The voltage-lifetime characteristics of the new epoxy resin system, diglycidyl ether of bisphenol A (DGEBA)/4,4'-methylene dianiline (MDA)/succinonitrile (SN), have been investigated by using non-homogeneous electrode geometry. The lifetime dependence of the applied electric field well followed the empirical V(n)t=const model. The lifetime factors at 25, 70 and 100 degrees C were 5.128, 7.533 and 14.494, respectively. The dielectric breakdown mechanism at 25 degrees C was changed around 14kV. At high temperature, the thermal stress dominated the lifetime and at the low thermal stress, the thermal decomposition and distortion by electro-mechanical stress governed the dielectric breakdown under high electric field.