I can't help you very much, but I found out that it's a very congested grid.
Some high tension power lines are located on U.S. Geological survey maps, and maybe some of these are available from the DEP database.
Many lines criss cross state lands and forests, especially over ridges.
If you have an idea of the area that you are most interested in, and can identify some of the closer power plants, then you might be able to follow some of the major lines that way.
There's the Maromas power plant in Middletown on the CT River, with some lines emanating from there.
There's the Hartford Generating Station on the CT River in Hartford, and many others too.
There's some trash to energy plants generating power too, one is in Bristol, and there is another one in Hartford.
Maybe the DPUC (CT Dept. of Public Utility Control) can help you since they are the regulatory agency for the ongoing power line rebuilding project going on in CT, one line which is from Middletown to Norwalk, another was from Bethel to Norwalk.
Power is fed into the grid from as far away as Quebec (Hydro-Quebec).
From the CL&P website:
CONVEX - The Connecticut Valley Electric Exchange
ISO New England - ISO New England Inc.
I found a little bit of information by Googling "Connecticut Power Grid".
This local agency might have experts who can help:
Connecticut Resources
Connecticut Department of Public Utility Control welcomes you.