Electrical insulation is used in the stator and rotor windings of motors and generators, as well as in the stator core. Degradation of the insulation is a main cause of motor and generator failure, and is one of the main factors which determines the remaining life of such machines. The goal of this project was to establish the present state-of-the-art in assessing the remaining life of motor and generator insulation, and to develop improved methods for determining remaining life. The ability of existing electrical tests to determine remaining life was determined in extensive test on five stator windings. These conventional tests were found to be ineffective in determining remaining life. However, these tests, if trended over time, and combined with other background information, can be used to asses the insulation condition (i.e., fitness for service). the 300 page Handbook to Assess the Insulation Condition of Large Rotating Machines'' was published by EPRI in 1990 to help utility maintenance personnel in assessing condition. IN the absence of diagnostic tests which predict remaining life, several new monitors were developed which provide better information on insulation condition. Improved vibration monitoring, rotor temperature monitoring, as well as several new monitors for motor insulation weremore » developed. Prototypes of these new monitors were installed on operating motors and generators. Four of the new monitors appear to provide very useful information on insulation condition. To estimate remaining life, a probabilistic model was formulated which combines information from monitors, diagnostic tests, the relationship between mechanical, thermal and electrical stress and life. The model is very preliminary, but it does provide a realistic means of estimating the remaining life of machine insulation systems.« less