I think you would need to be in a low priority queue set on like a 30 minute wait before you are considered for a perma ban.... My friend had one up to 20 when he had bad internet so that was a fun 5 game run.
When you think about your bad internet consider what happens to your team after it goes out. The game is now a 4v5 which is a major disadvantage which the jungler needs to compensate for unless the bot lane wants to solo. Having anyone dc from a game is almost a guaranteed loss and makes the game experience much worse for the players on your team. I know it sounds steep receiving any ban for just not having good internet but if your internet is not going to be stable enough to maintain connection for the sake of your teammates then league is not a game that time should be invested in.
That being said you did not really describe how often this happens. If this happens like maybe 2-3 times out of like 25 games then I would not worry but if every other game you are disconnecting or experiences some bad latency then you should probably look for games with shorter average play times than league.