Facilities Instructions, Standards, and Techniques Volume 3-32: Transformer Fire Protection [open pdf - 299KB]
From the abstract: "Large, oil-filled transformers pose the risk of explosion and fire should the transformer fail and the insulating oil ignite. Fire suppression systems have been used at Reclamation plants for many years, but there have been inconsistencies in applications of these systems and in their operation and maintenance procedures. This volume establishes consistent practices for use across the organization and provides technical background and references, as well."
Bureau of Reclamation, Facilities Instructions, Standards, and Techniques Volume 3-32
United States Bureau of Reclamation: http://www.usbr.gov/