Environmental condition such as pollution and humidity can influence on expected performance of insulators and change their electrical behavior. Pollution also reduces the efficiency of the insulators and increases the possibility of flashover occurrence which consequently results in transmission line outage. Therefore, forecasting the flashover and detecting the critical conditions are very important. This paper proposes a novel method for critical conditions detection and consequently preventing from flashover in porcelain and glass insulators by employing leakage current analysis Pollution also reduces the efficiency of the insulators and increases the possibility of flashover occurrence which consequently results in transmission line outage. Therefore, forecasting the flashover and detecting the critical conditions are very important