Grid Glossary

TRENDING TERM

Critical Issue Fast Path (CIFP)

An accelerated stakeholder process used in PJM Interconnection to resolve urgent, contentious, and time-sensitive issues that cannot be resolved through the normal stakeholder process. The process involves several stages of discussion and proposal development, culminating in a submission to the Federal Energy Regulatory Commission (FERC) for approval. The CIFP process has been used in recent years to discuss large load additions (2025) and resource adequacy (2023).

TRENDING TERM

Effective Load Carrying Capability (ELCC)

Measurement used to calculate how much an energy resource–such as a wind farm or solar array–contributes to the overall reliability of the grid. It assesses the resource’s ability to meet electricity demand, particularly during peak usage periods, and is especially useful for variable renewable energy sources whose output depends on factors like weather conditions. 

TRENDING TERM

Disturbance

Refers to any unwanted or unplanned electrical event that interferes with the normal operation of the electrical grid. These can manifest in power outages, surges, and other events, and can originate from various sources within the electrical grid, such as loss of a large generating unit or another grid asset, such as a transmission line or transformer.

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Baseload

The minimum amount of electricity that a utility must provide to meet the consistent, ongoing needs of its customers. Historically, this steady demand was met by large power plants (like coal or nuclear) that ran continuously. Today, with more renewable energy, this minimum demand can be met by a flexible mix of various power sources, rather than relying solely on specific “baseload plants”.

  • Baseload capacity:  The generating equipment normally operated to serve loads on an around-the-clock basis.
  • Baseload plant:  A plant, usually housing high-efficiency steam-electric units, which produces electricity at an essentially constant rate and runs continuously. 
Battery Energy Storage System (BESS)

A technology that stores electrical energy in rechargeable batteries for later use. Batteries help stabilize the grid, manage energy demand, and increase the use of renewable energy.

Behind-the-meter

Any energy resource that provides energy directly to a home or business without passing through a utility company’s meter. Examples include rooftop solar and microgrids.

Federal Energy Regulatory Commission (FERC)

An independent agency that regulates the interstate transmission of natural gas, oil, and electricity. FERC also regulates natural gas and hydropower projects.

Federal Power Act

A United States law primarily regulating the interstate transmission and sale of electricity and the development of hydroelectric power. It was responsible for creating the body now known as FERC. It was created in 1920 and has been amended several times since. 

Firming requirements

Measures taken to ensure backup power, particularly of renewable energy, such as solar and wind generators. These requirements may require battery storage, ancillary services, or backup generation, such as an added gas plant to produce energy when a solar or wind plant does not.

Frequency

Electricity is supplied to homes and businesses in the United States in the form of alternating current, and frequency is the rate at which an alternating current changes direction, as measured in hertz (Hz). Across the power grid there is a consistent frequency which in the United States is 60 Hz. 

Frequency regulation or response

The ability of the grid to react to a change in

the frequency to bring it back to the normal operating frequency, which is 60 Hz in the United States

  • Inertial response refers to the injection of stored energy, such as battery energy, into the electricity grid to slow down a decline in frequency. 
  • Primary frequency response – The first line of defense against frequency fluctuations that could destabilize the grid. It takes the form of immediate, automatic adjustments in power output by generators and loads in response to frequency deviations in the electric grid.
  • Fast frequency response consists of the combined inertial response and primary frequency response. It injects energy in the seconds immediately following a disturbance to slow frequency decline and establishes the minimum frequency (called the nadir).
  • Secondary frequency response works on a slightly longer time frame than primary frequency response, on the order of 5-15 minutes. It maintains grid frequency and allows for scheduled energy transfers between balancing authorities, which include utilities, regional transmission operators, and other grid management entities.
Large load

Historically refers to industrial facilities with high electrical demand. They had long interconnection timelines that allowed for more study time under traditional planning processes. Currently, emerging large loads include cryptocurrency mining, data centers (conventional and artificial intelligence), oil field loads, and hydrogen production facilities. Many have a shorter timeline to interconnect (months vs. years) to the grid. In addition to these rapid timelines, some emerging large loads introduce new challenges to grid operators like rapid demand fluctuations and increased voltage sensitivity.

Load

The amount of power or electricity consumed by a device or system at a given time. It’s the demand placed on an energy source, like a power grid or a battery, by the connected electrical equipment.

Load growth

The increase in the demand for electricity over time. It signifies the rising need for power from various sectors, including residential, commercial, and industrial, and can be driven by factors like population increases, economic development, and the adoption of new technologies like electric vehicles and data centers.

Load shed

A controlled process where a utility company reduces or shuts off power supply to certain areas or customers to balance demand with available supply, preventing a complete system failure. It’s a last-resort measure to maintain grid stability when demand exceeds supply or when there are issues with power generation or transmission.

Locational Marginal Price (LMP)

A way for wholesale electric energy prices to reflect the value of electric energy at different locations, accounting for the patterns of load, generation, and the physical limits of the transmission system.

Loss of Load Expectation (LOLE)

Analysis is typically performed on a system to determine the amount of capacity that needs to be installed to meet the desired reliability target, commonly expressed as an expected value, or LOLE of 0.1 days/year.

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