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BHEL Earthing Drawing

1. This document provides calculations for sizing earthing conductors for various plant auxiliaries. 2. It calculates the required cross-sectional area based on a formula that considers fault current and time using values of 50,000 amps and 1 second. 3. For most equipment, including generators, transformers, switchgear, motors over 90kW, and the system neutral, the calculation shows 65x10 mm conductor is adequate.

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Mohan Babu
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2K views17 pages

BHEL Earthing Drawing

1. This document provides calculations for sizing earthing conductors for various plant auxiliaries. 2. It calculates the required cross-sectional area based on a formula that considers fault current and time using values of 50,000 amps and 1 second. 3. For most equipment, including generators, transformers, switchgear, motors over 90kW, and the system neutral, the calculation shows 65x10 mm conductor is adequate.

Uploaded by

Mohan Babu
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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1.0 TYPICAL SIZING CALCULATION FOR EARTHING CONDUCTORS OF PLANT AUXILIARIES

1.01 NEUTRAL & ENCLOSURE EARTHING OF GENERATOR TRANSFORMER,


STATION TRANSFORMER, LT AUXILIARY TRANSFORMER, LT BUSDUCT,

 A= 0.01216   I   t c

I= 50000.00 Amperes
tc= 1.00 Sec
 A= 608.00 Square mm

Hence the Size chosen 65 x 10 mm is adequate

1.02 11 & 6.6 kV EQUIPMENT


 A= 0.01216  I   t c

I= 50000.00 Amperes
tc= 1.00 Sec
 A= 608.00 Square mm

Hence the Size chosen 65 x 10 mm is adequate

1.03 415 V SWITCHGEAR , MCCS , BATTERY CHARGER ,


DISTRIBUTION BOARDS, FUSE DISTRIBUTION BOARDS,
 A= 0.01216  I  t 
 
c

I= 50000.00 Amperes
tc= 1.00 Sec
 A= 608.00 Square mm

Hence the Size chosen 65 x 10 mm is adequate

1.04 SUB-MAT, RUNWAY CONDUCTOR/MAIN EARTH LEAD ALONG COLUMNS


 A= 0.01216  I   t c

I= 50000.00 Amperes
tc= 1.00 Sec
 A= 608.00 Square mm

Hence the Size chosen 65 x 10 mm is adequate

1.05 415 V MOTORS

ABOVE 90 KW
 A= 0.01216  I  t  
c

I= 50000.00 Amperes

tc= 1.00 Sec


 A= 608.00 Square mm

Hence the Size chosen 65 x 10 mm is adequate

ABOVE 30 KW UPTO 90 KW
 A= 0.01216  I  t 
 
c

I= 3000.00 in Amperes = Effective Short circuit current for 0.2 sec pre-arcing
time ( Refer enclosed fuse characterstics of siemens type 3 NA2)
tc= 0.20 Sec
 A= 16.31 Square mm

Hence the Size chosen 25 x 3 mm is adequate


 

ABOVE 5 KW UPTO 30 KW
 A= 0.01216  I  t 

c

I= 2000.00 in Amperes = Effective Short circuit current for 0.2 sec pre-arcing
time ( Refer enclosed fuse characterstics of siemens type 3 NA2)
tc= 0.20 Sec
 A= 10.88 Square mm

Hence the Size selected 8 SWG GI wire is adequate

Upto 5 KW
 A= 0.01216  I 
 t 

c

I= 600.00 in Amperes = Effective Short circuit current for 0.2 sec pre-arcing
time ( Refer enclosed fuse characterstics of siemens type 3 NA2)
tc= 0.20 Sec
 A= 3.26 Square mm

Hence the Size selected 8 SWG GI wire is adequate

1.06 SYSTEM NEUTRAL


The maximum system neutral fault current is 50 kA of the 415 system, so that
will be considered for calculations.
 A= 0.01216  I 
  t 
c

I= 50000.00 Amperes
tc= 1.00 Sec
 A= 608.00 Square mm
Hence the Size chosen 65 x 10 mm is adequate

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