MV transformers with dual primary

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cpiper

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I'm working on a primary service conversion project and the client has requested that we specify a transformer that has the capability of operating at 12 KV primary voltage presently with the option of switching to 21Y/12 KV primary voltage if the utility converts their distribution network in the future. FYI - the secondary voltage is 480Y/277V and the kVA rating is 2000 kVA. Does anyone have any experience with this?
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
In the past I have quoted "re-connectible" primary transformers. But, they are very rare except in those parts of the world that are experiencing tremendous growth in the power distribution system. I have not seen one of these specified in decades, the small rural locations that could need these often just use (3) single phase transformers instead.
 

cpiper

Member
I've spoke to a transformer manufacturer and was told that I can specify a dual voltage delta-wye switch (Cooper, Square D, GE all have standard options). Initially, the switch will be in the delta position and the primary votlage will be 12 kV. In the future, if the utiltiy distibution system is upgraded, the switch will be in the wye position and the primary voltage will be 20.8 kV. Now the issue I need to be concerned with is potential ground fault problems with Y-Y connected transformers.
 

jrannis

Senior Member
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There is such a critter. I saw one yesterday. I think I have a pic of it too.
 
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