Fire-Resistant Cast-Resin Transformers Offer Multiple Safety Benefits

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In previous posts, I described the lifecycle-cost and environmental benefits the cast-resin transformers provides, compared to liquid-type transformers. In this post, I describe the fire-resistance cast-resin offerings provide, especially when indoor installation is required. While their first costs can be higher, but often are competitive globally by taking into account all expenses of installation and other, cast-resin transformers are both less expensive and safer to operate than those using oil as an insulating material.

Cost and environmental benefits

As I described in “Thinking Beyond First Costs When Specifying Transformers,” cast-resin units – also called “dry-type” transformers – require much less ongoing maintenance than oil-filled transformers. And, as I covered in “Today’s Medium-Voltage Transformers Are Turning Green,” new CENELEC standards EN 50588 and EN 50629 are leading to more efficient transformers, across the board. But safety, especially electrical fire safety, remains a critical consideration when specifying medium- and high-voltage transformers, and cast-resin designs offer some distinct advantages, in this regard.

Material advantages

The most obvious safety feature of cast-resin transformers is the use of epoxy resin instead of oil. For example, Schneider Electric’s Trihal dry-type transformers incorporate alumina trihydrate into the resin formula, which reduces fire risks in three ways. If a unit is exposed to flames, the material:

  • Creates a refracting shield of alumina
  • Produces a barrier of water vapor
  • Holds surface temperature below the point of ignition

As a result of these three qualities, dry-type transformers are actually self-extinguishing. With a net calorific value of less than 10 megajoules/kilogram (MJ/kg), compared to 30 MJ/kg or more for the oil used to insulate liquid-type transformers, cast-resin units can be installed indoors, without special fire precautions. To establish the F1 fire classifications required for indoor installation, transformers are tested to IEC Standard IEC 60076-11.

In addition to resisting flames, cast-resin transformers also produce less toxic smoke than oil-insulated versions. This means firefighters are able to more safely access areas around a transformer should a blaze occur nearby.

Learn more

Check out the recent white paper “How to Specify Cast Resin Transformers for Commercial and Industrial Buildings” for more information on the advantages these products could offer for your next project. And you can also visit our Consulting Engineer Portal for more resources and to connect with our engineering specialists.

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