The long-term behavior of solid electrical insulation is influenced by the nature and the magnitude of applied stresses. Much work has been done over the years to model and understand insulation degradation under single and combined electric and thermal stresses. However, efforts aimed at including mechanical stress as an additional interactive aging term in the existing models appear to be scanty. In the present work, the authors describe experimental methods for acquisition and analysis of insulation failure data when fatigue stresses, due to vibration, are present with electric and thermal stresses. An empirical model, based essentially on an Eyring relation, together with a fatigue crack propagation approach (in line with Miner's cumulative damage model) has been presented. Attempts have been made to verify this model experimentally.
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