One upgrade method used by US utilities is to change, for example, 12kV circuits to 20.8kV with an added neutral span and larger insulators. Delta 3ø 12kV-primary transformer banks are changed to grounded-wye, and 12kV 1ø transformers are changed from ø-ø to ø-n.
Newer padmount transformers can then be specified with a non-loadbreak primary switch to swap between 12kV delta and 20.8kV wye.
