Step-up transformer vector group
Step-up transformer vector group
(OP)
Hi everyone,
I am trying to finalize the specification of a step-up transformer but I can't find a lot of information about vector group.
The existing step-down transformers of the installation are Dyn11 type. After a discussion with a transformer manufacturer his proposal was YNd11.
A rough description of the installation is [gen-set 0.4kV] - [step-up transformer 0.4/20kV] - [20kV line] - [step-down transformer 20/0.4kV] - [loads].
Thanks
I am trying to finalize the specification of a step-up transformer but I can't find a lot of information about vector group.
The existing step-down transformers of the installation are Dyn11 type. After a discussion with a transformer manufacturer his proposal was YNd11.
A rough description of the installation is [gen-set 0.4kV] - [step-up transformer 0.4/20kV] - [20kV line] - [step-down transformer 20/0.4kV] - [loads].
Thanks






RE: Step-up transformer vector group
RE: Step-up transformer vector group
Perhaps the question was not so clear. So, is there any regulation (or other tech restriction) which determine to use an exact vector group for the step-up trafo if the vector group of the step-down trafo (Dyn11) is known ?
RE: Step-up transformer vector group
- Are there any changeover supplies at the other end? If so, the phase shift degrees will need to be carefully coordinated to avoid mismatch of phasing between the two supplies at the receiving end
- Ground fault protection philosophy will also dictate the type of vector grouping. In the arrangement you have mentioned (having a YNd11), I presume the intention was to use the d11 for the 20kV side. If this is the case, grounding of the entire 20kV network is going to be challenging. You may need to consider corner point delta winding earthing or having earthing transformers installed. In my opinion, I would go with the 20kV side to be solidly or resistively earthed via an NER or NEX in which case a star winding is what I would prefer for the 20kV side
RE: Step-up transformer vector group
RE: Step-up transformer vector group
RE: Step-up transformer vector group
The generator itself doesn't know or care about the GSU vector group, but the GSU vector group may be of significance if the station and unit auxiliary supplies are required to operate in parallel for any reason.
RE: Step-up transformer vector group
thanks for your answer. Consequently which is your proposal for my simple case ?
RE: Step-up transformer vector group
RE: Step-up transformer vector group
With delta on LV side, any LG fault on HV will be seen as a LL fault on LV. Scotty, my understanding is, UK you follow YNd11 for GSUs always. My understanding wrong? In India, we follow UK practice except where US consultants are involved where we use YNd1.
RE: Step-up transformer vector group
There are few if any British generating plant manufacturers left, with the market now dominated by foreign companies - YNd1 isn't uncommon among the younger stations, especially those with North American links. I think the UK practice you refer to is that of the old CEGB, but now ownership of generation is fragmented there's no common standard. Dyn11 is the default vector group on the distribution system other than where 'unusual' types are required - typically star-star or star-interstar (zigzag) - for specific purposes.