Cut the Copper
The New Age of Ventilated Dry-Type Transformers
In this "Cut the Copper" blog, manufacturers use air as a transformer coolant after their attempts to replace Askarel fluids met with little to no success.
After enduring all of the pain and tremendous costs associated with replacing, rehabilitating, retro-filling and remediating nasty liquid-filled transformers, the electrical industry finally said, more or less in unison, “That’s enough! I’m not going to go through this anguish one more time! No more liquid transformers in my plants ever again. The EPA will never outlaw AIR as a transformer coolant, so from now on, my indoor transformers will be air-cooled.”
Manufacturers like GE and Westinghouse, again, led the charge and developed new dry-type substation transformer designs. The electrical industry adopted these quickly, and dozens of other smaller manufacturers entered the transformer business with new ventilated dry-type transformer designs.
In general, the new dry-types worked well in service, although early adopters immediately complained about how loudly they operated compared to the liquid units they replaced, and how much heat they generated when loaded. The most prevalent early designs used 220 C winding insulation and an allowable winding temperature rise of 150 C over a 40 C ambient. That says that the windings themselves could be operating in completely normal service at temperatures nearly twice the boiling point of water, so it’s no wonder that they felt “warm” (can you spell “i2R winding losses”?)
Later, next generation improvements included things like Vacuum-Pressure Impregnation (VPI) process, that greatly improved uniform quality of the insulation systems, and then lower temperature rise construction (115 C and 80 C ratings), that greatly improved efficiency and also extended useful operating life.
In general, life was good, again, with many tens of thousands of dry-type transformer installations now in service.
Helping Joe on these blogs posts is Brian Steinbrecher, an electrical engineer focused on medium-voltage power distribution systems. His 30 year career includes work with an end-user (IOU), a manufacturer of power systems equipment, and as a system designer/consultant. Brian has a wide breadth of experience within the utility segment from systems design to equipment specifications and from system studies to construction and start-up. He has written many technical documents, papers, and reports and holds over a dozen active patents.
A good portion of Brian’s career was with Cooper Power Systems where he performed engineering and marketing work in behalf of their major product groups. Prior to moving into his current role, Brian was the Director of Engineering for a product group at Cooper. Brian is currently the Owner and Principal Engineer at Galt Engineering Solutions located in Brookfield, Wis.
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Wednesday, 02-05-12 13:43
SGB Cast Resin dry-type transformers have a MTBF (Mean Time Between Failure) of 2,400 years. With that kind of reliability there are significant savings in maintenance, TOS (Time Out of Service), and TOC (Total Ownership Cost). Our units are also inherently safe; unable to sustain combustion without external energy.
Dry-type are important only if you care about safety, up time, & operations cost. If your facility matters, take a look at dry-types.