Transformer Vector Groups

dear,

Transformer vector group depends upon

1. removing harmonics - d/y connection - y winding nullifies 3rd harmonics, preventing it to be reflected on delta side.

2. parallel operations - all the transformers should have same vector group & polarity of the winding.

3. 3 phase d/d transformers does not have neutral. to restrict the earth faults in such systems, we may use zig zag wound transformer to create a neutral along with the earth fault relay..

4. systems having say 3 bigger transformers of 1.5 mva each, & harmonics / non lionear loads e.g. furnace heaters - vfds etc.. we may use Dyn11, Dyn21, Dyn31 configuration, wherein, 30 deg. shifts of voltages nullifies the 3rd harmonics to zero in the supply system.

Normally, Vector group used is Dyn11 for standard distribution systems - wherein 3rd harmonics are zero on the supply system. -& providing 3 phase 4 wire out put. - along with saving in COPPER MATERIAL.

However, you have to specify the special requirements of vector group - prior to manufacturing / finalising the order - design - costing.

Thanks

Reqest to clarify one more doubt is

-As you said Dyn11 is used Normally for standard distribution,but why ?

Why we cannot take Dyn1 or any other vector group,What r the merits or demerits of Dyn11 compare to other vector group Dyn1/Dyn5 etc..(What is Dyn21 & Dyn31,I am in feeling that vector group can be in 0 to 11 in number just like clock).

Again thanks for clearing my earlier doubt.

Hello SJAT

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http://www.springerlink.com/content/bqval8gmvbrv0vwt/

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The idea of these vector groups it to synchronise the phases of the 'in' and 'out' of the power to the transformer.

I know it is a lot more complicated than that, and I have pasted the site address above in 'bold'

The preface of the page is below in 'bold' again. You may have to enlarge the page on the site the above address should lead to.

Let me know if it works and is of help please?

Received: 1 September 2003 Accepted: 9 January 2004 Published online: 28 February 2004 Abstract Transformer differential protection is exposed to faulty operation related to abnormal operation conditions (inrush, overexcitation, etc.). In this paper a new approach to improve the relay security and dependability is proposed, based on the space-vector analysis of the differential signal, and on their time characteristic shapes in Parks plane. The approach is supported by an introductory formulation and later validated. The technique has been shown to be robust and very simple for the purpose of detecting internal faults. Keywords Transformer - Internal fault - Park - Differential relaying - Symmetrical components

Hello SJAT,

Please find the search address with various sites available to view to you.

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http://www.google.com/search?hl=en&client=safari&rls=en-gb&ei=3cRmSu2NJtfPjAfG8ISXAQ&sa=X&oi=spell&resnum=0&ct=result&cd=1&q=Can+Transformer+be+designed+or+manufactured+after+finalization+of+Vector+group+or+vector+group&spell=1

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I hope this helps. Keep in touch.

Hello SJAT,

Here is a search I did to help you choose the correct Transformer. Though if you are not experienced enough to do this yourself, it may be a job for another person to do? No insult but, you should know what you are doing?p]

http://www.google.com/search?hl=en&client=safari&rls=en-gb&ei=q8dmSpDUMofSjAeSwoWeAQ&sa=X&oi=spell&resnum=0&ct=result&cd=1&q=what+type+of+Transformer+vector+group+we+have+to+select&spell=1

Take a look and let me know.

SJ,

The vector group is not something that can be selected freely, it derives from the angle difference between primary and secondary winding (same phase). There are only 3 basic ways of connecting the coils of a transformer (either primary or secondary):

- Y/star/wye, where all winding ends are connected together

- D/delta, where each end of a winding is connected to the beginning of the following winding.

- zig-zag connection, where the winding of each phase is divided into 2 and the first half of one phase(transformer column) is connected to the second half of the next column (in series), etc

The number of turns for each phase depends on the voltage, so a transformer can be fed from a source with primary voltages with a ratio of sqrt(3) if the same winding is used. The rating (kVA) of it differs in this case.

In case of a winding split into 2 parts, those parts (corresponding for one phase/column can be connected in series or in parallel for Y or delta, but in such case the applied voltage ratio would be 1 : 2. (The series connection leads to a zig-zag connection).

When designing a transformer, it is designed with a certain voltage (both primary and secondary) in mind, so the final number of turns is determined, thus the total number of turns per phase is corresponding to either phase-to-phase voltage (delta) or phase-to-neutral (Y) . In case of the zig-zag connection, the voltage applied along the 2 halfs is that of line-to-neutral.

If all coil terminations are brought out to the terminal box ( 2 per phase in case of Y or delta (per primary/secondary), thus a total of 6 and 4/phase(total 12) in case of zig-zag) , there is some flexibility possible depending on where connections are made (Y) and how to allocate (consider) the 3 phases (A,B,C) on the secondary part.

Delta connections annihilate the 3rd harmonic and zig-zag connections can be used as grounding banks since they provide an easy path for in-phase currents while limiting out-of-phase currents.

Please see also http://www.scribd.com/doc/7165661/The-Composition-of-Transformer

and http://books.google.com/books?id=Sf1ppwGI6uYC&pg=PA42&lpg=PA42&dq=advantages+of+zigzag+connection+of+transformers&source=bl&ots=NqeNKAxYA7&sig=VzWgP4xAHDm7foboAfHqFN9eGVQ&hl=en&ei=MlpnStG5BsKtlAfBnZjdDA&sa=X&oi=book_result&ct=result&resnum=4

Dear Suryakant,

Regarding your question No 2 only after you confirm the Vector Group to the Transformer Manufacturer they will go for the manufacturing of the same.

For your answer to Question 1 I will try to answer later.

Bye

JNC