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What types of transformers should be used to step down voltage from 400kv to 132 kv, 132kv to 33kv,33kv to11kv?

what are the pro's and cons of using cast resin and oil cooled transformers?

Public Comments

1. No question about it Oil Filled transformers are always far better in sub station voltages like that. Dry type are used for industrial/commerical loads of 120/208 volts off the incoming 480 volt. Oil filled were used alot back in the day. They have been phased out because of PCB's (Polychlorinated Bythenals) very toxic if it gets into the water supply. Dry type tend to break down quicker because of the heat.The windings have also gotten cheaper constructed over the years. Disc Wound were the best (using all cooper), Barrel Wound were not near as good but worked fine for what it did. And Core Wound what is used now a days, Aluminum windings around iron cores then coated in laminate resin, they work thats about it. Nothing comes close to good ole PCB's. for cooling.


2. I don't know what sparky is rambling on about but he certainly doesn't respond to your question.

   Anyhow, for 400 to 132kV interbus transformers the best option is normally a 3 phase autotransformer with forced oil and forced air cooling. This is dictated by economics. For very high ratings 3 single phase autotransformers in separate tanks might find application. This would be dictated by manufacturing and/or transport problems.

   For the other applications normal oil cooled 3 phase power system transformers having separate primary and secondary windings would usually be chosen. Those for 132 to 32 kV would again have forced cooling but the 33 to 11 kV might use natural circulation cooling - depending on local ambient temperatures and cost considerations.

   Cast resin doesn't come into it here unless the unit rating (e.g. as for a station service or auxiliary transformer) were quite low but even then the HV side is normally not so high as 33kV, maybe max. about half that.



3. These would almost all be oil filled. There is an option for SF6 filled, but that would be very unusual (and expensive).

   Cast resin transformers are typically found only in lower voltage applications - say 13.8 kv stepping down to 480v.



4. Usually,oil cooled power transformers, 3-phase 400kv/132kv, 132kv/33kv ,33kv/11kv transformers are used.

   Cast resin transformers may not have adequate cooling and THEY MAY OVERHEAT IN TIME

   Oil cooled transformers may cool down transformers adequately, but they will require regular filtering and possible replacement.