Generator Transformer vector group

[gce1991]

we have a power system with 132 kV/11 KV YYnd0 , 20 MVA Transformer and two TG's 12 MW and 16 MW connected to 11 kV with resistance earthing 400 A thro NGR.

Now we want to add additional 22 MW TG at the 11 kv level.In order to isolate the earthing of new TG it is proposed high impedence earthing thro NGT/NGR and an Isolation transformer 11 kV/11 KV with Ddo .
There are additional proposal to consider the Generator transformer with Dyn11 earthing , in this case the new TG -22 MW will supply the entire power hence the earthing is needed at the 11 KV level. Now is it possible to synchronise the new TG 22 MW with Gen. Transformer, Dyn 11 vector group with the grid transformer 20 MVA YYnd0. There is a argument that the generator source is 0 degree vector so it is possible to synchronise with the grid.

ESW,

 

[Skogsgurra]

The new 22 MW generator is free to run at whatever angle it wants - isn't it? I don't see what the problem should be?

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[ScottyUK]

Agree with Gunnar, unless there is a requirement to synchronise the generator's auxiliary services with an external source.

 

[gce1991]

Thank You Gunnar and Scotty for your time and reply.

ESW,

 

[prc]

Normally Generator transformers are of Yd11 or 1 (ie HV star coinnected) Why in this case Dy11 is considered? 400A NGR is for 20 MVA transformer or generator?

"In order to isolate the earthing of new TG " From operational angle, why it is required?

 

[davidbeach]

Standard for wye-delta is that the low-side lags the high-side by 30 degrees. Generator should be on the delta side, other side should be grounded wye. Piece of cake.

 

[gce1991]

Generator transformer is delta connected in Generator side and Star (Y11) connected on the switchgear side,as per suggestion Y11 can be made Y1, 400A NGR is for Transformer high voltage side(Star). The other two existing TG-1 and 2 are permanently connected thro NGR, 400A. hence for the new TG it is decided to isolate the earthing thro the 11Kv/11KV generator transformer and earth the generator thro high impedence earthing by NGT/NGR.

ESW,