NASA - UFGS-26 11 16
SECONDARY UNIT SUBSTATIONS
|Publication Date:||1 February 2010|
1. This guide specification covers the requirements for three phase secondary unit substations for step-down operation at primary voltages of 601 volts through 38 kilovolts, and secondary voltages, of 600 volts or less.
2. When feasible, provide a separate liquid-filled pad-mounted transformer outside of the facility and a separately erected switchboard/switchge
3. For NAVFAC LANT projects, where the available fault current is less than 12,000 amperes rms symmetrical, provide pad-mounted switchgear with a fault interrupting switch-way as the transformer primary protection device in lieu of a load interrupting switch. Clearly indicate requirements for identifying signage at switch-ways and at the transformer.