Transformer - Fault Condition - CR4 Discussion Thread

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MSCS Associate Join Date: Feb 2011 Location: Angul, orissa Posts: 25 Good Answers: 1	Transformer - Fault Condition 08/29/2011 1:08 PM
	Hello everybody, warm regards for the day. I have a small doubt regarding transformers. Assume that we have a 6.6 KV / 415 V transformer and that the transformer is charged through the 6.6 KV HT panel feeder, where as the LT side supplies a PMCC panel. Now suppose there has been a huge short circuit in one of the feeders of the PMCC panel and there is a considerable voltage dip on the LV side because of this. (say the voltage now is some 380 V for a very short period of time). Does this decrease in voltage effect the HT side voltage?? I mean will there be a decrease in the HT side voltage as well (To maintain a constant value of transformation ratio)? If no, is it logical enough to say that the transformation ratio of the transformer has changed for that particular period during which the fault persists or till the time the fault is cleared? Thank you all in advance. __________________ mscs
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wareagle Guru Join Date: Jun 2008 Location: Alabama Posts: 1604 Good Answers: 63	#1 Re: Transformer - Fault Condition 08/29/2011 2:49 PM
	I would say that there will be a voltage drop on the 6.6 kv feeder but not in relationship to the transformer turns ratio. The secondary VD is due to the transformer %Z and the impedance of the conductors in the fault path. The primary voltage drop is due to the impedance of the distribution feeder looking back to its source. The source is probable a distribution substation and that is about as far back as you need to look.
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V.I.Abraham Guru Join Date: May 2007 Location: Pune , India Posts: 875 Good Answers: 42	#2 In reply to #1 Re: Transformer - Fault Condition 08/29/2011 4:47 PM
	It is a real simple and good answer.GA.
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MSCS Associate Join Date: Feb 2011 Location: Angul, orissa Posts: 25 Good Answers: 1	#3 In reply to #1 Re: Transformer - Fault Condition 08/30/2011 6:18 AM
	Thank you Mr. Wareagle. So is it logical enough to say that the transformation ratio of the transformer is not maintained during such a condition? If that is the case, for that instant of time, the transformer cannot be called as a constant power device. Is that true? __________________ mscs
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V.I.Abraham Guru Join Date: May 2007 Location: Pune , India Posts: 875 Good Answers: 42	#4 In reply to #3 Re: Transformer - Fault Condition 08/30/2011 4:30 PM
	What do you mean by constant power device? A device that can deliver constant power to a varying load? The terminology is used for a power source which can provide power under varying load conditions like a primary cell or SMPS. A normal transformer does not come under that category of power source. It has all limitations and react with load conditions and not a constant power device.
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MSCS Associate Join Date: Feb 2011 Location: Angul, orissa Posts: 25 Good Answers: 1	#5 In reply to #4 Re: Transformer - Fault Condition 08/30/2011 11:11 PM
	Thank you Mr. Abraham. __________________ mscs
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MSCS (2); V.I.Abraham (2); wareagle (1)

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Transformer - Fault Condition