Since Scotty speaks of velocity balance variation, and probably isn't referring to the velocity of the ship (since they aren't going anywhere) but to transporters (because his report is all about repairing those), blssdwlf's idea that these wires transfer excess momentum between the transporter and the engines is a pretty fitting one.
Run this by me again. I don't understand the whole "transfer excess momentum" business. How would this be done? Why would this be important?
Also, the ship indeed is
moving as it's orbiting the planet. So the position of the landing party and the Enterprise
would be a constant variable. However, I guess now I have to ask what this whole "velocity balance" business is about. Mr. Scott mentions it as a factor when they are reintegrating the poodle-slug. I don't get the impression that they are beaming it to someplace and then bringing it back, but, rather, simply dematerializing it and rematerializing it, hopefully in one body. So, given that the only thing involved here is the one transporter pad, what velocity are we even talking about?