Composite insulating materials have their important place in high-voltage insulating technology. The quality and high reliability of electrical devices is much affected by the curing level of these materials. Curing level is quantified by so-called degree of conversion and there are several possibilities how to determine this degree in practice. Attention is given mainly to kinetic analysis based techniques. Kinetic analysis use specific mathematic models, which work on the basis of Arrhenius law (kinetic analysis of thermal stability, isothermal kinetic analysis, Borchardt and Daniels kinetic analysis). The main objective is to compare results of selected methods; these data were subsequently verified via residual enthalpy measurement. Two composites (insulating tapes with different curing agent composed of glass fabric, mica and epoxy binder) were examined. The measurement carried out on simultaneous thermal analysis (STA), which allows the simultaneous measuring by differential scanning calorimetry (DSC) and thermogravimetry (TGA). Obtained results highly refer to advantages and disadvantages of selected methods.