pt connection

[keyrose]

I have seen pt connection Delta/Delta and one leg of secondary is grounded.

What is the purpose of grounding one leg of secondary delta?

Can we ground one leg of primary too? I don't think so.

I have seen a lot of Delta/Delta power transformer and never seen secondary grounded. Can we ground one leg of secondary delta in power transformer too?

Is there any transformation ratio change with and without delta grounding ?

Can somebody explain me the purpose of delta grounding.


Kiroj

 

[scottf]

The purpose of the grounding of one leg of the delta secondary is to provide ground reference for the secondary windings. Without this ground reference, the secondary windings will float up in voltage primarily due to capacitive coupling between the primary and secondary windings.

Secondary windings for any type of instrument transformer should always have some reference to ground.

 

[busbar]

scottf hit the nail on the head, but ”corner grounded” delta or open-delta secondaries are also called out in ANSI/IEEE C57.13.3-1983 §2—IEEE Guide for the Grounding of Instrument Transformer Secondary Circuits and Cases.

 

[waross]

Four wire delta systems supplying 120:240V single phase along with 240V delta are possibly the most common 240V delta configuration for distribution transformers. The center tap of the 120:240V winding is always grounded.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[pwrengrds]

My training told me it was a matter of safety, in the event of a primary secondary short, grounding one phase of the secondary would insure a blown primary fuse. You don't want medium voltage on your secondary side.