Cast Resin Dry-Type Transformers

SGB’s cast resin dry-type transformers are designed and manufactured as standard in accordance with IEC 60076-11. It includes power ratings up to 25MVA and rated insulation voltages up to 36kV, as well as converter and special transformers.

The low ignition hazard and self-extinguishing character, to verify fire protection class F1, is proved by testing that complies with the European body of regulations and standards (IEC).

• Routine and type testing are done according to international standards.
• Routine and type testing are done in SGB’s own modern test area.
• First transformer manufacturer with internal C2/C3 test area to verify climate class.
• First transformer manufacturer with internal E2/E3 test area to verify an environmental class.
• Verification of internal tests by German agency TÜV-Süd / other renowned institutes.
• Operation of cast resin transformers possible in temperatures down to -50°C.

SGB’s cast resin dry-type transformers are insulated with a mixture of epoxy resin and quartz powder (an environmentally friendly material) that allows the winding to be:

• Almost maintenance-free.
• Flame-retardant.
• Self-extinguishing.
• Moisture-resistant.
• Tropicalized.

No toxic gases are produced – not even under the effects of arcing. The unique developed spacers of the coil support system ensure isolation of vibrations from the iron core, which result in very low noise levels.

Only SGB’s dry-type transformers feature vacuum-encapsulated high voltage coils, of which the winding is designed as a double-layered winding.

Why double-layered winding?
For over 40 years, SGB has manufactured coil winding for distribution (oil) transformers and cast resin transformers. Their established experience is the reason for the following particularities which ensure the highest quality:

• Two established processes to connect the end lead bars to the coils exist: (1) Inert gas welding, OR (2) Cold pressure welding under high pressure (400 kN). For over 20 years, SGB has only used cold pressure welding. As a result of this process, there is no metallurgical change to the conductor metal by means of a thermal process, and no foreign matter occurrence.
• By using multi-layer prepregs with subsequent bonding, a highly resistant cylinder is created. Unlike other conventional solutions, this cylinder is capable of absorbing the radial short-circuit forces in a self-supporting fashion. The simple support to the core is used only for centering.

 

• The winding edges are stiffened additionally. This affords reliable protection against the penetration of humidity and enhances mechanical resistance. This technology has proven its worth over many decades, including in terms of extreme applications, and is equivalent to encapsulated winding.

The high voltage windings are potted with epoxy resin under vacuum at a high temperature, to ensure that:
 
+ Undesirable gas inclusions are prevented.
+ Freedom from partial discharges (up to twice the rated voltage) is provided.
 
The low-voltage strip winding is also made of copper or aluminum. The width of the strip is equal to the length of the coil, to ensure that:
 
+ Axial short-circuit forces in the transformer are reduced.

SGB’s cast resin dry-type transformers have ongoing benefits – even at the end of their life-cycle:
+ Without any danger to the environment, up to 90% of the material can be recycled.