Sequence Diagram For a Transformer

[jaus tail]

Homework Statement

I think two diagrams are wrong here. I've marked in red.[/B]

Homework Equations

Do you also think the 2 diagrams are wrong? I think for 1st red circle, at delta-- the a1 switch should be open
whereas for second red circle at star grounded-- the a1 switch should be closed.

The Attempt at a Solution

I found this in book and am not sure if book is right or wrong.

 

[magoo]

First of all, this should be titled as zero sequence diagrams for a transformer.

You are correct for diagrams #5 and #6. One way to determine this is to examine what you get when you perform a short circuit test with zero sequence voltage applied.

 

[jaus tail]

One way to determine this is to examine what you get when you perform a short circuit test with zero sequence voltage applied.

I don't know this method. I just remembered the formula. If there is ground in star the connect series switch. If there is delta then connect shunt switch.