Transmission lines are often very long and in sparsely populated areas. They make easy targets and cannot be well protected. However, they can also be repaired quickly unless there is a coordinated widespread attack. Even then, the transmission lines can be repaired almost as soon as replacement towers can be delivered. Thus transmission lines are of less concern than substations.
System Control Center(s)
Major electrical systems rely heavily on their primary system control center. Computers, telemetry, fiber, radio, and dedicated telephone lines are continuously used to monitor major system elements and transmit vital information to the control center. As discussed in Chapter 6, when routine disturbances occur, the system is designed to take certain remedial measures instantly and to automatically report these measures and conditions to the control center staff. Major disturbances often require quick decisions and reactions on the part of the staff to prevent widespread outages.
System control centers contain highly technical control and communications equipment as well as experienced system operations personnel. Any attack, such as with a vehicle bomb that would destroy or severely damage such a center, would also significantly impair the operation or restoration of a system by eliminating vital command, control, and communications (C3) functions and capabilities. In most cases there are redundant control facilities, and the system could still be operated, but C3 would be significantly degraded.
Security is very uneven across the system. Some control centers have been extensively hardened and have excellent access control and other security. Other utilities provide nominal local security for these centers that could easily be overcome by a determined attacker. Control centers could easily be sabotaged by insiders either to affect C3 loss or to support a broader system attack by outsiders.
Control centers could be a desirable terrorist target, particularly if the redundant center is also targeted. Loss of a control center would make the continued operation of the power system difficult and might cause widespread outages.
From the transmission substation networked medium-voltage lines and substations carry the power to all the users “downstream” from the transmission system. Distribution components are more numerous and of lower capacity than transmission system components, and spare parts are generally in greater supply. Storms take an annual toll on distribution systems. Utilities are prepared for such emergencies and often pool their resources to aid each other in restoring service. Targeting of distribution system components can cause troublesome outages, but the magnitude of the problems will usually be more manageable than those resulting from attacks on the “upstream” transmission systems or generation stations, unless of course they are targeted at disrupting supply to a critical facility in conjunction with some other attack.
Other Collective Targets
Other targets, although not system choke points, can be key terrorist targets. These include:
• Key personnel. Hostage taking usually places the attacker at greater risk than does the mere destruction of facilities or equipment. However, it should not be overlooked by security planners as a tactic historically employed when coercive control is desired. Contingency plans, security awareness training, and timely threat briefings for key personnel have proven effective in these situations.
• Major materiel yards. Central supply points, and sites where major repair vehicles and high-voltage spare components are stored, present valuable targets. Although such sites have a lower priority, security plans could include responses to the potential for attacks on these sites.
• Customers (Users). From heavy industries to households, the entire North American societal infrastructure is dependent in varying degrees on the reliable functioning of these electrical systems. As users’ demands fluctuate moment-by-moment, generation must be increased or decreased to keep all elements of the system and the demand in precise balance. Attacking individual consumer electrical facilities would have limited overall impact on society, unless those facilities constituted part of a coordinated attack on targets such as chemical facilities or facilities providing essential community services.
Countermeasures to attacks on physical infrastructure such as substations include improved security engineering techniques, such as calculations of blast effects; the use of hardened construction; and calculation of minimum standoff ranges for threat weapons. Along with site hardening, new and improved surveillance equipment to allow rapid identification of and response to attacks could be installed at critical facilities. These improved electronic surveillance technologies include point vibration sensors, leaky coaxial cable sensors, seismic disturbance and electrostatic field disturbance sensors, microphonic cable, and microstain fiber option sensing systems (a new technology for perimeter protection) that could be employed as appropriate at sites depending on the level of threat and risk present.
dead-end tower (which is self-supporting even under one-sided tension) or a corner tower (which is used when the transmission line must make a turn, resulting in asymmetric loadings on the tower).