PSEG

Many utilities ran systems like that--some do 24.9 and 12470, while CL&P does 13.8 and 27.6. 26.4 is a more uncommon voltage though--never saw anybody but PSE&G run it.

Interesting information...thank you.

That is true but I found for many utilities there's more to it. The amount of load on the customer's end often counts as a voltage determinant as well. The higher the load, the more wattage needed and that can often mean higher voltage to compensate for higher current and the cost of larger conductors kind of like with increased heat resistence on long distances. I've also found some utilities favor 12-13kv as a standard regardless of distance and use more varying conductors sizes while other utilities often favor higher voltages such as 22.8-27.8kv like in crowded areas in Ontario to make varying load fluctuations or future loads less of a concern. Obviously the disadvantage of lower distribution voltages is larger-expensive conductors are needed while with higher voltages larger more expensive insulators and safety measures are needed.