Does a triple divorce take place if wudu is nullified during the 'Isha prayer, knowing that the condition was stated in the past tense and three years ago?

Your statement to your wife: "If I miss the 'Isha prayer again, then you are divorced by triple talaq" is considered a conditional divorce. The majority of scholars hold that divorce occurs upon the violation of the condition. However, some scholars, including Sheikh Ibn 'Uthaymeen, are of the view that conditional divorce is divided into three categories:

1. Pure condition: Divorce occurs in all cases (Example: "If the sun sets, you are divorced"). 2. Pure oath: Divorce does not occur, but an expiation for an oath (kaffarat yamin) is required (Example: "If you speak to Zayd, then my wife is divorced," intending to prevent oneself). 3. Ambiguous: It refers back to the intention of the one who made the condition (Example: "If you leave the house, you are divorced"). If he intended to effect a divorce, it occurs; if he intended prevention or encouragement, then an expiation for an oath is required.

Since you intended by conditioning the divorce to discipline yourself and encourage yourself to pray, the divorce has not occurred, and an expiation for an oath is required of you.