This guide establishes minimum requirements and practices for the physical security of electric power substations. It is designed to address a number of threats, including unauthorized access to substation facilities, theft of material, and vandalism. It describes the requirements for positive access control, monitoring of facilities, and delay/deter features which shall be employed to mitigate these threats. This guide also establishes requirements for different levels of physical security for electric powersubstations. The guide does not establish requirements based on voltage levels, size or any depiction of criticality of the substation. The user will make these decisions based on threat assessment and criticality assignment by the substation owner. Overtattacks against the substation for the purpose of destroying its capability to operate, such as explosives, projectiles, vehicles, etc. are beyond the scope of this guide.