Transformer winding phase angle shift 3

[bazoomba]

What is the phase angle difference between a HV delta 3 wire to LV wye 4 wire power transformer. I know the LV is either leading or lagging the HV by 30' but which is it?. The vector drawing on the transformer (not able to show symbols here) is a delta triangle with H1 at bottom left, H2 at the top and H3 bottom right. The wye symbol is on it's side with X1 on the stem which points to the left (towards the middle of the delta triangle), X2 is at the left top of the Y, X0 in the center and X3 at the right top of the Y ( -< ). This is not an unusual transformer. I perform various tests on transformers and was asked that question. I asked 2 engineers and got two different answers.

 

[dpc]

For a transformer built to ANSI standards, the low side should lag the high side by thirty degrees. Based on your description of the relative positions of H1 and X1, I think that is what you have, but your description of X2 and X3 confuses me.

The transformer can be built with a 30 deg phase shift in either direction, but for U.S. transformer built to ANSI, the low will always lag the high, unless specified otherwise.

Hope that helps.

 

[flickstar]

I don't know if this helps, but if the transformer is type Dy1 then the low side lags the high side. If the transformer is type Dy11 then the low side leads the high side by 30 degrees. (This is assuming the phasors rotate anti-clockwise.)

If anyone knows better please correct me.

 

[busbar]

ANSI/IEEE standard C57.12.70 §8 lists assorted delta-primary/wye-secondary-configured phase displacements of 30°, 90°, 150°, 210°, 270°, or 330°. Related info in ANSI/IEEE C57.105.

http://www.cooperpower.com/Library/pdf/R201902.pdf

 

[1x1x1x]

Your transformer could be Dy1; Dy11; Dy7 or Dy5 vector group, it is depends on the power supply phase sequence (positive phase sequence = A-B-C or negative phase sequence = A-C-B) or the transformer winding connections.

 

[peterb]

Like dpc, I am confused by your wye winding configuration. Assuming that you mean that the X1-X0 vector is in phase with the H1-H3 vector, X2-X0 in phase with H2-H1 and X3-X0 in phase with H3-H2, then your transfpormer is indeed an ANSI standard unit. The secondary lags the primary by 30 degrees (for H1-H2-H3 phase rotation).
As 1x1x1x points out, reversing the phase rotation reverses the phase shift from lag to lead (30 degrees in either case - that is set by the winding connections)

 

[RRaghunath]

Your Transformer Vector Group is Dyn1.
You can establish the same through a simple test.

 

[bazoomba]

Thank you all for your helpful reply.

 

[bazoomba]

Thank you all for your helpful information. This is a great forum. I'll be back.
Your Pal, Bazoomba

 

[jbartos]

Suggestion: Reference:
1. Electrical Transmission and Distribution Reference Book by Central Station Engineers of the Westinghouse Electric Corporation, East Pittsburgh, Pennsylvania, 1964.
Section 13 Three-Phase Transformers on page 106.
To make sure that the connection is correct, present (for example):
C---H3 X3---c
B---H2 X2---b
A---H1 X1---a
Which is for &quot;Eag lags EAG by 30degrees&quot;

 

[HYDL]

I have some follow questions with regard to delta-wye transformer phase shift. I'm refering to transformere built in the USA to ANSI standards.

Is the phase shift different for delta-wye or wye-delta (like advanced or retarded).

Is the phase shift always advanced 30 degrees LV to MV and retarded 30 degrees MV to LV?

My application is a 480v generator emergency board stepped up to 12.47kv.......and then from the utility it will then go through another transformer 12.47 to 480 for the normal power distribution. So, it's important for the phase angle to end up the same at the normal power distribution as the generator emergency board.

 

[dpc]

For ANSI standard delta-wye or wye-delta transformers:

The low voltage side will lag the high voltage side by 30 degrees.

 

[RalphChristie]

I've written a FAQ regarding the meaning of vector symbols for two winding, three phase transformers.

faq238-1090

Regards
Ralph

 

[stevenal]

The phase shift depends not only on how the transformer windings connect to the bushings, but how the bushings are connected to the system. Some predecessors of mine chose a non-standard connection, leaving a good portion of our system 60 degrees out from the rest of our system and our neighbors'. These ANSI standard (DY1)transformers low sides lead the high sides by 30 degrees because of how they are connected. A good paper on the subject can be found at

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

 

[dpc]

I should also have pointed out that non-standard phase shifts can be ordered and provided. At large generating facilities, the auxiliary power or standby power transformer generally has to have a non-standard phase shift in order for everything to match up. Of course the options are limited by the laws of physics.

 

[HYDL]

Thank you all. This has been very helpful.