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Anonymous Poster

Short circuit calculation

09/30/2008 2:49 AM

Dear Sir,

In our project, we have around 84 number of 3.6 MVA distribution transformer & 4 numbers of 60 MVA power transformers. While designing Short Circuit Level, the designers considered only one 60 MVA transformer, one 3.6 MVA transformer & power cables only. Not all numbers of 60 MVA & 3.6 MVA transformers, Why? Any body please tell me the answer. If we considered one transformer, the impedance value is in one level and if we considered all the transformers, the impedance value whether increase or decrease and what will be the short circuit level. kindly answer? And what are the impacts if we considered all the transormers? Also, Please tell your answers and suggestions related this question.

Thank you.

Kailash
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V.Ambarani.
Associate
Engineering Fields - Power Engineering - New Member

Join Date: Nov 2007
Location: India
Posts: 42
Good Answers: 3
#1

Re: Short circuit calculation

09/30/2008 4:53 AM

Mr.Kailash

please provide Single Line diagram indicating the voltage levels, how the transformers are connected ,py&sy Voltage value ,percentage of impedence of transformers , cable size, length ,no of cores,no runs per phase to answer your quiestion.

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kailasamvv
Associate

Join Date: Aug 2008
Posts: 39
#2
In reply to #1

Re: Short circuit calculation

09/30/2008 5:11 AM

Dear Mr.Ambarani,

Power transformer rating 230/11KV, 60 MVA, 10% imp, Distribution transformer 11/0.433 V, 3.6 MVA or 2.5 MVA, 6.28%imp for 3.6 MVA and 6.25% for 2.5 MVA, Transmission line 25 KM, ACSR zebra conductor of 0.069 ohm reisitance at 20 degree, 11 KV XLPE cable of 250 M, 0.130ohm/km. Any more details, please mail me and request you to kindly clarify that what will be the short circuit level at medium voltage bus and LV bus.

Regards,
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wareagle
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United States - Member - New Member

Join Date: Jun 2008
Location: Alabama
Posts: 1604
Good Answers: 63
#3

Re: Short circuit calculation

09/30/2008 12:09 PM

Are the transformers connected in parallel? Otherwise I have the same questrions as V Ambarani.
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kailasamvv
Associate

Join Date: Aug 2008
Posts: 39
#4
In reply to #3

Re: Short circuit calculation

10/01/2008 5:04 AM

Dear sir,

No parallel operation

Regards,

kailash
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wareagle
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Join Date: Jun 2008
Location: Alabama
Posts: 1604
Good Answers: 63
#5

Re: Short circuit calculation

10/01/2008 11:59 AM

"In our project, we have around 84 number of 3.6 MVA distribution transformer & 4 numbers of 60 MVA power transformers. While designing Short Circuit Level, the designers considered only one 60 MVA transformer, one 3.6 MVA transformer & power cables only. Not all numbers of 60 MVA & 3.6 MVA transformers, Why?

You assume that you will have a fault on only one transformer. You would not ever expect to have a fault on all of the transformers at the same time. If they were operating in parallel then you would have to consider all of the transformers.
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kailasamvv
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Join Date: Aug 2008
Posts: 39
#6
In reply to #5

Re: Short circuit calculation

10/03/2008 12:56 AM

Dear Mr.Wareagle,

Thank you for your answer. I have done one short circuit calculation. I dont know whether it is correct or not. Kindly give ur mail ID. I will send to you and kindly give your remarks and advice to implement it. Thank you

regards,
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Anonymous Poster
#7
In reply to #6

Re: Short circuit calculation

10/03/2008 11:22 AM

Post your calculations here and we will check them.
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wareagle
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Join Date: Jun 2008
Location: Alabama
Posts: 1604
Good Answers: 63
#8
In reply to #6

Re: Short circuit calculation

10/03/2008 5:17 PM

Post you calculations here an we will look at them.
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Previous in Forum: power quality   Next in Forum: Why control votages are DC only?
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