Adaptive Capacity

The ability of a system to successfully adjust to various external factors.

Adversarial actor

An individual, organization, or nation that acts maliciously with the intent to damage, disrupt, or destroy the power system or components of the system. Also referred to as bad actor or malicious actor.

Critical infrastructure

Assets, systems and networks that are essential for the functioning of society and the economy. Damage to this infrastructure, or disruption of the services they provide, may harm the security, economic activity, and/or public health and safety. Infrastructure may be physical or virtual, and publicly or privately owned, such as power systems, roadways, waterways, or other systems (e.g., buildings and water treatment facilities).

Critical loads

Loads for which power supply must always be maintained and cannot be interrupted to ensure the functioning of society and the economy, such as hospitals, critical communications, emergency services, water and wastewater treatment, and military installations.

Distribution network

The final system (structures, wires, insulators, and associated hardware) in the delivery of electric power to customers (load). Distribution systems consist of subtransmission-level voltage lines, typically below 69 kilovolts (kV).

Energy profile

Information on the energy consumption patterns and generation assets of the power system in addition to utility service provider agreements and long-term regional forecasts for meeting demands given socioeconomic projections.


The infrastructure, operations, workforce, and/or finance systems that are present where hazards may occur. Exposure is not a sufficient determinant of risk because systems may be exposed but not vulnerable.


Any abnormal flow of electric current in a power system that disrupts the steady state of the system. This may occur from, for example, a failure of system insulation materials or contact of the system with a conducting object, resulting in a short circuit. There are many possible causes, including, lightning, heavy winds, vehicles colliding with structures, squirrels shorting lines, lines breaking due to excessive loading, and others.

Flexibility (operational)

The ability of a power system to respond to changes in electricity demand and supply. High flexibility implies that a system can respond quickly to changes in net load.


Anything that can damage, destroy, or disrupt the power sector. This term is often used interchangeably with threat.

Human-caused threat

A threat that results from an accident (e.g., accidentally cutting underground lines) or an action from a bad actor (e.g., cyber, acts of terror). Refer to the definition of threat.


The extent to which a hazard affects power sector infrastructure and processes (e.g., a typhoon causes wind damage to transmission lines). This term is often used interchangeably with consequence or outcome.


This term refers to the physical and virtual structures, facilities, and systems of a power system. It includes generation, transmission and distribution, and transportation systems in addition to the assets that support these systems.


Integrated Resource and Resilience Planning (IRRP) is a strategic energy planning approach that enables power providers to identify a “least-regrets” power resource investment portfolio or one that is most resilient to potential future risks.


This term refers to end-use devices or customers that receive power from the electric system. It also refers to the aggregate electric power consumed by all users connected to the power system.

Natural threats

Threats that result from acts of nature (e.g., severe weather, floods, earthquakes, hurricanes, solar flares, and others) as well as wildlife interactions with the power system (e.g., squirrels, snakes, or birds causing short circuits on distribution lines). Refer to the definition of threat.

Planning horizon

The length of time into the future (start and end year) that is considered for a particular planning activity. For example, a planning horizon of 15 years, starting in the year 2015, would go until the year 2030.

Power sector resilience

The ability to anticipate, prepare for, and adapt to changing conditions and withstand, respond to, and recover rapidly from disruptions to the power sector through adaptable and holistic planning and technical solutions.


The inclusion of additional resources beyond those that are required for daily operation and which can be relied upon to continue system operations in case of failure of other components.


A measure of whether a power system can provide regular, consistent power, typically defined by System Average Interruption Duration Index (SAIDI), Customer Average Interruption Duration Index (CAIDI), and System Average Interruption Frequency Index (SAIFI).


See Power sector resilience


The potential for loss, damage, and/or destruction of power system assets or other key resources resulting from exposure to a threat. Risk is evaluated as the product of the threat likelihood and vulnerability severity scores.

Spatial diversification

The practice of separating power system infrastructure over different geographical areas to avoid exposure to threats. The modular nature of renewable energy technologies, such as wind turbines and photovoltaics, permits spatial diversification.


A pressure or tension that is exerted on the power system that could have adverse effects on continued operations (e.g., changes in population or economic conditions in a region).

Technological threats

Unpredicted equipment and infrastructure failures (e.g., a bridge collapse or grid outage). Refer to the definition of threat.


Anything that can damage, destroy, or disrupt the power sector. Threats can be natural, human caused, or technological. Threats are not typically within the control of power system planners and operators. They may consist of wildfires, hurricanes, storm surges, cyberattacks, and others. This term is often used interchangeably with hazard.

Transmission network

A system of structures, wires, insulators, and associated hardware that carry electric energy from one point to another in an electric power system. The system is operated at high voltages (above 69 kV) and can transmit large quantities of electricity over long distances.


A situation in which the current state of knowledge involves imperfect or unknown information; the consequences, extent, or magnitude of conditions or events is unpredictable; or the credible probabilities of possible outcomes are not available.


Weaknesses within infrastructure, processes, or systems, or the degree of susceptibility to various threats. Different measures can be taken to reduce vulnerability or improve adaptive capacity to threats to the power sector. Vulnerabilities are typically identified through stakeholder interviews, technical analyses, and/or literature reviews.

Vulnerability assessment

A process that begins with data gathering, consideration of risks and exposure, and the identification of threats, impacts, and vulnerabilities in a power system followed by the prioritization of vulnerabilities according to risk.