Abstract In this paper, the simplified algorithm for prediction of insulation status of high-voltage asynchronous machine stator coil is presented. It also pointed out the simple way of determining the lifetime coefficient of the stator insulation of high-voltage asynchronous machine. The presented methods are based on the law on the increasing probability of electrical discharge that arises from the rule of independent probabilities multiplication. The experiments were performed on samples taken from new and used windings. The experiments were also carried out on entirely new and used windings. The statistical processing of the experimental results was with high statistical reliability, and a combined measurement uncertainty was satisfactory. The satisfactory results have been obtained that enable replacing the expensive and time-consuming testing in the construction phase of the high-voltage asynchronous machine, as well as the testing during the machine's operation, with much shorter and economical tests, while the reliability of the results remains unchanged.