The full wye-delta with a floating star point also has an issue.
During energization, there may be switching over-voltage transients.
I have seen one mitigation for this.
There were four fused cutouts at the transformer bank, the forth cutout for the star connection.
When a crew was working on the bank locally, they would instal a fuse to ground the wye point.
Then they could energize, phase by phase without transient over-voltages.
When the bank was energized, the neutral fuse would be removed and taken away with the crew.
I saw one such arrangement about 12 years ago.
I still regret not taking a picture.
Another case.
In a micro grid, (about 5000 subscribers) there were several wye-delta banks.
The burn-out of customers refrigerators was frequent.
When I got involved, it took several years but I eventually had the wye-delta banks converted to wye-wye.
I had been away, but I was back in the area and the System Manager asked me to do a walk-around of the system.
Low and behold, a new wye-delta bank.
"I thought that we had agreed that that connection would never be used again."
"Yes but that customer is owned by the National Government and they are too big for us to argue with."
"How long has it been since a customer has complained about a burned out refrigerator?"
"Not for years now."
"Do you want to go back to those days?"
"No way. That was terrible."
"Well we have to do something."
Solution:
Transformer bank capacity: 150 KVA.
Three phase load: 17 KVA.
Single phase load: Less than 17 KVA.
For those who may not be familiar with fused cut-outs;
The fuse holder has a tiggle on the bottom end.
The toggle is held in position by the replaceable fuse link.
When the fuse blows it releases the toggle and when the toggle collapses the fuse holder swings down 180 degrees and is readily visible as a blown fuse.
We removed the fuse link from a fuse holded and tack welded the toggle in position.
When we installed the dummy fuse holder, it looked like a full delta but was actually an open delta.
The customer never knew.
Bill
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Ohm's law
Not just a good idea;
It's the LAW!