Revision Standard - Active. Guidance for the physical security of electric power substations is provided in this guide. It addresses a number of threats, including unauthorized access to substation facilities, theft of material, and vandalism. It describes some options for positive access control, monitoring of facilities, and delay/deter features that could be employed to mitigate these threats. This guide also discusses options for different levels of physical security risk for electric power substations. The guide does not establish recommendations 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. Large scale overt attacks 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.