ECN Forum Forums Photo Discussion Forums Photos for General Discussion Primaries of pole mounted transformers

I'm not an electrician, but I think most residential distribution systems today are wye, with a multi-grounded neutral common to the primary and secondary. The primaries are connected line-to-neutral.

Most single-phase aerial distribution transformers have a single primary bushing, with the other end of the primary winding internally bonded to the transformer case and the secondary neutral. But I occasionally see a two-bushing transformer, where both ends of the primary are brought out to bushings. This type of transformer can be used on either delta systems (connected line-to-line) or wye systems (where one of the primary terminals is externally connected to the neutral).

I think residential delta distribution was much more common in the past.