The electrical insulation of high voltage rotating
machines is one of the most important parts of
generators und motors with respect to the
manufacturing costs as well as to maintenance
and life time aspects. Defects in the stator
insulating system may be created by combined
thermal, mechanical, electrical and
environmental stresses during operation,
resulting in gradual deterioration [4]. It is of great
importance, that the aging condition of the
insulation can be evaluated based on nondestructive
characteristic parameters.
Today, the estimation of the aging state of
the insulating system and remaining
lifetime of a machine is based
on experience and empirical laws found by
extensive testing and dielectric measurements on
machines and on model insulators [5].