DRY TYPE TRANSFOMER FACTOR THAT AFFECT ITS LIFE BASIC
INFORMATION
What Are The Factors That Affects The Life OF Dry Type
Transformers?
Dry-type transformers may be loaded above rated kilovolt-amperes
under conditions other than those specified in the preceding clauses, with a
sacrifice of life expectancy dependent on the load capability of the
transformer and on the actual operating conditions.
The overload capability of dry-type transformers varies
widely and is affected by the following characteristics:
a) Hottest-spot winding conductor rise over ambient;
b) Ratio of load losses to no-load losses;
c) Time constant;
d) Ambient temperature.
Operating conditions for dry-type transformers are so
variable that no single set of practical loading data can be presented for all
possible combinations of conditions and loading.
However, methods are outlined in this clause whereby the
user can estimate allowable loads for the user’s own conditions by taking into
account the probable number and nature of such loads during the life of the
transformer, and the approximate percentage of life expectancy that the user is
willing to sacrifice.
In general, permissible temperatures and loads calculated by
the means outlined here will be higher than those loading for life expectancy
which are necessarily conservative in order to cover the wide variation in
sizes and makes of dry-type transformers.
The necessary curves, tables, equations, and definitions used
as a basis for the methods given here are presented in Clause 6 of IEEE
STD-C57.56. Information given is considered to be the best that can be produced
from the present knowledge of the subject.
In spite of its approximate nature, it is believed that it
will be of value as a guide to the user.
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