What Are the Transformer Enclosure / Housing Types?

Published 27 Aug 2026Updated 27 Aug 20265 min readIntermediateApplications
Quick answer — Transformers are made for indoor and outdoor service: an outdoor unit is weatherproof with IP-rated bushings and a sealed tank; an indoor unit may be in a metal or enclosed housing, or a pad-mounted/unit-substation enclosure. The enclosure (IP rating, material, ventilation, fire rating, access) is chosen for the site and the environment, and for indoor fire-safety and noise.
Contents
What are the different transformer enclosure types?

Outdoor vs indoor

Outdoor units have weatherproof bushings, a sealed tank and a high IP rating; indoor units may be in a ventilated enclosure or a room, with extra attention to fire and ventilation.

Enclosure types

Pad-mounted, unit-substation, or a simple metal housing; the enclosure provides the IP rating, fire rating, ventilation and access for the site.

Choosing

Match the IP rating, the material (steel, GRP), the cooling and the fire and noise requirements to the location, indoor or outdoor.

References & standards

Related

Book seriesAcademy

Related manufacturers

Prolec GE (GE Vernova) · Prolec GE Waukesha · Hitachi Energy USA · Siemens Energy · Eaton · Virginia Transformer Corp

Related components

Tank & mechanical Transformer bushings & terminations
Technical content is prepared from engineering references, standards frameworks, manufacturer documentation and industry sources. Contractual or compliance decisions should refer to current official standards. TransformerPath Technical Editorial.
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