I'm still a bit skeptical- the voltage to remote earth has to be higher- though the odds of faster clearing do go up.
But for what design parameters? 34.5 kV can push more power further but also has a different design.
For a constant fault impedance, the higher kV will yield a higher minimum ground fault true enough. That is for a relatively large fault impedance. But the GPR scenario discussed is for bolted faults with normal source impedance.
My thought was that the conductor size and distance for either voltage would be designed to supply adequate power to a load without overdoing it. Also, for the higher voltage you would increase the source impedance at the station to keep the available fault from being too high. As such, my first thought was that when all is said and done you would wind up with a similar power supply profile at the load for either design and would thus have a similar result.
This may not be true but I did not feel like running a bunch of scenarios. It would take more than just changing the source voltage because the two would be designed differently.
To a degree though- I've found that at 12.47kv you are generally limited to 40-80MVA loading tops, 100-120MVA at 23kv, and at 34.5kv I've seen 200MVA and over.
Yes you can push more power from a single transformer at a higher voltage. But you can also have multiple transformers in a sub. I like about a 20-40 MVA unit. When the transformer gets too big, you may be better off to locate a new sub closer to a load center and spend less on large distribution.
You have to run the economics of large distribution lines vs building a new sub elsewhere. A large concentrated load may very well need 200 MVA in a small sq mile area but you could also invest too much in one substation and then spend a lot of distribution system cost getting that power out to remote load centers. Every system is different.
But how do we know this will always result in safe values of neutral to remote earth voltage?
At what Thevenin impedance?
Nothing is always safe. People demand electricity. They demand it at a reasonable cost. They demand it with reasonable safety. They demand it with reasonable reliability. There are a lot of demands and not all can be met perfectly at the same time. And not everyone defines reasonable the same way.
An example of one of the most dangerous things people demand is cars. Not always safe but we still allow them because people demand them. It is not a perfect world.