Vector Group of 3 winding transformer

The harmonics in a transformer are present only in the transformer inrush current (predominantly 2 nd harmonic content). This cannot be avoided by selecting a tansformer with a particular vector group. In other words the vector group of a transformer cannot aid in eliminating the harmonic content in its inrush current.

From your question above, I presume that ur understanding of the transformer is not complete. Please note that u cannot have two different vector group on a single transformer,i.e, u cannot have DYn5 on pri winding and DYn11 on the secondary winding. The transformer can either be DYn5 or DYn11 or of any other vector group.

If anyone has a different suggestion, pls pour it in....

DYn5

D (capital letter) = Delta Connected HV side (usually but not necessarily primary)

y (small) = Star Connected LV Side.

n = neutral point of star brought out.

5 = (5 x 30= 150 degrees) phase shift between primary and secondary.

So this is taking care of both primary and secondary.

The harmonic suppression is only done for the third order by the Dy conenction (the secondary y will take the zero sequence current to earth/ neutral.

However there are special vector groups, the Dz comes to mind (z = zigzag secondary) that has the added suppression of 5th order.

Or you have multiple secondaries (eg Dyd blocking the fifth and seventh order harmonics)...

But note the z and others mentioned are rarely used in power transformers (I have never come across)

What order harmonics you want to suppress?

It's a six pulse drive, so I'm expecting to reduce the 5th and 7th harmonics.

I have read somewhere, that when you want to supply 2 drives from 2 transformers, you have to select the vector group for each transformer so that the harmonic content of one transformer will suppressed by others.

But the condition I had is like this, there are three drives, and each drive is fed from three winding transformer, and both of the winding have a Dyn5 vector group. Is it correct? Or should I change the vector group of other winding?

Not the group but the connection of the secondaries. Go for Dynd as mentioned in the end of #2

In my openion, generally three winding transformer is used for 12 pulse drives to have 30 degree phase shift for two 6 pulse drives which finally consist of 12 pulse drive. if your system is of 6 pulse and you have to have to reduce 5 and 7 harmonics because of facing of disadvantages of harminic rich envirnment you have three ways (1) change system to 12 pulse drives, which is perhaps costlier solution (2) put a active filter, which is also a costliest solution (3) put a detuned filters for 5 and 7 harmonic., which is somewhat cheaper solution. Also, Please refer IEEE-519, it is important that what is your point of coupling I.e. Point at which you are measuring harmonics. A harmonic study would give more clear picture on this point and then you could decide which harmonic is having more impact and accordingly decide further course of action depending on severity. In my openion, your read interpretation may be not proper. Transformer is not the devise to supress harmonics, but it helps us in 3 rd harmonics. For curiosity about transformer and vector group read J&P transformer book. Hope this satisfies your query.

@smenon

Then, what is the meaning of the three winding transformer with vector group of: Dyn11d0?

The harmonics are present not only during the inrush current of transformer. When you have non linear load, you can expect harmonics from time to time.

This is a 3 wnding trasnformer with the HV side on Delta and the secondaries of Star & Delta. Its just a single vector group for the whole trasnformer. So am again stressing that one trasnformer cannot have 3 sets of vector group on all 3 windings.

Yes on the harmonics part u r correct.

Dear Mr.Local Eng,

This topic was discussed several times.

Pl.open the link below and read and you will get your answer.

http://cr4.globalspec.com/search/sitesearch?do=show&order=asc&sort=textmatchrank&srch=transformer%20vector%20group

DHAYANANDHAN.S