Simple question about vector group YnD11 ?

[rayas91]

Friends,

I have a question about vector group YnD11.

If we assume current flows from primary to secodary, angles will be Y (0°) - D (30°).


But if current flows secondary to primary , which angles will occur ? Y (30°) - D (0°)?

Thanks for your time.

 

[jghrist]

Your settings show the GSU high side wye winding at -330° (same as +30°). A Ydn11 transformer will have the wye winding -30° compared to the delta winding. Your settings show a third winding, but your one-line doesn't show a three-winding transformer. If your injected currents are into the relay on both sides, then it matches the relay settings for windings 1 & 2, but does not match a through fault for a Ydn11 transformer. As noted in my earlier post, the current into the transformer will be at +150°, not -150°, for a through fault.

 

[rayas91]

Third windng is the Y side of DYn1 transformer.

 

[DiscoP]

I believe for that diagram the expected current angle is +150 degrees for Ia on the 400kV side when Ia on the generator side is at zero degrees.

Using two captial letters makes this really confusing, but if the delta is the generator LV side we call this a YNd11

The d side is at +30 degrees when compared to the Y side reference, (or -330 deg or 11 o'clock)

So conversely the Y side is at -30 degrees if the d side is the reference which is what you are doing (or 1 o'clock)

You then need to add 180 degrees for the relay measurement (-30 + 180 = +150 degrees)

In the setting file, the delta side has been entered as the reference, the Y side is at -30 degrees to the reference, so the setting in the T60 should be -30.

For conventions, we normally connect the HV side as winding 1 and the LV side to winding 2, if you did this the setting would be -330 degs (or 11 o'clock).

Either way works, but I find this easier to follow.

 

[rayas91]

Discop ,

Can you look at the pic on attachment? I added my software pic during injection test.

At these conditions ,there s no trip. Primary Side is GEN side, I mean delta side is reference(This is my transf. Ynd11 but I use it reverely) .

 

[DiscoP]

I am getting an error message opening the file ?

 

[stevenal]

Probably the ? marks in the file name are causing an issue.

 

[rayas91]

sorry , I fixed it now, You can check it when you have free time.

 

[DiscoP]

Hi Rayas

The injection angles look correct for the settings shown in your T60 screenshot.

The relay has been set so the Wye side is as -330° with respect to the delta reference (or the Y side is at +30° with respect to the delta side).

However for a Yd11 transformer, the Wye side lags the delta side by 30° (or the Y side is at -30° with respect to the delta side)

If you are injecting at 180°,60°,-60° on the generator (delta) side, the angles on the Y side should be -30°,-150°,90° for a Yd11 Transformer.

I am not sure that the settings are correct for a Yd11.

 

[rayas91]

Friends ,Thank you for your interest and your time.

I called engineering center many times,They said settings are correct and said "We make these settins always,no problem".Bu I dont trust them, of course.

Then...

I disable the diffferential protection .

I energized the Step-up Tranf and Unit Auxiliary Transf. .Then I put some loads.

Finally , I saw the angle differences,The settings was not correct as you said.

I fixed settings as me and you know, like " gen : 0 , hv : -30 , uat : -30 " respectively.

Thank you again.

 

[DiscoP]

Thanks for the update Rayas - a primary test is always a pretty reliable second opinion !

 

[rayas91]

Yes, excatly.Thanks to all guys who helped me.

 

[waross]

This may clear up the misunderstanding as to vector group nptation;
From;

http://electrical-engineering-portal.com/understanding-vector-group-transformer-1

Winding connection designations
First Symbol: for High Voltage: Always capital letters.
D=Delta, S=Star, Z=Interconnected star, N=Neutral
Second Symbol: for Low voltage: Always Small letters.
d=Delta, s=Star, z=Interconnected star, n=Neutral.
Third Symbol: Phase displacement expressed as the clock hour number (1,6,11)

Example – Dyn11

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[davidbeach]

Typically Y/y for wye rather than S/s for star; per the example given. ;-)

 

[waross]

Agreed David. Thank you for heading off another potential misunderstanding.
The points that I was making was that the high voltage winding is used rather than the primary winding, and the convention concerning capitalization.

Bill
--------------------
"Why not the best?"
Jimmy Carter