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Description / Abstract:
This guide briefly describes aging mechanisms of insulation
systems and methods for ascertaining correlation of aging during
testing and aging during actual service. Diagnostic techniques for
use in functional tests are also listed.
When the performance of an insulation system is evaluated by
accelerated functional tests, misleading results may be obtained if
the aging mechanisms under the conditions of the test differ from
those experienced in actual service applications. The risk of such
errors increases as the aging stresses are intensified in relation
to their normal levels in service.
The equivalence of the aging mechanisms in the test and in
service must be verified before an effective functional evaluation
test can be performed. The importance of such verification
procedures increases with the degree of stress intensification.
considerations regarding the methodology of verification are given
in Section 3.
Diagnostic methods, which are especially sensitive in
ascertaining changes in the test specimen's condition, may have the
advantage that tests at relatively less intensified stresses can be
included to determine the changes of the system's characteristics
or aging rate. Diagnostic methods are reviewed in Section 4.
It must be recognized that functional test procedures may
require the selection of an arbitrary end-point criterion that does
not correspond to equipment failure. This end-point, however,
provides a relative measure of life expectancy.
Purpose
The purpose of this guide is to present background information
necessary for proper construction of aging mechanisms and selection
of diagnostic procedures when designing tests for functional
evaluation of insulation systems for electrical equipment.
This guide is primarily intended to aid committees to
standardize tests within their scope of responsibilities.