Transformer delta star

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

Theoretically trivial, but practically, I dunno..... unless the bushings were rated for 380kV in the first place.

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.

| 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 :-)