Well, of course, living in Australia, I have no knowledge of FERC or it's codes, but a lot of these situations are best solved by just looking at the basic situation and what is wanted, - as an example, I sold an 80 kW wind turbine to a High School in Victoria, a town called Murtoa, and the head of the Physics department had convinced the School, (and since a fast friend), but when they got the thing installed, - such a time and work.. they could not work out how to install the wind turbine, (3 phase) to the school Main circuit board, (3 phase), - the electrical engineer who designed the board, - no idea, the electricians who built the board, - no idea, - they all knew that the Wind turbine would be supplying the school and there were no grants, so it was obvious to me that the wind turbine had to be connected between the Mains Meter and the School network, - still no idea, so I requested a picture of the board, - high definition, and looked at it, - there the meter, there the terminal blocks for each phase, leading off to the various buildings, connect it there, those three blocks, earth is common. - so simple, but people are afraid of new, whatever, it worked fine.
So, you break it down, does the new HVDC contribute to the substation's capacity? if yes, (probably at a guess), then it increases Capacity, so Capital, or if not, then it is just maintenance, ie Expense.
The next bit is dependant on that you are dealing with a Bureaucracy, so if they fund Expense, but not capacity, you can probably show you need no more capacity, so it is expense, but if you need more power, it is Capital, - easy peasy.
Cheers, Geoff Thomas, Advanced Wind Technologies, Malanda, Qld, Australia.