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Anonymous Poster #1

For 400V, 2.5 MVA Transformer, Fault Level

09/27/2014 6:56 AM

Hi,

what is the fault level for 400V, 2.5 MVA transformer in terms of kA/s ?

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#1

Re: For 400V, 2.5 MVA transformer, fault level..

09/27/2014 9:55 AM

42.

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#2

Re: For 400V, 2.5 MVA transformer, fault level..

09/27/2014 11:34 AM

Sorry. What is "kA/s"? The slope dI/dt? It depends on R and L of the circuit. If it was only "kA" was probably short-circuit current. What kind of fault: phase-to-phase, phase-to-ground, phase-to-ground-to-phase, three phase short-circuit [metallic, through arc].There are some unknown parameters as short-circuit voltage, ground resistance and other.

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Anonymous Poster #1
#3
In reply to #2

Re: For 400V, 2.5 MVA transformer, fault level..

09/27/2014 11:39 AM

I mean short time current rating in kA for 1 sec.

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#5
In reply to #3

Re: For 400V, 2.5 MVA transformer, fault level..

09/28/2014 2:51 PM

The limiting factor for system fault current is NOT the transformer itself but the switchgear, cabling and associated protection gear connected to the transformer.

This sounds like homework.

If you want to know the fault level of the transformer then talk with the transformer manufacturer as the value varies depending on transformer construction.

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#4

Re: For 400V, 2.5 MVA transformer, fault level..

09/27/2014 4:13 PM

Please identify yourself.

Indicate source fault level in MVA or kA.

Indicate Transformer percentage impedance.

Fault kA can be calculated with these input parameters.

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#6

Re: For 400V, 2.5 MVA Transformer, Fault Level

10/01/2014 2:30 PM

See:

IEC 60076-5 Power Transformers Part 5:Ability to withstand short circuit.Ch.4

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#7

Re: For 400V, 2.5 MVA Transformer, Fault Level

10/04/2014 12:31 PM

Hi,

Prospective short circuit current at transformer output terminal = (transformer full load current) divide by (transformer P.U. impedance). This works out to be 72KA, if 5% impedance is typically assumed. BTW fault level and prospective short circuit current are not expressed in KA/s.

Regards.

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Anonymous Poster #2
#8

Re: For 400V, 2.5 MVA Transformer, Fault Level

10/18/2014 2:06 AM

This means that you have to verify the maximum fault current at the 0.4kV side of the transformer. You can see more information on short circuit calculation here http://www.psa-outline.com/solutions/fault-anlysis/

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Anonymous Poster #2
#9

Re: For 400V, 2.5 MVA Transformer, Fault Level

10/24/2014 5:59 AM

To understand more how to calculate short-circuit currents based on IEC standard, find out this link http://www.psa-outline.com/short-circuit-currents-three-phase-ac-systems-iec-60909-0/

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