This paper describes a new estimating method of elec^"_t~!.cal
insulation under given voltage stress. The new technique proposed
by the author can not only predict the lifetime under the service
voltage stress but also select the most adequate V-t characteristics
model objectively. This paper has the four outstanding features
as follows. (1) Two V-t characteristic models have been proposed:
one is the so-called inverse power law model and the other is
the exponential model. The former has a relation with the Weibull
distribution, but the latter not. Thus, the author proposed a
new exponential model with the Weibull probability distribution.
(2) Both two models include the threshold voltage stress parameter
in the probability distribution. Thus, we can estimate the threshold
value with confidence interval. (3) In order to cut down on time
of V-t test, an accelerated stress procedure with type I censoring
is considered. (4) We can determine which modcl represents better
the V-t test data in the meaning of the most adequate V-t characteristics.
In model selection, we use the AIC(Akaike Information Criterion).
The idea of AIC will give us deeper knowledge for the voltage
deterioration phenomena. Therefore, we can select the probable
model, and we can estimate the unknown parameters of the selected
model such as the threshold value and the lifetime under the service
voltage with confidence interval.

The paper written in English is available
upon request.