Transformer vector groups
Transformer vector groups
(OP)
Hi,
We have 4 off 132/11kV YNd1 transformers on site but are replacing two of them due to age. We witnessed the factory tests last week but were told that a request had been made to chenge the vector group of the 2 new transformers to YNd11. Apparently this is because there has been a c**k up on the design and the HV connection to the HV bushings is now to be BYR rather than the conventional RYB (in old money). Can anyone explain how changing the vector group to YNd11 and then changing the HV phasing to BYR convert the output of the transformer back to the require phase rotation?
We have 4 off 132/11kV YNd1 transformers on site but are replacing two of them due to age. We witnessed the factory tests last week but were told that a request had been made to chenge the vector group of the 2 new transformers to YNd11. Apparently this is because there has been a c**k up on the design and the HV connection to the HV bushings is now to be BYR rather than the conventional RYB (in old money). Can anyone explain how changing the vector group to YNd11 and then changing the HV phasing to BYR convert the output of the transformer back to the require phase rotation?






RE: Transformer vector groups
RE: Transformer vector groups
RE: Transformer vector groups
RE: Transformer vector groups
RE: Transformer vector groups
RE: Transformer vector groups
RE: Transformer vector groups
Third times a charm.
RE: Transformer vector groups
RE: Transformer vector groups
I don't understand your diagrams. The Winding 1 voltage should be in phase with Winding 4. On a Dyn1 transformer, the secondary line-to-neutral voltage r-n lags the primary line-to-neutral voltage R-n. Your diagram shows r-n in phase with R-n.
RE: Transformer vector groups
RE: Transformer vector groups
I don't understand your diagrams.
jghrist, the only possible reason I can see for you not understanding the diagrams is because they were a complete cock-up, incorrect, wrong, mistaken and erroneous.
*please insert an embarrassed emoticon at this point*
I can only throw myself on the mercy of the court and claim that I was arguing with the wife, yelling at the kids, kicking the dog and drinking way too much beer at the time.
I have inserted a changed drawing.
RE: Transformer vector groups
Is it common for transformers with varying vector groups to be connected in parallel and the external connections changed to compensate for this? I am not in a utilities industry but even after talking to other more experienced power engineers they have never come across this either. I always thought the basics for transformers in parallel were: same vector group, similar/same impedance, similar/same rating etc etc.
RE: Transformer vector groups
RE: Transformer vector groups
A hint: the transformer itself knows nothing about vector groups. The nameplate shows what the factory thought as the most probable vector group, but any Dy or Yd transformer can have any of the odd numbered vector groups. What is important is that you see how it works. Draw out the diagrams and thoroughly understand it for yourself. Don't proceed further based on anything from the internet, but know for yourself that it is correct.