This document examines the vulnerability of electrical power systems to natural hazards, describes what equipment in critical facilities should be supplied by emergency power sources, how long the emergency power may be needed, the specific equipment needs of different types of critical facilities, and how emergency power can be supplied. It provides guidance on how to assess the risks and vulnerabilities to the electrical power system, identifying performance goals for an emergency power system, and the importance of having realistic emergency management policies that address emergency power.
It also discusses the advantages and limitations of redundant systems, the need for advanced planning of emergency power systems, potential pitfalls when sizing system components, such as fuel storage tanks, and provides examples of simple and complex installations. It emphasizes the need to apply a holistic approach to the design of a new emergency power system. In this document, a holistic approach means all elements of the design and operation of the emergency power system and the equipment using the power need to be considered, so that the facility will perform as intended under extreme design events, all in a cost effective manner. The report also provides summaries of relevant building code provisions that influence the design of emergency power systems.