URJA is one of the leading and established cast resin dry type transformer (CRT) manufacturer, supplier and exporter. Cast resin transformers (CRT) are air cooled dry type 3 phase distribution transformers used in high moisture prone areas.
We manufacture CRT complying to IEC 60076-11, IS 11171, BS, CE standards.
We manufacture cast resin dry type transformers up to 3.5 MVA and 33 kV Class.
Cast resin dry type transformers are used for indoor as well as outdoor applications. The primary and secondary windings in these transformers are completely encapsulated by epoxy resin of Class F. This prevents penetration of moisture and increases life of winding. Also the encapsulation offers very good protection against adverse ambient conditions. These transformers can work 100% humidity without disruption of service.
These transformers are provided with standard enclosures complying with IP55 rating.
Epoxy resin is used as insulation material. Normally we use epoxy resin of classes F and H depending on the customer requirements. The high grade insulation material makes the coils non hygroscopic which eliminates the need of pre-drying the coil before starting even when the transformer has not been in use for a long period of time.
Cast resin coil transformers are better in respect of impulse voltage withstand strength.
Due to fibre glass reinforced epoxy encapsulation higher dynamic short circuit withstanding strength is observed in comparison to oil immersed and conventional dry type transformers. During this operation no partial discharges occur.
The insulation material used is usually glass fibre, mica, silicone elastomer, asbestos, etc. reinforced with epoxy bonding resin of class 'F' and class ‘H’. Class H polyester resin can withstand hot spot temperature rise upto 180 Degrees Celsius and maximum winding temperature upto 220 Degrees Celcius, Class F resin can withstand hot spot temperature rise of 145 Degrees Celcius and maximum winding temperature upto 180 Degrees Celcius. Class F insulating material is commonly used.
Due to high hot spot temperature limit and maximum winding temperature limit the transformer is practically non-inflammable by an electric arc and hence special fire protection measures are not required.
Since in CRT the moulds get hardened on drying hence no coil tightening is required. Also it eliminates the need of insulation oil level and condition checking. This leads to saving in maintenance cost related to oil. Moreover as cast resin transformers are solidly cast, the problems associated with oil immersed transformers such as oil pilferage and oil leakage are completely avoided.
In terms of size and weight, CRT are smaller in dimension and lighter in weight as compared to oil immersed transformers. They also occupy less space. As the epoxy resin has high level of temperature sustaining limits they can be placed near the load centre as it reduces the possibility of fire or danger of explosion.
The overall civil works for CRT is reduced since they do not require construction of any special fibre brick walls or oil pits.Also LT cables are not required, which leads to savings in cost usually incurred in laying of cables.
Cast resin dry type transformers are environmentally friendly as it there is no contamination of ground water due to zero oil leakage.
Application of Cast Resin Dry Type Transformer:
These transformers are used in distribution network for feeding basements or stilts of high-rise buildings,air ports, stadium, hotels, shopping malls, chemical & refinery plants.