You may be able to force them to remove it from your property--but not necessarily from the easement area.
Generally speaking if the pad is on your lands you can force its removal.
However you may have a problem that it seems it has been there for over 30 years --and in NJ that may trigger adverse possessionin favor of power company--but its not quite that easy for power company.
1. There is case law in NJ that the adverse possession clock does not beging to run until the use is known by other side to be adverse--case involved a sign place a few feet in wrong place--but it was not discovered to be wrong until much later--later date counted NOT original date. You may need to be careful about when you discovered the wrong placement!
1.1 I assume you are accurate in description of easement as it is deeded and actual placement of pad --some dimensions in NJ can be wacky--two adjacent properties--one deed runs to center line of street--next one over runs from edge of 45' street ROW--so be sure of what you are reading.
2. There is a general rule that permission trumps adverse use--so if some prior owner gave permission to put it there then that trumps an adverse use claim and you may be able to simply revoke permission.
And in a way you sort of want to find out power company's reason it says pad is located there BEFORE you address fact or opinions you think you may have on your side.
You cannot prohibt them for using the easement area--if said use is otherwsie permissible--but if some other code say no transformers that close to roadway thay may be blocked to use that area by other rules--and generally since this is a problem created by power company it is not entitled to automatic relief by variance for a problem it brought upon itself. But I suggest you not get into second stage problems until you have secured removal of pad from wrong place in your front yard.
I know folks who have gotten poles removed from wrong place in NJ--but it requires a bit of attention to detail.
And you may want to get oral answers from transmission or maintenance engineering staff at power company by phone BEFORE some androids in right of way department put a lid on it if they discover an error by power firm.