A 100,000-volt portable substation

Expanding needs of the Southern Power system, paralleled many miles by railroads, required a flexible-connection transformer relay of large capacity, easily portable, and self-contained on a single car. The equipment in operation is of 4000 kv-a. actual capacity, and provided with high- and low-tension switch gear, instruments, panel, wiring and cables, oil-insulated, self-cooled transformers with motor-driven blower for forced air draft, special means of establishing the high-tension delta with 100,000-volt clearances, after transformer terminals and high-tension switches have been raised by a portable derrick, from receptacles where all fragile parts are protected from malicious tampering. Besides meeting standard freight car requirements for transportation, substantial, specially braced trussed superstructure is provided for supporting cabs and switch gear, which latter, as well as transformer terminals, must be lowered, during transit, to meet railroad clearances. Unusual flexibility of voltage connections is secured, contributing largely to the successful operation. Current for lights, instruments and blower motor is obtained from auxiliary transformer windings incorporated with the main units. Low-tension arrangements allow operation at various voltages with minimum switching. The entire equipment is designed for simplicity and dispatch in disassembly for transit, and reassembly in new location.