Where should dry-type transformers rated over 35kV be installed when indoors?

Dry-type transformers rated over 35kV are classified as high-voltage equipment, which necessitates specific installation considerations to ensure safety and compliance with building codes. The requirement for such transformers to be installed in a vault stems from the need to contain any potential electrical faults, manage heat dissipation, and protect personnel and property from high voltage hazards.

A vault provides a controlled environment specifically designed for high voltage equipment, including appropriate ventilation, fire-resistant barriers, and other safety features that mitigate risks associated with high voltage operation. This isolated setting reduces the likelihood of electrical hazards impacting building occupants and allows for secure maintenance access.

While options like being in an open area or on a roof might seem practical, they do not offer the necessary protections and control required for high-voltage installations. A separate room could provide some containment, but it likely lacks the robust features that a designated vault would have. Therefore, installing these transformers in a vault is the most effective and compliant option for ensuring safety and reliability in indoor settings.