Delta power ditribution systems outside of North America 1

[jraef]

I have never worked outside of North America, but I was under the impression that we are, for the most part, the only ones who use delta power distribution systems, that "everywhere else they use wye (star) distribution"; in quotes because a former boss from England made that statement to me once during a discussion of symmetric vs asymmetric fault current, but I have no other direct knowledge.

This subject comes up a lot for me now because VFD manufacturers tend to have a lot of heartburn with delta power systems; some mfrs provide ways to disconnect any internal ground references but warn of potential dire consequences, others simply put it in their instructions that you cannot use them on delta sources at all and you must add drive isolation transformers ahead of them with a solidly grounded wye secondary. I would like corroboration of that old statement, which I took at face value so many years ago. Are delta power distribution systems common in the IEC based world?


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[Mbrooke]

IT is common (the norm) in Norway, and found in some Industrial plants through the world.

 

[WHiPCPL]

In Denmark;

Residential and some industrial installations use TT.

TN is found industrial applications, it was more or less exclusively used in the place I was an intern at.

IT is found in hospitals and ships, and other places where a 1st fault will not result in a fault clearing, until another fault happens.

 

[waross]

In a Central American Country, the standard was the disasterous wye:delta system.
The fuses changed with the elections.
Much of the country ran on inadvertent open delta transformer banks but not enough..
AS you drove around you would see many transformer banks with one fused cu-out hanging down and the loads happily running open delta.
Then would come an election and many of the politically appointed engineers at the National Energy Company would be replaced.
Under the new supervision, the crews would be out replacing the third fuse in the transformer banks.
Each time a fuse opened it was often replaced with a higher rating.
Then transformers would start failing due to excess circulating currents.
After an election it took about 6 to 8 months for things to get back to normal.
SO, when asking about delta systems I have to also ask:
Delta:delta,
Star:delta with floating primary star point,
or
Star:delta with a four wire primary connection?
TT, TN IT describe grounding systems, not transformer connections.
Delta systems may be asymmetrically grounded, corner grounded, grounded with a grounding transformer or ungrounded.
Wye systems may be ungrounded, (IT).
Bill
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"Why not the best?"
Jimmy Carter