11/3.3kV Dy11 transformer implies no neutral on LV side but neutral connection shown in vector diag.

[Callum5593]

Hi all,

As above, I have an 11/3.3kV transformer, with the nameplate showing a Dy11 vector group. However, the vector diagram shown at the bottom of the nameplate shows a neutral connection - so I'm usure if a neutral is present or not.

In this case, I'm doing a protection study for the site, I'm inclined to think it's the latter (there is a neutral connection), as the 3.3kV incomer is fitted with a standard earth-fault relay, as are the feeder circuits. I can't understand why the nameplate would show both though. Image attached.

Thanks

 

[jghrist]

A wye winding has a neutral point, inherent in the construction of the winding and the definition of "wye connected". It may or may not be grounded or connected to anything.

 

[stevenal]

I see no inconsistency in the nameplate. DY means the HV 11 kV winding is delta connected and the LV 6.6 kV winding is wye connected with a neutral terminal. Perhaps I don't understand the question here.

I fail to see how you get 11 kV out with only 3.3 kV in. The deenergized tap changer only allows a change of 5%.

 

[waross]

As above, I have an 11/3.3kV transformer,

You have posted the nameplate of an 11/6.6kV transformer and are asking about an 11/3.3kV transformer.
3.3kV incomer Implies a supply voltage of 3.3kV. Is that supplied to the 11kV winding or to the 6.6kV winding?
The nameplate posted shows a transformer with voltages of 11kV, 6.6kV and a voltage to neutral of 3.8kkV.
The transformer depicted by the nameplate has a neutral on the 6.6kV side, designated "n".
You have confused all of us.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[RRaghunath]

Dy11 doesn't imply that there is no neutral on y side.
It only implies that the neutral is not available externally, maybe isolated or earthed but inside the tank.
Check with the client what is their practice / what is actually done. I expect the plant SLD to indicate the same (hope you have one from the client).

 

[Parchie]

The nameplate is fine. The mere classification Dy11 tells you that there is no neutral connection. Otherwise you would see Dyn11.

 

[stevenal]

Except there is a neutral terminal, labelled n in the winding diagram.

 

[waross]

Conventions change over time.
Definitions change over time.
Conventions are not always applied universally.
I saw a convention that used the "n" to denote a factory grounded wye connection. (I am watching for a second confirmation of that.)
I remember when electricity flowed from negative to positive.
I was in a class being taught the "Right Hand Rule" to determine the polarity of an electromagnet.
We were instructed to use our left hands when implementing the "Right Hand Rule".
Contrary to some fears, the whole world did not shudder when the flow of electricity was abruptly changed from negative to positive back to positive to negative.
So we have a 57 year old nameplate showing a neutral terminal and what appears to be internal CT windings.
The CTs won't be effective without a neutral connection or grounding.
The issue is not a lack of a neutral, it is lack of an "n".
It is what it is.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!