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Active Contributor

Join Date: May 2012
Posts: 12

# Bus Bar Short Circuit Current Calculation

08/07/2012 5:22 AM

We are taking power supply from 40 KVA dg set and selected 100A , 415 V ,TPN ,50kA for 1 sec bus bar in LT Panel. Now we have selected 32A MCCB for outgoing feeder having cable size 4C, 6 sq mm Al cable to LDB. My question is how can we calculate fault level of bus bar in LDB.

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Join Date: Jan 2007
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#1

### Re: bus bar short circuit current calculation

08/07/2012 5:58 AM

How does a busbar fault get to the LDB if it is downstream and protected by a 32A breaker?

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Join Date: Nov 2008
Posts: 17
#2

### Re: Bus Bar Short Circuit Current Calculation

08/08/2012 10:02 AM

I think question is wrongly posted. Either it could be fault level at busbar for a fault at LDB or fault level at LDB for a fault at busbar.

Commentator

Join Date: May 2011
Posts: 84
#3

### Re: Bus Bar Short Circuit Current Calculation

08/08/2012 11:21 PM

Simple: Add %impedance of ur genset and %impedance of ur cable.

Then, Divide genset KVA with this total %impedance.

this gives you fault level in KVA for any fault in LDB.

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Join Date: May 2012
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#4

### Re: Bus Bar Short Circuit Current Calculation

08/14/2012 5:29 AM

We are taking power supply from 40 KVA DG set and selected 100A , 415 V ,TPN ,50kA for 1 sec bus bar in LT Panel. Now we have selected 32A MCCB for outgoing feeder having cable size 4C, 6 sq mm Al cable to LDB. My question is how can we calculate short circuit rating of bus bar in LDB.

Lighting load is 10kW.Plz can any 1 show calculation here.? How can I attach SLD for reference ?

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#5

### Re: Bus Bar Short Circuit Current Calculation

08/14/2012 9:38 AM

The short circuit current in your LDB will be limited by the feed conductor. (unless your busbar/buscomb is less than 6mm2) In any event it won't be more than the feed can provide.

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Participant

Join Date: Feb 2014
Posts: 1
#6

### Re: Bus Bar Short Circuit Current Calculation

02/06/2014 11:28 AM

will you please explain to calculate this fault level calculation for bus bar?