Earth Conductor Sizing

2x330MW TPP, Mundra SEZ

Attachment-2 to Doc.No.6785-EL-DSN-633-001

SIZING CALCULATION FOR EQUIPMENT EARTHING S.No

Equipment

Fuse Rating

Earth fault current in kA, (I)

Earth fault current Required Steel conductor size withstand duration, sec (t) in sq.mm (15.76 X I X sqrt(t)

Required minimum conductor size, Selected steel conductor sq.mm size Material

symbol No. of Used leads

Main Earthing Grid 1

Buried in ground

2

Embe Embedd dded ed in Floo Floor/ r/Co Conc ncre rete te Slab Slabs s

3

Exposed Conductors

32 mm dia. Rod

MS

A

75 X10 mm Flat

MS

B

50X10 mm Flat

GS

C

GS GS

A A

Neutral Earthing 4

HV Neutral of Generator Transformer

31.5

5 6 7 8 9

HV Neutral of Station Transformer NGR of Station Transformer NGR of Unit Auxiliary Transformer LV Neutral of Auxiliary Transformer LV Neutral of Lighting Transformer

31.5 0. 2 0. 2 50.0 20.0

1 1 1 1 1 1

496.44 496.44 3 . 1 52 3 . 1 52 788 315.2

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 30

Enclosure Earthing Generator Transformer Station Transformer Unit Auxiliary Transformer 6. 6.6 kV Switchgear 6.6 kV Motors LT LT Transformers L T B u sd u c t s LT PCC/PMCC LT MCC/DB LT ACB operated Motors Battery Charger /DCDB Local Starters Lighting Mast/Pole Cable Trays Control Panel Junction Boxes Push Button stations 3 Phase Receptacles Structural Steel Columns Steel pipe rack Isolated Phase Bus duct Isolated Phase Bus duct Fence/Gate

31.5 31.5 0. 2 0. 2 0. 2 50.0 50.0 50.0 50.0 50.0 25.0 3. 5 5

1 1 1 1 0.2 1 1 1 0.5 0.2 0.5 0. 0 1 0. 0 1

496.44 496.44 3.15 3.15 1.41 788 788 788 557.2 352.4 278.6 5. 5 7. 9

31.5 31.5

1 1

496.44 496.44

31 32 33

LT Motors (Rating in kW) Upto 5.5 kW above 5.5kW & Up to 11 kW above 11kW & Up to 30 kW

3 5 11

0. 0 1 0.01 0.01

4. 7 7. 9 17.3

32.0 50.0

25.0 50.0 1 0 0. 0

16.0 16.0 16.0 16.0 16.0 16.0

50X10 50X10 25X3 25X3 75X12 50X8

16.0 16.0 16.0 16.0 16.0 16.0 16.0 16.0 16.0 16.0 16.0 16.0 16 . 0 16.0 16.0 16.0 16.0 16.0 16.0 16.0 16.0 16.0 16.0

50X10 50X10 25X3 25X3 25X3 75X12 75X12 75X12 75X8 50X8 50X6 8 swg 8 swg 50x6 25X6 8 swg 8 swg 25X6 50X6 50X6 50X10 Flat 50X10 Flat 25X6

16.0 16 . 0 16 . 0

8 swg 8 swg 25X6

2 2

2x330MW TPP, Mundra SEZ

Attachment-2 to Doc.No.6785-EL-DSN-633-001

S.No

Equipment

Fuse Rating

Earth fault current in kA, (I)

34 35

above 30kW & Up to 90 kW above 90kW & less than 160 kW

2 5 0. 0 3 1 5. 0

20 22

Earth fault current Required Steel conductor size withstand duration, sec (t) in sq.mm (15.76 X I X sqrt(t) 0. 0 1 31.5 0. 0 1 34.7

Required minimum conductor size, Selected steel conductor sq.mm size Material 25X6 16.0 50X6 16.0

symbol No. of Used leads