When I was younger, I didn't have the $$$ for isolation transformers. I knew that the TV had a hot chassis and my scope had a power transformer that would allow it to reference at the TV chassis ground, if I lifted the scope earth ground. So I removed the three of us from proximity to Earth. Not as dramatic as a guy in a Faraday Suit, hopping off a helicopter, to work on 500KV lines, but the same general idea.
Joe
Really, I removed the scope's and my reference to Earth and the TV chassis shifted us negative WRT Earth.
