tiny power poles have area = 3x3 and reach = 3 which makes it a bit difficult to cover an accu from two sides without the power poles connecting. to achieve that one side needs to use the tiny poles and the other uses normal poles.
EDIT: when i (below) wrote about zigzag setup of powerpoles so that they don't connect, why didn't i do that for the tiny poles too? two non-connecting columns of tiny poles have space for one column of 2x2 accus between them! thus i don't need anything better than those tiny poles when i only have a few (maybe 3) accus for some local setup :-)
just "eyeballing": maybe area=5x5 (same as normal poles) would be best, but keeping reach low enough to not connect "to the other side" (reach=4, but maybe even reach=5 would be useful when placing poles in zigzag instead of a grid). to cover a large area with many accus, maybe even a modified substation would be useful with normal area=18x18 and reduced reach of 9 only. that would allow a "zigzag" layout of substations which don't connect to any other substations, but having a line of medium power poles behind them which match exactly their distances. result would be an area 8 wide (4 rows or columns of accus) between the substations and easy symmetrical connections to medium poles behind them. that would allow to easily have more than 2x16 accus for each pair of modified substations in such a staggered setup (for use with bigger power plants)
With 2250kW discharge you should only need 16 to cover a full 40 steam engine set up.
I didn't use accus to connect bigger power plants yet, but had several small selfsufficient greenhouse setups which produced a surplus of either lots of wood (or coal), or could convert that to power. since it was helpful to get power from the main factory while bootstrapping the setup and absolutely necessary to keep the setups selfsufficient (even if that meant that there is not enough power for lasers in the main base :-) i needed those "powernet separators" with a dimendion of only 2, 4 or 6 MW for each setup. up to 20 normal accus for each setup took too much space and 1, 2 or 3 of your accus would be just right. for the bigger setups, 1 accu for each group of 1 boiler and 2 steam engines doesn't sound bad (2250 > 1800) and the capacity almost doesn't matter when it is used only to forward the energy.
while writing this, i did a test setup of a power plant and it was really easy: i even didn't have to modify my blueprint, but only put one of your accus next to each steam engine in the second row, and insert a tiny pole in the gap between my steam engines to also electrically connect the accus. this will be my new default blueprint :-)
i had tried using a transformer mod, but if the main factory needed power they started drawing too much power from my selfsufficient setups and "starved" them :-( being almost vanilla with only your slightly modified accus and slightly modified power poles will help a lot in the future, although it will not be possible to use it for some kind of "electrical main bus" that is fed by many selfsufficient small power plants and forward the energy to several groups of smelters, machines, lasers, etc.
one additional suggestion: i just built the test setup with creative mode. but it would be nice if a similar setup also could be built in early vanilla games, not requiring blue science, oil industry and batteries. maybe you could add another lower tier of your accus with really low capacity, eg working like big capacitors which can be built from mostly only some separating materials (a few wood boards) and (lots of) copper plates. they could have max transfer of 900+ kW (one for each single steam engine) and almost no capacity at all (just enough to buffer lag and rounding errors in factorios power calculations, maybe 900+ kJ for one second of max transfer), or maybe even half those values to match KS power's burner generator (450 kW, half the efficiency of boilers).
