>If used in succession with other protection moves, its success rate is cut to 33% of what it was, working cumulatively the more it's used. This will prevent damage and effects of almost all possible attacks that would be inflicted upon the user.
Bulbapedia for some reason doesn't have this. But this is right because even PS! Uses this description.
>This move has a 1/X chance of being successful, where X starts at 1 and triples each time the move is successfully used.
And using 3 times in a row the chance for it to fail is 1/9 which is 11.11%