  This paper is an effort to evaluate the numerical indices for the assessment
of the frequency response analysis (FRA) to provide a deeper understanding of
their characteristics. The study introduces the indices in the literature and
categorizes them into two groups. The results of an actual FRA experimental
setup on an electrical machine are employed to examine the indices from the
various aspects. The main features of the indices are extracted, and the better
ones in various aspects are marked. Moreover, based on the observations from
the experimental studies, a new numerical index for comparing FRA results is
proposed in this paper to enhance FRA results assessment and interpretation in
both electrical machines and transformers. The advantages of the proposed index
are also shown by comparing it with the existing ones.
