vector group selection of generator transformer

Vector group is important when you run the transformers in parallel. One of the criteria for parallel run of transformers is that the transformers to be run in parallel have to be of same vector group. If you do not have the intension to run it parallel with any other transformer, it should be ok to go for YNyn0.

- MS

dear msamad,

thankyou for the reply.Howevever i would like to know if we keep the vector symbol as YNd1 as per our past running plants,what will be the difference.Further this time we shall be using 11/132kv transformer capacity 20 MVA inplace of 11/66kv transformer as the nearest grid is of 132kv voltage level.i would be obliged if you can help me in designing single line diagram.Also i would like to inform you that generator star point shall be earthed through NGR.

jaswant.

No, you can not keep the same symbol.

The vector group of the new transformer should be the one that it is designed for (YNyn0 for your case). The symbols YNd1 and YNyn0 have different meanings. The meanings are:

YNd1 – High Voltage winding is Y connected with neutral terminal and Low Voltage winding is Delta connected. The phase angle of the LV winding lags the HV by 30 degrees.

YNyn0 - High Voltage winding is Y connected with neutral terminal and Low Voltage winding is Y connected with neutral terminal. The phase angle of the LV winding lags the HV by 0 degrees (both side voltage are in phase).

Note: The degree 'lags by' is calculated by 30 x the numbers at the end of vector group symbol . For example:

Dyn11 - High Voltage winding is Delta connected and Low Voltage winding is Y connected with neutral terminal. The phase angle of the LV winding lags the HV by 11x30 = 330 degrees (same as phase angle of the LV winding leads the HV by 360-11x30 = 30 degrees).

Dear MSamad San,

Can you explain what is the different between Dyn11 and Dy11?

As i understand HV side connected in Delta and LV side connected in star neutral grounding. but for Dy11 means there is not grounding? even though in single line diagram stated that it is drawn between star-delta connection.

Please advice.

Thanks.

Regards,

Michael (cristiano_michael_ronaldo83@yahoo.co.uk)

i want to know that what is the selection critrea for selecting either of YNd1, YNd0, YNd11 etc.pl give detail study releted to this.

I have one question, if I want to synchronized two (or more) generators through generator transformer that have different vector groups ( one has Ynd11 and the other has Ynd5) is it possible ? And when it is not possible do you have any technical explaination. Thanks and Regards,

Bambang.

I think it is not possible.

Paralleling is taking place on the secondary side of the transformer and not on the Generator side.Kindly recheck and confirm.

Yes, this is absolutly possible when the parallel operation is done only on the secondary side of the transformers

Peter

Kindly clarify,is it possible to synchronise two transformers when vector groups of the transformers are different.

In case the generators are paralleled through two separate stepup or stepdown transformers on the secondary side, the second generator will synch based on feedback info received through its own stepup or stepdown transformer. The reference info is transmitted from the secondary side bus. However, the generators must not be connected to a common bus on the primary side of the transformers and must be connected to the secondary side bus.

Vector groups of the two transformers in this case can be different.

Dear sir

Let me have your email id.

we are Electrical consultant can offer services if required.

Dear Sir ,

pls note my e-mail id

jaswantsarai@rediffmail.com

Dear Sir,

Can you please tell me what is the selection criteria of choosing vector group of various transformers like station, unit auxiliary & generator transformers in power plants, what is the meaning of '11' , '1' in Dyn11, Ynd1, on what basis we choose these angles.

Dear Mr.Jaswant,

We cannot decide the Vector Group unilaterally if the Transformer is NOT independantly connected to load - as an example, Captive load wit in a Factory.

hen the Power is to exported to the Grid, or Power is to be supplied where already a transformer is in service - compulsorily the Vector Group is to be MATCHED.

DHAYANANDHAN.S