Yd-1 and Yd-5 1

[Sargardani]

Whats the major difference between Vector group Yd-1 and Yd-5 of a power transformer? Any advantages of one over another? Does it amtter if in a power plant some units have Yd-1 while others have Yd-5?

Sarg

 

[Skogsgurra]

Sarg,

There are (to my knowledge) no Yd1 transformers. The number indicates the phase shift in steps of 30 degrees (actually the position of phase a on an imagined clock face when the A phase is at 12 o'clock).

Perhaps you are referring to a Yd11 transformer (it has minus 30 degrees phase shift)?. Anyhow, there is no difference in performance between different connection groups within the Yd class. Different connection groups are sometimes used to feed rectifiers to reduce 5th, 7th harmonics.

Dy and Yz etcetera is something else. There, the connection group has an influence on triplene harmonics reduction, unbalanced loading and so on.

 

[stevenal]

Externally, the only difference is how the bushings are identified. See
link page 5/4. Same basic phasor picture. Might make paralleling a little confusing.

 

[Skogsgurra]

I got some education there, stevenal.

Thanks.

 

[busbar]

Another vector group list is pg 5 of

http://www.riedel-trafobau.de/english/pdf_eng/in_general/explanation.pdf

 

[busbar]

Another terse reference is page 26+ of verk.hi.is/~egill/raforkuk1/ 2003/skyggnur/9_spennar3.pdf

 

[mersin33]

skogsgurra,

why isn't there a transformer connection Yd1? As far as I know there is such a connection (I could not open any of the links given by stevenal and busbar - so I don't know if their references support this).

 

[ScottyUK]

Saltan,

There is a Yd1 connection. Skogsgurra's second post acknowledged this.







----------------------------------

If we learn from our mistakes,
I'm getting a great education!

 

[stevenal]

An excellent paper on the subject was presented at the Western Protective Relay Conference a few days ago. Here's a link:

http://www.basler.com/downloads/3phXfmrs.pdf

 

[stevenal]

Salton,

If clicking the link doesn't work with a pdf, try right clicking it and choosing "Save Target As." Then open the saved file after it has finished downloading.

 

[cuky2000]

QUESTION 1: What’s the major difference between Vector group Yd-1 and Yd-5 of a power transformer?
ANSWER 1: The major difference is the electrical offset of the windings in respect to each other is the electrical phase shift angle of 30 and 150 degrees for the Dy1 and Dy5 vector group connection respectively. (See figure below)

QUESTION 2: Any advantages of one over another?
ANSWER: No

QUESTION 3: Does it matter if in a power plant some units have Yd-1 while others have Yd-5?
ANSWER: All interconnected systems should have matching phase. Different vector groups in the same facility may be a cause of confusion and induce involuntarily human error from simple change in phase rotation to severe short circuit if two vector groups are interconnected.

 

[veritas]

Skogsgurra

The most common vector group used in our distribution network is YNd1. There are many Yd11's as well. In some instances we've had to change Yd1's to look like Yd11's or Yd3's (Yd5's are also possible). Similarly from a Yd11 one could get a Yd1, Yd9 or Yd5.

Hope this helps.

Regards.