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?