48

0.04

J

150.72

0.00

0.00

1.74

2185 .44

0.98

1846.32

0.

47

1180.64

0.19 715.92

0.02

100.48

a·

r

. ;

.,

.

'

;

..,

,

'

'

OF GC

. ' - - - - ~ . - . - . --. . . . .

--

.

.

- : - . , . - ..,.__if.



A

SWAY

IN

ASSOCIATES

OPG

51

No.

1

1

2

3

ERT No.

2

1..00

2.00

3.0

·0

Location

3

Transformer

Area

Transformer

Area

TG

Building

Area

I ~ U L I I Q ~ Q

5QIL

B r ; ~ 5 T I V I T Y

.-

Spacing in Mtr. Resistance in

n

Mtr

4

I

5

2 00

\

1.68

3.00 0.84

4.00

0.26

6.00

I

0.06

8.00

0.00

2.00

1.74

3.00

0.92

i

4.00

0.41

6.00

0.12

8.00

0. 00

2.00

1.8

4

3 .00

1. 13

4.00

0 .77

6.00

0 .4 1

8 00

0 .09

111

I

-

I

Resistivity

in

n

e

m

6

2110.08

15

82.56

6

53.12

22

6.08

0.00

21

85.44

1733.28

1029.

92

45.2.16

I

0 .00

231

1.0

4

2

128.9

2

1

93

4 .24

15

44.

88

452.16

Grounding design basis

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