Transformer Bypass

[apollo electric]

Opened up a transformer (277/120) and inside was a transformer bypass with 3 leads to primary, 3 leads to secondary. Never have seen this before was wondering if anyone has come across this before.

 

[blingbling4r]

I've heard of a transformer bypass circuit being used on utility transformers. Basically this alternate path is used for high speed communications (internet over power lines) since the high frequency of that data doesn't pass well through the transformer.