Transformer Vector 2

[foxhoundme]

what is meant by -Ydn1? The transformer is an oil filled design - 7100kVA with LV = 800V Delta with 45kVBIL and HV = 26000V Wye with 150kVBIL and an ESS (electro-static shield) grounded.

 

[ScottyUK]

Break it down into elements.

Y - star or wye connected primary
d - delta connected secondary
n - externally available neutral. In this position and lower case it denotes a secondary neutral which seems odd. YNd1 would makem more sense.
1 - voltage on the secondary 'a' terminal leads the voltage on the primary 'A' terminal by 30° phase shift.

The shield is to reduce the common-mode coupling of impulses on the primary through to the secondary.

 

[prc]

In stead of primary and secondary,let us use HV &LV. In a generator transformer, primary will be LV and secondary will be HV.As Scotty said, it should be YNd1 or Dyn11 etc.

 

[ScottyUK]

Good point prc, this could be a GSU transformer with that winding configuration. HV and LV makes more sense.

 

[foxhoundme]

Thank you prc and ScottyUK, this unit will be connected to a generator application, however the vector is the point I am having problems with and yes I understand the vector elements. But its the nameplate and the description that is causing me to scratch my head and wonder what the engineer was thinking - the engineer responded and stated the transformer will have a (negative)-Ydn1, the HV neutral will be internally isolated and will not be brought out. Can either of you tell me if the vector (-Ydn1) he is suggesting is correct? Am I correct to say it should be Yd11 instead of (-Ynd1)? I did not realize you could construct a vector with a negative sign. Thanks for your input.

 

[ScottyUK]

I think he's probably alluding to the fact that the 'A' voltage will lag the 'a' voltage and is describing that as 'negative'. The generator won't care because it will synchronise across whichever breaker (high or low side) is designated for the duty and the machine's phase relationship to the larger system isn't of direct consequence to its operation. There may be customary vector groups used for GSU transformers in your country but they are almost certainly arbitrary rather than a practical necessity.

 

[ShooterBoter]

"1 - voltage on the secondary 'a' terminal leads the voltage on the primary 'A' terminal by 30° phase shift."
Shouldn't it be "lags" instead of "leads"? The HV 'A' phase leads the LV 'a' phase.

 

[ScottyUK]

Yes, you're right. No excuses.