Cast Resin Dry Type Transformer
|In cast-resin dry-type
transformers, the complete encapsulation of primary and
secondary winding in epoxy resin prevents penetration of
moisture into windings. The cast resin offers very good
protection against adverse ambient conditions. These
transformers can work without disruption of service at 100%
Due to the high grade insulation material, coils are non
hygroscopes & the transformer can be switched on directly
without pre-drying even after a long period of service
Contrary to the conventional dry type transformers the
cast coil transformers are better in respect of impulse
voltage withstand strength.
Higher dynamic short circuit withstands strength as
compared to oil immersed and conventional dry type
transformers because of fibre glass reinforced epoxy
encapsulation. No partial discharges can occur during
operation. The insulation material used is glass fibre
reinforced with epoxy resin of class 'F' which can withstand
wide temperature variation. Due to high quality insulation
material the transformer is practically non-inflammable by
an electrical arc, special fire protection measures are not
Due to encapsulation of coils with cast resin the coils
dimensions are stable & no coil tightening is required to
maintain the short circuit strength. Also no check of oil
level and electrical insulation/oil is required. This leads
to saving in cost on account of maintenance.
As cast resin transformers are solidly cast, problem
associated with oil filled transformers like oil leakage and
pilferage of oil is completely avoided.
These transformers are generally smaller in dimensions and
lesser in weights. The construction and installation cost
for the sub-station can be reduced by adopting dry type
Without fire or danger of explosion, it is possible to
place the transformers near to the load centre. Also, these
transformers do not need construction of special fibre brick
walls or oil pits, which reduces the overall civil works.
Additionally, since LT cables are not required, thers is
also saving in cost on account of expensive cable laying
Since no oil is used in these transformers, there are no
chances of contamination of ground water due to oil leakage.