C. Dang et al., ELECTRICAL AGING OF EXTRUDED DIELECTRIC CABLES - REVIEW OF EXISTING THEORIES AND DATA, IEEE transactions on dielectrics and electrical insulation, 3(2), 1996, pp. 237-247
Despite the huge amount of data on so-called electrical aging of extru
ded HV cables, the fundamental phenomena responsible for it or evolvin
g with aging time, are still far from well understood. It is therefore
not surprising why it is so difficult to predict reliable cable lifet
imes in service from accelerated aging experiments in the laboratory.
The objective of this paper is to review critically the existing theor
ies of electrical aging of solid dielectric materials. A relatively la
rge number of models and theories exist but none of the most often use
d is known to yield reliable life predictions. One conclusion is that
there is a need for a more comprehensive model of electrical aging of
extruded dielectric cables. In order to develop this model, an extensi
ve review of existing literature data was undertaken. This paper summa
rizes the data collected from more than 200 papers on aging of PE, XLP
E and EPR cables. It appears that cable breakdown strength should not
be plotted on log field vs. log time graphs to yield long-time (i.e. l
ow-field) values, since results obtained over a long time period do no
t obey an inverse power law. In fact, high-field results are better de
scribed by an exponential relation between time and field. The models
of Simoni, Montanari and Crine seem to give the best fit to experiment
al results obtained under a wide variety of experimental conditions. I
t is also shown that the lower field limit for the exponential regime
with XLPE cable is in the 8 to 15 kV/mm range, which corresponds to th
e onset of strong charge injection. The influence of environment, insu
lation nature and morphology, and testing temperature are discussed. I
t is also shown that the two physical parameters of the model describe
d in Part 2 are linearly related and vary with the experimental condit
ions.