HOXO connection and switch

[PowerDawg]

We recently received a re-manufactured 3 phase transformer with a HOXO connection on the secondary side. (The transformer is a 24940Y/14400 480Y/277 1500kVA transformer) I know that a lot of transformers have a removable link to separate the HO and XO connection. This particular transformer has an external switch to open or close the HOXO connection. My question is, under what circumstances would you want the HO and XO connection open?

 

[DTR2011]

testing the transformer in the field

 

[waross]

A high impedance grounding system on one side and a low impedance grounding system on the other side. Or, both sides high impedance grounded but with different impedance values.

Bill
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"Why not the best?"
Jimmy Carter

 

[davidbeach]

That works Bill if there are actually H0 and X0 bushings. From the description it sounds like a transformer where there is only one place to terminate a '0' conductor. Given that, it is probably also a transformer with graded insulation and must be solidly grounded on both sides to meet the insulation requirements. As DTR2011 says, that switch is just for testing purposes and should be closed any time the transformer is in use.

 

[waross]

Thanks David.

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