Do corner-grounded deltas exist outside of USA? If yes, where?
Where do you find information about this? Is there an IEC standard that dictates which transformers exist where?
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\$\begingroup\$ It wouldn't be an IEC standard; that would be the realm of national standards. \$\endgroup\$– HearthCommented Sep 6, 2023 at 15:19
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\$\begingroup\$ Oh OK, is there a summary of the national standards somewhere? I'm interested to understand how people manufacture equipment without having this data? \$\endgroup\$– user1047455Commented Sep 6, 2023 at 23:49
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\$\begingroup\$ I hope someone can provide ab answer on the European and Asian situation \$\endgroup\$– user1047455Commented Sep 6, 2023 at 23:51
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2 Answers
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By my experience, tertiary windings with on single point grounded are used all around the world. IEEE C57.158-2017 provides recommendations for such practice (if you look to the participants list, there people from many different countries).
I live in Brazil, and I can say that here it's almost omnipresent in the entire transmission system.
Note: this single point grounded deltas are used in medium voltage (like between 15 and 36kV). Regarding low voltage (i.e., <1kV), I never saw any of it here.
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1\$\begingroup\$ Just need to make sure the bushings on the 2 ungrounded corners can handle the ph-ph voltage magnitude continuously. \$\endgroup\$ Commented Sep 7, 2023 at 16:59
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\$\begingroup\$ OK, but this tertiary winding, I guess, won't impact the distribution network. Correct? Or are the distribution networks in Brazil also could be/maybe corner-grounded? I know Brazil basically has both American and European electrical systems. \$\endgroup\$ Commented Sep 8, 2023 at 4:33
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\$\begingroup\$ You are right. Very few distribution systems in delta in Brazil (there is some like in 36kV). But the vast marjority is grounded wye. \$\endgroup\$ Commented Sep 8, 2023 at 9:41
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\$\begingroup\$ Corner grounding will have zero impact on the bank behavior in regards to load/fault current. If another winding on the core is wye-grounded, the delta facilitates zero-sequence current flow in the wye. Corner grounding has no effect here. \$\endgroup\$ Commented Sep 8, 2023 at 16:53
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I know by experience it exists in Uruguay, and I can even say they sometimes even change the grounding point. I noticed it once when mounting an LED lamp in the backyard. Depending on which wire I chose as neutral (which isn't defined) you had a small glow when the lamp was off or not. I, of course, chose the wiring so that it didn't glow. A few months later, the operator changed the grounding and it started glowing. You have quite a variation on the electrical codes across countries. In Argentina, for example, they use star, and the neutral is tied to ground, therefore if you get a 3 phase machine the neutral will usually be connected to ground. If you plug that in in a country that doesn't do that it will trip the differential.
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1\$\begingroup\$ OK, thanks for sharing the south American experience. \$\endgroup\$ Commented Sep 6, 2023 at 23:50