Multi-Factor Aging of Insulation Systems - Infinite Sequential Stressing Method -

In substituting sequential stress aging for simultaneous multi-factor aging, the interactions between the factors of influence should be expressed in each experimental equation for single-factor aging as a change in the coefficients with time of aging. Then, if all single-factor aging characteristics can be confirmed experimentally, the characteristic equation for multi-factor aging can be derived as that for infinite sequential stress aging. For mica-epoxy insulation systems, since the values of n in the inverse power law and thermal aging rate constant usually remain unchanged during aging, the characteristic equation thus derived can be expressed as an analytical form. Mechanical aging of mica-epoxy systems due to repeated bending can be considered as a combination of uniform thermal aging and local voltage aging. Combined thermal, voltage, and mechanical stress aging can be replaced by infinite sequential thermal, voltage, uniform mechanical, and local mechanical stress aging.