Big electric pole and Substation have a limit of 5 connections (Didn't test small and medium poles). So the max is 1 power connection and 4 factories.

If you have 1 Substation connected with a Big electric pole and 4 factories, and then you try to place the 5th factory close to the substation, the substation will disconnect from the Big Electric Pole and none of the factories will have power, because the substation will not have power anymore.
https://imgur.com/cHMaDPt
https://imgur.com/iW3mPbM
If you have 5 factories, and place a Substation (that should get power from a Big Electric pole), the Substation will connect to the 5 factories, but will not connect to the Big Electric pole. In the end the substation and the factories don't get power.

If you have 6 factories, and place a Substation (that should get power from a Big Electric pole). Nothing will have power, and you get the error msg "Max of 5 connection reached." If you try to add more factories you keep getting the error.
https://imgur.com/OcB53Tg

In vanilla this is not a big problem, but if you're playing with mods that have bigger substations or powerpoles, the limit of 4 factories per substation is annoing.

This is intentional (-ish)

There is no way to increase the 5 connection limit on an electric pole from the modding api. You can try this yourself by dragging copper wire from a pole to 6 other poles.
I've added certain features to help alleviate this issue such as factory poles having priority over standard electric poles and unlimited power connection while doing recursion. The "max of 5 connections" error message is actually something I put into the game.

Until the mod api gets updated, this issue will remain.

I don't think it's actually that annoying to work with this, just place a new power pole for every group of 5 factory buildings.

Yeah, I understand. I just said annoying because in my current Pyanodon play through i'm using City Blocks with big electric poles that have 30x30 supply range. So I didn't need to place any poles. And when I go around placing my factories, sometimes the poles from the city block get disconnected, and sometimes this cause some place to stop getting power. Example:
https://imgur.com/xaH87so

And even if i place another pole, sometimes I still disconnect a City block wire. Something like this:
https://imgur.com/wpuHx2t

There is a way to add an option to disable the priority given to factory poles? I prefer adding a new factory and that it doesn't get power than having it breaking the already placed poles wires connections.

Anyway, tnks for the updates, great work :)

This seems reasonable to add. I'll put it in the next version

tnks :)