My understanding was that most long distance transmission is high voltage DC anyway, so the frequency of interconnected grids should be irrelevant in that case
harmonization of grid standards is more than just frequency (it is mostly policy paperwork and the replacement of non-compliant equipment or the installation of conversion equipment) but you are correct high voltage DC is used for long distance power transmission. There are also details such as who is responsible for paying for what, where things are to be connected and various other bureaucratic details.
My understanding was that most long distance transmission is high voltage DC anyway, so the frequency of interconnected grids should be irrelevant in that case
harmonization of grid standards is more than just frequency (it is mostly policy paperwork and the replacement of non-compliant equipment or the installation of conversion equipment) but you are correct high voltage DC is used for long distance power transmission. There are also details such as who is responsible for paying for what, where things are to be connected and various other bureaucratic details.