Water Curtain for Transformers
Among the interesting and unusual pieces of machinery at Boulder Dam are the transformers, which step up the 16.5 kv. primary voltage to 287 k.v. for transmission over hundreds of miles of cable. Physically, these units are the largest in the world, and operate at the highest voltage ever used commercially. Each one is 32 feet in height, and weighs 385,000 pounds, 150,000 pounds of which is accounted for by the transformer oil which they contain.
In design they are of the circular-coil, non-resonating type, and a shielded high voltage winding is used. A water curtain for fire protection has been provided. These units were built by General Electric Company especially for installation at Boulder Dam, and constitute examples of the pioneering work that has been necessary in this field.
Lightning arrestors for the switching stations and switchyards present an unusual appearance. The central columns are composed of 287 kv Thyrite arrestors, supported further by three strings of insulators around the outside. The bottom of the assembly is secured to the base through a spring attachment that serves to prevent swaying. Electrostatic stresses are distributed over the entire length of the arrestors by means of circuit shields which present the appearance of lamp shade frames.