Joe of NJ, don't mean to step on your toes, just trying to de-myth manufactures claims. I know very well the difference between common and normal modes, and at a service entrance where you have a MBJ there is no common mode, or better said comon mode and normal are the same...
I have drawn it out and designed TVSS units for GE. Here is a link of some white papers I published that relates directly to common mode and normal mode.
http://www.geindustrial.com/products/applications/service_entry.pdf Here is a quote:
There are no real benefits of choosing a 7-mode TVSS (asuming 3-phase service) over a 4-mode TVSS at service entry when the N & G are bonded except for allowing a manufacture to quote "per phase" maximum surge current ratings.
The rest of the publications can be found at
http://www.geindustrial.com/cwc/pro...p;id=tvssoem&typeId=2&lang=en_US
