# Transformer delta star

Hello everyone,
Does someone know something of a transformer that prior is used a step down delta-star 220kV/110kV which later on could be used as a Yy
380kV/110kV transformer.
Regards
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What's to know?
Reconnecting the high voltage side from delta to star raises the line-line voltage by the square root of 3. So 220kV * 1.73 = 380 kV. Not much of a question there.
Or are you wondering why delta versus star has a factor of sqrt(3) different? That's some basic three-phase electrical theory. Do some vector math and it 'jumps right out' at you.
daestrom
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On Wed, 01 Nov 2006 21:05:42 GMT, "daestrom"

Theoretically trivial, but practically, I dunno..... unless the bushings were rated for 380kV in the first place.
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Yep, bushings, and also the internal insulation.
Unless there is a tertiary winding, the zero sequence source will now become the 380kV system. AFAIK it's normal to provide a zero sequence source in a substation, but I'm no utility engineer.
May I suggest that if you don't know what you are doing, you should be doing ANYTHING with 220kV or 380kV utility systems.
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| May I suggest that if you don't know what you are doing, you should be doing | ANYTHING with 220kV or 380kV utility systems.
Just let the Darwin Effect run its course :-)
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|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |